CH714502A1 - Optical system for three-dimensional measurement, device and measurement method with such an optical system. - Google Patents

Abstract

An optical system (100) for three-dimensional measurement of the relative position between a first object and a second object upon which said optical system (100) is to be mounted, said optical system (100) comprising a first system camera (110) and a second camera (120), wherein: the depth of field of the first camera (110) is at least ten times greater than the depth of field of the second camera (120), and the optical system (100) is arranged such that the optical path of the first camera system (110) and the optical path of the second camera system (120) have a section common member comprising the image focal plane of the first image system (110) and the image focal plane of the second image system (120).

Description

Description

Technical Field [0001] The present invention relates to the field of optical measurement of the relative position between a first object and a second object.

[0002] More precisely, the present invention relates to a three-dimensional optical measurement of the relative position between a first object and a second object. This type of measurement is used in many fields applying dimensional metrology, including but not limited to the field of machining parts, in particular by machine tool or other machining by material removal.

In this area of the machine tool, there is a need to know precisely the relative position between the tool holder and the workpiece support, to ensure a machining range consistent with the machining plane developed during development.

The manufacture of parts by means of machining modules (machine tools), including lathe machines, automatic lathes, turning-milling centers, milling machines, machining centers and transfer machines, typically comprises three distinct phases: [0005] In a first phase of development (or preset), the operator (for example a bar turner) defines and tests on a machining module the machining plane, that is to say say the sequence of operations and axis movements necessary to obtain the desired workpiece. The operator ensures, for example, that the machining plan is as efficient as possible, that is to say, that which makes it possible to machine a given part with a minimum of operations and avoiding collisions between tools or with the piece. He chooses the tools to use, and checks the quality of the parts obtained, for example the surface conditions, the respect of the tolerances, etc.

In a second production phase, a series of parts are produced on the pre-set machining module, with the parameters defined during the development. This phase is the only productive phase; it is often performed 24 hours a day, the machining module being fed with raw material by means of a mothership or a plow loader (raw parts).

It happens that the production of a series of parts is interrupted, for example to replace worn tools, to produce another type of parts on the same machining module, for the maintenance of the machine, etc., then resumed later. In such a case, a set-up phase is necessary to apply the parameters defined previously during debugging. This setting is faster than focusing.

During start-up, it is often necessary to replace the tools mounted on the machine with another set of tools suitable for the machining to be performed. The precision of the positioning of these tools determines the quality of the machining, but is difficult to reproduce during successive start-ups.

In addition, during the production phase, it is not impossible to have as and when machining new parts, and in particular for large series, position drifts between the door- tool and the support of room, drifts in particular due to the thermal expansion of the machines.

State of the art [0010] Various solutions have therefore been proposed in the prior art to ensure correct relative positioning between the tool holder and the part support during the production phase and during start-up, it is that is, in accordance with the relative position between the tool holder and the work support during focusing.

Numerous in-situ measurement techniques used in machine tools are concerned with measuring the relative position between the workpiece or the workpiece support and the tool itself. However, in this case, the measurement of the relative position between the workpiece or the workpiece support and the tool is tainted by the effects of tool wear and thermal drift of the machine tool during operation.

[0012] Also, this type of relative position measurement is generally carried out in two dimensions, that is to say in two directions, as in DE 20 2016 004 237 U.

This relative location between the workpiece or the workpiece support and the tool being limited to two dimensions (for example Y and X, respectively the lateral and vertical direction), it is not sufficiently complete to ensure the correct relative position, so that one must resort to another technique for the measurement of the third dimension (eg Z, the direction of advancement / retreat of the support piece also called "material direction"). This situation not only increases the cost of the measurement technique, but also its implementation time, and it also adds an error by using two measurement series simultaneously.

The document US 2014 362 387 AA discloses an optical measuring device placed on the tool holder and for verifying that a target object will not interfere with the tool holder. This optical measuring device uses a calibration element with several inclined parts to characterize the geometrical parameters of the laser beam measuring device, in particular the position between the reflected ray sensor and the incident ray emitter. This calibration element does not intervene during the measurement of the relative position between the tool holder and the target object which may be a workpiece.

[0015] US 2010 111 630 AA discloses a tool repositioning system for a machine tool, comprising irregularly shaped targets located on the tool and allowing the optical measurement of the precise position of the tool by tools. Optical measuring elements whose position is not specified.

US 2007 253 002 AA discloses an optical measurement system of the distance between two bodies that are to be aligned, respectively comprising a transmitter element and a receiver element placed at the ends of the two bodies.

Document US Pat. No. 5,831,734 describes a solution in which an optical sensor is integral with the tool holder and carries out the identification of the relative position of this tool holder with respect to a workpiece provided with a distinctive mark ( groove).

These solutions, however, do not allow to be determined by a single step of shooting the relative position between the workpiece and the tool, this single shooting step giving the information to determine this relative position in the three dimensions of space.

These solutions also do not make it possible to overcome variable parameters in real time during machining, in particular tool wear as well as thermal variations of the tool and / or the tool. workspace of the machine tool that receives the workpiece.

BRIEF SUMMARY OF THE INVENTION [0020] An object of the present invention is to propose a technology for performing a relative position measurement between a first object and a second object, and in particular between a tool holder and a part support , free from the limitations of known measurement techniques.

Another object of the invention is to provide a technology for performing a relative position measurement between a tool holder and a part support, and more generally between a first object and a second object, which provide the three-dimensional relative position between the first object and the second object from a single shooting step.

According to the invention, these objects are attained in particular by means of an optical system for the three-dimensional measurement of the relative position between a first object and a second object on which said optical system is intended to be mounted, said optical system. comprising a first camera system and a second camera system, in which: - the depth of field of the first camera system is at least 10 times greater than the depth of field of the second camera system and the optical system is arranged so that the optical path of the first camera system and the optical path of the second camera system have a common section comprising the image focal plane of the first camera system and the camera. focal plane image of the second system of shooting.

Such an optical system can be placed on one of the two objects concerned (the second object) and allows by the two systems of shooting, a simultaneous capture of two sharp images in two neighboring locations one of the two other on the other of the two objects (first object), these two locations of the first object being located at a slightly different distance from the second object. Such an optical system makes it possible, as will be described in detail hereinafter, thanks to the two images, to locate three-dimensionally the relative position between the first object and the second object which carries the optical system.

According to one embodiment, the optical system is arranged so that the optical path from the object (first object) passes through at least a portion of one of the first and the second camera system before 'reach each other among the first and second shooting system. In this way, it is possible to have an optical path section at the input / output of the optical system that is common or very similar for the first and the second camera system. it is thus possible not only to group the first and second camera systems on the same optical system but also to be able to locate two neighboring locations on the first object, which are close to a few tens of millimeters, or even a few millimeters or even less than a millimeter.

One or more of the following arrangements can be implemented: the first and second camera systems are arranged in parallel with each other and the optical system further comprises an optical module disposed between the first and the second camera system and configured to deflect a portion of the light rays passing through at least a portion of one of the first and second camera systems to the other of the first and the second camera system: in particular this optical module is a catoptric optical system such as a mirror; the focal length of the second camera system is greater than the focal length of the first camera system; - The magnification of the first system of shooting is less than or equal to the magnification of the second system of shooting.

The present invention also relates to a three-dimensional optical measuring device for measuring the relative position between a first object and a second object, comprising an optical system as described in the present text and intended to be mounted on said second object, and a three-dimensional target intended to be placed on said first object and to serve as positioning reference, said three-dimensional target comprising on a useful face: a first structure defining a plane reference face, and a second structure presenting a face inclined with respect to said reference plane face, wherein the difference between the focal length of the second camera system and the focal length of the first camera system is between the minimum distance and the maximum distance between the camera and the camera. reference face of the inclined face.

This target is also possibly in accordance with one or more of the following provisions: the surface of said first portion is reflective in a diffuse reflection, and the surface of said second portion is reflective according to a reflection specular; said second portion is distributed according to a series of localized zones positioned in the first portion; the surface of said inclined face has elements in relief or specular elements regularly distributed; the localized zones define between them a geometrical figure belonging to the following list: quadrilateral, parallelogram, rectangle, square, rhombus, regular polygon and circle; - The localized areas of said second portion are formed of islands or segments distributed in the first portion; - the localized areas are in chrome; - The first structure and the second structure are arranged on the useful face concentrically with respect to one another, in particular the first structure surrounds the second structure; the localized zones of the second portion of the first structure define a square which surrounds the second structure; the first structure defines an opening for a housing housing said second structure; - The second structure is disposed in said housing with the inclined face which is set back relative to the reference face of said first structure, in particular behind, behind the plane delimited by the reference face; - The surface of the inclined face of the second structure is striated, in particular the surface of the inclined face of the second structure is covered by one of the following elements: etched network, structured grid or specular line network.

This three-dimensional target has on its side forming the useful face of a double structure, defining respectively a first planar reference face and a second reference face, defining a plane inclined relative to the first reference face. This three-dimensional geometry of the target, combined with specific optical characteristics and different surfaces respectively composing the first reference face and the second reference face, allow optical identification in the three dimensions X, Y and Z of the space of this target compared to the optical system used. In one embodiment, this optical system makes it possible to carry out this optical registration, namely resulting in the measurement of relative position, by means of a single step of taking both the first reference face and the second face of inclined reference: it is therefore a simultaneous shooting of the image of the first reference plane face and the second reference face. This simultaneous shooting can be carried out according to two, three or more iterations, see burst on n shots (n integer greater than one, for example ranging from two to fifteen). In this way, it is possible to have several images (a series of images) of both the first plane reference face and the second reference face, which makes it possible to perform a processing by calculation algorithms, not not a single image of the first planar reference face and the second reference face, but a processing of the series of images of both the first planar reference face and the second reference face, and thus gain in precision.

In particular, in one possible arrangement, this generation of image (s) of the first reference plane face and the second reference face, is performed by the optical system used without having to perform a focus, as it will be explained later. In this case, there is no specific adjustment to operate in the optical system, which allows a significant time saving for the realization of the measurement of the relative position of the three-dimensional target. This solution has the advantage over the prior art not to require either several measurement steps or even to change the settings and in particular the focal length of the optical system facing this target.

Also, when this target is used for the relative position measurement between a tool holder and a workpiece support, it is possible to overcome the wear of the tool as well as the thermal variations of the tool and or the work space of the machine tool that receives the workpiece by placing this target on the tool holder.

Thus, the optical system can simultaneously identify its position with respect, on the one hand, to the reference face (or first reference face) via the image generated by the first camera system and, on the other hand, to at least one zone of the inclined face (or second reference face) which is identified via the image generated by the first camera system, and whose location on the target is known with respect to the reference face.

The present invention further relates to an arrangement for three-dimensional optical measurement of the relative position between a first object and a second object, comprising: - an installation comprising a first object and a second object. an optical measuring device as described in the present text in which; the first camera system is configured so that its image focal plane is able to correspond to the reference face of the first structure, and the second camera system is configured so that its image focal plane is able to be secant with the inclined face of the three-dimensional target. According to a second possibility, compatible with the aforementioned first possibility or taken alone, the optical measuring device is such that: the focal length of the first camera system is capable of enabling the image focus to be placed on the first structure; the focal length of the second camera system is suitable for placing the image focus on the second structure.

Such an installation is for example an equipment, a machine, a particular scientific or technical module having a first object and a second object movable relative to each other and for which it is necessary to perform a referencing of relative position in three-dimensional space. For example, this installation is a machine tool or a machining module with as a first object the tool holder or one of the tool holders and as a second object the workpiece support carrying the workpiece (bar, blank, .. ..). In another example, this installation is an assembly unit of electronic components on a PCB (or Printed Circuit Board for printed circuit), with as a first object the support of the printed circuit and as a second object the clamp or other mounting tool of an electronic component. According to yet another example, this plant is a cell culture module for performing the seeding of series of wells housed on microplates, the first object being the support of the microplate and the second object being the support of the injection device of the microplates. cells to grow.

The present invention also relates to a three-dimensional optical measurement method according to three orthogonal directions X, Y and Z, between a first object and a second object aligned and distant from each other in the main direction Z, in which: - a three-dimensional target comprising a useful face forming a positioning reference is provided, and comprising: a first structure defining a plane reference face distributed between at least: a first portion whose surface is reflective according to first reflection parameters, and - a second portion whose surface is reflective according to second reflection parameters different from the first reflection parameters, and * a second structure having a face inclined with respect to said reference plane face - an optical system is provided comprising a first system of shooting and a second system of shooting, d in which: - the depth of field (DOF1) of the first camera system is at least 10 times greater than the depth of field (DOF2) of the second camera system, and - said optical system is arranged in a part so that the optical path of the first camera system and the optical path of the second camera system have a common section comprising the image focal plane of the first camera system and the image focal plane of the second camera system. also, so that the difference between the focal length of the second camera system and the focal length of the first camera system is between the minimum distance and the maximum distance separating the film reference of the inclined face, - said three-dimensional target is positioned on the first object so that on the one hand the focal length of the first shooting system is able to place the image focus of the first first system of shooting on the first structure of the target and secondly the focal length of the second camera system is able to place the image focus of the second camera system on the second structure of the target positioning said optical system on the second object, performing at least one shooting simultaneously with the first system of the optical system and with the second system of the optical system, whereby for each shot by the optical system, on the one hand the first image system generates a first image of the target makes it possible to identify on the reference face the position of the second portion relative to the first portion (in particular the position of the localized areas on the reference face), which gives first information on the relative position in the X direction of the target compared to the first system. first and second information on the relative position between the target and the first shooting system in the Y direction, and secondly the second camera system generates a second image of the camera. target comprising a net portion corresponding to a location of the inclined face of the second structure, which gives a third information on the distance between said target and said second camera in the Z direction.

By this method, we can have spatial geometric information related to the (first) reference face and the inclined face or second reference face of the three-dimensional target, to deduce the relative position in the three directions. X, Y and Z between the first object and the second object. Beforehand, we will have performed the referencing of the three-dimensional relative position between the target and the first object and the referencing of the three-dimensional relative position between the optical system and the second object.

It should be noted that in one embodiment, the shooting or image generation by each camera system of the optical system is performed without performing the development of the corresponding shooting system. Indeed, it is the relative position in the three directions X, Y and Z of the shooting system with respect to the object it is looking at (and therefore both the relative position of the first system of shooting relative to the reference face of the target and the relative position of the second image system with respect to the inclined face of the target) as well as the optical properties, and in particular the very different depth of field of each imaging system. shooting of the optical system, which makes it possible to simultaneously generate two images, respectively of the reference face of the inclined face. The analysis of these two images (see two sets of images) makes it possible to deduce information on the relative position in X (this direction X corresponding for example to the height) and in Y (this corresponding Y direction for example to the lateral lateral shift) and Z (this direction Z corresponding for example to the horizontal distance, principal) between the target and the optical system, and thus the three-dimensional relative position between the first object which carries the three-dimensional target and the second object which carries the optical system.

In one embodiment, after positioning the three-dimensional target on the first object and positioning the optical system on the second object, an additional step of spatially referencing the X, Y, and Z position is performed. the target relative to the first object by the optical system.

According to one possible arrangement, the second portion of the plane reference face is distributed according to a series of localized zones positioned in the first portion and the first image generated by the first image system makes it possible to identify the position of the localized areas of the second portion on the reference face, which gives information on the relative position between said localized areas and the first shooting system to deduce the relative measurement in the Y direction and in the X direction.

In one embodiment, the measurement method is a method for measuring, in the three-dimensional space of a machine tool, the relative position between a tool holder and a workpiece support, in which said first object is said tool holder and said second object is said workpiece support, in which an additional step is carried out, before said step of simultaneous shooting with said optical system, according to which: - the toolholder and the a workpiece support aligned in the main direction Z so that the useful face of said three-dimensional target is in the optical path of the optical system.

According to another possible arrangement, the optical device further comprises a third camera system disposed on the tool holder and configured to identify the orientation of the useful face of the target and / or the angular orientation of the toolbox.

BRIEF DESCRIPTION OF THE FIGURES [0041] Examples of implementation of the invention are indicated in the description illustrated by the appended figures in which:

Fig. 1 illustrates a three-dimensional measuring device comprising a three-dimensional target and an optical system according to the invention,

Fig. 2A illustrates the use of the three-dimensional measuring device of FIG. 1 in a machine-or machine for measuring in space the relative position between the tool holder and the workpiece support (also called material spindle),

Fig. 2B shows the part of FIG. 2A corresponding to the tool holder with the three-dimensional target, then the direction II B of FIG. 2A, in the Z direction, as seen by the optical system when the target is oriented towards the optical system,

figs. 3A, 3B and 3C are three views illustrating the structure of the three-dimensional target, respectively from the front, in perspective and in section, and FIGS. 3D and 3E are perspective views of the second structure of the target respectively as in Figs. 3A, 3B and 3C and according to an alternative embodiment, FIGS. 4A and 4B illustrate the processing of the image generated by the second camera system of the optical system. fig. 5 shows in perspective and exploded a tool holder equipped with the three-dimensional target according to the invention. fig. 6 illustrates the mounting of the three-dimensional optical measuring device according to the invention in a machine tool.

Example (s) of embodiment of the invention [0042] In FIG. 1, there is shown an optical device 10 comprising an optical system 100 and a three-dimensional target 200 capable of cooperating together to perform the three-dimensional measurement of the relative position between the target 200 and the optical system 100. Indeed, in this measurement position the target 200 is oriented towards the optical system 100, parallel to a main axis, forming a main horizontal Z direction. For this purpose, at the output of the optical system 100 the optical path O is orthogonal to a useful face 202 of the target 200.

The target 200 is now described in relation to FIGS. 1,3A, 3B and 3C. The target 200 is in the form of a pellet, here of cylindrical shape of circular section (it could be of square section or other), one side forms the useful face 202 for carrying out the measurement. For the realization of the measurement, this useful face 202 is thus turned towards the optical system 100, and in particular towards the input face 102 of the optical system 100, the Z axis corresponding to the main direction (horizontal in the figures) separating the useful face 202 of the input face 102 of the optical system 100.

The surface of the useful face 202 of the target 200 is distributed between a first structure 210 and a second structure 220. The first structure 210 comprises a flat reference face 212 whose surface is smooth and is distributed between a first portion 214 whose surface is reflective in a diffuse reflection and a second portion 216 whose surface is reflective in a specular reflection. In one embodiment the first portion 214 is coated with a diffusing reflective layer, for example barium sulfate BaSO4, and the second portion 216 is formed of a reflective layer according to a specular reflection, for example chromium. In the illustrated embodiment, the second portion 216 consists of several localized zones 217 in the form of circles forming islands arranged within the first portion 214 which is continuous. These localized areas 217 may have other shapes, such as segments or islands of other than a circle. These localized zones 217 define between them a geometrical figure belonging to the following list: quadrilateral, parallelogram, rectangle, square, rhombus, regular polygon and circle. This geometric figure can be a geometric figure with central symmetry. In FIGS. 3A and 3B, twenty-four circular localized zones 217 are arranged in a square. The purpose of this first structure 210 is to be able to precisely identify its center C3 using standard vision tools. With the square shape, the two diagonals C1 and C2 of this square are intersecting in the center of the square. Note that in the measuring position, as shown in Figures 1 to 3 and 5, the reference face 212 is disposed parallel to the X and Y directions, respectively forming a direction (a vertical axis) and a direction (an axis transverse horizontal in the case of the illustrated arrangement.

The second structure 220 has an inclined face 222 with respect to the reference face 212: this inclined face 222 is substantially flat, the average plane of this inclined face forming with respect to the reference face 212 an acute angle α understood between 10 degrees and 80 degrees, for example between 20 and 30 degrees, and preferably of the order of 25 degrees (see Fig. 3C).

In one embodiment, the surface of this inclined face 222 is not smooth but has relief elements 224 forming surface irregularities either random or according to a predetermined geometry, for example drawing between them a shape of grid or a network of lines, thus constituting a structured grid (not shown) or a structured network of lines (see Fig. 3D).

Such relief elements 224 may be protruding or recessed, that is to say recessed, relative to the mean plane of the inclined face 222, especially in the form of small roughnesses, or any other irregularity. of surface. Such relief elements 224 may be present on the entire surface of the inclined face 222. Such relief elements 224 may be regularly distributed over the entire surface of the inclined face 222. For example, these relief elements 224 may form a together delimiting a grid pattern or grating, or more generally a structured surface or a rough surface that allows the light reflected on this inclined surface 222 to be well diffused. The surface of the inclined face 222 of the second structure 222 is, for example covered by one of the elements according to etched grating or structured grid, with a pitch between the patterns of the grid or the grating of between 5 and 100 micrometers, in particular between 5 and 50 micrometers, and in particular between 8 and 15 micrometers, for example of the order of 10 micrometers.

For example, this inclined face 222 is unpolished silicon or ceramic, or unpolished metal or glass, or any other structurable material, and the relief elements 224 were obtained by photolithography, removal machining chips, direct writing, etc., or any other method of structuring. These relief elements 224 form for example depressions and / or protrusions respectively recessed / protruding from the average plane by a few micrometers or a few tens of micrometers, especially between 0.5 and 50 micrometers.

In another embodiment, as illustrated in FIG. 3E, the surface of this inclined face 222 is smooth and comprises a network of lines of chromium, or of another material causing a specular reflection of these lines of chromium which constitute specular elements 225. These specular elements 225 in the form of lines are arranged parallel to each other. In the measuring position, these specular elements 225 in the form of lines or strips are arranged parallel to the plane Y, Z, so that along the inclined surface, in the Z direction, one meets these lines one by one (this is also the case while moving in direction X). The substrate forming the wafer of the second structure 220 may then be in different materials, including glass or silicon, with on the inclined face 222 a diffusing reflecting layer, for example barium sulfate BaSO4 which alternates with the specular elements 225 or well which covers the entire surface of the inclined face, with the specular elements 225 disposed above this diffusing reflective layer. In an exemplary embodiment, these specular elements 225 in the form of lines form a network with a pitch of 25 micrometers, the lines (in particular chromium) having a width of 12.5 micrometers, equal to the width of the line spacing or portion with a diffuse reflection also in the form of lines or strips of width 12.5 micrometers. According to another embodiment, a pitch of 10 microns or more generally a pitch between 5 and 50 microns is used. It should be noted that these specular elements 225 which alternate with the rest of the surface which makes a diffuse reflection, could take other forms than continuous lines or segments forming strips, in particular discontinuous lines or dots, patterns such as friezes of points, circles, triangles, or any other geometric form.

According to a non-illustrated embodiment, the inclined face 222 of the second structure 220 carries relief elements 224 punctual and salient, in the form of small mounds or pins, which are divided into parallel rows with each other, the elements of 224 relief being offset from one row to another, to form a staggered pattern. According to another embodiment not illustrated, the inclined face 222 of the second structure 220 carries relief elements 224 salient in the form of segments parallel to each other and equidistant in two series intersecting at 90 ° from each other . This set of raised elements 224 constitutes a grid pattern. Note that this grid can be formed of two series of segments parallel to each other, with series of segments intersecting at an angle different from 90 ° from each other. In FIGS. 3A, 3B, 3C and 3D, the inclined face 222 of the second structure 220 carries hollow relief elements 224 in the form of a series of segments parallel to each other and equidistant from one another along the direction X: these elements in relief 224 form in this case grooves. This direction X is therefore orthogonal to the direction of the segments forming the relief elements 224.

In the embodiment of FIG. 3E, the surface of the inclined face 222 of the second structure 220 is covered by a network of specular lines 225, namely continuous strips parallel to each other whose surface has specular reflection properties.

Thus, in some of the aforementioned cases, and in particular those of Figures 3D and 3E, the surface of the inclined face 222 of the second structure 220 is striated.

According to the embodiments shown for the target 200, the wafer delimiting the target 200 has on its useful face 202 the first structure 210 which occupies the bulk of the surface of the useful face 202, and within the first structure 210, an area reserved for the second structure 220. In this situation, the first structure 210 surrounds the second structure 220. More specifically, the localized zones 217 of the second portion 216 of the first structure 210 define a square that surrounds the second structure 220. According to one possible arrangement, and in the case of the embodiments of the target 200 as shown, the first structure 210 and the second structure 220 are arranged on the useful face 202 concentrically with respect to each other. to the other. Furthermore, as in the cases shown, the first structure 210 defines an opening 218 for a housing 219 housing said second structure 220, which is for example disposed on a wafer having the inclined face 222. When the wafer is housed in the housing 219 of the first structure 210, its inclined face 222 is turned towards the outside of the housing 219, towards the opening 218. In this case, the second structure 220 is disposed in said housing 219 with the inclined face 222 which is is set back from the reference face of said first structure 210: this means that the inclined face 22, so the second structure 220 is disposed behind the plane delimited by the reference face 212 (relative to the direction main Z, see Fig. 3B), in the housing 219, for example from 0.05 to 2 millimeters or of the order of 0.15 millimeter. According to another possibility, not shown, the second structure 220 is disposed forward, in front of the plane defined by the reference face 212. According to yet another possibility, not shown, the second structure 220 is disposed on either side of the plane delimited by the reference face 212, namely a part of the inclined face 222 is disposed behind and the other part of the inclined face 222 is disposed forward with respect to the reference face 212.

In order to protect the first structure 210 and the second structure 220 of the environment (dust, oil, shocks ...), as shown in FIG. 3C, the target 200 comprises a protection plate 230 in a transparent material, in particular glass, covering the first structure 210 and the second structure 220 on the side of the useful face 202. According to one possible embodiment, as shown in fig. 3C, the target 200 comprises in the form of a stack the following elements. A bottom wall 231 is surmounted by a plate 232 formed of a recessed plate at its center in order to delimit the housing 219 delimited by the opening 218 on the side of the useful face 202. The plate 232 is surmounted by the plate of protection 230 closing the housing 219. The whole is surrounded by a cylindrical wall 234 retaining all of the target 200. The protection plate 230 includes the second structure 220 is for example a silicon wafer housed in the housing 219 with the inclined face 222 (carrying the raised elements 224 or specular elements 225) facing the useful face 202. The face of the plate 232 facing the useful face 202 comprises a reflective layer 233 according to two zones as previously described respectively in relation to with the first portion 214 (reflecting surface in diffuse reflection) and the second portion 216 (reflecting surface according to a specular reflection , in particular in the form of localized elements 217).

Furthermore, the target 200 may be equipped with an RFID-type chip (radio frequency identification), not shown, in order to allow the storage and reading of a unique identifier and data in relation to the target 200 and in relation to a first object on which the target 200 is intended to be mounted, in particular a tool holder 310 (see FIGS. 5 and 6): for example the reference of this tool carrier 310 and other information related to the use of this tool holder (for example its serial number, its type, its adjustment relative to the material center or part support, the number of times it has been used ...).

Referring now to FIG. 1 to present the optical system 100 associated with the target 200 which has just been described to form together an optical device 10 for measuring the relative position between two objects in the three directions of space. In particular, we consider an orthonormal space in a Cartesian coordinate system X, Y and Z, which is direct on the figures). This optical system 100 is intended to take simultaneously, during the same sequence of shots, both an image of the first structure 210 of the target 200 and at the same time an image of the second structure 220 of the target 200. According to the present text, this simultaneous shooting of the two images is done without focusing, which allows a great speed of execution of this shooting. Other features, particularly related to the specific structure of the target 200 which has just been described, also allows maximum accuracy. The Applicant Company has provided a three-dimensional optical measuring device 10 according to the present disclosure to achieve in one half second or less a repeatable relative measurement with an accuracy of one micrometer or less.

This optical system 100 comprises a first camera system 110 and a second camera system 120. According to one arrangement, said optical system 100 is arranged so that the difference between the focal length of the second camera system 120 and the focal length of the first camera system 110 is between the minimum distance and the maximum distance separating the reference face 212 from the inclined face 202. According to another arrangement, the depth of field DFO1 of the first system 110 is much greater and in particular at least 10 times greater than the depth of field DFO2 of the second camera system 120. For example the depth of field DFO1 of the first camera system 110 is between 10 and 10000 , or even between 100 and 5000 greater than the depth of field DFO2 of the second camera system 120. Among various possibilities, the depth of field DFO1 of the pr the first camera system 110 is greater than or equal to 0.8 millimeters, or it is between 0.5 and 5 millimeters, or it is between 0.8 and 3 millimeters, or it is between 1 and 2 millimeters. Also, according to different possibilities, the depth of field DFO2 of the second camera system 120 is less than or equal to 0.1 millimeters, or it is between 5 and 50 micrometers, or it is between 8 and 30 micrometers, or although it is between 10 and 20 micrometers.

This allows the first camera 110 to do naturally and without further adjustment, its focus on the entire reference face 212 of the first structure 210 in a range of distance between the target 200 and the first system shooting 110 may vary over a few millimeters. In parallel, the second camera system 120 is able to do naturally and without further adjustment, focusing on the portion of the inclined face 222 of the second structure 210 which is at the distance of the second camera system 120 corresponding to the focal length of the second camera system 120. According to one possibility, the magnification of the first camera system 210 is smaller than the magnification of the second camera system 220.

Each camera system within the meaning of the present invention (first camera system 210 and second camera system 220) corresponds to an optical system, in particular a centered optical system, comprising a set of components. optical and an image acquisition system. Such an image acquisition system makes it possible to take photographs and / or videos, and is for example a camera or a camera, in particular a digital camera. According to one possible arrangement, the first image acquisition system 112 of the first camera system 110 and the second image acquisition system 122 of the second camera system 120 are synchronized in order to simultaneously take a first image by the first camera system 110 and a second image by the second camera system 120.

To allow simultaneous access to the vision of the target 200 by the first camera system 210 and the second camera system 220, the latter have a portion of common optical path that goes to and from the object viewed by the optical system 100, in this case the target 200 (see Figures 1 and 2) after mounting the target 200 on the first object and mounting the optical system 100 on the second object. For this purpose, in the measurement position, the first camera system 210 is rotated towards the useful face 202 of the target 200 and forms a camera system aligned with the target 200, and the second camera system Shooting 120 has an optical path 126 which joins the optical path 116 of the camera system 110 aligned with the target 200 and forms an eccentric shooting system with respect to the target 200, with respect to the optical axis O of the optical system 100, and with respect to the common portion of the optical paths 116 and 126 (aligned with the target). In other words, the optical path of the image system aligned with the target 200 is substantially perpendicular to the reference face 212. The optical axis O is superimposed with the average radius of the common portion of the first optical path 116 and the second optical path 126. In this common portion, the sections of the first optical path 116 and the second optical path 126 are parallel to each other, but not necessarily superimposed.

In particular, as illustrated in FIGS. 1 and 2, the first shooting system 210 is turned towards the useful face 202 of the target 200, namely is oriented perpendicularly with respect to the useful face 202 of the target 200. This means that the optical axis O and the common portion of the optical paths 116 and 126 are aligned with the target 200 and are perpendicular to the useful face 202 (and therefore to the reference face 212) of the In this configuration, as seen in FIGS. 1 and 2, the optical axis O and the common portion of the optical paths 116 and 126 are parallel to the main direction Z, and are orthogonal to the transverse directions X and Y , as well as the X, Y plane.

In the common portion of the optical paths 116 and 126, the optical rays are at least partially merged or simply parallel to each other. The second eccentric imaging system 120 has an optical path portion 126 internal to the second imaging system 120 which is preferably parallel to the optical axis O. This internal optical path portion 126 is connected to the , or more precisely joined the optical path 116 of the first camera system 110 aligned by a dedicated optical module 128, comprising a catoptric optical system such as a mirror 129. In this way, the input of the optical pickup system eccentric view (here the second camera system 120) is connected to the path or optical path of the aligned image system (here the first camera system 110).

In a more general manner, it is conceivable that one of the first camera system 110 and the second camera system 120 is turned towards the useful face 202 of the target 200 and forms a the image system aligned with the target 200, and the other image system among the first image system 110 and the second image system 120 has an optical path 126 which joins the optical path 116 of the Shooting system 110 aligned with the target 200 and forms an eccentric shooting system. This means that the other camera has an optical axis that passes through the inclined face 222, that is to say the second structure 220 of the target 200. Also, the first camera system 110 and the second camera system 120 are arranged in parallel with each other. In addition, the optical system further comprises an optical module 128 (for example with a catoptric optical system such as a mirror) disposed between the first camera system 110 and the second camera system 120 and configured to deviate a portion of the light rays passing through at least a portion of one of the first and second image systems to the other of the first and second image systems. In contrast, the optical system 100 is arranged so that the optical path from the viewed object (the target 200 in FIGS. 1 and 2) by the optical system 100 passes through at least a portion of one of the first 110 and the second camera system 120 (the first camera system 110 in FIGS. 1 and 2) before reaching the other one of the first camera system 110 and the second Shooting system 120 (the second camera 120 in Figures 1 and 2).

In one embodiment, the focal distance of the second camera system 120 is greater than the focal length of the first camera system 110. For example, the difference between the focal length of the second camera system 120 and the focal length of the first camera system 110 is between 0.5 and 5 millimeters.

In one embodiment, the magnification of the first camera system 110 is less than or equal to the magnification of the second camera system 120. For example, the magnification of the first camera system 110 is between 0.2 and 1 times the magnification of the second camera system 120. For example, the magnification of the first camera system 110 is between 0.3 and 0.8, or between 0.4 and 0.6, preferably around 0.5 times the magnification. second camera system 120.

In the embodiment of FIGS. 1 and 2, the optical system 100 further comprises a light source 140 oriented towards the three-dimensional target 200, this light source 140 being arranged in order to constitute a lateral illumination of the Three-dimensional target 200. For this purpose, this light source 140 is arranged eccentrically and inclined with respect to the optical path 116 + 126 of the optical system 100. In particular, the light rays of the light source 140 form with the reference 212 of the target at an angle such that their specular reflection on the reflecting surfaces of the target, and in particular on the localized areas 217, generates reflected light rays which do not penetrate into the optical system 100. Similarly, when the inclined face 222 has specular elements 225, the reflection of the light rays of the light source 140 on these specular elements 225 does pen do not go into the optical system 100.

According to one embodiment, the first shooting system 210 used and the second shooting system 220 used are telecentric. As a reminder, telecentricity is a feature of an optical system in which all major rays (the central radius of each ray beam) passing through the system are substantially collimated and parallel to the optical axis. In the case of telecentric optics, the notion of depth of field is replaced by that of working distance. According to another embodiment, the first camera system 210 used and the second camera system 220 used are not or not both telecentric. In the case where they are both telecentric, they can also be used to measure the geometric characteristics of the tools arranged on the tool holder 310.

Referring now to Figures 2A and 6 to expose the three-dimensional optical measurement method between the target 200 and the optical system 100, in the case of a machine tool whose machining module 300 includes such a device. 10. The X, Y and Z reference directions are those of the machine tool, in particular of the machine tool frame, which gives a vertical X direction (or first transverse axis), a main horizontal direction Z (or main axis) and a lateral horizontal direction Y (or second transverse axis). The target 200 is placed on the tool holder 310 serving as the first object (see Fig. 5): the tool holder 310 extends in a horizontal main direction, corresponding to the X axis, with the possibility of rotating around this axis, a portion of the tool holder 310, for example the clamp, carries housings on its periphery, usually dedicated to the mounting of the clamping / loosening tool of the clamp, in which one can put the target 200, possibly associated with an RFID chip as previously discussed. Furthermore, the optical system 100 is mounted on the work support 320 serving as a second object (see Fig. 6) and receiving the workpiece 322. The work support 320 extends along its horizontal main direction, corresponding to the Z axis, with the possibility of turning around this axis Z. Then, the workpiece support 320 and the tool holder 310 are placed in a close position, prior to a machining step, placing the tool 312 and the workpiece to be machined close to each other, in a relative measuring position. The positioning of the target 200 on the tool holder 310 and the positioning of the optical system 100 on the workpiece support 320 allow that in this relative measurement position, the target 200, and more precisely the reference face 202, can be placed in the extension of the optical axis O of the optical system 100 (note that this optical axis O is parallel to the direction Z). Thus, the reference face 202 of the target 200 is turned towards the input face 102 of the optical system 100.

As in the case shown in FIG. 6, the optical device 10 further comprises a third camera 130 disposed on the tool holder 310 and configured to locate the orientation of the useful face 202 of the target 200 and / or the angular orientation of the part rotating the tool holder 310, in particular around the axis X. A preliminary step is performed, positioning the target 200, before the step of simultaneous shooting with said optical system 100, according to which: has the tool holder 310 and the workpiece support 320 so that the useful face 202 of the three-dimensional target 200 is in the optical path O of the optical system 100. In particular, it is possible to use the third camera system 130 for locating the angular orientation of the target 200 relative to the rotational part of the tool holder 310, thus with respect to the axis X, which makes it possible to modify, as the case may be, the angular orientation of the rotating part of the carrier tool 3 10 (see arrow R in Fig. 6), and thus set the target 200 so that its useful face 202 is rotated towards the optical system 100. The relative measurement position is obtained in which when the target 200 is oriented in the direction of the optical system 100 as previously discussed in the case of Figures 1 and 2A: in this case, the direction Z extends between the target 200 and the optical system 100.

During the first use of the optical device 10, namely the optical system 100 and an associated target 200, respectively mounted on a part support 320 (or more generally a second object) and a tool holder 310 (or more generally a first object), it is necessary to carry out an additional preliminary step of spatial referencing of the position of the target 200 with respect to the tool holder 310 (or more generally a first object) which carries the target 200 in the three directions X, Y and Z. It should be noted that we obviously know the parameters of the optical system 100, namely the first system 110 and the second shooting system, including their focal length. At this stage, it may be mentioned that when the working space of the machining module 300 is confined and maintained at a constant temperature, this thermal stability gives dimensional stability to the optical device 10 and therefore its parameters.

It will be recalled that the measurement of the three-dimensional relative position between the target 200 and the optical system 100 is used in the case of a machine tool to ultimately know the three-dimensional relative position in X, Y and Z between the door. tool 310 (or more generally a first object) and the part support 320 (or more generally a second object).

In the present text, the three directions X, Y and Z are, for example, the axes of the machining module 300 of the machine tool. Thus, Z can be defined as the main axis, namely the main horizontal direction separating the first object (the tool holder 310) from the second object (part support 320). X can be defined as the vertical direction or more generally a first transverse axis and Y can be defined as a lateral horizontal direction or more generally a second transverse axis. In one embodiment, the tool holder 310 rotates about an axis parallel to this direction X.

During this step of spatial referencing of the position in the three directions X, Y and Z of the target 200 (calibration of the optical device 10), for example with the arrangement of FIGS. 2A and 2B, a pick-up is activated. from the optical system 100, which generates on the one hand the generation by the first image acquisition system 112 of the first image system 110 of a first image of the entire useful face 202 of the target 200 with all the reference face 212 which is clear and secondly the generation by the second image acquisition system 122 of the second image system 120 of a second image of the entire inclined face 222 of the target 200 with only a net area in the form of a horizontal band. This first image comprises the image of the localized zones 217, here delimiting a square (see Fig. 3A), so that the processing of the first image generates the diagonals C1 and C2 of the square and makes it possible to identify the center C3 of the square. square. Thus, since the position of the optical axis O on the first image is known, the determination of the position of the center C3 of the square makes it possible to know the position in X and Y of the target 200 with respect to the optical axis O , but also on the one hand with respect to a reference 314 in the X direction on the tool holder 310 and secondly with respect to a reference 316 in the Y direction on the tool holder 310. Indeed, as can be seen on FIGS. 2A and 2B are used as reference numeral X to a face of the tool holder 310 which is orthogonal to the X axis, for example resulting from a shoulder fitting along a portion of the tool holder 310, visible as a line on the first image and forms said reference 314 in the X direction. Moreover, as seen in FIGS. 2A and 2B, a dimension of the tool carrier 310 is used as a Y reference near the target 200, which is orthogonal to the X axis, and in the case represented which is the width (parallel in the direction Y) of the tool holder 310 near the target 200, for example the diameter when this portion of the tool holder 310 is cylindrical of circular section; this dimension forms said reference 316 in the Y direction.

In parallel, the second image is processed, an example of which is visible in FIG. 4A. By analyzing the local contrast of this second image (see Fig. 4B showing contrast curves as a function of the X position), the XO position in the vertical direction X of the net area of the second image is determined. This analysis is done via an algorithm to determine the sharpest pixels of the image. As the inclination of the inclined face 222 is known, there is a correspondence curve between X and Z of this inclined face 222, specific to the target 200. Thanks to this correspondence curve, the knowledge of the XO position ( see Fig. 4A and 4B) allows to deduce the position ZO of the inclined face 222 on the optical axis O, and therefore the Z position of the target 200 relative to the optical system 100. Moreover, the relative position Z of the optical system 100 relative to the workpiece support 320 is known by a measurement rule (not shown) arranged along the Z axis on the workpiece support 320 and which supports the optical system 100. Similarly, the relative position in Z of the target 200 relative to the mark 314 of the tool holder 310 is known. By performing this operation multiple times by changing each time the distance Z of the workpiece support 310 relative to the tool holder 320 (for example by moving backwards or moving the work support 310), it is possible to reconstructing the three-dimensional image of the inclined face 222 of the target 200, and having a reference base forming a map for the three-dimensional coordinates of the inclined face 222 of the target 200 relative to the tool holder 310. In the end, it is the entire useful face 202 of the target 200 (reference face 212 and inclined face 222) which is referenced spatially in the three directions X, Y and Z with respect to the tool holder 310.

Then, we can achieve the actual measurement whenever necessary during operations of use of the machining module 300 equipped with this target 200 and this optical system 100, not removed in the meantime to maintain the accuracy of the measurement of spatial referencing explained previously. For this purpose, for example with the arrangement of FIG. 2A. If necessary, rotation of the workpiece support 320 about its axis of rotation parallel to the X axis (see arrow R in Fig. 6) is performed to align the target 200 with the optical system 100. Then, one activates a shooting by the optical system 100, which generates on the one hand the generation by the first image acquisition system 112 of the first image system 110 of a first image of the whole image. useful face 202 of the target 200 with all the reference face 212 which is clear and secondly the generation by the second image acquisition system 122 of the second image system 120 of a second image of any the inclined face 222 of the target 200 with only a net zone in the form of a horizontal band corresponding to the focal length of the second camera system 120. The analysis of this first image makes it possible, as explained above, to identify the center C3 of the square f ormé by the localized elements 217, and thus the X and Y position of the target 200 with respect to the optical axis O, and also with respect to the tool holder 310. The analysis of the second image and in particular of the position of the net area of the second image (as in Figure 2A) in the X direction allows to know the Z position, so the distance, from the target 200 relative to the optical system 100. Indeed, for the second image as we know the position Z of each pixel of the image of the inclined face 222 relative to the references 314 and 316 on the tool holder 310, it is possible to very quickly measure the position Z of the target 200 and therefore the tool holder 310.

It is understood from the foregoing that in this way, measurements are made very quickly, only by the analysis of the two images generated by the optical system 100, and without loss of time that would require a setting or an adjustment of the optical system 100, the position X, Y and Z of the target 200 relative to the optical system 100 and from the tool holder 310 relative to the work support 320. This is possible because we know the position in X, Y and Z of the optical system 100 relative to the work support 320.

The present text also relates to an optical system for the three-dimensional measurement of the relative position between a first object and a second object on which said optical system is intended to be mounted, said optical system comprising a first system of shooting and a second camera system, in which: the depth of field of the first camera system is at least 10 times greater than the depth of field of the second camera system, and the optical system is arranged to so that the optical path of the first camera system and the optical path of the second camera system have a common section comprising the image focal plane of the first camera system and the image focal plane of the second camera system. view.

The present text also relates to a three-dimensional optical measurement method according to three orthogonal directions X, Y and Z, between a first object and a second object aligned at a distance from each other in the main direction Z, in which: a three-dimensional target comprising a useful face forming a positioning reference and comprising: a first structure defining a planar reference face distributed between at least: a first portion whose surface is reflective according to first reflection parameters; and a second portion whose surface is reflective according to second reflection parameters different from the first reflection parameters, and * a second structure having a face inclined with respect to said reference plane face - an optical system comprising a first shooting system and a second system of shooting, in leque 1: the depth of field of the first camera system is at least 10 times greater than the depth of field of the second camera system, and said optical system is arranged on the one hand so that the optical path of the first camera system and the optical path of the second camera system have a common section comprising the image focal plane of the first camera system and the image focal plane of the second camera system and other so that the difference between the focal length of the second image system and the focal length of the first image system is between the minimum distance and the maximum distance separating the reference face from the inclined face, said three-dimensional target is positioned on the first object so that, on the one hand, the focal length of the first camera system is able to set the image focus of the first camera capture system. e view of the first structure of the target and that secondly the focal length of the second camera system is able to place the image focus of the second camera system on the second structure of the target. said optical system is positioned on the second object, at least one image is simultaneously taken with the first optical system's recording system and with the second optical system's imaging system, whereby each shot by the optical system, firstly the first shooting system generates a first image of the target to identify on the reference face the position of the second portion relative to.the first portion ( or the position of the zones located on the reference face), which gives firstly a first information on the relative position in the X direction of the target relative to the first camera system and secondly a second information on the relative position between the target and the first shooting system in the Y direction, and secondly the second shooting system generates a second image of the target c omprenant a net portion corresponding to a location of the inclined face of the second structure, which gives a third information on the distance between said target and said second camera in the Z direction.

As already explained above, the optical system 100 thus generates the first image and the second image in a synchronized manner. In addition, the optical system 100 generates the first image and the second image without focusing, which allows shooting immediately and without loss of time.

The present text also relates to a machine tool comprising an optical target as defined above, and a machine tool comprising an optical system as defined above. The present text also relates to a machine tool comprising a machining module equipped with a tool holder and a workpiece support, and an optical measuring device for the three-dimensional measurement of the relative position between said tool holder and said workpiece support, said optical measuring device comprising an optical system mounted on the workpiece support and a target mounted on the toolholder and comprising a useful face forming a positioning reference adapted to be placed in the optical axis of the system optical. For example, the optical measuring device is configured to allow by a single step of shooting the target by the optical system to determine the three-dimensional relative position between the support of the workpiece and the tool holder. Also, in a possible arrangement, the target is arranged so that the image focal plane of the optical system can be confused with the useful face of the target.

Reference Numbers Used in Figures [0082] X Vertical Direction (First Transverse Axis) Y Horizontal Lateral Direction (Second Transverse Axis) Z Horizontal Main Direction Separating First Object from Second Object (Main Axis) C1 Diagonal C2 Diagonal C3 Center Angle of the inclined face R Arrow for the rotation of the tool holder and the target 10 Optical device 200 Three-dimensional target 202 Useful face 210 First structure 212 Reference face 214 First portion (reflective surface in diffuse reflection) 216 Second portion (reflecting surface according to specular reflection) 217 Localized areas 218 Aperture 219 Housing 220 Second structure 222 Inclined face 224 Embossed elements 225 Specular elements 230 Transparent protection plate 231 Bottom wall 232 Platinum 233 Reflective layer 234 Cylindrical wall 100 Optical system O Optical axis 102 Face d 110 P optical system input first shot system DOF1 Depth of field of the first camera system F1 Image plane of the first camera system 112 First camera system 116 Optical path of the first camera system 120 Second system F2 Focal plane image of the second camera system DOF2 Depth of field of the second camera system 122 Second image acquisition system 126 Optical path of the second camera system 128 Optical module with system Catoptric Optics 129 Mirror 130 Third Shooting System 140 Light Source (Side Illumination) 300 Machining Module 310 Tool Holder (First Object) 312 Tool 314 X Mark on Toolholder 316 Y Mark on Door tool 320 Workpiece support or material spindle (second object) 322 Workpiece (material)

Claims (31)

claims An optical system (100) for three-dimensional measurement of the relative position between a first object and a second object on which said optical system (100) is to be mounted, said optical system (100) comprising a first optical pickup system (100). view (110) and a second camera system (120), wherein: - the depth of field (DOF1) of the first camera system (110) is at least ten times greater than the depth of field (DOF2 ) of the second camera system (120), and - the optical system (100) is arranged such that the optical path of the first camera system (110) and the optical path of the second camera system ( 120) have a common section comprising the image focal plane of the first camera system (110) and the image focal plane of the second camera system (120). An optical system (100) according to claim 1, wherein the optical system (100) is arranged such that the optical path from the object passes through at least a portion of one of the first and second grip systems. from the viewpoint (110; 120) before reaching the other one of the first and second image systems (110; 120). An optical system (100) according to claim 1 or 2, wherein the first and second camera systems (110; 120) are arranged in parallel with each other and in that the system optical system (100) further comprises an optical module disposed between the first and second imaging systems (110; 120) and configured to deflect a portion of the light rays passing through at least a portion of one of the first and the second second camera system (110; 120) to the other one of the first and second camera systems (110; 120). An optical system (100) according to any one of claims 1 to 3, wherein the focal length of the second camera system (120) is larger than the focal length of the first camera system (110). . An optical system (100) according to any one of claims 1 to 4, wherein the magnification of the first camera system (110) is less than or equal to the magnification of the second camera system (120). An optical system (100) according to any one of claims 1 to 6, wherein the depth of field (DOF1) of the first camera system (110) is greater than or equal to 0.8 millimeters. An optical system (100) according to any one of claims 1 to 7, wherein the depth of field (DOF2) of the second camera system (120) is less than or equal to 0.1 millimeters. An optical system (100) according to any one of claims 1 to 8, wherein the first camera system (110) is telecentric and the second camera system (120) is telecentric. 9. Optical device (10) for measuring three-dimensional measurement for the relative position between a first object and a second object, comprising an optical system (100) according to any one of claims 1 to 8 to be mounted on said second object, and a three-dimensional target (200) intended to be placed on said first object and to serve as positioning reference, said three-dimensional target (200) comprising on a useful face (202): a first structure (210) defining a face reference plane (212), and * a second structure (220) having an inclined face (222) with respect to said reference plane face (212), wherein the difference between the focal length of the second image system ( 120) and the focal length of the first camera system (110) is between the minimum distance and the maximum distance separating the reference face (212) from the inclined surface (222). An optical device (10) according to claim 9, wherein said planar reference face (212) is distributed between at least: a first portion (214) whose surface is reflective according to first reflection parameters, and - a second portion (216) whose surface is reflective according to second reflection parameters different from the first reflection parameters. An optical device (10) according to claim 10, wherein the surface of said first portion (214) of which is reflective in a diffuse reflection, and the surface of said second portion (216) is reflective in specular reflection, The optical device (10) of claim 10 or 11, wherein said second portion (216) is distributed in a series of localized areas (217) positioned in the first portion (214). 13. An optical device (10) according to any one of claims 9 to 12, wherein the surface of said inclined face (222) has raised elements (224) or specular elements (225) regularly distributed. 14. An optical device (10) according to any one of claims 9 to 13, wherein said localized zones (217) define between them a geometrical figure belonging to the following list: quadrilateral, parallelogram, rectangle, square, rhombus, regular polygon and circle. The optical device (10) of claim 12, wherein said localized areas (217) of said second portion (216) are formed of islands or segments distributed in the first portion (214). An optical device (10) according to any one of claims 9 to 15, wherein said localized areas (217) are chromium. An optical device (10) according to any one of claims 9 to 16, wherein the first structure (210) and the second structure (220) are arranged on the useful face (202) concentrically with respect to each other. to the other. The optical device (10) of claim 9 or 17, wherein the first structure (210) surrounds the second structure (220). The optical device (10) of claim 12, wherein the localized areas (217) of the second portion (216) of the first structure (210) define a square surrounding the second structure (220). 20. Optical device (10) according to any one of claims 9 to 19, wherein the first structure (210) defines an opening (218) for a housing (219) housing said second structure (220) 21. Optical device (10) according to the preceding claim, wherein the second structure (220) is disposed in said housing (219) with the inclined face (222) which is set back relative to the reference face (212) of said first structure (210). An optical device (10) according to any of claims 9 to 20, wherein the surface of the inclined face (222) of the second structure (220) is ridged, in particular the surface of the inclined face (222). (222) of the second structure (220) is covered by one of the following: an etched network, structured grid or specular line network (225). An optical device (10) according to any one of claims 9 to 21, wherein said target (200) further comprising a plate of a transparent material, in particular glass, covering the first structure (210) and the second structure (220) on the side of the usable face (202). 24. The optical measuring device (10) of three-dimensional measurement according to one of claims 9 to 22, further comprising a light source (140) oriented towards the target (200) three-dimensional, said light source (140) being arranged to provide lateral illumination of the three-dimensional target (200). 25. Arrangement for three-dimensional optical measurement of the relative position between a first object and a second object, comprising: - an installation comprising a first object and a second object, - an optical measurement device (10) according to one of the claims 9 to 23 wherein; the first camera system (110) is configured so that its image focal plane is able to correspond to the reference face (212) of the first structure (210), and the second camera system (210); 120) is configured so that its image focal plane is able to be intersecting with the inclined face (222) of the three-dimensional target (200). 26. Arrangement according to the preceding claim wherein said installation is a machining module, the first object is a tool holder (310) and said second object is a material support or part support (320). 27. Three-dimensional optical measurement method according to three orthogonal directions X, Y and Z, between a first object and a second object aligned and spaced from each other in the main direction Z, in which: a target is provided ( 200) comprising a useful face (202) forming a positioning reference, and comprising; a first structure defining a planar reference face distributed between at least: a first portion whose surface is reflective according to first reflection parameters; surface is reflective according to second reflection parameters different from the first reflection parameters, and * a second structure (220) having an inclined face (222) with respect to said reference plane face - there is provided an optical system (100) comprising a first camera system (110) and a second camera system (120), wherein: - the depth of field (DOF1) of the first camera system (110) is at least 10 times greater than the depth of field (DOF2) of the second camera system (120), and - said optical system (100) is arranged on the one hand so that the optical path of the first camera system (110) and the path optics second camera system (120) has a common section comprising the image focal plane of the first camera system (110) and the image focal plane of the second camera system (120), and secondly so that the difference between the focal length of the second camera system (120) and the focal length of the first camera system (110) is between the minimum distance and the maximum distance separating the reference face (212). ) of the inclined face (222), - said three-dimensional target (200) is positioned on the first object so that on the one hand the focal length of the first camera system (110) is able to place the image focus of first image system (110) on the first structure (210) of the target (200) and secondly the focal length of the second image system (120) is adapted to place the focus image of the second shooting system (120) on the second structure e (220) of the target (200), - said optical system (100) is positioned on the second object, - at least one image is simultaneously taken with the first image system (110) of the optical system ( 100) and with the second image system (120) of the optical system (100), whereby, for each shot by the optical system (100), on the one hand the first image system ( 110) generates a first image of the target (200) for identifying on the reference face (212) the position of the second portion (216) with respect to the first portion (214), thereby giving a first first information on the relative position in the X direction of the target (200) relative to the first camera system (110) and secondly a second information on the relative position between the target (200) and the first camera system. image (110) in the Y direction, and secondly the second image capture system. view (120) generates a second image of the target (200) comprising a net portion corresponding to a location of the inclined face (222) of the second structure (220), thereby providing a third information on the distance between said target ( 200) and said second camera (120) in the Z direction. 28. Measuring method according to claim 27, wherein, after positioning the three-dimensional target (200) on the first object and positioning the optical system (100) on the second object, an additional step of spatial referencing of the X, Y, and Z position of the target (200) relative to the first object by the optical system (100). 29. Measuring method according to claim 27 or 28, wherein said second portion (216) of the planar reference face (212) is distributed according to a series of localized zones (217) positioned in the first portion (214) and in wherein the first image generated by the first camera system (110) identifies the location of the localized areas (217) of the second portion (216) on the reference face (212), thereby providing information about the relative position between said localized zones (217) and the first camera system (110) making it possible to deduce the relative measurement in the Y direction and in the X direction. Measuring method according to claim 27, 28 or 29, for the three-dimensional measurement of a machine tool of the relative position between a tool holder (310) and a work support (320), in wherein said first object is said tool holder (310) and said second object is said workpiece carrier (320), wherein an additional step is performed prior to said simultaneous shooting step with said optical system (100), according to which: - the tool holder (310) and the work support (320) are arranged aligned in the main direction Z so that the useful face (202) of said three-dimensional target (200) is in the optical path of the system optical (100). 31. Measuring method according to the preceding claim, wherein the optical device (10) further comprises a third camera arranged on the tool holder (310) and configured to locate the orientation of the useful face (202). ) of the target (200) and / or the angular orientation of the tool holder (310).