JP4662018B2 - Curved surface processing apparatus and parallel link mechanism calibration method - Google Patents

Description

  The present invention relates to an optical element such as a free-form surface lens applied as an fθ lens of a laser beam printer and a digital copying machine or a curved surface processing apparatus for forming a mold thereof.

  An aspherical surface or a free-form surface is adopted for the fθ lens used in the writing system of the laser printer. In order to mass-produce fθ lenses at low cost, a lens manufacturing method using an injection molding method has been developed. In the lens molding process by injection molding, since the shape accuracy of the insert piece for forming the optical surface directly affects the performance of the resin lens, the insert piece is required to have a very high shape accuracy on the order of submicrons.

  Usually, the insert of the optical element is manufactured by diamond cutting in the form of fly cutting, but in order to further improve the shape accuracy of the insert, a small diameter polishing tool is applied only to a very small part, and the shape error is controlled by residence time control. Many methods have been devised to improve the accuracy by correcting the above.

  As polishing tools, those that supply abrasive grains to rotary tools and fixed abrasive tools that contain abrasive grains have been used conventionally, but recently, an abrasive jet that uses magnetic fluid to act on the abrasive grains. Such a method has also been devised.

  In any method, it is assumed that the shape correction is performed by the residence time control, and the removal volume per unit time (hereinafter referred to as removal efficiency) is constant.

  If the removal efficiency changes at the machining position, it leads to an increase in machining error. Therefore, it is necessary to suppress the change as much as possible.

  For example, in the case of polishing processing that removes by load transfer, the tilt angle is controlled so that the polishing load direction always matches the normal line at the processing point in order to reduce the influence of the tilt of the surface to be processed. . Assuming that the plane perpendicular to the optical axis of the optical surface of the fθ lens is 0 degree, a maximum of about 50 degrees has been put into practical use, and attitude control of the tilt angle is essential for ensuring accuracy.

  Even in ferrofluid polishing and abrasive jet machining, the removal volume is stabilized and machining accuracy is improved by keeping the angle formed by the nozzle injection direction and the normal at the machining point constant.

  In order to perform tool scanning and tilt angle attitude control, a 5-axis control (linear orthogonal 3 axes and rotation 2 axes) positioning mechanism has been conventionally used. In addition, when the positioning axis in the polishing load direction is not required, a positioning mechanism of four-axis control (linearly orthogonal two axes and rotating two axes around each axis) was used.

  Patent Document 1 discloses an inclination mechanism that is frequently used in a general-purpose machining center. In addition to this, in consideration of the fact that the inclination of the optical surface of the fθ lens is large in the main scanning direction and small in the sub-scanning direction, a patent for reducing the space of the apparatus by combining a rotary stage and a gonio stage. A configuration as in Document 2 is also disclosed.

FIG. 8 shows a configuration that uses a gonio stage by limiting the angle range in the sub-scanning direction. The apparatus includes a fixed base 101, a cantilever support member 102, a direct drive motor 103 with roller bearings, a swinger 104, a sub swinger (gonio stage) 106, a magnet head 107, and a swing angle restriction sensor 108.
The cantilever support member 102 is fixedly installed on the fixed base 101. The direct drive motor 103 with a roller bearing is attached to the cantilever support member 102 such that the rotation shaft (output shaft) is in the horizontal direction, and swings the swing member. The swinger 104 is a swinging member that is swingably fixed to the end of the rotary shaft of the direct drive motor 103 with a roller bearing. The swing angle restriction sensor 108 is a sensor for restricting the swing angle of the swinger 104. The swinger 104 includes a swinger base 105, a sub swinger 106 fixed on the swinger base 105, and a magnet head 107 for magnetically attracting a member to be polished. The sub swinger 106 has a swing center axis in a plane perpendicular to the swing center axis J of the swinger 104 and parallel to the swing base 105, and is arranged so as to swing in the direction orthogonal to the swinger 4.

  Even in this configuration, the apparatus dimensions are not sufficiently small relative to the dimensions of the workpiece. In particular, since the weight of the oscillating device alone exceeds 20 to 30 kg, an increase in the size of the orthogonal three-axis linear motion mechanism is unavoidable for high-speed driving. In addition, in order to perform shape creation polishing with dwell time control, it is necessary to perform rapid acceleration / deceleration at the same time on 4 or 5 axes, a motor with high output on each axis, and a control mechanism that controls these with high speed and high accuracy. Is required.

  The polishing process itself is performed at a lower transfer pressure than cutting, and therefore it does not necessarily require device rigidity compared to the cutting device, but the actual polishing processing device is due to the above causes. It is a device that is as large and expensive as a device that performs heavy cutting of large workpieces.

  The machine tool is also downsized by using a parallel link mechanism.

  A machine tool having a parallel link mechanism is disclosed in Patent Literature 3 and Patent Literature 4.

  Although the invention disclosed in Patent Document 3 and Patent Document 4 is configured to control the movement of the tool spindle, these machine tools have insufficient motion accuracy and cannot be used for high-precision machining applications. is the current situation.

  In the case of the parallel link mechanism, the tool position in the XYZ coordinate system is indirectly estimated from the rotation angle of the straddle telescopic motor. Therefore, in order to perform highly accurate positioning, it is necessary to accurately identify mechanical parameters such as the length of the straddle and the position of the joint. However, it is difficult to accurately specify the position of the tool or the position of the tip of the spindle in an arbitrary space, and the identification accuracy of the parameters naturally follows this measurement accuracy. For this reason, in a processing machine using a parallel link mechanism, positioning accuracy has been limited to several tens to several hundreds of μm.

As a method for improving the positioning accuracy of the parallel link mechanism, there is a method disclosed in Non-Patent Document 1. This method is a method using a so-called double ball bar (DBB) method in which two spheres are connected by an extendable bar and the amount of expansion / contraction is taken.
JP 10-175150 A JP 2002-0779449 A JP-A-9-001491 Japanese Patent Laid-Open No. 9-019842 Journal of Precision Engineering, No. 2,2003 "Study on configuration of 3D coordinate measuring machine using parallel mechanism"

  However, even if this method is used, the actual moving part tip (touch probe) is accompanied by a rotational motion of 3 degrees of freedom around each axis of XYZ in addition to the translational motion. Therefore, it is impossible to obtain an accuracy that can be applied to processing an optical element and its mold.

  As described above, the conventional polishing apparatus has a problem that the apparatus becomes large when the apparatus rigidity required for the shape creation polishing is ensured.

The present invention has been made in view of such problems, and an object of the present invention is to provide a curved surface processing apparatus having a rigidity necessary for shape creation processing and having a smaller and lighter configuration than the conventional one and a calibration method thereof.

In order to achieve the above object, as a first aspect of the present invention, a work table on which a workpiece is placed and a base plate are connected by a plurality of extendable rod-like members, and the rod-like member is expanded and contracted and swung. A curved surface processing apparatus equipped with a parallel link mechanism for controlling the position and inclination of a work table, wherein the workpiece is maintained so that the normal formed at the contact point of the workpiece with the processing tool and the angle made by the processing tool are kept constant. Means for controlling the scanning and tilting posture of the workpiece by movement only on the table side, a processing tool that is elastic in a spherical or barrel shape and that is elastically deformed during processing and presses against the workpiece in a small area, and the workpiece Means for maintaining a constant contact pressure with the work piece, and means for adjusting the amount of work on the work piece by controlling the scanning speed of the work tool. The work tool is mainly composed of a resin material. A porous structure, the abrasive grains of the abrasive is to provide a curved surface machining apparatus characterized by scanning with externally supplied during processing. By doing so, it is possible to realize a lightweight, space-saving and inexpensive curved surface processing apparatus. Since the mass of the movable part is small, it has low inertia and can be processed at a higher speed than before while performing angular attitude control.

In order to achieve the above object, as a second aspect of the present invention, a work table on which a workpiece is placed and a base plate are connected by a plurality of extendable rod-like members, and the rod-like members are expanded and contracted. A curved surface processing device equipped with a parallel link mechanism that controls the position and tilt of the work table by turning, further comprising a rotary table for rotating the workpiece on the upper surface of the work table, and processing while rotating the workpiece. Means for scanning the tool and controlling the inclination posture of the workpiece by movement only on the work table side so as to keep a constant angle between the normal line at the contact point of the workpiece with the machining tool and the machining tool; A processing tool that is elastic in the shape of a sphere or barrel and that is elastically deformed during processing and presses against the workpiece in a minute area, and means for maintaining a constant contact pressure between the workpiece and the processing tool Means for adjusting the processing amount for the workpiece by controlling the scanning speed, and the processing tool has a porous structure mainly composed of a resin material, and abrasive grains as an abrasive during processing The present invention provides a curved surface processing apparatus characterized by scanning while being supplied from the outside. By doing so, it is possible to realize a lightweight, space-saving and inexpensive curved surface processing apparatus. Since the mass of the movable part is small, it has low inertia and can be processed at a higher speed than before while performing angular attitude control. Furthermore, an axisymmetric curved surface can be easily processed at high speed and high accuracy.

In the first aspect or the second aspect of the present invention described above, the contact pressure between the work tool and the work piece that is spherical or barrel-shaped and has elasticity and is elastically deformed at the time of machining and press-contacts the work piece with a small area. It is preferable to adjust the machining amount for the workpiece by keeping the constant and controlling the scanning speed of the machining tool. By causing the small-diameter tool to act in a point contact state, undulations and ripple components having a wavelength of several millimeters can be dynamically removed by residence time control. Thereby, since it is not necessary to make the tool act on a large area as in the conventional machine and use the viscosity and elasticity for averaging, the machining efficiency and accuracy can be improved.
In addition to this, it is more preferable that the processing tool has a porous structure mainly composed of a resin material, and the abrasive grains as the abrasive are supplied from the outside during processing. As a result, it is possible to suppress “lifting of the tool” in the polishing in the horizontal axis posture and maintain stable machining accuracy for a long time.

  Alternatively, in the first aspect or the second aspect of the present invention, the processing tool is polished in a binder mainly composed of any of urethane, chloroprene rubber, phenol resin, epoxy resin, ABS resin, and melanin resin. It is a resin grindstone containing abrasive grains as a material, and it is preferable that the amount of cut into the workpiece is given by being urged to the workpiece. In this way, it is possible to increase the abrasive grain size and tool peripheral speed while ensuring surface quality even for hard brittle materials such as glass and ceramic, which have low efficiency in polishing of “point contact + loose abrasive”. Thus, the machining efficiency is improved.

Alternatively, in the first aspect or the second aspect of the present invention, the processing tool is a nozzle that ejects a fluid containing abrasive grains as an abrasive, and the abrasive grains collide with the surface of the workpiece and It is preferable to remove the processed surface layer of the workpiece. In this way, since tool wear and changes over time do not become a problem, high-precision machining is possible even for large-area workpieces that require long-time machining.
In addition to this, it is more preferable to change the removal depth of the processed surface of the workpiece by changing the scanning speed of the processing tool.

  Alternatively, in the first aspect or the second aspect of the present invention, the processing tool is a single crystal diamond tool, and a normal line at a contact point of the workpiece with the processing tool and a cutting direction of the processing tool are determined. It is preferable to match. In this way, an apparatus capable of easily forming a diffraction pattern on a curved surface can be realized at low cost with light weight and space saving. In addition, since the mass of the drive unit is small and low inertia compared to the conventional machine, the work table can be moved at high speed, and the processing efficiency can be improved.

  Alternatively, in the first aspect or the second aspect of the present invention, the processing tool is a single crystal diamond tool, and has a rotational positioning mechanism that can rotate around an axis in a cutting direction, and It is preferable that the normal line at the contact point with the machining tool coincides with the cutting direction of the machining tool, and the angle formed by the scanning direction of the machining tool and the rake face of the machining tool is controlled by a rotary positioning mechanism. In this way, an apparatus capable of easily forming a diffraction pattern on a curved surface can be realized at low cost with light weight and space saving. In addition, since the mass of the drive unit is small and low inertia compared to the conventional machine, the work table can be moved at high speed, and the processing efficiency can be improved. In addition, the posture control that matches the cutting direction with the normal at the workpiece machining point and the rake face angle control that controls the angle θ made by the rake face can be performed separately on the work table side and the tool head side. In addition to being able to derive control commands separately, each control can be performed with a simple procedure.

Moreover, in order to achieve the said objective, this invention is a 3rd aspect. The calibration method of the parallel link mechanism in the curved surface processing apparatus concerning the structure in any one of the said 1st aspect or the said 2nd aspect of the said invention A spherical sensor is clamped on the work table, a displacement sensor for detecting the displacement of the work table with respect to the base plate , and a collimator for detecting the inclination of the surface of the spherical master are arranged, and the optical axis of the collimator is spherical. while maintaining the posture perpendicular to the standard surface by operating the work table so as to scan relative to the spherical standard surface, the optical axis of the spherical standard surface that is synchronized with the actual displacement and said actual displacement of the work table parallel to respect acquires inclination data, and identifying the position control parameters of the parallel link mechanism on the basis of the value of the actual displacement and the inclination data There is provided a calibration method of link mechanisms. In this way, it is possible to accurately identify the actual dimensions and positions of the components that connect the parallel link drive source to the work table that is the output end. Therefore, the positioning accuracy can be dramatically increased as compared with the conventional machine.

  According to the present invention, it is possible to provide a curved surface processing apparatus having a rigidity necessary for shape creation processing and having a smaller and lighter configuration than the conventional one, a calibration method thereof, an optical element and an optical element mold manufactured by the apparatus.

[Features of the invention]
Since the nesting piece for forming the optical surface is small and lightweight as a molding die, the parallel link mechanism is used as a work table moving mechanism in the present invention. The configuration is such that the tilt posture is controlled. As a structure for moving the workpiece, a parallel link mechanism in which a base plate and a work table for fixing the workpiece are connected by a plurality of extendable straddles is used, and this is connected to a polishing head having a load control mechanism. The configuration.

  In addition, in order to accurately identify the mechanical parameters of the parallel link, positioning accuracy is improved by providing means for accurately obtaining the movement amount of the work stage by separating it into a parallel movement component and a rotation movement component. .

  By adopting such a configuration, an optical element processing apparatus using a parallel link mechanism, which was difficult to implement in the past, was realized.

  In addition, by performing the movement of the workpiece itself by a combination of three orthogonal axes and two rotation axes, it is possible to move the workpiece with an acceleration twice or more that of the conventional machine. For example, the upper limit of the feed rate when used as a polishing machine is 300 mm / min in the conventional machine, but can be increased to 1000 mm / min in the present invention.

  Furthermore, in the conventional machine, the maximum scanning speed of the tool within a range in which the apparatus vibration does not occur is obtained, and NC data for dwell time control is generated on the assumption of this, but in the present invention, the maximum tool scanning is performed. Since the speed can be set to double, the scanning speed in the residence time control can be increased as a whole, and the polishing time can be greatly shortened compared with the conventional machine.

  Furthermore, in the present invention, the tool can be brought into contact with an arbitrary inclination in accordance with the processing point normal line without an extra translational motion.

  In conventional machines, the size of the device has been increased in order to provide a sufficient margin for the slide stroke, but in the present invention, such waste can be eliminated, and the effect of the link mechanism is combined with a significant reduction in size compared to conventional processing devices. It is possible to reduce the cost and space.

  A preferred embodiment of the present invention having such characteristics will be described below.

[First Embodiment]
A first embodiment in which the present invention is suitably implemented will be described. FIG. 1 shows a state where the mold of the fθ lens is being polished. The polishing tool 1 has a tire shape and is pressed against the fθ lens mold 2 by a polishing load (0.98 N) generated in the Z-axis direction by a pressure mechanism (not shown). The polishing tool 1 is rotationally driven by a motor (not shown), scanned in the Y direction perpendicular to the paper surface, moved by a small amount in the X direction in the vicinity of the outer edge of the fθ lens mold 2, and scanned in the Y direction again. By repeating the above, the entire processing surface is scanned. The polishing tool 1 is made of wood powder hardened with a resin, and has a contact area of about φ0.8 by causing elastic deformation at a processing point. Since the polishing tool 1 itself does not include abrasive grains that serve as an abrasive, a 1/4 μm diameter diamond paste is applied to the surface to be processed of the fθ lens mold 2 with a uniform thickness. Abrasive grains are supplied while being gradually engulfed by rotation and scanning.

  FIG. 3 shows the configuration of the polishing tool and its pressing mechanism. A spindle motor 15 that drives the polishing tool 1 is fixed to the movable block 11. The movable block 11 is movable in the Z-axis direction along the static air pressure slide 12, and the amount of movement in the Z-axis direction is visible by the linear scale 14.

In order to always make the normal at the processing point coincide with the Z-axis which is the polishing load direction, the tilting posture of the work table 34 is controlled by the expansion / contraction operation of the straddle 31, thereby controlling the tilting posture of the fθ lens mold 2. The Here, a configuration with six straddles is taken as an example, but this number is arbitrary. Each straddle 31 is fixed to the processing machine bed 37 and the work table 34 by a base side universal joint 32 and a work table side universal joint 33 , respectively.

  The expansion / contraction operation of the straddle 31 is generated by combining the parallel movement of the workpiece so as to generate the above-described tool scanning trajectory.

  The tool scanning speed is accelerated and decelerated for shape creation, and the dwell time is controlled.

  In the conventional machine, the upper limit of the tool scanning speed of 200 mm / min is used as the normal range, but in the present embodiment, the upper limit of the tool scanning speed with tilt control is increased to 400 mm / min. This makes it possible to shift the processing condition of 0.3 to 1.2 sec / mm (F200 to 50) to the condition of 0.15 to 1.05 sec / mm (F400 to 57) in the dwell time control NC data. Since the machining time is shortened by 0.15 sec per 1 mm of tool scanning, the machining time can be shortened by about 50 minutes when machining an fθ lens mold with a scanning distance of about 2000 mm.

  As described above, the curved surface processing apparatus according to the present embodiment has an effect of shortening the processing time in addition to the advantages of space saving and cost reduction.

[Second Embodiment]
A second embodiment in which the present invention is suitably implemented will be described. FIG. 2 shows a configuration of the curved surface processing apparatus according to the present embodiment. The curved surface processing apparatus according to the present embodiment is configured so as to be able to polish a coaxial aspherical surface that is axially symmetric.

  Here, as in the first embodiment, a configuration including six straddles 31 is taken as an example. The basic configuration is the same as that of the curved surface processing apparatus according to the first embodiment, but in this embodiment, a turntable 35 is further provided on the work table 34. The load cell 16 (not shown in FIG. 1) is an apparatus for applying a polishing load to the polishing tool.

  The shape error of the coaxial aspheric surface can be classified into an error amount such as a curvature error itself having an axis target component and an asphalt component that is not.

  By correcting the rotationally symmetric component using the turntable 35, the dwell time control NC data can be greatly simplified compared to the raster scan type in the case of the fθ lens, and the mechanical movement for the tool scan is less. Therefore, processing accuracy can be improved.

[Third Embodiment]
A third embodiment in which the present invention is preferably implemented will be described. The curved surface processing apparatus according to this embodiment shown in FIG. 4 is obtained by replacing the portion of the polishing tool 1 in the second embodiment with a high-speed injection nozzle 41 that injects abrasive grains at high speed.

  As the abrasive grains, alumina or SiC having a particle diameter of about several μm to submicron is used. The abrasive grains are supplied from the abrasive grain supply path 43 by the carrier air flow, and the high-pressure air for injection is supplied from the high-pressure air supply path 44. The abrasive grains and the high-pressure air are jetted as a mixed fluid 42 from the high-speed jet nozzle 41 onto the processing surface of the coaxial aspherical lens mold 22 that is a workpiece.

  At this time, the surface layer of the processed surface of the workpiece is removed by the collision energy of the abrasive grains. The processing depth is the same as in the case of polishing, and has a characteristic proportional to the residence time of the tool. For this reason, as in the above embodiment, highly accurate shape creation is possible by controlling the residence time.

  In addition, since the abrasive grains easily scatter due to the processing method, a dust-proof cover 36 that prevents the abrasive grains from entering is provided at the sliding portion of the processing apparatus.

  By rotating the coaxial aspherical lens mold 22 while making the direction of the high-speed injection nozzle 41 coincide with the processing point normal line and scanning from the outer periphery toward the center, the processing of the coaxial aspherical lens mold 22 is performed. The entire surface can be processed.

[Fourth Embodiment]
A fourth embodiment in which the present invention is preferably implemented will be described. FIG. 5 shows a configuration of the curved surface processing apparatus according to the present embodiment.
The curved surface processing apparatus according to the present embodiment has a configuration in which the portion of the polishing tool 1 in the second embodiment is replaced with a single crystal diamond tool 51. The diamond tool 51 is rotationally driven and positioned by the rotation control mechanism 52.

  While rotating the coaxial aspherical lens mold 22, concentric grooves are formed on the surface by cutting with a single crystal diamond tool 51. The single crystal diamond tool 51 has a sword tip shape, the roundness of the tip is R = 1 μm or less, and the tip angle is 91 °. Further, the cutting direction is the Z-axis direction in FIG. 5, and the single crystal diamond tool 51 is scanned from the outer periphery to the center of the coaxial aspheric lens mold 22 as in the above embodiments. To process the entire processing surface.

  When scanning with the tool kept in contact, a spiral groove is formed, so after cutting at a fixed position, the tool is once separated from the work, and moved slightly in the rotational radius direction of the coaxial aspherical lens mold 22, By repeating the cutting operation with the bottom as a fixed position, concentric grooves are formed on the curved surface.

  The angle formed between the normal line at the contact point of the tool and the Z axis that is the cutting direction can be arbitrarily set, and can be maintained at a constant angle or can be changed in accordance with the turning radius.

  FIG. 6 shows a state in which a concentric V-shaped groove 22 a is formed on the surface of the coaxial aspheric lens mold 22.

  FIG. 7 shows means for finishing the V-groove opening angle with high accuracy. The single crystal diamond bit 51 forms a tool path 55 with respect to the workpiece surface by the rotation of the workpiece. In such a circular or curved trajectory, the traveling direction of the tool at an arbitrary position is equal to the tangent to the trajectory of the tool. In FIG. 7, when the angle formed between the tangent line 53 of the tool trajectory and the rake face is θ, when θ = 90 °, the tip angle α0 of the diamond bit 51 acts on the workpiece with the same size as it is. It becomes.

  FIG. 9 shows a calibration operation for identifying a parallel link mechanism control parameter. The control parameter corresponds to the actual length of the straddle 31 or the actual joint position (base-side universal joint 32 and worktable-side universal joint 33), and connects the parallel link drive source to the worktable 34 that is the output end. It refers to the actual dimensions and position of the components. If this can be accurately identified as it is, it is possible to dramatically increase the positioning accuracy, which has conventionally been limited to about 10 microns.

  Here, the case of applying to the frame of the curved surface processing apparatus according to the third embodiment or the fourth embodiment has been described, but by arranging the autocollimator 61, the curved surface processing apparatus according to the second embodiment is arranged. It can also be applied to frames.

  The autocollimator 61. The optical axis is attached to the column 87 so as to be parallel to the Z axis. The optical axis of the objective lens 62 of the autocollimator is in a positional relationship that substantially coincides with the center lines of the high-speed injection nozzle 41 and the diamond bit 51 in the third and fourth embodiments.

  An intersection point of the extension line of the optical axis and the surface to be processed is P, and a normal vector n at the point P is illustrated. The spherical base 64 clamped on the work table 34 is made of glass, has a radius of curvature of 100 mm, and a diameter of φ80 mm. As the spherical original device 64, the one that is as close as possible to the approximate radius of curvature of the actual workpiece is used.

The double ball bar 67 is a sensor for detecting a relative displacement of the work table 34 with respect to the processing machine bed 38. This sensor detects a parallel movement component that does not include the tilt of the work table 34. The positional relationship between the center of curvature of the moving sphere of the double ball bar 67 (point Q in FIG. 9) and the spherical base 64 is accurately acquired in advance by a three-dimensional measuring machine. From this position information, ω _th and L _th are respectively theoretical values of the phase angle ω and the expansion / contraction length L of the double ball bar 67 when the normal vector n63 at the point P coincides with the optical axis. Can do. Here, the phase angle ω is a line segment OQ connecting the center of the moving sphere on the processing machine bed 37 side (point O in FIG. 9) and the center of the moving sphere on the work table 34 side (point Q) XY. This is the angle formed by the line projected on the plane and the X axis.

  With the parameters of the current parallel link mechanism, the autocollimator spot is scanned so as to cover the entire processing region, and ω and L at each position are acquired from the double ball bar 67. Since the autocollimator 61 is set so that its optical axis is orthogonal to the XY plane, it can acquire the angular orientation errors β and γ. γ is an angle formed by the optical axis of the autocollimator 61 and a normal line at a point P on the optical axis, and γ indicates the phase angle. The phase angle γ is an angle formed by a line obtained by projecting the normal vector n63 on the XY plane and the X axis, as in the previous ω.

  FIG. 10 shows the positional relationship between the phase angles. Since the optical axis of the autocollimator 61 and the Z axis are parallel, the Z axis can be regarded as the optical axis.

  Deviation amounts Δω and ΔL are obtained from the actual measurement value and theoretical value of the phase angle ω and the expansion / contraction length L, and the parallel link mechanism parameters are set so that the four error components β, γ, Δω, and ΔL are as small as possible in the entire evaluation range. Is identified. In this work, if an analytical expression is derived from the link structure, the optimum parameter can be automatically obtained without manpower by a convergence calculation using an electronic computer.

  Since the analytical expression itself is separated into Δω and ΔL indicating the parallel movement component and β and γ indicating the rotation posture component, it can be configured more simply, and the amount of calculation in the convergence calculation can be suppressed to a relatively small amount. .

FIG. 11 shows a processing method for forming a concentric blazed pattern as shown in FIG. 6 on a concave curved surface. It is common to cut with a sword-shaped diamond tool and rotate the work surface to rotate. Although a V-groove cutting tool is used here, it is difficult to make it into the target tip angle without error in actually producing a diamond tool. For this reason, it is necessary to correct the tool tip angle error. In FIG. 11, when the angle formed by the rake face is θ = 90 °, the opening angle of the formed V groove is α0. When the angle of θ is decreased or increased and moved away from 90 °, the tool tip angle acts as small as α0 → α1.
A V-groove having a more accurate opening angle can be formed by manufacturing a tool with a large tool tip angle in advance and adjusting θ during processing.

  In the present embodiment, the rotational positioning mechanism 52 can accurately control θ according to the tool trajectory. For this reason, by simultaneously controlling the tool scanning and θ, the opening angle of the V-groove can be accurately formed with an error of several seconds in not only concentric circles but also any other curved groove machining.

Each of the above embodiments is an example of a preferred embodiment of the present invention, and the present invention is not limited to these.
For example, in each of the above embodiments, a rotary tool or a diamond tool is used as an example of a processing tool. However, the present invention can also be applied to apparatuses using other processing tools.
As described above, the present invention can be variously modified.

  INDUSTRIAL APPLICABILITY The present invention can be applied to all polishing methods that traverse a polishing tool having a small diameter with respect to a processing surface and correct a shape error of the processing surface. By applying it to a flat and curved optical element and its shape correction processing or cutting tool, processing of a diffraction pattern having a curved surface, processing of a Fresnel lens, and the like can be easily performed.

It is a figure which shows the structure of the curved surface processing apparatus concerning 1st Embodiment which implemented this invention suitably. It is a figure which shows the structure of the curved surface processing apparatus concerning 2nd Embodiment which implemented this invention suitably. It is a figure which shows the structure of a pressurization mechanism. It is a figure which shows the structure of the curved surface processing apparatus concerning 3rd Embodiment which implemented this invention suitably. It is a figure which shows the structure of the curved surface processing apparatus concerning 4th Embodiment which implemented this invention suitably. It is a figure which shows the external appearance of a coaxial aspherical lens metal mold | die. It is a figure which shows the relationship between a motion of a tool, and a processing surface. It is a figure which shows the structure of the curved surface processing apparatus using a gonio stage. It is a figure which shows the calibration operation | movement for parallel link mechanism control parameter identification. It is a figure showing the relationship between the normal vector of a process surface, and a phase angle. It is a figure which shows the motion of the tool in the case of forming a blaze pattern on a curved surface.

Explanation of symbols

1 Polishing tool 2 fθ lens mold (nesting)
DESCRIPTION OF SYMBOLS 11 Movable block 12 Air static pressure slide 13 Air cylinder for polishing load control 14 Linear scale 15 Spindle motor 16 Load cell 22 Coaxial aspherical lens mold (nesting)
31 Strud 32 Base side universal joint 33 Work base side universal joint 34 Work table 35 Turntable 36 Dust cover 37 Processing machine bed 41 High speed spray nozzle 42 Abrasive grain 43 Abrasive grain supply path 44 High pressure air supply path 51 Diamond bit 51a Byte scoop Surface 52 Rotational positioning mechanism 53 Tool path tangent line 55 Tool path 61 Autocollimator 62 Autocollimator objective lens 63 Normal vector at point P 64 Spherical base 65 Spherical seat of moving sphere 66 Moving sphere 67 Telescopic bar 68 Fixed sphere 69 Fixed Spherical surface seat of ball 101 Fixed base 102 Cantilever support member 103 Direct drive motor with roller bearing 104 Swinger 106 Sub swinger (gonio stage)
107 Magnet bed 108 Oscillating angle regulating sensor 110

Claims (3)

A work table on which a workpiece is placed and a base plate are connected by a plurality of extendable rod-like members, and a parallel link mechanism is provided that controls the position and inclination of the work table by extending and retracting and turning the rod-like members. A curved surface processing apparatus,
Means for controlling the scanning and tilting posture of the workpiece by movement only on the worktable side so as to keep a constant angle between the normal line at the contact point of the workpiece with the machining tool and the machining tool;
Means for maintaining a constant contact pressure between the work tool and the work tool that presses against the work piece in a small area by causing elastic deformation at the time of machining with elasticity in a spherical or barrel shape;
Means for adjusting a machining amount for the workpiece by controlling a scanning speed of the machining tool;
Have
The processing tool has a porous structure having a resin material as a main component, and abrasive grains as an abrasive are scanned while being supplied from the outside during processing. A work table on which a workpiece is placed and a base plate are connected by a plurality of extendable rod-like members, and a parallel link mechanism is provided that controls the position and inclination of the work table by the extension and rotation of the rod-like members. A curved surface processing apparatus,
A rotating table for rotating the workpiece on the upper surface of the work table;
By rotating the workpiece, the machining tool is scanned, and by the movement only on the work table side so as to keep a constant angle between the normal line at the contact point of the workpiece with the machining tool and the machining tool . Means for controlling the tilt posture of the workpiece ;
Means for maintaining a constant contact pressure between the work tool and the work tool that presses against the work piece in a small area by causing elastic deformation at the time of machining with elasticity in a spherical or barrel shape;
Means for adjusting a machining amount for the workpiece by controlling a scanning speed of the machining tool;
Have
The processing tool has a porous structure having a resin material as a main component, and abrasive grains as an abrasive are scanned while being supplied from the outside during processing. A parallel link mechanism calibration method in a curved surface processing apparatus,
A spherical sensor is clamped on the work table, a displacement sensor that detects the displacement of the work table with respect to the base plate, and a collimator that detects the inclination of the surface of the spherical master,
The work table is operated so as to scan the surface of the spherical original material while maintaining the posture in which the optical axis of the collimator is orthogonal to the surface of the spherical original material. Acquire tilt data with respect to the optical axis of the synchronized surface of the spherical prototype,
The calibration method of the parallel link mechanism in the curved surface machining apparatus according to claim 1, wherein a position control parameter of the parallel link mechanism is identified based on values of the actual displacement and the inclination data.

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