JP2023116280A - Projector and measuring apparatus - Google Patents

Abstract

To provide a projector capable of inhibiting a laser beam from affecting a human body and preventing decrease of a frame rate (scan speed), and a measuring apparatus.SOLUTION: The projector comprises: a light emission unit including a plurality of laser beam sources that can be controlled for individual turning on/turning off; and a control device controlling respective turning on/turning off of the laser beam sources. The control device simultaneously turns on a combination of two or more laser beam sources in which a total amount of energy of laser beam having the possibility of entering human eyes when the respective laser beam sources are simultaneously turned on is equal to or less than a predetermined threshold. The control device, for example, simultaneously turns on the plurality of laser beam sources so as not to simultaneously turn on adjacent laser beam sources. The light emission unit is for example a surface emission element array in which a plurality of surface light emission elements are one-dimensionally or two-dimensionally arranged.SELECTED DRAWING: Figure 3

Description

The present invention relates to projectors and measuring devices.

With the progress of AD (Autonomous Driving) and ADAS (Advanced Driver Assistance System), LiDAR (Light Detection and Ranging) is one of the measuring devices used for understanding the surrounding environment and estimating self-location. called. ) are being researched/developed. LiDAR consists of a projector (irradiator) that irradiates an object with projected light (irradiation light, light beam (laser light)) and reflected light (return light) that returns the projected light to the object to be measured. The difference between the timing when the projector emits the projected light and the timing when the receiver receives the reflected light (time of flight of the laser beam, hereinafter referred to as "TOF" (Time Of Flight) ) to get the distance to the object.

A laser beam emitted from a LiDAR projector has a small emission area and a high energy density, and may be harmful to the human body. In Japan, the Japanese Industrial Standards (JIS) stipulate the "radiation safety standards for laser products" (JIS C 6802). must be designed to meet the conditions specified in

No. 6,201,000, which aims to flexibly adjust the balance between the parameters of a laser light source (illumination range for eye safety, repetition rate, duty cycle, pulse power, reference to operating temperature, etc.). A LIDAR system is described. The LIDAR system operates a laser source of a laser scanner that emits a first laser pulse from a plurality of angular regions to a specific angular region, performs LIDAR measurements based on the reflection of the first laser pulses, and performs a LIDAR measurement based on the LIDAR measurements. to selectively activate the laser source of the laser scanner to emit a second laser pulse in a particular angular region.

Japanese Patent Publication No. 2020-509389

One type of LiDAR is flash LiDAR. Flash LiDAR does not include mechanical components such as motors and MEMS (Micro Electro Mechanical Systems), and is a powerful LiDAR in fields where durability is required, such as when used for in-vehicle purposes to realize AD and ADAS. considered as a candidate.

By the way, for example, as shown in FIG. 6A, when the light source 60 of the flash LiDAR emits light and the entire light projection target area 61 (FOV (Field Of View)) is simultaneously irradiated with laser light, the entire light source 60 ( For example, when all the light emitting elements 601) of the light source are controlled to light up at the same time, as shown in FIG. is more likely to exceed the threshold (safety value, upper limit value, allowable value, etc.) based on the above standards. In addition, when long-distance measurement is necessary, such as when measuring a vehicle in the opposite lane, it is necessary to irradiate a high-intensity laser beam. FIG. 6(b) is a graph showing the control described above, where the horizontal axis is time and the vertical axis is the light emission intensity of the light emitting element 601. energy) is shown schematically.

As one of the methods for solving the above problems, for example, as shown in FIG. It is conceivable to use one provided with the light emitting element 601 (for example, an addressable VCSEL (Vertical Cavity Surface Emitting Laser) array). In this case, the light projection target areas 61a to 61d of the individual light emitting elements 601a to 601d are set to be different, and the individual light emitting elements 601a to 601d are sequentially lit (lighted at different times). It is possible to irradiate the entire light projection target area 61 with the laser light and reduce the influence on the human body.

However, the above method inevitably increases the number of times the light-emitting elements 601a to 601d are turned on/off (on/off times). There is a problem that it becomes difficult to secure the rate (scanning speed of the entire light projection target areas 61a to 61d).

Patent Literature 1 describes adjusting the balance with other parameters by considering the irradiation range for ensuring eye safety as a parameter of the laser light source. However, there is no specific description of how to prevent the frame rate from dropping.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a projector and a measuring apparatus capable of preventing a drop in frame rate while reducing the effects of laser light on the human body. and

One aspect of the present invention for achieving the above object is a light projector, comprising: a light emitting unit having a plurality of laser light sources whose lighting/extinguishing can be individually controlled; and a control device for controlling the lasers so that the total amount of energy of the laser beams that may be incident on human eyes when the lasers are simultaneously turned on is equal to or less than a preset threshold value. Two or more combinations of light sources are illuminated simultaneously.

In addition, the problems disclosed by the present application and their solutions will be clarified by the description of the mode for carrying out the invention and the drawings.

ADVANTAGE OF THE INVENTION According to this invention, the fall of a frame rate (scan speed) can be prevented, reducing the influence on the human body by a laser beam.

It is a figure explaining the schematic structure of a measuring device. It is a top view of the surface emitting element array shown as an example of a light emission part. (a) is a schematic diagram showing a configuration example of a light projector used for explaining control of a surface light emitting element by a light projection control device, and (b) is a graph showing an example of control of a light emitting unit by the light projection control device. be. (a) to (c) are schematic diagrams showing examples of combinations of surface emitting elements that are lit simultaneously. (a) is a diagram for explaining a method of calculating the angle at which the surface emitting element sees the aperture stop in the case of "measurement condition 1"; FIG. 10 is a diagram for explaining a method of calculating an angle at which the is viewed from the aperture stop; (a) is a schematic diagram showing a configuration example of a light projector used for explaining control of a light emitting element, and (b) is a graph showing an example of control of a light source. (a) is a schematic diagram showing a configuration example of a light projector used for explaining control of a light emitting element, and (b) is a graph showing an example of control of a light source.

EMBODIMENT OF THE INVENTION Hereinafter, it demonstrates, referring drawings for the form for implementing this invention. In the following description, the same or similar configurations may be denoted by common reference numerals, and redundant description may be omitted.

FIG. 1 shows a schematic configuration (block diagram) of a measuring device 100 shown as one embodiment. The exemplified measurement device 100 is a flash LiDAR (Flash Light Detection and Ranging, Laser Imaging) installed in a vehicle equipped with an AD (Autonomous Driving) or an ADAS (Advanced Driver Assistance System). Detection and Ranging).

The measurement apparatus 100 measures the time (hereinafter referred to as “TOF” (hereinafter referred to as “TOF” ( The distance to the object 50 is measured by measuring the Time Of Flight).

In the following description, the light beam (irradiation light) that the measurement apparatus 100 irradiates toward the object 50 is referred to as "projected light", and the light that is reflected by the object 50 and returns. is called "reflected light".

For example, the measuring device 100 assists the detection of people, vehicles, objects, etc., as well as ensuring the safety of the driver of the vehicle and people around the vehicle, and the damage caused to objects around while driving the vehicle. Provide various information useful for reducing

As shown in the figure, the exemplified measuring apparatus 100 includes a light emitting unit 111, a light projection control device 112, a current source 113, a light projecting optical system 114, a light receiving optical system 115, a light receiving unit 116, a TOF measuring device 117, and an arithmetic unit. 150, and communication I/F 160. Among them, the light emitting unit 111, the light projection control device 112, the current source 113, and the light projection optical system 114 constitute a "projector" that generates projection light. The light receiving optical system 115 and the light receiving unit 116 constitute a "light receiver" that receives the reflected light.

The light emitting unit 111 includes a plurality of surface emitting laser light sources (for example, VCSEL (Vertical Cavity Surface Emitting Laser)) arranged one-dimensionally or two-dimensionally on a substrate (semiconductor substrate, ceramic substrate, etc.). )), and is configured using a surface light emitting element array (addressable VCSEL array) capable of independently controlling the on/off of each surface light emitting element 10 . The surface emitting element 10 generates a light beam (laser light) that serves as projection light.

FIG. 2 is a plan view of a surface emitting element array shown as an example of the light emitting section 111. As shown in FIG. The illustrated surface emitting element array has a plurality of surface emitting elements 10 arranged in a square lattice on one surface of a substrate 22 . In the figure, a plurality of surface emitting elements 10 are provided so that their emission directions (optical axes) are directed in a direction perpendicular to the plane of the paper (+z direction shown in the figure). The illustrated surface light emitting element array is electrically connected to a plurality of current supply lines 23 for supplying a current (driving current) for causing the surface light emitting elements 10 to emit light from a current source 113 .

The arrangement form of the surface emitting elements 10 in the surface emitting element array is not necessarily limited to that shown in FIG. There may be. Further, the surface emitting elements 10 do not necessarily have to be two-dimensionally arranged on the substrate 22 and may be one-dimensionally arranged on the substrate 22 .

Returning to FIG. 1, the light projection control device 112 generates a control signal for controlling the current source 113 that supplies the drive current for the surface light emitting element 10 of the light emitting unit 111, and inputs it to the current source 113, whereby the current The current (driving current) supplied from the source 113 to the surface emitting element 10 is controlled. In addition, the light projection control device 112 outputs a signal indicating the timing at which the surface light emitting element 10 emits light (the timing at which the projected light is emitted from the surface light emitting element 10; hereinafter referred to as “projection timing”). to enter. The light projection control device 112 periodically and repeatedly causes the surface light emitting elements 10 to emit light by, for example, periodically repeating ON/OFF control of the electric current flowing through each of the surface emitting elements 10 .

The current source 113 supplies a current to the surface emitting element 10 according to the control signal input from the light projection control device 112 . The current source 113 supplies, for example, a periodic square-wave current to the surface emitting elements 10 for turning on and off the current flowing through each of the surface emitting elements 10 .

The projection optical system 114 adjusts the light distribution of the projected light by, for example, applying an optical action (refraction, scattering, diffraction, etc.) to the projected light emitted from the light emitting unit 111 . The projection optical system 114 is configured using optical components such as various lenses such as a collimator lens, a diffraction grating, and a reflector (mirror).

The light-receiving optical system 115 converges the reflected light returning from the object 50 onto the light-receiving section 116 . The light receiving optical system 115 is configured using, for example, various lenses such as a condenser lens, various filters such as a wavelength filter, and optical components such as a reflector (mirror).

The light receiving unit 116 is configured using, for example, a photodetector such as a SPAD (Single Photon Avalanche Diode), a photodiode, or a balanced photodetector. The light receiving unit 116 photoelectrically converts the reflected light incident from the light receiving optical system 115 to generate a current (hereinafter referred to as “light receiving current”) corresponding to the intensity of the reflected light. The light receiving unit 116 inputs a signal indicating the timing of receiving the reflected light (hereinafter referred to as “light receiving timing”) and the generated light receiving current to the TOF measuring device 117 .

The TOF measurement device 117 obtains the TOF based on the signal indicating the light projection timing input from the light emission control device 112 and the signal indicating the light reception timing input from the light receiving unit 116 . The TOF measurement device 117 is configured using, for example, a time measurement IC (Integrated Circuit) equipped with a TDC (Time to Digital Converter) circuit. The TOF measuring device 117 inputs the obtained TOF and the received light current input from the light receiving unit 116 to the arithmetic device 150 .

The arithmetic unit 150 is configured using a processor (CPU (Central Processing Unit), MPU (Micro Processing Unit), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), DSP (Digital Signal Processor), etc.). be. The calculation device 150 generates information used for various measurements such as detection of the target object 50 and distance measurement based on the received light current and the TOF input from the TOF measurement device 117 . The above information is, for example, a histogram used in Time Correlated Single Photon Counting, a distance to each point of the object 50, a point cloud (point cloud information) etc. The computing device 150 also controls the light projection control device 112 and the light receiving section 116 . The calculation device 150, for example, controls the light projection control device 112 and the light receiving unit 116, thereby adjusting the light projection timing and the light reception timing so that the processing related to the generation of the histogram is speeded up or optimized. Control. The information generated by the computing device 150 is provided (transmitted) to devices that use the information (hereinafter referred to as “various devices 40”) via a communication I/F 160 (I/F: Interface). .

Various utilization devices 40, for example, create an environment map by point cloud, self-position estimation (SLAM (Simultaneous Localization and Mapping)) using a scan matching algorithm (NDT (Normal Distributions Transform), ICP (Iterative Closest Point), etc.) etc.

<Light emission control>
The light projection control device 112 controls the surface light emitting element 10 so that the total amount of laser light energy that may enter the human eye is equal to or less than a preset threshold value (safety value, upper limit value, allowable value, etc.). Two or more combinations are controlled to light up at the same time. This reduces the effect (exposure dose) on the human body when the laser light is accidentally irradiated on the human body, and the measurement device 100 and the projector comply with the radiation safety standards (IEC: International Electrotechnical Commission) for laser products. 60825-1 of Japanese Industrial Standards (JIS: Japanese Industrial Standards) "Radiation Safety Standards for Laser Products" (JIS C 6802), etc.). Also, by simultaneously turning on two or more of the above combinations, it is possible to prevent a decrease in the frame rate (scanning speed of the light projection target area).

FIG. 3A is a schematic diagram showing a configuration example of a light projector used for explaining the control of the surface light emitting element 10 by the light projection control device 112. FIG. The reference numerals in the figure correspond to the reference numerals attached to FIG. In the example of FIG. 1, for the sake of simplicity of explanation, the light emitting section 111 has four surface light emitting elements 10a to 10d arranged on a substrate at equal intervals in a one-dimensional manner. It is assumed that the surface emitting elements 10a to 10d all have common specifications (for example, they are all products of the same model number).

As shown in the figure, out of the four surface emitting elements 10a to 10d, the laser beam emitted from the surface emitting element 10a passes through the projection optical system 114 to the projection area 51a, and also from the surface emitting element 10b. The emitted laser light passes through the light projecting optical system 114 to the light projecting area 51b, and the laser light emitted from the surface emitting element 10c passes through the light projecting optical system 114 to the light projecting area 51c. The laser light emitted from the light emitting element 10d is distributed to the light projection area 51d via the light projection optical system 114, respectively.

Here, for example, each of two adjacent surface emitting elements 10 (any combination of surface emitting elements 10a and 10b, surface emitting elements 10b and surface emitting elements 10c, surface emitting elements 10c and surface emitting elements 10d) , the two laser beams distributed toward the projection target area by the projection optical system 114 may enter the human eye at the same time and have a harmful effect on the human body. be. Therefore, the light projection control device 112 reduces the effect of the laser light on the human body by controlling the adjacent surface emitting elements 10 not to light at the same time, so that the measuring device 100 (projector) complies with the radiation safety standards for laser products. make it fulfill

FIG. 3(b) is a graph showing the above control. In this graph, the horizontal axis is time and the vertical axis is the emission intensity of the surface light emitting device 10, and shows the amount of projected light (energy of projected light) and the amount of exposure (energy to which a person is exposed). As shown in the figure, in this example, the combination of the surface emitting elements 10a and 10c is lit at the same time, and then the combination of the surface emitting elements 10b and 10d is lit at the same time. As can be seen from the figure, the exposure dose at each lighting timing is 1/2 of the exposure dose (FIG. 6B) in the method shown in FIG. 6A. In this case, the time required for one frame is half the time (FIG. 7B) in the method shown in FIG. can increase the frame rate (scanning speed of the area to be projected).

In this example, in order not to light two adjacent surface light emitting elements 10 at the same time, every other combination of surface light emitting elements 10 is lighted at the same time. You may make it light simultaneously every 2 or more. Also, any combination of two or more surface emitting elements 10 that are not adjacent to each other may be lit at the same time.

Further, the plurality of surface emitting elements 10 constituting the light emitting section 111 are classified into a plurality of groups each having a plurality of adjacent surface emitting elements 10 as elements, and the surface emitting elements 10 belonging to two adjacent groups are simultaneously lit. You can choose not to let it happen. However, in this case, the total amount of energy of the laser light that may enter the human eye when all the surface emitting elements 10 in one group are turned on at the same time is set to a preset threshold value (safety value, upper limit value, permissible value, etc.).

FIG. 4 shows an example of a combination of the surface emitting elements 10 that are lit simultaneously. (a) is when every other surface light emitting element 10 is lit at the same time; (b) is when every other surface light emitting element 10 is simultaneously lit; This is a case where a group having one or more surface emitting elements 10 (in this example, a group having two surface emitting elements 10) is set as a unit, and the surface emitting elements 10 are simultaneously turned on every other group.

It should be noted that how to select the combination of the surface light emitting elements 10 to be simultaneously lit among the surface light emitting elements 10 constituting the light emitting unit 111 (surface light emitting element array) depends on, for example, the arrangement interval of the surface light emitting elements 10, the surface light emitting element 10 Arrangement form of the elements 10 (for example, an orthorhombic lattice, a triangular lattice, a square lattice, a rectangular lattice, a hexagonal lattice, etc.), light beams emitted from the surface emitting elements 10 or the light beams emitted from the light emitting optical system 114 It is determined by considering the beam divergence angle (beam divergence angle, pitch) after passing through and the viewing angle of the human eye (viewing angle determined according to the aperture stop of the pupil).

For example, when the wavelength of the laser light is 400 to 1400 nm, "Measurement conditions 1" (telescope, binoculars, etc. (hereafter referred to as "observation equipment" for collimated beams where the hazard is increased by ), "aperture stop of 50 mm at 2000 mm", and "measurement condition 3" (naked eye, low power magnifier and operating beam). (Applied to the determination of the radiation dose for the

In this case, under the above "measurement condition ₁ ", as shown in FIG. /2000) For example, under the above "measurement condition 3", the angle _θ2 at which the surface emitting device 10 (laser product) sees the aperture stop is 4.0°, as shown in Fig. 5(b). (≈2*arctan(7/2/100)).

For this reason, for example, in the configuration of the projector shown in FIG. In order to prevent the light from entering the human eye at the same time, under “measurement condition 1”, the light beam emitted from the surface emitting element 10 or the beam divergence angle (beam divergence angle) and pitch of 0.7° (=1.4°/2) or more. Further, in "measurement condition 3", the beam divergence angle (beam divergence angle) and the pitch after the light beam emitted from the surface emitting element 10 or the light beam passes through the projection optical system 114 is 2.0° (=4.0 °/2) or more.

As described above, in the measuring apparatus 100 of the present embodiment, the total amount of laser light energy that may enter the human eye when the light projection control devices 112 are turned on at the same time is set in advance. A combination of two or more of the surface emitting elements 10 that is equal to or less than the threshold value (safety value, upper limit value, allowable value, etc.) is controlled to light up at the same time. Therefore, the influence (exposure dose) of the laser beam on the human body can be reduced, the measurement device 100 (projector) can meet the radiation safety standards for laser products, and the frame rate (scanning of the area to be projected) can be reduced. speed) can be prevented.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments and includes various modifications. In addition, the above-described embodiment describes the configuration in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. Moreover, it is possible to add, delete, or replace a part of the configuration of the above embodiment with another configuration.

10 surface light emitting element 22 substrate 50 object 100 measuring device 111 light emitting unit 112 light projection control device 113 current source 114 light projecting optical system 115 light receiving optical system 116 light receiving unit 117 TOF measuring device 150 computing device, 160 communication interface

Claims (8)

a light emitting unit having a plurality of laser light sources that can be individually controlled to be turned on/off;
a control device for controlling lighting/extinguishing of each of the laser light sources;
with
The control device selects a combination of two or more of the laser light sources such that the total amount of energy of the laser light that is likely to be incident on human eyes when they are simultaneously lit is equal to or less than a preset threshold value. light up at the same time
floodlight. A light projector according to claim 1,
The control device selects the plurality of laser light sources to be turned on at the same time so that the exposure dose to the human body due to peering using the observation device is equal to or less than a preset threshold.
floodlight. A light projector according to claim 1,
The control device selects the plurality of laser light sources to be turned on at the same time so that the exposure dose to the human body when looking into it with the naked eye is equal to or less than a preset threshold.
floodlight. A light projector according to claim 1,
The control device turns on the plurality of laser light sources simultaneously so as not to turn on the adjacent laser light sources at the same time.
floodlight. A light projector according to claim 4,
The controller simultaneously illuminates every other combination of one or more of the laser light sources.
floodlight. A light projector according to claim 1,
The plurality of laser light sources constituting the light emitting unit are classified into a plurality of groups each having a plurality of adjacent laser light sources as elements, and the surface emitting elements of two adjacent groups are classified into a plurality of groups so as not to light up at the same time. lighting the laser light sources of the group simultaneously;
floodlight. The projector according to any one of claims 1 to 6,
The light-emitting unit is a surface-emitting element array having a structure in which the surface-emitting elements that are the laser light sources are arranged one-dimensionally or two-dimensionally,
floodlight. A measuring device configured using the projector according to any one of claims 1 to 6,
the light projector;
a light receiver that receives reflected light of the light projected from the light projector;
with
measuring the distance to the detection target based on the light reception result of the light receiver;
measuring device.

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