JP7238928B2 - Photodetector and rangefinder - Google Patents

Description

The present invention relates to photodetectors and ranging devices.

In recent years, the development of a distance measuring device called LIDAR (Light Detection And Ranging) for self-driving automobiles is progressing. In this LIDAR, when traveling at a vehicle speed of about 100 [km/h] per hour, it is necessary to accurately measure the distance to an object up to about 300 [m] for safety. Of Flight) method is the mainstream. In the direct TOF method, a coherent laser beam is emitted in the direction to be detected, the laser beam that has collided with an object and is reflected is made incident on a light receiving part such as a photodiode via a lens, and the time from emission to detection is measured. It is a method to measure the distance to an object from the speed of light and the speed of light. A distance measuring device using the direct TOF method is generally configured to mechanically rotate 360[°] in a horizontal plane and stack a plurality of measurement systems in the vertical direction.

However, conventional distance measuring devices have the problem that sufficient resolution cannot be obtained in the vertical direction because the number of measuring systems stacked in the vertical direction is limited due to their sizes. There was a problem that miniaturization of equipment becomes difficult when a large number of are stacked. Furthermore, there was a problem that the durability of the mechanical 360° rotation mechanism had to be ensured, and that the structure had to be constructed in consideration of earthquake resistance.

As a technique for solving the problems of vertical resolution and mechanical durability, we have developed a deflection array that transmits image information from the imaging optics to the detector for the purpose of significantly increasing the signal-to-noise ratio of the detector. A pixel that is input immediately before and is operated within a two-dimensional array corresponding to each point in the field of view is determined, reflected light from the pixel that is operated on is directed to the photodiode, and light is reflected from the pixel that is operated off. The photodiode is a photosensitive element or photodiode array consisting of a two-dimensional array of photosensitive pixels, which is obtained from a two-dimensional light deflection array. A configuration is disclosed in which the two-dimensional array of detection light is directly detected by a two-dimensional photodiode array (for example, Patent Document 1).

However, the technique described in Patent Document 1 requires a structure having a plurality of transistors or the like arranged directly under each pixel for writing captured image information, and it takes time to write the operation information of each pixel. Therefore, there is a problem that high-speed operation is difficult. In addition, since the two-dimensional reflected light obtained from the light deflection array is directly incident on the two-dimensional photodiode array, there is a problem that a large-sized high-performance photodiode array is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photodetector and a distance measuring device that can suppress an increase in size and can detect light at high speed.

In order to solve the above-described problems and achieve the object, the present invention provides a photodetector comprising: a light guide section for guiding incident light, which is reflected light from an object incident from the outside; a deflection section for deflecting the incident light that has entered the section and is guided by the light guide section; a light receiving section, wherein the deflection section has a plurality of optical deflection element groups including a plurality of optical deflection elements for deflecting the incident light; The plurality of optical deflection elements included in the optical deflection element group are passively matrix-driven to simultaneously perform deflection operations, and the plurality of optical deflection element groups are simultaneously or simultaneously connected with the passage of time. The deflection operation is performed in order.

According to the present invention, it is possible to suppress an increase in size and to detect light at high speed.

FIG. 1 is a diagram illustrating a typical photodetector. FIG. 2 is a diagram showing an example of the configuration of a general photodetector. FIG. 3 is a diagram showing an example of the configuration of a conventional photodetector. FIG. 4 is a diagram schematically showing a cross section of an optical deflection element of the DMD. FIG. 5 is a diagram illustrating an example of the configuration of the distance measuring device according to the embodiment; 6A and 6B are a top view and a cross-sectional view of the optical deflection element of the rangefinder according to the embodiment. 7A and 7B are diagrams for explaining an example of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to the embodiment. FIG. 8 is a diagram showing an example of a timing chart of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to the embodiment. FIG. 9 is a flowchart showing an example of the flow of ranging operation of the ranging device according to the embodiment. 10A and 10B are diagrams for explaining an example of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to Modification 1. FIG. 11A and 11B are diagrams for explaining an example of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to Modification 2. FIG. FIG. 12 is a diagram showing an example of a timing chart of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to Modification 2. As shown in FIG. 13A and 13B are diagrams showing an example of a timing chart showing an operation of changing the laser intensity in the distance measuring device according to Modification 3. FIG.

Embodiments of a photodetector and a distance measuring device according to the present invention will be described in detail below with reference to the drawings. In addition, the present invention is not limited by the following embodiments, and the constituent elements in the following embodiments can be easily conceived by those skilled in the art, substantially the same, and so-called equivalent ranges. is included. Furthermore, various omissions, replacements, changes and combinations of components can be made without departing from the gist of the following embodiments.

(For conventional photodetectors)
FIG. 1 is a diagram illustrating a typical photodetector. FIG. 2 is a diagram showing an example of the configuration of a general photodetector. A typical detector configuration will be described with reference to FIGS. 1 and 2. FIG.

In FIG. 1, a distance measuring device 101 is a general distance measuring device, and objects 102 to 105 indicate objects existing in space and subject to distance measurement. A distance measuring device 101 is a device for measuring distances to external objects such as objects 102 to 105 . Distance measuring device 101 simultaneously or sequentially measures distances to objects 102 to 105 located at different distances.

As shown in FIG. 2, the distance measuring device 101 includes, for example, a laser light source 201, a shaping lens 202, a polygon mirror 203, a lens 204, an imaging lens 205, and a light receiver 206.

The laser light source 201 is a light source that emits near-infrared laser light, for example. The shaping lens 202 is a lens that shapes the laser light emitted from the laser light source 201 into coherent laser light. The polygon mirror 203 is a member that reflects the laser beam shaped by the shaping lens 202 so as to scan in the horizontal direction (for example, the range of 120[°] to 360[°]) and directs it toward the lens 204 . A lens 204 is a lens that emits the laser beam reflected by the polygon mirror 203 to the outside of the distance measuring device 101 . In this way, the laser light emitted from the lens 204 is reflected by an object existing in the outside world and enters the distance measuring device 101 as reflected light.

The imaging lens 205 is a lens that forms an image on the light receiver 206 of reflected light from an object that has entered from the outside world. The light receiver 206 is a member that simultaneously or sequentially detects reflected light that has passed through the imaging lens 205 . The distance measuring device 101 measures the distance to each object from the reflected light detected by the light receiver 206, and acquires three-dimensional information in the horizontal, vertical and depth directions.

The distance measuring device 101 as described above is desired to detect a wide range of distance measurement data with high resolution and as fast as possible, and is also desired to be small and inexpensive. However, it has the problem of becoming a large-scale device.

FIG. 3 is a diagram showing an example of the configuration of a conventional photodetector. FIG. 4 is a diagram schematically showing a cross section of an optical deflection element of the DMD. Next, the configuration of a conventional photodetector described in, for example, US Patent Application Publication No. 2017/0357000 will be described with reference to FIGS. 3 and 4. FIG.

The photodetector 101a is a device that receives and detects reflected light from external objects such as the objects 111 and 112 . The reflected light may be the reflected light emitted from some laser light source, as shown in FIG. As shown in FIG. 3, the photodetector 101a includes an imaging lens 211, a DMD (Digital Micromirror Device) 212, an imaging lens 213, and a light receiver 214.

The imaging lens 211 is a lens that forms an image on the DMD 212 of reflected light from an object that has entered from the outside world. The DMD 212 is an optical deflection array in which a large number of movable minute mirrors (optical deflection elements 212a shown in FIG. 4) are two-dimensionally arranged on an integrated circuit substrate. The imaging lens 213 is a lens that forms an image on the light receiver 214 of the light reflected by the ON operation of the optical deflection element 212 a in the DMD 212 . The photodetector 214 is a photodiode array that detects light that is reflected by the ON-operated optical deflection element 212 a in the DMD 212 and that has passed through the imaging lens 213 . In order to measure the distance of a distant object, it is desirable to use an avalanche photodiode, which is suitable for measuring a small number of photons, as the light receiver 214 rather than a normal photodiode.

The photodetector 101a acquires image information of an external object immediately before detection by the DMD 212, and among the optical deflection elements 212a of the DMD 212, the optical deflection element 212a to be turned on and the optical deflection element 212a to be turned off. to determine. At this time, it is necessary to store information on the ON/OFF operation of each optical deflection element 212a. Then, the DMD 212 of the photodetector 101 a turns ON only the optical deflection element 212 a determined to be turned ON, and reflects the reflected light from the imaging lens 211 toward the imaging lens 213 . As a result, the photodetector 101a can improve the signal-to-noise ratio.

Here, the configuration of the optical deflection element 212a of the DMD 212 will be described with reference to FIG. The optical deflection element 212a has a mirror configuration section 301 and an SRAM (Static Random Access Memory) 302, as shown in FIG.

The mirror component 301 is layered on the SRAM 302 and has a structure in which the angle of the mirror member is changed by torsion beams. The SRAM 302 is, as described above, a storage section including P-type transistors, N-type transistors, multi-layer wiring, etc., for storing information on the ON/OFF operation of the light deflection element 212a. The light deflection element 212 a having such a configuration moves the mirror member of the mirror configuration section 301 according to the ON/OFF information stored in the SRAM 302 .

In the photodetector 101a as described above, the image information of the object in the external world is acquired immediately before detection by the DMD 212, and the optical deflection element 212a to be turned on is specified based on the image information. However, for example, in the above-mentioned US Patent Application Publication No. 2017/0357000, it is not necessarily clear how to specify. Further, in the photodetector 101a, image information must be read each time the distance measurement operation is performed, but the operation for coping with an unpredictable case such as being unable to acquire the image information is not clear. In addition, the photodetector 101a requires a structure having a plurality of transistors and the like arranged directly under each pixel of the DMD 212 for writing captured image information. becomes high, and it takes time to write the operation information of each pixel, so there is a problem that high-speed operation is difficult. In addition, since the optical deflection element 212a is of a torsion beam type and movable, a restoring force of the beam and a residual vibration are generated in the displacement in the reflection direction. I have a problem. Further, since the distance measurement operation is performed after specifying the optical deflection element 212a to be turned on, the distance measurement data is obtained at a timing slightly shifted from the specified timing. There is also a problem that it can be obtained. In addition, since the two-dimensional reflected light obtained from the DMD 212 as a light deflection array is directly incident on the light receiver 214 as a two-dimensional photodiode array, there is a problem that a large-sized high-performance photodiode array is required. be.

The configuration and operation of the distance measuring device 1 according to this embodiment, which can solve the above-described problems, will be described below.

(Configuration of distance measuring device)
FIG. 5 is a diagram illustrating an example of the configuration of the distance measuring device according to the embodiment; 6A and 6B are a top view and a cross-sectional view of the optical deflection element of the rangefinder according to the embodiment. The configuration of the distance measuring device 1 according to the present embodiment will be described with reference to FIGS. 5 and 6. FIG.

As shown in FIG. 5, the distance measuring device 1 includes a laser light source 11 (light source), a shaping lens 12, an optical scanning device 13 (optical scanning section), a reflecting mirror 14 (an example of an optical system), and a vertical A magnifying lens 15 (an example of an optical system), an imaging lens 16 (light guide section), a light deflection array 17 (deflecting section), a light absorbing plate 18 (light absorbing section), an image forming lens 19, and a light receiver 20 (light receiving portion) and a controller 21 .

The laser light source 11 is a light source that emits, for example, near-infrared pulsed laser light.

The shaping lens 12 is a lens that shapes the laser light emitted from the laser light source 11 into coherent laser light.

The optical scanning device 13 is a member that reflects the laser beam shaped by the shaping lens 12 so as to scan in the horizontal direction (an example of the first direction) and directs it toward the reflecting mirror 14 . Note that the scanning direction of the laser light by the optical scanning device 13 is not limited to the horizontal direction.

The reflecting mirror 14 is a mirror member that reflects the laser light reflected by the optical scanning device 13 toward the vertical magnifying lens 15 .

The vertical magnifying lens 15 is a lens that magnifies the laser light reflected by the reflecting mirror 14 in the vertical direction and radiates it to the outside of the distance measuring device 1 . In this way, the laser light emitted from the vertical magnifying lens 15 is reflected by an object existing in the outside world and enters the distance measuring device 1 as reflected light (detection light). Note that the direction in which the laser light is expanded by the vertical direction expansion lens 15 is not limited to the direction perpendicular to the scanning direction (for example, the horizontal direction) of the laser light by the optical scanning device 13, and at least the direction intersecting the scanning direction. If it is

The imaging lens 16 is a lens that guides reflected light (incident light) from an object that has entered from the outside and forms an image on the light deflection array 17 .

The optical deflection array 17 is an optical deflection array in which the optical deflection elements 17a shown in FIG. 6 are arranged two-dimensionally. The optical deflection array 17 forms a plurality of optical deflection element groups in which arbitrary optical deflection elements 17a of the plurality of optical deflection elements 17a are electrically connected to each other in parallel, and each optical deflection element constituting the optical deflection element group. As for 17a, optical deflection operations are simultaneously performed by passive matrix driving, and each optical deflection element group is caused to perform optical deflection operations simultaneously or sequentially as time elapses. The optical deflection element group is directly driven by an external signal (such as a signal from the controller 21) by passive matrix driving. In this way, by the ON operation by passive matrix driving of any one of the light deflection element groups of the light deflection array 17, the light from the imaging lens 16 that is incident on one of the light deflection elements 17a constituting the light deflection element group The reflected light is reflected (deflected) as ON light directed toward the imaging lens 19 by the optical deflection element 17a. The light beams reflected as ON light beams by the group of optical deflectors that have been turned on are collected or separated, and are simultaneously detected by the light receiver 20 . On the other hand, the reflected light from the imaging lens 16 that has entered one of the optical deflection elements 17a that constitute the optical deflection element group that is in the off state is turned off toward the light absorbing plate 18 by the optical deflection element 17a. is reflected (deflected) as

The light absorbing plate 18 is a member that absorbs light reflected as OFF light by the light deflection array 17 .

The imaging lens 19 is a lens that forms an image of the ON light reflected by the light deflection array 17 on the light receiver 20 .

The light receiver 20 is one to several photodiodes (an example of light receiving elements) that sequentially detect (receive) the ON light that has passed through the imaging lens 19 . In addition, it is not limited to a photodiode, and may be configured by, for example, an avalanche photodiode (an example of a light receiving element).

The controller 21 is a control device that controls the overall operation of the distance measuring device 1 . The controller 21 executes, for example, a laser light emission operation by the laser light source 11 , a scanning operation by the optical scanning device 13 , and an on/off operation of the optical deflection element group by the optical deflection array 17 . Further, the controller 21 measures the distance to the point of the object from the time from when the laser light source 11 emits the laser light to when the ON light is detected by the light receiver 20 and the speed of light, and uses the distance information. to generate a 3D map (three-dimensional image).

With the configuration of the distance measuring device 1 as described above, the distance to an object in the external world can be measured one by one as time elapses. If the photodetector 20 has several photodiodes, it is possible to simultaneously measure the distance at a plurality of points.

In the case where the imaging lens 16, the optical deflection array 17, the light absorbing plate 18, the imaging lens 19, the light receiver 20, and the controller 21 are extracted from the distance measuring device 1, the incident light from the outside is sequentially It can also be regarded as an example of a photodetector for detection, and the distance measuring device 1 itself can also be regarded as an example of a photodetector when only the relevant component is considered.

Next, the details of the configuration of the optical deflection element 17a of the optical deflection array 17 will be described.

As shown in FIG. 6, the optical deflection element 17a includes a substrate 31, a wiring 32, an insulating film 33, a connection hole 34, electrodes 35a and 35b, a contact member 36, a fulcrum member 37, and a plate-shaped member. 38 , a post 39 and a hat-shaped member 40 . FIG. 6(b) is a cross-sectional view taken along the line A-A' in FIG. 6(a).

The substrate 31 is a plate-shaped member having a planar portion. As shown in FIG. 6A, the wirings 32 are a plurality of wirings formed of conductors arranged in parallel on the substrate 31 . As shown in FIG. 6B, the insulating film 33 is a film for insulating and protecting the wiring 32 arranged on the substrate 31 and planarizing it.

As shown in FIG. 6B, the connection hole 34 penetrates the insulating film 33 to electrically connect the electrode 35a and the arbitrary wiring 32, and electrically connect the electrode 35b and the arbitrary wiring 32. It is a member to be connected. The electrodes 35a and 35b are electrically connected to an arbitrary wiring 32 through the connection hole 34, thereby electrically connecting different optical deflection elements 17a. A group of optical deflection elements electrically connected in parallel is formed.

The electrodes 35 a and 35 b are electrodes arranged on the insulating film 33 so as to be symmetrical with respect to the fulcrum member 37 . As described above, the electrodes 35a and 35b are electrically connected to arbitrary wirings 32 through the connection holes 34, respectively.

As shown in FIG. 6B, the contact member 36 is a member arranged on the insulating film 33 on the side opposite to the electrodes 35a and 35b with respect to the fulcrum member 37, and when the plate-shaped member 38 is inclined, the contact member 36 It is a member to be contacted.

A plurality of fulcrum members 37 (two in the example of FIG. 6A) are arranged between the electrodes 35a and 35b on the planar portion of the substrate 31, and are arranged on the surface of the plate-shaped member 38 opposite to the reflecting surface. It is a member that comes into contact with the plate-shaped member 38 so as to move freely toward and away from it, and serves as a fulcrum for the tilting motion of the plate-shaped member 38 .

The plate-shaped member 38 is supported by the fulcrum member 37 so as to face the electrodes 35a and 35b so as to be freely contactable and detachable. It is a plate-shaped elastic member including a conductive region facing the electrodes 35 a and 35 b on at least a part of the surface in contact with the fulcrum member 37 .

The pillars 39 are arranged on the planar portion of the substrate 31 and on the end side of the plate-shaped member 38 on the line connecting the fulcrums of the plurality of fulcrum members 37 in the direction of the line. It is a pillar-shaped portion that regulates the The cap-shaped member 40 is a cap-shaped member installed at the end of each of the columns 39 opposite to the substrate 31, and covers a part of the end of the plate-shaped member 38 in the above-described line direction to form a plate. It is a member that regulates the arrangement of the shape member 38 and prevents it from popping out. However, a gap is provided between the plate-shaped member 38 and the cap-shaped member 40 so that the plate-shaped member 38 can be freely tilted.

As described above, unlike the optical deflection element 212a shown in FIG. 4, the optical deflection element 17a does not have a portion corresponding to the SRAM 302 including transistors and the like, and has only a configuration corresponding to the mirror configuration portion 301. It's becoming Therefore, the optical deflection array 17 having the optical deflection elements 17a can be manufactured with a large reduction in manufacturing man-hours compared to the conventional DMD 212, and can be easily manufactured with a high yield.

Also, with the configuration of the light deflection element 17a as described above, the cold light deflection operation is performed in the direction of the arrow shown in FIG. 6(a). Specifically, the inclination angle of the plate-shaped member 38 is determined by contact with the fulcrum member 37, the contact member 36, and the cap-shaped member 40, and the inclination direction is determined by the voltage applied to the electrodes 35a and 35b. That is, the plate-shaped member 38 performs tilting operation so as to reflect the detection light as ON light, or changes the detection light as OFF light, as shown in FIG. Perform tilting motion so as to reflect as In this way, the optical deflection element 17a does not have the restoring force of the torsion beam unlike the optical deflection element 212a of the DMD 212 described above, so that the optical deflection operation can be performed at high speed.

(Switching operation of pattern of optical deflection element group)
7A and 7B are diagrams for explaining an example of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to the embodiment. FIG. 8 is a diagram showing an example of a timing chart of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to the embodiment. The switching operation of the pattern of the optical deflection element group to be turned on will be described with reference to FIGS. 7 and 8. FIG. 7 and 8, the distance measuring device 1 has a horizontal viewing angle of 120 [°], a vertical viewing angle of 20 [°], a detection rate of 5 [Hz], and a ranging distance of up to 300 [m]. It is assumed that 1200 points and 40 vertical pixels are used for detection. Here, the detection rate is the processing rate when detection is performed by all the pixels (optical deflection elements 17a) of the optical deflection array 17 once. Further, it should be added that the number of pixels of the optical deflection array 17 shown in FIG. 7 is not the same as the number of horizontal and vertical pixels described above for the sake of simple explanation.

FIG. 7 shows an example in which the pixels (optical deflection elements 17a) arranged in each horizontal direction (an example of the second direction) are electrically connected in parallel as the optical deflection element group in the optical deflection array 17. FIG. Each cell of the optical deflection array 17 shown in FIG. 7 corresponds to each optical deflection element 17a, and the entire area of the optical deflection array 17 corresponds to the entire area of the external measurement space. In FIG. 7, there are patterns (1) to (40) as patterns indicating which of the plurality of light deflection element groups is to be turned on. Specifically, in pattern (1), the first horizontal optical deflection element group from the top of FIG. 7 is turned on (other optical deflection element groups are turned off). ), and pattern (2) shows a state in which the second horizontal light deflection element group is turned on. Similarly, patterns are defined, and the last pattern (40) shows a state in which the horizontal light deflection element group at the bottom of FIG. 7 is turned on. FIG. 7 also shows a state in which reflected light (detection light) reflected from an object in the external world is incident on the third vertical pixel row (incident light area ILA) from the left of the light deflection array 17 . there is This is because, as described above, the laser light expanded in the vertical direction by the vertical expansion lens 15 is emitted to the outside, so that the reflected light of the laser light from the object is also the detection light expanded in the vertical direction. This is because it is incident on the distance measuring device 1 as a The arrangement direction of each optical deflection element 17a included in the optical deflection element group is not limited to the horizontal direction, and may be another direction.

For each pattern defined in this way, for example, as shown in FIG. 7, in a state in which the detection light is incident on the incident light area ILA, the controller 21 sequentially performs pattern (1) to pattern (40). switch. In this case, the light receiver 20 detects the ON light reflected at the detection point DP, which is the pixel where the light deflection element group that is ON in each pattern and the incident light area ILA intersect. In this case, the receiver 20 may consist of a single photodiode or avalanche photodiode. In other words, the controller 21 recognizes that the light detected by the light receiver 20 at this timing is the ON light from the pixel where the light deflection element group that is ON in the pattern intersects with the incident light area ILA. Therefore, it is possible to finally generate a 3D map by using it as distance information to the point of the object corresponding to the ON light.

On the other hand, the reflected light (detection light) reflected by the regions other than the detection point DP in the incident light region ILA is absorbed as OFF light because the light deflection element 17a corresponding to the region is in the OFF state. It goes to the plate 18 and is absorbed by the light absorbing plate 18 . As a result, light other than the ON light among the reflected light (detection light) can be suppressed from remaining as stray light in the distance measuring device 1 .

That is, like the DMD 212 of the prior art, it is necessary to acquire image information for an external object immediately before detection, and to store information on the ON/OFF operation of each optical deflection element 212a in an element such as a transistor immediately below. However, in the optical deflection array 17 of the distance measuring device 1 according to the present embodiment, a reflected light flux is formed to be reflected to the light receiver 20 by turning on the optical deflection element group corresponding to a predetermined arbitrary pattern.

Here, FIG. 8 shows a timing chart of switching of each pattern. The detection time per specific incident light area ILA calculated from the horizontal resolution (the number of horizontal pixels), that is, the total detection time for patterns (1) to (40) is 166.7 [μsec]. . Since it is desirable that the detection time for each of the 40 patterns is equal, the detection time for one pixel is 4 [μsec] as shown in FIG. Here, for example, since the time required for distance measurement up to 300 [m] is 2 [μsec] at maximum, detection is sufficiently possible, and high-speed detection is possible. On the other hand, in the torsion beam type device represented by the DMD 212 in the above-described prior art, there is residual vibration after displacement, so it is difficult to perform the light deflection operation in a short time as described above.

The connection configuration of the optical deflection elements 17a in the optical deflection element groups to be turned on and which optical deflection element group is to be turned on in each pattern are not limited to the configuration shown in FIG. It can be arbitrarily determined according to the specifications of the light detection operation or range finding operation. Further, the number of pixels of the optical deflection array 17, the size of the optical deflection element 17a in the optical deflection array 17, and the like can be arbitrarily determined according to the specifications of the distance measuring device 1. FIG.

(Flow of range finding operation of range finder)
FIG. 9 is a flowchart showing an example of the flow of ranging operation of the ranging device according to the embodiment. The flow of the ranging operation of the ranging device 1 according to this embodiment will be described with reference to FIG.

<Step S11>
The laser light source 11 emits pulsed laser light such as infrared light under the control of the controller 21 . Laser light emitted from the laser light source 11 is shaped into coherent laser light by the shaping lens 12 . Then, the process proceeds to step S12.

<Step S12>
Under the control of the controller 21 , the optical scanning device 13 reflects the laser light shaped by the shaping lens 12 while scanning in a specific horizontal direction, and directs it toward the reflecting mirror 14 . The reflecting mirror 14 reflects the laser light reflected by the optical scanning device 13 toward the vertical magnifying lens 15 . Then, the process proceeds to step S13.

<Step S13>
The vertical magnifying lens 15 magnifies the laser light reflected by the reflecting mirror 14 in the vertical direction and radiates it to the outside of the distance measuring device 1 . Then, the process proceeds to step S14.

<Step S14>
The laser light emitted from the vertical magnifying lens 15 is reflected by an object existing in the outside world and enters the distance measuring device 1 as reflected light (detection light). Then, the process proceeds to step S15.

<Step S15>
The imaging lens 16 forms an image on the light deflection array 17 of reflected light from an object that has entered from the outside world. Then, the process proceeds to step S16.

<Step S16>
The light deflection array 17 turns on the light deflection element group corresponding to a specific pattern by passive matrix driving according to the control by the controller 21, and the light deflection element group in the on operation and the reflected light (detection light) are A pixel (light deflection element 17a) that intersects with the incident light region directs the reflected light to the light receiver 20 as ON light. Then, the process proceeds to step S17.

<Step S17>
The ON light reflected by the light deflection array 17 is imaged on the light receiver 20 by the imaging lens 19 . The light receiver 20 detects the ON light that has passed through the imaging lens 19 . Then, the controller 21 measures the distance to the point of the object from the time from when the laser light source 11 emits the laser light to when the light receiver 20 detects the ON light and from the speed of light. Then, the process proceeds to step S18.

<Step S18>
If there is a pattern that has not been switched yet (step S18: Yes), the process proceeds to step S19, and if all patterns have been switched (step S18: No), the process proceeds to step S20.

<Step S19>
The optical deflection array 17 switches to the next pattern to be switched under the control of the controller 21 . Such pattern switching can be performed at high speed by a high-speed optical deflection operation based on the configuration of the optical deflection element 17a as described above. Then, the process proceeds to step S16.

<Step S20>
The controller 21 obtains measured distance information corresponding to the pixels (one vertical column of pixels) corresponding to the incident light area of the light deflection array 17 on which the reflected light (detection light) is incident. Then, the process proceeds to step S21.

<Step S21>
If the horizontal scanning of the incident light region in the light deflection array 17 has been completed for the entire region (step S21: Yes), the process proceeds to step S22. In order to scan the next incident light area of the light deflection array 17 by scanning the laser light in the horizontal direction, the process returns to step S12.

<Step S22>
The controller 21 generates a 3D map using distance information corresponding to each pixel (optical deflection element 17a) of the optical deflection array 17. FIG.

Through the flow of steps S1 to S22 described above, the distance measuring operation by the distance measuring device 1 is executed. That is, a configuration as a transmitter including a laser light source 11, a shaping lens 12, an optical scanning device 13, a reflecting mirror 14, and a vertical magnifying lens 15, an imaging lens 16, an optical deflection array 17, a light absorbing plate 18, and an imaging lens 19 and the receiver (photodetector) including the photodetector 20 can perform range finding operations for all points in the external measurement space while synchronizing.

As described above, in the distance measuring device 1 according to the present embodiment, the imaging lens 16 guides the incident light, the optical deflection array 17 deflects the incident light guided by the imaging lens 16, The light receiver 20 detects part of the incident light deflected by the light deflection array 17, and the light deflection array 17 has a plurality of light deflection element groups including a plurality of light deflection elements 17a for deflecting the incident light. The optical deflection element group is configured by electrically connecting a plurality of optical deflection elements 17a in parallel, and the plurality of optical deflection elements 17a included in the optical deflection element group perform deflection operations simultaneously by passive matrix driving. , the plurality of optical deflection element groups perform deflection operations simultaneously or sequentially as time elapses. As a result, there is no need to vertically stack a plurality of detectors serving as measurement systems as in the prior art, and there is no need to store image information. It is possible to suppress an increase in size and to detect light at high speed. Further, since a structure having a plurality of transistors or the like arranged directly under each pixel like the DMD 212 for writing image information is unnecessary, the structure can be made simple. In addition, passive matrix driving eliminates the need for an external signal for driving each pixel, which simplifies the configuration of the controller. In addition, since a plurality of optical deflection elements 17a are connected in parallel and optical deflection operations are performed simultaneously, the number of pads for voltage application can be reduced.

In the distance measuring device 1 according to the present embodiment, the optical deflection element 17a includes the substrate 31 having a planar portion, the plate-shaped member 38 having a deflection surface for deflecting incident light, and the fulcrum member 37 is protruding from the planar portion and serves as a fulcrum of the tilting motion of the plate-shaped member 38 so as to be able to come into contact with and separate from the surface of the plate-shaped member 38 opposite to the deflection surface. By regulating the arrangement of the member 38 and providing a gap between the plate-shaped member 38 and the plate-shaped member 38, the plate-shaped member 38 can be freely tilted. The plate-shaped member 38 includes conductive regions facing the plurality of electrodes 35a and 35b on the surface of the plate-shaped member 38 opposite to the reflecting surface. As a result, unlike the optical deflection element 212a of the DMD 212 described above, the torsion beam does not have a restoring force, so that the optical deflection operation can be performed at high speed.

Further, in the optical deflection element 17a according to this embodiment, the light receiver 20 is a single light receiving element. This eliminates the need to vertically stack a plurality of detectors serving as measurement systems, thereby suppressing an increase in size.

(Modification 1)
A distance measuring device 1 as an example of a photodetector according to Modification 1 will be described, focusing on the points that are different from the distance measuring device 1 according to the above-described embodiment.

10A and 10B are diagrams for explaining an example of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to Modification 1. FIG. Referring to FIG. 10, the switching operation of the pattern of the optical deflection element group to be turned on in this modified example will be described.

FIG. 10 shows an example in which nine pixels (optical deflection elements 17a) of 3×3 are electrically connected in parallel as an optical deflection element group in the optical deflection array 17 . Each cell of the optical deflection array 17 shown in FIG. 10 corresponds to each optical deflection element 17a, and the entire area of the optical deflection array 17 corresponds to the entire area of the external measurement space. In FIG. 10, there are patterns (1) to (40) as patterns for determining which of the plurality of light deflection element groups is to be turned on. That is, each pattern corresponds to an optical deflection element group in which nine different 3×3 pixels (optical deflection elements 17a) are electrically connected in parallel. The number of patterns of 40 is shown provisionally, and is actually determined according to the number of light deflecting elements 17a included in the light deflecting element group and the number of pixels in the horizontal and vertical directions of the entire light deflecting array 17. It is. Also, the optical deflection element group is not limited to 3×3=9 pixels, and the optical deflection element group may be formed by pixel groups having different numbers of pixels in the horizontal direction and the vertical direction.

For each pattern defined in this way, the controller 21 sequentially switches from pattern (1) to pattern (40) as shown in FIG. The specifications of the operation of emitting laser light from the transmitter of the distance measuring device 1 depend on the configuration of each pattern, and may be determined according to the configuration of the pattern. As in the above-described embodiment, the light receiver 20 detects the ON light reflected at the detection point, which is the pixel where the light deflection element group that is ON in each pattern and the incident light area overlap. That is, the controller 21 can recognize that the light detected by the light receiver 20 at this timing is the ON light from the pixels where the incident light region overlaps with the light deflection element group that is ON-operated in the pattern. Therefore, a 3D map can be finally generated by using it as distance information to the point of the object corresponding to the ON light. In this case, the detection is not limited to the photodetector 20 configured with one photodiode, and detection may be performed with the photodetector 20 configured with several photodiodes.

The distance measuring device 1 according to Modification 1 as described above also has the same effect as the above-described embodiment.

(Modification 2)
A distance measuring device 1 as an example of a photodetector according to Modification 2 will be described, focusing on differences from the distance measuring device 1 according to the above-described embodiment.

11A and 11B are diagrams for explaining an example of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to Modification 2. FIG. FIG. 12 is a diagram showing an example of a timing chart of the operation of switching the pattern of the optical deflection element group to be turned on in the distance measuring device according to Modification 2. As shown in FIG. The switching operation of the pattern of the optical deflection element group to be turned on in this modified example will be described with reference to FIGS. 11 and 12 .

In FIG. 11, as an optical deflection element group in the optical deflection array 17, a region R1 formed by electrically connecting a central pixel group (optical deflection element 17a group) in parallel, and pixels positioned outside the region R1 are shown. A region R2 is formed by electrically connecting groups in parallel, and a region R3 is formed by electrically connecting pixel groups located outside the region R2 in parallel. A feature of this modification is that, unlike the above-described embodiment and modification 1, one light deflection element group corresponds to one pattern, but one pattern has one or more optical deflection element groups. The point is that the optical deflection element groups are made to correspond to each other. For example, in pattern (2), two optical deflection element groups of regions R1 and R2 are associated, and in pattern (3), three optical deflection element groups of regions R1 to R3 are associated. Furthermore, in pattern (18), in addition to regions R1 to R3, a region R11 including a plurality of light deflection element groups layered in patterns (4) to (17) is associated. . In the pattern (19), in addition to the regions R1 to R3 and R11, a region R12 including one or more light deflection element groups formed by electrically connecting pixel groups located outside the region R11 in parallel corresponds. I am letting Furthermore, pattern (20) includes, in addition to regions R1 to R3, R11, and R12, one or more light deflection element groups formed by electrically connecting pixel groups located outside region R12 in parallel. Region R13 is made to correspond.

That is, the pattern configuration described in the above-described embodiment and modification 1 is configured for the purpose of a rolling shutter effect in terms of a camera. This configuration is aimed at the effect of squeezing a cat's eye. The number of patterns of 20 is shown provisionally, and is actually determined according to the number of light deflection elements 17a included in the light deflection element group and the number of pixels in the horizontal and vertical directions of the entire light deflection array 17. It is.

For each pattern defined in this way, the controller 21 sequentially switches from pattern (1) to pattern (20) as shown in FIG. The specifications of the operation of emitting laser light from the transmitter of the distance measuring device 1 depend on the configuration of each pattern, and may be determined according to the configuration of the pattern. As in the above-described embodiment, the light receiver 20 detects the ON light reflected at the detection point, which is the pixel where the light deflection element group that is ON in each pattern and the incident light area overlap. That is, the controller 21 can recognize that the light detected by the light receiver 20 at this timing is the ON light from the pixels where the incident light region overlaps with the light deflection element group that is ON-operated in the pattern. Therefore, a 3D map can be finally generated by using it as distance information to the point of the object corresponding to the ON light. In this case, the detection is not limited to the light receiver 20 configured with one photodiode, and detection may be performed with the light receiver 20 configured with several photodiodes.

Here, FIG. 12 shows a timing chart of switching of each pattern. For example, the detection time for a specific incident light region, that is, the total detection time for patterns (1) to (20) is 166.7 [μsec]. If the area of the group of photodetecting elements that are ON in patterns (1) to (3) is small, the detection time may be short because the object is to perform distance measurement at a short distance by correlation with the lens. 2 [μsec]. In patterns (18) to (20) in the latter half, the detection time is set to 6 to 8 [μsec] because the purpose is to perform distance measurement at a long distance and the detection time is relatively long. At this time, the pattern configuration is such that the aperture is enlarged considering that the amount of light decreases due to the distance.

Thus, in this modification, the optical deflection array 17 can be used to adjust the aperture like a cat's eye diaphragm in a camera configuration at high speed. This can provide high performance photodetection.

(Modification 3)
A distance measuring device 1 as an example of a photodetector according to Modification 3 will be described, centering on the differences from the distance measuring device 1 according to the above-described embodiment.

13A and 13B are diagrams showing an example of a timing chart showing an operation of changing the laser intensity in the distance measuring device according to Modification 3. FIG. With reference to FIG. 13, the operation of changing the laser intensity for suppressing erroneous detection with another laser beam incident from the outside in the distance measuring device 1 according to this modification will be described.

For example, in the pattern configuration shown in FIG. 7 described above, when the distance measurement time for each pattern is 4 [μsec], assuming that the tilting operation of the optical deflection element 17a requires 1.5 [μsec], detection is possible. The time is the remaining 2.5 [μsec]. For example, 2 [μsec] is sufficient for distance measurement up to 300 [m] ahead. There is a need to. In particular, when the range finder 1 is mounted on a vehicle that operates automatically, for example, it is required that erroneous detection due to mixing with laser light from a range finder mounted on another vehicle can be suppressed.

Therefore, the range finder 1 according to the present modification converts the laser light into a nanosecond level pulse and changes at least one of the intensity and the phase in the middle of the output, thereby radiating from the range finder 1 itself. erroneous detection is suppressed by discriminating whether it is a laser beam that has been emitted or another laser beam. For example, as shown by the pulse-shaped waveform indicated by the dotted line in FIG. A laser beam with varying laser intensity is emitted. As a result, the reflected light from the object with respect to such a laser beam also has a similar intensity ratio. When detecting light with a different intensity ratio, it can be determined that it is a different laser beam, so accurate distance measurement is possible.

1 distance measuring device 11 laser light source 12 shaping lens 13 optical scanning device 14 reflecting mirror 15 vertical magnifying lens 16 imaging lens 17 optical deflection array 17a optical deflection element 18 light absorbing plate 19 imaging lens 20 light receiver 21 controller 31 substrate 32 wiring 33 insulating film 34 connection hole 35a, 35b electrode 36 contact member 37 fulcrum member 38 plate-shaped member 39 pillar 40 shade-shaped member 101 distance measuring device 101a photodetector 102 to 105, 111, 112 object 201 laser light source 202 shaping lens 203 polygon Mommirror 204 Lens 205 Imaging Lens 206 Light Receiver 211 Imaging Lens 212 DMD
212a optical deflection element 213 imaging lens 214 light receiver 301 mirror structure 302 SRAM
DP detection point ILA incident light area R1 to R3, R11 to R13 area

U.S. Patent Application Publication No. 2017/0357000

Claims (8)

a photodetector ,
a light guide section for guiding incident light , which is reflected light from an object incident from the outside world ;
a deflection section that deflects the incident light that has entered the light guide section and is guided by the light guide section;
a light receiving unit that detects a part of the incident light beam deflected by the deflecting unit;
with
The deflection unit has a plurality of optical deflection element groups including a plurality of optical deflection elements that deflect the incident light,
The optical deflection element group is configured by electrically connecting the plurality of optical deflection elements in parallel,
the plurality of optical deflection elements included in the optical deflection element group perform deflection operations simultaneously by passive matrix driving;
A photodetector in which the plurality of optical deflection element groups perform the deflection operation simultaneously or sequentially over time. The optical deflection element is
a substrate having a planar portion;
a plate-shaped member having a deflection surface that deflects the incident light;
a fulcrum member projecting from the planar portion and serving as a fulcrum of tilting motion of the plate-shaped member so as to freely come into contact with and separate from a surface of the plate-shaped member opposite to the deflection surface;
a shade-shaped member that regulates the arrangement of the plate-shaped member and allows the plate-shaped member to freely tilt by providing a gap between the plate-shaped member and the plate-shaped member;
a plurality of electrodes arranged symmetrically with respect to the fulcrum member on the planar portion;
with
2. The photodetector according to claim 1, wherein said plate-shaped member includes a conductive region facing said plurality of electrodes on said opposite surface. 3. The photodetector according to claim 2, wherein the deflection surface is a reflective surface. 4. The photodetector according to any one of claims 1 to 3, wherein the light receiving section is composed of a single light receiving element. Further comprising a light absorbing section for absorbing the incident light reflected by the optical deflection element when the incident light is incident in a state where the light deflection element does not reflect the incident light toward the light receiving section. Item 5. The photodetector according to any one of Items 1 to 4. a light source that emits laser light;
an optical scanning unit that deflects the laser light so as to scan in a first direction;
an optical system that emits the laser beam deflected by the optical scanning unit to the outside;
A photodetector according to any one of claims 1 to 5;
Range finder with. the optical system expands the laser beam reflected by the optical scanning unit in a direction intersecting the first direction and radiates it to the outside;
7. The distance measuring device according to claim 6, wherein the optical deflection element group is configured by arranging the plurality of optical deflection elements in the second direction. 8. The method according to claim 6 or 7, further comprising a generating unit that generates a three-dimensional image based on a distance obtained from the time from when the laser light is emitted from the light source until the light is detected by the light receiving unit. Range finder as described.

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