Measuring device

Abstract

To provide a photosensitive element capable of receiving a distorted focal spot.SOLUTION: A photosensitive element disclosed herein comprises a first light reception unit for detecting light irradiated to a first light reception window, and second light reception units for detecting light irradiated to second windows provided around the first light reception window.SELECTED DRAWING: Figure 6

Description

Technical Field

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[0001] The present invention relates to a light receiving element and a measuring device.

Background Art

[0002] In distance measurement systems such as LiDAR (Light Detection and Ranging), a TOF (Time of Flight) method for measuring the distance to an object is known, which measures the time from when a pulsed laser beam is projected until the reflected light is received. Also, in distance measurement systems such as LiDAR, laser light is scanned to perform measurements over a wide range. For example, Patent Document 1 describes a distance measurement system that two-dimensionally scans laser light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When mounting distance measurement systems such as LiDAR on a vehicle, it is necessary to arrange the light-emitting elements, photodetectors, and optical systems that constitute the distance measurement system in a confined space. Furthermore, when arranging multiple photodetectors in a single optical system, the photodetectors must be offset from the optical axis of the optical system. As a result, the distortion of the focused spot of reflected light on the photodetector's light-receiving surface becomes large, and there is a risk that the photodetector may not be able to properly receive the reflected light. In particular, when attempting to configure a distance measurement system that can measure distances over a wide range from short to long distances, the distortion of the focused spot on the photodetector's light-receiving surface becomes large under at least one measurement condition, and there is a risk that the photodetector may not be able to properly receive the reflected light (or, if the optical system is configured so that the focused spot illuminates the photodetector's light-receiving window under all measurement conditions, the optical system will become large, making it difficult to mount the distance measurement system on a vehicle).

[0005] The present invention aims to provide a light-receiving element capable of receiving a distorted light-gathering spot. [Means for solving the problem]

[0006] One aspect of the present invention for achieving the above objectives comprises: a plurality of light-emitting elements arranged in the X and Y directions and emitting light in the Z direction; an optical system having an optical axis along the Z direction; a plurality of light-receiving elements arranged in the X and Y directions, conjugate to a specific light-emitting element and the optical system, and receiving reflected light; and a controller that measures the coordinates in the Z direction by measuring the time from when the light-emitting element emits light until the light-receiving element receives the reflected light, wherein the light-receiving elements comprise a first light-receiving unit that outputs a first signal corresponding to light irradiated into a first light-receiving window, and a second light-receiving unit that outputs a second signal corresponding to light irradiated into a second light-receiving window provided around the first light-receiving window, and the controller measures the time based on the first signal of the first light-receiving unit and the second signal of the second light-receiving unit, wherein the first light-receiving unit has a wider dynamic range than the second light-receiving unit, and the second light-receiving unit has higher sensitivity than the first light-receiving unit. The first light-receiving window is larger than the second light-receiving window. This measuring device is characterized by the following features.

[0007] Further issues disclosed in this application, and methods for solving them, will be made clear in the section on embodiments for carrying out the invention and in the drawings. [Effects of the Invention]

[0008] According to the present invention, a light-receiving element becomes capable of receiving a distorted light-gathering spot. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an explanatory diagram of an example of a measuring device. [Figure 2] Figure 2 is an explanatory diagram of the mounting board 5 as viewed from the X direction. [Figure 3] Figure 3A is an explanatory diagram of 2D scanning. Figure 3B is an explanatory diagram of 2D scanning in a certain frame. Figure 3C is an explanatory diagram of 2D scanning using multiple channels. [Figure 4] Figure 4A is a top view of the comparative example light-receiving element 20. Figure 4B is a cross-sectional view of an example of the light-receiving portion of the light-receiving element. [Figure 5] Figure 5A is an explanatory diagram of the light collection process by the light-receiving optical system 32. Figure 5B is an explanatory diagram of the light-receiving window 22 and the light-collecting spot on the light-receiving element 20 on the optical axis of the light-receiving optical system 32. Figure 5C is an explanatory diagram of the light-receiving window 22 and the light-collecting spot on the light-receiving element 20 located off-axis from the optical axis of the light-receiving optical system 32. [Figure 6] Figure 6A is an explanatory diagram of an example of the light-receiving element of this embodiment. Figure 6B is an explanatory diagram of the light-receiving window 22 (first light-receiving window 22A and second light-receiving window 22B) and the light-collecting spot in the light-receiving element 20 of this embodiment. [Figure 7] Figures 7A and 7B are explanatory diagrams of the output signals of the photodetector 20. [Figure 8] Figure 8A is an explanatory diagram of an example of a photodetector using the photodetector of this embodiment. Figure 8B is an explanatory diagram of another example of a photodetector. [Figure 9] Figure 9 is an explanatory diagram of an example of a photodetector using a modified photodetector. [Figure 10] Figs. 10A to 10F are explanatory diagrams of examples of the first light receiving window 22A and the second light receiving window 22B. [Figure 11] Figs. 11A to 11D are explanatory diagrams of another example of the first light receiving window 22A and the second light receiving window 22B. [Figure 12] Fig. 12 is an explanatory diagram of an example of a light receiving element array.

Embodiments for Carrying out the Invention

[0010] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following description, the same or similar configurations may be denoted by common reference numerals and redundant descriptions may be omitted.

[0011] <Regarding the measuring device> Fig. 1 is an explanatory diagram of an example of a measuring device.

[0012] In the following description, as shown in Fig. 1, each direction is defined. The direction along the optical axis (the axis of rotational symmetry of the lens) of the light receiving optical system 32 (or the light projecting optical system 31) is defined as the Z direction. Note that the object 90 to be measured by the measuring device 1 is separated from the measuring device 1 in the Z direction. Also, the direction perpendicular to the Z direction and in which the light projecting optical system 31 and the light receiving optical system 32 are arranged is defined as the X direction. Further, the direction perpendicular to the Z direction and the X direction is defined as the Y direction.

[0013] The measuring device 1 is a device for measuring the surface of the object 90. Specifically, the measuring device 1 is a device that emits laser light (Tx in Fig. 1) from the light emitting element 10, detects the reflected light (Rx in Fig. 1) reflected by the surface of the object 90 with the light receiving element 20, and calculates the distance to the object 90 based on the detection result. The measuring device 1 includes a light emitting element 10, a light receiving element 20, an optical system 30, and a controller 40. Also, the measuring device 1 includes a mounting substrate 5 having a plurality of light emitting elements 10 and a plurality of light receiving elements 20, and a driving device 45.

[0014] The light-emitting element 10 is an element that converts an electrical signal into an optical signal. For example, the light-emitting element 10 is an LD chip (LD: Laser Diode) that emits laser light. In the present embodiment, the light-emitting element 10 emits pulsed light (Tx in FIG. 1) toward the surface of the object 90. The light-emitting element 10 of the present embodiment is composed of an edge-emitting semiconductor laser, is surface-mounted on the mounting substrate 5, and emits laser light parallel to the substrate surface. Note that the light-emitting element 10 is not limited to an edge-emitting semiconductor laser, and the mounting method on the mounting substrate 5 is not limited to this either.

[0015] The light-receiving element 20 is an element that converts an optical signal into an electrical signal. For example, the light-receiving element 20 is a PD chip (Photodiode). The detailed configuration of the light-receiving element 20 will be described later. The light-receiving element 20 is mounted in a state where the light-receiving surface is perpendicular to the substrate surface of the mounting substrate 5 so that the reflected light is incident on the light-receiving surface. Note that the mounting method of the light-receiving element 20 is not limited to this.

[0016] The optical system 30 is an optical system for irradiating the object 90 with the light output from the light-emitting element 10 and for causing the light-receiving element 20 to receive the reflected light from the object 90. The light-emitting element 10 and the light-receiving element 20 are arranged at conjugate positions with respect to the optical system 30. The optical system 30 of the present embodiment includes a light-projecting optical system 31 and a light-receiving optical system 32.

[0017] The light-projecting optical system 31 is an optical system for irradiating the object 90 with the light output from the light-emitting element 10. The light-emitting element 10 is arranged within the focal plane of the light-projecting optical system 31. The light-projecting optical system 31 irradiates the object 90 with the laser light emitted from the light-emitting element 10 as collimated light. The collimated light is irradiated in a predetermined direction (predetermined angle) according to the positional relationship between the light-emitting element 10 and the light-projecting optical system 31. The light-emitting element 10 irradiates the object 90 with light via the light-projecting optical system 31. The light-projecting optical system 31 is each composed of a lens group including a plurality of (for example, 5 to 7) lenses (in FIG. 1, the lens group of the light-projecting optical system 31 is simply shown).

[0018] The light-receiving optical system 32 is an optical system for receiving reflected light from the object 90 onto the light-receiving element 20. The light-receiving surface of the light-receiving optical system 32 is positioned within the focal plane of the light-receiving optical system 32. The light-receiving optical system 32 focuses the reflected light from the object 90 onto the light-receiving surface of a predetermined light-receiving element 20. The light-receiving element 20 receives the reflected light from the object 90 via the light-receiving optical system 32. The light-receiving optical system 32, like the light-emitting optical system 31, is each composed of a lens group consisting of multiple lenses (for example, 5 to 7 lenses) (Figure 1 shows a simplified representation of the lens group of the light-receiving optical system 32).

[0019] The light-emitting optical system 31 and the light-receiving optical system 32 are integrally constructed, and their relative positions are fixed. Specifically, the light-emitting lens barrel that constitutes the light-emitting optical system 31 and the light-receiving lens barrel that constitutes the light-receiving optical system 32 are fixed to a common optical frame 33.

[0020] The controller 40 is a control unit that manages the measurement device 1. The controller 40 controls the emission of laser light from the light-emitting element 10. The controller 40 also calculates the distance to the object 90 based on the output signal of the light-receiving element 20. Specifically, the controller 40 measures the distance to the object 90 by measuring the time from when the light-emitting element 10 emits pulsed laser light until the light-receiving element 20 receives the reflected light. In other words, the controller 40 measures the distance to the object 90 using the TOF (Time of Flight) method by controlling the light-emitting element 10 and the light-receiving element 20 (measuring the Z coordinate of the surface of the object 90). Furthermore, by utilizing the fact that laser light is irradiated in a predetermined direction and reflected light is received in a predetermined direction, the controller 40 can measure the X, Y, and Z coordinates of the surface of the object 90 by scanning in the X and Y directions and measuring the Z coordinate of the surface of the object 90.

[0021] The controller 40 includes an arithmetic unit 41 and a storage device 42. The arithmetic unit 41 is an arithmetic processing unit such as a CPU or GPU. The storage device 42 consists of a main memory and an auxiliary memory and is a device for storing programs and data. By executing the program stored in the storage device 42, the arithmetic unit 41 controls the emission of laser light from the light-emitting element 10 and calculates the distance to the object 90 based on the output signal of the photodetector 20. The arithmetic unit 41 also calculates the X, Y, and Z coordinates of the surface of the object 90 based on the output signal of the photodetector 20. The arithmetic unit 41 may store the acquired coordinate data in the storage device 42 or in an external storage device. The data of the X, Y, and Z coordinates of numerous points on the surface of the object 90 becomes data representing a three-dimensional image (point cloud) of the surface of the object 90. The arithmetic unit 41 may perform an analysis of the object 90 based on the three-dimensional image stored in the storage device 42 by executing a program stored in the storage device 42.

[0022] The mounting substrate 5 is a substrate on which multiple light-emitting elements 10 and multiple light-receiving elements 20 are mounted. A certain light-receiving element 20 is associated with a specific light-emitting element 10, and the detection position of a certain light-receiving element 20 is conjugate to the light-emitting position of a specific light-emitting element 10. In this embodiment, there are multiple pairs of light-emitting elements 10 and light-receiving elements 20, and the surface of the object 90 can be measured with multiple channels. The light-emitting elements 10 emit laser light parallel to the substrate surface of the mounting substrate 5, and the light-receiving elements 20 receive light (reflected light) incident from a direction approximately parallel to the substrate surface of the mounting substrate 5.

[0023] As shown in Figure 1, the mounting substrate 5 has five light-emitting elements 10 and five light-receiving elements 20. However, the number of light-emitting elements 10 and light-receiving elements 20 is not limited to these. Multiple light-emitting elements 10 are arranged at different positions in the X direction on the mounting substrate 5. Also, multiple light-receiving elements 20 are arranged at different positions in the X direction on the mounting substrate 5.

[0024] As shown in Figure 1, the mounting substrate 5 is provided with a light-emitting curved portion 6 and a light-receiving curved portion 7. The light-emitting curved portion 6 is a part having an arc-shaped edge. The light-emitting curved portion 6 is a part for arranging multiple light-emitting elements 10 so as to follow the curvature of the image plane of the light-projection optical system 31. Multiple light-emitting elements 10 are arranged along the arc-shaped edge of the light-emitting curved portion 6. As a result, each light-emitting element 10 is positioned at an appropriate position and angle with respect to the light-projection optical system 31, and the effect of the image plane curvature of the light-projection optical system 31 can be reduced. The light-receiving curved portion 7 is a part having an arc-shaped edge and is located at a different position in the X direction from the light-emitting curved portion 6. The light-receiving curved portion 7 is a part for arranging multiple light-receiving elements 20 so as to follow the curvature of the image plane of the light-receiving optical system 32. Multiple light-receiving elements 20 are arranged along the arc-shaped edge of the light-receiving curved portion 7. As a result, each light-receiving element 20 is positioned at an appropriate position and angle with respect to the light-receiving optical system 32, and the effect of the image plane curvature of the light-receiving optical system 32 can be reduced. However, the mounting substrate 5 does not necessarily need to have a light-emitting curved portion 6 or a light-receiving curved portion 7. In this case, multiple light-emitting elements 10 and multiple light-receiving elements 20 will be arranged along the edge of the mounting substrate 5 perpendicular to the Z direction.

[0025] Figure 2 is an explanatory diagram of the mounting substrate 5 as viewed from the X direction. For explanatory purposes, the light-emitting side curved portion 6 and the light-receiving side curved portion 7 of the mounting substrate 5 are omitted, and it is assumed that the light-emitting element 10 and the light-receiving element 20 are arranged along the edge of the mounting substrate 5 parallel to the X direction. For explanatory purposes, the inclination of the mounting substrate 5 is exaggerated in this diagram.

[0026] As shown in Figure 2, the measuring device 1 has multiple mounting boards 5 (in this case, three mounting boards 5). The multiple mounting boards 5 are arranged at different positions in the Y direction. As shown in Figure 1, each mounting board 5 has multiple (in this case, five) light-emitting elements 10 and multiple light-receiving elements 20 arranged at different positions in the X direction. Therefore, a light-emitting element array is formed by arranging multiple (in this case, fifteen) light-emitting elements 10 in the X and Y directions, and a light-receiving element array is formed by arranging multiple light-receiving elements 20 in the X and Y directions. Here, the surface of the object 90 will be measured with 5 × 3 = 15 channels (5 channels in the X direction and 3 channels in the Y direction).

[0027] Multiple mounting substrates 5 are arranged at different angles with respect to the Z direction. Specifically, as shown in Figure 2, each mounting substrate 5 is arranged at a different angle with respect to the Z direction such that the light-emitting element 10 of each substrate 5 faces the light-emitting optical system 31, and the light-receiving surface of the light-receiving element 20 of each substrate 5 faces the light-receiving optical system 32. This ensures that the light-emitting element 10 and the light-receiving element 20 are positioned at appropriate positions and angles relative to the optical system 30, thereby reducing the effect of image field curvature of the optical system 30. The light-emitting element 10 of each mounting substrate 5 is arranged to emit laser light parallel to the substrate surface of the substrate 5. The light-receiving element 20 of each mounting substrate 5 is arranged to receive light (reflected light) incident from a direction approximately parallel to the substrate surface of the substrate 5. Since multiple (in this case, five) light-emitting elements 10 and multiple (in this case, five) light-receiving elements 20 are mounted on the same substrate, and since the light-emitting optical system 31 and the light-receiving optical system 32 are provided separately, even if the mounting substrate 5 is tilted in the Z direction (the direction of the optical axis of the optical system 30), each light-emitting element 10 and light-receiving element 20 can be maintained in a conjugate positional relationship with respect to the optical system 30. Furthermore, if the mounting substrate 5 is provided with a light-emitting side curvature 6 and a light-receiving side curvature 7, as in this embodiment, even if the mounting substrate 5 is tilted, it is easy to arrange multiple light-emitting elements along the image plane curvature of the light-emitting optical system 31, and it is easy to arrange multiple light-receiving elements 20 along the image plane curvature of the light-receiving optical system 32.

[0028] Furthermore, multiple mounting boards 5 may be arranged parallel to each other in the Z direction. However, if each mounting board 5 is arranged parallel to each other, the position and angle of the light-emitting element 10 and the light-receiving element 20 relative to the mounting board 5 must be different for each mounting board 5 so that the light-emitting element 10 and the light-receiving element 20 are at an appropriate position and angle with respect to the optical system 30. In contrast, in this embodiment, since the inclination of the mounting boards 5 is different, in each mounting board 5, the light-emitting element 10 can be configured to emit laser light parallel to the mounting board 5, and the light-receiving element 20 can be configured to receive light (reflected light) incident from a direction approximately parallel to the mounting board 5. For this reason, in this embodiment, multiple light-emitting elements 10 and multiple light-receiving elements 20 can be arranged at different positions in the X and Y directions, at an appropriate position and angle with respect to the optical system 30, with a simple configuration.

[0029] Multiple (in this case, three) mounting boards 5 are fixed together as a single unit, and their relative positions are fixed. Specifically, the multiple mounting boards 5 are fixed to a common board frame 8. However, the relative positions of the multiple light-emitting elements 10 and the multiple light-receiving elements 20 can be fixed by other means, as long as the relative positions of the multiple light-emitting elements 10 and the multiple light-receiving elements 20 can be fixed. Also, the measuring device 1 does not necessarily have to be equipped with multiple mounting boards 5.

[0030] The drive device 45 (see Figure 1) is a device that moves the optical system 30 and the mounting substrate 5 (light-emitting element 10 and light-receiving element 20) relative to each other in the XY direction. By moving the optical system 30 and the mounting substrate 5 relative to each other in the XY direction, the drive device 45 changes the positional relationship of the light-emitting element 10 with respect to the optical system 30, changing the angle at which the laser light is irradiated, thereby allowing the laser light to be scanned.

[0031] The drive unit 45 moves at least one of the optical system 30 and the mounting substrate 5 (either one of the optical system 30 and the mounting substrate 5, or both of the optical system 30 and the mounting substrate 5). The drive unit 45 may move the optical system 30 relative to the mounting substrate 5 in the XY direction, or move the optical system 30 relative to the mounting substrate 5 in the XY direction, or move the optical system 30 in the X direction (or Y direction) while moving the mounting substrate 5 in the Y direction (or X direction). In this embodiment, at least one of the optical frame 33 and the substrate frame 8 is supported by the housing 3 at predetermined resonant frequencies in the X and Y directions, respectively, and the drive unit 45 vibrates at least one of the optical system 30 and the mounting substrate 5 in the X and Y directions at their respective resonant frequencies. The drive unit 45 is composed of, for example, a voice coil motor, but is not limited to this (for example, it may be composed of a piezoelectric element).

[0032] Figure 3A is an explanatory diagram of two-dimensional scanning. In this embodiment, by vibrating at least one of the optical system 30 and the mounting substrate 5 in the X and Y directions at their respective resonant frequencies, the optical system 30 and the mounting substrate 5 (light-emitting element 10 or photodetector 20) are displaced relative to each other in the X and Y directions along a Lissajous curve as shown in Figure 3A. The Lissajous curve is a graph of X = Asin(at + δ), Y = Bsin(bt). Here, a and b are the frequencies in the X and Y directions, respectively, t is time, and δ is the phase difference. As already explained, since at least one of the optical frame 33 and the substrate frame 8 is supported in the X and Y directions at predetermined resonant frequencies, a and b are known values. Furthermore, A and B become known values ​​when the drive device 45 resonates the optical frame 33 or the substrate frame 8 with a predetermined amplitude, and δ becomes a known value based on the drive timing in the X and Y directions by the drive device 45. Therefore, the controller 40 can calculate the XY positions of the two pairs of light-emitting elements 10 (or light-receiving elements 20) in the optical system 30 based on time t. In other words, the controller 40 can calculate the direction in which the laser light is emitted based on time t. Alternatively, instead of calculating the direction in which the laser light is emitted based on time t, the controller 40 may detect the relative position in the XY directions between the optical frame 33 and the substrate frame 8 using a position detector (not shown), and calculate the direction in which the laser light is emitted based on this detection result.

[0033] Figure 3B is an explanatory diagram of a two-dimensional scan in a given frame. The controller 40 acquires one frame (one three-dimensional image of the object 90) at predetermined time intervals. For each measurement of one frame (one three-dimensional image), the X, Y, and Z coordinates of the surface of the object 90 are measured at multiple points on the Lissajous curve. This makes it possible to measure coordinates with increased resolution. The same Lissajous curve may be repeated for each frame. In this case, it becomes possible to measure the surface of the object 90 at the same position in each frame. On the other hand, the Lissajous curve may be shifted for each frame. In this case, it becomes possible to measure the surface of the object 90 in the next frame by interpolating between the point clouds measured in the previous frame.

[0034] Figure 3C is an explanatory diagram of two-dimensional scanning using multiple channels. As shown in the figure, in this embodiment, two-dimensional scanning is performed in different ranges for each channel. This makes it possible to measure the surface of the object 90 over a wide range in the X and Y directions, thereby achieving a wide FOV (field of view).

[0035] Note that the two-dimensional scanning does not necessarily have to be performed along the Lissajous curve. For example, two-dimensional scanning may be performed by performing line scanning in the X direction (or Y direction) multiple times, shifting it in the Y direction (or X direction). Alternatively, only one-dimensional scanning may be performed instead of two-dimensional scanning. Furthermore, scanning may not be performed at all. If scanning is not performed, the measuring device 1 does not need to be equipped with a drive device 45. However, if scanning is not performed, the resolution of the point cloud will be reduced compared to this embodiment.

[0036] <About the light-receiving element> First, a comparative example of a light-receiving element will be described, and then the light-receiving element of this embodiment will be described.

[0037] Figure 4A is a top view of the comparative example light-receiving element 20. Figure 4B is a cross-sectional view of an example of the light-receiving portion of the light-receiving element.

[0038] The light-receiving element 20 has a light-receiving window 22 for receiving light. The light-receiving window 22 is a light-receiving region provided on the light-receiving surface of the light-receiving element 20. For example, if the light-receiving element 20 is an avalanche photodiode (APD), the light-receiving portion 21 of the light-receiving element 20 has a buffer layer, a light-absorbing layer, an intermediate layer, a doubling layer, and a window layer on the substrate, and further has a light-receiving region and a guard ring around the outer periphery of the light-receiving region, and has electrodes 23 and electrodes 24 on the front and back surfaces of the substrate, respectively (the first light-receiving portion 21A and the second light-receiving portion 21B described later are similar). In addition, a protective layer is formed on the light-receiving surface of the light-receiving element 20. Here, the light-receiving window 22 corresponds to the region inside the annular electrode 23 (electrode on the light-receiving surface side; electrode on the substrate surface side). The diameter of the light-receiving window 22 is sometimes called the light-receiving diameter. The size of the photodetector 20 is several millimeters square (for example, 5 mm square), while the light-receiving diameter is, for example, 500 μm. However, the size of the photodetector 20 and the light-receiving diameter are not limited to these.

[0039] As shown in Figure 4A, the comparative example's light-receiving element 20 has one light-receiving window 22 located in the center of the chip that constitutes the light-receiving element 20. The light-receiving window 22 of the comparative example's light-receiving element 20 is only one, located in the center of the chip.

[0040] Figure 5A is an explanatory diagram of the light collection process by the light-receiving optical system 32. Figure 5B is an explanatory diagram of the light-receiving window 22 and the light-collecting spot on the light-receiving element 20 on the optical axis of the light-receiving optical system 32. Figure 5C is an explanatory diagram of the light-receiving window 22 and the light-collecting spot on the light-receiving element 20 located off-axis from the optical axis of the light-receiving optical system 32.

[0041] Since multiple photodetectors 20 are arranged for a single photodetector optical system 32, as shown in Figure 5A, in addition to the photodetectors 20 arranged on the optical axis of the photodetector optical system 32, there are also photodetectors 20 positioned off-axis. In Figure 5A, only one photodetector 20 off-axis of the photodetector optical system 32 is depicted, but there are multiple photodetectors 20 off-axis of the photodetector optical system 32, and furthermore, the degree to which they are off-axis from the optical axis of the photodetector optical system 32 differs from one another (see Figure 12, described later).

[0042] As shown in Figure 5B, for a photodetector 20 positioned on the optical axis, the focused spot of reflected light collected by the photodetector 32 is approximately circular and located inside the photodetector window 22. On the other hand, as shown in Figure 5C, for a photodetector 20 positioned off-axis, the focused spot of reflected light collected by the photodetector 32 is distorted into an ellipse. The distortion of the focused spot is not limited to an ellipse and varies depending on the configuration of the photodetector 32 and the angle of light. For example, the focused spot may be distorted into various shapes such as a circular spot with a tail (comet shape), a band, or an arc shape. Even when a photodetector 20 is provided in the aforementioned curved part 7 on the photodetector side, the distortion of the focused spot cannot be completely eliminated for a photodetector 20 positioned off-axis, and the focused spot will still be distorted.

[0043] As shown in the comparative example in Figure 4A, if the light-receiving element 20 has only one light-receiving window 22, as shown in Figure 5C, if the distortion of the light-gathering spot becomes large, a portion of the light-gathering spot may fall outside the light-receiving window 22. Then, as shown in Figure 5C, if a portion of the light-gathering spot falls outside the light-receiving window 22, the light energy received by the light-receiving element 20 decreases, and as a result, the light-receiving element 20 may not be able to properly detect the reflected light.

[0044] Figure 6A is an explanatory diagram of an example of the light-receiving element of this embodiment. Figure 6B is an explanatory diagram of the light-receiving window 22 (first light-receiving window 22A and second light-receiving window 22B) and the light-collecting spot in the light-receiving element 20 of this embodiment.

[0045] As shown in Figure 6A, the light-receiving surface of the light-receiving element 20 of this embodiment is provided with a first light-receiving window 22A and a second light-receiving window 22B. The first light-receiving window 22A and the second light-receiving window 22B are each provided with a light-receiving unit 21 (see Figure 4B). In the following description, the light-receiving unit 21 having the first light-receiving window 22A will be referred to as the "first light-receiving unit," and the light-receiving unit 21 having the second light-receiving window 22B will be referred to as the "second light-receiving unit." The light-receiving element 20 of this embodiment has a first light-receiving unit 21A that detects light irradiated onto the first light-receiving window 22A, and a second light-receiving unit 21B that detects light irradiated onto the second light-receiving window 22B. The first light-receiving window 22A and the second light-receiving window 22B may be referred to as the "main light-receiving window" and the "sub light-receiving window," respectively, and the first light-receiving unit 21A and the second light-receiving unit 21B may be referred to as the "main light-receiving unit" and the "sub light-receiving unit," respectively.

[0046] As already explained, in the case of a light-receiving element 20 positioned off-axis, the focused spot of reflected light collected by the light-receiving optical system 32 may be distorted. With the light-receiving element 20 of this embodiment, as shown in Figure 6B, even if a part of the focused spot is outside the first light-receiving window 22A, the focused spot is illuminated by the second light-receiving window 22B, making it possible for the second light-receiving unit 21B to detect the reflected light.

[0047] Figures 7A and 7B are explanatory diagrams of the output signals of the photodetector 20. The upper graph in each figure shows the current output from the first photodetector 21A, and the lower graph shows the current output from the second photodetector 21B. The current output from the photodetector 20 may be positive or negative (as described later). In the following explanation, the signal output from the first photodetector 21A will be referred to as the first signal, and the signal output from the second photodetector 21B will be referred to as the second signal. The first photodetector 21A outputs a current (first signal) corresponding to the light irradiated onto the first light-receiving window 22A. The second photodetector 21B outputs a current (second signal) corresponding to the light irradiated onto the second light-receiving window 22B.

[0048] Figure 7A is an explanatory diagram of the first and second signals when the light-gathering spot is located inside the first light-receiving window 22A. As already explained, in this embodiment, the light-emitting element 10 emits pulsed light (Tx in Figure 1), so that the focused spot of pulsed reflected light (Rx in Figure 1) is irradiated onto the light-receiving element 20. When the focused spot is located inside the first light-receiving window 22A, sufficient amount of reflected light is irradiated onto the first light-receiving window 22A, so the first light-receiving unit 21A outputs a relatively large pulsed current (first signal), as shown in the upper graph of Figure 7A. In this case, the controller 40 can determine the time t for receiving the pulsed reflected light based on the first signal. In other words, the controller 40 can measure the time from when the light-emitting element 10 emits pulsed laser light until the light-receiving element 20 receives the reflected light, and can measure the distance to the object 90.

[0049] Figure 7B is an explanatory diagram of the first and second signals when a portion of the light-gathering spot is outside the first light-receiving window 22A. When a portion of the focused spot moves away from the first light-receiving window 22A (see Figure 6B), the pulsed current of the first signal decreases, as shown in the upper graph of Figure 7A. On the other hand, when the focused spot of pulsed reflected light irradiates the second light-receiving window 22B, the second signal becomes a pulsed signal. Since the pulsed focused spot irradiates both the first light-receiving window 22A and the second light-receiving window 22B simultaneously, the timing of the pulses in the second signal indicates the timing of the reception of pulsed reflected light. Therefore, the controller 40 can determine the time t of the reception of pulsed reflected light based on the second signal. In other words, even if the current of the first signal is too weak to determine time t based on the first signal, the controller 40 can measure the time from when the light-emitting element 10 emits pulsed laser light until the light-receiving element 20 receives the reflected light, based on the second signal, and measure the distance to the object 90.

[0050] Incidentally, the light-receiving optical system 32 is designed so that light is mainly focused on the first light-receiving window 22A of the light-receiving element 20 (see Figure 5B). Therefore, under the main measurement conditions, the amount of light irradiated onto the first light-receiving window 22A is relatively large. In contrast, the second light-receiving window 22B is intended to detect a portion of the light from the distorted focused spot, so the amount of light irradiated onto the second light-receiving window 22B is relatively small. Therefore, in this embodiment, the second light-receiving unit 21B having the second light-receiving window 22B is configured to have higher sensitivity than the first light-receiving unit 21A having the first light-receiving window 22A. In other words, the second light-receiving unit 21B is configured to output a high current relative to the amount of light received (see the lower part of Figure 7B). As a result, in this embodiment, reflected light is more easily detected by the second light-receiving unit 21B.

[0051] Furthermore, since the intensity of reflected light differs depending on the distance to the object 90, the first light-receiving unit 21A is configured to have a wide dynamic range so that it can output detection signals corresponding to different light intensities. Generally, a wider dynamic range makes it difficult to output a strong current with a weak amount of received light, resulting in lower sensitivity. On the other hand, the second light-receiving unit 21B only needs to detect a portion of the light in the distorted focused spot, so a wide dynamic range is not required. For this reason, it is permissible to configure the second light-receiving unit 21B to have higher sensitivity than the first light-receiving unit 21A. Furthermore, generally, when a relatively wide dynamic range is configured, the light-receiving window is configured to be relatively large, and when a relatively high sensitivity is configured, the light-receiving window is configured to be relatively small. For this reason, it is generally difficult to configure the light-receiving element 20 to achieve both a wide dynamic range and high sensitivity. However, in this embodiment, since the first light-receiving unit 21A and the second light-receiving unit 21B are configured separately, it is possible to configure the first light-receiving unit 21A to have a wide dynamic range and the second light-receiving unit 21B to have high sensitivity. For this reason, in this embodiment, the first light-receiving unit 21A is configured to be larger than the second light-receiving window 22B. This makes it possible to widen the dynamic range of the first signal output by the first light-receiving unit 21A while increasing the current of the second signal output by the second light-receiving unit 21B. The size of the light-receiving window 22 is determined by the diameter (light-receiving diameter) if the light-receiving window 22 is circular, and by the area of ​​the light-receiving window 22 if the light-receiving window 22 is non-circular.

[0052] In this embodiment, multiple second light-receiving windows 22B are provided (two in Figure 6A). This makes it easier to detect reflected light by the second light-receiving windows 22B even if the light-gathering spot is distorted in different directions depending on the conditions (even if the light-gathering spot deviates in a different direction from the first light-receiving window 22A). In this embodiment, there are two second light-receiving windows 22B, but the number of second light-receiving windows 22B is not limited to two (as will be discussed later).

[0053] Figure 8A is an explanatory diagram of an example of a photodetector using the photodetector of this embodiment. For example, the aforementioned mounting substrate 5 is provided with a circuit for configuring the photodetector 50 shown in Figure 8A.

[0054] The light detection device 50 includes the above-mentioned light-receiving element 20 and a conversion unit 51. The conversion unit 51 is a circuit that converts the signal output from the light-receiving element 20 from current to voltage. The light detection device 50 has a conversion unit 51 for each light-receiving element 20. The conversion unit 51 shown in Figure 8A includes a first conversion unit 51A and a second conversion unit 51B. The first conversion unit 51A is a circuit that converts the first signal output from the first light-receiving unit 21A from current to voltage. The second conversion unit 51B is a circuit that converts the second signal output from the second light-receiving unit 21B from current to voltage. The first conversion unit 51A and the second conversion unit 51B are composed of a transimpedance amplifier (TIA).

[0055] The light detection device 50 has an analog-to-digital conversion circuit 52 (ADC). Here, an analog-to-digital conversion circuit 52 (ADC) is provided in each of the first conversion unit 51A and the second conversion unit 51B. Each analog-to-digital conversion circuit 52 converts the voltage (analog signal) output from the first conversion unit 51A or the second conversion unit 51B into a digital signal and outputs a signal to the controller 40 (arithmetic unit 41). The controller 40 (arithmetic unit 41) compares the voltage value of at least one of the first signal and the second signal with a threshold to determine the time t when the pulsed reflected light is received (see Figures 7A and 7B), calculates the time from when the light-emitting element 10 emits pulsed laser light until the light-receiving element 20 receives the reflected light, and calculates the distance to the object 90.

[0056] Figure 8B is an explanatory diagram of another example of a light detection device. Here, the conversion unit 50 adds the voltages output from the first conversion unit 51A and the second conversion unit 51B using the voltage summing unit 53. The analog-to-digital conversion circuit 52 converts the voltage (analog signal) output from the voltage summing unit 53 into a digital signal and outputs the signal to the controller 40 (arithmetic unit 41). The controller 40 determines the time t when pulsed reflected light was received by comparing the sum of the voltages of the first signal and the second signal with a threshold value. In this way, it is also possible to determine the time t when pulsed reflected light was received based on the first signal and the second signal.

[0057] Figure 9A is an explanatory diagram of an example of a photodetector using a modified photodetector.

[0058] The modified photodetector 20 outputs a current I which is the sum of the current I1 from the first photodetector 21A and the current I2 from the second photodetector 21B. In Figure 9A, the direction of the current when a positive current is output is indicated by an arrow, but as will be described later, there are also cases where a negative current (a current in the opposite direction to the arrow in the figure) is output. As already explained, when a portion of the focused spot moves outside the first light-receiving window 22A (see Figure 6B), the pulsed current I1 of the first signal decreases, as shown in the upper graph of Figure 7A. However, when the focused spot of pulsed reflected light illuminates the second light-receiving window 22B, a pulsed current I2 is generated as the second signal, as shown in the lower graph of Figure 7B. Since the pulses of the first signal and the pulses of the second signal are at the same timing, the light-receiving element 20 can output a relatively large pulsed current I from the signal line 25 even when a portion of the focused spot moves outside the first light-receiving window 22A.

[0059] Figures 9B and 9C are explanatory diagrams illustrating the connection between a modified photodetector and a conversion unit 51 (transimpedance amplifier).

[0060] Figure 9B shows an example of a modified photodetector. In this configuration, the anode of the first photodetector 21A and the anode of the second photodetector 21B are connected to the conversion unit 51 (transimpedance amplifier) ​​via the signal line 25. In this configuration, the current I, which is the sum of the positive current I1 of the first photodetector 21A and the positive current I2 of the second photodetector 21B, flows through the signal line 25. In this case, the positive current I is output from the photodetector 20.

[0061] Figure 9C shows another example of a modified photodetector. Here, the cathode of the first photodetector 21A and the cathode of the second photodetector 21B are connected to the conversion unit 51 via the signal line 25. In this configuration, the current I, which is the sum of the negative current I1 of the first photodetector 21A and the negative current I2 of the second photodetector 21B, flows through the signal line 25. In other words, in this case, a negative current I is output from the photodetector 20 (the photodetector 20 absorbs current I from the conversion unit 51).

[0062] By using the modified photodetector 20 shown in Figures 9A to 9C, the number of signal lines outputting signals from the photodetector 20 can be reduced. Furthermore, by using the modified photodetector 20, the number of transimpedance amplifiers (TIAs) and analog-to-digital converters (ADCs) in the photodetector 50 can be reduced.

[0063] Figures 10A to 10F are explanatory diagrams illustrating examples of the first light-receiving window 22A and the second light-receiving window 22B. The light-receiving element 20 shown in Figures 10A to 10F has a first light-receiving window 22A and two second light-receiving windows 22B. The first light-receiving window 22A is located in the center of the light-receiving surface of the light-receiving element 20, and the two second light-receiving windows 22B are located around the first light-receiving window 22A. Note that "around the first light-receiving window 22A" means the area outside the outer circumference of the first light-receiving window 22A and inside the outer edge of the chip on which the first light-receiving window 22A is provided. In Figures 10A to 10F, the two second light-receiving windows 22B are arranged so as to sandwich the first light-receiving window 22A. By arranging multiple second light-receiving windows 22B on either side of the first light-receiving window 22A, it becomes easier to detect reflected light with the second light-receiving windows 22B even when, under certain measurement conditions, the focused spot is distorted to deviate from the first light-receiving window 22A in a predetermined direction (e.g., the +Y direction), and under other measurement conditions, the focused spot is distorted to deviate from the first light-receiving window 22A in the opposite direction (e.g., the -Y direction). Alternatively, by arranging multiple second light-receiving windows 22B on either side of the first light-receiving window 22A, it becomes easier to detect reflected light with the second light-receiving windows 22B even when the focused spot is distorted in a band shape, causing it to be significantly distorted so that it straddles the first light-receiving window 22A.

[0064] As shown in Figures 10A to 10C (or Figures 10D to 10F), the direction in which the two second light-receiving windows 22B sandwich the first light-receiving window 22A may be in the X direction, the Y direction, or a direction intersecting both the X and Y directions. Also, as shown in Figure 10C, arranging the first light-receiving window 22A and the two second light-receiving windows 22B on the diagonals of the rectangular light-receiving surface makes it easier to arrange the first light-receiving window 22A and the two second light-receiving windows 22B in the limited space of the light-receiving surface (as a result, it is possible to miniaturize the chip of the light-receiving element 20). Note that the two second light-receiving windows 22B do not necessarily have to be arranged so as to sandwich the first light-receiving window 22A. For example, both of the two second light-receiving windows 22B may be arranged in the +Y direction relative to the first light-receiving window 22A.

[0065] As already explained, in order to widen the dynamic range of the first light-receiving unit 21A and increase the sensitivity of the second light-receiving unit 21B, it is desirable that the first light-receiving window 22A be larger than the second light-receiving window 22B, as shown in Figures 10A to 10C. However, if there are no problems with the dynamic range or sensitivity, the first light-receiving window 22A may be smaller than the second light-receiving window 22B, as shown in Figures 10D to 10F. Furthermore, if the second light-receiving window 22B is larger than the first light-receiving window 22A, it becomes easier for the second light-receiving window 22B to receive reflected light when the focusing spot is greatly distorted and moves away from the first light-receiving window 22A.

[0066] Figures 11A to 11D are explanatory diagrams of another example of the first light-receiving window 22A and the second light-receiving window 22B. In the light-receiving element 20 shown in Figures 11A to 11D, the two second light-receiving windows 22B are arranged so as to sandwich the first light-receiving window 22A, making it easier to detect reflected light by the second light-receiving windows 22B. It is desirable that the four second light-receiving windows 22B be evenly arranged around the first light-receiving window 22A, as shown in Figures 11A to 11D. Also, as shown in Figures 11B and 11D, arranging the first light-receiving window 22A and the two second light-receiving windows 22B on the diagonals of the rectangular light-receiving surface makes it easier to arrange the first light-receiving window 22A and the two light-receiving windows in the narrow space of the light-receiving surface (as a result, it is also possible to miniaturize the chip of the light-receiving element 20). Furthermore, in order to widen the dynamic range of the first light-receiving unit 21A and increase the sensitivity of the second light-receiving unit 21B, it is desirable to make the first light-receiving window 22A larger than the second light-receiving window 22B, as shown in Figures 11A and 11B. However, if there are no problems with the dynamic range or sensitivity, the first light-receiving window 22A may be smaller than the second light-receiving window 22B, as shown in Figures 11C and 11D. Note that the number of second light-receiving windows 22B is not limited to 2 or 4, but may be any other number.

[0067] Figure 12 is an explanatory diagram of an example of a photodetector array. As already explained, the measuring device 1 has multiple light-receiving elements 20 arranged in a two-dimensional array in the X and Y directions. When arranging multiple light-receiving elements 20 with respect to the light-receiving optical system 32 (dotted line in the figure), it is necessary to offset the light-receiving elements 20 with respect to the optical axis of the light-receiving optical system 32 (center of the dotted circle). As a result, the position of one light-receiving element 20 (first light-receiving element) with respect to the optical axis is different from the position of another light-receiving element 20 (second light-receiving element) with respect to the optical axis. The distortion of the focused spot differs depending on the position of the light-receiving elements 20 with respect to the light-receiving optical system 32, so the focused spot incident on each of the multiple light-receiving elements 20 arranged in a two-dimensional array will have a different shape.

[0068] Therefore, as shown in the figure, in this embodiment, the orientation of the first light-receiving window 22A and the second light-receiving window 22B of each light-receiving element 20 is made different depending on the distortion of the light-collecting spot. As a result, in this embodiment, in one light-receiving element 20 (first light-receiving element), the orientation of the first light-receiving window 22A and the second light-receiving window 22B is, for example, in the X direction, while in another light-receiving element 20 (second light-receiving element), the orientation of the first light-receiving window 22A and the second light-receiving window 22B is in the Y direction (or in a direction intersecting the X and Y directions). According to this embodiment, the second light-receiving unit 21B can more easily detect reflected light.

[0069] Furthermore, the orientation of the first light-receiving window 22A and the second light-receiving window 22B of all light-receiving elements 20 in the light-receiving element array may be the same. Also, not all light-receiving elements in the light-receiving element array are light-receiving elements having the first light-receiving window 22A and the second light-receiving window 22B of this embodiment; some of the light-receiving elements may be the light-receiving elements shown in Figure 4A.

[0070] As described above, the light-receiving element 20 of this embodiment includes a first light-receiving unit 21A that detects light irradiated onto the first light-receiving window 22A, and a second light-receiving unit 21B that detects light irradiated onto the second light-receiving window 22B, with the second light-receiving window 22B being provided around the first light-receiving window 22A (see Figure 6A). As a result, even if a part of the light-gathering spot is outside the first light-receiving window 22A, the reflected light can be detected by the second light-receiving unit 21B when the light-gathering spot is irradiated onto the second light-receiving window 22B (see Figure 6B).

[0071] Furthermore, in this embodiment, it is desirable that the second light-receiving unit 21B has higher sensitivity than the first light-receiving unit 21A. This makes it easier for the second light-receiving unit 21B to detect reflected light.

[0072] Furthermore, in this embodiment, it is desirable that the first light-receiving window 22A is larger than the second light-receiving window 22B. This makes it possible to achieve both a wider dynamic range for the first light-receiving unit 21A and a higher sensitivity for the second light-receiving unit 21B.

[0073] Furthermore, in this embodiment, it is desirable that multiple second light-receiving windows 22B are provided around the first light-receiving window 22A (see Figures 10 and 11). This makes it easier to detect reflected light with the second light-receiving windows 22B. However, it is also acceptable to have only one second light-receiving window 22B.

[0074] Furthermore, in this embodiment, it is desirable that the multiple second light-receiving windows 22B are arranged so as to sandwich the first light-receiving window 22A. This makes it easier to detect reflected light by the second light-receiving windows 22B. However, it is not necessary for the two second light-receiving windows 22B to be arranged so as to sandwich the first light-receiving window 22A.

[0075] Furthermore, in this embodiment, the first light-receiving window 22A and a plurality of second light-receiving windows 22B are arranged on the diagonals of the rectangular light-receiving surface (see Figures 10 and 11). This makes it easier to arrange the first light-receiving window 22A and the two second light-receiving windows 22B in the limited space of the light-receiving surface.

[0076] Furthermore, it is desirable that the light-receiving element 20 in this embodiment has a signal line 25 that outputs a current which is the sum of the current of the first light-receiving unit 21A and the current of the second light-receiving unit 21B (see Figure 9). This reduces the number of signal lines that output signals from the light-receiving element 20.

[0077] As described above, the measuring device 1 of this embodiment includes a light-emitting element 10 that irradiates light onto the object 90, an optical system 30, and a light-receiving element 20 that receives reflected light from the object 90. The light-receiving element 20 used in the measuring device 1 includes a first light-receiving unit 21A that detects light irradiated onto the first light-receiving window 22A, and a second light-receiving unit 21B that detects light irradiated onto the second light-receiving window 22B, with the second light-receiving window 22B being provided around the first light-receiving window 22A (see Figure 6A). As a result, even if a part of the focused spot is outside the first light-receiving window 22A, the reflected light can be detected by the second light-receiving unit 21B when the focused spot is irradiated onto the second light-receiving window 22B (see Figure 6B).

[0078] Furthermore, in this embodiment, the measuring device 1 is equipped with multiple light-receiving elements, and it is desirable that the position of one light-receiving element (first light-receiving element) with respect to the optical axis of the light-receiving optical system 32 is different from the position of another second light-receiving element (second light-receiving element) with respect to the optical axis of the light-receiving optical system 32, and that the direction in which the first light-receiving window 22A and the second light-receiving window 22B of one light-receiving element (first light-receiving element) are aligned is different from the direction in which the first light-receiving window 22A and the second light-receiving window 22B of another light-receiving element (second light-receiving element) are aligned. This makes it easier for each second light-receiving unit 21B to detect reflected light.

[0079] Although 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. Furthermore, the above embodiments are described in detail to explain the configuration in an easy-to-understand manner and are not necessarily limited to those having all the configurations described. In addition, some of the configurations of the above embodiments can be added to, deleted from, or replaced with other configurations. [Explanation of Symbols]

[0080] 1 measuring device, 3 housing, 5 mounting board, 6. Emitting side curved section, 7. Receiving side curved section, 8 substrate frame, 10 light-emitting element, 20 light-receiving element, 21 Light receiving section, 21A 1st light receiving section, 21B 2nd light receiving section, 22 Light receiving window, 22A First light receiving window, 22B Second light receiving window, 23 electrodes, 24 electrodes, 25 signal lines, 30 Optical system, 31 Light projection optical system, 32 Optical system for light reception, 33 Optical frame, 40 Controller, 41 Arithmetic unit, 42 Memory device, 50 Light detection device, 51 Conversion unit, 51A First conversion unit, 51B Second conversion unit, 52 Analog-to-digital conversion circuit, 53 Voltage summing section, 90 Object

Claims

1. Multiple light-emitting elements are arranged in the X and Y directions and emit light in the Z direction, An optical system having an optical axis along the Z direction, Multiple photodetectors are arranged in the X and Y directions, conjugate to a specific light-emitting element and the optical system, and receive reflected light. A controller that measures the coordinate in the Z direction by measuring the time from when the light-emitting element emits light until the light-receiving element receives the reflected light, Equipped with, The aforementioned light-receiving element is A first light receiving unit that outputs a first signal corresponding to the light irradiated onto the first light receiving window, A second light receiving unit that outputs a second signal corresponding to the light irradiated onto a second light receiving window provided around the first light receiving window, Equipped with, The controller measures the time based on the first signal from the first light receiving unit and the second signal from the second light receiving unit. The first light-receiving unit has a wider dynamic range than the second light-receiving unit. The second light-receiving unit has higher sensitivity than the first light-receiving unit. A measuring device characterized in that the first light-receiving window is larger than the second light-receiving window.

2. The measuring device according to Claim 1, The light-receiving element comprises a plurality of the second light-receiving units, A measuring device characterized in that a plurality of the second light-receiving windows are provided around the first light-receiving window.

3. The measuring device according to claim 2, A measuring device characterized in that a plurality of the second light-receiving windows are arranged so as to sandwich the first light-receiving window.

4. A measuring device according to claim 2 or 3, A measuring device characterized in that the first light-receiving window and a plurality of the second light-receiving windows are arranged on the diagonals of a rectangular light-receiving surface.

5. A measuring device according to any one of claims 1 to 4, A measuring device characterized by having a signal line that outputs a current obtained by adding the current of the second light-receiving unit to the current of the first light-receiving unit.

6. A measuring device according to claim 1, It comprises a plurality of light-receiving elements, including a first light-receiving element and a second light-receiving element. The position of the first light-receiving element with respect to the optical axis of the optical system is different from the position of the second light-receiving element with respect to the optical axis. A measuring device characterized in that the direction in which the first light-receiving window and the second light-receiving window of the first light-receiving element are aligned is different from the direction in which the first light-receiving window and the second light-receiving window of the second light-receiving element are aligned.

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