Light-receiving element and measuring device

Abstract

To provide a high-quality light reception device.SOLUTION: A light reception device is provided, comprising a modification unit configured to reflect twice light irradiated from a light-emitting element and reflected from an object to output the light from an exit surface, and a photosensitive element having a detection surface for detecting the light exiting from the modification unit.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a distance measurement system such as LiDAR is mounted on a vehicle, it is necessary to arrange a light emitting element, a light receiving element, an optical system, etc. that make up the distance measurement system in a narrow space. In order to arrange them in a narrow space, it is necessary to miniaturize the optical system by making the lens diameter small or shortening the overall length of the lens unit. However, when the optical system is miniaturized, the optical performance is sacrificed. Therefore, there is a risk of deterioration in the quality of the device, such as a decrease in the detection accuracy of an object.

[0005] In view of the above points, an object of the present invention is to provide a high-quality light receiving device.

Means for Solving the Problems

[0006] To achieve the above object, in one aspect of the present invention, there is provided a light receiving device including: a changing unit that reflects twice the light irradiated from a light emitting element and reflected by an object, and emits the light from an emission surface; and a light receiving element having a light detection surface that detects the light emitted from the changing unit.

[0007] In addition, the problems disclosed in the present application and the solutions thereto will be clarified by the section of the mode for carrying out the invention and the drawings.

Effects of the Invention

[0008] According to the present invention, a high-quality light receiving device is provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

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 a laser beam (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 receiver 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 receiver 20, an optical system 30, and a controller 40. Further, the measuring device 1 includes a mounting substrate 5 having a plurality of light emitting elements 10 and a plurality of light receivers 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) and emits a laser beam. 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 a laser beam 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 thereto.

[0015] The light receiver 20 is a block that converts an optical signal into an electrical signal while changing the direction of the optical signal from the light receiving optical system 32. Details of the light receiver 20 will be described later, but it includes a PD chip (Photodiode). The light receiver 20 is surface-mounted on the mounting substrate 5. Note that the mounting method of the light receiver 20 is not limited thereto. The mounting substrate 5 and the light receiver 20 are an example of the light receiving device in the present invention.

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

[0017] The light projection 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 disposed within the focal plane of the light projection optical system 31. The light projection 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 projection optical system 31. The light emitting element 10 irradiates the object 90 with light via the light projection optical system 31. The light projection optical system 31 is respectively constituted by a lens group composed of a plurality of lenses (for example, 5 to 7 lenses) (in FIG. 1, the lens group of the light projection optical system 31 is simply shown).

[0018] The light receiving optical system 32 is an optical system for causing the light receiver 20 to receive the reflected light from the object 90. The light receiver 20 is disposed within the focal plane of the light receiving optical system 32. The light receiving optical system 32 condenses the reflected light of the object 90 onto a predetermined light receiver 20. The light receiver 20 receives the reflected light from the object 90 via the light receiving optical system 32. Similarly to the light projection optical system 31, the light receiving optical system 32 is respectively constituted by a lens group composed of a plurality of lenses (for example, 5 to 7 lenses) (in FIG. 1, the lens group of the light receiving optical system 32 is simply shown).

[0019] The light projection optical system 31 and the light receiving optical system 32 are integrally configured, and their relative positional relationship is fixed. Specifically, the light projection lens barrel constituting the light projection optical system 31 and the light receiving lens barrel constituting the light receiving optical system 32 are fixed to a common optical frame 33.

[0020] The controller 40 is a control unit that controls the measurement device 1. The controller 40 controls the emission of laser light from the light emitting element 10. Also, based on the output signal of the light receiver 20, the controller 40 calculates the distance to the object 90. Specifically, the controller 40 measures the distance to the object 90 by measuring the time from when the pulsed laser light is projected from the light emitting element 10 until the light receiver 20 receives the reflected light. That is, the controller 40 measures the distance to the object 90 (measures the Z coordinate of the surface of the object 90) by controlling the light emitting element 10 and the light receiver 20 using the TOF (Time of flight) method. Also, by utilizing the fact that the laser light is irradiated in a predetermined direction and the reflected light in the predetermined direction is received, the controller 40 can measure the X, Y, and Z coordinates of the surface of the object 90 by measuring the Z coordinate of the surface of the object 90 while scanning in the XY direction.

[0021] The controller 40 includes an arithmetic unit 41 and a storage device 42. The arithmetic unit 41 is an arithmetic processing device such as a CPU or a GPU, for example. The storage device 42 is composed of a main storage device and an auxiliary storage device, and is a device that stores programs and data. When the arithmetic unit 41 executes 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 light receiver 20. Also, based on the output signal of the light receiver 20, the arithmetic unit 41 calculates the X, Y, and Z coordinates of the surface of the object 90. 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 a large number of points on the surface of the object 90 becomes data indicating a three-dimensional image (point cloud) of the surface of the object 90. The arithmetic unit 41 may analyze the object 90 based on the three-dimensional image stored in the storage device 42 by executing the program stored in the storage device 42 by the arithmetic unit 41.

[0022] The mounting substrate 5 is a substrate on which a plurality of light-emitting elements 10 and a plurality of light receivers 20 are mounted. A certain light receiver 20 is associated with a specific light-emitting element 10, and the detection position of a certain light receiver 20 is conjugate with the light-emitting position of the specific light-emitting element 10. In the present embodiment, there are a plurality of pairs of the light-emitting element 10 and the light receiver 20, and the surface of the object 90 can be measured in a plurality of channels. Note that the light-emitting element 10 emits laser light parallel to the substrate surface of the mounting substrate 5, and the light receiver 20 receives light (reflected light) incident from a direction substantially parallel to the substrate surface of the mounting substrate 5.

[0023] As shown in FIG. 1, the mounting substrate 5 has five light-emitting elements 10 and five light receivers 20. However, the number of the light-emitting elements 10 and the light receivers 20 is not limited to this. A plurality of light-emitting elements 10 are arranged at different positions in the X direction on the mounting substrate 5. Also, a plurality of light receivers 20 are arranged at different positions in the X direction on the mounting substrate 5.

[0024] As shown in FIG. 1, the mounting substrate 5 is provided with a light-emitting-side curved portion 6 and a light-receiving-side curved portion 7.

[0025] The light-emitting-side curved portion 6 is a portion having an arcuate edge. The light-emitting-side curved portion 6 is a portion for arranging a plurality of light-emitting elements 10 along the image surface curvature of the light-projecting optical system 31. A plurality of light-emitting elements 10 are arranged along the arcuate edge of the light-emitting-side curved portion 6. Thereby, each light-emitting element 10 is arranged at an appropriate position and angle with respect to the light-projecting optical system 31, and the influence of the image surface curvature of the light-projecting optical system 31 can be reduced.

[0026] The light-receiving-side curved portion 7 is a portion having an arcuate edge, and is provided at a position different from that of the light-emitting-side curved portion 6 in the X direction. The light-receiving-side curved portion 7 is a portion for arranging a plurality of light receivers 20 along the image surface curvature of the light-receiving optical system 32. A plurality of light receivers 20 are arranged along the arcuate edge of the light-receiving-side curved portion 7. Thereby, each light receiver 20 is arranged at an appropriate position and angle with respect to the light-receiving optical system 32, and the influence of the image surface curvature of the light-receiving optical system 32 can be reduced.

[0027] However, the light-emitting side bending portion 6 and the light-receiving side bending portion 7 may not be provided on the mounting substrate 5. In this case, a plurality of light-emitting elements 10 and a plurality of light receivers 20 are arranged along an edge perpendicular to the Z direction of the mounting substrate 5.

[0028] FIG. 2 is an explanatory view of the mounting substrate 5 as viewed from the X direction. Here, for the sake of explanation, the light-emitting side bending portion 6 and the light-receiving side bending portion 7 of the mounting substrate 5 are omitted, and it is assumed that the light-emitting elements 10 and the light receivers 20 are arranged along an edge parallel to the X direction of the mounting substrate 5. Here, for the sake of explanation, the inclination of the mounting substrate 5 is emphasized and shown in the figure.

[0029] As shown in FIG. 2, the measuring device 1 has a plurality of mounting substrates 5 (here, three mounting substrates 5). The plurality of mounting substrates 5 are arranged at different positions in the Y direction. As shown in FIG. 1, a plurality (here, five) of light-emitting elements 10 and a plurality of light receivers 20 are arranged at different positions in the X direction on each mounting substrate 5. Therefore, a light-emitting element array in which a plurality (here, 15) of light-emitting elements 10 are arranged in the X direction and the Y direction is configured, and a light-receiving element array in which a plurality of light receivers 20 are arranged in the X direction and the Y direction is configured. Here, the surface of the object 90 is measured with 5×3, 15 channels (5 channels in the X direction and 3 channels in the Y direction).

[0030] The plurality of mounting substrates 5 are arranged at different angles with respect to the Z direction. Specifically, as shown in FIG. 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 mounting substrate 5 faces the light-projecting optical system 31 and the incident surface 27A (described later) of the light receiver 20 of each mounting substrate 5 faces the light-receiving optical system 32. Thereby, since the light-emitting element 10 and the light receiver 20 are arranged at appropriate positions and angles with respect to the optical system 30, the influence of the field curvature of the optical system 30 can be reduced. The light-emitting elements 10 of each mounting substrate 5 are arranged to emit laser light parallel to the substrate surface of the mounting substrate 5. Further, the light receivers 20 of each mounting substrate 5 are arranged to receive light (reflected light) incident from a direction substantially parallel to the substrate surface of the mounting substrate 5. Since a plurality (here, five) of light-emitting elements 10 and a plurality (here, five) of light receivers 20 are mounted on the same substrate, and since the light-projecting 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), the respective light-emitting elements 10 and light receivers 20 can be maintained in a conjugate positional relationship with respect to the optical system 30. If the light-emitting-side curved portion 6 and the light-receiving-side curved portion 7 are provided on the mounting substrate 5 as in the present embodiment, even if the mounting substrate 5 is tilted, it is easy to arrange a plurality of light-emitting elements along the field curvature of the light-projecting optical system 31, and it is also easy to arrange a plurality of light receivers 20 along the field curvature of the light-receiving optical system 32.

[0031] In addition, a plurality of mounting substrates 5 may be arranged in parallel in the Z direction and may be arranged parallel to each other. However, if the mounting substrates 5 are arranged parallel to each other, it is necessary to vary the positions and angles of the light-emitting elements 10 and the light receivers 20 with respect to the mounting substrate 5 so that the light-emitting elements 10 and the light receivers 20 are in appropriate positions and angles with respect to the optical system 30 for each mounting substrate 5. In contrast, in the present embodiment, in order to vary the inclination of the mounting substrate 5, in any of the mounting substrates 5, the light-emitting element 10 can be configured to emit laser light parallel to the mounting substrate 5, and the light receiver 20 can be configured to receive light (reflected light) incident from a direction substantially parallel to the mounting substrate 5. Therefore, in the present embodiment, the plurality of light-emitting elements 10 and the plurality of light receivers 20 can be arranged at different positions in the X and Y directions in a simple configuration at appropriate positions and angles with respect to the optical system 30.

[0032] A plurality (here, three) of mounting substrates 5 are integrally fixed, and their relative positions are fixed. Specifically, the plurality of mounting substrates 5 are fixed to a common substrate frame 8. However, if the relative positions of the plurality of light-emitting elements 10 and the plurality of light receivers 20 can be fixed, the relative positions of the plurality of light-emitting elements 10 and the plurality of light receivers 20 may be fixed by other methods. Further, the measuring device 1 may not include a plurality of mounting substrates 5.

[0033] The driving device 45 (see FIG. 1) is a device that relatively moves the optical system 30 and the mounting substrate 5 (the light-emitting element 10 and the light receiver 20) in the XY direction. By relatively moving the optical system 30 and the mounting substrate 5 in the XY direction by the driving device 45, the relative position of the light-emitting element 10 with respect to the optical system 30 is changed, and the angle at which the laser light is irradiated is changed, whereby the laser light can be scanned.

[0034] The drive device 45 is configured to move 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 the optical system 30 and the mounting substrate 5). The drive device 45 may move the optical system 30 in the XY directions with respect to the mounting substrate 5, or may move the optical system 30 in the XY directions with respect to the mounting substrate 5, or may 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 the present embodiment, at least one of the optical frame 33 and the substrate frame 8 is supported by the housing 3 at predetermined resonance frequencies in the X direction and the Y direction respectively, and the drive device 45 vibrates at least one of the optical system 30 and the mounting substrate 5 at their respective resonance frequencies in the X direction and the Y direction. The drive device 45 is constituted by, for example, a voice coil motor, but is not limited thereto (it may be constituted by a piezoelectric element, for example).

[0035] FIG. 3A is an explanatory diagram of two-dimensional scanning. In the present embodiment, at least one of the optical system 30 and the mounting substrate 5 is vibrated at its respective resonance frequency in the X direction and the Y direction, so that the optical system 30 and the mounting substrate 5 (the light-emitting element 10 or the light receiver 20) are relatively displaced in the XY direction along the Lissajous curve as shown in FIG. 3A. The Lissajous curve is a graph of X = A sin(at + δ), Y = B sin(bt). Here, a and b are the frequencies in the X direction and the Y direction, respectively, t is time, and δ is the phase difference. As already described, since at least one of the optical frame 33 and the substrate frame 8 is supported at a predetermined resonance frequency in the X direction and the Y direction, a and b are known values. Also, by resonating the optical frame 33 or the substrate frame 8 with a predetermined amplitude by the driving device 45, A and B become known values, and δ becomes a known value based on the driving timings in the X direction and the Y direction by the driving device 45. Therefore, the controller 40 can calculate the XY-direction position of the light-emitting element 10 (or the light receiver 20) with respect to the optical system 30 based on the time t. That is, the controller 40 can calculate the direction in which the laser light is irradiated based on the time t. Note that instead of calculating the direction in which the laser light is irradiated based on the time t, the controller 40 may detect the relative position in the XY direction between the optical frame 33 and the substrate frame 8 by a position detector (not shown), and calculate the direction in which the laser light is irradiated based on this detection result.

[0036] Figure 3B is an explanatory diagram of two-dimensional scanning in a certain frame. The controller 40 acquires one frame (one three-dimensional image of the object 90) every predetermined time. 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 a plurality of points on the Lissajous curve. Thereby, it is possible to measure the coordinates with higher resolution. Note that the same Lissajous curve may be repeated for each frame. In this case, in each frame, the surface of the object 90 can be measured at the same position. On the other hand, the Lissajous curve may shift for each frame. In this case, in the next frame, the surface of the object 90 can be measured so as to interpolate between the point groups measured in the previous frame.

[0037] Figure 3C is an explanatory diagram of two-dimensional scanning by a plurality of channels. As shown in the figure, in the present embodiment, two-dimensional scanning is performed in different ranges for each channel. Thereby, the surface of the object 90 can be measured in a wide range in the X direction and the Y direction, and a wide FOV (field of view) can be realized.

[0038] Note that the two-dimensional scanning does not have to be performed along the Lissajous curve. For example, two-dimensional scanning may be performed by shifting a line scan in the X direction (or Y direction) in the Y direction (or X direction) a plurality of times. Also, instead of two-dimensional scanning, only one-dimensional scanning may be performed. Also, scanning does not have to be performed. When scanning is not performed, the measuring device 1 does not have to include the driving device 45. However, when scanning is not performed, the resolution of the point group decreases compared to the present embodiment.

[0039] <Regarding the light receiver> The light receiver 20 according to the present embodiment will be described.

[0040] Figure 4A is a view of the light receiver 20 seen from above. The light receiver 20 has a light receiving element 21 and a prism 27. Figure 4B is a cross-sectional view taken along the line B-B of Figure 4A, and Figure 4C is an exploded perspective view of the light receiver 20. Also, Figure 4D is a cross-sectional view of the light receiving element 21.

[0041] The light-receiving element 21 is surface-mounted flat on the surface of the mounting substrate 5. Specifically, the light-receiving element 21 is fixed on the surface of the mounting substrate 5 such that the surface of the mounting substrate 5 and the surface for detecting light in the light-receiving element 21 (hereinafter referred to as the light-receiving surface 21A) are substantially parallel. The light-receiving element 21 has a light-receiving window 23 for receiving light on the light-receiving surface 21A. The light-receiving window 23 is a light-receiving region provided on the light-receiving surface 21A of the light-receiving element 21. For example, when the light-receiving element 21 is an avalanche photodiode (APD), the light-receiving portion 22 of the light-receiving element 21 has a buffer layer, a light absorption layer, an intermediate layer, a multiplication layer, and a window layer on the substrate, and further has a guard ring at the outer periphery of the light-receiving region and the light-receiving region, and has electrodes 24 and 25 on the front and back surfaces of the substrate, respectively. Also, a protective layer is formed on the light-receiving surface 21A of the light-receiving element 21. Here, the light-receiving window 23 corresponds to the region inside the annular electrode 24 (the electrode on the light-receiving surface 21A side; the electrode on the substrate surface side). The diameter of the light-receiving window 23 may be referred to as the light-receiving diameter. The size of the light-receiving element 21 is several millimeters square (for example, 5 mm square), while the light-receiving diameter is, for example, 500 μm. However, the sizes of the light-receiving element 21 and the light-receiving diameter are not limited to this.

[0042] In addition, in FIG. 4D, for the sake of convenience, the height from the back surface of the light-receiving element 21 to the surface of the light-receiving window 23 provided at the center of the light-receiving element 21 is drawn to be the highest, but actually, on the light-receiving surface 21A side, a planarization film, a protective film, etc. (not shown) are formed. For this reason, the height from the back surface of the light-receiving element 21 to the light-receiving surface 21A including the protective film, etc. is substantially equal in the light-receiving element 21.

[0043] The prism 27 is a pentaprism fixed to the light-receiving element 21 and has a function of reflecting the incident light twice and changing the optical axis direction by 90 degrees and then emitting it. Examples of the material of the prism 27 include optical glass, quartz, resin, etc., but an appropriate one is adopted according to the required optical performance, usage conditions, design conditions, etc.

[0044] As shown in FIGS. 4 to 6, the prism 27 has a pentagonal cross section, and has two rectangular surfaces (referred to as the incident surface 27A and the exit surface 27B) that are orthogonal to each other, and rectangular reflecting surfaces 27C and 27D that are respectively connected to the incident surface 27A and the exit surface 27B.

[0045] As shown in FIG. 4B, the angle formed by the rectangular reflecting surfaces 27C and 27D is 22.5 degrees. The cross-sectional dimensions of the prism 27 are as shown in FIG. 4B, and the ratio of the length d of the exit surface 27B in the normal direction of the incident surface 27A to the total length of the prism 27 in the same direction is 1:1.41.

[0046] The incident surface 27A is a surface facing the light-receiving optical system 32, and the reflected light collected by the light-receiving optical system 32 is incident thereon. The exit surface 27B is fixed to the light-receiving element 21 and faces the light-receiving portion 22. The area of the exit surface 27B is larger than that of the light-receiving element 21.

[0047] The light incident on the incident surface 27A is reflected twice by the reflecting surfaces 27D and 27C, changing the direction of the optical axis by 90 degrees, and exits from the exit surface 27B so as to be orthogonal to the exit surface 27B (FIG. 4B).

[0048] An optical film can be attached or vapor-deposited on any of the incident surface 27A, the exit surface 27B, and the reflecting surfaces 27C and 27D. Examples of the optical film include an antireflection film, a filter that absorbs a specific wavelength, and a reflecting mirror. For example, by forming a reflecting mirror on either of the reflecting surfaces 27C and 27D, the reflectivity can be increased. Also, when an antireflection film is formed on any of the exit surface 27B and the reflecting surfaces 27C and 27D, the reflectivity and transmittance of light on these surfaces can be adjusted. Thus, by forming an optical film on any of the incident surface 27A, the exit surface 27B, and the reflecting surfaces 27C and 27D, the required optical performance can be obtained.

[0049] The method for fixing the light-receiving element 21 to the light-emitting surface 27B is appropriately selected according to the material of the prism 27, usage conditions, design conditions, etc. For example, methods of bonding using low-melting glass, polymers, or films, anodic bonding, or direct bonding can be cited as examples of bonding methods.

[0050] The light-emitting surface 27B may be fixed to the light-receiving element 21 via a resin film. In the examples shown in FIGS. 5A and 5B, a resin film 29 is sandwiched between the light-emitting surface 27B and the light-receiving element 21, and the light-emitting surface 27B and the light-receiving element 21 are fixed via the resin film 29. The resin film 29 can be, for example, an optical film. In this case, by passing the light emitted from the light-emitting surface 27B through the resin film 29, it is possible to suppress refraction and reflection of unnecessary light, or to absorb a specific wavelength and adjust the transmittance, etc., to obtain the required optical performance.

[0051] A gap may be provided between the light-emitting surface 27B and the light-receiving element 21. In the examples shown in FIGS. 6A and 6B, the light-emitting surface 27B is fixed to the light-receiving element 21 via a mounting member 28. The mounting member 28 is provided along the peripheral edge of the light-receiving element 21, and a gap is formed between the light-emitting surface 27B and the light-receiving element 21 by the thickness of the mounting member 28. The gap between the light-emitting surface 27B and the light-receiving element 21 is used to obtain required optical performance such as position adjustment between the focus of the light condensed by the light-receiving optical system 32 and the light-receiving portion 22. Also, by adjusting the thickness of the mounting member 28, it is possible to adjust the mounting angle or mounting position of the prism 27 with respect to the light-receiving element 21.

[0052] FIG. 7A is an explanatory diagram of the state of light condensation by the light-receiving optical system 32. FIG. 7B is an explanatory diagram of the light-receiving window 23 and the condensing spot on the light-receiving element 21 on the optical axis of the light-receiving optical system 32.

[0053] Since a plurality of light receivers 20 are arranged for one light-receiving optical system 32, as shown in FIG. 7A, in addition to the light receiver 20 arranged on the optical axis with respect to the light-receiving optical system 32, there is a light receiver 20 arranged at a position deviated from the optical axis. In FIG. 7A, only one light receiver 20 deviated from the optical axis of the light-receiving optical system 32 is drawn, but there are a plurality of light receivers 20 deviated from the optical axis of the light-receiving optical system 32, and furthermore, the ways of deviation from the optical axis of the light-receiving optical system 32 are also different from each other. The reflected light emitted from the light-receiving optical system 32 is condensed onto the light-receiving surface 21A of the light-receiving element 21 via the prism 27 to form a condensed spot (FIG. 7B).

[0054] FIG. 8 is an explanatory diagram of the output signal of the light-receiving element 21. The upper graph in each figure shows the current output from the light-receiving unit 22. As already described, in the present embodiment, since the light-emitting element 10 emits pulsed light (Tx in FIG. 1), the condensed spot of the pulsed reflected light (Rx in FIG. 1) is irradiated onto the light-receiving element 21. Since the reflected light is irradiated onto the light-receiving window 23, the light-receiving unit 22 outputs a pulsed current (output signal) as shown in the graph of FIG. 8.

[0055] Note that the current output from the light-receiving element 21 may be a positive-side current or a negative-side current. The light-receiving unit 22 outputs a current (output signal) corresponding to the light irradiated onto the light-receiving window 23.

[0056] The controller 40 can obtain the time t when the pulsed reflected light is received based on the output signal. That is, the controller 40 can measure the time from when the pulsed laser light is projected from the light-emitting element 10 until the light-receiving element 21 receives the reflected light, and can measure the distance to the object 90.

[0057] FIG. 9 is an explanatory diagram of an example of a light detection device using the light-receiving device of the present embodiment. For example, on the aforementioned mounting substrate 5, a circuit for configuring the light detection device 50 shown in FIG. 9 is provided.

[0058] The light detection device 50 includes the above-described light receiver 20 and a conversion unit 51. The conversion unit 51 is a circuit that converts the signal output from the light receiver 20 from current to voltage. The light detection device 50, that is, has a conversion unit 51 for each light receiving element 21. The conversion unit 51 shown in FIG. 9 is a circuit that converts the output signal output from the light receiving unit 22 from current to voltage. The conversion unit 51 is composed of a transimpedance amplifier (TIA).

[0059] The light detection device 50 has an analog-to-digital conversion circuit 52 (ADC). The analog-to-digital conversion circuit 52 (ADC) is provided for each conversion unit 51. Each analog-to-digital conversion circuit 52 converts the voltage (analog signal) output from the conversion unit 51 into a digital signal and outputs the signal to the controller 40 (arithmetic unit 41). The controller 40 (arithmetic unit 41) obtains the time t when pulsed reflected light is received by comparing the voltage value of the output signal with a threshold value, calculates the time from when the pulsed laser light is projected from the light emitting element 10 until the light receiving element 21 receives the reflected light, and calculates the distance to the object 90.

[0060] <Effect> In the above embodiment, a prism 27 (corresponding to the modification part in the present invention) that reflects the optical axis direction of the light irradiated from the light emitting element 10 and reflected by the object twice and emits it from the emission surface 27B, and a light receiving element 21 having a light receiving surface 21A (corresponding to the detection surface) that detects the light emitted from the prism 27 are disclosed.

[0061] With the above configuration, the distance until the reflected light reaches the light receiving element 21 can be extended. That is, the back focus distance of the light receiving optical system 32 is extended, and the numerical aperture (NA value) of the light receiving optical system 32 can be reduced.

[0062] A specific example is shown in FIG. 10. When the light-receiving optical system 32 has a short back focus and a large NA value (FIG. 10A), the deviation of the angle of the reflected light with respect to the optical axis of the light-receiving optical system 32 greatly shifts the position of the condensing spot, which may affect the detection performance of the light-receiving element 21. On the other hand, if the optical system has a long back focus and a small NA value (FIG. 10B), the influence of the deviation of the angle of the reflected light on the position of the condensing spot can be reduced.

[0063] In this embodiment, since the optical system can have a long back focus and allow a low NA value in this way, even if the total length of the combined lenses of the light-receiving optical system 32 is shortened or the lenses are made smaller in diameter, the detection performance of the reflected light by the light-receiving element 21 is maintained. In addition, since the optical path distance is extended by using the prism 27, the design length from the light-receiving optical system 32 to the light-receiving element 21 can be shortened (FIG. 10C). Therefore, the light-receiving optical system 32 and the measuring device 1 can be miniaturized.

[0064] In addition, with the above configuration, the light receiver 20 can be mounted on the mounting substrate 5 in a planar manner. Therefore, there is no risk of losing the fixation between the light-receiving element 21 and the mounting substrate 5, and a high-quality light-receiving device can be obtained.

[0065] In the light receiver 20, the light-receiving element 21 is mounted on the surface of the mounting substrate 5 and electrically connected. Therefore, there is no risk of losing the fixation between the light-receiving element 21 and the mounting substrate 5, and a high-quality light-receiving device can be obtained.

[0066] The prism 27 is a pentaprism. The light receiver 20 can change the optical axis direction of the reflected light with a simple configuration using the pentaprism.

[0067] The area of the exit surface 27B is larger than the area of the light-receiving surface 21A of the light-receiving element 21. By making the prism 27 larger, the light-receiving beam or the amount of received light of the reflected light can be increased. The amount of light incident on the light-receiving unit 22 increases, and the detection accuracy of the light-receiving element 21 is improved.

[0068] The prism 27 can include at least one of an antireflection film and a vapor deposition film mirror. Further, the prism 27 and the light receiving surface 21A of the light receiving element 21 may face each other with a resin film interposed therebetween. By providing such an optical film in the light receiver 20, desired optical performance can be obtained, such as suppression of unnecessary light refraction or reflection, or absorption of a specific wavelength and adjustment of transmittance.

[0069] The light receiver 20 may include a mounting member 28 that mounts the prism 27 to the light receiving element 21 while forming a gap between the emission surface 27B and the light receiving surface 21A. By forming the gap, it becomes possible to adjust the distance from the light receiving optical system 32 to the light receiving portion 22 or to obtain desired optical performance.

[0070] On the mounting substrate 5, both the light emitting element 10 and the light receiving element 21 are surface-mounted and electrically connected. Therefore, there is no risk of losing the fixing between the light receiving element 21 and the mounting substrate 5 or the fixing between the light emitting element 10 and the mounting substrate 5, and a high-quality light detection device 50 can be obtained.

[0071] <Modification Example> In the above embodiment, the prism 27 is used as the modified part. The present invention is not limited to such a configuration. As an example, as shown in the modification example of FIG. 11, when using a penta mirror instead of the prism 27, the optical axis direction of the reflected light may be changed using two or more mirrors 60. Further, the conversion angle of the optical axis direction between the incident light and the emitted light is not limited to 90 degrees. For example, the prism 27 may be a prism of a type different from the penta prism, or the optical axis change angle may be set to an angle other than 90 degrees using the mirror 60.

Description of Reference Numerals

[0072] 1 Measuring device, 3 Housing, 5 Mounting substrate, 6 Light emitting side curved portion, 7 Light receiving side curved portion, 8 Frame for substrate, 10 Light emitting element, 20 Light receiver 21 Light receiving element, 22 Light receiving portion, 23 Light receiving window, 24 Electrode, 25 Electrode 27 Prism 29 Resin film 30 Optical system, 31 Light projection optical system 32 Light reception optical system, 33 Optical frame 40 Controller, 41 Arithmetic unit, 42 Storage device 50 Light detection device, 51 Conversion unit 52 Analog-digital conversion circuit 90 Object

Claims

1. a modifying portion that is irradiated with light from a light-emitting element, reflects the light reflected by an object twice, and emits the light from an emission surface; a light-receiving element having a light-receiving surface that detects the light emitted from the modifying portion; and a mounting member that mounts the modifying portion to the light-receiving element while forming only an air gap between the emission surface and the light-receiving surface, wherein the mounting member is a light-receiving device provided along a peripheral edge portion of the light-receiving element.

2. The light-receiving device according to claim 1, wherein the modifying portion is a pentaprism.

3. The light-receiving device according to claim 1 or 2, further comprising a substrate to which the light-receiving element is attached and is electrically connected.

4. The light-receiving device according to any one of claims 1 to 3, wherein an area of the emission surface is larger than an area of the light-receiving surface.

5. The light-receiving device according to any one of claims 1 to 4, wherein the modifying portion includes at least one of an antireflection film and a vapor deposition film mirror.

6. The light-receiving device according to any one of claims 1 to 5, wherein the emission surface and the light-receiving surface face each other with a resin film therebetween.

7. a light-emitting element that irradiates an object with light; a modifying portion that reflects the light reflected by the object twice and emits the light from an emission surface; a light-receiving element having a light-receiving surface that detects the light emitted from the modifying portion; and a mounting member that mounts the modifying portion to the light-receiving element while forming only an air gap between the emission surface and the light-receiving surface, wherein the mounting member is provided along a peripheral edge portion of the light-receiving element, a measuring device.

8. The measuring device according to claim 7, further comprising a substrate on which the light-emitting element and the light-receiving element are attached to the surface and the light-emitting element and the light-receiving element are electrically connected.

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