Control method for measuring device, measuring device, control program for measuring device, and computer-readable recording medium having computer program recorded thereon

Abstract

The present invention suppresses electric effects due to the reception of reflected light having a relatively high light intensity, while making it possible to measure the distance to a measurement target object separated by a prescribed distance. This control method for a measuring device is a control method for a measuring device provided with: a light projector that emits light; and a light receiver having a light receiving element that receives reflected light, which is the light that is emitted by the projector and reflected back from the measurement target object. In a first period between an emission timing of the light projector and a delayed timing later than the emission timing, the light-receiving sensitivity of the light receiving element is set to be lower than a reference sensitivity with which it is possible to detect the measurement target object separated by the prescribed distance from the measuring device, and in a second period, after the delayed timing, the light-receiving sensitivity is set to the reference sensitivity, and the distance to the measurement target object is measured on the basis of a light reception signal from the light receiving element in the second period.

Description

MEASURING DEVICE CONTROL METHOD, MEASURING DEVICE ... CONTROL PROGRAM, AND COMPUTER-READABLE RECORDING MEDIUM HAVING COMPUTER PROGRAM RECORDED THEREIN

[0001] The technology disclosed in this specification relates to a method for manufacturing a measuring device.

[0002] With the advancement of AD (Autonomous Driving) and ADAS (Advanced Driver-Assistance Systems), research and development of LiDAR (Light Detection and Ranging) is underway as one of the measurement devices used to grasp the surrounding environment and estimate the vehicle's position while the vehicle is traveling. LiDAR includes a projector that projects (irradiates) laser light onto a measurement target, and a photoreceiver that receives the reflected light that is returned from the measurement target after being reflected by the laser light. LiDAR outputs information about the measurement target by measuring the distance to the measurement target based on the time difference between the emission timing of the projector when the laser light is emitted and the reception timing of the reflected light by the photoreceiver.

[0003] The light receiver has a light receiving surface on which a plurality of photon counting type light receiving elements (SPAD: Single Photon Avalanche Diode) are arranged in an array (see, for example, Patent Document 1).

[0004] JP 2018-91760 A

[0005] Conventional measurement devices can be electrically affected by receiving reflected light with a relatively high optical intensity. For example, laser light emitted from a projector can be reflected not only by the measurement target but also by an object (hereinafter referred to as a "near-distance object") located closer to the measurement device than the measurement target and received by the receiver. Light reflected from a near-distance object exhibits a smaller optical intensity attenuation rate relative to the emitted laser light than light reflected from the measurement target. Therefore, the optical intensity of light reflected from a near-distance object is higher than that of light reflected from the measurement target. Meanwhile, in conventional measurement devices, the light-receiving element in the receiver always has a constant, fixed sensitivity. The fixed sensitivity is set based on detecting the measurement target with a predetermined accuracy, not a near-distance object. Therefore, when the light-receiving element receives high-intensity reflected light from a near-distance object, the light-receiving element outputs an excessively high level of light-receiving signal (e.g., current) according to the fixed sensitivity, resulting in electrical effects such as overcurrent failure. This issue is common to measurement devices equipped with light-receiving elements other than SPADs.

[0006] This specification discloses a technique that can solve at least one of the above-mentioned problems.

[0007] The technology disclosed in this specification can be realized, for example, in the following forms.

[0008] (1) A method for controlling a measurement device disclosed in this specification is a method for controlling a measurement device including a light projector that emits light and a light receiver having a light receiving element that receives light that is reflected back from a measurement object when the light projector emits light, the method comprising: during a first period between an emission timing of the light projector and a delay timing that is later than the emission timing, setting the light receiving sensitivity of the light receiving element to a value lower than a reference sensitivity that allows detection of a measurement object that is a specified distance away from the measurement device; during a second period after the delay timing, setting the light receiving sensitivity to the reference sensitivity; and measuring the distance to the measurement object based on a light receiving signal from the light receiving element during the second period.

[0009] In this control method, the light-receiving sensitivity of the light-receiving element is set lower than the reference sensitivity during a first period from the emission timing of the projector to the delay timing. Therefore, even if the light-receiving element receives reflected light with a relatively high light intensity during the first period, electrical effects associated with photoelectric conversion in the light-receiving element can be suppressed. Furthermore, in this control method, the light-receiving sensitivity is set to the reference sensitivity during a second period after the delay timing, making it possible to measure the distance to a measurement target that is a specified distance from the measurement device. In this way, this control method makes it possible to measure the distance to a measurement target that is a specified distance away while suppressing electrical effects caused by receiving reflected light with a relatively high light intensity.

[0010] (2) In the control method for the measurement device, the light receiving sensitivity may be set to a preliminary sensitivity that is greater than 0 and lower than the reference sensitivity during at least a third period of the first period that includes a period immediately before the delay timing. This control method can suppress overshoot of the light receiving signal from the light receiving element that accompanies a change in light receiving sensitivity, compared to a configuration in which the light receiving sensitivity is suddenly increased from 0 to the reference sensitivity at the delay timing, for example.

[0011] (3) In the control method for the measurement device, the light receiving sensitivity may be increased stepwise or continuously over time so as to approach the reference sensitivity over time during the third period. This control method can more effectively suppress overshoot of the light receiving signal from the light receiving element due to a change in the light receiving sensitivity.

[0012] (4) In the method for controlling the measurement device, the distance to the measurement object may be measured based on the light-receiving signal from the light-receiving element during the third period. According to this control method, the distance to the measurement object can be measured during the third period before the delay timing while suppressing electrical influences caused by receiving reflected light with high optical intensity.

[0013] (5) In the above-described method for controlling a measurement device, the light-receiving element may be a SPAD, and the voltage applied to the SPAD may be set to less than a breakdown voltage during the first period, and the voltage applied to the SPAD may be set to equal to or greater than the breakdown voltage during the second period. This configuration makes it possible to measure the distance to a measurement object that is a specified distance away using the SPAD, while suppressing electrical effects caused by receiving reflected light with a relatively high optical intensity.

[0014] The technology disclosed in this specification can be realized in various forms, such as a control method for a measuring device, a measuring device, a control program for a measuring device, and a computer-readable recording medium on which a computer program is recorded.

[0015] A block diagram showing the schematic configuration of the measurement device 10 according to the embodiment. A side cross-sectional view showing the internal configuration of the light receiver 30. A side cross-sectional view showing the internal configuration of the sensor package 70. A flowchart showing the contents of the measurement process. A timing chart showing the emission timing and delay timing. A side cross-sectional view showing the internal configuration of the sensor package 70a of the comparative example. A side cross-sectional view showing the internal configuration of the sensor package 70A of the modified example.

[0016] A. Embodiment: A-1. Configuration of Measuring Device 10: FIG. 1 is a block diagram showing a schematic configuration of the measuring device 10 according to this embodiment. As shown in FIG. 1, the measuring device 10 includes a projector 20 that irradiates a measurement target W with emitted light L1 (e.g., a light beam (laser light)), and a photoreceiver 30 that receives reflected light L2 (return light) that is generated when the emitted light L1 is reflected back from the measurement target W, and functions as a LiDAR. The measuring device 10 measures the difference between the timing at which the projector 20 emits the emitted light L1 and the timing at which the photoreceiver 30 receives the reflected light L2 (time of flight of the laser light, hereinafter referred to as "TOF" (Time of Flight)) to acquire information about the measurement target W.

[0017] The measuring device 10 is mounted on, for example, a vehicle (not shown) equipped with AD or ADAS. The measuring device 10 assists in detecting objects such as people and other vehicles while the vehicle is traveling, and provides various information to other devices and users that is useful for ensuring the safety of the driver of the vehicle and those around the vehicle, and for reducing damage to surrounding objects while the vehicle is being driven.

[0018] The light projector 20 includes a light source 22 , a light projecting optical system 24 , a light projecting control device 26 , and a current source 28 .

[0019] The light source 22 includes a light-emitting source having one or more light-emitting elements (not shown), or one or more light-emitting element arrays (e.g., light-emitting elements arranged linearly (one-dimensionally) or planarly (two-dimensionally)). The light-emitting element may be, for example, a laser diode, a surface-emitting laser light-emitting element (e.g., a VCSEL (Vertical Cavity Surface Emitting Laser), hereinafter referred to as a "surface-emitting element"), or a surface-emitting element array (e.g., a VCSEL array) in which a plurality of surface-emitting elements are arranged one-dimensionally or two-dimensionally on a substrate (e.g., a semiconductor substrate, a ceramic substrate, etc.).

[0020] The current source 28 supplies a current corresponding to a control signal input from the light projection control device 26 to the light emitting element that constitutes the light source 22. The current source 28 supplies, for example, a periodic square wave current to the light emitting element for turning on and off the current flowing through the light emitting element.

[0021] The light-projection control device 26 generates a control signal for the current source 28 and inputs it to the current source 28, thereby controlling the current (drive current) supplied to the light-emitting element from the current source 28. The light-projection control device 26 inputs a signal indicating the timing at which the light-emitting element emits light (the timing at which the light-emitting element emits light; hereinafter referred to as "emission timing") to the TOF measurement device 40. The light-projection control device 26 periodically controls the on / off of a current flowing through the light-emitting element, for example, to cause the light-emitting element to emit light periodically and repeatedly.

[0022] The light projection optical system 24 adjusts the light distribution of the output light L1 by, for example, applying an optical effect (such as refraction, scattering, or diffraction) to the light emitted by the light source 22. The light projection optical system 24 is configured using optical components such as various lenses, such as collimating lenses, and reflecting mirrors (mirrors).

[0023] The light receiver 30 includes a light receiving section 32 and a light receiving optical system 34 .

[0024] The light receiving optical system 34 collects reflected light L2, which is light L1 emitted from the projector 20 and reflected by the measurement target W or the like, onto the light receiving unit 32. The light receiving optical system 34 is configured using optical components such as various lenses, such as a collecting lens, various filters, such as a wavelength filter, and a reflecting mirror (mirror).

[0025] The light receiving unit 32 has a plurality of light receiving elements. The light receiving elements are, for example, photodiodes, APDs (Avalanche Photodiodes), SPADs (Single Photon Avalanche Diodes), balanced photodetectors, etc. The light receiving unit 32 performs photoelectric conversion on the reflected light L2 incident from the light receiving optical system 34 to generate a light receiving signal with a current level or voltage level corresponding to the intensity of the reflected light L2. The light receiving unit 32 inputs, to the TOF measurement device 40, a signal indicating the timing at which the light receiving elements constituting the light receiving unit 32 receive the reflected light L2 (hereinafter referred to as "light receiving timing"), and the light receiving signal generated by the light receiving elements.

[0026] The measurement apparatus 10 further includes a TOF measurement device 40, a control circuit 42, and a communication I / F (Inter face) 50. In this embodiment, the TOF measurement device 40 and the control circuit 42 are an example of a controller.

[0027] The TOF measurement device 40 calculates the TOF based on a signal indicating the emission timing input from the light-projection control device 26 and a signal indicating the light-reception timing input from the light-receiving unit 32. The TOF measurement device 40 has, for example, a time measurement IC (Integrated Circuit) equipped with a TDC (Time to Digital Converter) circuit. The TOF measurement device 40 inputs the calculated TOF and the light-receiving signal input from the light-receiving unit 32 to the control circuit 42.

[0028] The control circuit 42 has a processor (such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), DSP (Digital Signal Processor)). Based on the light receiving signal and TOF input from the TOF measurement device 40, the control circuit 42 generates information used for various measurements such as detection of the measurement object W and distance measurement. The information includes, for example, a histogram used in time-correlated single photon counting, distances to each point on the measurement target W, a point cloud (point cloud information), etc. The control circuit 42 also controls the light-projection control device 26 and the light-receiving unit 32. The control circuit 42 controls the light-projection control device 26 and the light-receiving unit 32, for example, to control the emission timing and light-receiving timing so as to speed up or optimize the processing for generating the histogram. The information generated by the control circuit 42 is provided (transmitted) via the communication I / F 50 to devices that use the information (hereinafter referred to as "various use devices 60").

[0029] The various utilization devices 60 perform, for example, the creation of an environmental map using a point cloud, and self-position estimation (SLAM (Simultaneous Localization and Mapping)) using a scan matching algorithm (NDT (Normal Distributions Transform), ICP (Iterative Closest Point), etc.).

[0030] A-2. Internal Configuration of the Optical Receiver 30: Fig. 2 is a side cross-sectional view showing the internal configuration of the optical receiver 30. As shown in Fig. 2, the optical receiver 30 includes an optical receiver housing 61 and a sensor package 70.

[0031] The receiver housing 61 has an internal storage space 64. Specifically, the receiver housing 61 has a substrate 62, a cylindrical body 63, and the light-receiving optical system 34. The substrate 62 is a rectangular plate-shaped member and is formed, for example, from resin. The cylindrical body 63 is disposed on the substrate 62. One end (lower side in FIG. 2 ) of the cylindrical body 63 is bonded to the substrate 62, and the opening on that side of the cylindrical body 63 is sealed by the substrate 62. The light-receiving optical system 34 is held in the opening on the other end (upper side in FIG. 2 ) of the cylindrical body 63. That is, the opening on the other end of the cylindrical body 63 is sealed by the light-receiving optical system 34. Note that the light-receiving optical system 34 is a compound lens including multiple lenses, but the shape of the light-receiving optical system 34 is simplified in FIG. 2 .

[0032] The space surrounded by the substrate 62, the cylindrical body 63, and the light-receiving optical system 34 is the accommodation space 64. The sensor package 70 is accommodated in the accommodation space 64 (closed space) of the receiver housing 61. The sensor package 70 is disposed on the substrate 62.

[0033] Fig. 3 is a side cross-sectional view showing the internal configuration of the sensor package 70. As shown in Fig. 3, the sensor package 70 includes a light receiving unit 32, a cavity 76, a lid 78, and a BPF 72 (band-pass filter).

[0034] The cavity 76 has a recess 75 formed in one surface (the upper surface in FIG. 3 ). The cavity 76 is made of, for example, resin. The lid 78 is a light-transmitting, flat-plate member made of, for example, glass or resin. The lid 78 is disposed so as to close the opening of the cavity 76. Specifically, the peripheral portion of the lower surface of the lid 78 and the periphery of the opening of the cavity 76 are bonded with a bonding material 74 (for example, an epoxy resin adhesive). The entire outer surface 79 of the lid 78 (the upper surface in FIG. 3 ) is preferably coated with an anti-reflection film (AR coating).

[0035] The light receiving unit 32 is housed in the recess 75. The light receiving unit 32 is disposed on the bottom surface of the recess 75. The light receiving unit 32 has a light receiving surface 32A. The light receiving surface 32A faces the lid 78.

[0036] The BPF 72 is housed in the recess 75 and is disposed between the light receiving surface 32A and the lid 78. A stepped surface 75A is formed on the inner peripheral surface that constitutes the recess 75. The peripheral portion of the lower surface of the BPF 72 is disposed on the stepped surface 75A, thereby fixing the BPF 72 to the cavity 76.

[0037] The BPF 72 has a dielectric multilayer film 71 and transmits light in a specific frequency band and does not transmit or attenuates light in other frequency bands. In this embodiment, the emitted light L1 emitted by the projector 20 is infrared light, and the dielectric multilayer film 71 has a function of transmitting only light in the infrared frequency band. Specifically, the BPF 72 is a generally flat member. The BPF 72 has the dielectric multilayer film 71 and a base material 73. The base material 73 is a flat, light-transmitting member made of, for example, glass or resin. The dielectric multilayer film 71 is coated on one surface of the base material 73. In FIG. 3 , the dielectric multilayer film 71 is formed on the surface facing the lid 78, but it may also be formed on the surface opposite the lid 78.

[0038] A-3. Measurement Process: Fig. 4 is a flowchart showing the contents of the measurement process, and Fig. 5 is a timing chart showing emission timing t1 and delay timing t2. The measurement process is a process in which the light receiving sensitivity of the light receiving element is set to the preliminary sensitivity during a first period ΔT1 (delay period) from emission timing t1 of the projector 20 to delay timing t2, and the light receiving sensitivity is set to the reference sensitivity during a second period ΔT2 after delay timing t2, and measurements are performed on the measurement target. The second period ΔT2 is the period from delay timing t2 to the next emission timing t1.

[0039] The light receiving sensitivity of the light receiving element is the amplification factor (amplification factor) of the amount of reflected light L2 received by the light receiving element (light receiving intensity). The reference sensitivity is the light receiving sensitivity capable of detecting an object located at a specified distance (e.g., 200 m) or more from the measurement device 10 (hereinafter referred to as a "long-distance object"). The preliminary sensitivity is the light receiving sensitivity lower than the reference sensitivity and capable of detecting an object located at a distance less than a specified distance (e.g., several tens of meters) from the measurement device 10 (hereinafter referred to as a "short-distance object"). The first period ΔT1 is shorter than the time from the emission timing t1 of the emitted light L1 to the reception timing of the light reflected by the long-distance object and received by the light receiving element. In other words, during the first period ΔT1, the reflected light L2 from the short-distance object may be received by the light receiving element, but the reflected light L2 from the long-distance object may not be received by the light receiving element. Conversely, during the second period ΔT2, the light receiving element does not receive the reflected light L2 from a short-distance object, but the light receiving element may receive the reflected light L2 from a long-distance object.

[0040] The control circuit 42 has a function of changing the light receiving sensitivity of the multiple light receiving elements arranged in the light receiving unit 32. For example, if the light receiving elements are amplification type light receiving elements (e.g., APDs, SPADs), the control circuit 42 has a function of changing the voltage applied to the light receiving elements. The control circuit 42 can change the light receiving sensitivity by changing the voltage applied to the light receiving elements.

[0041] When the control circuit 42 receives an instruction to start measurement from, for example, the utilization device 60, it executes the measurement process shown in FIG. 4 . The control circuit 42 determines whether emission timing t1 has arrived (S110). Note that emission timing t1 is a timing that is repeated at predetermined time intervals (= a first period ΔT1 + a second period ΔT2, described below) (see the L1 timing chart in FIG. 5 ). If the control circuit 42 determines that emission timing t1 has not arrived (NO in S110), it waits as is. However, if the control circuit 42 determines that emission timing t1 has arrived (YES in S110), it causes the light-emitting element disposed in the light source 22 of the projector 20 to emit emission light L1 (S120).

[0042] Furthermore, when the control circuit 42 determines that the emission timing t1 has arrived (S110: YES), it sets the light receiving sensitivity of the light receiving element to a preliminary sensitivity (S130). If the light receiving element is a SPAD, the preliminary sensitivity is the light receiving sensitivity of the SPAD (for example, up to 10 ３ ) (see the V timing chart in FIG. 5 ). In this embodiment, the standby voltage Va increases continuously over time during the first period ΔT1 so as to approach the breakdown voltage Vb. Note that the standby voltage Va may also increase stepwise over time during the first period ΔT1 so as to approach the breakdown voltage Vb. The first period ΔT1 is an example of a third period.

[0043] Next, the control circuit 42 determines whether the light receiving element has received the reflected light L2 (S140). If the control circuit 42 determines that the light receiving element has received the reflected light L2 (S140: YES, see timing t3 in the L2a timing chart in FIG. 5), it performs measurements related to a close-range object (object detection, distance measurement, etc.) based on the light receiving signal from the light receiving element (S150). Then, the process proceeds to S160.

[0044] At this time, the light intensity of the reflected light L2 from a close-distance object is attenuated less than that of the emitted light L1 compared to that of the reflected light L2 from a long-distance object. Therefore, the light intensity of the reflected light L2 from a close-distance object is higher than that of the reflected light L2 from a long-distance object. However, during the first period ΔT1, the light receiving sensitivity of the light receiving element is set to a preliminary sensitivity lower than the reference sensitivity. This makes it possible to suppress electrical effects caused by receiving the reflected light L2 from a close-distance object. In other words, because the voltage applied to the SPAD is set to less than the breakdown voltage Vb, the amplification of the reflected light L2 from the close-distance object is suppressed, thereby suppressing, for example, the generation of an overcurrent from the SPAD.

[0045] If the control circuit 42 determines that the light receiving element does not receive the reflected light L2 (S140: NO), the control circuit 42 proceeds to S160 without performing the measurement of the close-range object (S150).

[0046] In S160, the control circuit 42 determines whether the delay timing t2 has arrived. The delay timing t2 is the timing after the first period ΔT1 has elapsed since the emission timing t1 (see FIG. 5). If the control circuit 42 determines that the delay timing t2 has not arrived (S160: NO), the process returns to S140. That is, the control circuit 42 continues the process of determining whether or not the reflected light L2 has been received while maintaining the light receiving sensitivity at the preliminary sensitivity.

[0047] When the control circuit 42 determines that the delay timing t2 has arrived (S160: YES), it sets the light receiving sensitivity of the light receiving element to the reference sensitivity (S170). If the light receiving element is a SPAD, the reference sensitivity is the light receiving sensitivity of the SPAD when the voltage applied to the SPAD is set to a breakdown voltage Vb or higher (for example, 10 ６ ) (see the V timing chart of FIG. 5).

[0048] Next, the control circuit 42 determines whether the light receiving element has received the reflected light L2 (S180). If the control circuit 42 determines that the light receiving element has received the reflected light L2 (S180: YES, see timing t4 in the L2b timing chart in FIG. 5), it performs measurements (object detection, distance measurement, etc.) related to the long-distance object based on the light receiving signal from the light receiving element (S190). The process then proceeds to S200. At this time, the light intensity of the reflected light L2 from the long-distance object is lower than the light intensity of the reflected light L2 from the short-distance object. Therefore, even if the light receiving sensitivity of the light receiving element is set to a relatively high reference sensitivity, the electrical influence caused by receiving the reflected light L2 is suppressed.

[0049] If the control circuit 42 determines that the light receiving element does not receive the reflected light L2 (S190: NO), the control circuit 42 proceeds to S200 without performing measurement of the long-distance object (S190).

[0050] In S200, the control circuit 42 again determines whether emission timing t1 has arrived. If the control circuit 42 determines that emission timing t1 has not arrived (S200: NO), the process returns to S180. That is, the control circuit 42 continues the process of determining whether reflected light L2 has been received while maintaining the light-receiving sensitivity at the reference sensitivity. If the control circuit 42 determines that emission timing t1 has arrived (S200: YES), the process returns to S120. That is, the control circuit 42 sets the light-receiving sensitivity to the preliminary sensitivity, causes the projector 20 to emit emitted light L1 (S130), and executes the process of determining whether reflected light L2 has been received (S140).

[0051] A-4. Advantages of the Present Embodiment: As described above, in the measurement device 10 according to the present embodiment, during the first period ΔT1 from the emission timing t1 of the projector 20 to the delay timing t2, the light receiving sensitivity of the light receiving element is set lower than the reference sensitivity (see the timing chart V in FIG. 5 ). Therefore, even if the light receiving element receives reflected light L2 with a relatively high optical intensity during the first period ΔT1, electrical effects associated with photoelectric conversion in the light receiving element can be suppressed. Furthermore, in the present embodiment, during the second period ΔT2 after the delay timing t2, the light receiving sensitivity is set to the reference sensitivity (see the timing chart V in FIG. 5 ). Therefore, the distance to a long-distance object at a specified distance from the measurement device 10 can be measured. Thus, according to the present embodiment, electrical effects due to the reception of reflected light with a relatively high optical intensity can be suppressed while enabling the measurement of the distance to a long-distance object.

[0052] In this embodiment, the light receiving sensitivity of the light receiving element is set to the preliminary sensitivity (>0) during a third period of the first period ΔT1, which period includes a period immediately before the delay timing t2. According to this embodiment, compared to a configuration in which the light receiving sensitivity is suddenly increased from 0 to the reference sensitivity at the delay timing, for example, it is possible to suppress overshoot of the light receiving signal from the light receiving element in accordance with a change in the light receiving sensitivity.

[0053] In this embodiment, during the first period ΔT1, the light receiving sensitivity is increased stepwise or continuously so as to approach the reference sensitivity over time. According to this embodiment, it is possible to more effectively suppress overshoot of the light receiving signal from the light receiving element due to a change in the light receiving sensitivity.

[0054] FIG. 6 is a side cross-sectional view showing the internal configuration of a sensor package 70a of the comparative example. In the sensor package 70a of the comparative example, the light receiving unit 32 is housed in a recess 75 in a cavity 76a. However, the BPF 72 is disposed on the outer surface (top surface in FIG. 6 ) of the lid 78. In the comparative example, the BPF 72 allows the light receiving unit 32 to receive the emitted light L1, which is infrared light, and prevents light of other frequency bands from entering the light receiving unit 32. However, because the dielectric multilayer film 71 of the BPF 72 is always exposed to the outside, there is a risk that, for example, moisture adhering to the dielectric multilayer film 71 may cause deterioration or damage to the dielectric multilayer film 71, resulting in a decrease in light transmittance or a shift in the transmission band, which may adversely affect the light receiving performance of the optical receiver 30.

[0055] In contrast, according to this embodiment, as shown in FIG. 3 , the BPF 72 is housed in a recess 75 surrounded by a cavity 76 and a lid 78. That is, the dielectric multilayer film 71 is prevented from being exposed to the outside. This makes it possible to prevent a decrease in the light receiving performance of the optical receiver 30 due to deterioration or damage to the dielectric multilayer film 71. Furthermore, according to this embodiment, the size of the dielectric multilayer film 71 can be made smaller than in the comparative example, thereby reducing costs.

[0056] B. Modifications: The technology disclosed in this specification is not limited to the above-described embodiment, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0057] The configuration of the measuring device 10 in the above embodiment is merely an example and can be modified in various ways. For example, the projector 20 is of a flash type, but is not limited to this, and may be of a scanning type equipped with a scanner.

[0058] The flowchart of the measurement process in the above embodiment is merely an example, and various modifications are possible. For example, in the above embodiment, the light receiving sensitivity of the light receiving element is set to the preliminary sensitivity throughout the entire first period ΔT1. However, this is not limiting. The preliminary sensitivity may be set only for a portion of the first period ΔT1 (including immediately before the delay timing t2). Furthermore, the preliminary sensitivity may be constant and not increased. Furthermore, the light receiving sensitivity of the light receiving element may be set to zero throughout the entire first period ΔT1.

[0059] In the above embodiment, an example in which the light receiving sensitivity is changed using a SPAD has been described, but this is not limiting, and the light receiving sensitivity of an APD may be changed by changing the voltage applied to the APD. Also, an amplifier may be provided to amplify the light receiving signal from the light receiving element, and the light receiving sensitivity may be changed by controlling this amplifier.

[0060] FIG. 7 is a side cross-sectional view showing the internal configuration of a modified sensor package 70A. In the configuration of FIG. 3, the recess 75 of the cavity 76 is sealed with a lid 78. In contrast, in this modified example, the recess 75 of the cavity 76A is sealed with a BPF 72A. The BPF 72A includes a substrate 73A and a dielectric multilayer film 71A. The dielectric multilayer film 71A is formed on the inner surface of the substrate 73A facing the light receiving section 32 (recess 75). The dielectric multilayer film 71A is formed inside the periphery of the substrate 73A along its entire periphery. In other words, the dielectric multilayer film 71A is not present at the periphery of the substrate 73A. The periphery of the substrate 73A is bonded to the periphery of the opening of the cavity 76A via a bonding material 74.

[0061] According to this modification, the dielectric multilayer film 71A is prevented from being exposed to the outside, which makes it possible to prevent deterioration of the light receiving performance of the optical receiver 30 due to deterioration or damage to the dielectric multilayer film 71A. Note that the entire outer surface 77A of the substrate 73A (top surface in FIG. 7 ) is preferably coated with an anti-reflection film (AR coating).

[0062] This international application claims priority based on Japanese Patent Application No. 2024-019165, filed on February 13, 2024, the entire contents of which are incorporated herein by reference.

[0063] The above descriptions of specific embodiments of the present invention have been presented for purposes of illustration. They are not intended to be exhaustive or to limit the invention to the precise forms described. Numerous modifications and variations will be apparent to those skilled in the art in light of the above description.

[0064] 10: Measuring device 20: Light emitter 22: Light source 24: Light-emitting optical system 26: Light-emitting control device 28: Current source 30: Light receiver 32: Light-receiving section 32A: Light-receiving surface 34: Light-receiving optical system 40: TOF measuring device 42: Control circuit 50: Communication I / F 60: Utilizing device 61: Light-receiver housing 62: Substrate 63: Cylinder 64: Storage space 70, 70A, 70a: Sensor package 71, 71A: Dielectric multilayer film 72, 72A: BPF 73, 73A: Base material 74: Bonding material 75: Recess 75A: Step surface 76, 76A, 76a: Cavity 78: Lid

Claims

1. A control method for a measuring device equipped with a light projector that emits light and a light receiver having a light receiving element that receives light that is emitted by the light projector and reflected off a measurement object and returns, the method comprising: during a first period between the emission timing of the light projector and a delayed timing that is later than the emission timing, setting the light receiving sensitivity of the light receiving element to a lower level than a reference sensitivity that can detect a measurement object that is a specified distance away from the measuring device; during a second period after the delayed timing, setting the light receiving sensitivity to the reference sensitivity; and measuring the distance to the measurement object based on the light receiving signal from the light receiving element during the second period.

2. A control method for a measuring device as described in claim 1, wherein the light receiving sensitivity is set to a preliminary sensitivity that is greater than 0 and lower than the reference sensitivity during a third period of the first period that includes at least the period immediately before the delay timing.

3. A method for controlling a measuring device according to claim 2, wherein, during the third period, the light receiving sensitivity is increased stepwise or continuously so as to approach the reference sensitivity over time.

4. A method for controlling a measuring device according to claim 2 or 3, wherein the distance to the measurement object is measured based on the light receiving signal from the light receiving element during the third period.

5. A method for controlling a measuring device according to any one of claims 1 to 3, wherein the light receiving element is a SPAD, and the voltage applied to the SPAD is set to less than a breakdown voltage during the first period, and the voltage applied to the SPAD is set to equal to or greater than the breakdown voltage during the second period.

6. A measuring device comprising: a light projector that emits light; a light receiver having a light receiving element that receives reflected light that is emitted by the light projector and reflected back from an object to be measured, the light receiving element being configured to be able to change the light receiving sensitivity of the light receiving element; and a controller, wherein the controller, during a first period between the emission timing of the light projector and a delay timing that is later than the emission timing, lowers the light receiving sensitivity below a reference sensitivity that allows detection of an object to be measured that is a specified distance away from the measuring device; during a second period after the delay timing, sets the light receiving sensitivity to the reference sensitivity; and measures the distance to the object to be measured based on the light receiving signal from the light receiving element during the second period.

7. A control program for a measuring device that includes a light projector that emits light and a light receiver that has a light receiving element that receives reflected light that is emitted by the light projector and reflected back from an object to be measured, the light receiving element being configured to be able to change the light receiving sensitivity of the light receiving element, the program causing a controller to lower the light receiving sensitivity below a reference sensitivity that can detect an object to be measured that is a specified distance away from the measuring device during a first period between the emission timing of the light projector and a delay timing that is later than the emission timing, set the light receiving sensitivity to the reference sensitivity during a second period after the delay timing, and measure the distance to the object to be measured based on the light receiving signal from the light receiving element during the second period.

8. A computer-readable recording medium having recorded thereon a computer program for controlling a measuring device comprising a light projector that emits light and a light receiver that has a light receiving element that receives light that is reflected back from a measurement object when the light emitted by the light projector is reflected off the measurement object and returns, and that is configured to be able to change the light receiving sensitivity of the light receiving element, the computer program causing the measuring device to: during a first period between the emission timing of the light projector and a delay timing that is later than the emission timing, lower the light receiving sensitivity below a reference sensitivity that can detect a measurement object that is a specified distance away from the measurement device; during a second period after the delay timing, set the light receiving sensitivity to the reference sensitivity; and measure the distance to the measurement object based on the light receiving signal from the light receiving element during the second period.

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