Measurement device

Abstract

The present invention prevents reductions in the accuracy of a measurement device caused by the characteristics of a bandpass filter (BPF). A measurement device according to the present invention comprises a projector and a light receiver that receives reflected light of projection light projected by the projector. The projector has a wavelength control unit that controls the wavelength of the projection light and a scanning unit that scans the projection light, and the light receiver has a light reception unit that receives the reflected light and a BPF that limits a wavelength passband for the reflected light that is incident at the light reception unit. The incidence angle at which the reflected light is incident at the BPF changes in accordance with the scanning angle of the projection light. The projector shifts the wavelength of the projection light so as to suppress reductions in the amount of reflected light received by the light reception unit caused by shifts in the wavelength passband of the BPF in accordance with the incidence angle of the reflected light.

Description

Measuring equipment

[0001] The present invention relates to a measurement device, and more particularly to a technique for improving measurement accuracy.

[0002] This application claims priority based on Japanese Patent Nos. 2024-002133 and 2024-002142, both of which were filed on January 10, 2024, the entire disclosures of which are incorporated herein by reference.

[0003] Patent Document 1 describes a light receiving device configured to enable good detection of light of a predetermined wavelength over a wide angle of view. The light receiving device includes a light receiving element that receives light and performs photoelectric conversion, a light receiving optical system that guides the incident light to the light receiving element, and a bandpass filter that is inserted in the optical path of the light received by the light receiving element. The bandpass filter has a central wavelength of its light transmission band set to be longer than the predetermined wavelength, and has a light transmittance equal to or greater than a predetermined value when light of the predetermined wavelength is perpendicularly incident on the bandpass filter.

[0004] Patent Document 2 describes a liquid crystal wavelength tunable filter designed to reduce the incidence angle dependency. The liquid crystal wavelength tunable filter has a configuration in which at least one of a plurality of liquid crystal cells used has a boundary at the center of the cell thickness so that the rising angle of the liquid crystal director in the cell thickness direction is approximately symmetrical with respect to the center plane of the cell thickness.

[0005] JP 2005-175256 A JP 2008-197518 A

[0006] A measuring device such as LiDAR (Light Detection and Ranging) acquires information about an object present in a field of view based on the difference between the timing when a projector emits projected light toward the field of view and the timing when a receiver receives the reflected light of the projected light. The receiver uses a band pass filter (BPF) to limit the wavelength of the reflected light to a predetermined wavelength range in order to cut out background light such as sunlight that becomes noise. Some measuring devices are designed to change the wavelength of the projected light irradiated onto the object (field of view) in order to analyze the surface characteristics and structure in more detail.

[0007] Generally, the bandpass filters used in the above-mentioned measuring devices have a characteristic that the pass wavelength band shifts depending on the angle of incidence of the reflected light. Therefore, it is necessary to broaden the entire pass wavelength band beyond the wavelength range of the projected light, taking into account the shift depending on the angle of incidence of the reflected light and the wavelength of the projected light. However, broadening the pass wavelength band allows a large amount of background light to enter the light receiving unit, which reduces the accuracy of the measuring device.

[0008] In Patent Document 1, the center wavelength of the light transmission band of a bandpass filter is set to be longer than a predetermined wavelength, so that light of the predetermined wavelength can pass through even when the angle of incidence on the bandpass filter is large. However, this document fixes the center wavelength of the bandpass filter, and is therefore unable to accommodate changes in the angle of incidence of reflected light on the bandpass filter or the wavelength of the projected light as the projected light scans. Furthermore, this document does not specifically mention a mechanism for suppressing noise reduction due to background light.

[0009] The present invention has been made in view of the above background, and has as its object to provide a measurement device that can prevent a decrease in measurement accuracy due to the characteristics of a bandpass filter.

[0010] One aspect of the present invention for achieving the above object is a measuring device comprising a light projector and a light receiver that receives reflected light of projected light projected by the light projector toward a field of view range, wherein the light projector has a wavelength control unit that controls the wavelength of the projected light and a scanning unit that scans the projected light, the light receiver has a light receiving unit that receives the reflected light and an optical element that limits the pass wavelength band of the reflected light that enters the light receiving unit, wherein the angle of incidence of the reflected light that enters the optical element changes according to the scanning angle of the projected light, the optical element has a property that the pass wavelength band shifts according to the angle of incidence of the reflected light, and the light projector shifts the wavelength of the projected light so as to suppress a decrease in the amount of reflected light received by the light receiving unit caused by the shift in the pass wavelength band according to the angle of incidence.

[0011] Another aspect of the present invention for achieving the above object is a measuring device comprising a light projector and a light receiver that receives reflected light of projected light projected by the light projector toward a field of view range, wherein the light projector has a wavelength control unit that controls the wavelength of the projected light and a scanning unit that scans the projected light, the light receiver has a light receiving unit that receives the reflected light and an optical element that limits a pass wavelength band of the reflected light that enters the light receiving unit, wherein the angle of incidence of the reflected light that enters the optical element changes according to the scanning angle of the projected light, and the optical element has a property that the pass wavelength band shifts according to the angle of incidence, the light receiver has a band control unit that shifts the pass wavelength band, and the band control unit shifts the pass wavelength band of the optical element according to at least one of the wavelength of the projected light and the angle of incidence of the reflected light that enters the optical element so as to suppress a decrease in the amount of reflected light received by the light receiving unit due to a change in the wavelength of the projected light.

[0012] Other problems and solutions disclosed in the present application will be made clear in the detailed description and drawings.

[0013] According to the present invention, it is possible to prevent a decrease in the accuracy of the measuring device due to the characteristics of the bandpass filter.

[0014] Fig. 1 is a diagram showing a schematic configuration of a measurement device according to a first embodiment; Fig. 2 is a diagram explaining the angle dependency of a passing wavelength band of a bandpass filter (BPF); Fig. 3 is a diagram explaining a scanning angle; Fig. 4 is a diagram explaining an incident angle; Fig. 5 is a flowchart explaining wavelength control processing; Fig. 6 is a diagram showing a schematic configuration of a measurement device according to a second embodiment; Fig. 7 is a flowchart explaining notification processing; Fig. 8 is a flowchart explaining band limiting processing;

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0016] 1 shows a schematic configuration (block diagram) of a measurement device 1 shown as a first embodiment. The measurement device 1 includes a projector 10 that projects (emits, irradiates) projected light (irradiation light, light beam) toward a field of view 5, a photoreceiver 20 that receives reflected light (returned light) that is returned after the projected light is reflected by an object (such as a measurement target) present in the field of view 5, a TOF measurement device 30, and a calculation device 40.

[0017] The measuring device 1 obtains information about the measurement target, etc. (distance to the measurement target, range in which the measurement target exists, etc.) by measuring the time difference (time of flight of light (projected light and reflected light), hereinafter referred to as "TOF" (Time Of Flight)) between the time when the projector 10 emits the projected light and the time when the receiver 20 receives the reflected light.

[0018] The measuring device 1 functions as, for example, a LiDAR (Light Detection and Ranging) device. The measuring device 1 is mounted on a vehicle such as an automobile equipped with an AD (Autonomous Driving) system or an ADAS (Advanced Driver Assistance System), and assists in the detection of people, other vehicles, and objects while the vehicle is traveling, and provides various types of information to other devices and users that are 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.

[0019] As shown in the figure, the light projector 10 includes a light emitting unit 11, a scanning unit 12, and a light projection control device 13. The light projector 10 may further include an optical component such as a collimating lens.

[0020] The light-emitting unit 11 is configured using a light-emitting element (e.g., a wavelength-tunable laser) that can control the wavelength of the emitted light. The light-emitting unit 11 is configured using, for example, one or more light-emitting elements, 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 vertical cavity surface-emitting laser (VCSEL), 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.).

[0021] The scanning unit 12 scans (controls the light distribution) the projected light by, for example, applying an optical effect (such as refraction, scattering, or diffraction) to the light beam generated by the light-emitting element of the light-emitting unit 11. The type of scanning unit 12 is not necessarily limited. For example, the scanning unit 12 may be a mechanical type (such as a tilt mirror type, a polygon mirror type, a rotating head type, or a MEMS (Micro Electro Mechanical Systems) mirror type) that uses reflected light (mirror), or may be a solid-state type (such as an optical phased array type, a photonic crystal type, or a liquid crystal type).

[0022] As shown in the figure, the light-projection control device 13 has the functions of an emission control unit 131, a scanning control unit 132, and a wavelength control unit 133. The light-projection control device 13 is configured using, for example, an information processing device (computer) having a processor (such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), FPGA (Field Programmable Gate Array), or ASIC (Application Specific Integrated Circuit)) and a storage device (such as a ROM (Read Only Memory), RAM (Random Access Memory), or NVRAM (Non Volatile RAM)). The functions of the light-projection control device 13 are realized by the processor reading and executing a program stored in the storage device.

[0023] Of the above functions, the light emission control unit 131 controls the current (drive current) supplied from a current source (not shown) to the light emitting elements of the light emitting unit 11. The light emission control unit 131 also inputs a signal indicating the timing at which the light emitting elements emit light (the timing at which projected light is emitted from the light emitting elements; hereinafter referred to as "light projection timing") to the TOF measurement device 30. The light emission control unit 131 periodically controls the on / off of a current flowing through each of the light emitting elements, thereby causing the light emitting elements to periodically emit light.

[0024] The scanning control unit 132 electrically or mechanically controls the scanning unit 12 to scan the emission direction of the projected light (scanning angle (the angle between a reference axis Z, which will be described later, and the projected light) (controls the light distribution of the projected light).

[0025] The wavelength control unit 133 controls the wavelength of the projected light emitted from the light-emitting element of the light-emitting unit 11. The wavelength control unit 133 also notifies the photoreceiver 20 of information indicating the wavelength of the projected light currently being projected. The wavelength control unit 133 is configured using, for example, a so-called distributed Bragg reflector laser (DBR) that controls the characteristic wavelength and refractive index by using a diffraction grating or one or more optical filters having wavelength selectivity, or a micromachine laser that selects the wavelength by mechanically rotating an optical filter that uses a diffraction grating or the like.

[0026] The optical receiver 20 has a light receiving section 21 and a band pass filter (hereinafter referred to as a "BPF 22"). The optical receiver 20 collects reflected light, which is light projected by the projector 10 and reflected by an object present in the field of view 5, onto the optical receiver 21. The optical receiver 20 may further include optical components such as various lenses, such as a condensing lens, and a reflecting mirror.

[0027] The light receiving unit 21 photoelectrically converts the incident reflected light to generate a current (hereinafter referred to as a "photocurrent") corresponding to the intensity of the reflected light. The light receiving unit 21 is configured, for example, using one or more light receiving elements or a light receiving element array (for example, light receiving elements arranged linearly (one-dimensionally) or planarly (two-dimensionally)). The light receiving elements are, for example, photodiodes or balanced photodetectors. The light receiving element array is, for example, a SPAD (Single Photon Avalanche Diode). The light receiving unit 21 inputs, to the TOF measurement device 30, a signal indicating the timing at which each light receiving element constituting the light receiving unit 21 receives reflected light (hereinafter referred to as a "light receiving timing"), and the light receiving current generated by each light receiving element 211.

[0028] The BPF 22 limits the wavelength of the reflected light to a predetermined wavelength band, thereby cutting out background light that becomes noise, such as sunlight. As shown in Fig. 2, the BPF 22 has a characteristic that the pass wavelength band shifts according to the angle of incidence of the reflected light, based on the currently set pass wavelength band (for example, the pass wavelength band shifts to the shorter wavelength side as the angle of incidence increases).

[0029] The TOF measurement device 30 calculates the TOF based on a signal indicating the light projection timing input from the light-projection control device 13 and a signal indicating the light reception timing input from the light-receiving unit 21. The TOF measurement device 30 is configured using, for example, a time measurement IC (Integrated Circuit) equipped with a TDC (Time to Digital Converter) circuit. The TOF measurement device 30 inputs the calculated TOF and the light-receiving current input from the light-receiving unit 21 to the calculation device 40.

[0030] The arithmetic unit 40 is configured using a processor (such as a CPU, MPU, ASIC, FPGA, or DSP (Digital Signal Processor)). The arithmetic unit 40 generates information used for various measurements such as object (measurement target, etc.) detection and distance measurement based on the photocurrent and TOF input from the TOF measurement device 30. The information includes, for example, a histogram used in time-correlated single photon counting, distances to each point on the object (measurement target, etc.), a point cloud (point cloud information), etc.

[0031] The arithmetic unit 40 controls the light projector 10 and the light receiver 20. By controlling the light projector 10 and the light receiver 20, the arithmetic unit 40 controls the timing of light projection and the timing of light reception described above, for example, to speed up or optimize the processing for generating a histogram. The information generated by the arithmetic unit 40 is provided (transmitted) via the communication I / F 45 to devices that use the information (hereinafter referred to as "various use devices 50").

[0032] The various utilization devices 50 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.).

[0033] <Scanning Angle and Incident Angle> Fig. 3A is a diagram illustrating the scanning angle in a case where the light-emitting unit 11 is configured using a two-dimensional light-emitting element array and the projector 10 is configured so that the scanning unit 12 selects light-emitting elements of the light-emitting element array to emit light, thereby scanning the projected light (projected beam).

[0034] In the figure, for example, a line passing through the center of the surface of the light-emitting element array and the center of the optical element (such as a collimator lens) is taken as the reference axis Z, and the angle between the reference axis Z and the emission direction of the projected light is taken as the scan angle. In this example, the scan control unit 132 determines the scan angle of the projected light based on, for example, which light-emitting element of the light-emitting element array has been selected by the scanning unit 12.

[0035] 3B is a diagram illustrating the angle of incidence when the light receiving element 211 constituting the light receiving unit 21 is configured using a two-dimensional light receiving element array. In the case of this diagram, for example, a line passing through the surface center of the light receiving element 211 and the surface center of the BPF 22 is defined as a reference axis Z', and the angle formed by the reference axis Z' and the incident direction of the reflected light is defined as the angle of incidence.

[0036] <Wavelength control unit> The wavelength control unit 133 shifts (changes) the wavelength of the projected light so as to suppress a decrease in the amount of reflected light received by the light receiving unit 21 due to a shift in the pass wavelength band depending on the incident angle of the reflected light to the BPF 22.

[0037] For example, if the BPF 22 has a characteristic that the passing wavelength band shifts to the shorter wavelength side as the incident angle increases, the wavelength control unit 133 shifts the wavelength of the projected light to the shorter wavelength side as the incident angle of the reflected light to the BPF 22 increases. Note that the incident angle of the reflected light to the BPF 22 is uniquely determined depending on the scanning angle of the projected light that generated the reflected light.

[0038] The wavelength control unit 133 stores information indicating the correspondence between the scanning angle and the incident angle (hereinafter referred to as "scanning angle / incident angle correspondence information"), and determines the current incident angle of the reflected light by comparing the current scanning angle of the projected light with the scanning angle / incident angle correspondence information.

[0039] In addition, the wavelength control unit 133 stores information indicating the correspondence between the incident angle of the reflected light onto the BPF 22 and the shift amount of the pass wavelength band (hereinafter referred to as "incident angle / shift amount correspondence information"), and by comparing the current incident angle of the reflected light with the incident angle / shift amount correspondence information, the shift amount of the pass wavelength band corresponding to the incident angle is determined.

[0040] The wavelength control unit 133 also stores information (hereinafter referred to as "pass wavelength band / optimal wavelength correspondence information") indicating the correspondence with the optimal wavelength of reflected light (projected light) corresponding to the pass wavelength band (the optimal wavelength (e.g., the central wavelength of the pass wavelength band; hereinafter referred to as the "optimal wavelength") for suppressing a decrease in the amount of reflected light received by the light receiving unit 21), and determines the optimal wavelength corresponding to the shifted pass wavelength band, and shifts the wavelength of the projected light to the optimal wavelength.

[0041] The above-described scan angle / incident angle correspondence information is created, for example, by conducting experiments, simulations, or the like in advance in accordance with the configuration of the measurement device 1. The incident angle / shift amount correspondence information is created in advance, for example, from information on the specifications of the BPF 22 and by conducting tests on the BPF 22. The pass wavelength band / optimum wavelength correspondence information is created in advance, for example, from information on the specifications of the BPF 22 and by conducting tests on the BPF 22.

[0042] 4 is a flowchart illustrating a process (hereinafter referred to as "wavelength control process S400") performed by the light-projection control device 13 of the projector 10 in wavelength control according to the angle of incidence of reflected light on the BPF 22. The wavelength control process S400 will be described below with reference to the same figure.

[0043] As shown in the figure, the light-projection control device 13 of the light projector 10 monitors in real time whether the scan angle of the projected light has changed as a result of the scan control unit 132 controlling the scanning unit 12 (S411: No). If it detects that the scan angle of the projected light has changed (S411: Yes), the process proceeds to S412.

[0044] In S412, the light projection control device 13 compares the changed scanning angle of the current projected light with the scanning angle / incident angle correspondence information to find the incident angle of the reflected light of the projected light on the BPF 22 (S412).

[0045] Next, the light projection control device 13 compares the determined incident angle with the incident angle / shift amount correspondence information to determine the shift amount of the passing wavelength band of the BPF 22 corresponding to the determined incident angle (S413).

[0046] Next, the light projection control device 13 compares the determined shift amount of the pass wavelength band with the pass wavelength band / optimum wavelength correspondence information to determine the optimum wavelength of the reflected light (projected light) corresponding to the determined shift amount (S414).

[0047] Next, the light-projection control device 13 shifts the wavelength of the projected light so that it becomes the optimum wavelength thus found (S415), after which the process returns to S411.

[0048] <Technical Effects, etc.> As described above, the measurement device 1 of this embodiment shifts the wavelength of the projected light so as to suppress a decrease in the amount of reflected light received by the light receiving unit 21, which is caused by a shift in the pass wavelength band depending on the angle of incidence of the reflected light on the BPF 22. Therefore, it is possible to prevent a decrease in measurement accuracy caused by a change in the angle of incidence of the reflected light incident on the BPF 22, without widening the pass wavelength band of the BPF 22.

[0049] Furthermore, since the angle of incidence of the reflected light into BPF 22 is determined according to the scanning angle of the projected light, by controlling the wavelength of the projected light to shift according to the scanning angle of the projected light, the wavelength of the projected light can be appropriately shifted by an amount corresponding to the shift in the pass wavelength band.

[0050] 5 shows a schematic configuration (block diagram) of a measurement device 1 shown as a second embodiment. The measurement device 1 of the second embodiment includes a projector 10, a receiver 20, a TOF measurement device 30, and a calculation device 40. The following description will focus on the differences from the first embodiment.

[0051] As shown in the figure, the floodlight 10 includes a light-emitting unit 11, a scanning unit 12, and a light-projection control device 13. The floodlight 10 may further include optical components such as a collimating lens. The light-emitting unit 11 and the scanning unit 12 are similar to those of the floodlight 10 of the first embodiment.

[0052] As shown in the figure, the light projection control device 13 has the functions of a light emission control unit 131 , a scanning control unit 132 , and a wavelength control unit 133 .

[0053] Of these, the light emission control unit 131 controls the current (drive current) supplied from a current source (not shown) to the light emitting elements of the light emitting unit 11. The light emission control unit 131 also inputs a signal indicating the timing at which the light emitting elements emit light (the timing at which projected light is emitted from the light emitting elements; hereinafter referred to as "light projection timing") to the TOF measurement device 30. The light emission control unit 131 periodically causes the light emitting elements to emit light repeatedly, for example, by periodically turning on and off the current flowing through each of the light emitting elements.

[0054] The scanning control unit 132 scans the projected light (controls the light distribution of the projected light) by electrically or mechanically controlling the scanning unit 12. The scanning control unit 132 also notifies the photoreceiver 20 of information indicating the scanning angle of the currently projected projected light (the angle between the reference axis Z, which will be described later, and the projected light).

[0055] The wavelength control unit 133 controls the wavelength of the projected light emitted from the light-emitting element of the light-emitting unit 11. The wavelength control unit 133 also notifies the photoreceiver 20 of information indicating the wavelength of the projected light currently being projected. The wavelength control unit 133 is configured using, for example, a distributed Bragg reflector laser (DBR) that controls the characteristic wavelength and refractive index by using a diffraction grating or one or more optical filters having wavelength selectivity, or a micromachine laser that selects the wavelength by mechanically rotating an optical filter that uses a diffraction grating or the like.

[0056] The light-projection control device 13 is configured using, for example, an information processing device (computer) having a processor (CPU, MPU, FPGA, ASIC, etc.), a storage device (ROM, RAM), and a non-volatile memory (NVRAM, etc.). The functions of the light-projection control device 13 are realized by the processor reading and executing a program stored in the storage device. Although not shown in the figure, the light-projection control device 13 also has a function of communicating with a bandwidth control unit 23 (described later) of the optical receiver 20 using a predetermined communication method.

[0057] The optical receiver 20 has a light receiving section 21, a band pass filter (hereinafter referred to as a "BPF 22"), and a band control section 23. The optical receiver 20 collects, onto the optical receiver 21, reflected light that is returned after being projected by the projector 10 and reflected by an object present in the field of view 5. The optical receiver 20 may further include optical components such as various lenses, such as a focusing lens, and a reflecting mirror.

[0058] The light receiving section 21 is the same as that in the first embodiment.

[0059] The BPF 22 limits the wavelength of the reflected light to a predetermined wavelength band, thereby cutting out background light that becomes noise, such as sunlight. As shown in Fig. 2, the BPF 22 has a characteristic that the pass wavelength band shifts according to the angle of incidence of the reflected light, based on the currently set pass wavelength band (for example, the pass wavelength band shifts to the shorter wavelength side as the angle of incidence increases).

[0060] The BPF 22 is configured using, for example, a wavelength-variable filter using liquid crystal, and is capable of changing the pass wavelength band by changing the transmittance of light of a specific wavelength.

[0061] The band control unit 23 controls the passing wavelength band of the BPF 22. For example, if the BPF 22 is a wavelength tunable filter using liquid crystal, the band control unit 23 controls the passing wavelength band of the BPF 22 by changing a voltage that controls the orientation of liquid crystal elements of the BPF 22. The band control unit 23 controls the passing wavelength band of the BPF 22 based on the scanning angle of the currently projected light and the wavelength of the currently projected light, which are notified by the light-projection control device 13.

[0062] The band control unit 23 is configured using, for example, an information processing device (computer) having a processor (CPU, MPU, FPGA, ASIC, etc.), a storage device (RAM, ROM, NVRAM, etc.), a voltage control circuit, etc. The functions of the band control unit 23 are realized by the processor reading and executing a program stored in the storage device. Although not shown in the figure, in addition to the above functions, the band control unit 23 also has a function of communicating with the projection control device 13 of the floodlight 10 using a predetermined communication method.

[0063] The TOF measurement device 30, the calculation device 40, and the various utilization devices 50 are the same as those in the first embodiment.

[0064] <Band control unit> The band control unit 23 shifts the pass wavelength band of the BPF 22 in accordance with the wavelength of the projected light and the angle of incidence of the reflected light entering the BPF 22, so as to suppress a decrease in the amount of reflected light received by the light receiving unit 21 due to a change in the wavelength of the projected light.

[0065] For example, if the BPF 22 has a characteristic that the pass wavelength band shifts to the shorter wavelength side as the incident angle increases, the band control unit 23 shifts the pass wavelength band of the BPF 22 to the shorter wavelength side as the incident angle of the reflected light to the BPF 22 increases. Also, the band control unit 23 shifts the pass wavelength band of the BPF 22 to the shorter wavelength side as the wavelength of the reflected light (the wavelength of the projected light) decreases.

[0066] The band control unit 23 stores information indicating the correspondence between the incident angle of the reflected light and the shift amount of the pass wavelength band (hereinafter referred to as "incident angle / shift amount correspondence information"). By comparing the incident angle of the reflected light with the incident angle / shift amount correspondence information, the band control unit 23 determines the shift amount of the pass wavelength band of the BPF 22 that is optimal for suppressing a decrease in the amount of received reflected light, and shifts the pass wavelength band of the BPF 22 by the determined shift amount.

[0067] The incident angle of the reflected light on the BPF 22 is uniquely determined according to the scanning angle of the projected light that generated the reflected light. The band control unit 23 stores information indicating the correspondence between the scanning angle and the incident angle (hereinafter referred to as "scanning angle / incident angle correspondence information"), and obtains the incident angle of the reflected light on the BPF 22 by comparing the scanning angle notified by the scanning control unit 132 with the scanning angle / incident angle information.

[0068] The band control unit 23 also stores information (hereinafter referred to as "wavelength / passband correspondence information") indicating the relationship between the wavelength of the reflected light (projected light) and the pass wavelength band of the BPF 22 that is optimal for suppressing a decrease in the amount of received reflected light. The band control unit 23 compares the wavelength of the reflected light (projected light) with the wavelength / passband correspondence information to determine the amount of shift of the pass wavelength band of the BPF 22 that is optimal for suppressing a decrease in the amount of received reflected light, and shifts the pass wavelength band of the BPF 22 by the determined amount of shift.

[0069] The incident angle / shift amount correspondence information is generated in advance, for example, by collecting information on the specifications of the BPF 22 and conducting tests on the BPF 22. The scan angle / incident angle correspondence information is generated in advance, for example, by conducting experiments, simulations, or the like in accordance with the configuration of the measurement device 1. The wavelength / passband correspondence information is generated in advance, for example, by collecting information on the specifications of the BPF 22 and conducting tests on the BPF 22.

[0070] <Processing Example> Fig. 6A is a flowchart illustrating processing (hereinafter referred to as "notification processing S600") performed by the light-projecting control device 13 of the projector 10 in controlling the pass wavelength band of the BPF 22. Fig. 6B is a flowchart illustrating processing (hereinafter referred to as "band control processing S650") performed by the band control unit 23 of the optical receiver 20 in relation to control of the pass wavelength band of the BPF 22. Below, the processing performed by the measurement device 1 in controlling the pass wavelength band of the BPF 22 will be described with reference to these figures.

[0071] As shown in FIG. 6A , in the notification process S600, the light-projection control device 13 of the light projector 10 monitors in real time whether the scan angle of the projected light has changed as a result of the scanning control unit 132 controlling the scanning unit 12 (S611). When detecting that the scan angle of the projected light has changed (S611: Yes), the light-projection control device 13 notifies the bandwidth control unit 23 of the light receiver 20 of the current scan angle of the projected light (S612).

[0072] The light-projection control device 13 also monitors in real time whether the wavelength of the projected light has changed under the control of the wavelength control unit 133 (S613). When it detects that the wavelength of the projected light has changed (S613: Yes), the light-projection control device 13 notifies the band control unit 23 of the optical receiver 20 of the current wavelength of the projected light (S614). Thereafter, the process returns to S611.

[0073] As shown in FIG. 6B , in the band control process S650, the band control unit 23 of the receiver 20 monitors in real time whether or not a notification of the current scan angle or a notification of the current wavelength has been received from the light-projection control device 13 of the transmitter 10 (S651).

[0074] When the bandwidth control unit 23 detects that it has received a notification from the light-projection control device 13 (S651: Yes), it determines whether the received notification is a notification of the current scan angle of the projected light (S652). If the received notification is not a notification of the current scan angle (S652: No), the process proceeds to S655.

[0075] On the other hand, if the received notification is a notification of the current scanning angle (S652: Yes), the band control unit 23 controls the passing wavelength band of the BPF 22 based on the notified scanning angle so as to suppress a decrease in the amount of reflected light received by the light receiving unit 21 due to a change in the scanning angle of the projected light.

[0076] Specifically, first, the band control unit 23 finds the incident angle of the reflected light to the BPF 22 by comparing the notified current scanning angle with the scanning angle / incident angle correspondence information (S653).

[0077] Next, the band control unit 23 compares the determined incident angle with the incident angle / shift amount correspondence information to determine the shift amount of the pass wavelength band of the BPF 22 that is optimal for suppressing a decrease in the amount of received reflected light, and shifts the pass wavelength band of the BPF 22 by the determined shift amount (S654).Then, the process proceeds to S655.

[0078] In S655, the bandwidth control unit 23 determines whether the notification received in S651 is a notification of the current wavelength of the projected light. If the received notification is not a notification of the current wavelength of the projected light (S655: No), the process returns to S651.

[0079] On the other hand, if the received notification is a notification of the current wavelength of the projected light (S655: Yes), the band control unit 23 controls the passing wavelength band of the BPF 22 based on the notified wavelength so as to suppress a decrease in the amount of reflected light received by the light receiving unit 21 due to a change in the wavelength of the projected light.

[0080] Specifically, the band control unit 23 compares the notified current wavelength with the wavelength / passband correspondence information to determine the optimum shift amount of the passband of the BPF 22 to suppress a decrease in the amount of received reflected light, and shifts the passband of the BPF 22 by the determined shift amount (S656).The process then returns to S651.

[0081] In the above, the light-projection control device 13 notifies the band control unit 23 of the receiver 20 of the scanning angle or wavelength of the projected light when the scanning angle or wavelength of the projected light changes, but the light-projection control device 13 may also be configured to notify the band control unit 23 of the scanning angle and wavelength of the projected light at all times (in real time).

[0082] <Technical Effects, etc.> As described above, the measurement device 1 of this embodiment shifts the pass wavelength band of the BPF 22 in accordance with at least one of the wavelength of the projected light and the angle of incidence of the reflected light incident on the optical element, so as to suppress a decrease in the amount of reflected light received by the light receiving unit 21, which is caused by a change in the wavelength of the projected light. Therefore, it is possible to prevent a decrease in measurement accuracy caused by a change in the angle of incidence or wavelength of the reflected light incident on the BPF 22, without widening the pass wavelength band of the BPF 22.

[0083] Furthermore, since the angle of incidence of the reflected light onto the BPF 22 is determined according to the scanning angle of the projected light, by controlling the wavelength of the projected light to change according to the scanning angle of the projected light, the wavelength of the projected light can be appropriately changed by an amount corresponding to the shift in the pass wavelength band.

[0084] Furthermore, by using a wavelength-variable filter using liquid crystal as the BPF 22, it is possible to easily realize a mechanism for shifting the pass wavelength band of the BPF 22 depending on the wavelength of the projected light and the angle of incidence of the reflected light entering the BPF 22.

[0085] [Summary] Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments and includes various modifications. Furthermore, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, some of the configurations of the above-described embodiments can be added to, deleted from, or replaced with other configurations.

[0086] REFERENCE SIGNS LIST 1 Measurement device 5 Field of view range 10 Light projector 11 Light emitting unit 12 Scanning unit 13 Light projection control device 131 Light emission control unit 132 Scanning control unit 133 Wavelength control unit 20 Light receiver 21 Light receiving unit 22 BPF 23 Bandwidth control unit 30 TOF measurement device 40 Arithmetic unit 45 Communication I / F 50 Various utilization devices S400 Wavelength control process S450 Bandwidth control process

Claims

1. A measuring device comprising: a projector; a light receiver that receives reflected light of the projected light projected by the projector toward a visual field range; the projector having a wavelength control unit that controls the wavelength of the projected light and a scanning unit that scans the projected light; the light receiver having a light receiving unit that receives the reflected light and an optical element that restricts a passing wavelength band of the reflected light incident on the light receiving unit; an incident angle of the reflected light incident on the optical element changing according to a scanning angle of the projected light; the optical element having a property that the passing wavelength band shifts according to the incident angle of the reflected light; and the projector shifting the wavelength of the projected light so as to suppress a decrease in the amount of received light of the reflected light by the light receiving unit due to the shift of the passing wavelength band according to the incident angle.

2. The measuring device according to claim 1, wherein the projector shifts the wavelength of the projected light according to a scanning angle of the projected light.

3. The measuring device according to claim 1, wherein the projector shifts the wavelength of the projected light by an amount corresponding to a shift amount of the passing wavelength band according to an incident angle of the reflected light on the optical element.

4. The measuring device according to claim 3, wherein the projector shifts the wavelength of the projected light according to the scanning angle such that the wavelength of the projected light becomes shorter as the incident angle becomes larger.

5. The measuring device according to claim 1, wherein the optical element is a band-pass filter.

6. A measuring device comprising: a projector; a light receiver that receives the reflected light of the projected light projected by the projector toward the field of view; the projector having a wavelength control unit that controls the wavelength of the projected light and a scanning unit that scans the projected light; the light receiver having a light receiving unit that receives the reflected light and an optical element that restricts the passing wavelength band of the reflected light incident on the light receiving unit; the incident angle of the reflected light incident on the optical element changing according to the scanning angle of the projected light; the optical element having a property that the passing wavelength band shifts according to the incident angle; the light receiver having a band control unit that shifts the passing wavelength band; the band control unit shifting the passing wavelength band of the optical element according to at least one of the wavelength of the projected light and the incident angle of the reflected light incident on the optical element so as to suppress a decrease in the amount of received reflected light of the light receiving unit caused by a change in the wavelength of the projected light.

7. The measuring device according to claim 6, wherein the projector changes the wavelength of the projected light according to the scanning angle of the projected light.

8. The measuring device according to claim 6, wherein the optical element is a wavelength variable filter using liquid crystal, which is capable of changing the transmittance of light of a specific wavelength.

9. The measuring device according to claim 6, wherein the optical element is a band-pass filter.

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