Distance measuring device and optical system

Abstract

A distance measuring device according to the present disclosure comprises: a light reception unit that outputs a pixel signal in response to received light; an optical element that changes and emits an optical path of incident light; and a distance measuring unit that performs distance measurement on the basis of the time at which light is emitted from a light source and the time at which the light is received by the light reception unit. The optical element is provided on an optical path from emission of light from the light source to reception of reflected light by the light reception unit, the reflected light being produced by said light being reflected by an object. The optical path is changed in accordance with the distance between the light source or the light reception unit and the object.

Description

Range finder and optical system

[0001] The present disclosure relates to a distance measuring device and an optical system.

[0002] Distance measuring devices are known that measure distance by projecting light using a laser and detecting the light reflected from the target. For example, LiDAR (Laser Imaging Detection and Ranging) uses a distance measuring method called a direct Time of Flight (ToF) method, in which laser light emitted from a light source is reflected by a target and the reflected light is received by a sensor, and the distance to the target is measured based on the time from when the light is emitted until it is received as reflected light.

[0003] International Publication No. 2021 / 161857

[0004] In order to perform distance measurement with higher accuracy in such a distance measuring device, it is necessary to appropriately detect reflected light of the laser light emitted from the light source.

[0005] Therefore, an object of the present disclosure is to provide a distance measuring device and an optical system that are capable of measuring distances with higher accuracy when measuring distances based on reflected light when light is projected onto a target.

[0006] The distance measuring device according to the present disclosure comprises a light receiving unit that outputs a pixel signal in response to the received light, an optical element that changes the optical path of the incident light and then emits it, and a distance measuring unit that measures distance based on the time when light is emitted from the light source and the time when the light is received by the light receiving unit, wherein the optical element is arranged on the optical path from when light is emitted from the light source to when the light reflected by an object is received by the light receiving unit, and changes the optical path in response to the distance between the light source or the light receiving unit and the object.

[0007] 1 is a diagram schematically illustrating distance measurement using a direct ToF method that can be applied to each embodiment; FIG. 2 is a diagram illustrating an example histogram based on the time at which a light receiving unit receives light, that can be applied to each embodiment; FIG. 3 is a block diagram illustrating the configuration of an example of an electronic device using a distance measurement device according to each embodiment; FIG. 4 is a block diagram illustrating the configuration of an example of a distance measurement device that can be applied to each embodiment in more detail; FIG. 5 is a schematic diagram illustrating a first example configuration of an optical system related to distance measurement using a direct ToF method according to existing technology; FIG. 6 is a schematic diagram illustrating a second example configuration of an optical system related to distance measurement using a direct ToF method according to existing technology; FIG. 7 is a schematic diagram illustrating a degradation in distance measurement performance at close range due to parallax; FIG. 8 is a schematic diagram illustrating a configuration of an example according to a first embodiment; FIG. 9 is a schematic diagram illustrating a configuration of an example according to a modification of the first embodiment; FIG. 10 is a schematic diagram illustrating a configuration of an example according to a second embodiment; FIG. 11 is a schematic diagram illustrating a configuration of an example according to a third embodiment; and FIG. 12 is a schematic diagram illustrating a configuration of an example according to a fourth embodiment. FIG. 10 is a schematic diagram showing a configuration of an example according to a fourth embodiment. FIG. 11 is a schematic diagram for explaining the influence of flare on distance measurement. FIG. 12 is a block diagram showing a configuration of an example of a distance measurement system applicable to a fifth embodiment. FIG. 13 is a block diagram showing a configuration of an example of a light-emitting unit applicable to the fifth embodiment. FIG. 14 is a block diagram showing a configuration of an example of a light-receiving unit applicable to the fifth embodiment. FIG. 15 is a schematic diagram showing a basic configuration example of a pixel Pix using a SPAD as a light-receiving element, included in a pixel array unit, applicable to the fifth embodiment. FIG. 16 is a schematic diagram showing a configuration of an example of a scanning mechanism applicable to the fifth embodiment. FIG. 17 is a schematic diagram for explaining distance measurement according to the fifth embodiment. FIG. 18 is a schematic diagram for explaining another example of distance measurement according to the fifth embodiment. FIG. 19 is a flowchart of an example of distance measurement processing according to the fifth embodiment. FIG. 19 is a schematic diagram for explaining saturation detection applicable to the fifth embodiment. FIG. 19 is a block diagram showing a configuration of an example of a light-emitting unit according to a first modification of the fifth embodiment. FIG. 19 is a schematic diagram for explaining distance measurement according to a second modification of the fifth embodiment.FIG. 10 is a schematic diagram for explaining an example in which reflected light due to strong light emission is acquired in a weak light emission region. FIG. 11 is a schematic diagram for explaining distance measurement according to a third modified example of the fifth embodiment. FIG. 12 is a flowchart of an example of distance measurement processing according to the third modified example of the fifth embodiment. FIG. 13 is a schematic diagram for explaining the influence of stray light inside a housing. FIG. 14 is a schematic diagram for explaining distance measurement according to a fourth modified example of the fifth embodiment. FIG. 15 is a flowchart of an example of distance measurement processing according to the fourth modified example of the fifth embodiment. FIG. 16 is a block diagram showing an example of a schematic configuration of a vehicle control system. FIG. 17 is an explanatory diagram showing an example of the installation positions of an outside vehicle information detection unit and an imaging unit.

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, the same components are denoted by the same reference numerals, and redundant description will be omitted.

[0009] Hereinafter, embodiments of the present disclosure will be described in the following order: 1. Technology applicable to the present disclosure 1-1. Overview of direct ToF 1-2. Configuration applicable to the present disclosure 2. Existing technology 3. Overview of embodiments of the present disclosure 4. First embodiment 4-1. Modified example of the first embodiment 5. Second embodiment 5-1. Modified example of the second embodiment 6. Third embodiment 7. Fourth embodiment 8. Fifth embodiment 8-1. Existing technology 8-2. Overview of the fifth embodiment 8-3. Configuration applicable to the fifth embodiment 8-4. Processing according to the fifth embodiment 8-5. First modified example of the fifth embodiment 8-6. Second modified example of the fifth embodiment 8-7. Third modified example of the fifth embodiment 8-8. Fourth modified example of the fifth embodiment 9. Sixth embodiment

[0010] (1. Techniques Applicable to the Present Disclosure) Techniques applicable to the present disclosure will be described.

[0011] (1-1. Outline of Direct ToF) Distance measurement using the direct ToF (Time of Flight) method will be briefly described with reference to FIGS. 1 and 2. FIG.

[0012] 1 is a diagram schematically illustrating distance measurement using a direct ToF method that can be applied to each embodiment. A distance measuring device 300 includes a light source unit 301 and a light receiving unit 302. The light source unit 301 is, for example, a laser diode, and is driven to emit pulsed laser light. The light emitted from the light source unit 301 is reflected by an object to be measured 303 and received as reflected light by the light receiving unit 302. The light receiving unit 302 includes a light receiving element that converts light into an electrical signal by photoelectric conversion, and outputs a signal corresponding to the received light.

[0013] Here, the time when the light source unit 301 emits light (light emission timing, first time) is defined as time t0, and the time when the light receiving unit 302 receives the light that is emitted from the light source unit 301 and reflected by the object under test 303 (light reception timing, second time) is defined as time t1. The constant c is the speed of light (2.9979×10 8 (m / sec)), the distance D between the distance measuring device 300 and the object to be measured 303 is calculated by the following equation (1): D=(c / 2)×(t1−t0) (1)

[0014] The distance measuring device 300 repeats the above process multiple times. The light receiving unit 302 may include multiple light receiving elements, and the distance D may be calculated based on the light receiving timing at which the reflected light is received by each light receiving element. The distance measuring device 300 calculates the distance D based on the time t0 from the light emission timing to the light receiving timing at which the light is received by the light receiving unit 302. m (light receiving time t m The data (called "data") is classified into classes (bins) to generate a histogram.

[0015] The light receiving unit 302 receives light for a time t m The light received by the light receiving unit 302 is not limited to light emitted by the light source unit 301 and reflected by the object to be measured. For example, ambient light around the distance measuring device 300 (light receiving unit 302) is also received by the light receiving unit 302.

[0016] 2 is a diagram showing an example of a histogram based on the time at which the light receiving unit 302 receives light, which can be applied to each embodiment. In FIG. 2, the horizontal axis indicates bins, and the vertical axis indicates the frequency of each bin. A bin is a time period for receiving light t m are classified for each predetermined unit time d. Specifically, bin #0 ism < d, bin #1 is d≦t m < 2 × d, bin #2 is 2 × d ≦ t m <3×d, ..., bin #(N-2) is (N-2)×d≦t m <(N-1)×d. The exposure time of the light receiving unit 302 is set to time t ep In this case, t ep = N × d.

[0017] The distance measuring device 300 receives light at a time t m The number of times the frequency of acquisition is counted based on the bin to determine the frequency 310 for each bin, and a histogram is generated. Here, the light receiving unit 302 receives light other than the reflected light that is the light emitted from the light source unit 301. An example of such light other than the target reflected light is the above-mentioned ambient light. The portion indicated by range 311 in the histogram includes the ambient light component due to the ambient light. The ambient light is light that is randomly incident on the light receiving unit 302, and acts as noise in the target reflected light.

[0018] On the other hand, the reflected light of interest is light received according to a specific distance, and appears in the histogram as an active light component 312. The bin corresponding to the frequency of the peak in this active light component 312 is the bin corresponding to the distance D to the object under measurement 303. By acquiring the representative time of that bin (for example, the time at the center of the bin) as the above-mentioned time t1, the distance measuring device 300 can calculate the distance D to the object under measurement 303 according to the above-mentioned formula (1). In this way, by using multiple light reception results, it is possible to perform appropriate distance measurement despite random noise.

[0019] (1-2. Configuration applicable to the present disclosure) Next, a configuration applicable to the present disclosure will be described. FIG. 3 is a block diagram showing the configuration of an example of an electronic device using a distance measuring device according to each embodiment. In FIG. 3, an electronic device 6 includes a distance measuring device 1, a light source unit 2, a storage unit 3, a control unit 4, and an optical system 5.

[0020] The light source unit 2 corresponds to the above-described light source unit 301 and is a laser diode, which is driven to emit, for example, pulsed laser light. A VCSEL (Vertical Cavity Surface Emitting Laser) that emits laser light as a surface light source can be used as the light source unit 2. Alternatively, the light source unit 2 may be an array in which laser diodes are arranged in a line, and the laser light emitted from the laser diode array may be scanned in a direction perpendicular to the line. Furthermore, a laser diode may be used as a single light source, and the laser light emitted from the laser diode may be scanned in both horizontal and vertical directions.

[0021] The distance measuring device 1 includes a plurality of light receiving elements corresponding to the light receiving unit 302. The plurality of light receiving elements are arranged, for example, in a two-dimensional lattice pattern to form a light receiving surface. The optical system 5 guides light incident from the outside to the light receiving surface included in the distance measuring device 1.

[0022] The control unit 4 controls the overall operation of the electronic device 6. For example, the control unit 4 supplies a light emission trigger, which is a trigger for causing the light source unit 2 to emit light, to the distance measuring device 1. The distance measuring device 1 causes the light source unit 2 to emit light at a timing based on the light emission trigger, and also supplies a time t em The control unit 4 also sets a pattern for distance measurement in the distance measuring device 1 in response to an external instruction, for example.

[0023] The distance measuring device 1 receives time information (light receiving time t m ) is acquired within a predetermined time range, and the frequency of each bin is calculated to generate the above-mentioned histogram. The distance measuring device 1 further calculates the distance D to the object based on the generated histogram. Information indicating the calculated distance D is stored in the storage unit 3.

[0024] 4 is a block diagram showing in more detail the configuration of an example of a distance measuring device 1 applicable to each embodiment. In FIG. 4, the distance measuring device 1 includes a pixel array unit 100, a distance measurement processing unit 101, a pixel control unit 102, an overall control unit 103, a clock generation unit 104, an emission timing control unit 105, and an interface (I / F) 106. The pixel array unit 100, distance measurement processing unit 101, pixel control unit 102, overall control unit 103, clock generation unit 104, emission timing control unit 105, and I / F 106 can be arranged on a single semiconductor chip.

[0025] Alternatively, the distance measuring device 1 may have a configuration in which a first semiconductor chip and a second semiconductor chip are stacked together. In this case, for example, a part of the pixel array unit 100 (such as a light receiving unit) may be arranged on the first semiconductor chip, and other parts included in the distance measuring device 1 may be arranged on the second semiconductor chip.

[0026] 4, the overall control unit 103 controls the overall operation of the distance measuring device 1 in accordance with, for example, a pre-installed program. The overall control unit 103 may be a microprocessor, and the program may be stored in advance in a non-volatile memory (not shown) connected to the overall control unit 103.

[0027] The overall control unit 103 can also execute control in response to an external control signal supplied from outside. The clock generation unit 104 generates one or more clock signals used in the distance measuring device 1 based on a reference clock signal supplied from outside. The light emission timing control unit 105 generates a light emission control signal indicating the light emission timing in accordance with a light emission trigger signal supplied from outside. The light emission control signal is supplied to the light source unit 2 and also to the distance measurement processing unit 101.

[0028] 4, the light source unit 2 is shown as being separate from the distance measuring device 1, but this is not limiting. For example, the light source unit 2 may be included in the distance measuring device 1.

[0029] In the pixel array section 100, a plurality of pixels 10, 10, ... each including a light receiving element are arranged in a two-dimensional lattice pattern. In the pixel array section 100, the horizontal direction in the drawing is defined as rows, and the vertical direction is defined as columns. That is, in the pixel array section 100, the pixels 10 are arranged in a matrix pattern. For example, a SPAD (Single Photon Avalanche Diode) can be applied as a light receiving element to each pixel 10.

[0030] The operation of each pixel 10 is controlled by the pixel control unit 102 in accordance with instructions from the overall control unit 103. For example, the pixel control unit 102 can control the readout of pixel signals from each pixel 10 for each block including p pixels 10 in the row direction and q pixels 10 in the column direction (p × q). Furthermore, the pixel control unit 102 can scan each pixel 10 in the row direction and then scan it in the column direction for each block to read out pixel signals from each pixel 10. This is not a limitation, and the pixel control unit 102 can also control each pixel 10 individually. Furthermore, the pixel control unit 102 can set a predetermined region of the pixel array unit 100 as a target region and select pixels 10 included in the target region as target pixels 10 from which pixel signals are to be read out. Furthermore, the pixel control unit 102 can scan multiple rows (multiple lines) together and then further scan the target region in the column direction to read out pixel signals from each pixel 10.

[0031] In the following, scanning refers to a process of causing the light source unit 2 to emit light and continuously reading out a signal Vpls (pixel signal) corresponding to light received from the pixel 10 for each pixel 10 designated as a scanning target within one scanning area. Emission and reading can be performed multiple times in one scanning.

[0032] The pixel signals read out from each pixel 10 are supplied to a ranging processing unit 101. The ranging processing unit 101 includes a conversion unit 110, a generation unit 111, and a signal processing unit 112.

[0033] The pixel signals read out from each pixel 10 and output from the pixel array unit 100 are supplied to the conversion unit 110. Here, the pixel signals are read out asynchronously from each pixel 10 and supplied to the conversion unit 110. That is, the pixel signals are read out from the light receiving elements in accordance with the timing at which light is received in each pixel 10 and output.

[0034] The conversion unit 110 converts the pixel signals supplied from the pixel array unit 100 into digital information. That is, the pixel signals supplied from the pixel array unit 100 are output in accordance with the timing at which light is received by the light receiving element included in the pixel 10 to which the pixel signal corresponds. The conversion unit 110 converts the supplied pixel signals into time information indicating the timing.

[0035] The generation unit 111 generates a histogram based on the time information into which the pixel signals are converted by the conversion unit 110. Here, the generation unit 111 counts the time information based on the unit time d set by the setting unit 113, and generates a histogram.

[0036] The signal processing unit 112 performs predetermined arithmetic processing based on the histogram data generated by the generation unit 111, and calculates, for example, distance information. For example, the signal processing unit 112 creates a curve approximation of the histogram based on the histogram data generated by the generation unit 111. The signal processing unit 112 detects peaks in the curve obtained by approximating the histogram, and can calculate the distance D based on the detected peaks.

[0037] When performing curve approximation of a histogram, the signal processing unit 112 can perform filtering on the curve obtained by approximating the histogram. For example, the signal processing unit 112 can suppress noise components by performing low-pass filtering on the curve obtained by approximating the histogram.

[0038] The distance information obtained by the signal processing unit 112 is supplied to the interface 106. The interface 106 outputs the distance information supplied from the signal processing unit 112 to the outside as output data. As the interface 106, for example, a Mobile Industry Processor Interface (MIPI) can be applied.

[0039] In the above description, the distance information calculated by the signal processing unit 112 is output to the outside via the interface 106, but this is not limited to this example. That is, the histogram data, which is the histogram data generated by the generation unit 111, may be output to the outside from the interface 106. In this case, the distance measurement condition information set by the setting unit 113 can omit information indicating the filter coefficients. The histogram data output from the interface 106 is supplied to, for example, an external information processing device and processed as appropriate.

[0040] (2. Existing Technology) Next, existing technology will be described.

[0041] 5 is a schematic diagram illustrating a first exemplary configuration of an optical system for distance measurement using a direct ToF method according to an existing technology. In the first exemplary configuration illustrated in FIG. 5, a light source unit 2 and a light receiving unit 30 are arranged in parallel. In the light source unit 2, light emitted by a light-emitting element 20 is emitted as emitted light 220 via an optical system 21 toward, for example, a distance measurement target. Reflected light 420, for example, formed by reflecting the emitted light 220 from the distance measurement target, is directly incident on the light receiving unit 30, and is received by a light receiving element (for example, the pixel array unit 100) via an optical system 41.

[0042] In this configuration, the distance between the light source unit 2 and the light receiving unit 30, in other words, the distance between the emitted light 220 and the reflected light 420, becomes the parallax. One method for reducing this parallax is to physically bring the light source unit 2 and the light receiving unit 30 closer to each other. While the parallax can be reduced as the distance between the light emitting element 20 and the light receiving element 40 decreases, there is a limit to how close the light source unit 2 and the light receiving unit 30 can be physically brought to each other due to physical constraints such as the optical systems 21 and 41 and the substrates on which the light emitting element 20 and the light receiving element 40 are mounted.

[0043] 6 is a schematic diagram illustrating a second example configuration of an optical system for distance measurement using a direct ToF method according to an existing technology. In the configuration shown in FIG. 6, emitted light 220 from the light source unit 2 passes through a half mirror 500 at a constant transmittance and is emitted as emitted light 221 toward the target to be measured. The reflected light of the emitted light 221 from the target to be measured is reflected by the half mirror 500 at a constant reflectance and enters the light receiving unit 30 as secondary reflected light 421.

[0044] In this second method, the half mirror 500 is used to combine the emitted light 220 and the reflected light 420, making it possible to reduce the parallax to approximately 0. On the other hand, in the second method, as shown by light 501 a and 501 b in the figure, light is reflected and transmitted in unnecessary directions by the half mirror 500, which significantly reduces efficiency and may also degrade distance measurement performance due to stray light.

[0045] When the parallax is large, distance measurement performance deteriorates, especially at short distances. Figures 7A and 7B are schematic diagrams for explaining the deterioration of distance measurement performance at short distances due to parallax. The configuration shown in Figures 7A and 7B is a modified example of the configuration shown in Figure 5 in which the light source unit 2 and the light receiving unit 30 are arranged in parallel. That is, in the configuration shown in Figures 7A and 7B, the reflected light 420a, which is the light emitted from the light source unit 2 and reflected by the target 900 to be measured, is reflected by the folding mirror 50. The secondary reflected light 420b, which is reflected from the reflected light 420a, is incident on the light receiving unit 30. In this configuration, the distance between the light source unit 2 and the folding mirror 50 (e.g., the center of the folding mirror 50) corresponds to the parallax.

[0046] 7A is a schematic diagram showing an example in which the object 900 to be measured is at a long distance (e.g., several tens of meters) from the light source unit 2. FIG. 7B is a schematic diagram showing an example in which the object 900 to be measured is at a short distance (e.g., 2 to 3 meters) from the light source unit 2.

[0047] 7A and 7B, the light source unit 2, the light receiving unit 30, and the folding mirror 50 are arranged assuming that the distance to the object 900 to be measured is located at a long distance (for example, several tens of meters) from the light source unit 2.

[0048] Parallax exists even when the target 900 is at a long distance. As shown in Figure 7A, when the target 900 is at a long distance, the irradiation range of the emitted light 220 on the target 900 widens, and the light receiving range on the target 900 where the light receiving unit 30 can receive the reflected light 420a widens. Therefore, these irradiation ranges and light receiving ranges on the target 900 overlap, and the reflected light 420a from this overlapping area can be received, making the effect of parallax minimal. The light source unit 2, the light receiving unit 30, and the folding mirror 50 are configured so that the reflected light 420a reflected by the target 900 is reflected by the folding mirror and the secondary reflected light 420b is received at approximately the center of the light receiving element 40.

[0049] 7B , when the target 900 is at a short distance, the reflected light 420a is incident on the light-receiving unit 30 at an angle corresponding to the distance of the target 900, and the angle of incidence on the light-receiving unit 30 deviates from the angle assumed when the target 900 is at a long distance. As a result, the secondary reflected light 420b is irradiated at a position shifted from the center of the light-receiving element 40, which is the desired irradiation position for the secondary reflected light 420b, making it difficult to obtain sufficient distance measurement performance.

[0050] For example, assume that the position of the target 900 to be measured at a short distance is position Dt in Fig. 7A. The spread of the illumination range and the light-receiving range according to the distance is constant regardless of the distance of the target 900 from the light source unit 2. Therefore, when the target 900 to be measured is at a short distance (position Dt), the illumination range and the light-receiving range do not overlap, and the effect of parallax is greater than when the target 900 to be measured is at a long distance.

[0051] (3. Overview of Embodiments of the Present Disclosure) Next, an overview of embodiments of the present disclosure will be described.

[0052] In an embodiment according to the present disclosure, an optical element that changes the angle of light is disposed in a part of the optical path of the reflected light 420 or the emitted light 220, and when the object 900 to be measured is in a short distance, the reflected light 420 is made incident on the light receiving unit 30 via this optical element. This optical element allows the reflected light 420 from the object 900 to be measured in a short distance to be irradiated onto a desired position on the light receiving unit 30, making it possible to prevent a decrease in distance measurement performance at short distances.

[0053] On the other hand, when the object 900 to be measured is at a long distance, the reflected light 420 or the emitted light 220 passes through another part of the optical path, i.e., a part of the optical path where the optical element is not disposed. Therefore, the influence of the optical element on the distance measurement is suppressed, and the original distance measurement performance can be obtained.

[0054] That is, the optical element according to the embodiment of the present disclosure is provided on an optical path through which reflected light 420, which is emitted from the light source unit 2 and reflected by the object 900 to be measured, is received by the light receiving unit 30, and changes the optical path depending on the distance between the light source unit 2 or the light receiving unit 30 and the object 900 to be measured. By providing such an optical element in the light source unit 2 or the light receiving unit 30, it is possible to suppress the influence of parallax in short-distance distance measurement.

[0055] 4. First Embodiment Next, a first embodiment of the present disclosure will be described. The first embodiment is an example in which a portion with a different angle is provided with respect to the folding mirror 50 in the configuration described with reference to FIGS. 7A and 7B .

[0056] 8A and 8B are schematic diagrams showing an example configuration according to the first embodiment, in which Fig. 8A shows an example in which a distance measurement target 900 is located at a short distance, and Fig. 8B shows an example in which the distance measurement target 900 is located at a long distance.

[0057] 8A and 8B, similar to the above-described Figures 7A and 7B, is a modified example of the configuration in which the light source unit 2 and the light receiving unit 30 are provided in parallel as shown in Figure 5. Also, similar to the above-described Figures 7A and 7B, the configuration shown in Figures 8A and 8B has the light source unit 2, the light receiving unit 30, and the folding mirror 50 arranged on the assumption that the distance to the object 900 to be measured is located at a long distance (for example, several tens of meters) from the light source unit 2.

[0058] 8A , a short-distance mirror 51 is provided at the end of the folding mirror 50 opposite the incident side of the reflected light 420a (the upper end side of the folding mirror 50 in the figure). The short-distance mirror 51 is provided at an angle with respect to the folding mirror 50 so that the opening faces the side opposite the incident side of the reflected light 420a. The short-distance mirror 51 is configured so that the area ratio of the short-distance mirror 51 is small compared to the area ratio of the portion of the folding mirror 50 that does not overlap with the short-distance mirror 51.

[0059] Reflected light 421a, which is the emitted light 220 reflected by an assumed short-distance target 900, is incident on the light-receiving unit 30 at an angle assumed for the short distance. The short-distance mirror 51 is provided on the folding mirror 50 at an angle such that secondary reflected light 421b, which is reflected from the reflected light 421a, is irradiated onto approximately the center of the light-receiving element 40.

[0060] The approximate center of the light-receiving element 40 refers to a portion within a predetermined range from the center of the light-receiving element 40, which is a portion that can receive light incident on the light-receiving unit 30 with a certain level of efficiency or higher. If light is irradiated to a position shifted from the center of the light-receiving element 40, some of the irradiated light may not be received by the light-receiving element 40, resulting in a decrease in light-receiving efficiency.

[0061] On the other hand, reflected light 420a that is not incident on the short-distance mirror 51, i.e., that is incident on an area of ​​the folding mirror 50 that does not overlap with the short-distance mirror 51, is reflected by the folding mirror 50 and enters the light-receiving unit 30 as secondary reflected light 420b. Similar to the secondary reflected light 420b in Fig. 7B, this secondary reflected light 420b is irradiated at a position shifted from the center of the light-receiving element 40, which is the desired irradiation position for secondary reflected light 420b.

[0062] 8B , when the target 900 is at a long distance, an overlapping portion occurs between the irradiation range on the target 900 of the light 220 emitted by the light source unit 2 and the light receiving range on the target 900 that can be received by the light receiving unit 30. Therefore, if reflected light 420a reflected at the overlapping portion is incident on a portion of the folding mirror 50 that does not overlap with the short distance mirror 51, the reflected light is reflected by the folding mirror 50, and the resulting secondary reflected light 420b is irradiated onto approximately the center of the light receiving element 40. On the other hand, for example, if reflected light 422a reflected outside the light receiving range on the long distance target 900 is incident on the short distance mirror 51, the secondary reflected light 422b is irradiated onto a position shifted from the center of the light receiving element 40.

[0063] As described above, the area of ​​the short-distance mirror 51 is small compared to the area of ​​the portion of the folding mirror 50 where the short-distance mirror 51 does not overlap. For a short-distance target 900, very strong reflected light 420a is obtained compared to when the target 900 is at a long distance, so the area of ​​the short-distance mirror 51 can be small. Furthermore, because the area of ​​the short-distance mirror 51 is small, secondary reflected light 422b, which is light 422a reflected by the long-distance target 900 and reflected by the short-distance mirror 51, is weak and does not have much effect on long-distance distance measurement.

[0064] In this way, the portion of the folding mirror 50 that does not overlap with the short-distance mirror 51 constitutes a first reflecting portion that reflects, toward approximately the center of the light-receiving element 40, reflected light 420a that is reflected at an overlapping portion of the irradiation range on the target 900 of the light emitted by the light source unit 2 and the light-receiving range on the target 900 that can be received by the light-receiving unit 30. In addition, the short-distance mirror 51 constitutes a second reflecting portion that reflects, toward approximately the center of the light-receiving element 40, reflected light 422a that is reflected outside the overlapping portion on the target 900.

[0065] In other words, the second reflecting portion is angled to reflect light reflected from an object at an assumed first distance (short distance) toward approximately the center of the light receiving element 40, and the first reflecting portion is angled to reflect light reflected from an object at a second distance, which is farther away than the first distance, toward the center of the light receiving element 40.

[0066] As described above, in the first embodiment, the short-distance mirror 51 having a different reflection angle from the folding mirror 50 is provided in addition to the folding mirror 50 that reflects the light reflected from the object 900 to be measured and makes it incident on the light-receiving unit 30. This makes it possible to suppress the influence of parallax in short-distance distance measurement.

[0067] In the above description, the second reflecting section is configured by providing the short-distance mirror 51 for the folding mirror 50, but this is not limited to this example. For example, the second reflecting section may be formed by bending the end of the folding mirror 50.

[0068] (4-1. Modification of the First Embodiment) Next, a modification of the first embodiment will be described. In the modification of the first embodiment, the folding mirror 50 is deformed in the thickness direction to provide portions of the folding mirror 50 with different angles.

[0069] FIG. 9 is a schematic diagram showing an example configuration according to a modification of the first embodiment. In FIG. 9 , the folding mirror 54 has an end portion on the side where the reflected light 420a is incident, which is deformed in the thickness direction to form a short-distance reflecting portion 54a (second reflecting portion) having a different reflection angle from the main reflecting portion (first reflecting portion) of the folding mirror 54. More specifically, the short-distance reflecting portion 54a is deformed so that the thickness of the end portion of the folding mirror 54 decreases toward the end. This shape of the short-distance reflecting portion 54a can be formed, for example, by cutting out the end portion of the folding mirror 54 at an angle when viewed in cross section. The area of ​​the short-distance reflecting portion 54a is configured to be smaller than the area of ​​the main reflecting portion of the folding mirror 54.

[0070] Reflected light 425a corresponding to the emitted light 220 is incident on the short-distance reflector 54a from an assumed short-distance target 900. The folding mirror 54, the short-distance reflector 54a, and the light-receiving unit 30 are arranged so that secondary reflected light 425b, which is reflected from the reflected light 425a, is irradiated onto approximately the center of the light-receiving element 40.

[0071] The reflected light 420a that does not enter the short-distance reflecting portion 54a is reflected by the main portion of the folding mirror 54 and enters the light-receiving portion 30 as secondary reflected light 420b. Similar to the secondary reflected light 420b in Fig. 7B, this secondary reflected light 420b is irradiated at a position shifted from the center of the light-receiving element 40, which is the desired irradiation position for the secondary reflected light 420b.

[0072] Although not shown, when the target 900 is at a long distance, reflected light 420 from the target 900 is incident on the main portion of the folding mirror 54, it is reflected by the folding mirror 54, and the secondary reflected light is irradiated onto approximately the center of the light receiving element 40. On the other hand, when reflected light from the target 900 at a long distance is incident on the short distance reflecting portion 54a, the secondary reflected light is irradiated onto a position shifted from the center of the light receiving element 40.

[0073] As described above, the area of ​​the short-distance reflecting portion 54a is configured to be small relative to the area of ​​the main portion of the folding mirror 54. For a short-distance target 900, very strong reflected light 425a is obtained compared to when the target 900 is at a long distance, so the area of ​​the short-distance reflecting portion 54a can be configured to be small. Furthermore, because the area of ​​the short-distance reflecting portion 54a is configured to be small, secondary reflected light formed by reflecting light from the long-distance target 900 by the short-distance reflecting portion 54a is weak and does not have much effect on long-distance distance measurement.

[0074] In this way, by providing the short-distance reflecting portion 54a by deforming a part of the folding mirror 54 in the thickness direction, it is also possible to suppress the influence of parallax in short-distance distance measurement.

[0075] (5. Second Embodiment) Next, a second embodiment of the present disclosure will be described. The second embodiment is an example in which a folding mirror is configured by laminating a first layer having a reflectance smaller than the transmittance and a second layer that reflects light transmitted through the first layer. Furthermore, the first layer has a different reflection angle from the second layer.

[0076] 10A and 10B are schematic diagrams showing an example configuration according to the second embodiment, in which Fig. 10A shows an example in which a distance measurement target 900 is located at a short distance, and Fig. 10B shows an example in which the distance measurement target 900 is located at a long distance.

[0077] 10A and 10B are modifications of the configuration shown in FIG. 5 in which the light source unit 2 and the light receiving unit 30 are provided in parallel, similar to the configuration shown in FIG. 7A and FIG. 7B described above.

[0078] 10A , the folding mirror 52 according to the second embodiment is formed by laminating a first layer 52a and a second layer 52b. The first layer 52a is formed so that the thickness of the opposite side of the first layer 52a is greater than the thickness of the side on which reflected light 420a from the target 900 is incident. For example, the cross section of the first layer 52a may be formed as a trapezoid, with the side on which reflected light 420a is incident and the end opposite to the side being the upper and lower bases, respectively, and the surface on which reflected light 420a is reflected and the surface opposite to the side being the legs of the trapezoid.

[0079] With this configuration, the folding mirror 52 according to the second embodiment has a different angle between the surface (incident surface) of the first layer 52a and the incident surface (surface in contact with the first layer 52a) of the second layer 52b.

[0080] 10A and 10B, the light source unit 2, the light receiving unit 30, and the folding mirror 52 are arranged assuming that the distance to the object 900 to be measured is located at a long distance (for example, several tens of meters) from the light source unit 2. Furthermore, the angle of the second layer 52b of the folding mirror 52 is set assuming that the distance to the object 900 to be measured is located at a long distance.

[0081] Reflected light 420a and 423a corresponding to emitted light 220 are incident on first layer 52a from an assumed short-distance measurement target 900. Note that reflected light 420a and 423a may be the same light, but for the sake of explanation, they are shown as separate lights in the figure. The same applies to reflected light 420a and 423a' in FIG. 10B.

[0082] The reflected light 423a is partially reflected by the surface of the first layer 52a, and enters the light receiving unit 30 as secondary reflected light 423b, which is then irradiated onto approximately the center of the light receiving element 40. In other words, the angle of the surface of the first layer 52a is set to an angle at which the secondary reflected light 423b is irradiated onto approximately the center of the light receiving element 40.

[0083] On the other hand, a portion of the reflected light 420a passes through the first layer 52a and enters the second layer 52b. The reflected light 420a that enters the second layer 52b is reflected by the second layer 52b to become secondary reflected light 420b, which passes through the first layer 52a and enters the light receiving unit 30. This secondary reflected light 420b is irradiated onto a position shifted from the center of the light receiving element 40.

[0084] 10B , when the target 900 is at a long distance, part of the reflected light 420a from the target 900 passes through the first layer 52a of the folding mirror 52 and enters the second layer 52b. The reflected light 420b is reflected by the second layer 52b, and the resulting secondary reflected light 420b is irradiated onto approximately the center of the light receiving element 40. On the other hand, part of the reflected light 424a from the target 900 at a long distance is reflected by the first layer 52a of the folding mirror 52, and the resulting secondary reflected light 424b is irradiated onto a position shifted from the center of the light receiving element 40.

[0085] As described above, the first layer 52a of the folding mirror 52 is configured to have a reflectance smaller than the transmittance. For a target 900 at a short distance, a much stronger reflected light 420a is obtained compared to when the target 900 is at a long distance, so it is possible to configure the reflectance of the first layer 52a to be small. Furthermore, because the reflectance of the first layer 52a of the folding mirror 52 is configured to be small, secondary reflected light 424b, which is formed by reflecting light 424a from the target 900 at a long distance and then being reflected by the first layer 52a, is weak and does not have much effect on long-distance distance measurement.

[0086] In this way, in the folding mirror 52, the first layer 52a, which has a reflectance smaller than the transmittance and whose thickness increases from the end on the incident side of the reflected light to the opposite end, is stacked on the second layer 52b, which reflects the incident light, thereby making it possible to suppress the effect of parallax in short-distance distance measurement.

[0087] (5-1. Modification of the Second Embodiment) Next, a modification of the second embodiment will be described. In the second embodiment described above, the first layer 52a in the folding mirror 52 has a trapezoidal cross section and an angle with respect to the incident light different from that of the second layer 52b, but this is not limited to this example. In the modification of the second embodiment, the first layer 52a is a flat plate, and the incident surface and the surface opposite thereto are parallel to each other.

[0088] Even if the first layer 52a is a flat plate, by appropriately setting the thickness of the first layer 52a, it is possible to irradiate the secondary reflected light 420b related to the reflected light 420a from the close-range target 900 and the secondary reflected light 424b related to the reflected light 424a from the long-range target 900 at different positions on the light receiving element 40.

[0089] In this way, in the folding mirror 52, the first layer 52a, which has a reflectance smaller than the transmittance and is flat, is stacked on the second layer 52b, which reflects the incident light, so that the effect of parallax in short-distance distance measurement can be suppressed.

[0090] 6. Third Embodiment Next, a third embodiment of the present disclosure will be described. The third embodiment is an example in which an angle changing element whose exit angle differs from the incident angle is provided on an optical path along which reflected light 420 from a distance measurement target 900 is received by a light receiving unit 30.

[0091] Fig. 11 is a schematic diagram showing an example configuration according to the third embodiment. Fig. 11 shows an example in which the object 900 to be measured is located at a short distance. The configuration shown in Fig. 11 applies the configuration shown in Fig. 5 in which the light source unit 2 and the light receiving unit 30 are provided in parallel. Note that in the configuration shown in Fig. 11, the light source unit 2 and the light receiving unit 30 are arranged assuming that the object 900 to be measured is located at a long distance from the light source unit 2.

[0092] 11 , an angle changing element 53 is provided on the optical path of reflected light 424a from a short-distance target 900. The angle changing element 53 is provided so as to overlap a part of the opening in the light receiving unit 30 through which light is incident. For example, the angle changing element 53 is provided so that the proportion of the area of ​​the part of the opening that is covered by the angle changing element 53 is smaller than the proportion of the area of ​​the part that is not covered by the angle changing element 53. As a specific example, the angle changing element 53 is provided so as to overlap about 1 / 10 of the area of ​​the opening.

[0093] The angle changing element 53 may be, for example, a prism whose incident surface and exit surface are non-parallel, and the inclination of the incident side may be set to an angle at which reflected light 424a from an expected distance when the target 900 to be measured is close is perpendicularly incident. The angle of the reflected light 424a incident on the incident surface of the angle changing element 53 is changed by the angle changing element 53, and the reflected light 424c is output as angle-changed reflected light 424c. The angle changing element 53 is configured so that the angle-changed reflected light 424c is irradiated onto the center of the light receiving element 40.

[0094] On the other hand, reflected light 420 incident on the light receiving unit 30 from the short-distance measurement target 900 without passing through the angle changing element 53 is irradiated onto a position shifted from the center of the light receiving element 40 .

[0095] Although not shown in the figure, when the target 900 to be measured is at a long distance, the reflected light 420 from the target 900 is incident directly on the opening of the light receiving unit 30 without passing through the angle changing element 53. Therefore, the reflected light 420 is irradiated onto approximately the center of the light receiving element 40.

[0096] In this way, by providing an angle-changing element 53 that changes the exit angle relative to the incident angle on the optical path where reflected light from the object 900 to be measured is received by the light receiving unit 30, it is possible to suppress the effect of parallax in short-distance distance measurement.

[0097] (7. Fourth Embodiment) Next, a fourth embodiment of the present disclosure will be described. In the first to third embodiments described above, an optical element for changing the optical path is provided in the light receiving unit 30. In contrast, the fourth embodiment is an example in which the optical element is provided on the optical path of the emitted light 220 emitted from the light source unit 2.

[0098] 12A and 12B are schematic diagrams showing an example configuration according to the fourth embodiment, in which Fig. 12A shows an example in which the object 900 to be measured is in a short distance, and Fig. 12B shows an example in which the object 900 to be measured is in a long distance.

[0099] 7A and 7B, the configuration shown in Fig. 12A and 12B is a modified example of the configuration in which the light source unit 2 and the light receiving unit 30 are provided in parallel as shown in Fig. 5. In addition, in the configuration shown in Fig. 12A and 12B, the light source unit 2, the light receiving unit 30, and the folding mirror 55 are arranged assuming that the distance to the distance measurement target 900 is located at a long distance from the light source unit 2 and the light receiving unit 30.

[0100] 12A , a short-distance mirror 56 is provided at the end of the folding mirror 55 opposite the side facing the target 900, i.e., the end opposite the emission direction of the emitted light irradiated onto the target 900. The short-distance mirror 56 is provided at an angle relative to the folding mirror 55 such that the opening faces away from the target 900. The area of ​​the short-distance mirror 56 is configured to be smaller than the area of ​​the portion of the folding mirror 55 that does not overlap with the short-distance mirror 56.

[0101] 12A , when the emitted light 231a emitted from the light source unit 2 is reflected by the short-distance mirror 56, the reflected emitted light 231b of the emitted light 231a is irradiated onto the assumed short-distance measurement target 900. The reflected light 426 of the emitted light 231b reflected by the distance measurement target 900 is incident on the light receiving unit 30 and is irradiated onto the light receiving element 40 via the optical system 41.

[0102] On the other hand, when the emitted light 230a emitted from the light source unit 2 is irradiated onto a portion of the folding mirror 55 that does not overlap with the short-distance mirror 56, the emitted light 230a is reflected by the folding mirror 55, and the resulting emitted light 230b is irradiated onto a position on the target 900 where the target 900 is assumed to be at a long distance. The reflected light (not shown) of the emitted light 230b by the target 900 is incident on the light-receiving unit 30 and irradiated onto a position shifted from the center of the light-receiving element 40.

[0103] 12B , when the object 900 to be measured is at a long distance, if the emitted light 230a emitted from the light source unit 2 is irradiated onto a portion of the folding mirror 55 that does not overlap with the short distance mirror 56, the emitted light 230a is reflected by the folding mirror 55 to produce emitted light 230b, which is irradiated onto the object 900 to be measured within the light receiving range of the light receiving unit 30. The reflected light 426, which is the emitted light 230b reflected within the light receiving range of the object 900 to be measured, is incident on the light receiving unit 30 and is irradiated onto approximately the center of the light receiving element 40.

[0104] On the other hand, when the emitted light 231a emitted from the light source unit 2 is reflected by the short-distance mirror 56, the reflected light 231b of the emitted light 231a is irradiated outside the light-receiving range of the target 900. In this case, the reflected light (not shown) of the emitted light 231b reflected by the target 900 is not received by the light-receiving unit 30, for example. Furthermore, even when the emitted light 231a is reflected by the short-distance mirror 56 and irradiated within the light-receiving range of the target 900, the area of ​​the short-distance mirror 56 is small, so that the reflected light from the target 900 is weak and does not have much effect on long-distance measurement.

[0105] As shown in the third embodiment, even if an optical element for changing the optical path is provided on the optical path of the emitted light 220 emitted from the light source unit 2, it is possible to suppress the effect of parallax in short-distance distance measurement.

[0106] In the above description, the fourth embodiment has been described as an example in which a short-distance mirror 56 is provided for the folding mirror 55, corresponding to the configuration described in the first embodiment, but this is not limited to this example.

[0107] That is, the fourth embodiment can also be applied to an example in which a folding mirror corresponding to the configuration described in the second embodiment is configured by stacking a first layer having a reflectance smaller than the transmittance and a second layer that reflects light transmitted through the first layer. In this case, the folding mirror in which the first layer and the second layer are stacked may be arranged in the same manner as the folding mirror 55 in FIGS. 12A and 12B .

[0108] Furthermore, the fourth embodiment can also be applied to an example in which an angle changing element is provided on the optical path, which corresponds to the configuration described in the third embodiment. In this case, the angle changing element may be provided so that a portion of it overlaps, for example, an opening for emitting the emitted light in the light source unit 2, as in the example described using Fig. 11. Furthermore, the angle changing element may be configured to change the optical path of the emitted light when the target 900 to be measured is in a short distance, and to emit the emitted light toward the target 900 to be measured without passing through the angle changing element when the target 900 is in a long distance.

[0109] 8. Fifth Embodiment Next, a fifth embodiment of the present disclosure will be described.

[0110] (8-1. Existing Technology) Prior to the description of the fifth embodiment, existing technology related to the fifth embodiment will be described.

[0111] Distance measuring devices (e.g., LiDAR) are known that measure distance by projecting laser light and detecting the light reflected from a target. In such distance measuring devices, if the target has high reflectivity, such as a traffic sign, the amount of returning light (reflected light) that reflects off the target and enters the light receiving sensor becomes very large, causing the returning light to reflect multiple times within the light receiving sensor or light receiving lens and enter unintended pixels. This phenomenon is called flare. When flare occurs, the pixels are unable to detect the returning light from the target whose distance is actually being measured. As a result, non-existent objects are output as distance measurement data as if they were present, significantly reducing the performance of the distance measuring device.

[0112] Fig. 13 is a schematic diagram illustrating the effect of flare on distance measurement. Section (a) of Fig. 13 shows an example of a distance measurement area 60. In the example of section (a), the distance measurement area 60 includes a road sign 61. The road sign 61 uses a mechanism called retroreflection, in which incident light is reflected back toward the light source. This retroreflection allows a vehicle driver, for example, to recognize the road sign 61 more brightly at night.

[0113] Section (b) of Figure 13 shows an example of a distance measurement result 62 obtained by performing distance measurement by horizontally scanning laser light using LiDAR in the distance measurement area 60 shown in section (a). In the example of section (b), flare occurs due to reflected light from the road sign 61 shown in section (a), and an area 63 that extends horizontally from the area 61' corresponding to the road sign 61 is obtained as the distance measurement area in which distance measurement was performed for the road sign 61. As such, there is a risk that distance measurement for the road sign 61 will not be performed correctly due to the flare.

[0114] (8-2. Overview of Fifth Embodiment) In a fifth embodiment of the present disclosure, a light source emits a first light emission and, after a predetermined time has elapsed since the first light emission, emits a second light emission with a light emission intensity different from that of the first light emission. In the fifth embodiment, the distance measurement based on the first light emission and the distance measurement based on the second light emission are integrated to output a distance measurement result.

[0115] Hereinafter, unless otherwise specified, the emission intensity of the second emission is assumed to be stronger than the emission intensity of the first emission, and the first emission will be referred to as "weak emission" and the second emission as "strong emission" as appropriate.

[0116] Weak light emission has the advantage that it is difficult to measure long distances due to the weak light emission intensity but is less likely to cause flare, while strong light emission has the advantage that it is possible to measure long distances but does cause flare. By applying the distance measuring device to which the fifth embodiment is applied, measuring the distance to the same target using both weak and strong light emission and selecting the reflected light to be used for distance measurement, it is possible to perform distance measurement with reduced flare without degrading distance measurement performance.

[0117] (8-3. Configuration Applicable to Fifth Embodiment) Fig. 14 is a block diagram showing the configuration of an example of a ranging system applicable to the fifth embodiment. In the example of Fig. 14, a ranging system 7 applicable to the fifth embodiment includes a ranging device 70 and a host device 77.

[0118] 14 , distance measuring device 70 includes a control unit 71, a light emitting unit 72, a scanning mechanism 73, a light receiving unit 74, a calculation unit 75, and an interface (I / F) unit 76. Of these, control unit 71 and calculation unit 75 may be configured by executing a predetermined program on a microprocessor, or may be configured by hardware circuits operating in cooperation with each other. Control unit 71 controls the overall operation of distance measuring device 70.

[0119] The control unit 71 outputs a light emission control signal to instruct the light emitting unit 72 to emit light. The control unit 71 also outputs the light emission instruction to the calculation unit 75. The light emitting unit 72 includes, for example, a light source that emits laser light, and emits and emits laser light 700 at a timing (time) according to the light emission control signal output from the control unit 71.

[0120] 15 is a block diagram showing an example of the configuration of the light-emitting unit 72 applicable to the fifth embodiment. As shown in Fig. 15, the light-emitting unit 72 includes a laser diode (LD) 720 as a light source that emits laser light 700, and an LD driver 721 that drives the LD 720 in accordance with a light-emission control signal output from the control unit 71.

[0121] The LD driver 721 generates a drive signal, for example, a rectangular wave with a predetermined duty ratio, in accordance with the light emission control signal output from the control unit 71, and outputs the drive signal to the LD 720. The LD 720 emits and emits laser light 700 in accordance with the drive signal output from the LD driver 721.

[0122] The LD driver 721 can change the emission intensity of the laser light 700 emitted by the LD 720 by changing the voltage and / or duty ratio of the rectangular wave of the drive signal. For example, the distance measuring device 70 may perform weak emission (first emission) by driving the LD 720 with a first voltage using the LD driver 721, and perform strong emission (second emission) by driving the LD 720 with a second voltage higher than the first voltage. Furthermore, for example, when driving the LD 720 with a rectangular wave, the distance measuring device 70 may perform weak emission (first emission) by driving the LD 720 with a first duty ratio (e.g., 25%), and perform strong emission (second emission) by driving the LD 720 with a second duty ratio (e.g., 50%) higher than the first duty ratio.

[0123] Laser light 700 emitted from the light-emitting unit 72 is incident on the scanning mechanism 73. The scanning mechanism 73 causes the incident laser light 700 to scan a predetermined range, for example, in the horizontal direction, and then emits the laser light 700 from the distance measuring device 70. The laser light 700 emitted from the distance measuring device 70 is reflected, for example, by an object to be measured 701, returns to the distance measuring device 70 as reflected light 702, and is received by the light-receiving unit 74 via the scanning mechanism 73. The configuration of the scanning mechanism 73 will be described later.

[0124] The light receiving section 74 receives not only reflected light 702 from the object to be measured 701 but also disturbance light 703. The disturbance light 703 may include ambient light and stray light inside the housing of the distance measuring device 70.

[0125] The light receiving unit 74 includes a light receiving element that outputs a pixel signal corresponding to the received light, and functions as an optical sensor for the received light. Fig. 16 is a block diagram showing an example of the configuration of the light receiving unit 74 applicable to the fifth embodiment. As shown in Fig. 16, the light receiving unit 74 includes a pixel array unit 740 in which pixels Pix formed by light receiving elements are arranged in a two-dimensional lattice pattern, and a pixel driving unit 741 for driving each pixel Pix included in the pixel array unit 740 under the control of the control unit 71.

[0126] The pixel array section 740 outputs a signal for each pixel Pix in accordance with the irradiated reflected light 702. The pixel drive section 741 generates and outputs a pixel signal based on the signal for each pixel Pix output from the pixel array section 740.

[0127] The pixel array section 740 may have the same configuration as the pixel array section 100 described with reference to Fig. 4. The light receiving elements included in the pixel array section 740 may be SPADs.

[0128] 17 is a schematic diagram showing an example of the basic configuration of a pixel Pix that uses a SPAD as a light-receiving element and is included in the pixel array unit 740 and that can be applied to the fifth embodiment. In FIG. 17, the pixel circuit that constitutes the pixel 10 includes a light-receiving element 1000, a transistor 1100, a comparator 1105, a switch unit 1101, and an AND circuit 1110.

[0129] The light-receiving element 1000 converts incident light into an electrical signal by photoelectric conversion and outputs the signal. In each embodiment, the light-receiving element 1000 converts incident photons into an electrical signal by photoelectric conversion and outputs a pulse corresponding to the incident photons. In the fifth embodiment, a single-photon avalanche diode is used as the light-receiving element 1000. Hereinafter, the single-photon avalanche diode will be referred to as a SPAD (Single Photon Avalanche Diode). A SPAD has the property that, when a large negative voltage that causes avalanche multiplication is applied to the cathode, electrons generated in response to the incidence of a single photon undergo avalanche multiplication, resulting in a large current flow. Utilizing this property of the SPAD, the incidence of a single photon can be detected with high sensitivity.

[0130] In FIG. 17 , the cathode of the photodetector 1000, which is a SPAD, is connected to a coupling element 1120, and the anode is connected to a voltage source of voltage (−Vbd). The voltage (−Vbd) is a large negative voltage for generating avalanche multiplication in the SPAD. The coupling element 1120 is connected to one end of a switch element 1101, which is controlled to be on (closed) or off (open) in response to a signal EN_PR. The other end of the switch element 1101 is connected to the drain of a transistor 1100, which is a P-channel metal oxide semiconductor field effect transistor (MOSFET). The source of the transistor 1100 is connected to a power supply voltage Vdd. The gate of the transistor 1100 is connected to a coupling element 1121, to which a reference voltage Vref is supplied.

[0131] The transistor 1100 is a current source that outputs a current from its drain that corresponds to the power supply voltage Vdd and the reference voltage Vref. With this configuration, a reverse bias is applied to the light receiving element 1000. When a photon is incident on the light receiving element 1000 while the switch unit 1101 is on, avalanche multiplication begins, and a current flows from the cathode to the anode of the light receiving element 1000.

[0132] A signal extracted from the connection point between the drain of the transistor 1100 (one end of the switch unit 1101) and the cathode of the light receiving element 1000 is input to the non-inverting input terminal of the comparator 1105. The comparator 1105 performs threshold determination based on the threshold voltage Vrefth input to the inverting input terminal, and inverts the signal input to the non-inverting input terminal each time the signal exceeds the threshold voltage Vrefth in the positive or negative direction, and outputs the signal as a pulsed output signal Vpls.

[0133] The signal Vpls output from the comparator 1105 is input to a first input terminal of an AND circuit 1110. A signal EN_F is input to a second input terminal of the AND circuit 1110. When the signals Vpls and EN_F are both in a high state, the AND circuit 1110 outputs the signal Vpls from the pixel Pix as a pixel signal via a terminal 1122.

[0134] In the pixel array unit 100, for example, by supplying a signal EN_PR that switches the switch unit 1101 to an off state to a pixel Pix that includes a light receiving element 1000 whose output is to be disabled, the supply of the power supply voltage Vdd to the light receiving element 1000 can be stopped and the pixel Pix can be turned off. This makes it possible to reduce power consumption in the pixel array unit 100. Furthermore, by switching the switch unit 1101 to an off state, the operation related to light reception by the light receiving unit 74 can be stopped, and by switching the switch unit 1101 to an on state, the operation related to light reception by the light receiving unit 74 can be started.

[0135] These signals EN_PR and EN_F are generated by the pixel driving unit 741 based on parameters stored in, for example, a register included in the control unit 71. The parameters may be stored in the register in advance, or may be stored in the register in accordance with an external input. The signals EN_PR and EN_F generated by the pixel driving unit 741 are supplied to the pixel array unit 100.

[0136] Note that the control by the signal EN_PR using the switch unit 1101 described above is control by analog voltage. On the other hand, the control by the signal EN_F using the AND circuit 1110 is control by logic voltage. Therefore, the control by the signal EN_F can be performed at a lower voltage than the control by the signal EN_PR, and is easier to handle.

[0137] The pixel Pix may have a two-layer structure of a first substrate and a second substrate bonded together. More specifically, the pixel Pix may have a light-receiving surface formed by arranging light-receiving elements 1000 in a two-dimensional lattice pattern on the first substrate, and a transistor 1100, a switch unit 1101, a comparator 1105, and an AND circuit 1110 on the second substrate.

[0138] 14 , the calculation unit 75 generates a histogram of the light-receiving frequency per unit time based on the pixel signals output from the light-receiving unit 74. The calculation unit 75 passes histogram data based on the generated histogram to the I / F unit 76. The control unit 71 also passes information indicating the timing (time) at which the LD 710 in the light-emitting unit 72 emitted light to the I / F unit 76. The I / F unit 76 outputs the histogram data passed from the calculation unit 75 and the information indicating the light-emission timing passed from the control unit 71 to, for example, the host device 77.

[0139] The host device 77 may be a general computer device having a CPU (Central Processing Unit), memory, etc. The host device 77 may be equipped with an application program for executing the processes described below in relation to the fifth embodiment. A description of the specific configuration of the host device 77 will be omitted.

[0140] The host device 77 calculates the distance D from the distance measuring device 70 to the object 701 to be measured based on the information indicating the light emission timing of the LD 710 and the histogram data output from the I / F unit 76 in the distance measuring device 70. The calculation method for the distance D can be the calculation method described using equation (1) and FIG. 2, so a description thereof will be omitted here.

[0141] Although the calculation process of the distance D based on the information indicating the light emission timing and the histogram data has been described as being executed by the host device 77 external to the distance measuring device 70, this is not limiting. For example, the calculation process of the distance D may be executed in the distance measuring device 70.

[0142] 18 is a schematic diagram showing an example of the configuration of the scanning mechanism 73 applicable to the fifth embodiment. As described above, the scanning mechanism 73 scans the laser light 700 emitted from the light-emitting unit 72 (LD 720) in the horizontal direction.

[0143] 18, the light source 430 corresponding to the LD 720 in Fig. 15 emits light at an emission timing and with an emission intensity according to the control of the control unit 71, thereby emitting laser light. In addition, in accordance with the control of the control unit 71 to control the emission of the light source 430, the pixel array unit 740 starts a light receiving operation according to the control of the control unit 71.

[0144] Laser light emitted from the light source 430 is collected by a collecting lens 431, reflected by a polarizing beam splitter 432, and irradiated onto a micromirror 433. For example, a MEMS (Micro Electro Mechanical Systems) can be applied to the micromirror 433, and the direction of the reflected light of the irradiated light can be changed within a predetermined angle range under external control.

[0145] A part of the laser light emitted as reflected light from the micromirror 433 is reflected by the object under measurement 434, and the reflected light is irradiated onto the micromirror 433. The reflected light from the object under measurement 434 that has been irradiated onto the micromirror 433 is reflected by the micromirror 433 and is irradiated onto the pixel array section 740 via the light receiving lens 435.

[0146] Here, laser light emitted from the light source 430 and reflected by the micromirror 433 is irradiated toward the object under test 434 as light that is narrow in the horizontal direction and long in the vertical direction, using, for example, an aperture with a slit provided in the vertical direction. Furthermore, the micromirror 433 is driven to scan the light in the horizontal direction. As a result, the laser light emitted from the light source 430 is reflected by the object under test 434, and is received in the pixel array section 740 only in an area 436 that has a predetermined width in the horizontal direction and is long in the vertical direction.

[0147] (8-4. Processing According to Fifth Embodiment) Next, processing according to the fifth embodiment will be described. FIG. 19 is a schematic diagram for explaining distance measurement according to the fifth embodiment. Note that FIG. 19 and similar figures thereafter schematically show histograms generated by the calculation unit 75, with the horizontal axis representing bins (time) and the vertical axis representing the frequency of each bin. Furthermore, in each of these figures, counting due to ambient light 703 is omitted.

[0148] In the fifth embodiment, as shown in FIG. 19, the distance measuring device 70 starts the light receiving operation (sensor operation) of the light receiving unit 74 at the same time t 10 The light emitting unit 72 emits a first weak light emission at the timing t 10 The distance measuring device 70 measures the time t 10 After a predetermined time (for example, 1000 ns) has elapsed since time t 12 The light emitting unit 72 emits a second strong light emission at this light emission timing.

[0149] The distance measuring device 70 measures the distance from the second light emission until a predetermined time (for example, 1000 ns) has elapsed, that is, from 0 ns to 2000 ns (time t 14 ) the light receiving unit 74 continues to receive light.

[0150] In addition, the specified time from when a weak light emission (first light emission) is performed to when a strong light emission (second light emission) is performed may be shorter than the distance measurement time corresponding to the second light emission and may include the distance measurement time corresponding to the first light emission.

[0151] 19, in response to a first emission, an active light component 80 is detected by the reflected light from the object to be measured (object to be measured A) in response to the first emission, and an active light component 81a is detected by the reflected light from the same object to be measured A in response to a second emission. The distance measurement system 7 detects the peak time t 11 , and / or the time t of the peak of the active light component 81a 13 Based on this, the distance D to the object A can be calculated.

[0152] More specifically, for example, the host device 77 10 to the peak time t of the active light component 80 11 Based on the time (for example, 100 ns) until the time t 12 from the peak time t of the active light component 81a 13 Based on the time (for example, 100 ns) until the object A is detected, the distance D to the object A can be calculated.

[0153] In practice, the distance measuring device 70 performs a set of distance measurements using the first light emission and distance measurements using the second light emission a predetermined number of times. The calculation unit 75 in the distance measuring device 70 generates a histogram by accumulating the results of the predetermined number of executions, and transmits the generated histogram data to the host device 77.

[0154] The first light emission occurs at time t 10 The second light emission is performed from time t 12 The period from the time t 12 The light receiving operation by the light receiving unit 74 is terminated at time t 14 The period from the second light emission to the strong light emission is called a strong light emission region, as it is a period during which distance measurement is performed using the second light emission, that is, strong light emission.

[0155] 19, the time of the weak light emission region and the time of the strong light emission region are each set to 1000 ns, but this is for the purpose of explanation and is not limited to this length. For example, the time of the weak light emission region and the strong light emission region may be set to a time corresponding to the distance measured using strong light emission.

[0156] The duration of the weak light emission region may be shorter than the duration of the strong light emission region. Fig. 20 is a schematic diagram for explaining another example of distance measurement according to the fifth embodiment. In the example of Fig. 20, the weak light emission region is at time t 10 From time t 12 ' is set to 300 ns, and the strong light emission region is at time t 12 ' to time t 14 In the weak light emission region, the object A emits light at time t 10Time t, 100 ns after 11 On the other hand, in the strong light emission region, an active light component 80 having a peak at time t 12 Similarly, 100 ns after the time t 13 An active light component 81b having a peak at ' is detected.

[0157] In distance measurement using weak light emission, it is difficult to measure long distances because the intensity of the laser light emitted from the light-emitting unit 72 is weak. Therefore, the time in the weak light emission region can be made shorter than the time in the strong light emission region, thereby shortening the overall distance measurement time.

[0158] Furthermore, the distance measuring device 70 according to the fifth embodiment can measure the distance to the same object A under test using both strong and weak light emission, thereby making it possible to obtain distance measurement results with higher accuracy.

[0159] 21 is a flowchart illustrating an example of distance measurement processing according to the fifth embodiment. In step S100, the control unit 71 in the distance measuring device 70 causes the light emitting unit 72 to emit weak light (first light emission) and starts a sensor operation (light receiving operation) by the light receiving unit 74. The light receiving unit 74 outputs a pixel signal to the calculation unit 75 in response to the timing at which light (photons) is received. The calculation unit 75 converts the pixel signal output from the light receiving unit 74 into time information indicating the timing at which light was received and stores the converted signal.

[0160] In the next step S101, the control unit 71 causes the light emitting unit 72 to emit a strong light (second light emission). The light receiving unit 74 outputs a pixel signal corresponding to the timing at which light (photons) is received to the calculation unit 75. The calculation unit 75 converts the pixel signal output from the light receiving unit 74 into time information indicating the timing at which light was received and stores the time information.

[0161] In the next step S102, after a predetermined time has elapsed since the strong light emission in step S101 (after the time of the strong light emission region has elapsed), the control unit 71 causes the light receiving unit 74 to terminate the sensor operation (light receiving operation). In the next step S103, the control unit 71 causes the calculation unit 75 to classify the time information accumulated in steps S101 and S102 into bins and integrate them into a histogram.

[0162] In the next step S104, the control unit 71 determines whether the processes of steps S100 to S103 have been executed a predetermined number of times (for example, 10 to several tens of times). If the control unit 71 determines that each process has not been executed the predetermined number of times (step S104, "No"), the control unit 71 returns the process to step S100. On the other hand, if the control unit 71 determines that each process has been executed the predetermined number of times (step S104, "Yes"), the control unit 71 proceeds to step S105.

[0163] In step S105, the calculation unit 75 removes the influence of ambient light 703 based on the histogram in which the time information has been integrated for each bin in step S103, and extracts active light components due to reflected light. The distance measuring device 70 transmits the histogram data of the active light components extracted by the calculation unit 75 to the host device 77 via the I / F unit 76.

[0164] The processing from step S106 onwards is performed by the host device 77. In step S106, the host device 77 analyzes the reflected light data transmitted from the distance measuring device 70, i.e., the histogram data based on the active light component, and selects appropriate reflected light data from the histogram data. Here, appropriate reflected light data refers to data from which the flare component has been removed from the histogram data based on the active light component.

[0165] In the next step S107, the host device 77 corrects the reflected light data selected in step S106. The host device 77 generates 3D (three-dimensional) point cloud data based on the corrected reflected light data. In the next step S108, the host device 77 outputs the point cloud data generated in step S107. The host device 77 may, for example, display an image based on the point cloud data on a display.

[0166] An example of histogram data analysis applicable to the fifth embodiment in step S106 described above will now be outlined with reference to Fig. 22 and Fig. 23. Fig. 22 and Fig. 23 are schematic diagrams for explaining saturation detection applicable to the fifth embodiment.

[0167] As shown in Figure 22, if the measurement target SU includes a highly reflective object HOB, the brightness of the image area (object area) of the highly reflective object HOB increases. When the brightness exceeds the saturation level LV, the brightness signal saturates. Furthermore, due to multiple reflections of the reference light PL scattered by the highly reflective object HOB, the brightness of the image area around the highly reflective object HOB also increases (flare). As a result, a distorted depth map DM is generated in which the contour of the highly reflective object HOB spreads outward, as shown as area 63 in section (b) of Figure 13.

[0168] In a light receiving element 1000 using an APD (Avalanche Photodiode) or SPAD, due to the influence of recharge, correlation signals (luminance data caused by a highly reflective object HOB) having a high correlation with each other are continuously generated in the time axis direction. As shown in FIG. 23, a correlation signal is included in the luminance signal acquired from the highly reflective object HOB without multiple reflections. No correlation signal is generated in the high-luminance image area around the highly reflective object HOB caused by multiple reflections. Therefore, the object area can be estimated based on the presence or absence of a correlation signal.

[0169] For example, the host device 77 may acquire pixel signals output from the light receiving unit 74 of the distance measuring device 70 and determine whether the received light data from the pixel signals includes saturated data where the brightness is saturated. If it is determined that the received light data includes saturated data, the host device 77 corrects the saturated data using unsaturated data (unsaturated correlation signal) at another time that is correlated with the saturated data in the time axis direction.

[0170] For example, the host device 77 extracts a luminance signal for each pixel Pix from the received light data. Based on the luminance signal of each pixel Pix, the host device 77 determines whether or not luminance data indicating a correlation signal is present for each pixel Pix. For example, the host device 77 determines that a correlation signal is not included when a discontinuous change in luminance over time is present in the luminance signal. The host device 77 determines that an image region formed by pixels Pix from which a correlation signal is detected is an object region.

[0171] The host device 77 analyzes the received light data and estimates the object area excluding high-brightness image areas caused by multiple reflections (multiple reflection removal). For example, the host device 77 detects the time (depth) d1 at which a signal with maximum brightness (saturation data) occurs from the brightness signal of each pixel Pix. The host device 77 also detects the time d2 at which a signal with maximum brightness occurs after time d1. The times d1 and d2 are expressed by the following equations (2) and (3), respectively.

[0172]

[0173]

[0174] The host device 77 calculates the probability R(u, v, d) that a correlation signal is included in the luminance signal using the time d1, the time d2, and the variance σR. The host device 77 estimates the object region based on the probability R(u, v, d). The probability R(u, v, d) is expressed by the following equation (4):

[0175]

[0176] The host device 77 calculates a saturation probability P(u, v, d) of the luminance signal extracted from the received light data based on a saturation waveform model of the luminance signal using the variances σpu and σpd. The host device 77 may determine the presence or absence of a flare based on the calculated saturation probability P(u, v, d).

[0177] (8-5. First Modification of Fifth Embodiment) Next, a first modification of the fifth embodiment will be described. In the fifth embodiment described above, weak light emission and strong light emission are achieved by changing the voltage and / or duty ratio of the rectangular wave of the drive signal for the LD 720. In contrast, the first modification of the fifth embodiment is an example in which weak light emission and strong light emission are achieved using separate light-emitting elements.

[0178] 24 is a block diagram showing an example of a configuration of a light-emitting unit 72′ according to a first modification of the fifth embodiment. In FIG. 24, the light-emitting unit 72′ includes an LD 720 for weakly emitting light. wk and LD driver 721 wk and LD720 for strong light emission. stg and LD driver 721 stg Includes:

[0179] In FIG. 24, LD720 wk The laser beam 700 is weakly emitted at a timing according to a light emission control signal output from the control unit 71. wk Similarly, LD720 stg The laser beam 700 is emitted by strong light emission at a timing according to a light emission control signal output from the control unit 71. stg It emits light and emits it.

[0180] For example, the light emitting unit 72′ controls the LD driver 721 in response to the light emission control signal. wk By generating a drive signal having a voltage and / or duty ratio for weak light emission, the LD 720 wk Similarly, the light emitting unit 72′ may drive the LD driver 721 to emit light in response to the light emission control signal. stg By generating a drive signal having a voltage and / or duty ratio for weak light emission, the LD 720 stg The light emission drive signal may be transmitted to the LD driver 721. wk and 721 stg The signal may be a signal common to both, or may be a signal corresponding to each.

[0181] Not limited to this, LD720 wk and 720 stgThe LDs 720 may emit weak or strong light depending on the structure of the elements themselves. wk and 720 stg may be driven by a common LD driver.

[0182] (8-6. Second Modification of Fifth Embodiment) Next, a second modification of the fifth embodiment will be described. In the fifth embodiment described above, weak light emission is performed before strong light emission. In contrast, in the second modification of the fifth embodiment, strong light emission is performed before weak light emission. Fig. 25 is a schematic diagram for explaining distance measurement according to the second modification of the fifth embodiment.

[0183] In the second modification of the fifth embodiment, as shown in FIG. 25, the distance measuring device 70 starts the light receiving operation at the same time t 20 The light emitting unit 72 emits a strong light at time t 20 After a predetermined time (for example, 1000 ns) has elapsed since time t 22 The light emitting unit 72 emits weak light at this timing.

[0184] The distance measuring device 70 measures the distance from the weak light emission until a predetermined time (for example, 1000 ns) has elapsed, that is, from 0 ns to 2000 ns (time t 24 In this example, the light receiving unit 74 continues to receive light until time t 20 ~t 22 The period is a strong light emission region, and the period is 22 ~t 24 The period is set as a weak light emission region.

[0185] 25, for a strong light emission, an active light component 82 is detected by the reflected light from the object A in response to the strong light emission, and an active light component 83 is detected by the reflected light from the same object A in response to a weak light emission. The distance measurement system 7 detects the peak time t 21 , or the time t of the peak of the active light component 83 23 Based on this, the distance D to the object A can be calculated.

[0186] However, when strong light is used, it is possible to measure distances over a longer distance than when weak light is used. Therefore, there is a possibility that reflected light from the strong light returning from a long distance may be acquired in the weak light measurement area (weak light area), which may make it difficult to distinguish between reflected light from strong light and reflected light from weak light.

[0187] 26 is a schematic diagram illustrating an example in which reflected light due to strong light emission is acquired in a weak light emission region. 20 ~t 21 The period from time t 21 '~t 24 The period of time is set as the weak light emission region. The peak of the active light component 83' of the reflected light from the object A due to the weak light emission occurs at the time of the start timing of the weak light emission region. 21 For example, at time t 1000 ns after 25 It has been detected in.

[0188] On the other hand, the peak of the active light component 82′ due to the reflected light from the object A in response to the strong light emission occurs at time t 21 In the case of strong light emission, this time t 21 There is a possibility that reflected light may be returned from a distance even farther than the distance corresponding to "1", making it extremely difficult to distinguish whether the active light component of the reflected light is due to strong or weak light emission.

[0189] Therefore, while distance measurement is possible by performing strong light emission before weak light emission, distance measurement results can be obtained with higher accuracy by performing strong light emission after weak light emission.

[0190] (8-7. Third Modification of Fifth Embodiment) Next, a third modification of the fifth embodiment will be described. In the fifth embodiment described above, weak light emission and strong light emission are performed serially, and this is repeated a predetermined number of times to perform distance measurement. In contrast, in the third modification of the fifth embodiment, weak light emission is repeated m times (m is an integer equal to or greater than 1) to perform distance measurement using weak light emission. Next, strong light emission is repeated n times (n is an integer equal to or greater than 1) to perform distance measurement using strong light emission. The distance measurement results from the m distance measurements using weak light emission and the distance measurement results from the n distance measurements using strong light emission are integrated to obtain a final distance measurement result.

[0191] 27 is a schematic diagram for explaining distance measurement according to the third modification of the fifth embodiment. In sections (a) to (c) of FIG. 27, at time t 30 ~t 32 The 1000 ns period is the weak emission region, and the time t 32 ~t 33 The period of 1000 ns is assumed to be a strong light emission region.

[0192] 27, section (a) shows an example of a histogram obtained by the first distance measurement using weak light emission. As illustrated in section (a), in the first distance measurement, weak light emission is repeated m times, and the number of photons received in response to the m weak light emissions is integrated for each bin to obtain an active light component 84 due to the light reflected from the object A under test under weak light emission. In the example of section (a), the peak of this active light component 84 occurs at time t 30 Time t 100 ns after 31 It has been detected in.

[0193] In Fig. 27, section (b) shows an example of a histogram obtained by the second distance measurement using strong light emission. Similarly, in the example of section (b), strong light emission is repeated n times in the second distance measurement, and the number of photons received in response to the n strong light emissions is integrated for each bin to obtain an active light component 85 due to the light reflected from the object A under test under strong light emission. In the example of section (b), the peak of this active light component 85 occurs at time t 32 Time t 100 ns after 34 It has been detected in.

[0194] In a third modification of the fifth embodiment, a histogram based on the first distance measurement shown in section (a) of Fig. 27 is integrated with a histogram based on the second distance measurement shown in section (b) to obtain an integrated histogram. Section (c) of Fig. 27 shows an example of an integrated histogram obtained by integrating the histogram based on the first distance measurement and the histogram based on the second distance measurement. The integrated histogram includes an active light component 84' based on m weak light emissions and an active light component 85' based on n strong light emissions.

[0195] The distance measurement system 7 detects the peak time t of these active light components 84′ in the same manner as described with reference to FIG. 31 , and / or the time t of the peak of the active light component 85′ 33 Based on this, the distance D to the object A can be calculated.

[0196] 28 is a flowchart illustrating an example of distance measurement processing according to the third modified example of the fifth embodiment. In step S200, the control unit 71 in the distance measuring device 70 causes the light emitting unit 72 to emit weak light (first light emission) and starts a sensor operation (light receiving operation) by the light receiving unit 74. The light receiving unit 74 outputs a pixel signal to the calculation unit 75 in response to the timing at which light (photons) is received. The calculation unit 75 converts the pixel signal output from the light receiving unit 74 into time information indicating the timing at which light was received and stores the converted signal.

[0197] In the next step S201, the control unit 71 determines whether m weak light emissions have been completed. If the control unit 71 determines that m weak light emissions have not been completed (step S201, "No"), the control unit 71 returns the process to step S200. At this time, if the sensor operation by the light receiving unit 74 is already being performed, the control unit 71 continues the sensor operation. On the other hand, if the control unit 71 determines that m weak light emissions have been completed (step S201, "Yes"), the control unit 71 transitions the process to step S202.

[0198] In step S202, the control unit 71 ends the sensor operation (light receiving operation) by the light receiving unit 74. In the next step S203, the control unit 71 causes the calculation unit 75 to classify the time information accumulated in step S200 into bins and add them to a histogram for weak light emission.

[0199] In the next step S204, the control unit 71 causes the light emitting unit 72 to emit strong light and starts a sensor operation (light receiving operation) by the light receiving unit 74. The light receiving unit 74 outputs a pixel signal corresponding to the timing at which the light is received to the calculation unit 75. The calculation unit 75 converts the pixel signal output from the light receiving unit 74 into time information indicating the timing at which the light is received and stores the time information.

[0200] In the next step S205, the control unit 71 determines whether or not n strong light emissions have been completed. If the control unit 71 determines that n strong light emissions have not been completed (step S205, "No"), the control unit 71 returns the process to step S204. At this time, if the sensor operation by the light receiving unit 74 is already being performed, the control unit 71 continues the sensor operation. On the other hand, if the control unit 71 determines that n strong light emissions have been completed (step S205, "Yes"), the control unit 71 proceeds to step S206.

[0201] In step S206, the control unit 71 terminates the sensor operation (light receiving operation) by the light receiving unit 74. In the next step S207, the control unit 71 causes the calculation unit 75 to classify the time information accumulated in step S204 into bins and add them to a histogram for strong light emission.

[0202] In the next step S208, the control unit 71 causes the calculation unit 75 to integrate the histogram for strong light emission and the histogram for strong light emission integrated in step S203.

[0203] In the next step S209, the calculation unit 75 removes the influence of ambient light 703 and extracts active light components due to reflected light based on the integrated histogram obtained by integrating the histogram for weak light emission and the histogram for strong light emission in step S209. The distance measuring device 70 transmits the histogram data for the active light components extracted by the calculation unit 75 to the host device 77 via the I / F unit 76.

[0204] The processing from step S210 onwards is performed by the host device 77. In step S210, the host device 77 analyzes the reflected light data transmitted from the distance measuring device 70, i.e., the integrated histogram data based on the active light component, and selects appropriate reflected light data from which the flare component has been removed from the integrated histogram data.

[0205] In the next step S211, the host device 77 corrects the reflected light data selected in step S210. The host device 77 generates 3D (three-dimensional) point cloud data based on the corrected reflected light data. In the next step S212, the host device 77 outputs the point cloud data generated in step S211. The host device 77 may, for example, display an image based on the point cloud data on a display.

[0206] According to the third modification of the fifth embodiment, it is possible to secure a longer irradiation interval of the LD 720 for each of the weak and strong emissions compared to when weak and strong emissions are executed serially. In the example of Figure 27, the irradiation interval can be secured at 2000 ns for each of the weak emission in section (a) and the strong emission in section (b), which is twice as long as when weak and strong emissions are executed serially. This makes it possible to secure a sufficient charging time for the LD 720, enabling strong emission with a stronger emission intensity.

[0207] Furthermore, according to the third modification of the fifth embodiment, the number of times weak light is emitted and the number of times strong light is emitted can be set separately. Furthermore, when weak light and strong light are emitted serially, it may be difficult to change the light emission intensity of the LD 720 in a short time to perform weak and strong light emission. In such cases, applying the third modification of the fifth embodiment makes it easy to switch between weak and strong light emission.

[0208] (8-8. Fourth Modification of Fifth Embodiment) Next, a fourth modification of the fifth embodiment will be described.

[0209] For example, in a LiDAR, depending on the internal structure, light emitted by the LD 720 may be reflected inside the housing, generating stray light that is detected directly by the light receiving unit 74.

[0210] 29 is a schematic diagram for explaining the influence of stray light inside the housing. In the example of FIG. 29, at the time t 40 (0 ns) to the time t 42 The period of 300 ns up to the timing of the strong light emission is the weak light emission region, and the period of 300 ns up to the timing of the strong light emission is the strong light emission region. 42 From time t 44 The period up to (2000 ns) is the strong light emission region.

[0211] In the example of Fig. 29, stray light inside the housing due to weak light emission at time t40 is received by the light receiving unit 74, and an active light component 90 due to the stray light is detected. This active light component 90 due to stray light is due to light reflected inside the housing, and is therefore detected in an extremely short time after emission, compared to light reflected from the object to be measured outside the housing. In the example of the figure, the peak of the active light component 90 due to stray light due to weak light emission occurs at time t 41 Similarly, the peak of the active light component 91 based on the stray light due to the strong light emission is detected at, for example, time t 42 At time t, which is about 10 ns after 43 For example, compared to the example shown in Fig. 19 in which the peak of the active light component due to reflected light from the DUT A outside the housing is detected approximately 100 ns after light emission, the peak of the active light component due to stray light is detected in an extremely short time.

[0212] As shown in Fig. 29, when two flashes are emitted, one weak and one strong, two levels of stray light are detected and output as distance measurement results. Since distance measurement based on this stray light is essentially unnecessary, the stray light results in unnecessary data and calculation processing.

[0213] In a fourth modification of the fifth embodiment, weak light is emitted at a timing before the start of the light receiving operation by the light receiving unit 74, and strong light is emitted a predetermined time after the start of the light receiving operation. By controlling the light emission timing in this way, it is possible to reduce unnecessary data and calculation processing due to stray light inside the housing.

[0214] 30 is a schematic diagram for explaining distance measurement according to the fourth modification of the fifth embodiment. In the example of FIG. 30, at time t 40 At this time t 40 is set to 0 ns. 40 Time t, a predetermined time before 50 The light is emitted at the timing t 50 (Weak light emission timing) is, for example, the active light component 90′ estimated to be detected as stray light due to weak light emission and the estimated peak time t 51 In the example of FIG. 30 , the timing at which the light receiving unit 74 starts receiving light (starts sensor operation) (time t 40 The weak light emission timing is determined so that the weak light emission timing corresponds to the timing at which the estimated active light component 90' disappears.

[0215] In this way, by timing the weak light emission before the light receiving unit 74 starts receiving light, it is possible to avoid measuring distance to stray light inside the housing due to weak light emission, and it is possible to reduce the amount of data and calculation processing due to stray light.

[0216] In this case, it may be impossible to measure short distances with weak light, but this is not a problem because distance measurement is possible with strong light.

[0217] 31 is a flowchart illustrating an example of distance measurement processing according to the fourth modified example of the fifth embodiment. In step S300, the control unit 71 in the distance measuring device 70 causes the light emitting unit 72 to emit weak light and starts a sensor operation (light receiving operation) by the light receiving unit 74. The light receiving unit 74 outputs a pixel signal to the calculation unit 75 in response to the timing at which light (photons) is received. The calculation unit 75 converts the pixel signal output from the light receiving unit 74 into time information indicating the timing at which light was received and stores the converted signal.

[0218] In the next step S301, the control unit 71 causes the light emitting unit 72 to emit strong light. The light receiving unit 74 outputs a pixel signal corresponding to the timing at which light (photons) is received to the calculation unit 75. The calculation unit 75 converts the pixel signal output from the light receiving unit 74 into time information indicating the timing at which light was received, and stores the time information.

[0219] In the next step S302, the control unit 71 causes the light emitting unit 72 to emit strong light, starting from the timing when the light receiving operation was started in step S301. The light receiving unit 74 outputs a pixel signal corresponding to the timing at which light (photons) is received to the calculation unit 75. The calculation unit 75 converts the pixel signal output from the light receiving unit 74 into time information indicating the timing at which light was received, and stores the time information.

[0220] In the next step S303, after a predetermined time has elapsed since the strong light emission in step S301 (after the time of the strong light emission region has elapsed), the control unit 71 causes the light receiving unit 74 to terminate the sensor operation (light receiving operation). In the next step S304, the control unit 71 causes the calculation unit 75 to classify the time information accumulated in steps S301 and S302 into bins and integrate them into a histogram.

[0221] In the next step S305, the control unit 71 determines whether the processes of steps S300 to S304 have been executed a predetermined number of times (for example, 10 to several tens of times). If the control unit 71 determines that each process has not been executed the predetermined number of times (step S305, "No"), the control unit 71 returns the process to step S300. On the other hand, if the control unit 71 determines that each process has been executed the predetermined number of times (step S305, "Yes"), the control unit 71 proceeds to step S306.

[0222] The processing from step S306 onwards is the same as the processing from step S105 onwards in the flowchart of Fig. 21 described above. That is, in step S306, the calculation unit 75 removes the influence of ambient light 703 based on the histogram in which the time information has been integrated for each bin in step S304, and extracts the active light component due to reflected light. The distance measuring device 70 transmits the histogram data of the active light component extracted by the calculation unit 75 to the host device 77 via the I / F unit 76.

[0223] In step S307, the host device 77 analyzes the reflected light data transmitted from the distance measuring device 70, i.e., the histogram data based on the active light component, and selects appropriate reflected light data from the histogram data. In the next step S308, the host device 77 corrects the reflected light data selected in step S307. The host device 77 generates 3D point cloud data based on the corrected reflected light data. In the next step S309, the host device 77 outputs the point cloud data generated in step S308.

[0224] 9. Sixth Embodiment Next, a sixth embodiment of the present disclosure will be described. The sixth embodiment relates to an example of application of the technology of the present disclosure to a moving body.

[0225] The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of moving body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0226] FIG. 32 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0227] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 32, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (Interface) 12053.

[0228] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0229] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0230] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0231] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0232] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0233] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, vehicle lane departure warning, etc.

[0234] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0235] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0236] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying information to vehicle occupants or the outside of the vehicle. In the example of Fig. 13, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0237] FIG. 33 is a diagram showing an example of the installation position of the imaging unit 12031.

[0238] In FIG. 33, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0239] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0240] 33 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0241] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0242] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation.

[0243] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0244] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0245] The above describes an example of a vehicle control system to which the technology according to the present disclosure can be applied. The technology according to the present disclosure can be applied to the imaging unit 12031 among the components described above. By applying the technology according to the present disclosure to the imaging unit 12031, it is possible to obtain more accurate distance measurement information in short-distance and long-distance distance measurement, thereby providing a safer driving environment for the driver.

[0246] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0247] Note that the present technology can also be configured as follows: (1) A distance measuring device comprising: a light receiving unit that outputs a pixel signal in response to received light; an optical element that changes the optical path of the incident light and outputs the light; and a distance measuring unit that measures distance based on the time when light is emitted from a light source and the time when the light is received by the light receiving unit, wherein the optical element is provided on an optical path from when light is emitted from the light source to when the light is reflected by an object and received by the light receiving unit, and changes the optical path in response to a distance between the light source or the light receiving unit and the object. (2) The distance measuring device according to (1), wherein the optical element is a folding mirror that reflects the reflected light toward the light receiving unit, and the folding mirror has a first reflecting portion and a second reflecting portion angled differently from the first reflecting portion. (3) The distance measuring device according to (2), wherein the folding mirror is configured such that the second reflecting portion is angled to reflect the reflected light reflected from an object at an assumed first distance toward the center of the light-receiving surface of the light-receiving portion, and the first reflecting portion is angled to reflect the reflected light reflected from an object at a second distance that is longer than the first distance toward the center of the light-receiving surface. (4) The distance measuring device according to (2) or (3), wherein the folding mirror is configured such that the proportion of the area of ​​the second reflecting portion is smaller than the proportion of the area of ​​the first reflecting portion. (5) The distance measuring device according to any of (2) to (4), wherein the folding mirror is configured by combining a first mirror that forms the first reflecting portion and a second mirror that forms the second reflecting portion. (6) The distance measuring device according to any of (2) to (4), wherein the folding mirror is configured such that the first reflecting portion and the second reflecting portion are formed by bending a single mirror. (7) The distance measuring device according to any one of (2) to (4), wherein the second reflecting portion of the folding mirror is formed by deforming an end of one mirror on the side where the reflected light is incident in the thickness direction of the mirror.(8) The distance measuring device according to (1), wherein the optical element is a folding mirror that reflects the reflected light toward the light receiving unit, the folding mirror having: a first layer that reflects a part of the incident light and transmits another part of the incident light; and a second layer that reflects the light transmitted through the first layer. (9) The distance measuring device according to (8), wherein the folding mirror has a reflection angle at the first layer that is different from the reflection angle at the second layer. (10) The distance measuring device according to (8) or (9), wherein the folding mirror has a thickness greater at an end of the first layer opposite to the end where the reflected light is incident than at the end. (11) The distance measuring device according to (8), wherein the folding mirror has the first layer having a constant thickness. (12) The distance measuring device according to any of (8) to (11), wherein the reflectance of the first layer is lower than the transmittance. (13) The distance measuring device according to (1), wherein the optical element is an angle-changing element having an exit angle that differs from an incident angle. (14) The distance measuring device according to (1), wherein the optical element is provided in an optical path of the output light emitted from the light source. (15) The distance measuring device according to (14), wherein the optical element is a folding mirror that reflects the output light toward an object to be measured, the folding mirror having a first reflecting portion and a second reflecting portion that has a different angle relative to the first reflecting portion. (16) The distance measuring device according to (14), wherein the optical element is a folding mirror that reflects the output light toward an object to be measured, the folding mirror having a first layer that reflects a part of the incident light and transmits another part of the incident light, and a second layer that reflects the light transmitted from the first layer. (17) The distance measuring device according to (14), wherein the optical element is an angle-changing element having an exit angle that differs from an incident angle. (18) An optical system including an optical element that changes an optical path of incident light and emits the light, the optical element being provided on an optical path from when light emitted from a light source is reflected by an object to when reflected light is received by a light receiving unit, and changing the optical path according to the distance between the light source or the light receiving unit and the object.(19) A distance measuring device comprising: a light emitting unit that emits light; a light receiving unit that outputs pixel signals in response to the received light; and a calculation unit that measures the time from the time the light is emitted by the light emitting unit to the time the light is received by the light receiving unit to obtain measurement values ​​and generate a histogram based on the measurement values, wherein the light emitting unit emits a first emission of light, and after a predetermined time has elapsed from the first emission of light, emits a second emission of light at an emission intensity different from that of the first emission of light. (20) The distance measuring device according to (19), wherein the light emitting unit emits the second emission of light at an emission intensity stronger than that of the first emission of light. (21) The distance measuring device according to (19) or (20), wherein the predetermined time is shorter than the distance measurement time in response to the second emission of light and includes the distance measurement time in response to the first emission of light. (22) The distance measuring device according to any of (19) to (21), wherein the light emitting unit emits the first light emission m times (m is an integer equal to or greater than 1) and the second light emission n times (n is an integer equal to or greater than 1), and the calculation unit integrates a histogram generated in response to the m first light emissions and a histogram generated in response to the n light emissions. (23) The distance measuring device according to any of (19) to (21), wherein the light emitting unit emits the first light emission before the light receiving unit starts a light receiving operation. (24) The distance measuring device according to any of (19) to (23), wherein the light emitting unit includes one light source that emits the light emission, and emits the first light emission and the second light emission in response to drive control of the light source. (25) The distance measuring device according to any one of (19) to (23), wherein the light emitting unit includes a first light source for performing the first light emission and a second light source for performing the second light emission.

[0248] 1, 70, 300 Distance measuring device 2, 301 Light source unit 7 Distance measuring system 20 Light emitting element 21, 41, 5 Optical system 30, 74, 302 Light receiving unit 40, 1000 Light receiving element 50, 52, 54, 55 Bending mirror 51, 56 Short distance mirror 52a First layer 52b Second layer 53 Angle changing element 54a Short distance reflecting unit 71 Control unit 72, 72' Light emitting unit 73 Scan mechanism 75 Arithmetic unit 76 I / F unit 77 Host device 80, 81a, 81b, 82, 82', 83, 83', 84, 84', 85, 85', 90, 90', 91, 312 Active light component 100, 740 Pixel array unit 220, 221, 230a, 230b, 231a, 231b Emitted light 303, 701 Measured object 420, 420a, 421a, 423a, 424a, 425a, 426, 702 Reflected light 420b, 421, 421b, 423b, 424b, 425b Secondary reflected light 703 Disturbing light 720,720 wk , 720 stg LD 721,721 wk , 721 stg LD driver 741 Pixel driving unit 900 Distance measurement target

Claims

1. A distance measuring device comprising: a light receiving unit that outputs pixel signals in response to received light; an optical element that changes the optical path of the incident light and then emits it; and a distance measuring unit that measures distance based on the time light is emitted from the light source and the time light is received by the light receiving unit, wherein the optical element is arranged on the optical path from when light is emitted from the light source to when the light is reflected by an object and received by the light receiving unit, and changes the optical path in response to the distance between the light source or the light receiving unit and the object.

2. A distance measuring device as described in claim 1, wherein the optical element is a folding mirror that reflects the reflected light toward the light receiving unit, and the folding mirror has a first reflecting unit and a second reflecting unit that is angled differently from the first reflecting unit.

3. The distance measuring device of claim 2, wherein the folding mirror is angled so that the second reflecting portion reflects the reflected light reflected from an object at an assumed first distance toward the center of the light receiving surface of the light receiving portion, and the first reflecting portion is angled so that the reflected light reflected from an object at a second distance that is farther away than the first distance toward the center of the light receiving surface.

4. The distance measuring device according to claim 2, wherein the folding mirror has an area ratio of the second reflecting portion smaller than an area ratio of the first reflecting portion.

5. A distance measuring device according to claim 2, wherein the folding mirror is configured by combining a first mirror that forms the first reflecting portion and a second mirror that forms the second reflecting portion.

6. The distance measuring device according to claim 2, wherein the folding mirror is formed by folding a single mirror to form the first reflecting portion and the second reflecting portion.

7. A distance measuring device according to claim 2, wherein the second reflecting portion of the folding mirror is formed by deforming the end of one mirror on the side where the reflected light is incident in the thickness direction of the mirror.

8. A distance measuring device as described in claim 1, wherein the optical element is a folding mirror that reflects the reflected light toward the light receiving unit, and the folding mirror has a first layer that reflects a portion of the incident light and transmits another portion of the incident light, and a second layer that reflects the light transmitted from the first layer.

9. The distance measuring device according to claim 8, wherein the folding mirror has a reflection angle at the first layer that is different from a reflection angle at the second layer.

10. The distance measuring device according to claim 8, wherein the folding mirror has a thickness greater at an end opposite to the end where the reflected light of the first layer is incident than at the end.

11. The distance measuring device according to claim 8, wherein the first layer of the folding mirror has a constant thickness.

12. The distance measuring device according to claim 8, wherein the first layer has a reflectance lower than a transmittance.

13. The distance measuring device according to claim 1, wherein the optical element is an angle-changing element whose exit angle differs from its incident angle.

14. The distance measuring device according to claim 1, wherein the optical element is provided in the optical path of the light emitted from the light source.

15. A distance measuring device as described in claim 14, wherein the optical element is a reflecting mirror that reflects the emitted light toward the object to be measured, and the reflecting mirror has a first reflecting portion and a second reflecting portion that is angled differently from the first reflecting portion.

16. A distance measuring device as described in claim 14, wherein the optical element is a folding mirror that reflects the emitted light toward the object to be measured, and the folding mirror has a first layer that reflects a portion of the incident light and transmits another portion of the incident light, and a second layer that reflects the light transmitted from the first layer.

17. The distance measuring device according to claim 14, wherein the optical element is an angle-changing element whose exit angle differs from its incident angle.

18. An optical system comprising: an optical element that changes the optical path of incident light and emits the light, wherein the optical element is arranged on the optical path from when light emitted from a light source is reflected by an object to when the reflected light is received by a light receiving unit, and changes the optical path depending on the distance between the light source or the light receiving unit and the object.

19. A distance measuring device comprising: a light emitting unit that emits light; a light receiving unit that outputs pixel signals in response to the received light; and a calculation unit that measures the time from when the light is emitted by the light emitting unit to when the light is received by the light receiving unit to obtain measurement values ​​and generate a histogram based on the measurement values, wherein the light emitting unit emits a first light emission, and after a predetermined time has passed since the first light emission, emits a second light emission with a light emission intensity different from that of the first light emission.

20. The distance measuring device according to claim 19, wherein the light emitting unit emits the second light emission at a light emission intensity stronger than that of the first light emission.

21. The distance measuring device according to claim 19, wherein the predetermined time is shorter than the distance measuring time corresponding to the second light emission and includes the distance measuring time corresponding to the first light emission.

22. The distance measuring device of claim 19, wherein the light emitting unit emits the first light emission m times (m is an integer greater than or equal to 1) and the second light emission n times (n is an integer greater than or equal to 1), and the calculation unit integrates a histogram generated in response to the m first light emissions and a histogram generated in response to the n light emissions.

23. The distance measuring device according to claim 19, wherein the light emitting unit performs the first light emission before the light receiving unit starts a light receiving operation.

24. The distance measuring device according to claim 19, wherein the light emitting unit includes one light source that emits the light, and emits the first light emission and the second light emission in response to drive control of the light source.

25. The distance measuring device according to claim 19, wherein the light emitting unit includes a first light source for performing the first light emission and a second light source for performing the second light emission.

Images