Distance measuring apparatus, distance measuring method, and program

Abstract

The present invention comprises: a plurality of light-emitting elements; a plurality of light receiving elements; and a determination means for determining, as a time of flight of the signal light for distance measurement, a time from emission of light from any of the plurality of light-emitting elements to reception of reflected light of the emitted signal light from any of the plurality of light-receiving elements. Among the plurality of light-receiving elements, a first light-receiving element receives reflected light and ambient light, the reflected light being signal light that has been emitted by a first light-emitting element among the plurality of light-emitting elements and has been reflected by the subject, each of the plurality of light-receiving elements including a plurality of sub-light-receiving elements, and a determination section obtaining a reference value from a measurement result of the time of flight measured using the detection signal of a first sub-light-receiving element, the first sub-light-receiving element being a portion of the first light-receiving element, the reference value indicating a measurement result of the ambient light that has been measured for each light-receiving element, and determining a time of flight of signal light for ranging in relation to the subject by using both: a reference value; and a measurement result of the time of flight measured using a detection signal of a second sub-light-receiving element that is included in the first light-receiving element and is different from the first sub-light-receiving element.

Description

Technical Field

[0001] This invention relates to ranging devices, ranging methods, and procedures. Background Technology

[0002] A ranging method based on the Time-of-Flight (TOF) scheme is known, which measures the distance to a subject by measuring the time of flight of light from the emitted light to the detection of the reflected light. According to the TOF scheme, the signal light, which is the reflected light originating from the light source, is received in a state mixed with external ambient light.

[0003] To address this, Patent Document 1 proposes a technique that generates a histogram during a period when the light source unit is not radiating light, calculates the average number of counts in the histogram as the interference light quantity, and determines the flight time of the signal light from the number of counts exceeding a threshold corresponding to the interference light quantity. Furthermore, Patent Document 2 proposes a technique that provides a light receiving unit for noise measurement, and uses the measurements from the light receiving unit for noise measurement to determine the flight time of the signal light. This light receiving unit for noise measurement is different from the light receiving unit for TOF measurement and only receives ambient light.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-3446

[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-134224 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] However, the technology proposed in Patent Document 1 requires setting a time during which the light source unit does not radiate light, i.e., a time during which Time of Flight (TOF) cannot be measured, which may lead to a reduction in the frame rate used for ranging. Furthermore, the technology proposed in Patent Document 2 requires arranging the optical receiving unit for noise measurement and the optical receiving unit for TOF measurement in parallel, which may increase the size of the ranging device. Therefore, it is desirable to improve the accuracy of ranging, i.e., to improve the accuracy of measuring the time of flight of the signal light, without requiring a time during which TOF cannot be measured or without arranging the optical receiving unit for noise measurement and the optical receiving unit for TOF measurement in parallel.

[0010] In view of the aforementioned problems, the present invention has been made, and the object of the present invention is to realize a technique for improving the accuracy of measuring the time of flight of signal light used for ranging.

[0011] Solutions to technical problems

[0012] To address the aforementioned problems, for example, the ranging device of the present invention includes the following structure. That is, the ranging device includes: a plurality of light-emitting elements; a plurality of light-receiving elements; and a determining component for determining the time from the emission of light by any of the plurality of light-emitting elements to the receipt of reflected light from any of the plurality of light-receiving elements by any of the plurality of light-receiving elements, as the time of flight of the signal light used for ranging, wherein, among the plurality of light-receiving elements, a first light-receiving element receives the reflected light and ambient light, the reflected light being the signal light emitted by the first light-emitting element among the plurality of light-emitting elements and reflected by the subject, and each of the plurality of light-receiving elements includes a plurality of sub-light receivers. The element, and the determining component: obtaining a reference value from the measurement result of the time of flight measured using a detection signal of a first sub-light receiving element, the first sub-light receiving element being a subset of the first light receiving elements, the reference value indicating the measurement result of the ambient light already measured for each light receiving element, and determining the time of flight of the signal light used for ranging in relation to the subject by using both: the reference value; and the measurement result of the time of flight measured using a detection signal of a second sub-light receiving element included in the first light receiving element and different from the first sub-light receiving element.

[0013] Advantages of the invention

[0014] According to the present invention, the accuracy of measuring flight time used for ranging can be improved.

[0015] Other features and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings. Note that throughout the drawings, the same reference numerals denote the same or similar components. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the specification, serve to explain the principles of the invention.

[0017] Figure 1 This is a block diagram illustrating a typical functional structure of a ranging device according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram illustrating the structure of the light source unit according to the first embodiment.

[0019] Figure 3 This is a schematic diagram illustrating an array of optical receiving elements according to the first embodiment.

[0020] Figure 4 This is a schematic diagram showing the appearance of the projected light according to the first embodiment.

[0021] Figure 5A Figure (1) is used to describe the appearance of the projected light on the subject in the first embodiment.

[0022] Figure 5B Figure (2) is used to describe the appearance of the projected light on the subject in the first embodiment.

[0023] Figure 5C Figure (3) is used to describe the appearance of the projected light on the subject in the first embodiment.

[0024] Figure 5D Figure (4) is used to describe the appearance of the projected light on the subject in the first embodiment.

[0025] Figure 6A It is a graph (1) used to describe the histogram according to the first embodiment and how to extract only the counts that exceed the threshold.

[0026] Figure 6B It is a graph (2) used to describe the histogram according to the first embodiment and how to extract only the counts that exceed the threshold.

[0027] Figure 7A This is a schematic diagram illustrating a sub-optical receiving element according to a first embodiment.

[0028] Figure 7B This is a diagram illustrating the light reception of the sub-optical receiving element according to the first embodiment.

[0029] Figure 8 This is a diagram used to describe the appearance of the received reflected light, which has been reflected by the subject, in the first embodiment.

[0030] Figure 9 This is a block diagram illustrating a typical functional structure of a ranging device according to the fourth embodiment. Detailed Implementation

[0031] (First Embodiment)

[0032] In the following description, embodiments will be illustrated with reference to the accompanying drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but the invention is not limited to requiring all of these features, and multiple features can be appropriately combined. Furthermore, in the drawings, the same reference numerals are given the same or similar structures, and redundant descriptions are omitted.

[0033] In the following description, as an example, a ranging device including a light-emitting element and a light-receiving element will be described. For example, this embodiment can be applied to devices such as LiDAR (light detection and ranging), digital cameras, smartphones, gaming devices, tablet terminals, medical devices, surveillance cameras, and mobile bodies such as automobiles and robots.

[0034] <Structure of Distance Measuring Device>

[0035] Reference Figure 1 The following describes the typical functional structure of the ranging device in this embodiment. The ranging device 1000 includes, for example, a light projection unit 110, a measurement unit 120, an image-space telecentric lens 130, an overall control unit 140, and a beam splitter 150.

[0036] The light projection unit 110 includes, for example, a light source unit 113 and a light source control unit 114. The light source unit 113 includes a light-emitting unit 111 and an optical element 112. (See later...) Figure 2 The structure of the light source unit 113 will be described below. The light-emitting unit 111 includes, for example, a light-emitting element array 210, in which a plurality of light-emitting elements 211, which will be described later, are arranged in two dimensions. The optical elements 112 in the light source unit 113 include, for example, a collimator lens array 220 and a microlens array 230, which will be described later.

[0037] For example, the light source control unit 114 can control the driving of the light-emitting elements, and drive each light-emitting element independently, or drive the light-emitting elements for specific areas. The light source control unit 114 may include a processor and a storage medium, and can control the driving of the light-emitting elements by executing a program stored in the storage medium through the processor in the light source control unit 114. Alternatively, the light source control unit 114 can control the driving of the light-emitting elements in response to instructions from the overall control unit 140.

[0038] Measurement unit 120 includes, for example, an optical receiving unit 121, a TDC (time-to-digital converter) array unit 122, a signal processing unit 123, and a measurement control unit 124. The optical receiving unit 121 includes components that will be referenced later. Figure 3 The optical receiver array 310 is described. The optical receiver array 310 includes, for example, a plurality of optical receiver elements arranged in a two-dimensional manner, and each optical receiver element includes a plurality of sub-optical receiver elements.

[0039] TDC array unit 122 measures the time-of-flight (TOF) of the signal light based on the detection signal from the sub-optical receiving element. For example, based on the TOF measurement result obtained by TDC array unit 122, signal processing unit 123 creates a histogram, calculates (obtains) the threshold used in removing noise components, and extracts the time-of-flight of the signal light. (See later...) Figures 6A to 6B and Figures 7A to 7B The histogram generation and threshold setting performed by the TDC array unit 122 and the signal processing unit 123 are described below. The measurement control unit 124 may include a processor and a storage medium, and the operation of the optical receiving unit 121, the TDC array unit 122, and the signal processing unit 123 can be controlled by executing a program stored in the storage medium through the processor in the measurement control unit 124. Furthermore, instead of the signal processing unit 123, the processing described in this embodiment can be implemented by executing a program through the processor in the measurement control unit 124.

[0040] The overall control unit 140 includes, for example, a processor such as a CPU, a memory such as RAM, and a storage medium such as ROM, and controls the overall operation of the ranging device 100 by, for example, executing a program stored in the storage medium using the processor. Furthermore, the processing of the signal processing unit 123 or the measurement control unit 124 described in this embodiment can be implemented by the overall control unit 140 using the processor to execute a program stored in the storage medium.

[0041] An overview of the operation of the ranging device 100 will be described below. First, the light-emitting elements 211 inside the light source unit 113 each emit pulsed light; as a result, the pulsed light is projected into space via the image-side telecentric lens 130. The pulsed light emitted from the different light-emitting elements 211 is projected at different angles in space. The projected light is radiated onto the subject, and a portion of the light reflected by the subject is received by the light receiving unit 121 via the image-side telecentric lens 130. The time from the emission of light by the light-emitting element 211 to the reception of light by the light receiving unit 121 is the time of flight (TOF) of the signal light. The TDC array unit 122 measures this time. Note that, generally, if a measurement is performed in a single step, it may be difficult to eliminate noise light such as ambient light and noise components attributable to dark counting, and furthermore, errors in ranging may increase, for example, due to noise in the measurement circuitry. Therefore, the ranging device 100 repeatedly measures the time from the emission of light from the light-emitting unit 111 to the reception of light from the light-receiving unit 121, generates a histogram of the measurement results in the signal processing unit 123, and performs noise removal and averaging of the measurement results. By allocating the time of flight (TOF) of the signal light obtained in the aforementioned manner to the following equation (1), the distance L to the subject can be calculated with high accuracy. Here, c is the speed of light.

[0042] [Mathematical Expression 1]

[0043]

[0044] <Structure of the light source unit>

[0045] Next, we will refer to Figure 2 The light source unit 113 in the light projection unit 110 according to this embodiment will be described.

[0046] The light-emitting element array 210 has the following structure: VCSELs (vertical-cavity surface-emitting lasers) are arranged in a two-dimensional array on a substrate as light-emitting elements 211. Note that in this embodiment, although the light-emitting elements 211 are not limited to VCSELs, elements that can be integrated in one-dimensional or two-dimensional arrays, such as edge-emitting lasers and LEDs (light-emitting diodes), can be used. When an edge-emitting laser is used as a light-emitting element in the light-emitting element array, a laser bar comprising a one-dimensional array on the substrate can be used, or a stack of laser bars comprising a layer of laser bars and thus having a two-dimensional light-emitting element array structure can be used. Furthermore, when LEDs are used as light-emitting elements, LEDs arranged in a two-dimensional array on the substrate can be used.

[0047] In this embodiment, for example, the wavelength of the light emitted by the light-emitting element can be in the near-infrared band; in this way, the influence of ambient light can be suppressed. Note that this embodiment does not limit the wavelength of light to the near-infrared band.

[0048] VCSELs can be created using, for example, semiconductor processes; for instance, in structures where the emitted wavelength is in the near-infrared band, GaAs-based semiconductor materials can be used as the main material of the VCSEL. In this case, the dielectric multilayer film forming the DBR (distributed Bragg reflector) mirror constituting the VCSEL can be composed of alternating and cyclic layers of two thin films formed of materials with different refractive indices (GaAs / AlGaAs). The wavelength of the emitted light can be changed by adjusting the combination or composition of the chemical elements in the compound semiconductor.

[0049] The VCSELs forming the VCSEL array are provided with electrodes for injecting current and holes into the active layer, and can emit arbitrary pulsed light and modulated light by controlling the injection timing. Therefore, the light source control unit 114 can, for example, independently drive each VCSEL in the VCSEL that acts as a light-emitting element, and can drive these VCSELs for each row, column or specific region in the VCSEL array.

[0050] Typically, due to diffraction at the aperture of a VCSEL, light emitted from the VCSEL, which acts as a light-emitting element 211, becomes divergent light. To address this, a collimator lens array 220, in which collimator lenses 221 are arranged in a two-dimensional array (between the light-emitting element array 210 and the microlens array 230 described later), is arranged to control the divergence angle of the divergent light or to convert the divergent light into collimated light. In this embodiment, collimator lenses 221 constituting the collimator lens array 220 are arranged one-to-one with the light-emitting elements 211. Light emitted from the VCSEL array and collimated by the collimator lens array 220 is, for example, converted into collimated light in a direction perpendicular to the VCSEL array substrate. Note that, for example, if the angle of radiation from the VCSEL is small due to the aperture diameter, a structure in which the collimator lens 221 is omitted can be used. The microlens array 230 includes, for example, a plurality of microlenses 231 arranged in a two-dimensional manner. Reference will be made later. Figure 4 To describe microlens 231.

[0051] <Typical Structure of an Optical Receiver>

[0052] Next, we will refer to Figure 3 The structure of the optical receiver array 310 according to this embodiment will be described below. The optical receiver array 310 includes, for example, a plurality of optical receiver elements 311. Furthermore, each optical receiver element 311 includes a plurality of sub-optical receiver elements 312. Each of the plurality of sub-optical receiver elements can be driven independently. Although Figure 3 The example shown depicts the case where the optical receiver element 311 is composed of 5×5 sub-optical receiver elements 312, but it can be composed of m×n sub-optical receiver elements (m and n are natural numbers).

[0053] The relationship between light projection and light reception

[0054] Next, refer to Figure 4 This describes the appearance of the projected light image after the light emitted from the light-emitting element 211 passes through the image-side telecentric lens 130.

[0055] The microlenses 231 constituting the microlens array 230 and the image-side telecentric lens 130 constitute an afocal system. In the afocal system, since the object and the image have a conjugate relationship at infinity, the collimated beam is incident on the microlens 231 and exits from the image-side telecentric lens 130. That is, the light projected from the image-side telecentric lens 130 is projected at an angle corresponding to the image height (the positional relationship between the microlens 231 and the image-side telecentric lens 130) and is also projected parallel to each other. Therefore, the light is projected such that when viewed from the image-side telecentric lens 130, the width d of the projected light is... bThe thickness (in three dimensions) is the same width (in three dimensions) at any distance from the subject (independent of the distance to the subject). Note that if the diameter of the emitted light on microlens 231 is p, the focal length of microlens 231 is f. M And the focal length of a telecentric lens like 130 is f L Then the width d of the projected light b As indicated by equation (2). Note that when p is greater than the spacing of the microlenses 231, p is limited by the spacing of the microlenses 231. In the width d of the projected light... b When the pupil diameter is larger than that of the image-side telecentric lens 130, the width d of the projected light b Limited by the diameter of the pupil.

[0056] [Mathematical Expression 2]

[0057]

[0058] Note that, although Figure 4 The example shown exemplarily depicts a structure in which the collimator lens 221 is omitted, but in cases where the light emitted from the light-emitting element 211 is highly dispersed, the emitted light can be collimated by arranging the collimator lens 221 between the light-emitting element 211 and the microlens 231.

[0059] Next, we will refer to Figures 5A to 5D To describe what has been used as seen on the subject Figure 4 Describe the appearance of the projected light. Figures 5A to 5C Each shows the appearance of the projected light that has been projected onto the subject (object) 501 as a projected light image 502. Figures 5A to 5D The size (diameter) of the projected light image shown is d. b equal Figure 4 The width d of the projected light shown b . Figure 5A , Figure 5B and Figure 5C Presented in ascending order of the distance between the subject 501 and the image-side telecentric lens 130. Figure 5D The appearance of each light receiving element 311 (composed of multiple sub-light receiving elements 312) in the light receiving element array 310 that receives light emitted from corresponding different light receiving elements in the light-emitting element 211 is shown.

[0060] like Figures 5A to 5C As shown, when using the light source unit 113 according to this embodiment, the spacing between the projected lights increases with the increase of the distance from the image-side telecentric lens 130, but the projected light image size d bIt remains unchanged. Therefore, the interval between the projected lights that have passed through the image-side telecentric lens 130 and radiated onto the subject 501 (projected light interval) changes according to the distance to the subject 501. On the other hand, the width of each projected light in the plurality of projected lights (projected light image size d) remains unchanged. b It does not change based on the distance to the subject 501. For example... Figure 5D As shown, since the projected light from a certain light-emitting element 211 can be received only by a specific light-receiving element 311 in the light-receiving element array 310, the light-emitting element 211 can be paired one-to-one with the light-receiving element 311. Therefore, the structure of this embodiment enables sequential driving, which is used to make only a portion of the multiple light-emitting elements 211 emit light, and to drive only the light-receiving element corresponding to the light-emitting element 211 that has been induced to emit light. In this way, multiple light-receiving elements 311 can share a single TDC, and the pixel size can be reduced, which is beneficial for increasing resolution.

[0061] <Histogram generation and threshold calculation>

[0062] Next, we will refer to Figures 6A to 6B This describes the generation of the time-of-flight histogram and the calculation of the threshold. In this embodiment, based on the detection signal from the sub-optical receiving element 312, the TDC array unit 122 measures the time-of-flight (TOF) of the detection signal. Then, using the TOF as the measurement result, the signal processing unit 123 calculates the occurrence frequency of the TOF (i.e., generates a histogram). Figures 6A to 6B In the present example, the histogram generated by the signal processing unit 123 is shown as histogram 600. Note that, as will be described later, for example, the signal processing unit 123 generates histogram 601 for each optical receiving element 311 (using the signal from the sub-optical receiving element included in the optical receiving element 311).

[0063] The received light received by the sub-light receiving element 312 includes two types of light: reflected light (here referred to as signal light) generated by the reflection of the projected light from the light-emitting element 211 onto the subject, and reflected light (here referred to as ambient light) generated by the reflection of external light other than the projected light from the light-emitting element 211 onto the subject. Therefore, the histogram 600 includes the TOF occurrence frequency (here referred to as signal light count) originating from the signal light and the TOF occurrence frequency (here referred to as ambient light count) originating from the ambient light.

[0064] The signal processing unit 123 calculates the distance to the subject from the data in the histogram 600. As a method for calculating the distance to the subject from the data in the histogram 600 (here referred to as the subject distance calculation method), a method of extracting the peak value of the histogram 600 or a method of fitting the area near the peak value of the histogram 600 can be used.

[0065] Signal processing unit 123 calculates, for example, the state where only counts exceeding the threshold CntTh calculated from the ambient light count have been extracted from histogram 600. The threshold CntTh is, for example, a reference value indicating the measurement result of the ambient light (received by the light receiving element), and extracting only counts exceeding the threshold CntTh from histogram 600 is equivalent to subtracting the threshold CntTh as an offset. By extracting only counts exceeding the threshold CntTh from histogram 600, signal processing unit 123 can determine the flight time of the signal light with high accuracy and calculate the distance to the subject from the determined flight time. Here, for example, signal processing unit 123 can calculate (obtain) the threshold CntTh using, for example, the average ECAve and standard deviation ECStd of the ambient light count according to equation (3).

[0066] CntTh=ECAve+n×ECStd(n≥0)…(3)

[0067] Note that although the threshold CntTh is calculated according to equation (3) in the description of this embodiment, the signal processing unit 123 may refer to a predefined table to obtain a value corresponding to the average value and standard deviation of the ambient light count as the threshold CntTh.

[0068] Figure 6B This shows that only the signal processing unit 123 extracts... Figure 6A An example of the result achieved by counting the number of counts exceeding the threshold CntTh in histogram 600 is shown (histogram 601). Clearly, the influence of ambient light counts has been largely eliminated in histogram 601. In this way, when calculating the distance to the subject using the aforementioned subject distance calculation method, the distance to the subject can be calculated with high accuracy by using the counts in histogram 601 instead of histogram 600.

[0069] <Measurement of Ambient Light>

[0070] The mean ECAve and standard deviation ECStd of the aforementioned ambient light counts depend on the reflectivity and reflectivity of the subject. For example, when a threshold CntTh has been calculated from reflected light relative to a subject with low reflectivity, this threshold CntTh is small. Therefore, when the threshold CntTh calculated relative to a subject with low reflectivity is applied to the histogram corresponding to a subject with high reflectivity, many ambient light counts exceed the threshold CntTh, and there is a possibility of false detection of subject distance and reduced accuracy in ranging. Conversely, when a threshold CntTh has been calculated from reflected light relative to a subject with high reflectivity, this threshold CntTh is large. Therefore, when this threshold CntTh is applied to the histogram corresponding to a subject with low reflectivity, many signal light counts also fail to exceed the threshold CntTh, and there is a possibility that ranging may not be possible.

[0071] Therefore, it is desirable to set the threshold CntTh to an appropriate value on a per-subject basis. Furthermore, when calculating the threshold CntTh, it is desirable to extract only the ambient light count (excluding the signal light count). In view of this, reference will be made to... Figures 7A to 7B This section describes an example of calculating the threshold CntTh (using ambient light counting) according to this embodiment.

[0072] In this embodiment, as referenced Figure 4 and Figures 5A to 5D As described above, there is a one-to-one correspondence between the light-emitting element 211 and the light-receiving element 311. Therefore, since the reflected light from a subject is only received by a specific light-receiving element 311, the threshold CntTh set on a subject-by-subject basis corresponds to the threshold CntTh set for each light-receiving element 311.

[0073] Figure 7A The appearance of the light receiving element 311 according to this embodiment is shown. The light receiving element 311 is receiving reflected light based on the projected light from the corresponding light-emitting element 211. Figure 7A In the example shown, each light receiving element 311 is composed of 5×5 sub-light receiving elements 312, and 2×2 light receiving elements 311 are arranged. In addition, the light-collecting images 711, 712, 713 and 714 are light-collecting images based on reflected light from corresponding subjects that are different from each other (which may not be different subjects depending on the distance to the subjects).

[0074] At this time, since ambient light is collected from all angles, it is uniformly collected onto the 5×5 sub-light receiving elements 312 constituting the light receiving element 311. However, signal light is only collected onto certain specific sub-light receiving elements 312 among the 5×5 sub-light receiving elements 312 constituting the light receiving element 311. For example, such as Figure 7BAs shown, the 5×5 sub-light receiving elements 312 can be divided into sub-light receiving elements that only receive ambient light (sub-light receiving element 721 for ambient light measurement) and sub-light receiving elements that receive both ambient light and signal light (sub-light receiving element 722 for signal light measurement). Note that the sub-light receiving element 721 for ambient light measurement and the sub-light receiving element 722 for signal light measurement are the same sub-light receiving element 312. In fact, for the signals output from the 5×5 sub-light receiving elements, the signal processing unit 123 applies different types of processing to the signals from the sub-light receiving element 721 for ambient light measurement and the signals from the sub-light receiving element 722 for signal light measurement; in this way, the sub-light receiving elements are classified. For example, in this embodiment, among the sub-light receiving elements 312 constituting the light receiving element 311, the sub-light receiving element arranged at a position excluding the central portion of the light receiving element 311 can be regarded as the sub-light receiving element 721 for ambient light measurement.

[0075] Therefore, by using only the measurement results from the sub-light receiving element 721 used for ambient light measurement, the signal processing unit 123 can calculate the threshold CntTh solely from the ambient light count (excluding the signal light count). Furthermore, the signal processing unit 123 can calculate the threshold CntTh for each individual light receiving element 311 by processing the signals from the sub-light receiving elements for each individual light receiving element 311. As a result, the threshold CntTh can be calculated on a subject-by-subject basis (here, the threshold CntTh is calculated for each light receiving element 311), and the flight time of the signal light corresponding to the subject can be determined with high accuracy. Then, the distance measurement to the subject can be calculated with high accuracy.

[0076] Note that the diameter of the received spot d is based on the diameter of the projected light. s1 and the diameter d of the received light spot caused by blurred focus s2 The size of the light-collecting image 711 formed on the plane 800 of the light-receiving element 311 satisfies the relationship indicated by the following formula (5). Figure 8 Figures 8a and 8b schematically illustrate the appearance of a light-collecting image formed on the plane 800 of the light-receiving element 311 after the projected light has been reflected by the subject and passed through the image-side telecentric lens 130. At this time, based on equation (4), the focal length f of the microlens can be used to determine the image. M The emitted light diameter p on the microlens, and the focal length f of the image-side telecentric lens 130°. L The diameter d of the received light spot is represented by the distance L from the subject. s1 Furthermore, based on equation (4), the diameter d of the received light spot caused by the blurred focus is represented by the conjugate point a0 of the subject, the distance a from the image-side telecentric lens 130 to the plane 801 of the light receiving element 311, and F as the F-value.s2 Furthermore, the size (d) of the light-collecting image 711 s1 +d s2 It needs to be smaller than the size S of the optical receiving element 311.

[0077] [Mathematical Expression 3]

[0078]

[0079] [Mathematical Expression 4]

[0080]

[0081] As described above, in this embodiment, a threshold CntTh indicating the measurement result of ambient light is calculated for each light receiving element, based on the measurement results of a sub-light receiving element used for ambient light measurement, which is a portion of the sub-light receiving element in a certain light receiving element 311. Furthermore, the flight time of the signal light used for distance measurement related to the subject is determined using the measurement results of the sub-light receiving element used for signal light measurement in the same light receiving element 311 and the calculated threshold. In this way, the threshold CntTh, which takes into account the reflectivity and reflection characteristics of each subject, can be calculated, and the flight time of the signal light used for distance measurement related to the subject can be determined with high accuracy. That is, false detection can be suppressed during distance measurement, and the accuracy of distance measurement can be improved.

[0082] (Second Embodiment)

[0083] In the above embodiments, the plurality of sub-optical receiving elements 312 constituting a certain optical receiving element 311 are classified into sub-optical receiving elements 721 for ambient light measurement and sub-optical receiving elements 722 for signal light measurement. In this embodiment, the signal processing unit 123 can dynamically control which of the plurality of sub-optical receiving elements 312 constituting a certain optical receiving element 311 is assigned as either sub-optical receiving element 721 for ambient light measurement or sub-optical receiving element 722 for signal light measurement. Note that in the following description of the embodiments, structures that are the same as or substantially the same as those in the first embodiment or the embodiments already described are given the same reference numerals, and their descriptions are omitted.

[0084] For example, as according to usage Figure 8 As understood from equations (4) and (5), the size of the light-collecting image formed on the plane of the light-receiving element 311 can be varied according to the distance L of the subject. Specifically, the longer the distance to the subject, the smaller the diameter of the light spot in the light-collecting image.

[0085] Therefore, the signal processing unit 123 can change which of the plurality of sub-light receiving elements 312 constituting the light receiving element 311 are set as sub-light receiving elements 721 for ambient light measurement and sub-light receiving elements 722 for signal light measurement, depending on the subject distance. In other words, the signal processing unit 123 can make the sub-light receiving element used as the sub-light receiving element 721 for ambient light measurement different according to the subject distance. For example, the signal processing unit 123 can reduce the number of sub-light receiving elements set as the sub-light receiving element 722 for signal light measurement as the subject distance of the subject image corresponding to the light receiving element 311 increases. In this way, the role of the sub-light receiving elements can be appropriately set in coordination with changes in the size of the light spot diameter of the light-gathering image.

[0086] Furthermore, the signal processing unit 123 can adjust the threshold CntTh according to the distance to the subject. For example, the signal processing unit 123 can increase the threshold CntTh as the distance to the subject decreases. That is, when the distance to the subject is small, the signal processing unit 123 can receive sufficient signal light, and therefore, even if the threshold CntTh increases, only counts exceeding the threshold CntTh can be extracted from the histogram 600. Therefore, by increasing the threshold CntTh, the time of flight can be determined with high accuracy, and ranging can be performed with high accuracy. Note that when the distance to the subject is long, the signal light decreases; therefore, when the distance to the subject is long, the signal processing unit 123 can also decrease the threshold CntTh to make it easy to extract only counts exceeding the threshold CntTh from the histogram 600.

[0087] (Third Embodiment)

[0088] The third embodiment will be described with respect to an exemplary process for ranging in situations with little ambient light (such as in the dark and indoors).

[0089] In situations with low ambient light, among the multiple sub-light receiving elements 312 constituting the light receiving element 311, the number of sub-light receiving elements 721 used for ambient light measurement can be reduced, while the number of sub-light receiving elements 722 used for signal light measurement can be increased. For example, the ranging device 100 can be configured to set a measurement mode for ranging indoors or outdoors. In this case, in response to the user setting the measurement mode, the signal processing unit 123 can reduce the number of sub-light receiving elements 721 used for ambient light measurement and increase the number of sub-light receiving elements 722 used for signal light measurement. Alternatively, instead of selecting a measurement mode for ranging indoors or outdoors, a time when ambient light is low due to sunset, etc., can be predefined and stored in the ranging device 100, and the signal processing unit 123 can change the number of sub-light receiving elements used for signal measurement and the number of sub-light receiving elements used for ambient light measurement according to this time. Note that storing the information defining the time when ambient light is low in, for example, in a ROM inside the overall control unit 140 is sufficient.

[0090] Next, the scenario of performing ranging under conditions of low ambient light and setting the role of the sub-light receiving elements will be described. First, ranging is performed under conditions of low ambient light, and the outputs of multiple sub-light receiving elements 312 are measured. Then, based on the outputs of the sub-light receiving elements 312, the sub-light receiving elements inside the light receiving element are set as either sub-light receiving element 721 for ambient light measurement or sub-light receiving element 722 for signal light measurement.

[0091] When ranging is performed in low ambient light conditions, the sub-optical receiver element that receives the signal light outputs a high signal light count, while the sub-optical receiver element that receives the ambient light outputs a low ambient light count. Therefore, when the optical receiver element 311 receives the signal light and the ambient light has a predetermined intensity or less, the sub-optical receiver element 721 that measures counts less than a predetermined value can be configured as the sub-optical receiver element 721 for ambient light measurement. In this way, the roles of the sub-optical receiver elements can be appropriately set, and thus the time of flight can be determined with high accuracy, and ranging can be performed with high accuracy.

[0092] (Fourth Embodiment)

[0093] In the fourth embodiment, as Figure 9As shown, the ranging device 100 includes a light metering unit 900. The light metering unit 900 includes a light metering component 901 and a light metering control unit 902. The light metering component 901 is equipped with a light metering sensor for measuring the light intensity from outside the ranging device 100, and the light metering control unit 902 controls the light metering component 901. The signal processing unit 123 can change the sub-light receiving element used for ambient light measurement 721 and the sub-light receiving element used for signal light measurement 722 based on the light intensity measured by the light metering component 901. For example, if the light intensity measured by the light metering unit 900 is dimmer than a predefined threshold, the signal processing unit 123 can reduce the number of sub-light receiving elements 721 used for ambient light measurement and increase the number of sub-light receiving elements 722 used for signal light measurement. In this way, the roles of the sub-light receiving elements can be appropriately set, and therefore the time of flight can be determined with high accuracy, and ranging can be performed with high accuracy.

[0094] (Other embodiments)

[0095] The present invention can also be implemented in a process in which a program implementing one or more functions of the above embodiments is supplied to a system or device via a network or storage medium, and one or more processors in the computer of the system or device read and execute the program. Furthermore, the present invention can also be implemented by a circuit (e.g., an ASIC) implementing one or more functions.

[0096] (Disclosure of this specification)

[0097] The disclosure in this specification includes the following ranging equipment, ranging methods, and procedures.

[0098] (Project 1)

[0099] A ranging device, characterized in that it comprises:

[0100] Multiple light-emitting elements;

[0101] Multiple optical receiving elements; and

[0102] A determining component is used to determine the time from the emission of light from any of the plurality of light-emitting elements to the receipt of reflected light from any of the plurality of light-receiving elements as the time of flight of the signal light used for ranging.

[0103] Among the plurality of light-receiving elements, the first light-receiving element receives the reflected light and ambient light. The reflected light is signal light that has been emitted by the first light-emitting element among the plurality of light-emitting elements and reflected by the subject.

[0104] Each of the plurality of optical receiving elements includes a plurality of sub-optical receiving elements, and

[0105] The determined component:

[0106] A reference value is obtained from the measurement results of the time of flight measured using the detection signal of a first sub-optical receiving element, which is a subset of the first optical receiving elements. This reference value indicates the measurement results of the ambient light already measured for each optical receiving element.

[0107] The time of flight of the signal light used for ranging in relation to the subject is determined by using the following two methods: the reference value; and the measurement result of the time of flight measured using the detection signal of a second sub-light receiving element included in the first light receiving element and different from the first sub-light receiving element.

[0108] (Project 2)

[0109] The ranging device according to Project 1 is characterized in that,

[0110] The first sub-light receiving element is a sub-light receiving element that receives ambient light but not the reflected light, and the second sub-light receiving element is a sub-light receiving element that receives both the reflected light and the ambient light.

[0111] (Project 3)

[0112] The ranging device according to item 1 or 2 is characterized in that,

[0113] The determining component determines the flight time of the signal light from flight times measured at frequencies exceeding the reference value by using a reference value for the frequency of occurrence of the flight time measured for the detection signal using the second sub-light receiving element.

[0114] (Project 4)

[0115] The ranging device according to any one of items 1 to 3 is characterized in that,

[0116] The determining component uses the reference value of each of the optical receiving elements in the optical receiving elements to determine the flight time of the signal light for each of the optical receiving elements in the optical receiving elements.

[0117] (Project 5)

[0118] The ranging device according to any one of items 1 to 4 is characterized in that,

[0119] Each of the plurality of light-emitting elements corresponds to a different light-receiving element among the plurality of light-receiving elements.

[0120] (Project 6)

[0121] The ranging device according to any one of items 1 to 5 is characterized in that it further includes:

[0122] A first lens is used to project the signal light emitted by the plurality of light-emitting elements onto the subject, and to collect the reflected light from the subject onto the plurality of light-receiving elements; and

[0123] Microlenses are arranged between the plurality of light-emitting elements and the first lens.

[0124] The first lens and the microlens constitute a focalless system.

[0125] (Project 7)

[0126] The ranging device according to Project 6 is characterized in that...

[0127] The size S of the first light-receiving element and the focal length f of the microlens M The emitted light diameter p on the microlens and the focal length f of the first lens. L The distance L from the subject, the conjugate point a0 of the subject, the distance a from the first lens to the plane of the first light receiving element, and F, as the value of F, satisfy equation (6) such that the diameter d of the received light spot s The light becomes smaller than the size S of the first light-receiving element, and the reflected light, which has been emitted by the first light-emitting element and reflected by the subject, forms the receiving light spot diameter d on the plane of the first light-receiving element via the first lens. s :

[0128] [Mathematical Expression 5]

[0129]

[0130] (Project 8)

[0131] The ranging device according to Project 1 is characterized in that,

[0132] The determining component increases the reference value as the distance to the subject decreases.

[0133] (Project 9)

[0134] The ranging device according to Project 1 is characterized in that,

[0135] The determining component causes the sub-light receiving element used as the first sub-light receiving element among the plurality of sub-light receiving elements to be different according to the distance to the subject.

[0136] (Project 10)

[0137] The ranging device according to Project 9 is characterized in that...

[0138] The determining component reduces the number of the first sub-light receiving elements among the plurality of sub-light receiving elements as the distance to the subject increases.

[0139] (Project 11)

[0140] The ranging device according to any one of items 1 to 10 is characterized in that it further comprises:

[0141] A first setting component is configured to, when the plurality of optical receiving elements receive the reflected light and ambient light having a predetermined intensity or less than a predetermined intensity, set the sub-optical receiving element as the first sub-optical receiving element if the frequency of occurrence of the time of flight measured by the detection signal of the sub-optical receiving element is lower than a predetermined frequency.

[0142] (Project 12)

[0143] The ranging device according to any one of items 1 to 11 is characterized in that,

[0144] In response to a first measurement mode already set for ranging in low ambient light environments, the determining component causes the number of the first sub-light receiving elements to differ from when the first measurement mode is not set.

[0145] (Project 13)

[0146] The ranging device according to any one of items 1 to 12 is characterized in that it further comprises:

[0147] A light sensor is used to measure the light intensity from outside the ranging device.

[0148] The determining component changes the sub-optical receiving element used as the first sub-optical receiving element and the sub-optical receiving element used as the second sub-optical receiving element among the plurality of sub-optical receiving elements according to the measured light intensity.

[0149] (Project 14)

[0150] A ranging method performed by a ranging device, the ranging device comprising multiple light-emitting elements and multiple light-receiving elements, characterized in that the ranging method includes:

[0151] The determination step is used to determine the time from when any of the plurality of light-emitting elements emits light to when any of the plurality of light-receiving elements receives the reflected light of the emitted signal light, as the flight time of the signal light used for ranging.

[0152] Among the plurality of light-receiving elements, the first light-receiving element receives the reflected light and ambient light. The reflected light is signal light that has been emitted by the first light-emitting element among the plurality of light-emitting elements and reflected by the subject.

[0153] Each of the plurality of optical receiving elements includes a plurality of sub-optical receiving elements, and

[0154] In the determination step,

[0155] A reference value is obtained from the measurement results of the time of flight measured using the detection signal of a first sub-optical receiving element, which is a subset of the first optical receiving elements. This reference value indicates the measurement results of the ambient light already measured for each optical receiving element.

[0156] The time of flight of the signal light used for ranging in relation to the subject is determined by using the following two methods: the reference value; and the measurement result of the time of flight measured using the detection signal of a second sub-light receiving element included in the first light receiving element and different from the first sub-light receiving element.

[0157] (Project 15)

[0158] A program for enabling a computer to function as a component in a ranging device according to any one of items 1 to 13.

[0159] This invention is not limited to the embodiments described above, and various changes and modifications can be made within the spirit and scope of this invention. Therefore, the appended claims are presented to inform the public of the scope of this invention.

[0160] This application claims priority to Japanese Patent Application 2023-027514, filed on February 24, 2023, the entire contents of which are incorporated herein by reference.

[0161] [List of reference numerals]

[0162] 100 range measuring device

[0163] 111 light-emitting units

[0164] 112 optical elements

[0165] 121 Optical Receiver Unit

[0166] 122 TDC array units

[0167] 123 Signal Processing Unit

Claims

1. A ranging device, characterized in that, include: Multiple light-emitting elements; Multiple optical receiving elements; as well as A determining component is used to determine the time from the emission of light from any of the plurality of light-emitting elements to the receipt of reflected light from any of the plurality of light-receiving elements as the time of flight of the signal light used for ranging. Among the plurality of light-receiving elements, the first light-receiving element receives the reflected light and ambient light. The reflected light is signal light that has been emitted by the first light-emitting element among the plurality of light-emitting elements and reflected by the subject. Each of the plurality of optical receiving elements includes a plurality of sub-optical receiving elements, and The determined component: A reference value is obtained from the measurement results of the time of flight measured using the detection signal of a first sub-optical receiving element, which is a subset of the first optical receiving elements. This reference value indicates the measurement results of the ambient light already measured for each optical receiving element. The time of flight of the signal light used for ranging in relation to the subject is determined by using the following two methods: the reference value; and the measurement result of the time of flight measured using the detection signal of a second sub-light receiving element included in the first light receiving element and different from the first sub-light receiving element.

2. The ranging device according to claim 1, characterized in that, The first sub-light receiving element is a sub-light receiving element that receives ambient light but not the reflected light, and the second sub-light receiving element is a sub-light receiving element that receives both the reflected light and the ambient light.

3. The ranging device according to claim 1, characterized in that, The determining component determines the flight time of the signal light from flight times measured at frequencies exceeding the reference value by using a reference value for the frequency of occurrence of the flight time measured for the detection signal using the second sub-light receiving element.

4. The ranging device according to claim 1, characterized in that, The determining component uses the reference value of each of the optical receiving elements in the optical receiving elements to determine the flight time of the signal light for each of the optical receiving elements in the optical receiving elements.

5. The ranging device according to claim 1, characterized in that, Each of the plurality of light-emitting elements corresponds to a different light-receiving element among the plurality of light-receiving elements.

6. The ranging device according to claim 1, characterized in that, Also includes: The first lens is used to project the signal light emitted by the plurality of light-emitting elements onto the subject and to collect the reflected light from the subject onto the plurality of light-receiving elements; as well as Microlenses are arranged between the plurality of light-emitting elements and the first lens. The first lens and the microlens constitute a focalless system.

7. The ranging device according to claim 6, characterized in that, The size S of the first light-receiving element and the focal length f of the microlens M The emitted light diameter p on the microlens and the focal length f of the first lens. L The distance L from the subject, the conjugate point a0 of the subject, the distance a from the first lens to the plane of the first light receiving element, and F, as the value of F, satisfy equation (6) such that the diameter d of the received light spot s The light becomes smaller than the size S of the first light-receiving element, and the reflected light, which has been emitted by the first light-emitting element and reflected by the subject, forms the receiving light spot diameter d on the plane of the first light-receiving element via the first lens. s : [Mathematical Expression 6] 8. The ranging device according to claim 1, characterized in that, The determining component increases the reference value as the distance to the subject decreases.

9. The ranging device according to claim 1, characterized in that, The determining component causes the sub-light receiving element used as the first sub-light receiving element among the plurality of sub-light receiving elements to be different according to the distance to the subject.

10. The ranging device according to claim 9, characterized in that, The determining component reduces the number of the first sub-light receiving elements among the plurality of sub-light receiving elements as the distance to the subject increases.

11. The ranging device according to claim 1, characterized in that, Also includes: A first setting component is configured to, when the plurality of optical receiving elements receive the reflected light and ambient light having a predetermined intensity or less than a predetermined intensity, set the sub-optical receiving element as the first sub-optical receiving element if the frequency of occurrence of the time of flight measured using the detection signal of the sub-optical receiving element is lower than a predetermined frequency.

12. The ranging device according to claim 1, characterized in that, In response to a first measurement mode already set for ranging in low ambient light environments, the determining component causes the number of the first sub-light receiving elements to differ from when the first measurement mode is not set.

13. The ranging device according to claim 1, characterized in that, Also includes: A light sensor is used to measure the light intensity from outside the ranging device. The determining component changes the sub-optical receiving element used as the first sub-optical receiving element and the sub-optical receiving element used as the second sub-optical receiving element among the plurality of sub-optical receiving elements according to the measured light intensity.

14. A ranging method performed by a ranging device, the ranging device comprising a plurality of light-emitting elements and a plurality of light-receiving elements, characterized in that, The ranging method includes: The determination step is used to determine the time from when any of the plurality of light-emitting elements emits light to when any of the plurality of light-receiving elements receives the reflected light of the emitted signal light, as the flight time of the signal light used for ranging. Among the plurality of light-receiving elements, the first light-receiving element receives the reflected light and ambient light. The reflected light is signal light that has been emitted by the first light-emitting element among the plurality of light-emitting elements and reflected by the subject. Each of the plurality of optical receiving elements includes a plurality of sub-optical receiving elements, and In the determination step, A reference value is obtained from the measurement results of the time of flight measured using the detection signal of a first sub-optical receiving element, which is a subset of the first optical receiving elements. This reference value indicates the measurement results of the ambient light already measured for each optical receiving element. The time of flight of the signal light used for ranging in relation to the subject is determined by using the following two methods: the reference value; and the measurement result of the time of flight measured using the detection signal of a second sub-light receiving element included in the first light receiving element and different from the first sub-light receiving element.

15. A program for using a computer as a component in a ranging device according to any one of claims 1 to 13.

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