Measuring device and measuring method

Abstract

[Problem] To obtain information relating to an object at a sufficient resolution or FPS using TOF. [Solution] A measuring device 1000 comprises: a light source unit 12; a splitting means 13 for splitting illuminating light from the light source unit into a plurality of light beams to be emitted toward a plurality of points on an object; a control means 31 for controlling the emission of the plurality of light beams onto the object; a detecting means 23 having a plurality of photoelectric conversion units that are arranged two-dimensionally, for detecting a plurality of reflected light beams from the plurality of points; and a processing means 51, 61 for acquiring information relating to the object for each photoelectric conversion unit on the basis of the time of flight from the emission of the plurality of light beams until the detection of the reflected light beams for each photoelectric conversion unit.

Description

Measuring device and measuring method

[0001] The present invention relates to a technique for acquiring information about an object using optical time of flight (TOF).

[0002] If it is possible to irradiate an object to be measured with light from a light source and detect the light reflected from the object, it is possible to obtain distance information to the object using TOF from irradiating the object with light to detecting the reflected light. As a distance measuring device using such TOF, Patent Document 1 discloses one that obtains two-dimensional distance information by scanning an object in two dimensions while deflecting laser light with a scanning mirror and acquiring the laser light reflected by the object.

[0003] Furthermore, a surface-emitting laser light source that can be used in a distance measuring device using TOF is a VCSEL array in which a plurality of vertical cavity surface-emitting lasers (VCSELs) are arranged two-dimensionally.

[0004] JP 2020-122689 A JP 2023-522559 A

[0005] The distance measuring device of Patent Document 1 requires time from the start to the completion of two-dimensional scanning of an object with laser light, and therefore does not provide sufficient resolution or frame rate (FPS). Although a VCSEL array can simultaneously irradiate multiple laser beams at multiple positions on an object, the irradiated positions of the laser beams on the object are also discrete according to the discrete arrangement of the VCSELs in the VCSEL array, and therefore sufficient resolution cannot be obtained.

[0006] The present invention provides a measurement apparatus and a measurement method that use TOF to obtain information about an object to be measured at sufficient resolution and FPS.

[0007] A measuring device according to one aspect of the present invention is characterized by having a light source unit, a splitting means for splitting illumination light from the light source unit into multiple lights that are irradiated toward multiple points on an object, a control means for controlling the irradiation of the multiple lights onto the object, a detection means having multiple photoelectric conversion units arranged two-dimensionally and detecting multiple reflected lights from the multiple points, and a processing means for acquiring information about the object for each photoelectric conversion unit based on the light flight time from the irradiation of the multiple lights to the detection of the reflected light for each photoelectric conversion unit.

[0008] A measurement method according to another aspect of the present invention includes splitting illumination light from a light source unit into multiple light beams that are irradiated toward multiple points on an object, controlling the irradiation of the multiple light beams onto the object, detecting multiple reflected light beams from the multiple points using multiple photoelectric conversion units arranged two-dimensionally, and acquiring information about the object for each photoelectric conversion unit based on the light flight time from the irradiation of the multiple light beams to the detection of the reflected light for each photoelectric conversion unit. Note that a program that causes a computer to execute processing according to the above measurement method also constitutes another aspect of the present invention.

[0009] According to the present invention, information about the object to be measured can be obtained with sufficient resolution and FPS using TOF.

[0010] 1 is a block diagram showing the configuration of a measurement device according to an embodiment; 2 is a diagram showing the configuration of a pixel region of a light detection unit according to an embodiment; 3 is a diagram explaining a drive pulse of a light detection unit according to an embodiment; 4 is a diagram showing the configuration of a measurement device according to an embodiment; 5 is a flowchart showing processing executed in the first embodiment; 6 is a diagram showing the configuration of a measurement device according to an embodiment; 7 is a diagram showing the configuration of a splitting unit according to an embodiment; 8 is another diagram showing the configuration of a splitting unit according to an embodiment; 9 is a flowchart showing processing executed in the second embodiment; 10 is a diagram explaining the intensity and detection time of reflected light from an object and other light; 11 is a diagram showing the configuration of a splitting unit according to embodiments 1 and 2.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] First, an overview of a measurement device according to an embodiment will be described with reference to Fig. 1. The measurement device 1000 shown in Fig. 1 includes an illumination unit 11, a light detection unit 21, a timing control unit 31, a signal processing unit 41, an arithmetic processing unit 51, a control unit 61, a display unit 71, and a storage unit 81. The timing control unit 31 and the control unit 61 constitute a control means, and the signal processing unit 41, the arithmetic processing unit 51, and the control unit 61 constitute a processing means.

[0013] The illumination unit 11 has a light source unit 12 and a splitting unit (splitting means) 13. The light source unit 12 emits illumination light to be irradiated onto an object to be measured. The object may be a person, a car, a plant, a mold, a substrate, or the like, and the type of the object is not particularly limited.

[0014] In this embodiment, the light source 12 is a laser light source, and the laser light emitted from the laser light source is collimated by a collimator lens and then emitted. The light source unit 12 may emit a composite of two or more colors of laser light, or may collimate and emit light from a light source other than a laser light source, such as an LED or a mercury lamp.

[0015] The light source unit 12 emits illumination light in response to receiving a light emission control signal transmitted from the timing control unit 31. For example, the light source unit 12 emits a light beam of a specific wavelength as pulsed light having a pulse width of several picoseconds to several tens of nanoseconds.

[0016] The illumination light emitted from the light source unit 12 is split by the splitter unit 13 into multiple light beams that have uniform intensities (light amounts) and are distributed two-dimensionally, and are irradiated onto multiple points on the object. Note that the uniform intensities do not necessarily have to be completely the same, and may have a difference that can be considered to be the same for distance measurement. For example, the intensity difference may be within 10%.

[0017] The splitting unit 13 is configured using a liquid crystal panel, a digital mirror device, a diffraction element, etc. The specific configuration of the splitting unit 13 will be described later.

[0018] The light detection unit 21 receives a plurality of beams of light that are irradiated onto a plurality of points on the object and reflected from each of the points. The light detection unit 21 includes a distance measurement optical system 22 and a sensor unit 23. The distance measurement optical system 22 irradiates a plurality of beams of light from the splitter 13 onto a plurality of points on the object and guides a plurality of beams of light reflected from the plurality of points on the object to the sensor unit 23, thereby forming an optical image of the plurality of points on the object on the sensor unit 23. The sensor unit 23 includes a plurality of pixels, each including a photoelectric conversion unit, and outputs a light reception signal (voltage pulse) from each pixel each time light is incident on the pixel. The light detection unit 21 counts the number of photons for each pixel of the sensor unit 23 based on the light reception signal and outputs the count value (intensity of received light) and information on the detection time, which is the time when the photon count was performed, to the signal processing unit 41.

[0019] The sensor unit 23 is exposed to light for a predetermined exposure time when performing one light receiving operation. The sensor unit 23 starts and ends exposure in response to receiving an exposure control signal transmitted from the timing control unit 31. During the exposure time from the start to the end of exposure, the light source unit 12 emits illumination light at the above-mentioned pulse width one or more times, and the sensor unit 23 receives reflected light.

[0020] In this embodiment, a SPAD array in which a plurality of SPAD (Single Photon Avalanche Diode) pixels are arranged in two dimensions (X direction and Y direction) as shown in Fig. 2 is used as the sensor unit 23. Details of the SPAD array will be described later. Note that, in this embodiment, the sensor unit 23 will be described using an avalanche photodiode that avalanche doubles light, but the sensor unit may also be configured using a photodiode that does not avalanche double light.

[0021] The splitting unit 13 and the sensor unit 23 are arranged at conjugate positions with respect to the distance measurement optical system 22 .

[0022] The timing control unit 31 transmits a light emission control signal to the illumination unit 11 to control the light emission timing of the illumination unit 11, and transmits an exposure control signal to the light detection unit 21 to control the timing of receiving reflected light at the light detection unit 21.

[0023] The signal processing unit 41 performs signal processing such as noise removal on the light reception signal output from the sensor unit 23. The signal processing unit 41 also maps the photon count value for each pixel and the detection time of reflected light output from the sensor unit 23 for pixels within the entire pixel region or a partial pixel region of the sensor unit 23. This provides two-dimensional light detection information (first information).

[0024] The calculation processing unit 51 is configured by a computer such as a CPU, and has an information calculation unit 52 and an image construction unit 53. In this embodiment, a time-of-flight (TOF) method is adopted, which acquires spatial information (second information) about an object, such as distance information about the object, based on the time of flight of light (TOF) from the irradiation time when illumination light is irradiated toward the object (when the light source unit 12 emits light) to the detection time when reflected light is received by the light detection unit 21. The information calculation unit 52 calculates distance information (light ray flight distance) indicating the optical path length of light received by each pixel, based on the irradiation time of illumination light acquired from the timing control unit 31 and the detection time of reflected light for each pixel of the sensor unit 23 obtained from the two-dimensional light detection information.

[0025] Image construction unit 53 constructs a shape from the distance information for each pixel as the distance measurement result calculated by information calculation unit 52, and outputs image data for displaying the shape (distance image data) to display unit 71. Display unit 71 displays the distance image data. Storage unit 81 stores the distance image data.

[0026] The control unit 61 controls the entire measuring device 1000. The control unit 61 includes a computer such as a CPU, and executes a program to control the illumination unit 11, the light detection unit 21, and the calculation processing unit 51. The control unit 61, together with the signal processing unit 41 and the calculation processing unit 51, may be configured as an integrated computer.

[0027] 2 shows the configuration of a portion of the entire pixel region in the sensor unit 23 (SPAD array). On the SPAD array, a plurality of SPAD pixels 103 are arranged in the X and Y directions. Each SPAD pixel 103 has a photoelectric conversion unit (avalanche photodiode) 201, a quenching element 202, a control unit 210, a counter / memory 211, and a readout unit 212.

[0028] A potential VH higher than the voltage VL supplied to the anode is supplied to the cathode of the photoelectric conversion unit 201. That is, a potential is supplied to the anode and cathode so that a reverse bias is applied such that photons incident on the photoelectric conversion unit 201 are avalanche multiplied. By performing photoelectric conversion with such a reverse bias potential supplied, charges generated by the incident light (photons) undergo avalanche multiplication, generating an avalanche current.

[0029] When a reverse bias potential is supplied, and the potential difference between the anode and cathode is greater than the breakdown voltage, the avalanche diode operates in Geiger mode. An avalanche diode that uses Geiger mode operation to quickly detect weak signals at the single-photon level is called a SPAD.

[0030] The control unit 210 determines whether or not to count the number of photons based on the light reception signal output from the photoelectric conversion unit 201. In this embodiment, the control unit 210 is a switch (gate circuit) provided between the photoelectric conversion unit 201 and the counter / memory 211. The gate of the switch is connected to the pulse line 124, and the control unit 210 is switched on and off in response to a signal input to the pulse line 124. A signal based on an exposure control signal from the timing control unit 31 is input to the pulse line 124 of each pixel column, thereby controlling the gates of the switches of all pixel columns. This collectively controls the start and end of light detection (exposure) of all SPAD pixels 103.

[0031] The control unit 210 may be configured with a logic circuit instead of a switch. For example, if an AND circuit is provided as the logic circuit, and the first input of the AND circuit is the output from the photoelectric conversion unit 201 and the second input is the signal on the pulse line 124, it becomes possible to switch whether or not to count the number of photons based on the light reception signal from the photoelectric conversion unit 201.

[0032] Furthermore, the control unit 210 does not need to be provided between the photoelectric conversion unit 201 and the counter / memory 211, but may be a circuit that inputs a signal that switches the counter in the counter / memory 211 between operating and non-operating.

[0033] The counter / memory 211 counts the number of photons that have entered the photoelectric conversion unit 201 and stores the count value as digital data.

[0034] The readout unit 212 is connected to the readout signal line 123 via the counter / memory 211. In response to a control pulse supplied from a vertical scanning circuit unit (not shown) provided in the SPAD array via a control line 214, the readout unit 212 switches whether or not to output the count value of the counter / memory 211 to the readout signal line 123. The readout unit 212 includes a buffer circuit and the like for outputting a signal.

[0035] The readout signal line 123 may be a signal line that outputs the count value from the light detection unit 21 to the arithmetic processing unit 51, or may be a signal line that outputs the count value to the signal processing unit 41. Furthermore, the vertical scanning circuit unit and a horizontal scanning circuit unit (not shown) may be provided on the same substrate on which the SPAD array is provided, or may be provided on a substrate different from the substrate on which the SPAD array is provided.

[0036] 3 shows the timing at which illumination light (pulsed light) from the illumination unit 11 is irradiated onto an object, and the timing at which the illumination light is reflected by the object and the reflected light is received (photodetected) by the sensor unit 23 for photocounting. At time t11, illumination light is irradiated onto the object and photodetection by the sensor unit 23 begins, and photodetection ends at time t12 after a predetermined count period. By the time the reflected light reaches the sensor unit 23, the sensor unit 23 is performing photodetection and detects the reflected light.

[0037] The light receiving timing of the plurality of SPAD pixels provided in the sensor unit 23 may be controlled collectively for all pixels or individually for each pixel.

[0038] A set of data including information on the intensity (light amount) of reflected light and information on the detection time when the reflected light is received can be obtained for each SPAD pixel arranged two-dimensionally in the sensor unit 23. By combining data from all pixels (within the XY plane), two-dimensional light detection information can be obtained, which is information on the intensity of reflected light and the detection time t for each position (X, Y) in the XY plane. Then, by using the two-dimensional light detection information, information about an object can be obtained with sufficient resolution and FPS.

[0039] 4 shows the configuration of a measurement apparatus 1000A according to Example 1. The measurement apparatus 1000A has an illumination unit 11 including a light source unit 12 consisting of a laser light source U101 and a collimator lens U201, and a splitting unit 13 consisting of a transmissive liquid crystal panel U103 and a polarizing plate U104. The measurement apparatus 1000A also has a light detection unit 21 including a distance measurement optical system 22 consisting of a polarizing beam splitter U105 and an objective optical system U106, and a sensor unit 23 having a light receiving surface located at an image plane IP.

[0040] The illumination light emitted from the laser light source U101 is collimated by a collimator lens U201 as a collimating means and is then irradiated onto the transmissive liquid crystal panel U103. The transmissive liquid crystal panel U103 has a plurality of adjacent light modulation sections (corresponding to pixels), and the illumination light is incident on and passes through these light modulation sections, thereby splitting the illumination light into a plurality of light beams each having a uniform intensity. A lens array may be provided to focus each of the plurality of light beams that have passed through the transmissive liquid crystal panel U103.

[0041] Generally, a laser light source emits laser light with a Gaussian intensity distribution, and the collimated illumination light also has an intensity distribution with high intensity at the center and low intensity at the periphery. To improve the uniformity of the intensity of multiple light beams, it is desirable for the intensity distribution of the collimated illumination light to be uniform. The laser light source U101 is composed of a laser element, a first deflection element, and a second deflection element. The light emitted from the laser element with a Gaussian intensity distribution is deflected by the first deflection element into light with a uniform intensity distribution, and then collimated by the second deflection element. Each deflection element is an optical element such as a metasurface, a diffractive element, or an aspherical collimator lens. The first deflection element and the second deflection element may be provided on both sides of a single element. While the cross section of a typical collimated light beam is circular or elliptical, it is desirable to shape the collimated light beam into a rectangular cross section using the second deflection element.

[0042] In this embodiment, the illumination light emitted from the laser light source U101 is polarized light polarized in the y direction in the figure. The illumination light polarized in the y direction is perpendicularly incident on the transmissive liquid crystal panel U103. The transmissive liquid crystal panel U103 is capable of modulating the polarization state of light passing through the light modulation unit. Of the light that passes through the transmissive liquid crystal panel U103, the polarized light polarized in the x direction passes through the polarizing plate U104 and is irradiated onto the object U107 via the distance measurement optical system 22. On the other hand, of the light that passes through the transmissive liquid crystal panel U103, the polarized light polarized in the y direction is absorbed by the polarizing plate U104.

[0043] By using the transmissive liquid crystal panel U103, the illumination light from the light source unit 12 can be divided into multiple lights of uniform intensity, and the timing (irradiation time) at which these lights are irradiated toward the object U107 can be controlled.

[0044] The multiple light beams (polarized light beams) that have passed through the polarizing plate U104 are reflected by the polarization splitting surface of the polarizing beam splitter U105 and are irradiated onto multiple points on the object via the objective optical system U106. The reflected light beams that have been specularly reflected from the multiple points enter the polarizing beam splitter U105 from the objective optical system U106, pass through the polarization splitting surface, and reach the light receiving surface (IP) of the sensor unit 23.

[0045] In this embodiment, a bending optical system including a polarizing beam splitter U105 is used as the distance measuring optical system 22, which enables the size of the distance measuring device 1000A to be reduced. In this embodiment, the transparent liquid crystal panel U103 and the sensor unit 23 are arranged at positions conjugate with the objective optical system U106.

[0046] The flowchart in FIG. 5 shows the process (measurement method) that the timing control section 31 and the control section 61 execute according to a program in this embodiment.

[0047] First, in step S101, the control unit 61 causes the light source unit 12 to emit light and irradiate the object U107 with illumination light as a plurality of lights via the splitting unit 13 and the distance measurement optical system 22. Specifically, the control unit 61 causes the timing control unit 31 to transmit a light emission control signal to the light source unit 12.

[0048] Next, in step S102, the control unit 61 determines whether illumination light has been emitted from the light source unit 12 and distance measurement (light detection by the sensor unit 23) has started, and if it has started, proceeds to step S103.

[0049] In step S103, the control unit 61 acquires time information indicating the irradiation time when the light source unit 12 emits light.

[0050] Next, in step S104, the control unit 61 controls each light modulation unit of the transmissive liquid crystal panel U103. Specifically, each light modulation unit is controlled so that polarized light having a polarization direction in the x direction is transmitted through the transmissive liquid crystal panel T103. As a result, the illumination light incident on the transmissive liquid crystal panel U103 is split into multiple light beams that are then emitted from the transmissive liquid crystal panel T103. In other words, by controlling each light modulation unit of the transmissive liquid crystal panel T103, it is possible to control the time at which the illumination light (multiple light beams) is irradiated onto an object. The multiple light beams emitted from the transmissive liquid crystal panel T103 are irradiated with uniform intensity onto multiple points on the object.

[0051] Next, in step S105, the control unit 61 causes the sensor unit 23 to detect reflected light from the object, and acquires two-dimensional light detection information.

[0052] Next, in step S106, the control unit 61 acquires time information indicating the time at which the reflected light was detected for each pixel in the sensor unit 23 from the two-dimensional light detection information.

[0053] Next, in step S107, control unit 61 causes arithmetic processing unit 51 to calculate the TOF from the irradiation time acquired in step S103 to the detection time acquired in step S106 for each pixel of sensor unit 23. Then, arithmetic processing unit 51 calculates distance information based on the TOF calculated for each pixel of sensor unit 23, and further causes arithmetic processing unit 51 to generate distance image data using the distance information and display the distance image data on display unit 71.

[0054] The order of the processes in steps S103 and S104 may be reversed, and the order of the processes in steps S105 and S106 may be reversed.

[0055] Furthermore, the control unit 61 may calculate distance information for a pixel using the time information obtained in steps S103 and S106 only when the intensity of reflected light is equal to or greater than a predetermined threshold in the light detection information obtained for each pixel of the sensor unit 23 in step S105. Furthermore, the control unit 61 may calculate distance information only for pixels for which the detection time obtained in step S106 is equal to or greater than a predetermined threshold from the irradiation time obtained in step S103. In other words, if the TOF is too short for the distance to the object, distance information is not calculated using that TOF. This makes it possible to avoid erroneous calculation of distance information due to the sensor unit 23 detecting unnecessary light other than reflected light from the object.

[0056] Furthermore, in this embodiment, the transmissive liquid crystal panel U103 is used in the dividing section 13, but a reflective liquid crystal panel may be used instead.

[0057] FIG. 6 shows the configuration of a measuring apparatus 1000B according to a second embodiment. The measuring apparatus 1000B includes an illumination unit 11 including a light source unit 12 consisting of a laser light source U101 and a collimator lens U201, and a splitting unit 13 consisting of a light guide U212 and a digital micromirror device (hereinafter simply referred to as a mirror device) U231. The measuring apparatus 1000B also includes a distance measurement optical system 22 consisting of a polarizing beam splitter U105 and an objective optical system U106, and a light detection unit 21 including a sensor unit 23 having a light receiving surface disposed at an image plane IP. The measuring apparatus 1000B of this embodiment differs from the first embodiment in the configuration of the splitting unit 13, but the other configurations are the same. In this embodiment, the mirror device U231 and the sensor unit 23 are positioned conjugate with respect to the objective optical system U106.

[0058] 7 shows the configuration of the light guide U212. The light guide U212 has a first surface on the light source side and a second surface on the mirror device side, opposite the first surface. A first dielectric film U212a, a second dielectric film U212b, a third dielectric film U212c, a fourth dielectric film U212d, and a sixth dielectric film U212f are formed in different regions on the second surface. A fifth dielectric film U212e is formed as a reflector on the first surface.

[0059] The first to third dielectric films U212a to U212c are each a separator that divides the incident illumination light at a predetermined rate (transmitting a portion and reflecting the remainder). Ideally, the transmittance of the first dielectric film U212a is 25%, the transmittance of the second dielectric film is 33.3%, and the transmittance of the third dielectric film is 50%. In this embodiment, the refractive index of the material of the light guide U212 is n = 1.52, and the angle θ = 21.6°.

[0060] Illumination light L11 incident from the light source unit 12 into the light guide U212 from an area of ​​the first surface where the fifth dielectric film U212e is not formed propagates through the light guide U212 while being reflected between the sixth dielectric film U212f and the fifth dielectric film U212e. The fifth dielectric film U212e and the sixth dielectric film U212f have the property of reflecting the illumination light at an angle θ.

[0061] The illumination light L13a (75% of L11) reflected by the first dielectric film U212a is reflected by the fifth dielectric film U212e and enters the second dielectric film U212b at an angle θ. The illumination light L12a (25% of L11) transmitted through the first dielectric film U212a is directed toward the mirror device U231 at an angle θa. The illumination light L13b (50% of L11) reflected by the second dielectric film U212b is reflected by the fifth dielectric film U212e and enters the third dielectric film U212c at an angle θ. The illumination light L12b (25% of L11) transmitted through the second dielectric film U212b is directed toward the mirror device U231 at an angle θa. Furthermore, illumination light L13c (25% of L11) reflected by the third dielectric film U212c is reflected by the fifth dielectric film U212e and enters the fourth dielectric film U212d at an angle θ. At this time, illumination light L12c (25% of L11) transmitted through the third dielectric film U212c is directed toward the mirror device U231 at an angle θa. The fourth dielectric film U212d is an anti-reflection film, and transmits the incident illumination light L13c as illumination light L12d (25% of L11) at an angle θa. In this way, the illumination light from the light source unit 12 is divided into multiple light beams with uniform intensity.

[0062] 8 shows how illumination light incident on the mirror device U231 from the light guide U212 passes through the light guide U212 and proceeds toward the polarizing beam splitter U105 shown in FIG. 6. The mirror device U231 has multiple light modulation units each made up of tiny movable mirrors, and controls the reflection direction of the incident light by changing the tilt angle of each movable mirror. In this example, when the movable mirror has a deflection angle of 17°, light incident at an angle θa = 34° is emitted at an exit angle of 0° (the angle at which light is perpendicularly incident on the first and second surfaces of the light guide plate U212).

[0063] In this embodiment, three types of dielectric films with different transmittances (reflectances) are used as the first to third dielectric films U212a to U212c that separate the incident light, but two or more types of dielectric films (N types) may be used. The N types of dielectric films are designated as the first dielectric film, the second dielectric film, ..., the Nth dielectric film, and the transmittance at the angle of the principal ray of the dominant wavelength incident on the Mth dielectric film is designated as T[M]. In this case, it is preferable to satisfy the following condition: T[N] / T[N-1]>1.1 (1). If T[N] / T[N-1] is below the lower limit of formula (1), the ratio of the amount of light transmitted through the (N-1)th dielectric film and the Nth dielectric film deviates from 1, resulting in intensity unevenness in the illumination light (multiple light beams) reaching the mirror device U231.

[0064] It is more preferable that the numerical range of the formula (1) is as follows:

[0065] T[N] / T[N-1]>1.2 (1a) Furthermore, it is more preferable to set the numerical range of the formula (1) as follows.

[0066] T[N] / T[N-1]>1.3 (1b) In order to make the light guide U212 thin, it is necessary to increase the angle θ of the illumination light propagating inside. According to Snell's law, the smaller the refractive index for the same incident angle, the larger the angle θ. Therefore, it is desirable that the refractive index n of the material of the light guide U212 satisfy the following condition: n<1.80 (2)

[0067] It is more preferable to set the numerical range of the formula (2) as follows:

[0068] n<1.60 (2a) The flowchart in FIG. 9 shows the process (measurement method) that the timing control unit 31 and the control unit 61 execute according to a program in this embodiment.

[0069] First, in step S201, the control unit 61 causes the light source unit 12 to emit light, and irradiates the object U107 with illumination light as a plurality of lights via the splitting unit 13 and the distance measurement optical system 22. Specifically, the control unit 61 causes the timing control unit 31 to transmit a light emission control signal to the light source unit 12.

[0070] Next, in step S202, the control unit 61 determines whether illumination light has been emitted from the light source unit 12 and distance measurement (light detection by the sensor unit 23) has started, and if so, proceeds to step S203.

[0071] In step S203, the control unit 61 acquires time information indicating the irradiation time when the light source unit 12 emits light.

[0072] Next, in step S204, the control unit 61 controls the angle (tilt) of each movable mirror in the mirror device U231. Specifically, the control unit 61 controls each movable mirror so that each of the multiple beams of light split by the light guide U212 with uniform intensity is reflected by the movable mirror and irradiated onto multiple points on the object. By controlling the angle of each movable mirror in the mirror device U231 in this way, it is possible to control the irradiation time of the illumination light (multiple beams of light) onto the object.

[0073] Next, in step S205, the control unit 61 causes the sensor unit 23 to detect reflected light from the object, and acquires two-dimensional light detection information.

[0074] Next, in step S206, the control unit 61 acquires time information indicating the time at which the reflected light was detected for each pixel in the sensor unit 23 from the two-dimensional light detection information.

[0075] Next, in step S207, the control unit 61 determines whether the intensity of the reflected light from the object U107 is equal to or greater than a threshold in the light detection information acquired in step S205 for each pixel of the sensor unit 23. Then, in step S208, the control unit 61 selects pixels whose intensity is equal to or greater than the threshold.

[0076] Next, in step S208, the control unit 61 determines, for each pixel selected in step S207, whether the detection time acquired in step S206 is a time that is equal to or greater than a predetermined threshold value from the irradiation time acquired in step S203. Then, in step S209, the control unit 61 selects pixels whose detection time is equal to or greater than the threshold value from the irradiation time.

[0077] Next, in step S211, control unit 61 causes calculation processing unit 51 to calculate, for each pixel selected in step S208, the TOF from the irradiation time acquired in step S203 to the detection time acquired in step S206. Then, calculation processing unit 51 calculates distance information based on the TOF calculated for each pixel, generates distance image data using the distance information, and displays the distance image data on display unit 71.

[0078] The order of the processes in steps S203 and S204 may be reversed, and the order of the processes in steps S205 and S206 may be reversed.

[0079] 10 shows an example in which unwanted light generated in the polarizing beam splitter U105 and the objective optical system U106 and reflected light (normal light) from the object U107 are detected by the light detection unit 21. The vertical axis represents the intensity of the detected light (or the number of photons), and the horizontal axis represents the detection time relative to the irradiation time.

[0080] The intensity threshold is a threshold used to determine the intensity of the light reflected from the object U 107 in step S207 of Fig. 9. The time threshold is a threshold used to determine the detection time in step S208.

[0081] At least one of light whose intensity is less than an intensity threshold and light whose elapsed time from the time of irradiation to the time of detection (TOF) is shorter than a time threshold is regarded as unwanted light and is not used in distance calculation, whereas light whose intensity is equal to or greater than the intensity threshold and whose elapsed time from the time of irradiation to the time of detection is equal to or greater than a time threshold is regarded as normal light and is used in distance calculation.

[0082] 11 shows a schematic configuration of the splitting unit 13 (transmissive liquid crystal panel U103 and mirror device U231) in Examples 1 and 2. U131 denotes one rectangular light modulation unit of the splitting unit 13, and U132 denotes a rectangular cross section of light transmitted or reflected by the light modulation unit. W1 denotes the diagonal length of the light modulation unit U131, and W2 denotes the width in the diagonal length direction (diagonal length or diameter) of the cross section of light U132.

[0083] In Examples 1 and 2, it is preferable to satisfy the condition: 0.7<W2 / W1≦1.0 (3). By satisfying the condition of Expression (3), it is possible to split the illumination light from the light source unit 12 into multiple light beams spaced sufficiently closely together, and to irradiate the multiple light beams onto multiple points on the object U107 that are spaced sufficiently closely together. This solves the problem of multiple light beams being irradiated onto the object in a discrete manner when the above-mentioned VCSEL array is used as the light source unit. In other words, Examples 1 and 2 enable highly accurate distance measurement with sufficient resolution and FPS compared to when a VCSEL array is used.

[0084] It is more preferable to set the numerical range of the formula (3) as follows:

[0085] 0.75<W2 / W1<0.98 (3a) (Other Examples) The present invention can also be realized by a process in which a program that realizes one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0086] The embodiments described above are merely representative examples, and various modifications and alterations are possible to each embodiment when implementing the present invention.

Claims

1. A measuring device comprising: a light source unit; a splitting means for splitting illumination light from the light source unit into multiple light beams that are irradiated toward multiple points on an object; a control means for controlling the irradiation of the multiple light beams onto the object; a detection means having multiple photoelectric conversion units arranged in two dimensions and detecting multiple reflected light beams from the multiple points; and a processing means for acquiring information about the object for each photoelectric conversion unit based on the light flight time from the irradiation of the multiple light beams to the detection of the reflected light for each photoelectric conversion unit.

2. The measuring device according to claim 1, further comprising an optical system that irradiates the plurality of light beams toward the object and directs the plurality of reflected light beams to the detecting means, wherein the splitting means and the detecting means are disposed in conjugate positions with respect to the optical system.

3. The measuring apparatus according to claim 1 or 2, wherein said splitting means splits said illumination light into said plurality of lights having uniform intensity.

4. A measuring device as claimed in any one of claims 1 to 3, characterized in that the splitting means has a plurality of optical modulation sections and splits the illumination light incident on the plurality of optical modulation sections into the plurality of lights.

5. The measuring device according to claim 4, characterized in that the splitting means is a liquid crystal panel capable of modulating the polarization state of light for each of the optical modulation sections, and the control means controls the irradiation by controlling the optical modulation sections.

6. The measuring device described in claim 4, characterized in that the splitting means comprises: a light guide having a reflecting portion on a first surface and a plurality of separation portions which transmit a portion of light incident on a second surface opposite the first surface and reflect the remainder; and a mirror device having a plurality of movable mirrors which constitute the light modulation portion; in the light guide, the illumination light is propagated by reflection at the reflecting portion and the plurality of separation portions, and the light transmitted through each of the plurality of separation portions is emitted towards the mirror device; the light from each of the plurality of separation portions is reflected by the plurality of movable mirrors of the mirror device and emitted as the plurality of light beams; and the control means controls the irradiation by controlling the movable mirrors.

7. A measuring device as claimed in any one of claims 4 to 6, characterized in that, when the diagonal length of the optical modulation section is W1 and the width of the light emitted from the optical modulation section is W2, the following condition is satisfied: 0.7<W2 / W1≦1.

0.

8. A measuring device according to any one of claims 1 to 7, characterized in that the information relating to the object is a distance to the object.

9. A measuring device as described in any one of claims 1 to 8, characterized in that the processing means acquires information about the object using a photoelectric conversion unit among the multiple photoelectric conversion units of the detection means in which at least one of the intensity of the reflected light and the time of flight of light is equal to or greater than a predetermined value.

10. A measuring device according to any one of claims 1 to 9, characterized in that the photoelectric conversion section is constituted by an avalanche photodiode.

11. A measurement method comprising: splitting illumination light from a light source unit into multiple light beams that are irradiated toward multiple points on an object; controlling the irradiation of the multiple light beams onto the object; detecting multiple reflected light beams from the multiple points using multiple photoelectric conversion units arranged in two dimensions; and acquiring information about the object for each photoelectric conversion unit based on the light flight time from the irradiation of the multiple light beams to the detection of the reflected light for each photoelectric conversion unit.

12. A program for causing a computer to execute the process according to the measurement method of claim 11.

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