Measurement device, processing device and measuring method

Abstract

To provide a compact measurement device that is able to obtain information on an object, such as a distance, highly accurately.SOLUTION: A measurement device includes: a light-emitting element array 111; a light-receiving element array 121; and a light separation element 150 having a separation unit 151 that separates light from the light-emitting element array into emission light to be emitted to an object via an optical system 130 and reference light to be guided to the light-receiving element array, the light separation element being configured to guide signal light of the emission light, which is reflected by the object and enters via the optical system, to the light-receiving element array via the separation unit. Information on the object is acquired by using a first time from a light-emission instruction to the light-emitting element array to reception of the reference light in the light-receiving element array and a second time from the light-emission instruction to reception of the signal light in the light-receiving element array. Reflection means 152 for reflecting the reference light from the separation unit so as to return it to the separation unit is provided, and the reference light from the reflection means is guided to the light-receiving element array via the separation unit.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a measuring device using the ToF (Time of Flight) method.

Background Art

[0002] In the ToF method, the distance to an object is measured based on the time from when light is irradiated onto the object until the reflected light from the object is detected. Patent Document 1 discloses a measuring device having a detector that detects a part of the irradiated light from a laser light source as reference light, and a detector that detects signal light generated by the irradiation light being reflected by an object, and that improves the ranging accuracy by using the cross-correlation between the reference light and the signal light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the measuring device of Patent Document 1, it is necessary to prepare an optical system for detecting reference light separately from the optical system for receiving signal light, and the device becomes large-sized.

[0005] The present invention provides a small-sized measuring device and a measuring method capable of obtaining information about an object such as distance with high accuracy.

Means for Solving the Problems

[0006] A measuring device and a measuring method according to one aspect of the present invention include a light-emitting element array including a plurality of light-emitting elements, a light-receiving element array including a plurality of light-receiving elements, an optical system, and a separating unit that separates light from the light-emitting element array into irradiation light irradiated onto an object through the optical system and reference light guided to the light-receiving element array, and a light separation element that guides signal light, which is reflected by the object among the irradiation light and incident through the optical system, to the light-receiving element array through the separating unit. Further, it has a processing means for acquiring information about the object using a first time from a light emission instruction to the light-emitting element array to reception of the reference light in the light-receiving element array and a second time from the light emission instruction to reception of the signal light in the light-receiving element array. It has a reflecting means for reflecting the reference light from the separating unit back to the separating unit, and is characterized in that the reference light from the reflecting means is guided to the light-receiving element array through the separating unit. Note that a processing device that includes the above-described measuring device and performs processing using information about the object also constitutes another aspect of the present invention.

Effects of the Invention

[0007] According to the present invention, it is possible to provide a small-sized measuring device and a measuring method capable of obtaining information about an object such as distance with high accuracy.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Examples

[0010] [Configuration of the Distance Measuring Device] FIG. 1 shows the configuration of a distance measuring device as a measuring device according to Example 1 of the present invention. Solid lines connecting the components in the figure indicate the exchange of signals, dashed lines indicate the irradiation light projected (irradiated) onto the object, and dash-dotted lines indicate the signal light that is the reflected light from the object.

[0011] The distance measuring device is composed of a light projecting unit 110, a measuring unit 120, an imaging lens 130 as an optical system, an overall control unit 140 as a processing means, and a beam splitter 150 as a light separation element. The light projecting unit 110 is composed of a light source unit 113 including a light emitting element array 111 in which a plurality of light emitting elements are arranged in a two-dimensional array and a light emitting element driving unit 112 for driving each light emitting element, and a light source control unit 114.

[0012] The measuring unit 120 is composed of a light receiving element array 121 including a plurality of light receiving elements, a TDC (Time-to-Digital Convertor) array unit 122, a signal processing unit 123, a measurement control unit 124, and a row selection circuit 125. In the light receiving element array 121, the plurality of light emitting elements are two-dimensionally arranged so as to form a plurality of rows.

[0013] It is desirable to arrange a band-pass filter on the light receiving element array that transmits light in a wavelength range including the wavelength of the light emitted from each light emitting element and reflects or absorbs light in other wavelength ranges.

[0014] The beam splitter 150 has a half mirror 151 as a separation unit that transmits a part of the incident light and reflects the rest, and a reflection structure unit 152 as a reflection means.

[0015] The irradiation light as pulsed light emitted from the plurality of light emitting elements of the light emitting element array 111 in the light source unit 113 is respectively projected in different directions in space through the imaging lens 130. The signal light reflected from an object in the space among the irradiation light is received by a light receiving element corresponding to the light emitting element that has emitted light among the plurality of light receiving elements in the light receiving element array 121 through the imaging lens 130. In the light receiving element array 121, the plurality of light receiving elements are two-dimensionally arranged so as to form a plurality of rows.

[0016] The time from when the light-emitting element emits light until the signal light is received by the light-receiving element is the flight time ToF (Time of Flight), and this flight time is calculated using the measurement result of the TDC array unit 122. At this time, in order to reduce ranging errors due to noise components caused by ambient light and dark counts, the influence of noise in the measurement circuit, and the light emission delay of the light-emitting element from the light emission instruction (start of time counting), the light emission of the irradiation light and the time counting are repeated. Then, the signal processing unit 123 creates a histogram of the measurement results and performs noise component removal and averaging of the measurement results. The light emission delay time of the light-emitting element from the light emission instruction varies depending on individual differences such as the buffer in the light-emitting element drive unit 112, the light-emitting element, the light-receiving element, the TDC array unit 122, and the signal transmission path, and temperature characteristics. Therefore, a part of the irradiation light actually emitted from the light-emitting element is detected as reference light, and the flight time ToF is calculated by subtracting the light emission delay time from the light emission instruction time to the detection time of the reference light from the time from the light emission instruction time to the detection time of the signal light.

[0017] By substituting the thus obtained flight time ToF into the following formula (1), the distance L to the object can be obtained with high precision. In formula (1), c is the speed of light.

[0018] L = ToF × c / 2 (1) Note that by using ToF, not only the distance information (L) to the object but also information about the object including the shape of the object can be obtained.

[0019] [Light Projection Unit] FIG. 2 shows a configuration example of the light source unit 113 and the light source control unit 114 that constitute the light projection unit 110. In the light-emitting element array 111, a plurality of VCSELs (Vertical Cavity Surface Emitting LASERs) are arranged in a two-dimensional array so as to form a plurality of rows on the substrate as the light-emitting elements 201. The light-emitting element drive circuit 112 is configured to arrange the row drive circuits 202 in a one-dimensional array.

[0020] The light-emitting element is not limited to a VCSEL, but preferably one that can be integrated in a one-dimensional or two-dimensional array. For example, an edge-emitting laser, an LED (light-emitting diode) can be mentioned. As the light-emitting element array, when an edge-emitting laser is used instead of a VCSEL array as the light-emitting element, a laser bar arranged in a one-dimensional array on a substrate or a laser bar stack in which these are stacked to form a two-dimensional light-emitting element array configuration can be used. Furthermore, when an LED is used as the light-emitting element, one in which LEDs are arranged in a two-dimensional array on a substrate can be used.

[0021] In the distance measuring device of this embodiment, in order to suppress the influence of ambient light, it is preferable that the wavelength of the light emitted by the light-emitting element is in the near-infrared band. In this case, the VCSEL is fabricated using a semiconductor process with materials used in conventional edge-emitting lasers and surface-emitting lasers, and a GaAs-based semiconductor material can be used as the main material when emitting light with a wavelength in the near-infrared band. In this case, the dielectric multilayer film forming the DBR (distributed Bragg reflector) mirror constituting the VCSEL can be composed of two thin films made of materials with different refractive indices alternately and periodically laminated (GaAs / AlGaAs). The wavelength of the light emitted from the VCSEL can be changed by adjusting the combination and composition of the elements of the compound semiconductor.

[0022] In addition, the VCSELs constituting the VCSEL array are provided with electrodes for injecting current and holes into the active layer. The electrodes are shared by a plurality of VCSELs in the row direction and are connected to the row drive circuits 202 arranged in each row. By operating only a specific row drive circuit 202 among the light-emitting element drive circuits 112, current injection is performed only on a plurality of VCSELs (first light-emitting elements) belonging to a specific row (light-emitting element row), and it is possible to simultaneously emit light from the plurality of VCSELs in the specific row.

[0023] By switching the operating row drive circuit 202, it is possible to sequentially emit light from the VCSELs in a plurality of rows one by one.

[0024] [Configuration of the Measurement Unit] FIG. 3 shows the configuration of the measurement unit 120. The measurement unit 120 includes a light receiving element array 121 having a plurality of pixels 301 arranged in a two-dimensional array, a TDC array section 122, a signal processing section 123, and a measurement control section 124. Further, the measurement unit 120 includes a row selection circuit 125 for activating only a specific row, a row selection pulse wiring 303 for outputting the output signal of the row selection circuit 125 to the pixel 301, and a pixel output line 304 for outputting the pixel output signal from the pixel 301 to the TDC array section 122.

[0025] FIG. 4 shows the configuration of the pixel 301. The pixel 301 is composed of a SPAD (Single Photon Avalanche Diode) 401 as a light receiving element, a load transistor 402, an inverter 403, a pixel output circuit 404, a row selection pulse line 303, and a pixel output line 304. The SPAD 401 has a light receiving region and an avalanche region.

[0026] The light incident on the SPAD 401, that is, photons, are photoelectrically converted in the light receiving region, thereby generating electrons and holes. The positively charged holes are discharged through the anode electrode Vbd. The negatively charged electrons are transported as signal charges to the avalanche region by an electric field set so that the potential becomes lower toward the avalanche region in the light receiving region. The signal charges reaching the avalanche region cause an avalanche breakdown due to the strong electric field in the avalanche region, thereby generating an avalanche current.

[0027] When no avalanche current is flowing, the voltage of the anode electrode Vbd is set so that a reverse bias of equal to or higher than the breakdown voltage is applied to the avalanche region of the SPAD 401. At this time, since no current flows through the load transistor 402, the cathode potential Vc is a voltage close to the power supply voltage Vdd, and the inverter output signal is "0".

[0028] When an avalanche current is generated in SPAD401 upon arrival of photons, the cathode potential Vc drops, and the output of inverter 403 is inverted. That is, the inverter output changes from "0" to "1". When the cathode potential Vc drops, the reverse bias applied to SPAD401 decreases. When the reverse bias becomes lower than the breakdown voltage, the generation of the avalanche current stops.

[0029] Thereafter, when a hole current flows from the power supply voltage Vdd to the cathode potential Vc via the load transistor 402, the cathode potential Vc rises, the inverter output returns from "1" to "0", and it returns to the state before the arrival of photons.

[0030] Also, in the pixel 301 where the row selection pulse wiring 303 is on, the output of the inverter 403 is controlled to be output from the pixel output circuit 404 to the pixel output line 304. In the pixel 301 where the row selection pulse wiring 303 is off, the inverter output is controlled to be disconnected from the pixel output line 304. Therefore, it is possible to detect only the light incident on a specific row (light receiving element row) selected by the row selection circuit 125 at the pixel 301.

[0031] In this way, pixel output signals corresponding to light detection in a plurality of pixels 301 belonging to the row selected by the row selection circuit 125 are output to the TDC array unit 122 as low-delay digital signals.

[0032] In the TDC array unit 122, the time from when the light emitting element array 111 emits light until the pixel output signal changes from "0" to "1" is measured as ToF.

[0033] Figure 5 schematically shows the TDC array unit 122. In the TDC array unit 122, TDC501 is provided in a number twice the number of pixels 301 in the horizontal direction in the light receiving element array 121, and pixel output signals from two rows of pixels 301 are measured simultaneously. One of the two rows of pixels 301 is used as a pixel for detecting signal light from an object, and the other row of pixels 301 is used as a pixel for detecting reference light.

[0034] Each TDC501 has an oscillator 511, an oscillation count circuit 521, and a synchronization clock count circuit 531. The count value in the synchronization clock count circuit 531 is responsible for the upper bits, the internal signal of the oscillator 511 is responsible for the lower bits, and the count value in the oscillation count circuit 521 is responsible for the intermediate bits in between. That is, the pixel output signal is roughly measured by the synchronization clock count circuit 531, more finely measured by the internal signal of the oscillator 511, and the interval therebetween is measured by the oscillation count circuit 521. Note that a configuration in which redundant bits are provided for each of the upper and intermediate bits may be adopted.

[0035] FIG. 6 schematically shows the configuration of the oscillator 511 of the TDC501. The oscillator 511 includes an oscillation start / stop signal generation unit 640, buffers 611 to 618, an oscillation switch 630, and a delay adjustment current source 620. The buffers 611 to 618 and the oscillation switch 630 are alternately connected in an 8-stage loop.

[0036] FIG. 7 shows the output signals of the buffers 611 to 618 and the internal signal of the oscillator 511 at the time of reset, and the output signals of the buffers 611 to 618 and the internal signal of the oscillator 511 after a certain period of time has elapsed since the oscillation switch 630 was turned on.

[0037] The outputs of the buffers 611 to 617 at the time of reset are “0”, and the output of the buffer 618 is “1”. After the delay time t of one buffer stage has elapsed since the oscillation switch 630 was turned on buff the outputs of the buffers 612 to 618 for which input / output alignment is achieved do not change, and only the output of the buffer 611 for which input / output alignment is not achieved changes from “0” to “1” (the signal advances by one stage). Further, after the delay time t of one buffer stage buff has elapsed (after 2×t buff ), the outputs of the buffers 611 and 613 to 618 for which input / output alignment is achieved do not change, and only the output of the buffer 612 for which input / output alignment is not achieved changes from “0” to “1”. In this way, the delay time t of one buffer stage buffEach time, the output of one buffer with inconsistent input and output changes sequentially. After the oscillation switch 630 is turned on, 8×t buff After that, the outputs of all buffers 611 to 618 change (the signal makes one round), 16×t buff After that, all the buffers change further (the signal makes two rounds) and return to the original state. After that, 16×t buuf The same operation is repeated each time. By doing so, time measurement is performed with a time resolution of t buff Also, this time resolution t buff is adjusted to be 1 / 2 of the synchronization clock by the oscillation adjustment voltage generation circuit 541 described later 7 .

[0038] Also, the oscillator output, which is the output of the buffer 618, is input to the oscillation count circuit 521. By counting the rising edge of the oscillator output in the oscillation count circuit 521, time measurement is performed with a time resolution of 16×t buff .

[0039] Figure 8 shows the SPAD cathode potential Vc, the pixel output signal, the synchronization clock, the synchronization clock count value, the output of the oscillation start / stop signal generation unit 640 (oscillation start / stop signal), the oscillator output, and the count value in the oscillation count circuit 521 (oscillation count value) at the time from when the light-emitting element 201 belonging to a specific row of the light-emitting element array 111 emits light until the SPAD 401 receives light and the counting operation of the TDC 501 ends. The SPAD cathode potential Vc is an analog voltage, and the upper side in the figure is shown as the higher potential. The synchronization clock, the oscillation start / stop signal, and the oscillator output are digital signals, and the upper side in the figure is shown as on and the lower side as off. The synchronization clock count value and the oscillator count value are digital values and are shown as decimal numerical values.

[0040] FIG. 9 also shows the oscillation start / stop signal, oscillator output, oscillator count value, and internal signal of oscillator 511 (oscillator internal signal) from time 803 to time 805 in FIG. 8. The oscillator internal signal is a digital value and is shown as a decimal numerical value.

[0041] Using FIGS. 8 and 9, the measurement operation (TDC operation) of TDC 501 in the time period from the time 801 when the light-emitting element 201 belonging to a specific row of the light-emitting element array 111 emits light to the time 803 when the SPAD 401 in the pixel 301 receives light (photons) will be described.

[0042] At time 801 synchronized with the rising time of the synchronization clock supplied via the overall control unit 140 shown in FIG. 1, a light-emitting signal indicating a light-emitting instruction is output from the overall control unit 140 to the light source unit 113. The synchronization clock count circuit 531 shown in FIG. 5 starts counting the rising edges of the synchronization clock from the time when the light-emitting signal is input.

[0043] When photons reflected by the object are received by the SPAD 401 at time 803, the SPAD cathode potential Vc drops, and the pixel output signal changes from "0" to "1". In response to the pixel output signal becoming "1", the oscillation start / stop signal changes from "0" to "1", and the oscillation switch 630 turns on. When the oscillation switch 630 turns on, the oscillation operation of the oscillator 511 starts, and the loop of the oscillator internal signal starts as shown in FIG. 9. Every time the oscillator internal signal makes two rounds, a rising edge appears in the oscillator output, and the oscillator count circuit 521 counts that number. Also at time 803, the synchronization clock count circuit 531 stops counting and holds the count value at that time.

[0044] After the oscillation switch 630 is turned on, the timing at which the synchronous clock first rises is time 805. In response to the rise of the synchronous clock, the oscillation start / stop signal becomes "0" and the oscillation switch 630 turns off. At the timing when the oscillation switch 630 turns off, the oscillation of the oscillator 511 ends and the internal signal of the oscillator is held as it is. Also, since the oscillation stops, the counting in the oscillation count circuit 521 also stops.

[0045] By doing so, the synchronous clock count value D, which is the count result of the synchronous clock count circuit 531 Gclk is the value counted every time of the time from time 801 to time 802 by 2 7 ×t buff Also, the oscillation count value D, which is the count result of the oscillation count circuit 521 ROclk is the value counted every time of the time from time 803 to time 804 by 2 4 ×t buff Furthermore, the internal signal D of the oscillator ROin is the value counted every time of the time from time 804 to time 805 by t buff The TDC 501 performs the following processing using these count values D Gclk , D ROclk and the internal signal D of the oscillator ROin and outputs the count value D ToF after the processing to the signal processing unit 123 to complete one TDC operation.

[0046] First, the oscillation count value D ROclk and the internal signal D of the oscillator ROin are added together as in the following formula (2).

[0047] D RO =2 4 ×D ROclk +D ROin (2) D RO is the value counted every time of the time from time 804 to time 805 by t buff and the time from time 802 to time 805 is the period of the synchronous clock and is 27 ×t buff is equal to. Therefore, as shown in the following equation (3), subtract D from the synchronous clock, and add the result to D RO . This way, the flight time of light (the time from time 801 to time 803) is counted for each t Gclk , and the count value D buff is obtained. ToF

[0048] D ToF = 2 7 × D Gclk + (2 7 - D RO ) = 2 7 × D Gclk + (2 7 - 24 × D ROclk - D ROin ) (3) The delay time t buff for one buffer stage varies due to process factors such as manufacturing errors of transistors, voltage fluctuations applied to the TDC501, and temperature. Therefore, as shown in FIG. 5, an oscillation adjustment voltage generation circuit 541 is provided in the TDC array unit 122. The oscillation adjustment voltage generation circuit 541 is composed of a dummy oscillator 1001, a 1 / 23 frequency divider 1002, and a phase comparator 1003, as shown in FIG. 10. The dummy oscillator 1001 is the same oscillator as the oscillator 511 mounted on the TDC501.

[0049] The output of the dummy oscillator 1001 is input to the 1 / 2 3 frequency divider 1002. The 1 / 2 3 frequency divider 1002 outputs a clock signal having a clock frequency of 1 / 2 3 of the input clock frequency. The phase comparator 1003 receives the synchronous clock and the clock signal from the 1 / 2 3 frequency divider 1002. The phase comparator 1003 receives the frequency of the synchronous clock and 1 / 2 3 ​Compare with the frequency of the clock signal from the frequency divider 1002. When the frequency of the synchronous clock is high, increase the output voltage; when the frequency of the synchronous clock is low, lower the output voltage. By inputting the output voltage of the phase comparator 1003 to the delay adjustment current source 620 of the oscillator 511, the oscillation frequency of the oscillator 511 is adjusted to be 2 3 times that of the synchronous clock.

[0050] In this way, since the oscillation frequency of the oscillator 511 is determined based on the frequency of the synchronous clock, it is advisable to generate the synchronous clock based on the output (clock) from an external IC that can output a constant frequency regardless of the above-mentioned process factors, voltage fluctuations, and temperature. Thereby, it is possible to suppress the frequency variation of the synchronous clock due to the above-mentioned process factors, applied voltage, and temperature.

[0051] For example, by inputting a clock with a frequency of 160 MHz from an external IC as the synchronous clock to the oscillator 511, the oscillation frequency becomes 1.28 GHz, which is 8 times the synchronous clock frequency. The delay time t for one buffer stage, which is the time resolution buff is 48.8 ps.

[0052] [Optical paths of reference light and signal light] Figure 11(A) schematically shows a beam splitter 150, a light emitting element array 111, a light receiving element array 121, and an imaging lens 130. The light emitting element array 111 and the light receiving element array 121 are in a conjugate relationship (positions optically conjugate to each other with respect to the half mirror 151 of the beam splitter 150), and each light emitting element and each light receiving element are also in a one-to-one conjugate relationship, so they are associated with each other. The row numbers in the light emitting element array 111 are assigned in ascending order from the side with the smaller Yv in Fig. 11(A) to the side with the larger Yv, and the row numbers in the light receiving element array 121 are assigned in ascending order from the side with the smaller Y in the same figure to the side with the larger Y. The light emitting element and the light receiving element with the same row number are in a conjugate relationship.

[0053] Note that the number of rows (8) of the light-emitting element array 111 and the light-receiving element array 121 shown in FIG. 11(A) is merely an example, and other numbers of rows may be used. Further, the configuration is not limited to a one-to-one conjugate relationship between the light-emitting element and the light-receiving element, and the number of light-receiving elements may be n×n times the number of light-emitting elements, and one light-emitting element and n×n light-receiving elements may be configured to have a conjugate relationship.

[0054] FIG. 11(B) shows the optical path of the light emitted from the light-emitting element (first light-emitting element) of row number 1 in the light-emitting element array 111. The light 1110 emitted from the light-emitting element is separated into irradiation light 1111 that is reflected by the half mirror 151 of the beam splitter 150 and irradiates the object, and reference light 1112 that passes through the half mirror 151 and travels toward the reflection structure portion 152 of the beam splitter 150.

[0055] FIG. 11(C) shows the optical path of the reference light 1113 reflected by the reflection structure portion 152 so as to return to the half mirror 151. FIG. 11(D) shows the optical path of the signal light 1114 reflected by the object irradiated with the irradiation light and returning. The signal light 1114 from the object enters the light-receiving element (first light-receiving element) that is in a conjugate relationship with the light-emitting element that emitted light. On the other hand, the reference light 1113 reflected by the half mirror 151 enters the light-receiving element (second light-receiving element) in the row adjacent to the row of the light-receiving element that is in a conjugate relationship with the light-emitting element that emitted light.

[0056] On the surface of the reflection structure portion 152, a structure is provided in which the reflectance for light in a predetermined wavelength range including the wavelength of the light from the light-emitting element is higher than the reflectance for light in other wavelength ranges, and light in other wavelength ranges is transmitted or (and) absorbed. As this surface structure, a structure in which dielectrics having different refractive indexes are laminated may be used, or a structure using an absorption material such as metal may be used. Further, the reflection structure portion 152 has a triangular periodic structure having a period that is twice the interval in the row direction of the light-emitting elements, and has the same shape in the depth direction perpendicular to the plane of the drawing. The reflection structure portion 152 may be a semi-cylindrical periodic structure having the above period.

[0057] The reflection structure 152 having such a shape returns the reflected reference light 1113 to the half mirror 151 by shifting it by one line with respect to the incident reference light 1112. Then, the reference light 1113 reflected by the half mirror 151 is incident on the light receiving elements in the adjacent row of the row of light receiving elements conjugate to the light emitting element that emitted the light 1110. The row of light receiving elements that receives the reference light 1113 corresponds to the row whose Yv coordinate is different from that of the light emitting element that emitted light among the two rows corresponding to the period of the reflection structure 152.

[0058] In the distance measurement process described later, by subtracting the time from the output of the light emission instruction signal to the reception of the reference light 1113 from the time from the output of the light emission instruction signal to the reception of the signal light 1114, the distance measurement error due to the deviation of the light emission timing of the light emitting element with respect to the light emission instruction is reduced. Here, although the light emitted from the light emitting element with row number 1 has been described, the same applies to the light emitted from the light emitting elements with other row numbers.

[0059] [Distance Measurement Process] FIG. 12 shows a distance measurement process (measurement method) executed by the overall control unit 140 via the light source control unit 114 and the measurement control unit 124. The overall control unit 140, the light source control unit 114, and the measurement control unit 124 may be configured as a single computer such as a CPU, or may be configured by separate computers.

[0060] First, in step 1201, the overall control unit 140 resets the row counter j to 1.

[0061] Next, in step 1202, the overall control unit 140 causes the row selection circuit 125 to select the row of the pixel 301 corresponding to the row counter j and its adjacent row through the measurement control unit 124. Thereby, it is set such that the pixel output signals from the pixel 301 in the row that receives the signal light and the pixel 301 in the adjacent row that receives the reference light are output to the TDC array unit 122 via the pixel output line 304.

[0062] Next, in step 1203, the overall control unit 140 causes the measurement control unit 124 to reset the histogram circuits arranged in the signal processing unit 123 in the same number as the TDCs. Further, the overall control unit 140 resets the measurement count counter i to 0.

[0063] Next, in step 1204, the overall control unit 140 outputs a light emission instruction signal to the light source control unit 114 to cause the light emitting elements belonging to that row to emit light through the row drive circuit 202 of the row corresponding to the row counter j. Here, when the overall control unit 140 outputs the light emission instruction signal, at the same time, it causes the TDCs 501 in the corresponding row and its adjacent row in the TDC array unit 122 to start the TDC operation through the measurement control unit 124.

[0064] Next, in step 1205, the overall control unit 140 determines whether the time from the output of the light emission instruction signal is less than or equal to Tmax, which is the time corresponding to the maximum ranging distance. When it exceeds Tmax, the process of step 1209 described later is performed. When the time from the output of the light emission instruction signal is less than or equal to Tmax, it waits at step 1206 until the pixel output signal becomes "1".

[0065] During this waiting period, the signal light reflected by the object and returned is incident on and received by the light receiving element that has a conjugate relationship with the light emitting element that emitted light. When the pixel output signal becomes "1" due to this light reception, in step 1207, the time from the light emission of the light emitting element to the light reception of the light receiving element is measured by the TDC 501.

[0066] After that, in step 1208, the measurement result (TDC result) by the TDC 501 is stored in the histogram, and it returns to the waiting state again. In the process from the light emission in step 1204 to step 1209 (step 1216 indicated by the broken line in the figure), each light receiving element, TDC 501, and histogram circuit perform the operations of measurement and histogram calculation individually according to the change in the pixel output due to light reception.

[0067] On the other hand, in step 1209, the overall control unit 140 increments the measurement count counter i by 1.

[0068] Next, in step 1210, the overall control unit 140 determines whether the value of the measurement count counter i is greater than a predetermined number N total If the value of the measurement count counter i is less than the predetermined number N total is less, the determination in step 1205 is performed again. If it is greater than the predetermined number N total is greater, the process proceeds to step 1211.

[0069] In step 1211, the overall control unit 140 causes the signal processing unit 123 through the measurement control unit 124 to perform histogram processing for calculating the reference light time (first time) from the light emission instruction to the detection of the reference light and the signal light time (second time) from the light emission instruction to the detection of the signal light from the histogram of the TDC result. In the histogram processing, the intensity of the signal light, the intensity of the ambient light, etc. are also calculated.

[0070] Next, in step 1212, the overall control unit 140 calculates (acquires) the ToF by subtracting the reference light time from the signal light time obtained in step 1211. Details of this subtraction process will be described later.

[0071] Next, in step 1213, the overall control unit 140 causes the measurement control unit 124 to calculate the distance information by substituting the ToF calculated in step 1222 into Equation (1) and acquires this. In the process from step 1202 to step 1213, the distance measurement using one row of light emitting / receiving elements is completed.

[0072] Next, in step 1214, the overall control unit 140 increments the row counter j by 1.

[0073] Subsequently, in step 1215, the overall control unit 140 determines whether the row counter j is greater than a predetermined number of rows Nrow (for example, Nrow = 8 as shown in FIG. 11(A)). If it is less than the predetermined number of rows Nrow, the process in step 1204 is performed again to perform distance measurement in the next row. When the row counter j reaches the predetermined number of rows Nrow and the distance measurement in all rows is completed, the measurement process ends.

[0074] Through the above distance measurement processing, a two-dimensional array-shaped distance measurement result similar to the image information can be obtained.

[0075] FIG. 13 shows, respectively, for a reference light and a signal light, the TDC results for a predetermined number N total FIG. 13 shows an example of a reference light histogram 1301 and a signal light histogram 1302 obtained by storing the TDC results for the reference light and the TDC results for the signal light in a histogram circuit. Time 1303 indicates the time when the light emission instruction signal is output from the overall control unit 140. The time 1304 from time 1303 to the peak time of the reference light histogram 1301 is the reference light time from when the light emission instruction signal is output until the light emitting element actually emits light. Also, the time from time 1303 to the peak time of the signal light histogram 1302 is the signal light time 1305 from when the light emission instruction signal is output until the signal light from the object is received. By subtracting the reference light time 1304 from the signal light time 1305 in step 1212 of FIG. 12, high-precision ToF, that is, distance information to the object, can be obtained regardless of the variation in the light emission delay time of the light emitting element from the light emission instruction.

[0076] As described above, in this embodiment, the light emitting elements in the light emitting element array 111 are caused to emit light at different times for each row. Also, a reflection structure portion 152 is provided on the beam splitter 150 for guiding the reference light to a light receiving element in a row different from the row of the light receiving elements corresponding to the row of the light emitting element that has emitted light among the light receiving element array 121 (the light receiving elements that receive the signal light). As a result, the signal light and the reference light can be received by the light receiving elements in the row corresponding to the row of the light emitting element that has emitted light among the light receiving element array 121 and the light receiving elements in the adjacent row, respectively. Thereby, high-precision distance measurement with reduced influence of the light emission delay of the light emitting element can be performed in a small-sized distance measurement device.

[0077] Note that the light receiving element that receives the reference light does not necessarily have to belong to the adjacent row of the light receiving element that receives the signal light. That is, the reflection structure portion 152 only needs to reflect the reference light so that the reference light is guided to a light receiving element different from the light receiving element that receives the signal light.

[0078] In the light-emitting element array, it is not always necessary to sequentially emit light from the light-emitting elements for each row. Instead, the light-emitting elements may be sequentially emitted for every two or more rows. That is, the light-emitting elements may be sequentially emitted for every predetermined number of rows.

Example

[0079] FIG. 14(A) schematically shows a beam splitter 150, a light-emitting element array 111, a light-receiving element array 121, and an imaging lens 130 in Example 2. Also in this example, the light-emitting element array 111 and the light-receiving element array 121 are in a conjugate relationship via the half mirror 151 of the beam splitter 150, and each light-emitting element and each light-receiving element are also in a one-to-one conjugate relationship. The row numbers in the light-emitting element array 111 and the light-receiving element array 121 are the same as those described in FIG. 11(A).

[0080] In this example, the reflection structure portion 152' provided in the beam splitter 150 is different from the reflection structure portion 152 in Example 1. As described with reference to FIGS. 11(B) and 11(C), the reflection structure portion 152 in Example 1 has a structure that reflects the reference light 1112(1113) incident from the half mirror 151 to the reflection structure portion 152 so as to shift it by one row. On the other hand, the reflection structure portion 152' in Example 2 has a structure that does not cause a shift of one row in the reference light. The reflection structure portion 152' is provided with a structure on its surface that transmits, absorbs, or both, such that the reflectance of light in a predetermined wavelength range including the wavelength of light from the light-emitting element is lower than the reflectance of light in other wavelength ranges. This surface structure may be a structure in which dielectrics having different refractive indices are laminated, or a structure using an absorbing material such as metal.

[0081] As shown in FIG. 14(B), the light 1410 emitted from the light-emitting element (first light-receiving element) of row number 1 in the light-emitting element array 111 is separated into the irradiated light 1411 reflected by the half mirror 151 and the reference light 1412 transmitted through the half mirror 151. The reference light 1412 is incident on the reflection structure portion 152'. The reference light 1413 reflected by the reflection structure portion 152' is incident on the half mirror 151 in the same optical path as the reference light 1412 incident on the reflection structure portion 152', as shown in FIG. 14(C), and is reflected by the half mirror 151 and travels toward the light-receiving element array 121. As a result, as can be seen from FIGS. 14(C) and (D), the reference light 1413 is incident on the light-receiving element (first light-receiving element) in a conjugate relationship with the light-emitting light-emitting element. That is, the reference light 1413 is incident on the same light-receiving element as the light-receiving element on which the signal light 1414 from the object is incident.

[0082] In this embodiment, in step 1202 of the flowchart shown in FIG. 12, the overall control unit 140 causes the row selection circuit 125 to select only the row of the pixel 301 corresponding to the row counter j through the measurement control unit 124. Thereby, it is set such that the pixel output signals from the pixels 301 in the row that receives the signal light and the reference light are output to the TDC array unit 122 via the pixel output line 304.

[0083] FIG. 15 shows an example of a reference light / signal light histogram obtained by storing the TDC results for each of the predetermined number N total in the histogram circuit. The time 1503 indicates the time when the light emission instruction signal is output from the overall control unit 140. In Example 1 (FIG. 13), the reference light histogram 1301 and the signal light histogram 1302 were obtained using the TDC results from the pixels 301 in the row in a conjugate relationship with the row of the light-emitting light-emitting element and the adjacent rows. In contrast, in this embodiment, a reference light / signal light histogram 1500 in which the reference light histogram and the signal light histogram are combined is obtained using only the TDC results from the pixels 301 in the row in a conjugate relationship with the row of the light-emitting light-emitting element.

[0084] The reference light / signal light histogram 1500 includes two peaks. The peak 1501 with a shorter time from time 1503 is the peak of the reference light, and the peak 1502 with a longer time from time 1503 is the peak of the signal light. The time 1504 from time 1503 to the time of the reference light peak 1501 is the reference light time from when the light emission instruction signal is output until the light emitting element actually emits light. Also, the time from time 1503 to the time of the signal light peak 1502 is the signal light time 1505 from when the light emission instruction signal is output until the signal light from the object is received. By subtracting the reference light time 1504 from the signal light time 1505 in step 1212 of FIG. 12, high-precision ToF, that is, distance information to the object, can be obtained regardless of the variation in the light emission delay time of the light emitting element from the light emission instruction.

[0085] As described above, in this embodiment, the light emitting elements in the light emitting element array 111 emit light at different times for each row. Also, the beam splitter 150 is provided with a reflection structure portion 152' for guiding the reference light to the light receiving elements in the row corresponding to the row of the light emitting element that has emitted light among the light receiving element array 121. As a result, the signal light and the reference light can be received with a time difference by the light receiving elements in the row corresponding to the row of the light emitting element that has emitted light among the light receiving element array 121. Thereby, high-precision distance measurement with reduced influence of the light emission delay of the light emitting element can be performed in a small-sized distance measurement device.

[0086] In addition, in each of the above embodiments, the case where the reflection structure portions 152 and 152' as the reflection means are provided integrally with the beam splitter 150 has been described. However, the same reflection means may be provided separately from the beam splitter. In this case, by arranging the reflection means in contact with or close to the beam splitter, the distance measurement device can be miniaturized.

[0087] The distance measurement device (measurement device) described in the above embodiments can be included in a processing device that performs processing using distance information (information about an object) obtained from the distance measurement device, which is mounted on various devices such as an imaging device such as a camera, an electronic device such as a smartphone, and a moving device such as an automobile. For example, in an imaging device or an electronic device, the processing device can perform focus control (AF) using distance data and generate a distance map within the angle of view as described above. In a moving device, a part of an ECU (Electronic Control Unit) that measures the inter-vehicle distance from a preceding vehicle, controls the brakes and steering wheel, and outputs warnings by detecting obstacles can be configured by the processing device.

[0088] The above embodiments include the following configurations.

[0089] [Configuration 1] A light emitting element array including a plurality of light emitting elements, A light receiving element array including a plurality of light receiving elements, An optical system, A separation unit that separates the light from the light emitting element array into irradiation light that irradiates an object through the optical system and reference light that is guided to the light receiving element array, and a light separation element that guides signal light that is reflected by the object and incident through the optical system to the light receiving element array through the separation unit, A measurement device having a processing means for acquiring information about an object from a first time from a light emission instruction to the light emitting element array to reception of the reference light in the light receiving element array and a second time from the light emission instruction to reception of the signal light in the light receiving element array, Having a reflection means for reflecting the reference light from the separation unit back to the separation unit, A measurement device characterized in that the reference light from the reflection means is guided to the light receiving element array through the separation unit. [Configuration 2] The measurement device according to Configuration 1, characterized in that the reflection means is provided integrally with the light separation element. [Configuration 3] Of the irradiation light from the first light-emitting element in the light-emitting element array, the reference light reflected by the object is guided to a first light-receiving element corresponding to the first light-emitting element in the light-receiving element array through the separation unit, The measurement apparatus according to configuration 1 or 2, wherein the reflection means reflects the reference light from the first light-emitting element so that the reference light is guided to a second light-receiving element different from the first light-receiving element in the light-receiving element array through the separation unit. [Configuration 4] In the light-emitting element array and the light-receiving element array, the plurality of light-emitting elements and the plurality of light-receiving elements are two-dimensionally arranged such that the plurality of light-emitting elements and the plurality of light-receiving elements respectively form a plurality of light-emitting element rows and a plurality of light-receiving element rows, In the light-emitting element array, simultaneous emission of a plurality of the first light-emitting elements belonging to the same light-emitting element row is sequentially performed for every predetermined number of light-emitting element rows, The measurement apparatus according to configuration 3, wherein the reflection means reflects the reference light from the plurality of first light-emitting elements so that the reference light is guided to a plurality of second light-receiving elements belonging to a light-receiving element row different from the light-receiving element row corresponding to the light-emitting element row to which the plurality of first light-emitting elements belong in the light-receiving element array through the separation unit. [Configuration 5] The measurement apparatus according to configuration 3 or 4, wherein the reflection means has a structure that shifts the reference light reflected by the reflection means with respect to the reference light incident on the reflection means. [Configuration 6] Of the irradiation light from the first light-emitting element in the light-emitting element array, the reference light reflected by the object is guided to a first light-receiving element corresponding to the first light-emitting element in the light-receiving element array through the separation unit, The measurement apparatus according to configuration 1 or 2, wherein the reflection means reflects the reference light from the first light-emitting element so that the reference light is guided to the first light-receiving element through the separation unit. [Configuration 7] In the light-emitting element array and the light-receiving element array, the plurality of light-emitting elements and the plurality of light-receiving elements are two-dimensionally arranged such that the plurality of light-emitting elements and the plurality of light-receiving elements respectively form a plurality of light-emitting element rows and a plurality of light-receiving element rows. In the light-emitting element array, simultaneous emission of the plurality of first light-emitting elements belonging to the same light-emitting element row is sequentially performed for every predetermined number of light-emitting element rows. The reflection means reflects the reference light from the plurality of first light-emitting elements so that the reference light is guided to a plurality of the second light-receiving elements belonging to a light-receiving element row corresponding to the light-emitting element row to which the plurality of first light-emitting elements in the light-receiving element array belong via the separation unit. The measuring device according to Configuration 6. [Configuration 8] In the measuring device according to any one of Configurations 1 to 7, each light-emitting element in the light-emitting element array and each light-receiving element in the light-receiving element array are associated with each other by being arranged at positions optically conjugate to each other with respect to the separation unit. [Configuration 9] The reflection means has a structure that performs at least one of transmission and absorption on light in a wavelength range different from the wavelength range including the wavelength of the reference light. The measuring device according to any one of Configurations 1 to 8. [Configuration 10] The processing means acquires distance information as information about the object using the flight time obtained by subtracting the first time from the second time. The measuring device according to any one of Configurations 1 to 9. [Configuration 11] Including the measuring device according to any one of Configurations 1 to 10. A processing device characterized by performing processing using the information about the object.

[0090] (Other embodiments) The present invention can also be realized by supplying a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be realized by a circuit (for example, an ASIC) that implements one or more functions.

[0091] Each of the embodiments described above is merely a representative example, and various modifications and changes can be made to each embodiment when implementing the present invention.

Description of Reference Numerals

[0092] 111 Light-emitting element array 121 Light-receiving element array 140 Overall control unit 150 Beam splitter 151 Half mirror 152 Reflection structure unit 1111 Irradiation light 1112, 1113 Reference light 1114 Signal light

Claims

1. A light-emitting element array including a plurality of light-emitting elements, A light-receiving element array including a plurality of light-receiving elements, An optical system, A separation unit that separates light from the light-emitting element array into irradiation light that irradiates an object through the optical system and reference light that is guided to the light-receiving element array, and a light separation element that guides signal light that is reflected by the object and enters through the optical system to the light-receiving element array through the separation unit, A measuring device having a processing unit that acquires information about the object using a first time from a light emission instruction to the light-emitting element array to reception of the reference light in the light-receiving element array and a second time from the light emission instruction to reception of the signal light in the light-receiving element array, having a reflection unit that reflects the reference light from the separation unit back to the separation unit, The measuring device characterized in that the reference light from the reflection unit is guided to the light-receiving element array through the separation unit.

2. The measuring device according to claim 1, characterized in that the reflection unit is provided integrally with the light separation element.

3. Among the irradiation light from the first light-emitting element in the light-emitting element array, the reference light reflected by the object is guided to a first light-receiving element corresponding to the first light-emitting element in the light-receiving element array through the separation unit, The measuring device according to claim 1, characterized in that the reflection unit reflects the reference light from the first light-emitting element so that the reference light is guided to a second light-receiving element different from the first light-receiving element in the light-receiving element array through the separation unit.

4. In the light-emitting element array and the light-receiving element array, the plurality of light-emitting elements and the plurality of light-receiving elements are two-dimensionally arranged so as to form a plurality of light-emitting element rows and a plurality of light-receiving element rows, respectively, In the light-emitting element array, simultaneous emission of a plurality of the first light-emitting elements belonging to the same light-emitting element row is sequentially performed for every predetermined number of light-emitting element rows. The measurement device according to claim 3, wherein the reflecting means reflects the reference light from the plurality of first light-emitting elements so that the reference light is guided to a plurality of the second light-receiving elements belonging to a light-receiving element row different from the light-receiving element row corresponding to the light-emitting element row to which the plurality of first light-emitting elements in the light-receiving element array belong via the separating unit.

5. The measurement device according to claim 3, wherein the reflecting means has a structure that shifts the reference light reflected by the reflecting means with respect to the reference light incident on the reflecting means.

6. Of the irradiation light from the first light-emitting element in the light-emitting element array, the reference light reflected by the object is guided to a first light-receiving element corresponding to the first light-emitting element in the light-receiving element array via the separating unit. The measurement device according to claim 1, wherein the reflecting means reflects the reference light from the first light-emitting element so that the reference light is guided to the first light-receiving element via the separating unit.

7. In the light-emitting element array and the light-receiving element array, the plurality of light-emitting elements and the plurality of light-receiving elements are two-dimensionally arranged such that the plurality of light-emitting elements and the plurality of light-receiving elements respectively form a plurality of light-emitting element rows and a plurality of light-receiving element rows. In the light-emitting element array, simultaneous emission of a plurality of the first light-emitting elements belonging to the same light-emitting element row is sequentially performed for every predetermined number of light-emitting element rows. The measurement device according to claim 6, wherein the reflecting means reflects the reference light from the plurality of first light-emitting elements so that the reference light is guided to a plurality of the second light-receiving elements belonging to the light-receiving element row corresponding to the light-emitting element row to which the plurality of first light-emitting elements in the light-receiving element array belong via the separating unit.

8. The measuring device according to claim 1, characterized in that each light-emitting element in the light-emitting element array and each light-receiving element in the light-receiving element array are associated with each other by being arranged at positions optically conjugate to each other with respect to the separation unit.

9. The measuring device according to claim 1, characterized in that the reflection means has a structure that performs at least one of transmission and absorption on light in a wavelength range different from the wavelength range including the wavelength of the reference light.

10. The measuring device according to claim 1, characterized in that the processing means acquires distance information as information about the object using the flight time obtained by subtracting the first time from the second time.

11. A processing device comprising the measuring device according to any one of claims 1 to 10, and performing processing using the information about the object.

12. A light-emitting element array including a plurality of light-emitting elements, A light-receiving element array including a plurality of light-receiving elements, An optical system, having a separation unit that separates light from the light-emitting element array into irradiation light irradiated onto an object through the optical system and reference light guided to the light-receiving element array, and using a light separation element that guides signal light reflected by the object and incident through the optical system to the light-receiving element array through the separation unit, providing reflection means for reflecting the reference light from the separation unit back to the separation unit, and guiding the reference light from the reflection means to the light-receiving element array through the separation unit, A measurement method characterized by acquiring information about the object using a first time from a light emission instruction to the light-emitting element array to reception of the reference light in the light-receiving element array and a second time from the light emission instruction to reception of the signal light in the light-receiving element array.

Images