Distance measuring device and distance measuring method

Abstract

To provide a distance measuring device capable of measuring a longer distance than before.SOLUTION: A distance measuring device 10 is a TOF method distance measuring device that comprises: a pulse generation part 107; a control part 106 controlling the pulse generation part 107 according to n types of exposure patterns; a light source part 102; a solid-state imaging part 105; and a distance calculation part 108. The n types of exposure patterns include in a plurality of unit times for any two adjacent unit times, (1) an exposure pattern in which exposure is permitted in both two unit times, (2) an exposure pattern in which exposure is permitted in one of the two unit times and inhibited in the other one thereof, and (3) an exposure pattern in which exposure is inhibited in both two unit times. The distance calculation part 108 generates for each pixel, on the basis of magnitude relation between the n types of signal values, information indicative of a distance section corresponding to reflected light from among a plurality of distance sections as distance information.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a distance measuring device and a distance measuring method, and particularly to a distance measuring device and a distance measuring method that measure the distance to an object by using the flight time of light traveling to and from the object.

Background Art

[0002] Conventionally, a TOF (time of flight) type distance measuring device that measures distance by using the flight time of light traveling to and from an object is known (see, for example, Patent Document 1).

[0003] In Patent Document 1, the distance measurement range is extended by using at least three exposure patterns indicating exposure permission or exposure prohibition for each of a plurality of unit times corresponding to a plurality of distance intervals obtained by dividing the distance measurement range.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, there is a problem that it cannot meet the demand for further extending the distance measurement range. For example, according to Patent Document 1, when three exposure patterns are used, the measurable distance is the distance corresponding to four unit times, and there is a problem that it cannot be said to be a sufficiently long distance measurement range.

[0006] Therefore, an object of the present disclosure is to provide a distance measuring device and a distance measuring method capable of extending the distance measurement range more than before.

Means for Solving the Problems

[0007] To achieve the above objective, a ranging device according to one embodiment of the present disclosure is a ranging device that measures the distance to an object by utilizing the time of flight of light to and from the object, comprising: a pulse generation unit that generates an emission pulse that indicates the timing of light irradiation and an exposure pulse that indicates the timing of exposure of reflected light; a control unit that controls the pulse generation unit according to n types of exposure patterns, each of which n is an integer of 3 or more, indicating exposure permission or exposure prohibition for each of a plurality of unit time corresponding to a plurality of distance intervals that divide the ranging range; a light source unit that irradiates light according to the emission pulse; a solid-state imaging unit having a plurality of pixels that takes images according to the exposure pulse; and n types corresponding to the n types of exposure patterns obtained from the solid-state imaging unit The solid imaging unit includes a distance calculation unit that calculates distance information based on signal values, and the solid imaging unit acquires the n types of signal values ​​for each pixel in a frame period based on the reflected light, and the n types of exposure patterns include an exposure pattern in which exposure is permitted for any two adjacent unit times in a plurality of unit times, an exposure pattern in which exposure is permitted for one of the two unit times and prohibited for the other, and an exposure pattern in which exposure is prohibited for both of the two unit times, and the distance calculation unit generates information for each pixel, indicating the distance interval among the plurality of distance intervals that corresponds to the reflected light, based on the relative magnitudes of the n types of signal values, as the distance information. The pulse generation unit generates the light emission pulse and the exposure pulse in such a cyclical manner that it repeats one of the n types of exposure patterns multiple times, then another exposure pattern multiple times, and then the remaining one exposure pattern multiple times, thereby repeating all of the n types of exposure patterns multiple times.

[0008] Furthermore, in order to achieve the above objective, a distance measuring method according to one embodiment of the present disclosure is a distance measuring method using a distance measuring device that measures the distance to an object using the time of flight of light to and from the object, wherein the distance measuring device comprises a pulse generation unit that generates a light emission pulse that indicates the timing of light irradiation and an exposure pulse that indicates the timing of exposure of reflected light, a light source unit that irradiates light according to the light emission pulse, and a solid-state imaging unit having a plurality of pixels that takes images according to the exposure pulse, and the distance measuring method comprises a control step of controlling the pulse generation unit according to n types of exposure patterns, where n is an integer of 3 or more, that indicate exposure permission or exposure prohibition for each of a plurality of unit time corresponding to a plurality of distance intervals that divide the distance measuring range, and the n types of exposure pulses obtained from the solid-state imaging unit The solid imaging unit includes a distance calculation step of calculating distance information based on n types of signal values ​​corresponding to a turn, wherein the solid imaging unit acquires the n types of signal values ​​for each pixel in a frame period based on the reflected light, and the n types of exposure patterns include an exposure pattern in which exposure is permitted for any two adjacent unit times in the plurality of unit times, an exposure pattern in which exposure is permitted for one of the two unit times and prohibited for the other, and an exposure pattern in which exposure is prohibited for both of the two unit times, and in the distance calculation step, based on the relative magnitudes of the n types of signal values, information indicating the distance interval corresponding to the reflected light from the plurality of distance intervals is generated as distance information for each pixel. The pulse generation unit generates the light emission pulse and the exposure pulse in such a cyclical manner that it repeats one of the n types of exposure patterns multiple times, then another exposure pattern multiple times, and then the remaining one exposure pattern multiple times, thereby repeating all of the n types of exposure patterns multiple times. [Effects of the Invention]

[0009] This disclosure provides a distance measuring device and a distance measuring method that can extend the distance measuring range compared to conventional methods. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a block diagram showing the configuration of a distance measuring device according to an embodiment. [Figure 2] Figure 2 is a circuit diagram showing the pixel configuration of the solid-state imaging unit shown in Figure 1. [Figure 3]Figure 3 is a block diagram showing the detailed configuration of the solid-state imaging unit shown in Figure 1. [Figure 4] Figure 4 is a table showing an example of three types of exposure patterns using the rangefinder shown in Figure 1. [Figure 5] Figure 5 shows the light emission and exposure drive timing of the solid-state imaging unit to realize the three types of exposure patterns shown in Figure 4. [Figure 6] Figure 6 is a circuit block diagram showing the detailed configuration of the distance calculation unit shown in Figure 1. [Figure 7] Figure 7 is a diagram illustrating the processing of the distance calculation unit shown in Figure 6. [Figure 8] Figure 8 is a flowchart showing the operation of the distance measuring device according to the embodiment. [Figure 9] Figure 9 is a table showing an example of three types of exposure patterns using a distance measuring device according to a modified example 1 of the embodiment. [Figure 10] Figure 10 shows the light emission and exposure drive timing of the solid-state imaging unit to realize three types of exposure patterns by the distance measuring device according to a modified example 2 of the embodiment. [Figure 11] Figure 11 shows the light emission and exposure drive timing of the solid-state imaging unit to realize three types of exposure patterns using the distance measuring device according to the modified example of Modification Example 2. [Figure 12] Figure 12 is a diagram showing a table indicating the drive timing of light emission and exposure by the distance measuring device according to the third modified embodiment. [Figure 13] Figure 13 is a table showing an example of four types of exposure patterns using the rangefinder shown in Figure 1. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that all of the embodiments described below are specific examples of the present disclosure. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, order of steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Also, each drawing is not necessarily drawn precisely. In each drawing, substantially the same configuration is denoted by the same reference numeral, and duplicate descriptions are omitted or simplified. Further, "connection" means electrical connection, and includes not only the case where two circuit elements are directly connected, but also the case where two circuit elements are indirectly connected with other circuit elements inserted between the two circuit elements.

[0012] FIG. 1 is a block diagram showing the configuration of a distance measuring device 10 according to an embodiment. An imaging space 100 is a space including the distance measuring device 10, an object 101 to be distance measured, and a background light source 140. The object 101 is an object to be distance measured, and may be not only a person but also an object. The distance measuring device 10 is a distance measuring device using the TOF method, and includes a light source unit 102, an optical lens 103, an optical filter 104, a solid-state imaging unit 105, a control unit 106, a pulse generation unit 107, and a distance calculation unit 108.

[0013] The optical lens 103 and the optical filter 104 are an optical system that guides reflected light from the object 101 to the solid-state imaging unit 105. The optical filter 104 is, for example, an infrared transmission filter.

[0014] The pulse generation unit 107 is a circuit that generates a light emission pulse 120 for instructing the light irradiation timing and exposure pulses 121 to 123 for instructing the exposure timing of the reflected light 111.

[0015] The control unit 106 is a circuit that controls the pulse generation unit 107, the solid-state imaging unit 105, and the distance calculation unit 108 via a control bus. For example, the control unit 106 controls the pulse generation unit 107 according to n types (in this embodiment, three types) of exposure patterns, where n is an integer of 3 or more, indicating exposure permission or exposure prohibition for each of a plurality of unit times corresponding to a plurality of distance intervals obtained by dividing the distance measurement range.

[0016] Here, the three types of exposure patterns are composed of the repetition of the patterns in seven unit times. Among the seven unit times, for any two adjacent unit times, (1) an exposure pattern that permits exposure in both of the two unit times, (2) an exposure pattern that permits exposure in one of the two unit times and prohibits exposure in the other, and (3) an exposure pattern that prohibits exposure in both of the two unit times are included.

[0017] The light source unit 102 is a light source that emits irradiation light 110 according to the emission pulse 120, and is, for example, an LED or a laser element that emits infrared light.

[0018] The solid-state imaging unit 105 has a plurality of pixels for imaging according to the exposure pulses 121 to 123. The solid-state imaging unit 105 acquires, for each pixel, three types of signal values (signals indicating these three types of signal values are also referred to as "packets 0 to 2") corresponding to the three types of exposure patterns in one frame period based on the reflected light 111, and outputs them as an imaging signal 130 to the distance calculation unit 108. Note that the reflected light 111 includes not only the reflected light of the irradiation light 110 emitted from the light source unit 102 but also the reflected light of the background light 141 from the background light source 140.

[0019] The distance calculation unit 108 is a circuit that calculates distance information 131 based on the three types of signal values ("packets 0 to 2") obtained from the solid-state imaging unit 105 and outputs it to the outside. At this time, the distance calculation unit 108 generates, for each pixel, information indicating the distance interval corresponding to the reflected light among a plurality of distance intervals as the distance information 131 based on the magnitude relationship between the three types of signal values. Furthermore, the distance calculation unit 108 also calculates a distance obtained by subdividing the distance interval from the three types of signal values and outputs it to the outside as the distance information 131.

[0020] The control unit 106, pulse generation unit 107, and distance calculation unit 108 are implemented by combining, for example, a memory for storing programs, a CPU (Central Processing Unit), an FPGA (Field Programmable Grid Array), a DSP (Digital Signal Processor), an AFE (Analog Front End), etc.

[0021] Figure 2 is a circuit diagram showing the configuration of a pixel 200 in the solid-state imaging unit 105 shown in Figure 1. The pixel 200 comprises a photoelectric conversion unit 201, two drains 210, three signal charge storage units called FDA (Floating Diffusion Amplifier) ​​211-213, three source follower circuits 221-223, and three output selection transistors 231-233. The pixel 200 also has gate electrodes 214-216 between each of the drains 210 and FDA 211-213 and the photoelectric conversion unit 201, and a gate electrode 217 between the drain 210 and the photoelectric conversion unit 201.

[0022] The photoelectric conversion unit 201 is composed of a photodiode (PD) that receives reflected light 111 and performs photoelectric conversion.

[0023] The drain 210 discharges the signal charge that has been photoelectrically converted in the photoelectric conversion unit 201.

[0024] Each of FDA211-213 stores the signal charge converted photoelectrically by the photoelectric conversion unit 201.

[0025] Source follower circuits 221 to 223 each output a voltage corresponding to the signal charge amount of FDA 211 to 213.

[0026] When the output enable signal 240 is at a high level, the output select transistors 231 to 233 output the output voltages of the source follower circuits 221 to 223 as pixel signals 241 to 243, respectively.

[0027] The operation of the pixel 200 is as follows: Exposure pulses 121 to 123 from the pulse generation unit 107 are applied to each of the gate electrodes 214 to 216. When the exposure pulses 121 to 123 reach a high level, the signal charge converted photoelectrically by the photoelectric conversion unit 201 is stored in FDA 211 to 213, respectively. However, a discharge pulse 127 from the pulse generation unit 107 is applied to the gate electrode 217. When the discharge pulse 127 reaches a high level, the signal charge converted photoelectrically by the photoelectric conversion unit 201 is discharged to the drain 210. Therefore, when all exposure pulses 121 to 123 are at a low level, and the discharge pulse 127 is at a high level, the signal charge photoelectrically converted by the photoelectric conversion unit 201 is discharged from the drain 210. When only one of the exposure pulses 121 to 123 is at a high level, and the discharge pulse 127 is at a low level, the signal charge photoelectrically converted by the photoelectric conversion unit 201 is stored in the FDA corresponding to the exposure pulse that is at a high level. Three types of imaging are performed for each pixel, corresponding to each of the exposure pulses 121 to 123.

[0028] In FDA211~213, signal charge accumulates, generating a voltage corresponding to the amount of signal charge. When the output enable signal 240 reaches a high level, the voltages generated in FDA211~213 pass through source follower circuits 221~223 and output selection transistors 231~233, respectively, and are output from pixel 200 as pixel signals 241~243.

[0029] Figure 3 is a block diagram showing the detailed configuration of the solid-state imaging unit 105 shown in Figure 1. The solid-state imaging unit 105 comprises a plurality of pixels 200 arranged in two dimensions, a row selection unit 372, a column AD 370, and a shift register 371. The pixels 200 are arranged in two dimensions, with X pixels horizontally and Y pixels vertically. For example, X=320 and Y=240.

[0030] Pixels 200 with horizontally aligned pixel addresses 11 to 1X are supplied with an output enable signal 240 from the row selection unit 372 via the row selection signal line 300. Similarly, pixels 200 with horizontally aligned pixel addresses 21 to 2X, 31 to 3X, ..., and Y1 to YX are supplied with an output enable signal 240 from the row selection unit 372 via the row selection signal lines 301, 302, ..., 303, respectively.

[0031] Pixel signals 241-243 output from pixels 200 with vertically aligned pixel addresses Y1-11 are input to column AD370 via common vertical signal lines 311-313, respectively. Similarly, pixel signals 241-243 output from pixels 200 with vertically aligned pixel addresses Y2-12 and YX-1X are input to column AD370 via common vertical signal lines 321-323 and 331-333, respectively.

[0032] The output signal from column AD370 is input to shift register 371, and the imaging signal 130 is output from shift register 371.

[0033] The readout operation of the solid-state imaging unit 105 is as follows. Note that the readout operation is the same as that of a typical CMOS image sensor with three times the horizontal pixel count.

[0034] In other words, when the row selection unit 372 causes only row selection signal line 300 of the row selection signal lines 300 to 303 to reach a high level, pixel signals 241 to 243 from pixel 200 at pixel address 11 are input to column AD370 via vertical signal lines 311 to 313, pixel signals 241 to 243 from pixel 200 at pixel address 12 are input to column AD370 via vertical signal lines 321 to 323, and pixel signals 241 to 243 from pixel 200 at pixel address 1X are input to column AD370 via vertical signal lines 331 to 333.

[0035] Similarly, when only row selection signal line 301 of row selection signal lines 300 to 303 is at a high level, pixel signals 241 to 243 from pixels 200 with pixel addresses 21 to 2X are input to column AD370. When only row selection signal line 302 of row selection signal lines 300 to 303 is at a high level, pixel signals 241 to 243 from pixels 200 with pixel addresses 31 to 3X are input to column AD370. When only row selection signal line 303 of row selection signal lines 300 to 303 is at a high level, pixel signals 241 to 243 from pixels 200 with pixel addresses Y1 to YX are input to column AD370.

[0036] Column AD370 performs analog-to-digital (AD) conversion on the input pixel signals 241-243 for X pixels and outputs them to the shift register 371. The shift register 371 shifts the input signal values ​​for X pixels one by one and outputs them to the distance calculation unit 108 as the imaging signal 130.

[0037] Figure 4 is a table showing an example of three types of exposure patterns by the distance measuring device 10 shown in Figure 1. In Figure 4, "distance measuring range" refers to multiple distance sections 1 to 7 (also called ranges 1 to 7) that divide the distance measuring range. Each of the distance sections 1 to 7 is also a corresponding unit time 1 to 7. One range (i.e., one unit time) corresponds to the emission time of the emission pulse 120.

[0038] The "1" and "0" in the lines labeled "Emission Pulse" and "Emission Pattern" indicate that, for the corresponding unit of time, the emission pulse 120 will enable or disable emission. In other words, the light source unit 102 will emit light due to the emission pulse 120 for only a unit of time of 1.

[0039] In the "Exposure Pulse" row, "Packets 0-2" represent signals indicating the signal values ​​obtained for each of the three exposure patterns, that is, the signal charges obtained in FDA211-213.

[0040] The "1" and "0" in the lines labeled "First Exposure Pattern," "Second Exposure Pattern," and "Third Exposure Pattern" indicate that, within the corresponding unit of time, the corresponding exposure pulses 121, 122, and 123 indicate exposure permission and exposure prohibition, respectively.

[0041] In other words, in the first exposure pattern, exposure pulse 121 indicates exposure permission at unit time 1 and 2, exposure prohibition at unit time 3 to 5, and exposure permission at unit time 6 and 7. Packet 0 is the signal indicating the signal charge obtained by the solid imaging unit 105 using this first exposure pattern. Similarly, in the second exposure pattern, exposure pulse 122 indicates exposure prohibition at unit time 1, exposure permission at unit time 2 to 4, and exposure prohibition at unit time 5 to 7. Packet 1 is the signal indicating the signal charge obtained by the solid imaging unit 105 using this second exposure pattern. Similarly, in the third exposure pattern, exposure pulse 123 indicates exposure prohibition at unit time 1 to 3, exposure permission at unit time 4 to 6, and exposure prohibition at unit time 7. Packet 2 is the signal indicating the signal charge obtained by the solid imaging unit 105 using this third exposure pattern. Thus, the three types of exposure patterns indicate the timing (phase) of exposure by exposure pulses 121 to 123 for a single light emission.

[0042] The three types of exposure patterns have the following relationships within unit time 1 to 7: (1) an exposure pattern in which exposure is permitted in both of the two adjacent unit time periods, (2) an exposure pattern in which exposure is permitted in one of the two unit time periods and prohibited in the other, and (3) an exposure pattern in which exposure is prohibited in both of the two unit time periods.

[0043] The "Range Determination / Packet Value / Sorting Result" shown in the lower half of the table in Figure 4 indicates the sorting result of packets 0-2 when sorted from the largest signal value to the smallest for each of two adjacent distance intervals in distance intervals 1-7.

[0044] Specifically, if reflected light is detected by pixel 200 in a time interval of 1 to 2 units, then in this interval, packet 0 will show the largest signal value because it represents the signal charge obtained from an exposure pattern where exposure is permitted for two units of time; packet 1 will show the next largest signal value because it represents the signal charge obtained from an exposure pattern where exposure is permitted for only one unit of time; and packet 0 will show the smallest signal value because it represents the signal charge obtained from an exposure pattern where exposure is prohibited for two units of time.

[0045] Similarly, if reflected light is detected by pixel 200 in an interval of 2 to 3 units of time, in this interval, packet 1 shows the largest signal value because it represents the signal charge obtained from an exposure pattern where exposure is permitted for two units of time, packet 0 shows the next largest signal value because it represents the signal charge obtained from an exposure pattern where exposure is permitted for only one unit of time, and packet 2 shows the smallest signal value because it represents the signal charge obtained from an exposure pattern where exposure is prohibited for two units of time.

[0046] Similarly, if the reflected light is detected by pixel 200 in a unit time interval of 3 to 4, the packets will be 1, 2, and 0 in descending order of signal value; if the reflected light is detected by pixel 200 in a unit time interval of 4 to 5, the packets will be 2, 1, and 0 in descending order of signal value; if the reflected light is detected by pixel 200 in a unit time interval of 5 to 6, the packets will be 2, 0, and 1 in descending order of signal value; and if the reflected light is detected by pixel 200 in a unit time interval of 6 to 7, the packets will be 0, 2, and 1 in descending order of signal value.

[0047] Thus, the sorting result (order of packets) is unique, depending on the position (i.e., timing) of the reflected light in the unit time units 1 to 7. The distance measuring device 10 uses this to determine which of the seven distance intervals the distance to the object 101 belongs to (i.e., range determination).

[0048] In addition, the distance measuring device in Patent Document 1 also uses three types of exposure patterns, but since all of them are monotonous exposure patterns, the range in which distance can be measured is limited to four ranges. According to the distance measuring device 10 of this disclosure, the three types of exposure patterns have a relationship in which, for any two adjacent unit time periods within seven unit time periods, (1) an exposure pattern in which exposure is permitted in both of the two unit time periods, (2) an exposure pattern in which exposure is permitted in one of the two unit time periods and prohibited in the other, and (3) an exposure pattern in which exposure is prohibited in both of the two unit time periods. Therefore, the range in which distance can be measured is seven ranges, and the distance measurement distance is extended compared to Patent Document 1.

[0049] Figure 5 shows the drive timing of light emission and exposure of the solid-state imaging unit 105 to realize the three types of exposure patterns shown in Figure 4. Each frame consists of L sets (for example, 12 sets) of light emission exposure periods 410, which consist of a first light emission exposure period 411, a second light emission exposure period 412, and a third light emission exposure period 413, and a signal output period 414.

[0050] The first light emission exposure period 411 is a period during which the first drive pattern 411a corresponding to the first exposure pattern is driven continuously M times (for example, 300 times). Specifically, as shown by the timing of the thick solid line in the first drive pattern 411a in Figure 5, the control unit 106 controls the pulse generation unit 107 to generate light emission pulses 120 and exposure pulses 121, thereby causing the light source unit 102 to emit light at unit time 1 of the unit time 1 to 7, and exposing the solid imaging unit 105 at unit time 1, 2, 6 and 7 of the unit time 1 to 7, thereby accumulating signal charge in FDA211. This drive (first drive pattern 411a) is repeated M times.

[0051] The second light emission exposure period 412 is a period during which the second drive pattern 412a corresponding to the second exposure pattern is driven M times continuously. Specifically, as shown by the timing of the thick solid line in the second drive pattern 412a in Figure 5, the control unit 106 controls the pulse generation unit 107 to generate light emission pulses 120 and exposure pulses 122, thereby causing the light source unit 102 to emit light during unit time 1 of the unit time 1 to 7, and exposing the solid imaging unit 105 during unit time 2 to 4 of the unit time 1 to 7, thereby accumulating signal charge in FDA212. This drive (second drive pattern 412a) is repeated M times.

[0052] The third light emission exposure period 413 is a period during which the third drive pattern 413a corresponding to the third exposure pattern is driven M times continuously. Specifically, as shown by the timing of the thick solid line in the third drive pattern 413a in Figure 5, the control unit 106 controls the pulse generation unit 107 to generate light emission pulses 120 and exposure pulses 123, thereby causing the light source unit 102 to emit light at unit time 1 of the unit time 1 to 7, and exposing the solid imaging unit 105 at unit time 4 to 6 of the unit time 1 to 7, thereby accumulating signal charge in FDA213. This drive (third drive pattern 413a) is repeated M times.

[0053] The signal output period 430 is the period during which distance information is calculated for each pixel 200 from three types of packets 0 to 2 obtained for each pixel 200 during the emission exposure period of the L set, and output to the outside. Specifically, the solid imaging unit 105 outputs three types of packets 0 to 2, obtained for each pixel corresponding to three types of exposure patterns, as imaging signals 130 to the distance calculation unit 108. The distance calculation unit 108, having received three types of packets 0 to 2 for each pixel 200, identifies the distance interval to which the distance to the object 101 belongs for each pixel, calculates the distance, and outputs these results to the outside as distance information 131.

[0054] In this way, the first drive pattern 411a is repeated multiple times, the second drive pattern 412a is repeated multiple times, and the third drive pattern 413a is repeated multiple times, and the drive is performed in a cyclical manner. In the distance measuring device of Patent Document 1, three types of exposure patterns are used, but four drive patterns are required. According to the distance measuring device 10 of this disclosure, only three drive patterns are needed, so the number of light emission times per unit time can be increased, and the distance measuring accuracy can be improved.

[0055] Figure 6 is a circuit block diagram showing the detailed configuration of the distance calculation unit 108 shown in Figure 1. The distance calculation unit 108 comprises a simultaneous processing unit 510, a sorting unit 511, a LUT (Look Up Table) 512, and a distance calculation unit 520.

[0056] The simultaneous processing unit 510 is a circuit that arranges the three packets 0 to 2 for each pixel, which are sequentially output as imaging signals 130 from the solid-state imaging unit 105, in parallel and outputs them to the sorting unit 511.

[0057] The sorting unit 511 is a circuit that sorts packets from the largest to the smallest signal value by comparing the signal values ​​of packets 0 to 2 output from the simultaneous unit 510, and outputs a signal indicating the sorting result (for example, if the sorting result is packets 0, 1, and 2, a signal indicating "012") to the LUT 512.

[0058] LUT512 is a memory that stores the sort results shown in "Range Determination / Packet Value / Sorting Result" in Figure 4 in association with the section signals that identify the distance measurement range (distance section). It reads the section signals corresponding to the sort results output from the sorting unit 511 and outputs them as part of the distance information 131. Specifically, when the sort results show "012", "102", "120", "210", "201", and "021", it outputs the section signals indicating distance sections 1-2, 2-3, 3-4, 4-5, 5-6, and 6-7, respectively, as part of the distance information 131.

[0059] The distance calculation unit 520 is a circuit that calculates the distance to the object 101 by taking as input three packets 0 to 2 output from the simultaneous unit 510, a signal indicating the sort result output from the sorting unit 511, and a section signal output from the LUT 512, and includes an S0 identification unit 521, an S1 identification unit 522, a BG identification unit 523, and a calculation unit 524.

[0060] The S0 identification unit 521 is a circuit that identifies the signal charge S0 obtained when all of the reflected light is imaged by the solid imaging unit 105. The S1 identification unit 522 is a circuit that identifies the signal charge S1 obtained when only a portion of the reflected light is imaged by the solid imaging unit 105. The BG identification unit 523 is a circuit that identifies the signal charge BG obtained when only the background light is imaged by the solid imaging unit 105. The calculation unit 524 is a circuit that calculates the distance to the object 101 based on the signal charges S0, S1 and BG obtained by the S0 identification unit 521, the S1 identification unit 522 and the BG identification unit 523, and outputs it as part of the distance information 131.

[0061] Figure 7 is a diagram illustrating the processing of the distance calculation unit 520 shown in Figure 6.

[0062] Figure 7(a) illustrates distance calculation when the interval signal output from LUT512 indicates distance interval 1-2. As shown in Figure 7(a), let Tp be the time width of the irradiated light, Z be the distance between the distance measuring device 10 and the object 101, and assume that the reflected light returns with a time delay Δt from the irradiated light. Packet 0 represents the signal charge obtained by exposure that is permitted in unit time 1 and 2 corresponding to distance interval 1-2, and therefore represents the signal charge S0 corresponding to all of the reflected light. On the other hand, packet 1 represents the signal charge obtained by exposure that is permitted only in unit time 2 corresponding to distance interval 2, and therefore represents the signal charge S1 corresponding to a part of the reflected light. Furthermore, packet 2 represents the signal charge obtained by exposure that is prohibited in unit time 1 and 2 corresponding to distance interval 1-2 and permitted in unit time when there is no reflected light, and therefore represents the signal charge BG corresponding to the background light.

[0063] Then, the distance Z, where c is the speed of light, can be expressed by equation 1 below, which can be further transformed as shown in equation 2 below, and further transformed as shown in equation 3 below, where S0, S1, and BG are the signal charges S0, S1, and BG respectively.

[0064] Z=c×Δt / 2 (Formula 1) =c×Tp / 2×Δt / Tp (Formula 2) =c×Tp / 2×(S1-BG) / (S0-BG) (Formula 3) Here, (c × Tp / 2) in equation 3 above is a fixed value.

[0065] Therefore, the distance calculation unit 520 uses the above equation 3 to determine if the interval signal output from the LUT 512 indicates the distance interval 1-2. The S0 identification unit 521 selects packet 0 from the three packets 0-2 output from the simultaneous unit 510 and outputs it to the calculation unit 524 as the signal charge S0. The S1 identification unit 522 selects packet 1 from the three packets 0-2 output from the simultaneous unit 510 and outputs it to the calculation unit 524 as the signal charge S1. The BG identification unit 523 selects packet 2 from the three packets 0-2 output from the simultaneous unit 510 and outputs it to the calculation unit 524 as the signal charge BG. The calculation unit 524 then calculates the distance Z by substituting the signal charges S0, S1, and BG output from the S0 identification unit 521, S1 identification unit 522, and BG identification unit 523 into S0, S1, and BG in the above equation 3, and outputs it externally as part of the distance information 131.

[0066] In this example, since the exposure time ratio of packets 0, 1, and 2 is 4:3:3, the BG identification unit 523 calculates the background light amount for signal charge S0 (signal charge BG) by multiplying the signal value of packet 2 by 4 / 3 in order to equalize the background light amount, and calculates the background light amount for signal charge S1 (signal charge BG) by multiplying the signal value of packet 2 by 3 / 3 (i.e., using it as is), and outputs these two types of signal charge BG to the calculation unit 524. For the calculation of (S0-BG), the calculation unit 524 subtracts the background light amount for signal charge S0 from the signal charge S0 indicated by packet 0, and for the calculation of (S1-BG), it subtracts the background light amount for signal charge S1 from the signal charge S1 indicated by packet 1.

[0067] Figure 7(b) illustrates distance calculation when the interval signal output from LUT512 indicates distance interval 2-3. As shown in Figure 7(b), let Tp be the time width of the irradiated light, Z be the distance between the distance measuring device 10 and the object 101, and assume that the reflected light returns after a time delay of (Tp+Δt) from the irradiated light. Packet 1 represents the signal charge obtained by exposure that is permitted in unit time 2 and 3 corresponding to this distance interval 2-3, and therefore represents the signal charge S0 corresponding to all of the reflected light. On the other hand, packet 0 represents the signal charge obtained by exposure that is permitted only in unit time 2 corresponding to distance interval 2, and therefore represents the signal charge S1 corresponding to a part of the reflected light. Furthermore, packet 2 represents the signal charge obtained by exposure that is prohibited in unit time 2 and 3 corresponding to this distance interval 2-3, and is permitted in unit time when there is no reflected light, and therefore represents the signal charge BG corresponding to the background light.

[0068] Then, the distance Z, where c is the speed of light, can be expressed by equation 4 below, which can be further transformed as shown in equations 5 to 7 below, and further transformed as shown in equation 8 below, where S0, S1, and BG are the signal charges S0, S1, and BG respectively.

[0069] Z=c×(Tp+Δt) / 2 (Formula 4) =c×Tp / 2+c×Δt / 2 (Equation 5) =c×Tp / 2+c×Tp / 2×Δt / Tp (Formula 6) =c×Tp / 2×(1+Δt / Tp) (Equation 7) =c×Tp / 2×(1+((S0-BG)-(S1-BG)) / (S0-BG)) (Equation 8) Here, (c × Tp / 2) in equation 8 above is a fixed value.

[0070] Therefore, the distance calculation unit 520 uses the above equation 8 to determine if the section signal output from the LUT 512 indicates distance section 2-3. The S0 identification unit 521 selects packet 1 from the three packets 0-2 output from the simultaneous unit 510 and outputs it to the calculation unit 524 as signal charge S0. The S1 identification unit 522 selects packet 0 from the three packets 0-2 output from the simultaneous unit 510 and outputs it to the calculation unit 524 as signal charge S1. The BG identification unit 523 selects packet 2 from the three packets 0-2 output from the simultaneous unit 510 and outputs it to the calculation unit 524 as signal charge BG. The calculation unit 524 then calculates the distance Z by substituting the signal charges S0, S1, and BG output from the S0 identification unit 521, S1 identification unit 522, and BG identification unit 523 into S0, S1, and BG in the above equation 8, and outputs it externally as part of the distance information 131.

[0071] In this example, since the exposure time ratio of packets 0, 1, and 2 is 4:3:3, the BG identification unit 523 calculates the background light amount for signal charge S0 by multiplying the signal value of packet 2 by 3 / 3 (i.e., using it as is) in order to equalize the background light amount, and calculates the background light amount for signal charge S1 by multiplying the signal value of packet 2 by 3 / 4, and outputs these two types of background light amounts as signal charge BG to the calculation unit 524. For the calculation of (S0-BG), the calculation unit 524 subtracts the background light amount for signal charge S0 from the signal charge S0 indicated by packet 1, and for the calculation of (S1-BG), it subtracts the background light amount for signal charge S1 from the signal charge S1 indicated by packet 0.

[0072] As described above, the method for calculating distance has been explained for the cases where the section signal output from LUT512 indicates distance section 1-2 and distance section 2-3. However, the method for calculating distance is determined in the same way when the section signal output from LUT512 indicates other distance sections.

[0073] Figure 7(c) shows the method for calculating distance for each value of the section signal output from LUT512. Here, from left to right, the section signal value, the packet selected as signal charge S0, the packet selected as signal charge S1, the packet selected as signal charge BG, the coefficient for calculating the background light amount for signal charge S0, the coefficient for calculating the background light amount for signal charge S1, and the distance calculation formula are shown.

[0074] For example, if the section signal output from LUT512 is 3-4, the S0 identification unit 521 selects packet 1 as the signal charge S0, the S1 identification unit 522 selects packet 2 as the signal charge S1, the BG identification unit 523 selects packet 0 as the signal charge BG, the BG identification unit 523 calculates the background light amount for signal charge S0 by multiplying the signal value of packet 0 by a coefficient of 3 / 4, and calculates the background light amount for signal charge S1 by multiplying the signal value of packet 0 by a coefficient of 3 / 4, and outputs these two types of background light amounts as the signal charge BG to the calculation unit 524. For the (S0-BG) calculation, the calculation unit 524 subtracts the background light amount for the signal charge S0 indicated by packet 1 from the signal charge S0 indicated by packet 1, and for the (S1-BG) calculation, it subtracts the background light amount for the signal charge S1 indicated by packet 2 from the signal charge S1, calculates the distance Z using the distance calculation formula shown in Figure 7(c), and outputs it externally as part of the distance information 131.

[0075] Figure 8 is a flowchart showing the operation of the distance measuring device 10 according to the embodiment (i.e., the distance measuring method using the distance measuring device 10).

[0076] The control unit 106 controls the pulse generation unit 107 according to n types of exposure patterns, where n is an integer of 3 or more, indicating exposure permission or exposure prohibition for each of the multiple unit time corresponding to the multiple distance intervals into which the distance measurement range is divided (control step S10). Specifically, in order to realize the three types of exposure patterns shown in Figure 4, the control unit 106 controls the pulse generation unit 107 and the solid imaging unit 105 according to the light emission and exposure drive timings shown in Figure 5.

[0077] Then, under the control of the control unit 106, the distance calculation unit 108 calculates distance information based on n types of signal values ​​corresponding to n types of exposure patterns obtained from the solid imaging unit 105 (distance calculation step S11). Specifically, for each pixel, the control unit 106 determines which of the seven distance intervals the distance to the object 101 belongs to (i.e., performs a range determination) from the result of sorting by the magnitude of the signal values ​​indicated by three types of packets (the order of the packets) based on the "range determination / packet value / sort result" shown in Figure 4. Furthermore, using the determination result and the three types of signal values ​​(packets 0 to 3) corresponding to the three types of exposure patterns, it calculates the distance to the object 101 from the distance calculation formula shown in Figure 7(c).

[0078] As described above, the distance measuring device 10 according to this embodiment is a device that measures the distance to an object by utilizing the time of flight of light to and from the object, and comprises a pulse generation unit 107 that generates an emission pulse that indicates the timing of light irradiation and an exposure pulse that indicates the timing of exposure of reflected light, a control unit 106 that controls the pulse generation unit 107 according to n types of exposure patterns, where n is an integer of 3 or more, which indicate exposure permission or exposure prohibition for each of the multiple unit time corresponding to the multiple distance sections that divide the distance measuring range, a light source unit 102 that irradiates light according to the emission pulse, a solid imaging unit 105 having multiple pixels that take images according to the exposure pulse, and n types corresponding to the n types of exposure patterns obtained from the solid imaging unit 105 The solid imaging unit 105 includes a distance calculation unit 108 that calculates distance information based on the signal values, and acquires n types of signal values ​​for each pixel in a frame period based on reflected light, and the n types of exposure patterns include, for any two adjacent unit time in all of the multiple unit time periods, (1) an exposure pattern in which exposure is permitted in both of the two unit time periods, (2) an exposure pattern in which exposure is permitted in one of the two unit time periods and prohibited in the other, and (3) an exposure pattern in which exposure is prohibited in both of the two unit time periods, and the distance calculation unit 108 generates information as distance information for each pixel, indicating the distance interval corresponding to the reflected light from among multiple distance intervals based on the magnitude relationship between the n types of signal values.

[0079] Furthermore, the distance measurement method by the distance measuring device 10 includes a control step S10 in which the pulse generation unit 107 is controlled according to n types of exposure patterns, where n is an integer of 3 or more, indicating exposure permission or exposure prohibition for each of the multiple unit time corresponding to the multiple distance intervals into which the distance measurement range is divided, and a distance calculation step S11 in which distance information is calculated based on n types of signal values ​​corresponding to the n types of exposure patterns obtained from the solid imaging unit 105.

[0080] As a result, the n types of exposure patterns have the characteristic that for any two adjacent unit time periods, (1) an exposure pattern in which exposure is permitted in both of those unit time periods, (2) an exposure pattern in which exposure is permitted in one of those unit time periods and prohibited in the other, and (3) an exposure pattern in which exposure is prohibited in both of those unit time periods. By utilizing this characteristic, the distance calculation unit 108 can identify the distance interval corresponding to the reflected light from among multiple distance intervals for each pixel. As a result, the range in which distance can be measured is extended compared to conventional techniques that use the same n types of exposure patterns.

[0081] Furthermore, the distance calculation unit 108 calculates distances obtained by further subdividing distance intervals from n types of signal values, using these as distance information. In other words, the distance calculation unit 108 calculates the distance to the object 101 using information indicating distance intervals corresponding to reflected light and n types of signal values ​​corresponding to n types of exposure patterns. As a result, not only information indicating distance intervals but also more detailed information such as the distance itself can be obtained as distance information.

[0082] Furthermore, the pulse generation unit 107 generates light emission pulses and exposure pulses in a cyclical manner, repeating one of the n types of exposure patterns multiple times, then another exposure pattern multiple times, and then the remaining one exposure pattern multiple times, thereby repeating all of the n types of exposure patterns multiple times. As a result, unlike the distance measuring device of Patent Document 1, the distance measuring device 10 of this disclosure only requires three drive patterns, which increases the number of light emission cycles per unit time and can improve distance measuring accuracy.

[0083] (Variation 1) Next, a distance measuring device according to Modification 1 of the embodiment will be described. The distance measuring device according to Modification 1 basically has the same configuration as the distance measuring device 10 according to the embodiment, but the three specific exposure patterns differ from those of the embodiment.

[0084] Figure 9 is a diagram showing a table illustrating an example of three types of exposure patterns by a distance measuring device according to Modification 1 of the Embodiment. In this modification, the distance measuring range consists of 1 to 6. That is, the first to third exposure patterns consist of unit time 1 to 6. More specifically, the first exposure pattern indicates exposure permission only for unit time 1, 2, and 6 out of unit time 1 to 6, the second exposure pattern indicates exposure permission only for unit time 2, 3, and 4 out of unit time 1 to 6, and the third exposure pattern indicates exposure permission only for unit time 4, 5, and 6 out of unit time 1 to 6.

[0085] In this modified example, as in the embodiment, the three types of exposure patterns have the following relationships within the six unit time intervals: (1) an exposure pattern in which exposure is permitted in both of the two adjacent unit time intervals, (2) an exposure pattern in which exposure is permitted in one of the two unit time intervals and prohibited in the other, and (3) an exposure pattern in which exposure is prohibited in both of the two unit time intervals.

[0086] Therefore, as shown in the lower half of the table in Figure 9, in this modified example, as in the embodiment, when packets 0 to 2 are sorted from largest to smallest signal value for each pair of adjacent distance intervals in distance intervals 1 to 6, the order of packets 0 to 2 is unique and without overlap. Utilizing this characteristic, the distance calculation unit 108 identifies the distance interval corresponding to the reflected light for each pixel. Furthermore, the distance calculation unit 108 uses the information indicating the distance interval corresponding to the reflected light and the three types of signal values ​​(packets 0 to 2) corresponding to the three types of exposure patterns to calculate the distance to the object 101 using the same TOF method as in the embodiment.

[0087] Here, the first feature of this modified example is that, unlike the above embodiment, the number of exposure units (3 in this case) is the same for all three types of exposure patterns. As a result, the exposure times for the signal values ​​(packets 0 to 2) corresponding to the three types of exposure patterns are the same, eliminating the need to adjust the background light intensity between the three types of packets. In other words, the calculation unit 524 of the distance calculation unit 108 calculates the distance by simply subtracting the signal charge BG from the signal charge S0 for the (S0-BG) calculation, and by simply subtracting the signal charge BG from the signal charge S1 for the (S1-BG) calculation.

[0088] Thus, in the distance measuring device according to this modified example, the number of exposure units is the same for each of the n exposure patterns. This eliminates the need for processing to equalize the background light intensity, and simplifies the distance calculation process.

[0089] Furthermore, a second feature of this modified version is that, unlike the above embodiment, the exposure permission time and exposure prohibition time are equal for all n types of exposure patterns. As a result, the pulse generation unit 107 can output a single signal with a 50% duty cycle for any of the n types of exposure pulses, simplifying the circuit.

[0090] (Modification 2) Next, a distance measuring device according to a modified example 2 of the embodiment will be described. The distance measuring device according to modified example 2 basically has the same configuration as the distance measuring device 10 according to the embodiment, but the drive timing of the emission and exposure of the solid imaging unit 105 to realize three types of exposure patterns differs from that of the embodiment.

[0091] Figure 10 shows the light emission and exposure drive timing of the solid imaging unit 105 to realize three types of exposure patterns by the distance measuring device according to a modified example 2 of the embodiment. Each frame consists of a light emission exposure period 420 of Ma times (for example, 1500 times) and a signal output period 430.

[0092] During the emission exposure period 420, as shown in the drive pattern 420a of Figure 10, the pulse generation unit 107 generates one exposure pulse indicating exposure permission for one of the n types of exposure patterns, then generates one exposure pulse indicating exposure permission for another of the n types of exposure patterns, and then generates one exposure pulse indicating exposure permission for the remaining one of the n types of exposure patterns, thereby cyclically generating one exposure pulse indicating exposure permission for all of the n types of exposure patterns. Furthermore, when the pulse generation unit 107 overlaps within the same unit time, it generates an exposure pulse indicating exposure permission for one of the n types of exposure patterns at any of the multiple unit time intervals.

[0093] In other words, during the light emission exposure period 420, the control unit 106 controls the pulse generation unit 107 to generate light emission pulses 120 and exposure pulses 121 to 123, thereby causing the light source unit 102 to emit light during unit time 1 of the unit time 1 to 7. Furthermore, when three exposure patterns are superimposed within the same unit time, the control unit 106 does not allow light emission for two or more exposure patterns within the same unit time, and when focusing on one exposure pattern, it exposes every other pattern, and drives the three exposure patterns in a cyclical manner by linking their drives.

[0094] Specifically, as shown by the timing of the thick solid line in the drive pattern 420a in Figure 10, the pulse generation unit 107 generates a light emission pulse 120 indicating light emission permission in unit time 1, generates an exposure pulse 121 indicating exposure permission belonging to the first exposure pattern in unit time 1 to 2, generates an exposure pulse 123 indicating exposure permission belonging to the third exposure pattern in the following unit time 4 to 6, generates a light emission pulse 120 indicating light emission permission in the next unit time 1, generates an exposure pulse 122 indicating exposure permission belonging to the second exposure pattern in the following unit time 2 to 4, and generates an exposure pulse 121 indicating exposure permission belonging to the first exposure pattern in the following unit time 6 to 7, and repeats this for Ma times (for example, 1500 times) of light emission pulses.

[0095] As a result, two exposures are performed for each light emission, improving light utilization efficiency (specifically, doubling it) compared to embodiments where only one exposure is performed for each light emission, and consequently improving distance measurement accuracy. Furthermore, since the exposure pattern is switched with each exposure and the signal charge obtained by the exposure is distributed to appropriate packets, calculation errors are suppressed when measuring distance with a moving object 101 compared to embodiments where the same exposure pattern is repeated.

[0096] In this modified example, the light emission and exposure drive timing shown in Figure 11 may be used instead of the light emission and exposure drive timing shown in Figure 10. Figure 11 is a diagram showing the light emission and exposure drive timing of the solid imaging unit 105 for realizing three types of exposure patterns by the distance measuring device according to the modified example of Modification Example 2. The difference from Figure 10 is that the exposure permission time width is the same for all three types of exposure patterns. Furthermore, the duty cycle for exposure permission is 25% for all three types of exposure patterns.

[0097] In other words, in the modified version 2 shown in Figure 11, each of the n exposure patterns consists of a sequence of exposure permission periods that last for m units of time, which is an integer greater than or equal to 1. As a result, in this modified version, the ratio of exposure permission periods to exposure prohibition periods is 1:3 for each of the n exposure patterns.

[0098] As a result, the distance measuring device according to Modification 2 exhibits the effects of improved light utilization efficiency, improved distance measuring accuracy, and suppression of calculation errors when measuring distance to moving objects, compared to the embodiment. In addition, it also exhibits the effects of stabilization and suppression of heat generation in the driving of the solid imaging unit 105 and simplification of the circuit of the pulse generation unit 107, compared to Modification 2.

[0099] (Variation 3) Next, a distance measuring device according to Modification 3 of the embodiment will be described. The distance measuring device according to Modification 3 basically has the same configuration as the distance measuring device 10 according to the embodiment, but the drive timing of the emission and exposure of the solid imaging unit 105 for obtaining three types of packets 0 to 2 is swapped with that of the embodiment.

[0100] Figure 12 is a diagram showing a table illustrating the drive timing of light emission and exposure by the distance measuring device according to the third modified embodiment. As shown in this figure, in this modified embodiment, three types of light emission patterns and one type of exposure pattern are used.

[0101] In the "first light emission pattern," the light emission pulse 120 indicates light emission permission at unit time 1 and 2, light emission prohibition at unit time 3 to 5, and light emission permission at unit time 6 and 7. A signal charge is accumulated in FDA211 corresponding to this first light emission pattern, and the accumulated signal charge is packet 0. This first light emission pattern corresponds to the first exposure pattern shown in Figure 4 in the embodiment, where exposure permission and exposure prohibition are replaced with light emission permission and light emission prohibition, respectively, and their order is reversed in the time direction.

[0102] In the "second light emission pattern," the light emission pulse 120 indicates light emission prohibition for unit time 1 to 3, light emission permission for unit time 4 to 6, and light emission prohibition for unit time 7. A signal charge is accumulated in FDA212 corresponding to this second light emission pattern, and the accumulated signal charge is packet 1. This second light emission pattern corresponds to the second exposure pattern shown in Figure 4 in the embodiment, where exposure permission and exposure prohibition are replaced with light emission permission and light emission prohibition, respectively, and their order is reversed in the time direction.

[0103] In the "third light emission pattern," the light emission pulse 120 indicates light emission prohibition at unit time 1, light emission permission at unit time 2-4, and light emission prohibition at unit time 5-7. A signal charge is accumulated in FDA213 corresponding to this third light emission pattern, and the accumulated signal charge is packet 2. This third light emission pattern corresponds to the third exposure pattern shown in Figure 4 in the embodiment, where exposure permission and exposure prohibition are replaced with light emission permission and light emission prohibition, respectively, and their order is reversed in the time direction.

[0104] The "exposure pattern" is a single type common to all three types of packets. Exposure pulses 121 to 123 all indicate exposure prohibition for unit time 1 to 6 and exposure permission for unit time 7. This exposure pattern corresponds to replacing the emission permission and emission prohibition in the emission pattern shown in Figure 4 in the embodiment with exposure permission and exposure prohibition, respectively, and reversing their order in the time direction.

[0105] The "Range Determination / Packet Value / Sorting Result" shown in the lower half of the table in Figure 12 indicates the sorting result of packets 0-2 when sorted from the largest signal value to the smallest for each of two adjacent distance intervals in distance intervals 1-7.

[0106] As can be seen from Figure 12, in this modified example, the three types of light emission patterns include a light emission pattern in which light emission is permitted in any two adjacent unit time periods within seven unit time periods, a light emission pattern in which light emission is permitted in one of the two unit time periods and prohibited in the other, and a light emission pattern in which light emission is prohibited in both of the two unit time periods.

[0107] Due to these characteristics, in this modified example as well, as shown in the lower half of the table in Figure 12, the sorting result (order of packets) based on the magnitude of the signal values ​​shown by the three types of packets becomes unique depending on the position (i.e., timing) in the unit time 1 to 7 in which the reflected light is detected. Using this, the distance calculation unit 108 determines which of the seven distance intervals the distance to the object 101 belongs to (i.e., performs a range determination), and further calculates the distance to the object 101 using the values ​​of packets 0 to 2.

[0108] However, in this modified example, unlike the embodiment, packets 0 to 2 are generated by exposure only during the last unit time 7 for any of the three types of light emission patterns. Therefore, the correspondence between the measured distance and the sequence of distance intervals 1 to 7 in the distance measurement range (i.e., the sequence of unit times 1 to 7) is reversed compared to the embodiment.

[0109] For example, if reflected light corresponding to distance interval 1 (i.e., unit time 1) is detected, the furthest distance is calculated, and if reflected light corresponding to distance interval 7 (i.e., unit time 7) is detected, the closest distance is calculated. Furthermore, in this modified example, the distance calculation formula shown in Figure 7(c) corresponds to the distance calculation formula shown in Figure 7(c) inverted in the time direction.

[0110] Furthermore, the variations in exposure patterns shown in Modifications 1 and 2 of the embodiment can also be applied to this modification as variations in the light emission pattern by swapping the drive timings of light emission and exposure. Specifically, when the three types of light emission patterns are superimposed over the same unit time, at least one of the three types of light emission patterns may be permitted to emit light at any of the seven unit time intervals. Moreover, for all three types of light emission patterns, the time for which light emission is permitted and the time for which light emission is prohibited may be equal.

[0111] Furthermore, the flowchart in Figure 8 shown in the embodiment can also be applied to this modified example by replacing "n types of exposure patterns" with "n types of light emission patterns."

[0112] As described above, the distance measuring device according to this modified example is a device that measures the distance to an object by utilizing the time of flight of light to and from the object, and comprises a pulse generation unit 107 that generates an emission pulse that indicates the timing of light irradiation and an exposure pulse that indicates the timing of exposure of reflected light, a control unit 106 that controls the pulse generation unit 107 according to n types of emission patterns, where n is an integer of 3 or more, which indicate emission permission or emission prohibition for multiple unit time corresponding to multiple distance sections that divide the distance measuring range, a light source unit 102 that irradiates light according to the emission pulse, a solid-state imaging unit 105 having multiple pixels that image according to the exposure pulse, and n types of signals corresponding to the n types of emission patterns obtained from the solid-state imaging unit 105 The system includes a distance calculation unit 108 that calculates distance information based on signal values. The solid imaging unit 105 acquires n types of signal values ​​for each pixel during a frame period based on reflected light. The n types of light emission patterns include, for any two adjacent unit time periods within a plurality of unit time periods, (1) a light emission pattern where light emission is permitted in both of the two unit time periods, (2) a light emission pattern where light emission is permitted in one of the two unit time periods and prohibited in the other, and (3) a light emission pattern where light emission is prohibited in both of the two unit time periods. The distance calculation unit 108 generates distance information for each pixel, indicating the distance interval corresponding to the reflected light from among a plurality of distance intervals, based on the relative magnitudes of the n types of signal values.

[0113] Furthermore, the distance measurement method by the distance measuring device 10 includes a control step of controlling the pulse generation unit 107 according to n types of light emission patterns, where n is an integer of 3 or more, that indicate light emission permission or light emission prohibition for multiple unit time intervals corresponding to multiple distance intervals into which the distance measurement range is divided, and a distance calculation step of calculating distance information based on n types of signal values ​​corresponding to the n types of light emission patterns obtained from the solid imaging unit 105.

[0114] As a result, the n types of light emission patterns have the characteristic that, for any two adjacent unit time periods within multiple unit time periods, (1) a light emission pattern that is permitted to emit light in both of those unit time periods, (2) a light emission pattern that is permitted to emit light in one of those unit time periods and prohibited in the other, and (3) a light emission pattern that is prohibited in both of those unit time periods. By utilizing this characteristic, the distance calculation unit 108 can identify the distance interval corresponding to the reflected light from among multiple distance intervals for each pixel. As a result, the range that can be measured is extended compared to conventional techniques that use the same n types of exposure patterns.

[0115] Here, the distance calculation unit 108 may further calculate distances obtained by subdividing distance intervals from n types of signal values ​​as distance information. In other words, the distance calculation unit 108 calculates the distance to the object 101 using information indicating distance intervals corresponding to reflected light and n types of signal values ​​corresponding to n types of light emission patterns. As a result, not only information indicating distance intervals but also more detailed information such as distance can be obtained as distance information.

[0116] Furthermore, the pulse generation unit 107 may generate emission pulses and exposure pulses in a cyclical manner, repeating one of the n emission patterns multiple times, then another emission pattern multiple times, and then the remaining one emission pattern multiple times, thereby repeating all n emission patterns multiple times. According to this embodiment of the distance measuring device 10, the number of required drive patterns is reduced compared to the conventional technology, and as a result, the number of emission times per unit time can be increased, and the distance measuring accuracy can be improved.

[0117] Furthermore, each of the n types of light emission patterns may consist of a sequence of light emission permissions that last for m units of time, which is an integer greater than or equal to 1. This also provides the effects of stabilization and suppression of heat generation during the operation of the solid-state imaging unit 105, and simplification of the circuit of the pulse generation unit 107.

[0118] The distance measuring device and distance measuring method of this disclosure have been described above based on embodiments and modifications, but this disclosure is not limited to these embodiments and modifications. Within the scope of this disclosure, various modifications conceivable by those skilled in the art, as well as other forms constructed by combining some of the components of the embodiments and modifications, are also included, as long as they do not depart from the spirit of this disclosure.

[0119] For example, in the above embodiment, three types of exposure patterns were exemplified as n types of exposure patterns, but four or more types of exposure patterns may also be used. Figure 13 is a table showing an example of four types of exposure patterns by the distance measuring device 10 shown in Figure 1. Here, the first to fourth exposure patterns are shown, which consist of distance intervals 1 to 9 (i.e., unit time 1 to 9) as the distance measuring range.

[0120] The first to fourth exposure patterns shown in Figure 13 have the following relationships within unit time 1 to 9: for any two adjacent unit time periods, (1) an exposure pattern in which exposure is permitted in both of those unit time periods, (2) an exposure pattern in which exposure is permitted in one of those unit time periods and prohibited in the other, and (3) an exposure pattern in which exposure is prohibited in both of those unit time periods.

[0121] As a result, as shown in the "Range Determination / Packet Value / Sorting Result" in the lower half of the table in Figure 13, the sorting result (order of packets) is unique, depending on the position (i.e., timing) in the unit time 1 to 9 in which the reflected light is detected, and based on the magnitude of the signal values ​​shown by the four types of packets 0 to 3. Therefore, even with these four types of exposure patterns, the distance measuring device 10 can use this sorting result to determine which of the seven distance intervals the distance to the object 101 belongs to (i.e., perform range determination). [Industrial applicability]

[0122] The distance measuring device described herein can be used as a TOF (Time-of-Flight) type distance measuring device, and in particular as a distance measuring device capable of extending the measuring distance compared to conventional devices, for example, as a TOF type long-range image sensor. [Explanation of Symbols]

[0123] 10 Ranging device 100 imaging space 101 Object 102 Light source section 103 Optical Lenses 104 Optical Filters 105 Solid-state imaging unit 106 Control Unit 107 Pulse generation unit 108 Distance calculation section 120 light pulses 121-123 Exposure pulses 130 Imaging signal 131 Distance Information 140 Background light source 200 pixels 201 Photoelectric conversion unit 210 Drain 211-213 FDA 214-217 Gates 221-223 Source Follower Circuit 231-233 Output Selection Transistor 240 Output Enable Signal 241-243 pixel signals 300-303 Select signal lines 311-313, 321-323, 331-333 Vertical signal lines 370 Column AD 371 Shift Register 372 row selection section 410 Setting the emission exposure period 411 First emission exposure period 411a First drive pattern 412 Second emission exposure period 412a Second drive pattern 413 Third emission exposure period 413a Third drive pattern 414 Signal output period 420 Emission exposure period 420a drive pattern 430 Signal output period 510 Simultaneous Unit 511 Sorting section 512 LUT 520 Distance calculation section 521 S0 specific part 522 S1 specific part 523 BG Specification Department 524 Calculation Department

Claims

1. A distance measuring device that measures the distance to an object by utilizing the time of flight of light to and from the object, A pulse generation unit that generates a light emission pulse to indicate the timing of light irradiation and an exposure pulse to indicate the timing of exposure of reflected light, A control unit controls the pulse generation unit according to n types of exposure patterns, where n is an integer of 3 or more, indicating exposure permission or exposure prohibition for each of the multiple unit time corresponding to multiple distance intervals into which the distance measurement range is divided. A light source unit that irradiates light according to the aforementioned emission pulse, A solid-state imaging unit having multiple pixels that captures images according to the exposure pulse, The system includes a distance calculation unit that calculates distance information based on n types of signal values ​​corresponding to the n types of exposure patterns obtained from the solid imaging unit, The solid-state imaging unit acquires the n types of signal values ​​for each pixel in one frame period based on the reflected light. The n types of exposure patterns include, within the plurality of unit time periods, an exposure pattern in which exposure is permitted for any two adjacent unit time periods, an exposure pattern in which exposure is permitted for one of the two unit time periods and prohibited for the other, and an exposure pattern in which exposure is prohibited for both of the two unit time periods. The distance calculation unit generates, for each pixel, information indicating the distance interval corresponding to the reflected light among the plurality of distance intervals, based on the relative magnitudes of the n types of signal values, as distance information. The pulse generation unit generates the emission pulse and the exposure pulse in such a cyclical manner that it repeats one of the n types of exposure patterns multiple times, then another exposure pattern multiple times, and then the remaining one exposure pattern multiple times, thereby repeating all of the n types of exposure patterns multiple times. Ranging device.

2. The distance calculation unit further calculates the distance obtained by subdividing the distance interval from the n types of signal values, using this as distance information. The distance measuring device according to claim 1.

3. The n types of exposure patterns are such that the number of units of exposure time is the same for all of them. The distance measuring device according to claim 1 or 2.

4. A distance measuring device that measures the distance to an object by utilizing the time of flight of light to and from the object, A pulse generation unit that generates a light emission pulse to indicate the timing of light irradiation and an exposure pulse to indicate the timing of exposure of reflected light, A control unit controls the pulse generation unit according to n types of exposure patterns, where n is an integer of 3 or more, indicating exposure permission or exposure prohibition for each of the multiple unit time corresponding to multiple distance intervals into which the distance measurement range is divided. A light source unit that irradiates light according to the aforementioned emission pulse, A solid-state imaging unit having multiple pixels that captures images according to the exposure pulse, The system includes a distance calculation unit that calculates distance information based on n types of signal values ​​corresponding to the n types of exposure patterns obtained from the solid imaging unit, The solid-state imaging unit acquires the n types of signal values ​​for each pixel in one frame period based on the reflected light. The n types of exposure patterns include, within the plurality of unit time periods, an exposure pattern in which exposure is permitted for any two adjacent unit time periods, an exposure pattern in which exposure is permitted for one of the two unit time periods and prohibited for the other, and an exposure pattern in which exposure is prohibited for both of the two unit time periods. The distance calculation unit generates, for each pixel, information indicating the distance interval corresponding to the reflected light among the plurality of distance intervals, based on the relative magnitudes of the n types of signal values, as distance information. The pulse generation unit generates one exposure pulse indicating exposure permission for one of the n types of exposure patterns, then generates another exposure pulse indicating exposure permission for another of the n types of exposure patterns, and then generates another exposure pulse indicating exposure permission for the remaining one of the n types of exposure patterns, thereby cyclically generating one exposure pulse indicating exposure permission for all of the n types of exposure patterns. Ranging device.

5. The pulse generation unit, when superimposed over the same unit time, generates an exposure pulse indicating permission to expose, belonging to one of the n types of exposure patterns, at any of the multiple unit time periods. The distance measuring device according to claim 4.

6. Each of the n types of exposure patterns consists of a sequence of m exposure permissions, each lasting for one or more units of time. A distance measuring device according to any one of claims 1 to 5.

7. A distance measuring device that measures the distance to an object by utilizing the time of flight of light to and from the object, A pulse generation unit that generates a light emission pulse to indicate the timing of light irradiation and an exposure pulse to indicate the timing of exposure of reflected light, A control unit controls the pulse generation unit according to n types of light emission patterns, where n is an integer of 3 or more, which indicate light emission permission or light emission prohibition for multiple unit time intervals corresponding to multiple distance intervals into which the distance measurement range is divided. A light source unit that irradiates light according to the aforementioned emission pulse, A solid-state imaging unit having multiple pixels that captures images according to the exposure pulse, The system includes a distance calculation unit that calculates distance information based on n types of signal values ​​corresponding to the n types of light emission patterns obtained from the solid-state imaging unit, The solid-state imaging unit acquires the n types of signal values ​​for each pixel in one frame period based on the reflected light. The n types of light emission patterns include, within the plurality of unit time periods, a light emission pattern in which light emission is permitted for any two adjacent unit time periods, a light emission pattern in which light emission is permitted for one of the two unit time periods and prohibited for the other, and a light emission pattern in which light emission is prohibited for both of the two unit time periods. The distance calculation unit generates, for each pixel, information indicating the distance interval corresponding to the reflected light from among the plurality of distance intervals, based on the relative magnitudes of the n types of signal values, as distance information. The pulse generation unit generates the light emission pulse and the exposure pulse in such a cyclical manner that it repeats one of the n types of light emission patterns multiple times, then another one of the n types of light emission patterns multiple times, and then the remaining one of the n types of light emission patterns multiple times. Ranging device.

8. The distance calculation unit further calculates the distance obtained by subdividing the distance interval from the n types of signal values, using this as distance information. The distance measuring device according to claim 7.

9. Each of the n types of light emission patterns consists of a sequence of m light emission permits, each lasting for one or more units of time, where m is an integer. The distance measuring device according to claim 7 or 8.

10. A distance measuring method using a distance measuring device that measures the distance to an object by utilizing the time of flight of light to and from the object, The distance measuring device is A pulse generation unit that generates a light emission pulse to indicate the timing of light irradiation and an exposure pulse to indicate the timing of exposure of reflected light, A light source unit that irradiates light according to the aforementioned emission pulse, The system includes a solid-state imaging unit having multiple pixels that captures images according to the exposure pulse, The distance measurement method is, A control step to control the pulse generation unit according to n types of exposure patterns, where n is an integer of 3 or more, indicating exposure permission or exposure prohibition for each of the multiple unit time corresponding to multiple distance intervals into which the distance measurement range is divided, The distance calculation step includes calculating distance information based on n types of signal values ​​corresponding to the n types of exposure patterns obtained from the solid imaging unit, The solid-state imaging unit acquires the n types of signal values ​​for each pixel in one frame period based on the reflected light. The n types of exposure patterns include, within the plurality of unit time periods, an exposure pattern in which exposure is permitted for any two adjacent unit time periods, an exposure pattern in which exposure is permitted for one of the two unit time periods and prohibited for the other, and an exposure pattern in which exposure is prohibited for both of the two unit time periods. In the distance calculation step, based on the relative magnitudes of the n types of signal values, information indicating the distance interval corresponding to the reflected light from among the plurality of distance intervals is generated for each pixel as distance information. The pulse generation unit generates the emission pulse and the exposure pulse in such a cyclical manner that it repeats one of the n types of exposure patterns multiple times, then another exposure pattern multiple times, and then the remaining one exposure pattern multiple times, thereby repeating all of the n types of exposure patterns multiple times. Distance measurement method.

11. A distance measuring method using a distance measuring device that measures the distance to an object by utilizing the time of flight of light to and from the object, The distance measuring device is A pulse generation unit that generates a light emission pulse to indicate the timing of light irradiation and an exposure pulse to indicate the timing of exposure of reflected light, A light source unit that irradiates light according to the aforementioned emission pulse, The system includes a solid-state imaging unit having multiple pixels that captures images according to the exposure pulse, The distance measurement method is, A control step in which the pulse generation unit is controlled according to n types of light emission patterns, where n is an integer of 3 or more, which indicate light emission permission or light emission prohibition for multiple unit time intervals corresponding to multiple distance intervals into which the distance measurement range is divided, The step includes calculating distance information based on n types of signal values ​​corresponding to the n types of light emission patterns obtained from the solid-state imaging unit, The solid-state imaging unit acquires the n types of signal values ​​for each pixel in one frame period based on the reflected light. The n types of light emission patterns include, within the plurality of unit time periods, a light emission pattern in which light emission is permitted for any two adjacent unit time periods, a light emission pattern in which light emission is permitted for one of the two unit time periods and prohibited for the other, and a light emission pattern in which light emission is prohibited for both of the two unit time periods. In the distance calculation step, based on the relative magnitudes of the n types of signal values, information indicating the distance interval corresponding to the reflected light from among the plurality of distance intervals is generated for each pixel as distance information. The pulse generation unit generates the light emission pulse and the exposure pulse in such a cyclical manner that it repeats one of the n types of light emission patterns multiple times, then another one of the n types of light emission patterns multiple times, and then the remaining one of the n types of light emission patterns multiple times. Distance measurement method.

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