JP6539990B2 - Optical flight type distance measuring device - Google Patents

Description

  According to the present invention, modulated light modulated in a pattern having a repetitive cycle is emitted in space, charges corresponding to incident light including reflected light reflected by the modulated light are divided by a plurality of modulation switches, and stored in plural. The present invention relates to an optical flight distance measuring apparatus which calculates a distance from an own apparatus to an object by using a value stored in a capacity and sampled.

  A TOF (Time of Flight) type distance measuring device is provided as a distance measuring device which calculates the distance from the own device to an object without contact. The optical flight type distance measuring apparatus emits modulated light (ranging light) modulated in a pattern having a repetitive cycle to space, and receives incident light including reflected light which is reflected by the object. Then, the optical flight type distance measuring apparatus distributes the charge corresponding to the received incident light by the plurality of modulation switches, accumulates the charge in the plurality of storage capacitors, and calculates the distance from the own apparatus to the object using the sampled values. (See, for example, Patent Documents 1 to 4).

  In the optical flight type distance measuring apparatus, when the distance from the own apparatus to the object is short or the object is an object having a high reflectance, the reflected light of high intensity is received. On the other hand, when the distance from the own apparatus to the object is long or the object is an object with low reflectance, only reflected light of weak intensity is received. Therefore, a large dynamic range (for example, 80 dB or more) is required in the optical flight distance measuring apparatus. Particularly in the case of on-vehicle etc., if at least one of the own device and the object (person, vehicle, wall, etc.) is moving, if the distance from the own device to the object is short, Frequent calculations of the distance (increasing the frame rate) are required to avoid collisions. That is, it is necessary to make a large dynamic range and a high frame rate compatible.

  It is difficult to achieve a dynamic range of 80 dB or more with ordinary pixels, and it is necessary to perform multiple exposure (multiple exposures). However, when multiple exposures are performed in series, the exposure time becomes long, which causes a problem that the followability to a moving object is deteriorated. In this regard, a method of grouping a plurality of pixels in a plane and changing the exposure time for each group is disclosed (see, for example, non-patent documents 1 and 2). As shown in FIGS. 31 and 32, the light receiving element 101 is configured to have a PD (Photodiode) 102, two modulation switches 103a and 103b, and two storage capacitors 104a and 104b. Will be described as an example. In this case, as shown in FIG. 33, for example, the group of pixels A repeats driving 1000 times to perform long-time exposure, and the group of pixels B repeats driving 100 times to perform short-time exposure. The range can be extended by 20 dB.

Patent No. 5579893 gazette JP, 2010-96730, A Patent No. 5855903 gazette JP, 2010-25906, A

S.Nayar and T.Mitsunaga. "High Dynamic Range Imaging: Spatial Varying Pixel Exposures." In IEEE Conference on Computer Vision and Pattern Recognition (CVPR), volume 1, pages 472-479, Jun 2000 S. G. Narasimhan and S. K. Nayar "Enhancing Resolution Along Multiple Imaging Dimensions Using Assorted Pixels." "IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE, VOL. 27, NO. 4, APRIL 2005, pp. 518

  However, in the methods disclosed in the above-mentioned Non-Patent Documents 1 and 2, it is premised that adjacent pixels A and B receive the same reflected light. Therefore, it becomes difficult to design a lens for collecting light on the light receiving element. If the design of this lens can not satisfy the above-mentioned preconditions, a fixed pattern depending on the arrangement of pixels will occur. In addition, in the configuration in which the group of the pixel A and the group of the pixel B are arranged in the same row without being divided for each row (coexistence), there is a problem that the wiring becomes complicated.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to appropriately expand the dynamic range without being restricted by the receiving condition of the reflected light, the design of the light receiving optical system, and the arrangement of the pixels. It is an object of the present invention to provide an optical flight type distance measuring apparatus which can

  According to the first aspect of the present invention, the light emitting element emits the modulated light modulated in the pattern having the repetition period to the space. The driving means drives the light emitting element. The light receiving element distributes the charges according to the incident light including the reflected light obtained by the modulated light reflected by the object by the plurality of modulation switches, and accumulates the charges in the plurality of storage capacitors. The control means controls driving of the plurality of modulation switches. The distance measurement value acquisition means calculates the distance from the own device to the object using the value sampled by the light receiving element to acquire the distance measurement value.

Control means controls the driving of the plurality of modulated switches the split to so that a plurality of sub-exposure periods the basic exposure period, accumulation in the sub exposure period in a plurality of sub-exposure periods in the one-round periods 1 round The period during which the control signal for driving one of the two modulation switches is H and the control signal for driving the other is L as a basic exposure pattern in the basic exposure period while holding the stored charge without resetting. Is defined as 1, and a period in which the control signal for driving one is L and the control signal for driving the other is H is defined as -1, and a period of 1 is defined as a sub-exposure pattern in the sub-exposure period. The period of 1 and the period of -1 are divided n (n is a natural number of 2 or more) so that the period of -1 is 180 degrees out of phase, and 0 is inserted in a period other than 1 and -1 . Distance value acquiring means may acquire the distance value of the short time exposure from the charge amount of charges accumulated in the one-round period, it integrates the charge amount of the plurality of charge stored in the one-round period The long distance exposure value is acquired.

  That is, unlike the prior art in which a plurality of pixels are grouped into a long exposure group and a short exposure group to obtain a long distance exposure value and a short distance exposure value, respectively, the basic exposure period Is divided into a plurality of sub-exposure periods, so that both a long-distance distance measurement value and a short-time distance measurement value can be obtained from one pixel (the same pixel). As a result, the dynamic range can be expanded without being restricted by the receiving condition of the reflected light, the design of the light receiving optical system, and the arrangement of the pixels. In particular, it is suitable in the case of an on-vehicle in which at least one of the own apparatus and the target moves.

Functional block diagram showing an embodiment of the present invention Diagram showing the configuration of a light receiving element (2-capacitance configuration) Diagram showing a sequence of 2 capacitance / 4 phase ranging Diagram showing differential output sequence Diagram showing the concept of the present invention A diagram showing a sequence for realizing 4-phase ranging exposure with 2-division sub-exposure The figure which shows the timing chart which realizes exposure of 4 phase ranging with 2 division sub exposure The figure which shows the sequence which explains the principle which acquires the ranging value from the sub exposure of 2 division A diagram showing a configuration and a sequence for realizing "0" (part 1) The figure which shows the structure and sequence which implement | achieve "0" (the 2) A diagram (part 3) showing a configuration and a sequence for realizing "0" A diagram showing a sequence for realizing exposure of four-phase distance measurement by sub-exposure of four divisions (part 1) A diagram showing a sequence for realizing exposure of four-phase distance measurement by sub-exposure of four divisions (part 2) A diagram showing a sequence for realizing exposure of four-phase distance measurement with sub-exposure of four divisions (part 3) A diagram showing a part of a distance measurement value acquisition circuit (part 1) The figure which shows the timing chart which shows the output of an output signal (the 1) A diagram showing a part of a distance measurement value acquisition circuit (part 2) Timing chart showing output of output signal (part 2) A diagram showing a timing chart for performing rolling reset and rolling read (part 1) The figure which shows the timing chart which performs rolling reset and rolling read-out (the 2) The figure which shows the timing chart which performs global reset and rolling read-out (the 1) The figure which shows the timing chart which performs global reset and rolling read-out (the 2) The figure which shows the timing chart which performs global reset and rolling read-out (the 3) The figure which shows the timing chart which performs control which makes the amplitude for every pixel of the output of a long time accumulation optimal (the 1) The figure which shows the timing chart which performs control which makes the amplitude for every pixel of the output of long-term accumulation optimal (the 2) The figure which shows the timing chart which performs control which makes the amplitude for every pixel of the output of long-term accumulation optimal (the 3) A diagram showing a part of a distance measurement value acquisition circuit (part 3) Diagram showing wiring (Part 1) A diagram showing a part of a distance measurement value acquisition circuit (part 4) Diagram showing wiring (Part 2) Diagram showing the configuration of a light receiving element (2-capacitance configuration) Diagram showing a sequence of 2 capacitance / 4 phase ranging Diagram showing a timing chart for performing multiple exposure

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings in which an embodiment of the present invention is applied to, for example, an on-vehicle optical flight distance measuring apparatus that can be mounted on a vehicle. The object for which the distance from the own device is calculated is, for example, a person, a vehicle, a wall or the like. The optical flight type distance measuring apparatus 1 includes a signal source 2, a drive circuit 3 (drive means), a light emitting element 4, a control circuit 5 (control means), a light receiving element 6, and a CM (common mode) component removal circuit And a distance measurement value acquisition circuit 8 (distance measurement value acquisition means). The distance measurement value acquisition circuit 8 includes buffers 9 a and 9 b, a difference detection circuit 10, an AD conversion circuit 11, and a digital signal processing circuit 12.

  The signal source 2 outputs a drive signal to the drive circuit 3 and the control circuit 5 to establish synchronization between the light emitting element 4 and the light receiving element 6 and synchronizes with the modulated light emitted from the light emitting element 4. The exposure of the light receiving element 6 is controlled. The drive signal output from the signal source 2 may be a rectangular pulse (usually several to several tens of MHz) for driving the light emitting element 4 and the light receiving element 6 or may be only a synchronization pulse. The light emitting element 4 is, for example, a laser diode (LD) or a light emitting diode (LED) that emits infrared light as modulated light. The light receiving element 6 is an image sensor using, for example, a process of a complementary metal oxide semiconductor (CMOS) or a charge coupled device (CCD).

  As shown in FIG. 2, the light receiving element 6 has a PD (Photodiode) 13, two modulation switches 14a and 14b, and two storage capacitors 15a and 15b. The two modulation switches 14a and 14b are, for example, MOS type devices such as MOS transistors and transfer gates, and devices having a CCD structure. The two storage capacitors 15a and 15b are, for example, capacitive elements such as MOS, CCD, MIM (Metal Insulator Metal), wiring, parasitic capacitance of PN junction, and the like. The light receiving element 6 drives the modulation switches 14a and 14b by the control signals (gate signals) TG1 and TG2, distributes the charges generated by the received incident light to the storage capacitors 15a and 15b, and indicates the charge amount of the distributed charges Are output to the CM component removal circuit 7. Since the control signals TG1 and TG2 are signals synchronized with the modulated light, the charge amount of the charge distributed to the storage capacitors 15a and 15b changes according to the distance from the own device to the object. Although two storage capacitors 15a and 15b are illustrated in FIG. 2, three or more storage capacitors may be provided.

  The CM component removal circuit 7 prevents saturation of the pixel due to the charge generated due to the background light, when there is a level of background light that can not be ignored with respect to the modulated light being emitted. . Various techniques have been disclosed in the prior art as methods of removing the CM component. For example, U.S. Pat. No. 6,919,549 B2, U.S. Pat. No. 102005056774 A1, U.S. Pat. No. 1,622,200 A1 and the like. The difference detection circuit 10 detects the difference between the signals input from the CM component removal circuit 7 via the buffers 9a and 9b, and outputs a signal corresponding to the detected difference to the AD conversion circuit 11. The buffers 9a and 9b are realized by, for example, a source follower circuit because of their simplicity. The difference detection circuit 10 is realized by, for example, a differential amplifier.

  The AD conversion circuit 11 converts the signal input from the difference detection circuit 10 from an analog signal to a digital signal and outputs the digital signal to the digital signal processing circuit 12. The digital signal processing circuit 12 performs digital signal processing on the signal input from the AD conversion circuit 11, calculates the distance from the own device to the object from the charge amount of the charge distributed to the storage capacitors 15a and 15b, and measures the distance value. To get distance measurement.

  FIG. 3 shows a sequence (modulation period: Tm, exposure period: Tw) in the case of performing four-phase distance measurement (driving the light receiving element 6 with four phases) with the duty of the light emission waveform being 50%. The waveform (light emission waveform 110) of the modulated light emitted from the light emitting element 4 is modulated by a rectangular wave synchronized with the control signals TG1 and TG2. Although FIG. 3 exemplifies a case where modulation is performed using a rectangular wave, modulation may be performed using a waveform such as a sine wave, a triangular wave, or a pseudo random sequence. The waveform (reflected waveform 120) of the reflected light in which the modulated light is reflected by the object has a time difference with respect to the light emission waveform 110, and thus becomes a waveform delayed by a phase difference φ with respect to the light emission waveform 110. On the other hand, the control signals TG1 and TG2 are driven by rectangular waves having different phases by 90 degrees. The digital signal processing circuit 12 repeats the sequence driven by the control signals TG1-1 and TG2-1 (drive waveforms 111 and 121) in a cycle of several tens to several hundreds of thousands of times, and then generates information on the charges Q1 and Q2 generated. Acquire (charge voltage converted voltage value). Thereafter, the digital signal processing circuit 12 repeats the sequence driven by the control signals TG1-2 and TG2-2 (the drive waveforms 112 and 122) in a cycle of several tens to several hundreds of thousands of times similarly, and generates the charge Q3. Get Q4, information. Then, the digital signal processing circuit 12 calculates the phase difference θ according to the following arithmetic expression (1) using the discrete Fourier transform (DFT) from the acquired Q1 to Q4.

θ = tan ⁻¹ [(Q ¹ -Q 3) / (Q 2 -Q 4)] (1)
Although the equation (1) is an equation for calculating the phase difference based on the four samplings, it is possible to calculate the phase difference θ according to the following equation (2) even for a general N phase.

θ = tan ⁻¹ [(ΣQk * sin (2π / N * k)) / (ΣQk * cos (2π / N * k))] (2)
FIG. 4 is a sequence of differential outputs. The difference detection circuit 10 repeats the combination of the control signals TG1 and TG2, for example, the control signals TG1-1 (drive waveform 111) and TG2-1 (drive waveform 121) several tens to several hundreds of thousands of digital values D1 (201) Generate Similarly, the difference detection circuit 10 generates a digital value D2 (202) from the control signals TG1-2 (drive waveform 112) and TG2-2 (drive waveform 122), and generates a control signal TG1-3 (drive waveform 113). , And TG2-3 (drive waveform 123) to generate a digital value D3 (203), and control signals TG1-4 (drive waveform 114) and TG2-4 (drive waveform 124) to generate a digital value D4 (204). In this case, the difference detection circuit 10 outputs the digital values D1 to D4 as values from which the DC component has been removed. When the control signal TG1 is "H" and TG2 is "L" for each digital value D1 to D4, "1" is assigned, and the control signal TG1 is "L" and TG2 is "H" When assigning "-1", it describes. That is, the states of the control signals TG1 and TG2 are uniquely determined depending on whether the value of the waveform Dx is “1” or “−1”. Since Dx is a signal indicating the difference between the two storage capacitors 15a and 15b as described above, the AD conversion circuit 11 outputs the signal on which the operation corresponding to the numerator or denominator of the arithmetic expression (1) described above is performed. Output.

  Now, in such a phase-type optical flying distance measuring apparatus 1, it is required to extend the dynamic range, assuming that it is used on a vehicle or the like as described in [Background Art]. Hereinafter, the method of extending the dynamic range according to the present invention will be described.

  FIG. 5 illustrates the inventive concept. The present invention divides the basic exposure period corresponding to the long-term accumulation period of the prior art into a plurality of sub-exposure periods to obtain the distance measurement value of the short-time exposure, and to obtain the exposure of the prior art (long-time exposure Long-distance distance measurement equivalent to. FIG. 6 shows a sequence for realizing the conventional four-phase distance measurement exposure with two divisional sub-exposures, and FIG. 7 shows its timing chart. By driving the sub-exposures 1 and 2 with a 25% duty waveform, repeating the sub-exposures 1 and 2 the same number of times several tens to several hundreds of thousands times, and accumulating the charges between the sub-exposures without resetting. It realizes charge accumulation equivalent to the prior art exposure. A distance measurement value for short-time exposure can be obtained (rapidly updated) from the charge amount of the charge accumulated in one round period in which a plurality of sub-exposure periods divided in this way make one cycle. Further, it is possible to acquire the distance measurement value of long time exposure by integrating the charge amounts of the charges accumulated in a plurality of one round periods. That is, by devising the timing at which the charge (output value) stored in one pixel (the same pixel) is read out, both the distance measurement value for short exposure and the distance measurement value for long exposure from one pixel The dynamic range can be expanded.

  FIG. 8 shows the principle of obtaining range values from two sub-exposures. As a premise, there is a prior art for performing 4 capacitance / 4 phase ranging apart from the prior art for performing 2 capacitance / 4 phase ranging shown in FIG. 31 described above. Comparing the sequence of FIG. 6 that realizes the conventional four-phase ranging exposure with two divisional sub-exposures and the sequence of the prior art that performs four-volume / four-phase ranging, sub-exposure 1 shown in FIG. The exposure corresponds to the exposure of 0 degree-180 degrees of the sequence performing 4 volumes / 4 phase ranging, and the sub-exposure 2 corresponds to 90 degrees-270 degrees of the sequence performing 4 volumes / 4 phase ranging. This corresponds to the numerator and denominator of the following arithmetic expression (3) for calculating the phase difference θ of four-phase ranging.

したがって、サブ露光１のサンプリング値とサブ露光２のサンプリング値との比を計算し、そのアークタンジェントを計算することにより、位相差を計算することが可能になる（演算式（３）は演算式（１）と等価になる）。

Therefore, the phase difference can be calculated by calculating the ratio between the sampling value of sub-exposure 1 and the sampling value of sub-exposure 2 and calculating the arc tangent (equation (3) is equation) Equivalent to (1)).

  FIG. 8 shows the case where the sub-exposure is based on four phases, but the same concept holds true for general N (N is a natural number) phase. In general, an arithmetic expression of discrete Fourier transform is given by the following arithmetic expression (4).

位相型の飛行型測距で主に使用されるのは１次成分であり、演算式（４）は以下の演算式（５）で与えられる。

The first-order component is mainly used in phase-type flying-type distance measurement, and the equation (4) is given by the following equation (5).

ここで、Ｎを２の倍数に限定し、Ｎ＝２Ｍとすると、演算式（５）は以下の演算式（６）で与えられる。

Here, if N is limited to a multiple of 2 and N = 2M, the arithmetic expression (5) is given by the following arithmetic expression (6).

よって、分割したサブ露光がａ_ｊ−ａ_{Ｎ／２+ｊ}となるようにサブ露光の駆動波形を決定することで、任意の分割の仕方について本発明の原理に基づく階層的な測距が成立する。具体的には、１，−１の波形の関係は位相差で１８０度となるように駆動波形を決定する。

Therefore, hierarchical distance measurement based on the principle of the present invention is established for an arbitrary division method by determining the drive waveform of the sub-exposure so that the divided sub-exposure is a _j -a _{N / 2 + j.} Do. Specifically, the drive waveforms are determined such that the relationship between the waveforms of 1 and -1 is 180 degrees in phase difference.

In the sequence of FIG. 6 in which the conventional four-phase distance measurement exposure is realized by two sub-exposures, there are, for example, the following first to third methods as a method of realizing “0”.
In the first method, as shown in FIG. 9, “0” is realized by providing a period in which the modulation switches 14a and 14b are simultaneously turned on, ie, a period in which both TG1 and TG2 are “H”. Charges generated in the PD 13 in a period in which both TG1 and TG2 are "H" are divided into Qa and Qb and stored in the storage capacitors 15a and 15b, and Qa and Qb become equal values. Therefore, this component is canceled by the CM component removal circuit 7 and the difference detection circuit 10, and as a result, the AD conversion circuit 11 outputs "0".

  In the second method, as shown in FIG. 10, a modulation switch 14c different from the modulation switches 14a and 14b is provided, and the modulation switches 14a and 14b are simultaneously turned off and another modulation switch 14c is turned on, that is, A period in which both TG1 and TG2 are "L" and TG3 is "H" is provided to realize "0". The charge generated in the PD 13 in the period when both TG1 and TG2 become "L" and TG3 becomes "H" is discarded to a fixed potential (for example, VDD).

  In the third method, as shown in FIG. 11, one of Qa and Qb is discarded, and two samples are integrated to realize “0”. That is, the cycle in which TG2 discards the charge accumulated in the "H" period and the cycle in which TG1 discards the charge accumulated in the "H" period are integrated. In the first method described above, it is necessary to provide a period in which both TG1 and TG2 are "H", and in the second method it is necessary to provide a period in which both TG1 and TG2 are "L". The method 3 does not have to provide such a period, it suffices to perform control to reverse TG1 and TG2 to each other, and has an advantage of requiring only simple control.

  FIG. 12 shows a sequence for realizing the conventional four-phase distance measurement exposure with four divided sub-exposures. In this case, activating the sub-exposure with a waveform with a duty of 12.5% is equivalent to the conventional 8 capacitance / 8 phase ranging. FIG. 13 shows another sequence for realizing the conventional four-phase ranging exposure with four-division sub-exposure. In this case, the sub-exposure is activated with a 37.5% duty waveform. In FIG. 12, in order to make the SNR (signal-to-noise ratio) of long-term accumulation equal to that of the prior art, the exposure time needs to be quadrupled, but in FIG. By making the time during which the signal is integrated longer than in the sequence shown in FIG. 12, the SNR can be improved without the need to quadruple the exposure time. FIG. 14 shows still another sequence for realizing the conventional four-phase ranging exposure with four-segment sub-exposure. In this case, the sub-exposure is started with a 50% duty waveform. In FIG. 12 and FIG. 13, although it is necessary to perform control to insert "0", in FIG. 14, although SNR obtained in the same exposure time is inferior to the sequence shown in FIG. It can be unnecessary.

  FIG. 15 shows a circuit diagram of a part of the distance measurement value acquisition circuit 8 which is a subsequent stage of the light receiving element 6 using an analog memory, and FIG. 16 shows a timing chart of its operation. The distance measurement value acquiring circuit 8 includes buffers 9a and 9b, reset switching elements 21a and 21b, and selector switching elements 22a and 22b for the light receiving element 6 (PD 13, modulation switches 14a and 14b, and storage capacitors 15a and 15b). Is connected. The buffers 9a and 9b, the switching elements 21a and 21b, and the switching elements 22a and 22b are each configured of, for example, a field effect transistor (FET). The analog differential signal processing circuit 23 differentially reads the charge amount from the light receiving element 6, and outputs an output signal to the analog memory 24 and the difference calculation circuit 25. The analog memory 24 holds the output value of the input output signal when the output signal is inputted from the analog differential signal processing circuit 23, and when the next output signal is inputted, the output signal including the held output value is held. It is output to the difference calculation circuit 25. The difference calculation circuit 25 subtracts the output value of the output signal input from the analog memory 24 from the output value of the output signal input from the analog differential signal processing circuit 23 to calculate and output the difference. That is, the distance measurement value acquisition circuit 8 outputs an output signal directly output from the analog differential signal processing circuit 23 as a distance measurement value for long time exposure, and measures an output signal output from the difference calculation circuit 25 for short time exposure. Output as distance value. In the configuration in which the difference is calculated by such an analog circuit, the increase in the circuit area and the influence of noise become a problem as compared with the configuration in which the difference is calculated by a digital circuit described later, but the influence of the quantization error can be suppressed. .

  FIG. 17 shows a circuit diagram in which a part of the distance measurement value acquisition circuit 8 which is the subsequent stage of the light receiving element 6 is configured using a digital memory, and FIG. 18 shows a timing chart of its operation. The AD conversion circuit 11 differentially reads out the charge amount from the light receiving element 6 to perform AD conversion, and outputs an output signal to the digital memory 31 and the difference calculation circuit 32. When the digital memory 31 receives an output signal from the AD conversion circuit 11, it holds the output value of the input output signal, and when the next output signal is input, the output signal including the held output value is a difference calculation circuit Output to 32. The difference calculation circuit 32 subtracts the output value of the output signal input from the digital memory 31 from the output value of the output signal input from the AD conversion circuit 11, and calculates and outputs a difference. That is, the distance measurement value acquisition circuit 8 outputs an output signal directly output from the AD conversion circuit 11 as a distance measurement value for long time exposure, and an output signal output from the difference calculation circuit 32 as a distance measurement value for short time exposure. Output. In the configuration in which the difference is calculated by such a digital circuit, the influence of the quantization error becomes a problem as compared with the configuration in which the difference is calculated by the above-described analog circuit, but the influence of the circuit area and noise can be suppressed.

Next, control of sub-exposure and control of long-time exposure will be described.
FIG. 19 shows a timing chart for performing rolling reset and rolling readout. In the timing chart of FIG. 19, since a time during which no row is read (time for exposure time adjustment) is provided, the long-time storage time does not have to be a multiple of the number of read rows. Further, since the charge obtained by long time exposure is accumulated with the capacity for each pixel, the analog differential signal processing circuit 23 and the analog memory 24 shown in FIG. 15 and the AD conversion circuit 11 and the digital memory shown in FIG. 31 may be provided for each column.

  FIG. 20 shows another timing chart for performing rolling reset and rolling readout. In the timing chart of FIG. 19 described above, the sequence of sub-exposure is stopped before and after the exposure time of the rolling shutter, but if no influence such as charge flow to peripheral pixels occurs, the exposure is globalized. The same drive waveform may be used, and only read may be realized by rolling reset.

  FIG. 21 shows a timing chart for performing global reset and rolling readout. In global reset, it is necessary to hold the values of all the pixels in the memory, so the circuit scale increases, but it is possible to suppress the problem (so-called focal plane distortion) associated with not being able to secure simultaneousness of exposure for each row. it can.

  FIG. 22 shows another timing chart for performing global reset and rolling readout. By using a global shutter for long-term accumulation and a rolling shutter for short-term accumulation, it is possible to obtain an output having almost no focal plane distortion on the long-term accumulation side. Also in this case, the analog differential signal processing circuit 23 and the analog memory 24 shown in FIG. 15 and the AD conversion circuit 11 and the digital memory 31 shown in FIG. 17 may be provided for each column.

  FIG. 23 shows still another timing chart for performing global reset and rolling readout. When the frame rate on the sub-exposure side is regulated by the readout time of the pixel, the frame rate can be increased by thinning out and reading the rolling shutter of the sub-exposure. If the distance from the own device to the object is short or the object is a high reflectance object, there is a high possibility of being measured across multiple lines, so this configuration is less likely to be a problem .

Next, control for optimizing the amplitude (readout output value) for each pixel of the long-time accumulation output will be described.
FIG. 24 shows a timing chart for optimizing the amplitude for each pixel of the long-time accumulation output. In the example shown in FIG. 24, the exposure is repeated for the pixels in the rows other than the second row because the amplitude is insufficient when the second round of reading is performed. Since the amplitude was sufficient when the second round reading was performed, the exposure was stopped in the second round. Since the exposure control line is common to the rows, the average value, the maximum value or the minimum value of the corresponding row is used to determine whether the amplitude is sufficient or not.

  FIG. 25 shows another timing chart for optimizing the pixel-by-pixel amplitude of the long-term accumulation output. By inserting a reset for each pixel with respect to a pixel having a high sub-exposure output value, control is performed so that the charge of the final long-time exposure is not saturated. In the example of FIG. 25, reset is inserted for the second row of pixels.

  FIG. 26 shows still another timing chart for optimizing the pixel-by-pixel amplitude of the long-term accumulation output. Although FIG. 25 mentioned above is a case where rolling reset is applied, also in the case where global reset is applied, reset may be inserted for each pixel with respect to a pixel having a high sub-exposure output value.

  FIG. 27 shows a circuit diagram that enables adaptive reset for each pixel, and FIG. 28 shows its wiring. In this case, in addition to the buffers 9a and 9b, the reset switching elements 21a and 21b, and the selector switching elements 22a and 22b in the light receiving element 6, the distance measurement value acquisition circuit 8 switches the column reset switching elements 23a and 23b. The switching elements 24a and 24b for the selectors are connected. In the sequence shown in FIG. 25 and FIG. 26, it is possible to select whether to reset for each pixel while maintaining the configuration in which the control line for exposure control is common among the rows. By setting both the SEL line and the CRST line to “H”, only that pixel can be reset, so that it is possible to reset only the pixel with the largest amplitude in the row being read.

  FIG. 29 shows another circuit diagram that enables adaptive reset for each pixel, and FIG. 30 shows its wiring. In the configuration of FIG. 27, the reset for each row can be performed by setting all the CRST lines to "H" simultaneously, so the RST lines become redundant. That is, in FIG. 29, the RST line in the configuration of FIG. 27 is omitted.

As described above, according to the present embodiment, the following effects can be obtained.
In the light flight type distance measuring apparatus 1, the basic exposure period corresponding to the conventional long-time accumulation is divided into a plurality of sub-exposure periods, and accumulated in the sub-exposure period within one cycle period in which the plurality of sub-exposure periods make one cycle. Hold the stored charge without resetting it. Then, the distance measurement value for short exposure is acquired from the charge amount of the charge accumulated in one cycle period, and the charge amount of the charge accumulated in a plurality of one cycle period is integrated to perform long time exposure By acquiring the distance measurement value, both of the distance measurement value for long time exposure and the distance measurement value for short time exposure are acquired from one pixel (the same pixel). As a result, the dynamic range can be expanded without being restricted by the receiving condition of the reflected light, the design of the light receiving optical system, and the arrangement of the pixels. In particular, it is suitable in the case of an on-vehicle in which at least one of the own apparatus and the target moves.

The present invention is not limited only to the above-described embodiment, and can be modified or expanded as follows.
It may be applied to uses other than in-vehicle use.

  In the drawing, 1 is a light flight type distance measuring apparatus, 3 is a drive circuit (drive means), 4 is a light emitting element, 5 is a control circuit (control means), 6 is a light receiving element, 8 is a distance measurement value acquisition circuit (distance measurement) Value acquisition means), 11 AD conversion circuit, 14a, 14b modulation switch, 14c another modulation switch, 15a, 15b storage capacitance, 23 analog differential signal processing circuit 24, 24 analog memory, 25 difference calculation A circuit 31 is a digital memory, and 32 is a difference calculation circuit.

Claims (13)

A light emitting element (4) for emitting in space a modulated light modulated by a pattern having a repetitive period;
Driving means (3) for driving the light emitting element;
A light receiving element (6) for distributing charges corresponding to incident light including reflected light obtained by reflection of modulated light by an object by means of a plurality of modulation switches (14a, 14b) and accumulating them in a plurality of storage capacitors (15a, 15b);
Control means (5) for controlling the drive of the plurality of modulation switches;
And distance measurement value acquisition means (8) for calculating a distance from the own device to an object using the values sampled by the light receiving element to acquire a distance measurement value.
The light receiving element distributes the charge according to the incident light including the reflected light that the modulated light is reflected by the object by using two modulation switches, and stores the charge in two storage capacitors.
Wherein the control means controls the driving of the plurality of modulated switches basic exposure period to the split to so that a plurality of sub-exposure periods, a plurality of sub-exposure periods in the sub-exposure period in one-round periods 1 round And the control signal for driving one of the two modulation switches is H and the control signal for driving the other is L as a basic exposure pattern in the basic exposure period. A period is defined as 1 and a period in which the control signal for driving one is L and the control signal for driving the other is H is defined as -1, and the sub-exposure pattern in the sub-exposure period is 1 Divide the period of 1 and the period of -1 into n (n is a natural number of 2 or more) so that the period and the period of -1 are 180 degrees out of phase, and insert 0 in the period of neither 1 nor -1. And
The distance measuring value acquisition means may acquire a distance value of the short time exposure from the charge amount of charges accumulated in the one-round period, accumulated charge amount of the plurality of charge stored in the one-round period An optical flight distance measuring apparatus (1) characterized in that a long exposure distance measurement value is acquired. In the optical flight type distance measuring apparatus according to claim 1 ,
Before SL control means in the sub exposure pattern, by a control signal for driving the two modulation switch each provide a period both H, the light flight distance measuring apparatus characterized by inserting a 0. In the optical flight type distance measuring apparatus according to claim 1,
The light receiving element has a modulation switch (14c) different from the two modulation switches.
The control means inserts 0 by providing a period in which the control signals for driving the two modulation switches are both L and the control signals for driving the other modulation switches are H in the sub-exposure pattern. An optical flying distance measuring apparatus characterized by In the optical flight type distance measuring apparatus according to claim 1 ,
The control means inverts and controls a control signal for driving the two modulation switches in a sub-exposure pattern, and a cycle for discarding the charge stored in one of the two storage capacitors, and the two storage capacitors An optical flight distance measuring apparatus characterized in that 0 is inserted by integrating with the cycle of discarding the charge accumulated in the other . The optical flight distance measuring apparatus according to any one of claims 1 to 4 .
Before SL control means in the sub exposure pattern, the cycle of the basic exposure periods when T, the light-flight, characterized in that the first period and the duration of -1 longer than T / (2n), respectively Distance measuring device. The optical flight distance measuring apparatus according to any one of claims 1 to 5 , wherein
The distance measurement value acquisition means includes an analog differential signal processing circuit (23) for differentially reading out the charge amount from the light receiving element, and an analog memory (24) for holding an output value of the analog differential signal processing circuit. The current output value output from the analog differential signal processing circuit at the current output timing and the output signal one cycle before from the analog differential signal processing circuit are held one by one in the analog memory a difference calculation circuit for calculating a difference between the output value (25), the light-flight distance measuring apparatus characterized by having a. In the optical flight distance measuring apparatus according to claim 6 ,
The light flight type distance measuring apparatus characterized in that the distance measuring value acquiring means is realized by a switched capacitor circuit . The optical flight distance measuring apparatus according to any one of claims 1 to 5 , wherein
The distance measuring value acquisition unit, an AD conversion circuit (11) for AD converting the charge amount from the light receiving element is read out differentially, a digital memory (31) for holding an output value of the AD conversion circuit, The difference between the current output value output from the AD conversion circuit at the current output timing and the previous output value output from the AD conversion circuit at the immediately preceding output timing and held in the digital memory And calculating a difference calculation circuit (32) . The optical flight distance measuring apparatus according to any one of claims 1 to 8 ,
The light flying distance measuring apparatus , wherein the control means performs control of sub-exposure and control of long-time exposure which repeats a plurality of sub-exposures by rolling reset and rolling readout . The optical flight distance measuring apparatus according to any one of claims 1 to 8 ,
The light flying distance measuring apparatus, wherein the control means performs control of sub-exposure and control of long-time exposure which repeats a plurality of sub-exposures together by global reset and rolling readout.

The optical flight distance measuring apparatus according to claim 9 or 10
The light flying distance measuring apparatus is characterized in that the control means selects whether or not to repeat the sub-exposure according to the output value of the sub-exposure read in row units . In the optical flight distance measuring apparatus according to claim 11 ,
The control means uses one of an average value, a maximum value, and a minimum value of the values read in the row to determine whether or not to repeat the sub-exposure depending on the output value of the sub-exposure read in row units. An optical flying distance measuring apparatus characterized in that The optical flight distance measuring apparatus according to any one of claims 9 to 12 ,
The control signal may be reset for each pixel according to the output value of the sub-exposure of the read row .

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