JP7376457B2 - Distance measuring device, distance measuring method, and program - Google Patents

Description

The present invention relates to a distance measuring device and the like.

As a technique for reducing image noise, for example, Patent Document 1 states, ``All image patches belonging to an image patch set are denoised by performing noise reduction processing using different parameters for each image patch. "Generate image patches" is described.

JP2013-26669A

By the way, there is a known technology called the Time-of-Flight method (also called the TOF method), which calculates the distance to the object by irradiating the object with light and performing multiple exposures with light including the reflected light. There is. When such a time-of-flight method is used, multiple imaging signals are obtained through multiple exposures. In order to reduce noise in these multiple imaging signals, when the technology described in Patent Document 1 is used, even for the same pixel (distance measurement position), the noise reduction processing characteristics ( parameters, etc.) will be different. As a result, the error in the measured value of the distance to the object may increase.

Therefore, an object of the present invention is to provide a distance measuring device and the like that appropriately measures the distance to an object.

In order to solve the above problems, the present invention includes a light emitting unit that irradiates a target object with light, and a light emitting unit that receives light including reflected light from the target object a plurality of times with predetermined timing shifts. The distance to the target object is calculated for each pixel based on the Time-of-Flight method using a light receiving unit that accumulates the amount of light received each time, and a plurality of imaging signals corresponding to the plurality of light receptions. and a control unit that performs noise reduction processing to reduce the noise of each of the plurality of imaging signals, and the predetermined noise reduction control signal used for the noise reduction processing The imaging signal is common to each pixel, and the light receiving section receives light in synchronization with the light irradiation by the light emitting section, and after accumulating a first amount of received light, the light irradiation by the light emitting section ends. The control unit receives light from time to time and accumulates a second amount of received light, and the control unit generates a first image signal based on the first amount of received light and a second image signal based on the second amount of received light for each pixel. The noise reduction control signal is generated using a synthesized signal obtained by synthesizing the noise reduction control signal, and the noise reduction control signal indicates the position of the pixel to be subjected to the noise reduction processing among the pixels included in the synthesized signal. and the signal indicates the position of a pixel in the vicinity of the target pixel for which the absolute value of the difference between the pixel value and the pixel value of the target pixel is less than or equal to a predetermined value. do. Note that other details will be explained in the embodiment.

According to the present invention, it is possible to provide a distance measuring device and the like that appropriately measures the distance to an object.

FIG. 1 is a configuration diagram including a distance measuring device according to a first embodiment. FIG. 2 is a functional block diagram including a control unit of the distance measuring device according to the first embodiment. 5 is a time chart regarding a light emission timing control signal, an exposure timing control signal, etc. of the distance measuring device according to the first embodiment. 3 is a time chart of a series of processes executed by the distance measuring device according to the first embodiment. FIG. 2 is an explanatory diagram showing an example in which a composite signal is generated based on a first image signal and a second image signal in the distance measuring device according to the first embodiment. FIG. 3 is an explanatory diagram regarding the generation of a noise reduction control signal in the distance measuring device according to the first embodiment. FIG. 7 is an explanatory diagram regarding the generation of a noise reduction control signal for pixels at the edge of an input image in the distance measuring device according to the first embodiment. FIG. 3 is an explanatory diagram of noise reduction processing executed by the noise reduction control unit of the distance measuring device according to the first embodiment. FIG. 7 is an explanatory diagram of processing performed by a noise reduction control unit on pixels at an edge in the distance measuring device according to the first embodiment. FIG. 2 is a functional block diagram including a control unit of a distance measuring device according to a second embodiment. It is a time chart regarding the light emission timing control signal, the exposure timing control signal, etc. of the distance measuring device based on 2nd Embodiment. It is a time chart of a series of processes executed by the distance measuring device according to the second embodiment. FIG. 7 is an explanatory diagram showing an example in which a composite signal is generated based on a first image signal, a second image signal, and a third image signal in the distance measuring device according to the second embodiment. It is a functional block diagram including a control part of a distance measuring device concerning a 3rd embodiment.

≪First embodiment≫
<Configuration of distance measuring device>
FIG. 1 is a configuration diagram including a distance measuring device 100 according to the first embodiment.
A distance measuring device 100 shown in FIG. 1 is a device that measures the distance to an object J (subject). As shown in FIG. 1, the distance measuring device 100 includes a light emitting section 1, a light receiving section 2, a reference clock generation section 3, a storage section 4, a control section 5, and a distance image output section 6. There is.

The light emitting unit 1 has a function of irradiating the object J with light. That is, the light emitting unit 1 irradiates the object J with predetermined pulse-modulated light based on the light emission timing control signal S0 input from the imaging control unit 51. As such a light emitting unit 1, for example, an LED (Light Emitting Diode) or a laser diode is used.

The light receiving unit 2 receives light including reflected light from the object J a plurality of times with predetermined timing shifts, and accumulates the amount of light received for each of the plurality of light receptions. That is, the light receiving section 2 performs exposure with light including reflected light from the object J based on the exposure timing control signals S1 and S2 inputted from the imaging control section 51.

The light receiving section 2 includes a pixel circuit 21 in which a plurality of pixels are arranged in a matrix. As such a pixel circuit 21, for example, a CCD (Charge Coupled Device) image sensor circuit or a CMOS (Complementary Metal-Oxide Semiconductor) image sensor circuit is used. Specifically, the light receiving unit 2 includes a photodiode (not shown) that is associated with each pixel on a one-to-one basis, a plurality of capacitors connected to the photodiode, and a plurality of photodiodes that convert charges photoelectrically in the photodiode. MOS transistors (not shown) for distributing predetermined distribution to the capacitors. In addition to the drive circuit that drives the MOS transistors based on the exposure timing control signals S1 and S2 from the imaging control unit 51, the light receiving unit 2 converts the analog value of the charge amount (that is, the amount of light received) of each capacitor into a digital value. It is equipped with an A/D converter (not shown) for converting into

The reference clock generation unit 3 is, for example, a crystal oscillator, and generates a reference clock signal at a predetermined clock frequency. The reference clock signal generated by the reference clock generation section 3 is output to the imaging control section 51.
The storage unit 4 appropriately stores various programs and parameters as well as calculation results of the control unit 5 and the like. For example, a flash memory is used as such a storage unit 4, but it is not limited to this.

The control unit 5 calculates the distance to the object J based on the Time-of-Flight method using a plurality of imaging signals (first imaging signal M1, second imaging signal M2) corresponding to light reception performed multiple times. Performs calculation processing (arithmetic processing) for each pixel. Although not shown, the control unit 5 is configured to include electronic circuits such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and various interfaces. Then, the program stored in the ROM is read out and expanded to the RAM, and the CPU executes various processes.

As shown in FIG. 1, the control section 5 includes an imaging control section 51. The imaging control unit 51 generates the light emission timing control signal S0 and the exposure timing control signals S1 and S2 based on the reference clock signal described above. Note that processing based on the light emission timing control signal S0 and the exposure timing control signals S1 and S2 will be described later.
The distance image output unit 6 is a predetermined interface circuit, and outputs data indicating the distance for each pixel calculated by the control unit 5 to the display device 200 as a predetermined distance image.

FIG. 2 is a functional block diagram including the control unit 5 of the distance measuring device 100.
As shown in FIG. 2, the control section 5 includes, in addition to the above-described imaging control section 51 (see also FIG. 1), a synthesis section 52, a smoothing section 53, a noise reduction control signal generation section 54, and a first noise control signal generation section 54. It includes a reduction section 55, a second noise reduction section 56, and a distance calculation section 57.
The imaging control section 51 includes a light emission control section 51a and an exposure control section 51b. The light emission control section 51a generates a light emission timing control signal S0 that specifies the timing of emitting light from the light emitting section 1 at a predetermined period. The exposure control section 51b generates exposure timing control signals S1 and S2 at a predetermined period, which specify the timing at which the light receiving section 2 is exposed to light.

FIG. 3 is a time chart regarding the light emission timing control signal S0, the exposure timing control signals S1, S2, etc. (see FIGS. 1 and 2 as appropriate).
Note that the light emission timing control signal S0 and the exposure timing control signals S1 and S2 shown in FIG. 3 are as described above. “Reflected light from the object” shown in FIG. 3 indicates the timing at which the light emitted from the light emitting unit 1 is reflected by the object J and the light including the reflected light reaches the light receiving unit 2.

The “charge amount Q1” shown in FIG. 3 is the amount of charge (that is, the amount of received light) stored in a capacitor (not shown) when the light receiving unit 2 photoelectrically converts the light received by the exposure timing control signal S1. It is. The "charge amount Q2" shown in FIG. quantity).

In the example of FIG. 3, a pulsed light emission timing control signal S0 is output from the light emission control section 51a (see FIG. 2) to the light emission section 1 (see FIG. 2) during the period from time t1 to time t3. As a result, although not shown, pulsed light having a pulse width of a predetermined time T0 is emitted from the light emitting unit 1 toward the object J (see FIG. 1) during the period from time t1 to time t3. Then, the reflected light from the object J reaches the light receiving section 2 with a delay of a predetermined delay time Td after the light is emitted from the light emitting section 1 . This delay time Td is proportional to the distance from the object J to the light receiving section 2. Note that it is assumed in advance that the delay time Td is less than the predetermined time T0.

The exposure timing control signal S1 is output from the exposure control section 51b (see FIG. 2) to the light receiving section 2 (see FIG. 2) during a period from time t1 to t3 in synchronization with the light emission timing control signal S0. Between times t1 and t3 when the exposure timing control signal S1 is in the ON state, the light receiving unit 2 photoelectrically converts the light it receives using a photodiode (not shown), and transfers the charge generated by this photoelectric conversion to a capacitor. (not shown). Such processing is performed in each pixel of the light receiving section 2.

The other exposure timing control signal S2 is transmitted from the exposure control section 51b (see FIG. 2) to the light receiving section 2( (see Figure 2). Note that the predetermined time T0 during which the exposure timing control signal S2 is in the ON state is equal to the predetermined time T0 during which the light emission timing control signal S0 and the exposure timing control signal S1 are in the ON state.

Between times t3 and t5 when the exposure timing control signal S2 is in the ON state, the light receiving section 2 photoelectrically converts the light it receives using a photodiode (not shown), and separates the charge generated by this photoelectric conversion. is stored in a capacitor (not shown). Such processing is performed in each pixel of the light receiving section 2.

That is, the light receiving section 2 receives light in synchronization with the light irradiation by the light emitting section 1, accumulates the amount of charge Q1 (first amount of received light), and then receives light from the end of the light irradiation by the light emitting section 1. A charge amount Q2 (second received light amount) is accumulated. In the example of FIG. 3, the entire amount of light received by the light receiving section 2 is divided at time t3, and distributed as charge amounts Q1 and Q2 including reflected light components. Then, the control unit 5 calculates the distance to the object J for each pixel based on digital values obtained by A/D converting the electric charges Q1 and Q2. This distance calculation method is called a time-of-flight method. As shown in FIG. 3, the electric charges Q1 and Q2 include not only a reflected light component derived from the reflected light from the object J, but also an external light component derived from background light and the like.

FIG. 4 is a time chart of a series of processes executed by the distance measuring device (see FIGS. 2 and 3 as appropriate).
Note that in FIG. 4, illustration of delay time between each process is omitted for convenience. As described above, the control unit 5 (see FIG. 2) turns on the light emission timing control signal S0 to cause the light emitting unit 1 to emit light (light emission processing), and also controls the exposure timing in synchronization with the light emission timing control signal S0. Turn on signal S1. Then, the control unit 5 turns on the exposure timing control signal S2 from the time when the light emission timing control signal S0 and the exposure timing control signal S1 are turned off. As a result, light including reflected light from the object J is received by the light receiving section 2 (light receiving processing). Note that each process after the exposure timing control signal S2 is turned off will be described later.

The explanation will be continued by returning to FIG. 2 again.
The control unit 5 performs a predetermined A/D conversion on the charge amount Q1 based on the exposure timing control signal S1, and generates the first imaging signal M1 (see also FIG. 4). This first image pickup signal M1 is data indicating the pixel value (digital value of the amount of charge Q1) of each pixel arranged in a matrix, and includes the position of each pixel and its pixel value. As shown in FIG. 2, the first image signal M1 is output from the light receiving section 2 to the combining section 52, and is also output to the first noise reduction section 55.

Similarly, the control unit 5 performs a predetermined A/D conversion on the charge amount Q2 based on the exposure timing control signal S2, and generates the second imaging signal M2 (see also FIG. 4). This second image pickup signal M2 is data indicating the pixel value (digital value of the amount of charge Q2) of each pixel arranged in a matrix, and includes the position of each pixel and its pixel value. As shown in FIG. 2, the second image pickup signal M2 is output from the light receiving section 2 to the combining section 52, and is also output to the second noise reduction section 56.

Note that various noises such as shot noise caused by fluctuations in the number of photons of light incident on the light receiving section 2 are present in the first image signal M1 and the second image signal M2. Therefore, in the first embodiment, the control unit 5 performs a predetermined noise reduction process to reduce noise in each of the plurality of imaging signals (first imaging signal M1, second imaging signal M2).

The combining unit 52 shown in FIG. 2 combines the first image signal M1 and the second image signal M2 for each pixel. That is, the synthesis unit 52 performs the following calculation (Equation 1) for each pixel, and generates a predetermined synthesis signal that uses the calculation result as a pixel value for each pixel ("synthesis processing" in FIG. 4). Note that the value α in (Formula 1) is a predetermined value larger than 0 and smaller than 1, and is set in advance.

(Synthetic signal) = (first image signal) x α + (second image signal) x (1 - α) ... (Formula 1)

FIG. 5 is an explanatory diagram showing an example in which a composite signal is generated based on the first imaging signal M1 and the second imaging signal M2.
FIG. 5 shows an example in which the pixels of the light receiving section 2 are arranged in a 5×5 matrix. Moreover, FIG. 5 shows a case where the value α of the above-mentioned (Formula 1) is 0.5. For example, the pixel value of the center pixel in the first image pickup signal M1 is 135. On the other hand, the pixel value of the center pixel in the second image pickup signal M2 is 153. The synthesizing unit 52 performs the calculation 135×0.5+153×(1−0.5)=144 based on the above-mentioned (Equation 1), and determines the pixel value of the center pixel after synthesis. Similarly, for other pixels, the combining unit 52 calculates the combined pixel values.

The synthesized signal (image data indicating the position and pixel value of the pixel after synthesis) generated in this way is transferred from the synthesizing section 52 to the smoothing section 53 (see FIG. 2) as data indicating the luminance distribution of the received light. is output to.

The smoothing unit 53 smoothes the composite signal using a predetermined filter (“smoothing process” in FIG. 4), and outputs the smoothed composite signal to the noise reduction control signal generation unit 54. Note that as a filter for the smoothing process, a Gaussian filter or a median filter can be used in addition to the average filter. Furthermore, the filter for smoothing processing may have a size of 3×3, or may have a size of 5×5 or 7×7.

By performing the predetermined filter processing by the smoothing unit 53 in this way, even when the S/N ratio of the composite signal is relatively small (for example, the S/N ratio is smaller than 1), the pixel value of each pixel can be changed. The original distribution becomes roughly clear. Therefore, the control unit 5 can appropriately generate a noise reduction control signal, which will be described later.

The noise reduction control signal generation unit 54 generates a predetermined noise reduction control signal based on the smoothed composite signal (image data) input from the smoothing unit 53 (“Noise reduction control signal generation” in FIG. 4). process"). Here, the noise reduction control signal is used to identify neighboring pixels that have a high correlation with the target pixel (that is, the difference in pixel values is relatively small) in order to reduce the noise of each pixel. It's a signal.

FIG. 6 is an explanatory diagram regarding the generation of the noise reduction control signal (see also FIG. 2 as appropriate).
The "input image" shown on the left side of the paper in FIG. 6 is image data (smoothed composite signal) input from the smoothing section 53 to the noise reduction control signal generation section 54. Further, f(i, j) is the pixel value of the pixel whose position is indicated by (i, j).

As shown on the left side of the paper in FIG. The pixel value f(i+m, j+n) is obtained. Here, the values m and n are integers greater than or equal to -1 and less than or equal to 1. Note that in this embodiment, the size of the area is 3×3, but it may be 5×5 or 7×7. For example, if the area size is 5×5, the values m and n are integers greater than or equal to −2 and less than or equal to 2.
Next, as shown in FIG. 6, the noise reduction control signal generation unit 54 subtracts the pixel value f(i,j) from the pixel value f(i+m,j+n), and calculates the absolute value of the subtracted value |f(i+m , j+n)−f(i,j)|

Then, the noise reduction control signal generation unit 54 performs the following calculation (Equation 2). Note that the pixel (i, j) included in (Formula 2) corresponds to the shooting point (measurement position) of the first image pickup signal M1 and the second image pickup signal M2. Further, the predetermined value k is a threshold value that serves as a criterion for determining whether the pixel value after the binarization process is set to "1" or "0", and is set in advance. In the example of FIG. 6, the predetermined value k=40. Furthermore, b _i,j (m, n) included in (Formula 2) is a noise reduction control signal generated by the noise reduction control signal generation section 54.

When |f(i+m,j+n)−f(i,j)|≦k, b _i,j (m,n)=1
When |f(i+m,j+n)−f(i,j)|>k, b _i,j (m,n)=0
...(Formula 2)

That is, when the absolute value |f(i+m,j+n)−f(i,j)| is less than or equal to the predetermined value k, the noise reduction control signal generation unit 54 generates the noise reduction control signal b _i,j (m,n) Assign "1" as the value. On the other hand, if the absolute value |f(i+m,j+n)−f(i,j)| is larger than the predetermined value k, the noise reduction control signal generation unit 54 generates the noise reduction control signal b _i,j (m,n) Assign “0” as the value. Through such binarization processing, a pixel with a relatively small difference from the pixel value f(i, j) is extracted from among the 3×3 pixels including the target pixel (i, j). . Then, the noise reduction control signal generation unit 54 outputs the noise reduction control signal b _i,j (m, n) to the first noise reduction unit 55 for each pixel (i, j), and also outputs the noise reduction control signal b i,j (m, n) to the first noise reduction unit 55 . It outputs to section 56.

In this way, the control unit 5 predetermines the first image signal M1 based on the amount of charge Q1 (first amount of received light) and the second image signal M2 based on the amount of charge Q2 (second amount of received light) for each pixel. A noise reduction control signal b _{i,j (m, n) is generated using a composite signal obtained by combining the signals b i,j} (m, n). This noise reduction control signal indicates the position of the pixel (i, j) to be subjected to noise reduction processing among each pixel included in the composite signal, and also indicates the position of the pixel (i, j) in the vicinity of the target pixel (i, j). This signal indicates the position of the pixel value f(i+m, j+n) among the pixel values f(i+m, j+n) and the pixel value f(i, j) of the target pixel for which the absolute value of the difference is less than or equal to a predetermined value. .

FIG. 7 is an explanatory diagram regarding the generation of a noise reduction control signal for pixels at the edge of an input image.
For a pixel existing at the edge of the input image (for example, pixel (0,0) shown in FIG. 7), no pixel exists in a part of the 3×3 neighboring area. In such a case, the noise reduction control signal generation unit 54 copies and supplements the pixel value of the pixel on the edge as the pixel value of a virtual pixel adjacent to the pixel on the edge, and then generates the noise reduction control signal. Generate b _i,j (m, n). Thereby, the noise reduction control signal b _i,j (m, n) can be appropriately generated even for pixels at the edges of the input image.

The first noise reduction unit 55 _shown in FIG. Then, predetermined noise reduction processing is performed. As shown in FIG. 2, the first noise reduction section 55 includes a noise reduction control section 55a.
The other second noise reduction unit 56 uses the noise reduction control signal b _i,j (m, n) for the pixel (i, j) of the second image pickup signal M2 inputted from the light receiving unit 2. Performs predetermined noise reduction processing. As shown in FIG. 2, the second noise reduction section 56 includes a noise reduction control section 56a.
Next, the process executed by the noise reduction control unit 55a of the first noise reduction unit 55 will be described using FIG. 8, but the same applies to the second noise reduction unit 56.

FIG. 8 is an explanatory diagram of the noise reduction process executed by the noise reduction control unit (see also FIG. 2 as appropriate).
Note that the noise reduction control signal b _i,j (m, n) (see also Figure 6). For example, the noise reduction control unit 55a sets the center (0,0) of the 3×3 area of the noise reduction control signal b _i,j (m,n) to the position of the pixel (i,j) of the first image pickup signal M1. Match. The noise reduction control unit 55a then calculates the noise reduction control signal b _i,j (m, n) and the pixel value f (i+m, j+n) of the first image pickup signal M1 based on the following (Formula 3). The pixel values at the positions where the values m and n are common are each multiplied, and the sum P1(i, j) is calculated.

In the example of FIG. 8, the sum P1(i,j)=590. This sum P1 (i, j) is the pixel whose position is indicated by the noise reduction control signal b _i,j (m, n) (that is, the value of b _i,j (m, n) is “1”) is the sum of pixel values f(i+m, j+n). In addition, the noise reduction control unit 55a calculates each of the noise reduction control signals b _i,j (m, n) in the 3×3 area based on the following (Formula 4), in addition to the sum P1 (i, j). Calculate the sum of elements Q1(i,j).

In the example of FIG. 8, the sum Q1(i,j)=5. This sum Q1(i,j) is determined by the pixel whose position is indicated by the noise reduction control signal b _i,j (m,n) (that is, the value of b _i,j (m,n) is "1"). equal to the number of Then, the noise reduction control unit 55a divides the above sum P(i, j) by the sum Q(i, j) based on the following (Equation 5), and calculates the average value within the 3×3 area as follows: It is calculated as the output pixel value O1(i,j).
Note that the noise reduction processing described in this embodiment is for the case where the size of the noise reduction control signal b _i,j (m, n) is 3×3, but the size of the noise reduction control signal b i,j (m, n) is 3×3. It may be. For example, if the size of the noise reduction control signal b _{i,j (} m, n) is 5×5, the center (0, 0 ) is aligned with the position of the pixel (i, j) of the first image pickup signal M1, and then the above calculation is performed. Here, the values m and n are integers greater than or equal to -2 and less than or equal to 2.

In the example of FIG. 8, the output pixel value O1(i,j)=590/5=118. Then, the first noise reduction unit 55 replaces the pixel value of the pixel (i, j) of the first image pickup signal M1 with the output pixel value O1 (i, j) based on (Equation 5). Such processing is called noise reduction processing. Furthermore, the first noise reduction unit 55 performs the above-described noise reduction processing on each pixel included in the first image pickup signal M1 while sequentially shifting the position of the pixel (i, j) (“first noise reduction processing” in FIG. 4). "Image signal noise reduction processing"). The image signal O1 corresponding to the first image signal M1 is output from the first noise reduction section 55 (see FIG. 2) to the distance calculation section 57 (see FIG. 2).

Similarly, the other second noise reduction unit 56 performs noise reduction processing on the second image signal M2 inputted from the light receiving unit 2, and changes the pixel value of the pixel (i, j) of the second image signal M2 to a predetermined value. It is replaced with the output pixel value O2(i,j) ("second image pickup signal noise reduction process" in FIG. 4). This output pixel value O2(i,j) is calculated in the same manner as (Equation 5) described above. The image signal O2 corresponding to the second imaging signal M2 is output from the second noise reduction section 56 (see FIG. 2) to the distance calculation section 57 (see FIG. 2). Note that, as shown in FIG. 4, the first imaging signal noise reduction process and the second imaging signal noise reduction process may be executed in parallel.

In this way, the noise reduction processing performed by the control unit 5 (the first noise reduction unit 55, the second noise reduction unit 56) is performed using the noise reduction control signal b _i in each of the first imaging signal M1 and the second imaging signal M2. _{, j} The average value (P1(i, j)/Q1(i,j)) as a new pixel value.

To put it simply, the first noise reduction unit 55 generates a noise reduction control signal b _i,j (m , n), the average of the pixel values is calculated, and the calculation result is replaced as a new pixel value of the first image pickup signal M1. Note that the same applies to the second noise reduction section 56. Thereby, noise in each signal can be reduced for each pixel of the first image signal M1 and the second image signal M2 based on the correlation with neighboring pixels. As a result, noise in the distance image, which will be described later, is also reduced, and edges in the distance image tend to remain.

Further, a predetermined noise reduction control signal b _i,j (m, n) used for noise reduction processing is common to each pixel in a plurality of imaging signals (first imaging signal M1, second imaging signal M2). There is. In this way, the first imaging signal M1 and the second imaging signal M2, which are captured at different timings, have the same noise reduction processing characteristics, thereby increasing the accuracy of distance measurement.

FIG. 9 is an explanatory diagram of processing performed by the noise reduction control unit on pixels at the edge.
For example, if the center of the noise reduction control signal b _i,j (m, n) is aligned with a pixel at the edge of the input image (in FIG. 9, the image of the first imaged signal M1), noise will occur in the input image. There will be pixels that do not correspond to the reduction control signal b _i,j (m, n). In such a case, the first noise reduction unit 55 copies the pixel value of the pixel at the edge of the input image as the pixel value of the virtual pixel adjacent to the pixel at the edge, as shown in FIG. After the compensation, the output pixel value O1(i,j) is calculated. As a result, the output pixel value O1(i,j) can be appropriately calculated even for pixels at the edges of the input image.

The distance calculation unit 57 shown in FIG. 2 calculates the distance between each pixel (that is, the The distance at each measurement position of the object J is calculated, and a distance image is generated. Specifically, the distance calculation unit 57 uses the output pixel value O1 (i, j) of the image signal O1 and the output pixel value O2 (i, j) of the image signal O2, and calculates the following (Equation 6). ), distance data D(i,j) is generated.

Note that the distance data D (i, j) in (Equation 6) is data indicating the distance to the target object J at the pixel (i, j). Moreover, T0 in (Formula 6) is the pulse width of the light irradiated to the object J (see FIG. 3), and c is the speed of light (3×10 ⁸ [m/s]). Moreover, O1 (i, j) is an output pixel value corresponding to the first image pickup signal M1, and O2 (i, j) is an output pixel value corresponding to the second image pickup signal M2. By calculating (Equation 6), the distance to the object J is calculated for each pixel. The distance data D(i, j) generated in this manner is output from the distance calculation unit 57 to the display device 200 (see FIG. 1) as a distance image. Thereby, the user can grasp the distance from each pixel of the light receiving unit 2 of the distance measuring device 100 to the target object J as a predetermined distance image.

<Effect>
According to the first embodiment, for each of the first imaging signal M1 and the second imaging signal M2 that are acquired at different timings, the control unit 5 sends a common noise reduction control signal to the pixels having the same position. b _i,j (m, n) is used. As a result, errors caused by the characteristic difference (difference in pixel value distribution) between the first imaging signal M1 and the second imaging signal M2 can be reduced for each pixel. Therefore, the distance from each pixel of the light receiving section 2 to the object J can be measured with high precision.

Further, according to the first embodiment, in the composite signal of the first image signal M1 and the second image signal M2, noise reduction control is performed based on the correlation of pixel values (the difference in pixel values with surrounding pixels). The control unit 5 generates the signal b _i,j (m, n) for each pixel. Then, the control unit 5 calculates the average of the pixel values, including the neighboring pixels whose positions are specified by the noise reduction control signal b _i,j (m, n), and calculates the average of the pixel values, Replace the pixel value of signal M2. As a result, noise in each signal is reduced for each pixel based on the correlation with neighboring pixels, so the distance to the object J can be measured with high precision.

Note that to reduce image noise, it is possible to perform image processing such as a low-pass filter, but natural images (images before noise reduction) contain signal components of various textures and edges. . If noise reduction processing with the same characteristics is applied to the entire image, the noise in texture and edge parts with a high signal-to-noise ratio will be reduced while the signal components are sufficiently maintained, but the signal noise will be reduced. Information about textures and edges with small ratios is lost. Furthermore, if it is attempted to leave information on textures or edges with a low signal-to-noise ratio, the effect of noise reduction may be weakened.

On the other hand, in the first embodiment, as described above, the control unit 5 generates a common noise reduction control signal b _i,j ( m, n). Thereby, the distance to the object J can be measured with high precision, and in turn, it is possible to contribute to society by promoting the development of industry.

≪Second embodiment≫
In the second embodiment, when measuring the distance to an object, the control unit 5A (see FIG. 10) sequentially outputs three exposure timing control signals S1, S2, and S3 to the light receiving unit 2 (see FIG. 10). This is different from the first embodiment in that. The second embodiment is different from the first embodiment in that the control unit 5A calculates the distance to the object after removing the external light component from the amount of received light. Note that other points are the same as those in the first embodiment. Therefore, the parts that are different from the first embodiment will be explained, and the explanation of the overlapping parts will be omitted.

FIG. 10 is a functional block diagram including a control unit 5A of a distance measuring device 100A according to the second embodiment.
As shown in FIG. 10, the control unit 5A of the distance measuring device 100A includes an imaging control unit 51, a combining unit 52, a smoothing unit 53, a noise reduction control signal generation unit 54, and a first noise reduction unit 55. , a second noise reduction section 56, a third noise reduction section 58, and a distance calculation section 57. The processing executed by each of these components will be explained using FIG. 11 and the like.

FIG. 11 is a time chart regarding the light emission timing control signal S0, the exposure timing control signals S1, S2, S3, etc. (see also FIG. 10 as appropriate).
As shown in FIG. 11, the control unit 5A turns on the light emission timing control signal S0 for a predetermined time T0, and turns on the exposure timing control signal S1 in synchronization with this light emission timing control signal S0. As a result, a charge amount Q1 is accumulated in a capacitor (not shown) connected to a photodiode (not shown).

Next, the control unit 5A turns on the exposure timing control signal S2 for a predetermined time T0 from the time when the light emission timing control signal S0 and the exposure timing control signal S1 are switched from ON to OFF. As a result, an amount of charge Q2 is accumulated in another capacitor (not shown). Furthermore, the control unit 5A turns on the exposure timing control signal S3 for a predetermined time T0 from the time when the exposure timing control signal S2 is switched from ON to OFF. As a result, the amount of charge Q3 is accumulated in yet another capacitor (not shown).

That is, the light receiving section 2 receives light in synchronization with the light irradiation by the light emitting section 1, accumulates the amount of charge Q1 (first received light amount), and then receives light from the end of the light irradiation by the light emitting section 1. The amount of charge Q2 (second amount of received light) is accumulated, and further, light is received from the end of the reception of the amount of charge Q2, and the amount of charge Q3 (third amount of received light) is accumulated.

In the example of FIG. 11, the electric charges Q1 and Q2 include an external light component in addition to a reflected light component obtained by photoelectrically converting the reflected light from the object. On the other hand, the amount of charge Q3 does not include a reflected light component, but only an external light component. Note that depending on the length of the distance to the object, the delay time Td becomes relatively long, so that the amounts of charge Q2 and Q3 include a reflected light component, while the amount of charge Q1 does not include a reflected light component. Sometimes.

FIG. 12 is a time chart of a series of processes executed by the distance measuring device.
Note that in FIG. 12, illustration of delay time between each process is omitted for convenience. As described above, the control unit 5A (see FIG. 10) turns on the light emission timing control signal S0 to cause the light emitting unit 1 to emit light (light emission processing), and sequentially turns on the exposure timing control signals S1, S2, and S3. (light reception processing).

Then, the control unit 5A performs a predetermined A/D conversion on the charge amount Q1 based on the exposure timing control signal S1, and generates the first imaging signal M1. Similarly, the control unit 5A performs a predetermined A/D conversion on the charge amount Q2 based on the exposure timing control signal S2, and generates the second image pickup signal M2. Further, the control unit 5A performs a predetermined A/D conversion on the charge amount Q3 based on the exposure timing control signal S3 to generate a third image pickup signal M3. Note that each process subsequent to the combining process in FIG. 12 will be described later.

The combining unit 52 shown in FIG. 10 generates a combined signal based on the following (Equation 7). Note that the values α and β included in (Formula 7) are preset as predetermined values greater than 0 and smaller than 1. Further, it is assumed that (α+β)<1.

(Synthetic signal) = (first image signal) x α + (second image signal) x β + (third image signal) x (1 - α - β) (Formula 7)

FIG. 13 is an explanatory diagram showing an example in which a composite signal is generated based on the first imaging signal M1, the second imaging signal M2, and the third imaging signal M3.
In the example of FIG. 13, α=1/3 and β=1/3 in the above-mentioned (Formula 7). The composite signal generated in this manner is output from the combining section 52 (see FIG. 10) to the smoothing section 53 (see FIG. 10) as data indicating the luminance distribution of the received light.

Note that the processing executed by the smoothing section 53 (see FIG. 10) and the noise reduction control signal generation section 54 (see FIG. 10) is the same as in the first embodiment. That is, the control unit 5A generates a first image signal M1 based on the amount of charge Q1 (first amount of received light), a second image signal M2 based on the amount of charge Q2 (second amount of received light), and a second image signal M2 based on the amount of charge Q3 (third amount of received light). The noise reduction control signal b _i,j (m, n) is generated by using a composite signal obtained by predeterminedly combining the third image pickup signal M3 based on the 3rd image pickup signal M3 for each pixel. The noise reduction control signal b _i,j (m, n) generated by the noise reduction control signal generation section 54 is output to the first noise reduction section 55, the second noise reduction section 56, and the third noise reduction section 58, respectively. be done.

Further, each process of the first noise reduction unit 55, the second noise reduction unit 56, and the third noise reduction unit 58 is also the same as the processing of the first noise reduction unit 55 etc. (see FIG. 2) described in the first embodiment. The same is true. That is, the control unit 5A controls the pixel position of the pixel whose position is indicated by the noise reduction control signal b _i,j (m, n) in each of the first image signal M1, the second image signal M2, and the third image signal M3. Noise reduction processing is performed in which the average value obtained by dividing the sum of the values by the number of pixels concerned is replaced as a new pixel value.

The distance calculation unit 57 shown in FIG. Based on the output pixel value O3(i, j) of the unit 58, distance data D(i, j) from the light receiving unit 2 to the object is calculated for each pixel. Note that the distance calculation method differs depending on the magnitude relationship between the delay time Td (see FIG. 11) and the predetermined time T0 during which the exposure timing control signals S1, S2, and S3 are maintained in the ON state.

For example, if the delay time Td is less than the predetermined time T0, all of the reflected light from the object is exposed during the period when the exposure timing control signals S1 and S2 are sequentially output (times t1 to t5 in FIG. 11). Ru. At this time, the amount of charge Q3 based on the exposure timing control signal S3 is smaller than the amount of charge Q1 based on the exposure timing control signal S1.

On the other hand, when the delay time Td is longer than the predetermined time T0, all of the reflected light from the object is exposed during the period in which the exposure timing control signals S2 and S3 are output. At this time, the amount of charge Q1 based on the exposure timing control signal S1 is greater than or equal to the amount of charge Q3 based on the exposure timing control signal S3. Therefore, the distance calculation unit 57 performs the determination process of (Equation 8) below.

When Q1>Q3, (judgment result)=0
When Q1≦Q3, (judgment result)=1 (Formula 8)

For example, when the determination result of (Formula 8) is "0", the distance calculation unit 57 calculates distance data D (i, j) based on (Formula 9) below.

Note that the distance data D (i, j) in (Equation 9) is data indicating the distance to the target object at the pixel (i, j). Moreover, T0 in (Formula 9) is the pulse width of the light irradiated to the object (see FIG. 11), and c is the speed of light (3×10 ⁸ [m/s]). Further, O1 (i, j) is an output pixel value corresponding to the first image signal M1, O2 (i, j) is an output pixel value corresponding to the second image signal M2, and O3 is an output pixel value corresponding to the third image signal M1. This is the output pixel value corresponding to M3. By such calculation based on (Equation 9), the distance to the object is calculated for each pixel (for each measurement position).

On the other hand, when the determination result of the above-mentioned (Formula 8) is "1", the distance calculation unit 57 calculates distance data D (i, j) based on the following (Formula 10).

Then, the control unit 5 calculates distances for all pixels while sequentially shifting the pixel positions (i, j). As a result, a distance image is generated that indicates the distance to the target object for each pixel.

<Effect>
According to the second embodiment, depending on the distance to the object, one of the charge amounts Q1 and Q3 becomes only an external light component. Therefore, the reflected light component can be extracted by predetermined subtraction of the external light component based on the digital value of the charge amount Q1 or the charge amount Q3. Therefore, according to the second embodiment, distance can be measured with higher accuracy than the first embodiment. Furthermore, by sequentially performing three exposures with different timings for one light emission, the upper limit of the measurable distance can be doubled as compared to the first embodiment.

≪Third embodiment≫
In the third embodiment, the control unit 5B (see FIG. 14) individually performs the smoothing process and the noise reduction control signal generation process for each of the first image signal M1 and the second image signal M2, and then performs the synthesis process. This embodiment differs from the first embodiment in that it is performed. Note that other aspects are the same as those in the first embodiment. Therefore, the parts that are different from the first embodiment will be explained, and the explanation of the overlapping parts will be omitted.

FIG. 14 is a functional block diagram including a control unit 5B of a distance measuring device 100B according to the third embodiment.
As shown in FIG. 14, the control unit 5B of the distance measuring device 100B includes an imaging control unit 51, a first smoothing unit 53a, a second smoothing unit 53b, a first noise reduction control signal generation unit 54a, It includes a second noise reduction control signal generation section 54b and a synthesis section 52B. In addition to the above-described configuration, the control unit 5B includes a first noise reduction unit 55, a second noise reduction unit 56, and a distance calculation unit 57.

As shown in FIG. 14, the first image signal M1 generated by the light receiving section 2 is output to each of the first smoothing section 53a and the first noise reduction section 55. Further, the second image signal M2 generated by the light receiving section 2 is output to each of the second smoothing section 53b and the second noise reduction section 56.

The first smoothing unit 53a performs predetermined filter processing on the first image signal M1 to smooth it. Note that the filter used in the first smoothing section 53a may be, for example, an average filter, a Gaussian filter, or a median filter. Similarly, the second smoothing unit 53b smoothes the second image signal M2 by subjecting it to predetermined filter processing.

The first noise reduction control signal generation section 54a generates the first noise reduction control signal b1 _i,j (m, n) based on the image data input from the first smoothing section 53a. On the other hand, the second noise reduction control signal generation section 54b generates the second noise reduction control signal b2 _i,j (m, n) based on the image data input from the second smoothing section 53b.

Note that the processing of the first noise reduction control signal generation section 54a and the second noise reduction control signal generation section 54b is similar to the processing of the noise reduction control signal generation section 54 (see FIG. 2) described in the first embodiment. be. That is, the control unit 5B uses the first imaging signal M1 based on the amount of charge Q1 (first amount of received light) to generate a predetermined first noise reduction control signal (first control signal) b1 _i,j (m, n). At the same time, a predetermined second noise reduction control signal (second control signal) b2 _i,j (m, n) is generated using the second imaging signal M2 based on the amount of charge Q2 (second amount of received light). do.

Note that the first noise reduction control signal (first control signal) b1 _i,j (m, n) described above refers to the pixel to be subjected to noise reduction processing among each pixel included in the first image pickup signal M1. This is a signal that indicates the position of a pixel in the vicinity of the target pixel, of which the absolute value of the difference between the pixel value and the pixel value of the target pixel is less than or equal to a predetermined value.

In addition, the second noise reduction control signal (second control signal) b2 _i,j (m, n) described above refers to the pixel to be subjected to noise reduction processing among each pixel included in the second image pickup signal M2. It is a signal indicating the position of a pixel in the vicinity of a target pixel for which the absolute value of the difference between the pixel value and the pixel value of the target pixel is less than or equal to a predetermined value.

The first noise reduction control signal b1 _i,j (m, n) generated by the first noise reduction control signal generation section 54a and the second noise reduction control signal b2 generated by the second noise reduction control signal generation section 54b. _{i, j} (m, n) are respectively output to the combining section 52.

For example, the synthesis unit 52 performs a product operation of the first noise reduction control signal b1 _i,j (m, n) and the second noise reduction control signal b2 _i,j (m, n) for each element (m, n), a composite signal is generated. Specifically, for each element (m, n), the synthesis unit 52 determines that the value of the first noise reduction control signal b1 _i,j (m, n) is "1" and that the value of the second noise reduction control signal b1 If the value of the control signal b2 _i,j (m, n) is "1", the value of the combined noise reduction control signal b _i,j (m, n) is set to "1". Furthermore, the synthesis unit 52 determines that the value of at least one of the first noise reduction control signal b1 _i,j (m, n) and the second noise reduction control signal b2 _i,j (m, n) is “0”. , the value of the synthesized noise reduction control signal b _i,j (m, n) is set to "0".

In this way, the control unit 5B controls the first noise reduction control signal (first control signal) b1 _i,j (m,n) and the second noise reduction control signal (second control signal) b1 _i,j (m , n) for each pixel in a predetermined manner, a noise reduction control signal b _i,j (m, n) is generated. The synthesized noise reduction control signal b _i,j (m, n) is output from the synthesis section 52 to the first noise reduction section 55 and also to the second noise reduction section 56 . Note that each process of the first noise reduction unit 55, the second noise reduction unit 56, and the distance calculation unit 57 shown in FIG. 14 is the same as that of the first embodiment, and therefore the description thereof will be omitted.

<Effect>
According to the third embodiment, the control unit 5B generates the first noise reduction control signal b1 i,j (m, n) based on the signal obtained by smoothing the first imaging signal M1, and also generates the second noise reduction control signal b1 _i,j (m, n). A second noise reduction control signal b2 _i,j (m, n) is generated based on a signal obtained by smoothing the imaging signal M2. Here, each pixel value of the first imaging signal M1 is derived from the amount of charge Q1, and each pixel value of the second imaging signal M2 is derived from the amount of charge Q2, and the length of the distance to the object is It is reflected as is. By combining the first image signal M1 and the second image signal M2 (that is, performing a product operation of each element), pixels to be subjected to noise reduction processing can be appropriately extracted, and the target object The distance can be calculated with higher accuracy than in the first embodiment.

≪Modification example≫
Although the distance measuring device 100 and the like have been described above in each embodiment, the present invention is not limited to these descriptions, and various changes can be made.
For example, in the first embodiment, the average pixel value at the position specified by the noise reduction control signal b _i,j (m, n) is calculated in the first image signal M1 and the second image signal M2, and Although the processing in which the result is used as an output signal value has been described, the present invention is not limited to this. That is, the noise reduction processing performed by the control unit 5 is performed by adjusting the pixel value of the pixel whose position b _i,j (m, n) is indicated by the noise reduction control signal in each of the first imaging signal M1 and the second imaging signal M2. The weighted average calculated based on the position of the target pixel may be replaced as a new pixel value. Specifically, for pixels in the vicinity of the target pixel, the shorter the distance to the target pixel, the greater the weighting when performing weighted averaging. Alternatively, the pixel values of multiple pixels may be extracted based on the noise reduction control signal b _i,j (m, n), and the median of these pixel values may be used as the output signal value. . Note that the same can be said of the third embodiment as well as the second embodiment (the case where the first imaging signal M1, the second imaging signal M2, and the third imaging signal M3 are used).

Further, in the second embodiment, the process of removing the external light component and extracting the reflected light component at the stage when the distance calculation unit 57 (see FIG. 10) calculates the distance to the target object has been described. Not exclusively. That is, the control unit 5A (see FIG. 10) generates two signals in which reflected light components are extracted based on the first image signal M1, the second image signal M2, and the third image signal M3, and The distance to the object may be calculated based on two signals.

Furthermore, in the first embodiment, a configuration has been described in which the control section 5 (see FIG. 2) includes the smoothing section 53, but the present invention is not limited to this. That is, the smoothing section 53 may be omitted, and the synthesized signal may be output from the synthesizing section 52 to the noise reduction control signal generating section 54. Note that the same can be said of the second embodiment and the third embodiment.

Further, in each embodiment, a configuration has been described in which the distance measuring device 100 (see FIG. 1) and the display device 200 (see FIG. 1) are separate bodies, but the present invention is not limited to this. That is, the distance measuring device 100 may include a display section (not shown) that displays a distance image in a predetermined manner.
Furthermore, in the first embodiment, when measuring the distance to an object, the light emission timing control signal S0 (see FIG. 3) and the exposure timing control signals S1 and S2 (see FIG. 3) are generated once each. Although described above, the control unit 5 may generate each signal multiple times at a predetermined period and accumulate the amounts of charge Q1 and Q2. Note that the same applies to the second embodiment and the third embodiment.

Moreover, each embodiment can be combined as appropriate. For example, the second embodiment and the third embodiment may be combined to perform the following processing. That is, the control unit 5 first generates a predetermined first control signal using the first imaging signal M1 based on the amount of charge Q1 (first amount of received light), and also generates a predetermined first control signal based on the amount of charge Q2 (second amount of received light). A predetermined second control signal is generated using the second image pickup signal M2 based on the charge amount Q3 (third amount of received light), and a predetermined third control signal is further generated using the third image pickup signal M3 based on the charge amount Q3 (third amount of received light). do. The first control signal described above indicates the position of a pixel to be subjected to noise reduction processing among each pixel included in the first image pickup signal M1, and also indicates the pixel value of pixels in the vicinity of the target pixel. This signal indicates the position of a pixel where the absolute value of the difference between the pixel value and the pixel value of the target pixel is less than or equal to a predetermined value. Note that the same applies to the second control signal and the third control signal. Then, the control unit 5 generates a noise reduction control signal b _i,j ( m, n). As a result, the noise reduction control signals b _{i, j} (m, n) can be calculated appropriately. Furthermore, since external light components are removed when calculating the distance to the target object, the distance to the target object can be calculated with high accuracy.

Further, the noise reduction control signal b _i,j (m, n) described in each embodiment is an example, and the noise reduction control signal b _i,j (m, n) generated by another predetermined method may be It may be used in common for each pixel of the first imaging signal M1 and the second imaging signal M2.

Furthermore, one or more computers such as a server (not shown) may execute all or part of the program that implements the functions of the distance measuring device 100 described in each embodiment. The above program can be provided via a communication line, or can be written on a recording medium such as a CD-ROM and distributed.

Further, each embodiment is described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, it is possible to add, delete, or replace some of the configurations of the embodiments with other configurations. Further, each of the above-described configurations, functions, etc. may be realized in part or in whole by, for example, designing an integrated circuit. Further, each of the configurations, functions, etc. described above may be realized by software by a processor interpreting and executing a program for realizing each function. Further, the mechanisms and configurations described above are those considered necessary for explanation, and not all mechanisms and configurations are necessarily shown in the product.

1 Light emitting unit 2 Light receiving unit 3 Reference clock generation unit 4 Storage unit 5, 5A, 5B Control unit 6 Distance image output unit 51 Imaging control unit 200 Display device 52, 52B Combining unit 53 Smoothing unit 53a First smoothing unit 53b 2 smoothing unit 54 noise reduction control signal generation unit 54a first noise reduction control signal generation unit 54b second noise reduction control signal generation unit 55 first noise reduction unit 56 second noise reduction unit 57 distance calculation unit 58 third noise reduction Section 100, 100A, 100B Distance measuring device J Target object M1 First imaging signal M2 Second imaging signal M3 Third imaging signal Q1 Amount of charge (first amount of light received)
Q2 Charge amount (second light reception amount)
Q3 Charge amount (3rd light reception amount)

Claims (9)

a light emitting part that irradiates light to a target object;
a light receiving unit that receives light including reflected light from the target object a plurality of times with predetermined timing shifts, and accumulates the amount of light received for each of the plurality of light receptions;
a control unit that calculates the distance to the object for each pixel based on a time-of-flight method using a plurality of imaging signals corresponding to the plurality of light receptions,
The control unit performs noise reduction processing to reduce noise in each of the plurality of imaging signals,
A predetermined noise reduction control signal used in the noise reduction process is common to each pixel in the plurality of imaging signals,
The light receiving section receives light in synchronization with the irradiation of light by the light emitting section, accumulates a first amount of received light, and then receives light from the end of irradiation of light by the light emitting section and accumulates a second amount of received light. ,
The control unit reduces the noise by using a composite signal obtained by combining a first image signal based on the first amount of received light and a second image signal based on the second amount of received light for each pixel in a predetermined manner. generate a control signal,
The noise reduction control signal indicates the position of a pixel to be subjected to the noise reduction processing among each pixel included in the composite signal, and also indicates the pixel value and the The signal indicates the position of a target pixel where the absolute value of the difference between the pixel value and the pixel value is less than or equal to a predetermined value.
A distance measuring device featuring: a light emitting part that irradiates light to a target object;
a light receiving unit that receives light including reflected light from the target object a plurality of times with predetermined timing shifts, and accumulates the amount of light received for each of the plurality of light receptions;
a control unit that calculates the distance to the object for each pixel based on a time-of-flight method using a plurality of imaging signals corresponding to the plurality of light receptions,
The control unit performs noise reduction processing to reduce noise in each of the plurality of imaging signals,
A predetermined noise reduction control signal used in the noise reduction process is common to each pixel in the plurality of imaging signals,
The light receiving section receives light in synchronization with the irradiation of light by the light emitting section, accumulates a first amount of received light, and then receives light from the end of irradiation of light by the light emitting section and accumulates a second amount of received light. ,
The control unit includes:
A first imaging signal based on the first amount of received light is used to generate a predetermined first control signal, and a second imaging signal based on the second amount of received light is used to generate a predetermined second control signal. ,
The first control signal indicates the position of a pixel to be subjected to the noise reduction process among each pixel included in the first image pickup signal, and also indicates the pixel value of pixels in the vicinity of the target pixel. and the pixel value of the target pixel;
The second control signal indicates the position of the pixel to be subjected to the noise reduction process among the pixels included in the second image pickup signal, and also indicates the pixel value of the pixels in the vicinity of the target pixel. and the pixel value of the target pixel;
Generating the noise reduction control signal based on a composite signal obtained by combining the first control signal and the second control signal in a predetermined manner for each pixel.
A distance measuring device featuring: The noise reduction process performed by the control unit includes:
In each of the first imaging signal and the second imaging signal, an average value obtained by dividing the sum of pixel values of pixels whose positions are indicated by the noise reduction control signal by the number of the pixels is set as a new pixel value. The process of replacing
Or
In each of the first imaging signal and the second imaging signal, a new weighted average is calculated based on the pixel value of the pixel whose position is indicated by the noise reduction control signal, and the position of the target pixel is used as a reference. The distance measuring device according to claim 1 or 2, wherein the distance measuring device is a process of replacing as a pixel value. a light emitting part that irradiates light to a target object;
a light receiving unit that receives light including reflected light from the target object a plurality of times with predetermined timing shifts, and accumulates the amount of light received for each of the plurality of light receptions;
a control unit that calculates the distance to the object for each pixel based on a time-of-flight method using a plurality of imaging signals corresponding to the plurality of light receptions,
The control unit performs noise reduction processing to reduce noise in each of the plurality of imaging signals,
A predetermined noise reduction control signal used in the noise reduction process is common to each pixel in the plurality of imaging signals,
The light receiving section receives light in synchronization with the irradiation of light by the light emitting section, accumulates a first amount of received light, and then receives light from the end of irradiation of light by the light emitting section and accumulates a second amount of received light. , further, receiving light from the end of receiving the second amount of received light and accumulating a third amount of received light;
The control unit is configured to predetermined, for each pixel, a first image signal based on the first amount of received light, a second image signal based on the second amount of received light, and a third image signal based on the third amount of received light. Generating the noise reduction control signal using the synthesized signal,
The noise reduction control signal indicates the position of a pixel to be subjected to the noise reduction processing among each pixel included in the composite signal, and also indicates the pixel value and the The signal indicates the position of a target pixel where the absolute value of the difference between the pixel value and the pixel value is less than or equal to a predetermined value.
A distance measuring device featuring: a light emitting part that irradiates light to a target object;
a light receiving unit that receives light including reflected light from the target object a plurality of times with predetermined timing shifts, and accumulates the amount of light received for each of the plurality of light receptions;
a control unit that calculates the distance to the object for each pixel based on a time-of-flight method using a plurality of imaging signals corresponding to the plurality of light receptions,
The control unit performs noise reduction processing to reduce noise in each of the plurality of imaging signals,
A predetermined noise reduction control signal used in the noise reduction process is common to each pixel in the plurality of imaging signals,
The light receiving section receives light in synchronization with the irradiation of light by the light emitting section, accumulates a first amount of received light, and then receives light from the end of irradiation of light by the light emitting section and accumulates a second amount of received light. , further, receiving light from the end of receiving the second amount of received light and accumulating a third amount of received light;
The control unit includes:
A first imaging signal based on the first amount of received light is used to generate a predetermined first control signal, and a second imaging signal based on the second amount of received light is used to generate a predetermined second control signal. , further generating a predetermined third control signal using a third imaging signal based on the third amount of received light;
The first control signal indicates the position of a pixel to be subjected to the noise reduction process among each pixel included in the first image pickup signal, and also indicates the pixel value of pixels in the vicinity of the target pixel. and the pixel value of the target pixel;
The second control signal indicates the position of the pixel to be subjected to the noise reduction process among the pixels included in the second image pickup signal, and also indicates the pixel value of the pixels in the vicinity of the target pixel. and the pixel value of the target pixel;
The third control signal indicates the position of a pixel to be subjected to the noise reduction process among each pixel included in the third image pickup signal, and also indicates the pixel value of pixels in the vicinity of the target pixel. and the pixel value of the target pixel;
Generating the noise reduction control signal based on a composite signal obtained by combining the first control signal, the second control signal, and the third control signal in a predetermined manner for each pixel.
A distance measuring device featuring: The noise reduction process performed by the control unit includes:
In each of the first imaging signal, the second imaging signal, and the third imaging signal, an average value obtained by dividing the sum of pixel values of pixels whose positions are indicated by the noise reduction control signal by the number of the pixels. This is a process of replacing , as a new pixel value,
Or
In each of the first image signal, the second image signal, and the third image signal, calculate based on the pixel value of the pixel whose position is indicated by the noise reduction control signal, with the position of the target pixel as a reference. 6. The distance measuring device according to claim 4 , wherein the distance measuring device is a process of replacing the calculated weighted average as a new pixel value. The control unit smoothes the composite signal using a predetermined filter, and generates the noise reduction control signal using the smoothed composite signal,
The distance measuring device according to claim 1 or 4 , wherein the filter is an average filter, a Gaussian filter, or a median filter. A light emitting process that irradiates the target with light,
a light reception process of receiving light including reflected light from the target object multiple times with predetermined timing shifts, and accumulating the amount of light received for each of the multiple times;
Sequentially performing calculation processing for calculating a distance to the object for each pixel based on a time-of-flight method using a plurality of imaging signals corresponding to the plurality of light receptions,
The arithmetic processing includes noise reduction processing that reduces noise in each of the plurality of imaging signals,
A predetermined noise reduction control signal used in the noise reduction process is common to each pixel in the plurality of imaging signals,
In the light reception process, light is received in synchronization with the light irradiation by the light emission process and a first amount of received light is accumulated, and then light is received from the end of the light irradiation by the light emission process and a second amount of received light is accumulated. ,
In the arithmetic processing, the noise reduction is performed using a composite signal obtained by combining a first image signal based on the first amount of received light and a second image signal based on the second amount of received light for each pixel in a predetermined manner. generate a control signal,
The noise reduction control signal indicates the position of a pixel to be subjected to the noise reduction processing among each pixel included in the composite signal, and also indicates the pixel value and the The signal indicates the position of a target pixel where the absolute value of the difference between the pixel value and the pixel value is less than or equal to a predetermined value.
A distance measurement method characterized by: A program for causing a computer to execute the distance measuring method according to claim 8 .

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