JP2020027978A - Imaging device and control method - Google Patents

Abstract

To provide an imaging device capable of suppressing generation of noise in an image caused by a switching timing of a data transmission mode.SOLUTION: Provided is an imaging device that comprises: a conversion unit that converts an analog signal into a digital signal; a signal processing unit that performs signal processing to the digital signal; and a controller that at least uses a first signal used for conversion at the conversion unit and a second signal processed at the signal processing unit to control a switching timing to a first data transmission mode and a second data transmission mode with a lower transmission rate than the first data transmission mode, of a communication mode of a data signal to be outputted on the basis of a predetermined rule.SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to an imaging device and a control method.

  The MIPI (Mobile Industry Processor Interface) standard is often used as an output IF of an imaging device. The MIPI signal used in the MIPI standard has a high-speed data transfer operation (HS) section and a low power consumption operation (LP) section. In the HS section, it operates with a small-amplitude differential signal, and in the LP section, it operates with a single-ended signal having an amplitude from the power supply to GND. Patent Literature 1, for example, is disclosed as a technique related to the MIPI standard.

JP 2017-195500 A

  At the time of switching between the HS section and the LP section, a level fluctuation of the transmission path occurs, and the power supply and GND current and voltage of the device for driving the transmission path fluctuate with the fluctuation. Due to a change in GND caused by switching between the HS section and the LP section, noise occurs in an image generated by the imaging device.

  Therefore, in the present disclosure, a new and improved imaging apparatus and control method capable of suppressing the occurrence of image noise due to the timing of switching the data transmission mode by controlling the timing of switching the data transmission mode Suggest.

  According to the present disclosure, a conversion unit that converts an analog signal into a digital signal, a signal processing unit that performs signal processing on the digital signal, a first signal used for conversion in the conversion unit, and a signal processing unit A first data transmission mode of a communication mode of a data signal to be output using at least a second signal to be processed, and a second data transmission mode having a lower transmission speed than the first data transmission mode And a control unit that controls the timing of switching to the above based on a predetermined rule.

  According to the present disclosure, converting an analog signal to a digital signal, performing signal processing on the digital signal, a first signal used for the conversion, and a second signal processed in the signal processing The timing at which the communication mode of the data signal to be output is switched between the first data transmission mode and the second data transmission mode having a lower transmission speed than the first data transmission mode is determined by using at least a predetermined rule. And a control method based on the control method.

  As described above, according to the present disclosure, by controlling the timing of switching the data transmission mode, it is possible to suppress the occurrence of image noise due to the timing of switching the data transmission mode, a new and improved An imaging device and a control method can be provided.

  Note that the above effects are not necessarily limited, and any of the effects shown in the present specification or other effects that can be grasped from the present specification are used together with or in place of the above effects. May be played.

FIG. 4 is an explanatory diagram illustrating an example of a signal in an HS section and a signal in an LP section. FIG. 5 is an explanatory diagram showing timings that are susceptible to noise when digitizing a signal from a pixel. FIG. 9 is an explanatory diagram showing a mechanism of generation of noise caused by switching between an HS section and an LP section of MIPI. FIG. 9 is an explanatory diagram showing an example of an image on which noise caused by switching between the HS section and the LP section of MIPI is superimposed. FIG. 1 is an explanatory diagram illustrating a functional configuration example of an imaging device 100 according to an embodiment of the present disclosure. FIG. 8 is an explanatory diagram illustrating a control example of switching timing between an HS section and an LP section. FIG. 3 is an explanatory diagram illustrating a first configuration example of a control unit. FIG. 9 is an explanatory diagram showing a state in which the switching timing of the HS section and the LP section is shifted to a timing less affected by noise. FIG. 9 is an explanatory diagram illustrating a second configuration example of the control unit. FIG. 9 is an explanatory diagram illustrating an example of a relationship between a ramp signal, switching timing of an HS section and an LP section, and a noise amount. FIG. 13 is an explanatory diagram illustrating a third configuration example of the control unit. FIG. 4 is an explanatory diagram for describing effects of the embodiment of the present disclosure.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

The description will be made in the following order.
1. 1. Embodiment of the present disclosure 1.1. Background 1.2. 1. Configuration example and operation example Conclusion

<1. Embodiment of the Present Disclosure>
[1.1. Background]
Before describing the embodiments of the present disclosure in detail, the circumstances that led to the embodiments of the present disclosure will be described.

  The MIPI standard is often used as an output IF of an imaging device. The MIPI signal used in the MIPI standard has a high-speed data transfer operation (HS) section and a low power consumption operation (LP) section. In the HS section, it operates with a small-amplitude differential signal, and in the LP section, it operates with a single-ended signal having an amplitude from the power supply to GND. FIG. 1 is an explanatory diagram illustrating an example of a signal in an HS section and a signal in an LP section. FIG. 1 shows an activation signal having an amplitude of 250 mV in the HS section, and a single-ended signal that changes between GND and a voltage of 1.2 V in the LP section.

  At the time of switching between the HS section and the LP section, a level fluctuation of the transmission path occurs, and the power supply and GND current and voltage of the device for driving the transmission path fluctuate with the fluctuation. In general, the GND of the apparatus is designed so that interference between the analog processing unit and the digital processing unit is reduced. However, this interference cannot be completely eliminated because the respective GNDs are coupled via the substrate of the image sensor. For this reason, noise is generated in an image due to a change in GND generated when the MIPI signal is switched.

  From each of a plurality of pixels in the pixel array, an analog pixel signal obtained by photoelectrically converting incident light and a signal serving as a reference for digitization are compared in an analog processing unit, and the time until the result coincides is counted. Is digital output data. The timing at which this processing is performed is most easily affected by noise. FIG. 2 is an explanatory diagram showing timings that are susceptible to noise when digitizing a signal from a pixel. By controlling the counter at the timing when the signal from the pixel and the slope of the output of the DAC (Digital Analog Converter) cross, the signal from the pixel is digitized. At this time, the timing is such that the slope portion of the output of the DAC is easily affected by noise.

  The evaluation of the image noise is performed in a state where the light in which the noise is most conspicuous is blocked (light shielding state). In the light-shielded state, the result is the same when reading the reference level and when reading the pixel level. If the switching between the HS section and the LP section of the MIPI occurs at the time of reading the reference level or the pixel level, the reading results do not become the same, and noise (a phenomenon that only a part of the image becomes bright or dark) occurs.

  This process is performed simultaneously for the pixel arrays on the same line, but the operation clock frequencies of the analog processing unit and the digital processing unit are the same, and switching between the HS section and the LP section of the MIPI is performed every several lines. In the case of occurrence of noise, generation of noise can be avoided by steadily delaying the output timing of the switching timing between the HS section and the LP section of the MIPI.

  However, when the frequency of the operation clock is different between the analog processing unit and the digital processing unit, the switching timing of the HS section and the LP section of MIPI is shifted every moment. The respective operation clocks are asynchronous, and there are a plurality of types of phase relationships between the output signal of the DAC and the switching between the HS section and the LP section of the MIPI, and they change periodically. Therefore, it is not possible to suppress the generation of noise only by giving a steady delay to the switching timing between the HS section and the LP section, and the noise becomes periodically dark and light in the vertical direction.

  FIG. 3A is an explanatory diagram illustrating a mechanism of generation of noise caused by switching between the HS section and the LP section of MIPI. There are a plurality of types of phase relationships between the output signal from the DAC and the switching timing of the HS section and the LP section of the MIPI, and the phase relation changes periodically. Therefore, the switching timing of the HS section and the LP section of MIPI shifts every moment.

  FIG. 3B is an explanatory diagram showing an example of an image on which noise caused by switching between the HS section and the LP section of MIPI is superimposed. As shown in FIG. 3B, due to the switching between the HS section and the LP section of the MIPI, the noise appears as a periodic dark and light noise in the vertical direction.

  In view of the above points, the present discloser has conducted intensive studies on a technique capable of suppressing the occurrence of image noise caused by switching between the HS section and the LP section in the MIPI standard. As a result, as disclosed below, the present Disclosure has devised a technology capable of suppressing generation of image noise by controlling switching between the HS section and the LP section in the MIPI standard.

  The details that led to the embodiment of the present disclosure have been described above.

[1.2. Configuration example and operation example]
Subsequently, a functional configuration example of the imaging device according to the embodiment of the present disclosure will be described. FIG. 4 is an explanatory diagram illustrating a functional configuration example of the imaging device 100 according to the embodiment of the present disclosure. Hereinafter, an example of a functional configuration of the imaging device 100 according to the embodiment of the present disclosure will be described with reference to FIG.

  As illustrated in FIG. 4, the imaging device 100 according to the embodiment of the present disclosure includes a pixel array 110, an analog processing unit 120, a storage unit 130, a signal processing unit 140, a control unit 150, an output process And a unit 160.

  In the pixel array 110, pixels for photoelectrically converting incident light are provided in an array, and output pixel signals obtained by photoelectric conversion of the incident light. The pixel signal from the pixel array 110 is sent to the analog processing unit 120.

  The analog processing unit 120 performs a digitizing process on a pixel signal from the pixel array 110, which is an analog signal, and an image process on a digitized signal. The signal after performing the digitization and the image processing is sent to the storage unit 130. An output signal (for example, a horizontal synchronization signal) of a DAC used for digitization in the analog processing unit 120 is sent to the control unit 150.

  Storage section 130 temporarily stores a signal output from analog processing section 120. The signal processing unit 140 reads out the signal stored in the storage unit 130 and performs a predetermined signal processing.

  The control unit 150 controls the switching timing of the HS section and the LP section of the output signal from the output processing unit 160 based on the DAC output signal from the analog processing unit 120 and the clock signal used in the signal processing unit 140. I do.

  The output processing unit 160 outputs a signal output from the signal processing unit 140 based on the control of the control unit 150. With respect to the output signal from the output processing unit 160, the control unit 150 controls the switching timing of the HS section and the LP section of the MIPI, so that the shading that has been generated periodically in the vertical direction becomes non-periodic in the entire screen. The noise changes to light and shade, making it difficult to see.

  FIG. 5 is an explanatory diagram illustrating a control example of the switching timing of the HS section and the LP section of the MIPI by the control unit 150. As shown in FIG. 5, the end of the HS section and the start time of the LP section, and the start time of the LP section and the start time of the HS section are changed for each frame and each horizontal cycle. As described above, by controlling the end of the HS section and the start time of the LP section, and the start time of the LP section and the start time of the HS section, the imaging apparatus 100 according to the embodiment of the present disclosure can operate in the vertical direction. By changing the shading that has occurred periodically to a non-periodic shading of the entire screen, it is possible to make the noise hard to be visually recognized.

  As above, the functional configuration example of the imaging device 100 according to the embodiment of the present disclosure has been described with reference to FIG. Subsequently, a configuration example of the control unit 150 included in the imaging device 100 according to the embodiment of the present disclosure will be described.

(First configuration example)
First, a first configuration example of the control unit 150 will be described. FIG. 6 is an explanatory diagram illustrating a first configuration example of the control unit 150 included in the imaging device 100 according to the embodiment of the present disclosure. Hereinafter, a configuration example of the control unit 150 will be described.

  As shown in FIG. 6, the control unit 150 includes an M-sequence signal generation unit 151, a switching timing register 152, a timing generation unit 153, an addition unit 154, and a switching timing counter 155. FIG. 6 shows an example of the output processing unit 160 as a MIPI driver.

  The M-sequence signal generation unit 151 generates an M-sequence signal having a predetermined number of bits as a pseudo-random number. For example, when the M-sequence signal generation unit 151 generates a 7-bit M-sequence signal, it repeatedly generates 127 non-ordered data excluding zero. If the number of repetitions is small, periodic noise that is not sinusoidal is generated. Therefore, it is desirable to have a certain word length.

  On the other hand, even if the word length is too long, the output value cannot be used as it is because there is a limit in the amplitude and fineness of the timing. When the word length is long, only the necessary number of bits from the lower bits of the signal generated by M-sequence signal generation section 151 may be used. By using only the necessary number of bits from the lower bits of the signal, it is possible to select the number of bits required for the signal while securing the length of the repetition period to some extent.

  The switching timing register 152 stores a load value used for controlling switching timing between the HS section and the LP section. The load value stored in the switching timing register 152 is not changed.

  The timing generator 153 outputs a load (LD) signal to be supplied to the switching timing counter 155.

  The adder 154 adds the signal generated by the M-sequence signal generator 151 to the load value held by the switching timing register 152, and outputs the result to the switching timing counter 155.

  The switching timing counter 155 controls the switching timing of the HS section and the LP section in the output processing unit 160 based on the load (LD) signal. The load signal is also synchronized with the data in the HS section at a predetermined cycle. That is, the signal generated by the timing generation unit 153 and the horizontal synchronization signal HSync generated by the analog processing unit 120 are input to the switching timing counter 155.

  The switching timing counter 155 inputs a signal obtained by adding a signal generated by the M-sequence signal generation unit 151 that changes at random to the load value held by the switching timing register 152, and switches between the HS section and the LP section. Control the timing. That is, in the first configuration example, the control unit 150 randomly changes the switching timing between the HS section and the LP section.

  By randomly changing the switching timing between the HS section and the LP section, the control unit 150 changes the shading that has been generated periodically in the vertical direction to the aperiodic shading of the entire screen, so that the noise that is hardly visually recognized is changed. It can be.

  The control unit 150 in the first configuration example can randomly change the switching timing between the HS section and the LP section, but the MIPI standard defines the minimum value of the switching time between the HS section and the LP section. . Therefore, the control unit 150 in the first configuration example randomly changes the switching timing between the HS section and the LP section so as not to fall below the minimum value of the switching time between the HS section and the LP section specified by the MIPI standard. Let it.

(Second configuration example)
Subsequently, a second configuration example of the control unit 150 will be described. The control unit 150 according to the second configuration example controls to always shift the switching timing between the HS section and the LP section to a timing less affected by noise based on the horizontal synchronization signal generated by the analog processing unit 120. .

  FIG. 7 is an explanatory diagram showing a state in which the switching timing between the HS section and the LP section is shifted to a timing less affected by noise. In FIG. 7, the switching timing between the HS section and the LP section is shifted not to the ramp portion of the output of the DAC but to a horizontal portion. By controlling the switching timing between the HS section and the LP section in this way, the control unit 150 can suppress the noise itself.

  FIG. 8 is an explanatory diagram illustrating a second configuration example of the control unit 150 included in the imaging device 100 according to the embodiment of the present disclosure. Hereinafter, a configuration example of the control unit 150 will be described.

  As illustrated in FIG. 8, the control unit 150 includes a switching timing register 152 and a switching timing counter 155. FIG. 8 illustrates an example of the output processing unit 160 as an MIPI driver.

  The switching timing register 152 stores a load value used for controlling switching timing between the HS section and the LP section. In the second configuration example, the value stored in the switching timing register 152 can be changed according to the amount of noise. The amount of noise may be obtained by, for example, taking an average value of pixels for each line and obtaining variance. The variance differs greatly between periodic noise and randomly generated noise. As the value stored in the switching timing register 152, a value that reduces the amount of noise is set as a specified value. This allows the control unit 150 to shift the switching timing between the HS section and the LP section to a timing less affected by noise.

  In the second configuration example, switching to the LP section is performed irrespective of the data in the HS section. Therefore, the transfer rate in the HS section is a speed at which data in the HS section can be completely output before switching to the LP section.

(Third configuration example)
Subsequently, a third configuration example of the control unit 150 will be described. The control unit 150 according to the third configuration example sets the switching timing between the HS section and the LP section while referring to the ramp signal generated by the analog processing unit 120 so that the timing is less affected by noise.

  FIG. 9 is an explanatory diagram showing an example of the relationship between the ramp signal generated by the analog processing unit 120, the switching timing between the HS section and the LP section, and the noise amount. When the switching timing between the HS section and the LP section is set to five as shown in FIG. 9, the pattern 3 has the largest noise amount and the pattern 1 has the smallest noise amount. Therefore, the control unit 150 according to the third configuration example sets the switching timing so that the HS section and the LP section are switched in pattern 1.

  FIG. 10 is an explanatory diagram illustrating a third configuration example of the control unit 150 included in the imaging device 100 according to the embodiment of the present disclosure. Hereinafter, a configuration example of the control unit 150 will be described.

  As illustrated in FIG. 10, the control unit 150 includes a switching timing register 152, a switching timing counter 155, and a noise determination unit 156. FIG. 10 shows an example of the output processing unit 160 as an MIPI driver.

  The switching timing register 152 stores a load value used for controlling switching timing between the HS section and the LP section. In the third configuration example, the value stored in the switching timing register 152 can be changed according to the amount of noise. The amount of noise may be obtained by, for example, taking an average value of pixels for each line and obtaining variance. The variance differs greatly between periodic noise and randomly generated noise. As the value stored in the switching timing register 152, a value that reduces the amount of noise is set as a specified value. This allows the control unit 150 to shift the switching timing between the HS section and the LP section to a timing less affected by noise.

  The noise determination unit 156 determines the amount of noise in the image signal. The amount of noise has a correlation with the switching timing between the HS section and the LP section and the phase of the slope of the ramp signal. That is, when the value of the switching timing register 152 is sequentially increased or decreased, the noise amount increases or decreases according to the increase or decrease. The noise determination unit 156 can determine the setting that minimizes the noise by measuring the noise amount of the image signal for each setting of the switching timing register 152.

  As described above, the switching timing between the HS section and the LP section is restricted in the MIPI standard. On the other hand, in the MIPI standard, there is no definition of the maximum time for the switching time (THS-TRAIL) from the end of the HS section to the driving circuit for the LP and the time of the LP section. Accordingly, when controlling the switching timing between the HS section and the LP section, the control unit 150 extends the switching time from the end of the HS section to the drive circuit for the LP section and the time of the LP section while complying with the MIPI standard. . Thereby, the control unit 150 can change the switching timing between the HS section and the LP section without changing the transfer frequency.

  Lastly, effects according to the embodiment of the present disclosure will be described. FIG. 11 is an explanatory diagram for describing effects of the embodiment of the present disclosure.

  FIG. 11 illustrates a case where an image 210 having a noise of 64 ± 3 (LSBrms) and a horizontal line of a sine wave having an amplitude of ± 0.3 (LSB) are superimposed on an image 200, and an HS section according to the present embodiment. A case where the image 230 in which the switching timing of the LP section is changed is superimposed is shown. When a horizontal stripe of a sine wave having an amplitude of ± 0.3 (LSB) is superimposed, horizontal stripe noise is conspicuous as in the image 220. On the other hand, according to this embodiment, the switching timing between the HS section and the LP section is changed. Then, the noise is less noticeable as in the image 240. That is, according to the present embodiment, it is possible to suppress the generation of image noise by controlling the switching between the HS section and the LP section in the MIPI standard.

<2. Summary>
As described above, according to the embodiment of the present disclosure, it is possible to provide the imaging apparatus 100 that controls the end of the HS section and the start time of the LP section, and the start time of the LP section and the start time of the HS section. Can be done. The imaging apparatus 100 according to the embodiment of the present disclosure controls the end of the HS section and the start time of the LP section, and the start time of the LP section and the start time of the HS section, so that the By changing the generated shading to a non-periodic shading of the entire screen, it is possible to make the noise hard to be visually recognized.

  It is also possible to create a computer program for causing hardware such as a CPU, a ROM, and a RAM incorporated in each device to exhibit the same functions as those of the above-described devices. Also, a storage medium storing the computer program can be provided. Further, by configuring each functional block shown in the functional block diagram by hardware, a series of processing can be realized by hardware.

  As described above, the preferred embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, but the technical scope of the present disclosure is not limited to such examples. It is apparent that a person having ordinary knowledge in the technical field of the present disclosure can conceive various changes or modifications within the scope of the technical idea described in the claims. It is understood that also belongs to the technical scope of the present disclosure.

  Further, the effects described in this specification are merely illustrative or exemplary, and are not restrictive. That is, the technology according to the present disclosure can exhibit other effects that are obvious to those skilled in the art from the description in the present specification, in addition to or instead of the above effects.

Note that the following configuration also belongs to the technical scope of the present disclosure.
(1)
A conversion unit that converts an analog signal into a digital signal;
A signal processing unit that performs signal processing on the digital signal,
A first data transmission mode of a communication mode of a data signal to be output, using at least a first signal used for conversion in the conversion unit and a second signal processed in the signal processing unit; A control unit that controls a timing of switching to a second data transmission mode having a lower transmission speed than the first data transmission mode based on a predetermined rule;
An imaging device comprising:
(2)
The imaging device according to (1), wherein the control unit randomly changes a timing of switching between the first data transmission mode and the second data transmission mode as the predetermined rule.
(3)
The imaging device according to (2), wherein the control unit randomly changes a timing of switching between the first data transmission mode and the second data transmission mode based on a pseudo-random number.
(4)
(1) the control unit changes timing of switching between the first data transmission mode and the second data transmission mode so as to avoid a predetermined period with reference to the first signal. An imaging device according to claim 1.
(5)
The imaging device according to (4), wherein the first signal is a ramp signal.
(6)
The control unit measures a noise amount of the second signal, and changes a timing of switching between the first data transmission mode and the second data transmission mode at a timing when the noise amount is minimized. The imaging device according to (1).
(7)
The control unit may control the first data transmission in a range where a minimum value of a switching time between the first data transmission mode and the second data transmission mode does not fall below a minimum value defined in a rule of the communication mode. The imaging device according to any one of (1) to (6), wherein a timing of switching between a mode and the second data transmission mode is controlled.
(8)
The imaging device according to any one of (1) to (7), further including a pixel array in which pixels that generate the analog signal are arranged in an array.
(9)
The imaging device according to any one of (1) to (8), wherein the communication mode is a mode conforming to a MIPI (Mobile Industry Processor Interface) standard.
(10)
Converting an analog signal to a digital signal;
Performing signal processing on the digital signal;
A first data transmission mode of a communication mode of a data signal to be output, using at least a first signal used for the conversion and a second signal processed in the signal processing; Controlling the timing of switching to the second data transmission mode having a lower transmission speed than the mode based on a predetermined rule;
A control method comprising:

100 imaging device 200 image 210 image 220 image 230 image 240 image

Claims (10)

A conversion unit that converts an analog signal into a digital signal;
A signal processing unit that performs signal processing on the digital signal,
A first data transmission mode of a communication mode of a data signal to be output, using at least a first signal used for conversion in the conversion unit and a second signal processed in the signal processing unit; A control unit that controls a timing of switching to a second data transmission mode having a lower transmission speed than the first data transmission mode based on a predetermined rule;
An imaging device comprising:   The imaging device according to claim 1, wherein the control unit randomly changes a timing of switching between the first data transmission mode and the second data transmission mode as the predetermined rule.   The imaging device according to claim 2, wherein the control unit randomly changes a timing of switching between the first data transmission mode and the second data transmission mode based on a pseudo-random number.   2. The control unit according to claim 1, wherein the control unit changes a switching timing between the first data transmission mode and the second data transmission mode so as to avoid a predetermined period with reference to the first signal. 3. An imaging device according to any one of the preceding claims.   The imaging device according to claim 4, wherein the first signal is a ramp signal.   The control unit measures a noise amount of the second signal, and changes a timing of switching between the first data transmission mode and the second data transmission mode at a timing when the noise amount is minimized. The imaging device according to claim 1.   The control unit may control the first data transmission in a range where a minimum value of a switching time between the first data transmission mode and the second data transmission mode does not fall below a minimum value defined in a rule of the communication mode. The imaging device according to claim 1, wherein timing of switching between a mode and the second data transmission mode is controlled.   The imaging device according to claim 1, further comprising a pixel array in which pixels that generate the analog signal are arranged in an array.   The imaging device according to claim 1, wherein the communication mode is a mode conforming to a Mobile Industry Processor Interface (MIPI) standard. Converting an analog signal to a digital signal;
Performing signal processing on the digital signal;
A first data transmission mode of a communication mode of a data signal to be output, using at least a first signal used for the conversion and a second signal processed in the signal processing; Controlling the timing of switching to the second data transmission mode having a lower transmission speed than the mode based on a predetermined rule;
A control method comprising: