JP2012235342A - Imaging apparatus and electronic camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for suppressing a lateral stripe noise caused by a noise mixed before sampling a pixel signal.SOLUTION: An imaging apparatus includes a pixel unit, a sample hold unit and a sampling adjustment unit. The pixel unit has a plurality of pixels, disposed in a two-dimensional shape, for photoelectrically converting incident light to generate pixel signals, and can read out the pixel signals from the pixels in a random access manner. The sample hold unit samples the pixel signals, and holds sampled signal values. The sampling adjustment unit groups the plurality of pixels into a plurality of pixel groups, to make the sample hold unit successively sample the pixel signals that are read out in the unit of each pixel group. The sampling adjustment unit specifies the readout sequence of the pixel groups to be discontinuous in a pixel array.

Description

  The present invention relates to an imaging apparatus that suppresses horizontal stripe noise that causes image quality degradation, and an electronic camera including the imaging apparatus.

  Conventionally, a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor generally samples and reads out a pixel signal simultaneously for each horizontal line (see, for example, Patent Document 1).

  In the read operation for each horizontal line, for example, when the reference voltage waveform for A / D conversion fluctuates for each horizontal line, it is known that the horizontal stripe noise occurs because the signal level fluctuates for each horizontal line. . This horizontal stripe noise becomes a cause of image quality degradation.

  Therefore, in Patent Document 1, lateral stripe noise is suppressed by performing arithmetic processing on pixel signals after A / D conversion.

JP 2006-157263 A

  However, Patent Document 1 does not sufficiently consider the suppression of horizontal stripe noise caused by noise mixed before sampling of pixel signals.

  In view of the above circumstances, an object of the present invention is to provide means for suppressing horizontal stripe noise caused by noise mixed before sampling of a pixel signal.

  An imaging apparatus according to a first invention includes a pixel unit, a sample hold unit, and a sampling adjustment unit. In the pixel portion, a plurality of pixels each generating a pixel signal by photoelectrically converting incident light are two-dimensionally arranged, and random access readout of the pixel signal from the plurality of pixels is possible. The sample hold unit samples the pixel signal and holds the sampled signal value. The sampling adjustment unit groups a plurality of pixels into a plurality of pixel groups, and causes the sample hold unit to sequentially sample the pixel signals read out in units of pixel groups. Then, the sampling adjustment unit specifies that the readout order of the pixel groups in the pixel array is discontinuous.

  In a second aspect based on the first aspect, the sampling adjustment unit specifies that the readout order of the pixel groups belonging to the same line in the pixel array is discontinuous.

  In a third aspect based on the first or second aspect, the sampling adjustment unit causes the sample hold unit to sequentially sample the pixel signals, and changes the timing for sampling the pixel signals in units of pixel groups.

  An imaging device according to a fourth invention includes a pixel unit, a sample hold unit, and a sampling adjustment unit. In the pixel portion, a plurality of pixels each generating a pixel signal by photoelectrically converting incident light are two-dimensionally arranged, and a random access readout of a pixel signal is possible from the plurality of pixels. The sample hold unit samples the pixel signal and holds the sampled signal value. The sampling adjustment unit groups a plurality of pixels into a plurality of pixel groups, specifies the readout order of pixel signals output from each pixel group in line units of the pixel array, and reads out the line units in the sample hold unit The pixel signals are sequentially sampled, and the timing for sampling the pixel signals is changed for each pixel group.

  An electronic camera according to a fifth aspect includes a photographing optical system and the imaging device according to any one of the first to fourth aspects.

  According to the present invention, it is possible to provide means for suppressing horizontal stripe noise caused by noise mixed before sampling of pixel signals.

Block diagram for explaining the internal configuration of the electronic camera 1 1 is a block diagram illustrating an internal configuration of an imaging apparatus that is an embodiment of the present invention. The figure which shows schematic structure of the image sensor 11 FIG. 6 is a diagram illustrating an example of a circuit configuration of a pixel 31 in the pixel portion 11a. The figure explaining the circuit structural example of the S & H circuit 11c of the image sensor 11. Conceptual diagram explaining the occurrence of horizontal stripe noise Conceptual diagram explaining the occurrence of horizontal stripe noise A flowchart showing an example of the operation of the electronic camera 1 The figure which illustrates conceptually the order which reads an optical signal per pixel group The figure which shows an example of the timing chart of the sampling of the optical signal of a pixel group Diagram showing an example of still image for recording The figure explaining the 1st modification

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating an internal configuration of the electronic camera 1. As shown in FIG. 1, the electronic camera 1 includes a photographing lens 10, an image sensor 11, a timing generator (hereinafter referred to as “TG”) 12, an analog front end unit (hereinafter referred to as “AFE”) 13, and image processing. Unit 14, RAM (Random Access Memory) 15, ROM (Read Only Memory) 16, display unit 17, recording interface unit (hereinafter referred to as "recording I / F unit") 18, operation unit 19, A release button 20, a CPU (Central Processing Unit) 21, and a bus 22 are provided.

  Among these, the AFE 13, the image processing unit 14, the RAM 15, the ROM 16, the display unit 17, the recording I / F unit 18, and the CPU 21 are connected to each other via a bus 22.

  The taking lens 10 is composed of a plurality of lens groups including a focus lens and a zoom lens. For the sake of simplicity, FIG. 1 shows the photographic lens 10 as a single lens. The photographing lens 10 is controlled by a lens driving device (not shown) according to an instruction from the CPU 21.

  The image sensor 11 captures a subject image by the photographing lens 10 and generates an analog pixel signal corresponding to the signal charge. In the present embodiment, the image sensor 11 is a CMOS type image sensor by an XY address scanning method.

  The TG 12 controls reading of pixel signals. Specifically, a control signal is transmitted to each of the image sensor 11 and the AFE 13 in accordance with an instruction from the CPU 21 to control drive timing.

  The AFE 13 is an analog front end circuit that performs signal processing on pixel signals generated by the image sensor 11. The AFE 13 performs adjustment (gain adjustment) of image pickup sensitivity (corresponding to so-called ISO sensitivity), A / D conversion, and the like.

  The image processing unit 14 reads the image data recorded in the RAM 15 and performs various image processing (gradation conversion processing, white balance processing, etc.). The RAM 15 temporarily records the digitized image signal output from the AFE 13 as image data. The ROM 16 is a non-volatile memory that stores a program for controlling the electronic camera 1 in advance.

  The display unit 17 displays a still image, a through image, an operation menu of the electronic camera 1, and the like. As the display unit 17, a liquid crystal display or the like can be appropriately selected and used.

  The recording I / F unit 18 provides an interface for recording processing with the detachable recording medium 30. The recording I / F unit 18 is formed with a connector (not shown) for connecting a detachable recording medium 30. In response to an instruction from the CPU 21, the recording I / F unit 18 accesses the recording medium 30 connected to the connector and performs still image recording processing and the like. The recording medium 30 is, for example, a non-volatile memory card. FIG. 1 shows the recording medium 30 after being connected to the connector.

  The operation unit 19 includes, for example, a command dial for command selection, a power button, and the like. Then, the operation unit 19 receives an instruction input for operating the electronic camera 1.

  The release button 20 receives an instruction input of a half-press operation and an instruction input of a full-press operation (shooting operation start).

  The CPU 21 is a processor that performs overall control of the electronic camera 1. The CPU 21 controls each part of the electronic camera 1 by executing a sequence program stored in advance in the ROM 16.

  Next, the imaging device 100 which is one embodiment of the present invention will be described. FIG. 2 is a block diagram illustrating the internal configuration of the imaging apparatus 100. The imaging apparatus 100 includes an image sensor 11, a TG 12, and an AFE 13. Note that the imaging apparatus 100 may incorporate the TG 12 and the AFE 13 in the image sensor 11.

  The image sensor 11 includes a pixel unit 11a, an amplifier circuit 11b, a sample and hold circuit (hereinafter referred to as “S & H circuit”) 11c, and an output amplifier 11d.

  FIG. 3 is a diagram illustrating a schematic configuration of the image sensor 11. In the pixel portion 11a, a plurality of pixels 31 each generating a pixel signal by photoelectrically converting incident light are two-dimensionally arranged. The pixel unit 11 a can perform random access readout of pixel signals from the plurality of pixels 31. Further, an optical black area (hereinafter referred to as “OB area”) is formed on the light receiving surface of the pixel portion 11a adjacent to the imaging area. In FIG. 3, the pixel unit 11a shows a plurality of pixels 31 arranged in a two-dimensional form of 4 rows and 4 columns for the sake of simplicity. It has many pixels consisting of 10,000 pixels. In the pixel portion 11a, each of the pixels 31 is provided with one of three color filters of R (red), G (green), and B (blue) in a Bayer array.

  The image sensor 11 further includes a plurality of pixels 31 arranged in rows (pixel groups) by a plurality of vertical signal lines 32 arranged one by one between two adjacent columns of pixels 31 and various control signals (pulse signals) described later. And a plurality of rows composed of a plurality of signal lines for supplying various control signals output from the vertical scanning circuit 33 to a plurality of pixels 31 (pixel group) in the same row. A signal line 34, a horizontal scanning circuit 35 that drives the S & H circuit 11c, and a horizontal signal line 36 that guides a pixel signal output from the S & H circuit 11c to the output amplifier 11d are provided.

  The amplifier circuit 11b amplifies the pixel signal output from the pixel unit 11a. The S & H circuit 11c is a pixel signal output from the amplifier circuit 11b (an optical signal including a photoelectric current component photoelectrically converted by the pixel 31 and a dark current component) or a pixel signal (dark signal) of a dark current component at reset. And the value of the sampled pixel signal is held as a voltage. Details of the internal configuration of the pixel 31 of the pixel unit 11a and the S & H circuit 11c will be described later. The output amplifier 11d amplifies the optical signal and the dark signal.

  The TG 12 illustrated in FIG. 2 includes a sampling adjustment unit 12a and a register 12b. The sampling adjustment unit 12a groups a plurality of pixels into a plurality of pixel groups. Then, the sampling adjustment unit 12a specifies that the pixel group readout order is discontinuous in the pixel array. For example, the sampling adjustment unit 12a specifies that the readout order of pixel groups belonging to the same line in the pixel array is discontinuous. Then, the sampling adjustment unit 12a causes the S & H circuit 11c to sequentially sample the pixel signals read in units of pixel groups. Here, the same line means, for example, one row in the horizontal direction (X direction) or one column in the vertical direction (Y direction) of the pixel unit 11a. The sampling adjustment unit 12a may perform the reading order of the pixel signals discontinuously in any direction of vertical, horizontal, and diagonal in the imaging region.

  The register 12b is a memory for the TG 12, and records data indicating the order in which pixel signals are read out in units of pixel groups. In other words, this data is data indicating the order in which the S & H circuit 11c samples the pixel signals read in units of pixel groups.

  The AFE 13 includes a CDS (correlated double sampling circuit) 13a, an analog gain unit 13b, and an A / D conversion unit 13c.

  The CDS (correlated double sampling circuit) 13a takes a difference between an optical signal read from the image sensor 11 and a dark signal, and removes reset noise, noise due to 1 / f noise, and the like. The analog gain unit 13b adjusts the gain of the pixel signal after the difference. The A / D conversion unit 13c converts the analog pixel signal after gain adjustment to a digital image signal.

  Next, the internal configuration of the pixel 31 of the pixel portion 11a of the image sensor 11 and the S & H circuit 11c will be described. FIG. 4 is a diagram illustrating a circuit configuration example of the pixel 31 of the pixel unit 11a. Each pixel of the pixel unit 11a includes a photodiode (PD), a floating diffusion (FD), a transfer transistor (TX), a reset transistor (FDRST), an amplification transistor (AMP), a selection transistor (SEL), Power supply (VDD). The transistors (TX, FDRST, AMP, and SEL) of the pixel unit 11a are nMOS transistors.

  The pixel unit 11 a includes a vertical signal line 32, a transfer signal line 51, a reset signal line 52, and a selection signal line 53. 3 receives, for example, a control signal (driving pulse) from the TG 12 and transfers a transfer pulse (ΦTX), a reset pulse (ΦFDRST), and a selection for each pixel row of the pixel unit 11a. Each pulse (ΦSEL) is output.

  The photodiode (PD) generates a signal charge corresponding to incident light by photoelectric conversion, and accumulates the signal charge. When receiving a transfer pulse (ΦTX) from the TG 12 via the transfer signal line 51, the transfer transistor (TX) transfers the signal charge accumulated in the photodiode (PD) to the floating diffusion (FD). The floating diffusion (FD) receives a signal charge and converts it into a voltage. The amplification transistor (AMP) amplifies and outputs a pixel signal corresponding to the voltage of the floating diffusion (FD). The reset transistor (FDRST) resets the voltage of the floating diffusion (FD) when receiving a reset pulse (ΦFDRST) from the TG 12 via the reset signal line 52. When the selection transistor (SEL) receives a selection pulse (ΦSEL) from the TG 12 via the selection signal line 53, the selection transistor (SEL) reads out the pixel signal of the amplification transistor (AMP) as a current. Further, the selection transistor (SEL) outputs the pixel signal to the amplifier circuit 11b via the vertical signal line 32.

  FIG. 5 is a diagram illustrating a circuit configuration example of the S & H circuit 11 c of the image sensor 11. In FIG. 5, the S & H circuit 11c includes an optical signal storage capacitor C-Sig, a dark signal storage capacitor C-Dark, an optical signal sampling switch SW1, and a dark signal sampling switch SW2.

  The optical signal sampling switch SW1 (hereinafter referred to as “switch SW1”) stores an optical signal as a voltage using an optical signal from a pixel selected according to a control signal received from the sampling adjustment unit 12a via the horizontal scanning circuit 35. This is a switch element that accumulates in the capacitor C-Sig. The switch SW1 is composed of, for example, an nMOS transistor. The switch SW1 is supplied with a sampling control signal (ΦSW1) for an optical signal from the sampling adjustment unit 12a via the horizontal scanning circuit 35. The switch SW1 is turned on when the sampling control signal (ΦSW1) is at a high level, and turned off when the sampling control signal (ΦSW1) is at a low level. The optical signal storage capacitor C-Sig stores an optical signal as a voltage when the switch SW1 is turned on. In addition, the sampling adjustment unit 12a transmits a control signal for reading the optical signal to the S & H circuit 11c via the horizontal scanning circuit 35, so that the optical signal stored in the optical signal storage capacitor C-Sig is output to the output amplifier. 11d.

  The dark signal sampling switch SW2 (hereinafter referred to as “switch SW2”) is a switch element that accumulates the dark signal at the time of reset as a voltage in the dark signal storage capacitor C-Dark. The switch SW2 is composed of an nMOS transistor, like the switch SW1. The switch SW2 is supplied with a dark signal sampling control signal (ΦSW2) from the sampling adjustment section 12a via the horizontal scanning circuit 35. The switch SW2 is turned on when the sampling control signal (ΦSW2) is at a high level, and is turned off when the sampling control signal (ΦSW2) is at a low level. The dark signal storage capacitor C-Dark stores the dark signal as a voltage when the switch SW2 is turned on. The sampling adjustment unit 12a transmits a dark signal read control signal to the S & H circuit 11c via the horizontal scanning circuit 35, whereby the dark signal accumulated in the dark signal storage capacitor C-Dark is output to the output amplifier 11d. Is output.

  Note that the imaging apparatus 100 according to the present embodiment is characterized by suppressing lateral stripe noise caused by noise mixed before sampling of pixel signals by the S & H circuit 11c. Therefore, here, the occurrence of horizontal stripe noise will be briefly described. 6 and 7 are conceptual diagrams for explaining the occurrence of horizontal stripe noise.

  FIG. 6A is a diagram schematically illustrating an example of a pixel signal (optical signal) output from the pixel unit 11 a of the image sensor 11. In FIG. 6A, for convenience of explanation, the optical signal for each line in the horizontal line of the pixel portion 11a is represented by one line. In FIG. 6A, the line numbers of horizontal lines nH, (n + 1) H, (n + 2) H, and (n + 3) H are spaced from each other. FIG. 6B is a diagram schematically illustrating an example of the external drive signal 1 that causes the horizontal stripe noise. FIG. 6C is a diagram schematically illustrating an example of the external drive signal 2 that causes the horizontal stripe noise. Note that the optical signal shown in FIG. 6A represents a state that is not affected by the external drive signal 1 and the external drive signal 2.

  FIG. 7A shows a case where the external drive signal 1 shown in FIG. 6B and the external drive signal 2 shown in FIG. 6C are superimposed on the optical signal shown in FIG. It is a figure which shows an optical signal typically. Here, the S & H circuit 11c samples the optical signal for each line in the horizontal line of the pixel portion 11a. In FIG. 7A, the timing at which SW1 of the S & H circuit 11c samples is indicated by an arrow. The sampling timing is the same for each line.

  Here, in the optical signal shown in FIG. 7A, noise is generated in accordance with the sampling timing by generating so-called crosstalk at a location where the level values of the external drive signal 1 and the external drive signal 2 change suddenly. Superimposed. In FIG. 7A, as an example, noise is picked up at the sampling timing SW1 in the horizontal lines nH and (n + 2) H. Therefore, in the optical signal shown in FIG. 7A, noise is superimposed on the horizontal lines nH and (n + 2) H.

  FIG. 7B is a diagram schematically showing a dark signal when the external drive signal 1 and the external drive signal 2 are superimposed on a dark signal (not shown). Here, it is assumed that the external drive signal 1 and the external drive signal 2 are superimposed on the external drive signal 1 and the external drive signal 2 shown in FIG. Here, the S & H circuit 11c samples the dark signal for each line of the pixel portion 11a. In FIG. 7B, the timing at which SW2 of the S & H circuit 11c samples is indicated by an arrow in the figure. The sampling timing is the same for each line. The dark signal shown in FIG. 7B does not pick up a noise signal at the sampling timing SW2 as an example, so that no noise is generated.

  FIG. 7C shows a conceptual diagram when a still image is generated by taking the difference CDS from the optical signal shown in FIG. 7A to the dark signal shown in FIG. 7B. Actually, the still image of FIG. 7C shows a state after taking the difference over all the lines. In FIG. 7C, for example, horizontal stripe noise occurs on the horizontal lines nH and (n + 2) H.

  Next, the operation of the electronic camera 1 in this embodiment will be described. FIG. 8 is a flowchart showing an example of the operation of the electronic camera 1. Here, after the power of the electronic camera 1 is turned on, when the operation unit 19 receives an instruction input of a still image shooting mode, the CPU 21 starts the flowchart shown in FIG.

  Step S101: The CPU 21 determines whether or not there is an instruction input (release operation) for a full press operation via the release button 20. If the instruction input operation (release operation) for the full press operation is not accepted, the CPU 21 repeats the process of step S101 again. When receiving an instruction input (release operation) instruction for full-press operation, the CPU 21 proceeds to step S102.

  Step S102: The CPU 21 drives the image sensor 11 by a rolling shutter system that controls the charge accumulation time for each line by address designation, and performs still image shooting. However, the CPU 21 reads out the pixel signal after the charge accumulation of all the pixels is completed.

  Note that the CPU 21 may drive the image sensor 11 by a global shutter system that controls the charge accumulation time of all the pixels at the same timing to perform still image shooting. In this case, the photodiodes (PD) of all the pixels of the pixel portion 11a are exposed at the same timing, and generate and accumulate signal charges corresponding to incident light by photoelectric conversion. Thereafter, the CPU 21 reads the pixel signal.

  Step S103: The CPU 21 instructs the sampling adjustment unit 12a of the TG 12 to specify the sampling order for each pixel group. The sampling adjustment unit 12a refers to the register 12b and specifies data indicating the order in which the optical signals are read out in units of pixel groups.

  FIG. 9 is a diagram conceptually illustrating the order of reading out optical signals in units of pixel groups. In FIG. 9, for easy understanding, a pixel portion (FIG. 9A) in which R, G, and B unit pixels are arranged in a two-dimensional form of 4 rows and 8 columns is used. Then, the sampling adjustment unit 12a outputs an optical signal from the pixel unit 11a to the amplifier circuit 11b using two pixels as a unit of the pixel group. The unit of the pixel group is not limited to two pixels, and may be N pixels (N is a natural number).

Here, the sampling adjustment unit 12a groups the pixel unit 11a into a plurality of pixel groups,
Designation is made so that the readout order of pixel groups belonging to the same line is discontinuous. For example, as shown in FIG. 9B, for example, the sampling adjustment unit 12a groups two pixels into 16 blocks from (a) to (p) using a pixel group as a unit. Then, the sampling adjustment unit 12a designates the order of reading the optical signals output from each block (pixel group). Here, for example, if the sampling adjustment unit 12a designates the order of reading sequentially for each line in the numerical order shown in FIG. 9C, the generated still image is likely to generate horizontal stripe noise. Therefore, in the present embodiment, the sampling adjustment unit 12a specifies, for example, the order of reading the optical signals output from each block (pixel group) in the numerical order shown in FIG. Thereby, since the noise which becomes a factor of a horizontal stripe noise is disperse | distributed to the whole screen, the horizontal stripe noise will be suppressed. In order to disperse noise over the entire image, the sampling adjustment unit 12a preferably specifies the reading order so that the blocks do not read adjacently. Further, the sampling adjustment unit 12a may specify the reading order by a statistical method such as random number calculation. Further, the blocks to be grouped by the sampling adjustment unit 12a are not limited to two horizontal rows as shown in FIG. 9D, but may be arbitrarily grouped every two vertical columns.

  Step S104: The sampling adjustment unit 12a transmits a selection pulse (ΦSEL) for reading out the pixel signals (optical signals) of the pixel group in the specified order via a horizontal scanning circuit (not shown). Thereby, the pixel unit 11a outputs the optical signal of the designated pixel group. Note that the sampling adjustment unit 12a also transmits a selection pulse (ΦSEL) for reading out a dark signal at the time of reset corresponding to the row of the designated pixel group before outputting the optical signal of the designated pixel group. Thereby, the pixel unit 11a outputs a dark signal at the time of designated reset.

  Step S105: The sampling adjustment unit 12a instructs the S & H circuit 11c to perform sample & hold processing. The S & H circuit 11c first samples the dark signal output from the amplifier circuit 11b and holds the sampled dark signal as a voltage. Subsequently, the S & H circuit 11c samples the optical signal of the pixel group output from the amplifier circuit 11b, and holds the sampled optical signal as a voltage.

  Step S106: The sampling adjustment unit 12a instructs the S & H circuit 11c to output the sampled optical signal and dark signal. The S & H circuit 11c outputs an optical signal and a dark signal to the output amplifier 11d at a predetermined timing. Further, the output amplifier 11d amplifies the optical signal and the dark signal. The amplified pixel signals (light signal and dark signal) are output to the CDS 13a of the AFE 13. The CDS 13a eliminates reset noise, 1 / f noise, and the like by taking the difference between the optical signal and the dark signal. The pixel signal processed by the CDS 13a is subjected to gain adjustment by the analog gain unit 13b. The A / D conversion unit 13c converts the pixel signal whose gain has been adjusted into a digital image signal. This digital image signal is temporarily recorded in the RAM 15.

  Step S107: The CPU 21 determines whether or not the pixel signals (light signals) of all the pixel groups have been read in the designated order. When the CPU 21 has not read out the optical signals of all the pixel groups in the designated order (step S107: No), the CPU 21 returns to step S104. On the other hand, when the CPU 21 reads out the optical signals of all the pixel groups in the designated order (step S107: Yes), the CPU 21 proceeds to step S108.

  FIG. 10 is a diagram illustrating an example of a timing chart of sampling of the optical signal of the pixel group. FIG. 10A shows a case where optical signals are read in the reading order shown in FIG. 9C for comparison. FIG. 10B shows a case where optical signals are read in the reading order shown in FIG. For simplicity, in FIG. 10, one waveform of the optical signal is drawn so as to correspond to two pixels. Further, for easy understanding, the external drive signal that causes the horizontal stripe noise is depicted as a signal having periodicity.

  In the case of FIG. 10A, the external drive signal is the timing (sampling point, upward arrow in the figure) for sampling the optical signals in the blocks (a, b, c, d) and (i, j, k, l). ) Causes crosstalk with the optical signal, and superimposes noise that causes horizontal stripe noise on the optical signal. Therefore, in this reading order, the noise is continuously superimposed on the optical signal, so that horizontal stripe noise is likely to occur.

  On the other hand, in the case of FIG. 10B, the external drive signal causes crosstalk with the optical signal at the sampling points in the blocks (a, j, c, l) and (b, k, e, n). Noise that causes horizontal stripe noise is superimposed on the. However, in this reading order, the noise is distributed over the entire image, so that the occurrence of horizontal stripe noise is suppressed.

  Step S108: The image processing unit 14 of the CPU 21 reads the image data of the still image recorded in the RAM 15, and performs various image processing (gradation conversion processing, white balance processing, etc.). Thereby, the CPU 21 generates a still image for recording.

  FIG. 11 is a diagram illustrating an example of a still image for recording. FIG. 11A shows a still image when pixel signals are read out in units of one line for comparison. In this case, the horizontal streak noise appears in the still image by continuously superimposing the noise mixed before sampling the pixel signal on one line. On the other hand, FIG. 11B shows a still image when pixel signals are read in the order of the designated pixel group. In this case, as described above, noise is dispersed throughout the image, and horizontal stripe noise in the still image is suppressed.

  Step S 109: The CPU 21 records a recording still image on the recording medium 30 via the recording I / F unit 18.

As described above, since the electronic camera 1 according to the present embodiment includes the imaging device 100, noise mixed before sampling of pixel signals is distributed over the entire image, so that horizontal stripe noise that causes image quality degradation can be suppressed. it can.
(First modification)
Next, a first modification of the electronic camera 1 of this embodiment will be described. In the first modification, the sampling adjustment unit 12a groups the pixel units 11a of the image sensor 11 into a plurality of pixel group regions, and specifies the order in which the optical signals output from each pixel group are read for each line. In this case, the sampling adjustment unit 12a causes the S & H circuit 11c to sequentially sample the optical signal line by line, and changes the timing (sampling point) for sampling the optical signal for each pixel group.

FIG. 12 is a diagram illustrating a first modification. FIG. 12A shows the output waveform of the optical signal of the pixel group. For example, the S & H circuit 11c designates the sampling point as one of (1) to (3) and turns on SW1. As a result, even if the TG 12 instructs the pixel unit 11a to output an optical signal in units of lines, the S & H circuit 11c changes the sampling point for each pixel group as shown in FIG. The occurrence of is likely to be suppressed. Note that the first modification may be applied to reading of a dark signal.
(Second modification)
Next, a second modification of the electronic camera 1 of this embodiment will be described. In the second modification, the sampling adjustment unit 12a causes the S & H circuit 11c to sequentially sample the optical signal and changes the timing (sampling point) for sampling the optical signal for each pixel group. That is, in the process of step S105 in the flowchart shown in FIG. 8, the S & H circuit 11c further changes the sampling point for each pixel group as shown in FIG. Thereby, compared with the process of step S105, the noise mixed before sampling of the optical signal by the S & H circuit 11c is further dispersed in the entire image, so that the occurrence of horizontal stripe noise is further easily suppressed. Note that the second modification may be applied to reading out a dark signal.

DESCRIPTION OF SYMBOLS 1 ... Electronic camera, 11a ... Pixel part, 11c ... S & H circuit, 12a ... Sampling adjustment part, 100 ... Imaging device

Claims (5)

A plurality of pixels, each of which photoelectrically converts incident light to generate a pixel signal, are two-dimensionally arranged, and a pixel unit capable of random access readout of the pixel signal from the plurality of pixels,
A sample and hold unit for sampling the pixel signal and holding the sampled signal value;
A sampling adjustment unit that groups the plurality of pixels into a plurality of pixel groups, and that sequentially samples the pixel signals read in units of pixel groups in the sample and hold unit;
The sampling adjustment unit includes:
An image pickup apparatus, wherein the pixel group is designated so that a reading order of the pixel group is not continuous. The imaging device according to claim 1,
The imaging apparatus is characterized in that the sampling adjustment unit specifies that the readout order of pixel groups belonging to the same line in the pixel array is discontinuous. In the imaging device according to claim 1 or 2,
The sampling adjustment unit causes the sample-and-hold unit to sequentially sample the pixel signals, and changes the timing for sampling the pixel signals in units of pixel groups. A plurality of pixels, each of which photoelectrically converts incident light to generate a pixel signal, are two-dimensionally arranged, and a pixel unit capable of random access readout of the pixel signal from the plurality of pixels,
A sample and hold unit for sampling the pixel signal and holding the sampled signal value;
A plurality of the pixels are grouped into a plurality of pixel groups, the readout order of the pixel signals output from each pixel group is designated in units of lines of a pixel array, and the pixels are read out in units of lines by the sample hold unit A sampling adjustment unit that sequentially samples the pixel signals and changes the timing of sampling the pixel signals in units of pixel groups;
An imaging apparatus comprising: Photographic optics,
The imaging apparatus according to any one of claims 1 to 4,
An electronic camera comprising:

Images