Imaging apparatus, imaging method, and computer program

Abstract

To provide an imaging apparatus capable of reducing the influence of periodic noise.SOLUTION: In an imaging device, a plurality of pixels, a noise signal after reset of the same pixel is read out in a first period to be a first noise signal, the noise signal after reset of the same pixel is read out in a second period different from the first period to be a second noise signal, the first noise signal and the second noise signal are added to generate an added noise signal, an image signal of the same pixel is read out in a third period to be a first image signal, and the image signal of the same pixel is read out in a fourth period different from the third period to be a second image signal, A control unit configured to add the first image signal and the second image signal to generate an added image signal, obtain a difference between the added image signal and the added noise signal, and control a difference between the first period and the second period to be different from a difference between the third period and the fourth period.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an imaging device, an imaging method, a computer program, and the like. [Background technology]

[0002] For example, as disclosed in Patent Document 1, an imaging unit has been proposed that reduces random noise contained in pixel signals and achieves high sensitivity by sampling pixel signals multiple times and averaging them (hereinafter referred to as multi-sampling). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-296423 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the configuration of Patent Document 1 has the advantage of being able to reduce random noise compared to conventional imaging units, it also has the problem that the more random noise is reduced, the more susceptible the imaging unit becomes to the effects of periodic noise. Patent Document 1 does not take into consideration the reduction of such periodic noise.

[0005] Therefore, one object of the present invention is to provide an imaging device that can reduce the influence of periodic noise. [Means for solving the problem]

[0006] An imaging device according to one aspect of the present invention comprises: A plurality of pixels; a noise signal after resetting of the same pixel is read out in a first period to obtain a first noise signal, and the noise signal after resetting of the same pixel is read out in a second period different from the first period to obtain a second noise signal; adding the first noise signal and the second noise signal to generate a summed noise signal; reading out the image signal of the same pixel in a third period to obtain a first image signal, and reading out the image signal of the same pixel in a fourth period different from the third period to obtain a second image signal; adding the first image signal and the second image signal to generate a sum image signal; A difference between the added image signal and the added noise signal is obtained, and a control means for controlling the difference between the first period and the second period so that the difference is different from the difference between the third period and the fourth period; The present invention is characterized by having the following. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an imaging device that can reduce the influence of periodic noise. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram schematically illustrating an example of the overall configuration of an imaging device 1000 according to a first embodiment of the present invention. [Figure 2] 1 is a diagram illustrating an example of the configuration of an image sensor 100 and its periphery according to a first embodiment of the present invention. [Figure 3] 2 is a diagram schematically illustrating an example of the configuration of a column circuit 204 included in the image sensor 100 according to the first embodiment of the present invention. FIG. [Figure 4] 4 is a timing chart schematically showing an example of readout driving of pixel signals according to the first embodiment of the present invention. [Figure 5] 1 is a flowchart schematically illustrating an example of an operation flow of the imaging device 1000 according to the first embodiment of the present invention. [Figure 6] 10 is a timing chart schematically showing an example of readout driving of pixel signals according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. In each drawing, the same members or elements are designated by the same reference numerals, and duplicate descriptions will be omitted or simplified.

[0010] <Embodiment 1> Fig. 1 is a diagram schematically illustrating an example of the overall configuration of an image capture device 1000 according to a first embodiment of the present invention. Note that some of the functional blocks illustrated in Fig. 1 are realized by causing a CPU or the like serving as a computer included in the image capture device 1000 to execute a computer program stored in a memory serving as a storage medium.

[0011] However, some or all of these functions may be implemented by hardware. Examples of hardware that can be used include dedicated circuits (ASICs) and processors (reconfigurable processors, DSPs). Furthermore, the functional blocks shown in Figure 1 do not have to be built into the same housing, and may be configured as separate devices connected to each other via signal paths.

[0012] Reference numeral 100 denotes an image sensor. The image sensor 100 is composed of a pixel group 200 (described later) and converts an optical image incident through a lens 102 (described later) into an electrical signal and transfers it to a signal processing circuit 101 (described later). Reference numeral 101 denotes a signal processing circuit. The signal processing circuit 101 processes the signal from the image sensor 100 and generates a captured image and an image for focus detection.

[0013] Reference numeral 102 denotes a lens. The lens 102 is driven by a lens control unit 103 (described later) to perform zoom control, focus control, aperture control, etc., and forms an incident optical image on the imaging element 100.

[0014] Reference numeral 103 denotes a lens driving unit that controls the lens 102. Reference numeral 104 denotes a CPU serving as a computer. The CPU 104 functions as a control means that executes control steps for the drive timing of the image sensor and control steps for a noise detection unit 109 and a lens control unit 103, which will be described later. Reference numeral 105 denotes a memory that is used to record image data and computer programs.

[0015] Reference numeral 106 denotes a recording unit, which is used to read and write image data to a semiconductor memory or the like. Reference numeral 107 denotes a display unit, which displays information such as the exposure conditions of the imaging device 1000 and image data. Reference numeral 108 denotes an operation unit, which is made up of buttons, dials, etc., and allows settings of the imaging device 1000 to be made.

[0016] Reference numeral 109 denotes a noise detection unit. The noise detection unit 109 detects noise signals, such as periodic noise, applied to the imaging device 1000 from, for example, an image output from an imaging element. Furthermore, the noise detection unit 109 functions as noise detection means for detecting the frequency of the detected noise signal.

[0017] 2 is a diagram schematically illustrating an example of the configuration of the image sensor 100 and its surroundings according to the first embodiment of the present invention. 200 denotes a pixel group, in which pixels 201 (described later) are arranged in a matrix. Each pixel 201 has a photoelectric conversion unit, a transistor, etc.

[0018] Each pixel 201 may have multiple photoelectric conversion units. Focus detection may be performed by comparing image A and B signals obtained by photoelectrically converting light from different exit pupils obtained by the multiple photoelectric conversion units. Such an image sensor is called an image plane phase difference detection type image sensor. A signal obtained by adding the image A and B signals from the multiple photoelectric conversion units can be used as an image signal for imaging (image signal for display).

[0019] Reference numeral 202 denotes a vertical scanning circuit. The vertical scanning circuit 202 supplies drive signals that control the transistors included in each pixel 201. These drive signals are common to multiple pixels in each row. Reference numeral 203 denotes column signal lines. At least one column signal line 203 is connected to each pixel column, and transfers the signal of each pixel to a column circuit 204, which will be described later.

[0020] The column circuit 204 performs processing such as amplification of the signal of each pixel 201 read out via the column signal line 203, analog multi-sampling, and analog-to-digital conversion (hereinafter referred to as AD conversion).

[0021] Reference numeral 205 denotes a reference signal generating circuit. The reference signal generating circuit 205 supplies a reference signal having a predetermined slope waveform to a plurality of column circuits 204. An AD conversion unit in the column circuit 204 then performs AD conversion by comparing the signal of the pixel 201 with the reference signal having the predetermined slope waveform.

[0022] Reference numeral 206 denotes a horizontal scanning circuit. The horizontal scanning circuit 206 transfers signals of the pixels 201 processed by the column circuit 204 to the signal processing circuit 101. Reference numeral 207 denotes a register group. The register group 207 is controlled by signals from the CPU 104 (described later) and stores settings such as a predetermined operation mode. The settings in the register group 207 include settings for ΔN, ΔS, ΔT, etc. (described later).

[0023] A timing generator 208 operates the vertical scanning circuit 202 and the horizontal scanning circuit 206 based on the settings stored in the register group 207.

[0024] FIG. 3 is a diagram schematically illustrating an example of the configuration of the column circuit 204 included in the image sensor 100 according to the first embodiment of the present invention. The column circuit 204 in FIG. 3 includes a signal amplifier, an analog multi-sampling unit, an AD converter, and the like.

[0025] Reference numeral 301 denotes a current source, which is connected to a column signal line 203 via a switch 302 (described later) and controls the current of the column signal line 203. Reference numeral 302 denotes a switch, which is disposed between the column signal line 203 and the current source 301 and switches between a supply state and a non-supply state of a bias current from the current source 301. The bias current is put into a supply state by setting a drive signal supplied to the gate of the switch 302 to a High level.

[0026] Reference numerals 303a and 303b denote first transfer switches. The first transfer switches 303a, 303b, etc. may be collectively referred to as first transfer switches 303. By setting the drive signals supplied to the gates of the first transfer switches 303a and 303b to a High level, the signals of the pixels 201 connected to the column signal line 203 can be held in sample-and-hold capacitors 304a and 304b, respectively, as described below.

[0027] Although FIG. 3 shows an example in which there are two first transfer switches 303, 303a and 303b, the two 303a and 303b may be reduced to one, or three or more.

[0028] Reference numerals 304a and 304b denote sample and hold capacitors. The sample and hold capacitors 304a and 304b may be collectively referred to as the sample and hold capacitor 304. The sample and hold capacitors 304a and 304b are capacitors that temporarily hold the signals of the pixel 201 supplied by the first transfer switches 303a and 303b, respectively.

[0029] Although FIG. 3 shows an example in which there are two sample-and-hold capacitors 304, 304a and 304b, the number of sample-and-hold capacitors 304 is implemented according to the number of first transfer switches 303, so there may be one or three or more.

[0030] Also, 305a and 305b are second transfer switches. Note that the second transfer switches 305a, 305b, etc. may be collectively referred to as second transfer switch 305. By setting the drive signals supplied to the gates of the second transfer switches 305a and 305b to a High level, the signals held in the sample-and-hold capacitors 304a and 304b can be output to the comparator 306, which will be described later.

[0031] 3 shows an example in which there are two second transfer switches 305a and 305b as the second transfer switch 305. However, the number of second transfer switches 305a and 305b may be one or three or more as long as they are implemented in accordance with the number of first transfer switches 303a and 303b.

[0032] When there are multiple second transfer switches 305a and 305b, the drive signals of the multiple second transfer switches are set to high level to average the multiple signals held in the corresponding multiple sample-and-hold capacitors, and then output to the comparator 306, thereby achieving an analog multi-sampling function.

[0033] Reference numeral 306 denotes a comparator. The comparator 306 compares a reference signal having a predetermined slope waveform from the reference signal generating circuit 205 with the signal from the pixel 201 obtained via the second transfer switch, and outputs the comparison result to an output node as an AD converted output. Reference numeral 307 denotes a switch. The switch 307 switches the comparator 306 between an operating state and a non-operating state. The comparator 306 can be put into an operating state by setting the drive signal supplied to the gate of the switch 307 to a High level.

[0034] FIG. 4 is a timing chart showing an example of readout driving of pixel signals according to the first embodiment of the present invention. The sequence of the analog multi-sampling function using the sample and hold capacitors (304a and 304b) according to the first embodiment will be described with reference to FIG.

[0035] In the example of FIG. 4, a signal (noise signal N) obtained immediately after resetting the pixel 201 is read out during a readout period T1, and a photoelectric conversion signal (image signal S) of the pixel 201 is read out during a readout period T2.

[0036] First, at time t1, the gate drive signals of the first transfer switch 303a (denoted as SW_303a in FIG. 4. Hereinafter, other switches will also be similarly denoted with "SW_" in FIG. 4) and the first transfer switch 303b are set to a High level.

[0037] This connects the column signal line 203 and the sample and hold capacitor 304, and the noise signal N after the pixel 201 is reset begins to accumulate in the sample and hold capacitors 304a and 304b (referred to as SH capacitors 304a and 304b in FIG. 4), respectively.

[0038] Then, at time t2 after the signal settling time has elapsed, the gate drive signal of the first transfer switch 303a is set to low level, thereby holding and fixing the noise signal Na in the sample and hold capacitor 304a. Here, the period from time t1 to time t2 is called the first period. Also, the noise signal Na read out during the first period after resetting the pixel is called the first noise signal.

[0039] Furthermore, at time t3, the gate drive signal of the first transfer switch 303b is set to low level, thereby finalizing the noise signal Nb in the sample and hold capacitor 304b. Here, the period from time t1 to time t3 is called the second period. The second period is different from the first period. Also, the noise signal Nb read out from the same pixel after resetting during the second period is called the second noise signal. The interval between time t2 and time t3 (the difference between the first period and the second period) is called ΔN.

[0040] When three or more sample-and-hold capacitors 304 are provided, the noise reduction effect can be increased by shifting the determination times of as many noise signals N as possible.

[0041] That is, the gate drive signal of the first transfer switch 303 of a predetermined sample and hold capacitor 304i is set to low level at a timing that is shifted from the timing at which the noise signal N of the other sample and hold capacitors 304 is determined, thereby determining the noise signal Ni.

[0042] Next, at time t4, the gate drive signals of the second transfer switch 305a and the second switch 305b are set to High level, thereby connecting the two sample and hold capacitors 304a and 304b. As a result, the charges Na and Nb stored in the two sample and hold capacitors 304a and 304b are averaged, and the multi-sampled noise signal N is determined. That is, the first noise signal and the second noise signal are added together in this way to generate an added noise signal.

[0043] Thereafter, the noise signal N supplied to the comparator 315 is compared with a reference signal having a predetermined slope waveform and is AD converted until time t5. Following the noise signal N, the image signal S also undergoes similar signal processing after time t5.

[0044] That is, at time t5, the gate drive signals of the first transfer switch 303a and the first transfer switch 303b are set to high level, thereby connecting the column signal line 203 to the sample and hold capacitor 304. The image signal S, which is a pixel signal from the pixel 201, begins to be accumulated in the sample and hold capacitors 304a and 304b.

[0045] Then, at time t6 after the signal settling time has elapsed, the gate drive signal of the first transfer switch 303a is set to low level, thereby settling the image signal Sa in the sample and hold capacitor 304a. Here, the period from time t5 to time t6 is called a third period. Also, the image signal Sa read out during the third period is called a first image signal.

[0046] Furthermore, at time t7, the gate drive signal of the first transfer switch 303b is set to low level, thereby finalizing the image signal Sb in the sample and hold capacitor 304b. Here, the period from time t5 to time t7 is referred to as a fourth period. The fourth period is different from the third period. Also, the image signal Sb of the same pixel read out during the fourth period is referred to as a second image signal.

[0047] When there are three or more sample-and-hold capacitors 304, the noise reduction effect can be increased by shifting the determination times of as many image signals S as possible, in the same way as with the noise signal N. Noise reduction is possible. Here, the interval between times t6 and t7 (the difference between the third period and the fourth period) is defined as ΔS.

[0048] Here, the sample and hold capacitor 304 functions as a holding means for holding the first noise signal and the second noise signal, respectively. The holding means also has a function for holding the first image signal and the second image signal, respectively. In the first embodiment, the holding means can hold analog signals such as charge signals.

[0049] Next, at time t8, the gate drive signals of the second transfer switches 305a and 305b are set to High level, connecting the two sample and hold capacitors 304a and 304b. As a result, the charges Sa and Sb accumulated in the two sample and hold capacitors 304a and 304b are averaged, and the multi-sampled image signal S is determined. That is, the first image signal and the second image signal are added together in this manner to generate an added image signal.

[0050] The multi-sampled image signal S is then propagated to the subsequent comparator 315. The image signal S supplied to the comparator 315 is compared with a reference signal having a predetermined gradient waveform and is AD converted until time t9 (when the noise signal of the next pixel is read out).

[0051] The signal processing circuit 101 takes the difference between the AD converted noise signal N (added noise signal) and image signal S (added image signal) and converts it into an image signal for imaging. That is, by obtaining the difference between the added image signal and the added noise signal, an image signal for imaging from which noise has been removed is generated. The above is an example of generating an image signal for imaging using the analog multi-sampling function in this embodiment.

[0052] Next, we will explain sensitivity to periodic noise (noise sensitivity). In the image pickup device 1000 shown in Figure 2, periodic noise has a negative effect on the image, mainly appearing as stripes. As a premise, we assume that the image pickup image signal is generated from the difference between the image signal S and the noise signal N, and that the determination times of the noise signals Na and Nb and the image signals Sa and Sb are t2, t3, t6, and t7, respectively.

[0053] As mentioned above, the interval between time t2 and time t3 (the difference between the first period and the second period) is ΔN, the interval between time t6 and time t7 (the difference between the third period and the fourth period) is ΔS, and the interval between the determination time t2 of the noise signal Na and the determination time t6 of the image signal Sa is ΔT.

[0054] In this embodiment, the difference (ΔN) between the first and second periods is controlled to be different from the difference (ΔS) between the third and fourth periods, and the difference (ΔS) between the third and fourth periods is controlled to be greater than the difference (ΔN) between the first and second periods.

[0055] Here, assuming that the periodic noise added to the image is a single-frequency sine wave and the noise frequency is f, the periodic noise superimposed on the pixel signal at time t can be calculated using the following equation (1).

number

[0056] Here, assuming that time t2 is t for convenience, the influence (noise sensitivity) of periodic noise given to pixel signals determined at times t2 to t6 can be calculated by the following equations (2) to (5), respectively.

number

number

number

number

[0057] Assuming that multi-sampled pixel signals are ideally averaged, the noise N and the periodic noise added to the image signal S can be calculated as shown in the following equations (6) and (7) by averaging equations (2) and (3), and equations (4) and (5), respectively.

number

number

[0058] Since the image signal for imaging is calculated by the signal processing circuit 101 as the difference between the noise signal N and the image signal S, the signal finally added to the image signal for imaging is calculated as the difference between equations (6) and (7). Rearranging this and extracting the terms related to the gain of noise sensitivity, the following equations (8) and (9) are obtained. 1 / 2 x G 1 / 2 ...Equation (8) G=4+2[cos{2π f(ΔN)}+cos{2π f(ΔS)}-cos{2π f(ΔT)}-cos{2π f(ΔT-ΔS)}-cos{2π f(ΔT+ΔS)}-cos{2π f(ΔT+ΔN-ΔS)}] ...Equation (9)

[0059] The variables in equation (9) are the noise frequency f and the differences ΔN, ΔS, and ΔT between the signal confirmation times. Therefore, the influence of periodic noise (noise susceptibility) can be arbitrarily changed by adjusting the differences ΔN, ΔS, and ΔT between the signal confirmation times.

[0060] Here, the noise susceptibility equations (1) to (9) each take a value between 0 and 2. Because noise susceptibility is a gain, the lower this value, the stronger the resistance to periodic noise. Therefore, it is possible to reduce noise susceptibility by adjusting the differences ΔN, ΔS, and ΔT between the signal determination times.

[0061] For example, when ΔT + ΔN = ΔS, the value of the cosine wave in the final term of equation (9) is -1, so noise susceptibility can be reduced regardless of the noise frequency f. That is, noise susceptibility can be reduced by controlling the difference (ΔS) between the third and fourth periods to be the sum of the difference (ΔT) between the end of the third period (t6) and the end of the first period (t2) and the difference (ΔN) between the first and second periods.

[0062] Similarly, the noise sensitivity in equations (8) and (9) can be reduced by the relationship between the differences ΔN, ΔS, and ΔT between various other signal determination times, regardless of the noise frequency f.

[0063] For example, the difference (ΔS) between the third period and the fourth period may be controlled to be the same as the difference between the end of the third period (t6) and the end of the second period (t3).

[0064] However, in this embodiment, as shown in Fig. 4, the interval ΔN between time t2 and time t3 is controlled to satisfy ΔN<ΔT. That is, the difference (ΔT) between the end of the third period (t6) and the end of the first period (t2) is controlled to be larger than the difference (ΔN) between the first period and the second period.

[0065] Note that noise susceptibility may be similarly reduced by adjusting only ΔS, which is not constrained. That is, noise susceptibility may be reduced by changing only the difference (ΔS) between the third period and the fourth period.

[0066] Next, an example of the operation flow of the imaging device 1000 will be described with reference to Fig. 5. Fig. 5 is a flowchart that schematically shows an example of the operation flow of the imaging device 1000 according to the first embodiment of the present invention. Note that the CPU 104 or the like executes a computer program stored in memory, thereby sequentially performing the operations of the steps in the flowchart of Fig. 5.

[0067] First, in step S101, when a drive mode is selected in the imaging device 1000, it is determined whether or not periodic noise is present in the image output from the imaging device 1000. The determination of whether or not periodic noise is present is performed by the noise detection unit 109 or the like. If it is determined in step S101 that periodic noise is present, the process proceeds to step S103, and if it is determined that periodic noise is not present, the process proceeds to step S102.

[0068] In step S102, since there is no need to reduce periodic noise, the differences ΔN, ΔS, and ΔT between the signal determination times are determined according to the selected drive mode.

[0069] On the other hand, in step S103, the noise detection unit 109 calculates the frequency of the periodic noise contained in the image output from the image capturing device 1000 in order to reduce the periodic noise.

[0070] In step S104, the optimum differences ΔN, ΔS, and ΔT between the signal determination times for reducing noise susceptibility are determined from equations (8) and (9) based on the frequency of the periodic noise calculated in step S103.

[0071] That is, based on the frequency of the noise signal detected by the noise detection means, at least one of the difference (ΔN) between the first period and the second period, the difference (ΔS) between the third period and the fourth period, and the difference between the end of the third period (t6) and the end of the first period (t2) is determined.

[0072] In step S105, the differences ΔN, ΔS, and ΔT between the signal determination times calculated in step S202 or step S104 are transmitted to and set in the register group 207 under the control of the CPU 104.

[0073] In step S106, the imaging device 1000 controls the lens 102 and the like using the lens control unit 103 based on the settings of the register group 207, thereby performing exposure control (control of the accumulation time in the imaging element, control of the lens aperture, etc.).

[0074] In step S107, the pixel signals of the pixels 201 that have been photoelectrically converted and accumulated as a result of exposure control in step S106 are read out to the signal processing circuit 101 based on the settings of the register group 207 (ΔN, ΔS, ΔT, etc.).

[0075] In step S108, the read pixel signals are subjected to various image corrections and development processes by the signal processing circuit 101, thereby completing the image capturing operation of the imaging device 1000. The processing flow in FIG. 5 is executed at a predetermined cycle, thereby acquiring a moving image.

[0076] As described above, according to this embodiment, the pixel signal is sampled multiple times at different times using the analog multi-sampling function, thereby achieving the effect of reducing random noise using the multi-sampling function.

[0077] Furthermore, by setting (adjusting) a combination of ΔN, ΔS, ΔT, etc., it is possible to reduce the influence of the noise frequency f while also reducing noise susceptibility. Furthermore, by calculating the frequency of the periodic noise using the noise detection unit 109, it is possible to further reduce noise susceptibility to a specific frequency f.

[0078] <Embodiment 2> Next, referring to FIG. 6, noise susceptibility reduction by digital multi-sampling according to a second embodiment of the present invention will be described.

[0079] 6 is a timing chart showing an example of readout driving of pixel signals according to the second embodiment of the present invention. The sequence of the digital multi-sampling function of performing AD conversion multiple times in the comparator 306 in the second embodiment will be described with reference to FIG.

[0080] In the second embodiment, the first transfer switch 303, the second transfer switch 305, and the sample and hold capacitor 304 shown in FIG. 3 may each be one.

[0081] In the second embodiment, similarly to the first embodiment, a signal (noise signal N) obtained immediately after resetting the pixel 201 is read out during the readout period T1, and a photoelectric conversion signal (image signal S) of the pixel 201 is read out during the readout period T2.

[0082] The readout order may be reversed, i.e., the image signal S may be read out first and the noise signal N may be read out later, or the first and second periods may be provided after the third and fourth periods.

[0083] The noise signal N transferred to the column circuit 204 via the column signal line 203 at time t1 in FIG. 6 is compared in the comparator 306 with a reference signal having a predetermined slope from the reference signal generating circuit 205.

[0084] 6, the reference signal has a waveform with a predetermined slope at a predetermined period. At time t2 when the reference signal with the predetermined slope first falls below the noise signal N, the noise signal N is AD converted and determined as the noise signal Na. The noise signal Na is transferred to the signal processing circuit 101 and stored as a digital signal in a memory 105 or the like connected to the signal processing circuit 101 and capable of storing digital signals.

[0085] Thereafter, the reference signal returns to the reference voltage once, and after a predetermined time has elapsed, it is again compared with the noise signal N in the comparator 315 as a reference signal having a predetermined slope. Next, at the time t3 when the reference signal falls below the noise signal N, the noise signal N is AD converted and determined as the noise signal Nb. The noise signal Nb is transferred to the signal processing circuit 101 and stored as a digital signal in a memory 105 or the like connected to the signal processing circuit 101.

[0086] The digital noise signals Na and Nb transferred to and held in the signal processing circuit 101 are averaged and determined as a multi-sampled noise signal N. In this way, in this embodiment, a digital multi-sampling function is realized during AD conversion.

[0087] The interval between time t2 and time t3 is ΔN, as in embodiment 1. The noise signal Nb may be directly averaged with the noise signal Na stored in the memory 105 or the like connected to the signal processing circuit 101, without being stored as a digital signal in the memory 105 or the like.

[0088] Next, at time t5, the image signal S transferred to the column circuit 204 via the column signal line 203 is compared in the comparator 315 with a reference signal having a predetermined slope from the reference signal generating circuit 205. The time when the reference signal falls below the image signal S for the first time is set to t6, and the image signal S is AD converted and determined as the image signal Sa. The image signal S is then transferred to the signal processing circuit 101 and stored as a digital signal in the memory 105 or the like connected to the signal processing circuit 101.

[0089] Thereafter, the reference signal returns to the reference voltage, and after a predetermined time has elapsed, the reference signal is again compared with the image signal S by the comparator 315. Next, at the time t7 when the reference signal falls below the image signal S, the noise signal N is AD converted and determined as the image signal Sb, which is transferred to the signal processing circuit 101 and held as a digital signal in the memory 105 or the like connected to the signal processing circuit 101.

[0090] The image signal Sa and the image signal Sb transferred to and held in the signal processing circuit 101 are averaged and determined as the digitally multi-sampled image signal S in AD conversion. As in the first embodiment, the interval between time t6 and time t7 is designated as ΔN. Note that the image signal Sb may not be held as a digital signal in the memory 105 or the like, but may be directly averaged with the image signal Sa held in the memory 105 or the like.

[0091] Furthermore, the interval between the determination time t2 of the noise signal Na and the determination time t6 of the image signal Sa is set to ΔT. By performing such an operation, even in a configuration using a digital multi-sampling function, the noise susceptibility can be calculated using equations (8) and (9), as in the first embodiment.

[0092] Therefore, even when digital multi-sampling is performed in AD conversion, the noise sensitivity in equations (8) and (9) can be reduced by adjusting (setting) the differences ΔN, ΔS, and ΔT between the signal determination times, as in embodiment 1.

[0093] The present invention has been described above in detail based on its preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and combinations of the above embodiments are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0094] The present invention also includes those that realize the functions of the above embodiments using, for example, at least one processor such as a CPU, memory, or circuit (for example, ASIC). Also, multiple processors may be used to perform distributed processing.

[0095] In order to realize some or all of the control in the above-described embodiments, a computer program that realizes the functions of the above-described embodiments may be supplied to an imaging device or the like via a network or various storage media. Then, a computer (or a CPU, MPU, or the like) in the imaging device or the like may read and execute the program. In this case, the program and the storage medium storing the program constitute the present invention. The present invention also includes the following combinations.

[0096] (Configuration 1) An imaging device comprising: a plurality of pixels; and control means for reading out noise signals from the same pixel after resetting in a first period to generate a first noise signal, and reading out the noise signals from the same pixel after resetting in a second period different from the first period to generate a second noise signal, adding the first noise signal and the second noise signal to generate an added noise signal, reading out image signals from the same pixel in a third period to generate a first image signal, and reading out the image signals from the same pixel in a fourth period different from the third period to generate a second image signal, adding the first image signal and the second image signal to generate an added image signal, obtaining a difference between the added image signal and the added noise signal, and controlling so that the difference between the first period and the second period is different from the difference between the third period and the fourth period.

[0097] (Configuration 2) The imaging device according to configuration 1, further comprising holding means for holding the first noise signal and the second noise signal, respectively.

[0098] (Configuration 3) The imaging device according to configuration 2, wherein the holding means holds the first image signal and the second image signal, respectively.

[0099] (Configuration 4) The imaging device according to configuration 2 or 3, wherein the holding means is capable of holding an analog signal.

[0100] (Configuration 5) The imaging device according to configuration 2 or 3, wherein the holding means is capable of holding a digital signal.

[0101] (Configuration 6) An imaging device described in any one of configurations 1 to 5, characterized in that the noise detection means detects the frequency of the noise signal, and the control means determines at least one of the difference between the first period and the second period, the difference between the third period and the fourth period, and the difference between the end of the third period and the end of the first period based on the frequency detected by the noise detection means.

[0102] (Configuration 7) The imaging device according to any one of configurations 1 to 6, wherein the control means changes the difference between the third period and the fourth period.

[0103] (Configuration 8) The imaging device described in any one of configurations 1 to 7, characterized in that the control means controls the difference between the third period and the fourth period to be the same as the difference between the end of the third period and the end of the second period.

[0104] (Configuration 9) The imaging device described in any one of configurations 1 to 8, characterized in that the control means controls so that the difference between the third period and the fourth period is the sum of the difference between the end of the third period and the end of the first period and the difference between the first period and the second period.

[0105] (Configuration 10) The imaging device according to any one of configurations 1 to 9, wherein the control means is configured such that the difference between the third period and the fourth period is greater than the difference between the first period and the second period.

[0106] (Configuration 11) The imaging device described in any one of configurations 1 to 10, characterized in that the control means controls so that the difference between the end of the third period and the end of the first period is greater than the difference between the first period and the second period.

[0107] (Configuration 12) The imaging device according to any one of configurations 1 to 11, characterized in that the control means controls the imaging device so that the first period and the second period are provided after the third period and the fourth period.

[0108] (Method) An imaging method for controlling an imaging device having a plurality of pixels, the imaging method comprising the steps of: reading out noise signals from the same pixel after resetting in a first period to obtain a first noise signal; reading out the noise signals from the same pixel after resetting in a second period different from the first period to obtain a second noise signal; adding the first noise signal and the second noise signal to generate an added noise signal; reading out image signals from the same pixel in a third period to obtain a first image signal; reading out the image signals from the same pixel in a fourth period different from the third period to obtain a second image signal; adding the first image signal and the second image signal to generate an added image signal; obtaining a difference between the added image signal and the added noise signal; and controlling so that the difference between the first period and the second period is different from the difference between the third period and the fourth period.

[0109] (Program) A computer program for controlling each means of the imaging device according to any one of configurations 1 to 12 by a computer. [Explanation of symbols]

[0110] 100: Image sensor 101: Signal processing circuit 102: Lens 103: Lens control unit 104:CPU 105: Memory 106: Recording section 107: Display section 108:Operation unit 109: Noise detection unit

Claims

1. A plurality of pixels; a noise signal after resetting of the same pixel is read out in a first period to obtain a first noise signal, and the noise signal after resetting of the same pixel is read out in a second period different from the first period to obtain a second noise signal; adding the first noise signal and the second noise signal to generate a summed noise signal; reading out the image signal of the same pixel in a third period to obtain a first image signal, and reading out the image signal of the same pixel in a fourth period different from the third period to obtain a second image signal; adding the first image signal and the second image signal to generate a sum image signal; A difference between the added image signal and the added noise signal is obtained, and a control means for controlling the difference between the first period and the second period so that the difference is different from the difference between the third period and the fourth period; An imaging device comprising:

2. 2. The imaging device according to claim 1, further comprising holding means for holding the first noise signal and the second noise signal, respectively.

3. 3. The imaging device according to claim 2, wherein said holding means holds said first image signal and said second image signal, respectively.

4. 3. The imaging device according to claim 2, wherein the holding means is capable of holding an analog signal.

5. 3. The imaging device according to claim 2, wherein the holding means is capable of holding a digital signal.

6. a noise detection means for detecting the frequency of the noise signal; 2. The imaging device according to claim 1, wherein the control means determines at least one of a difference between the first period and the second period, a difference between the third period and the fourth period, and a difference between an end of the third period and an end of the first period based on the frequency detected by the noise detection means.

7. 2. The imaging device according to claim 1, wherein the control means changes the difference between the third period and the fourth period.

8. 2. The imaging device according to claim 1, wherein the control means controls the difference between the third period and the fourth period so that the difference between the end of the third period and the end of the second period is the same as the difference between the end of the third period and the end of the second period.

9. 2. The imaging device according to claim 1, wherein the control means controls the difference between the third period and the fourth period to be the sum of the difference between the end of the third period and the end of the first period and the difference between the first period and the second period.

10. 2. The imaging device according to claim 1, wherein the control means controls the difference between the third period and the fourth period to be greater than the difference between the first period and the second period.

11. 2. The imaging device according to claim 1, wherein the control means controls the image sensor so that a difference between an end of the third period and an end of the first period is greater than a difference between the first period and the second period.

12. 2. The imaging device according to claim 1, wherein the control means controls the imaging device so that the first period and the second period are provided after the third period and the fourth period.

13. 1. An imaging method for controlling an imaging device having a plurality of pixels, comprising: a noise signal after resetting of the same pixel is read out in a first period to obtain a first noise signal, and the noise signal after resetting of the same pixel is read out in a second period different from the first period to obtain a second noise signal; adding the first noise signal and the second noise signal to generate a summed noise signal; reading out the image signal of the same pixel in a third period to obtain a first image signal, and reading out the image signal of the same pixel in a fourth period different from the third period to obtain a second image signal; adding the first image signal and the second image signal to generate a sum image signal; A difference between the added image signal and the added noise signal is obtained, and a control step of controlling the difference between the first period and the second period to be different from the difference between the third period and the fourth period; An imaging method comprising:

14. A computer program for controlling each unit of the imaging device according to any one of claims 1 to 12 by a computer.

Images