JP5523068B2 - Solid-state imaging device, driving method of solid-state imaging device, and computer program - Google Patents

Description

  The present invention relates to a solid-state imaging device, a driving method for a solid-state imaging device, and a computer program, and is particularly suitable for use in reading an electric charge obtained by photoelectric conversion to form an image.

  In an interline solid-state imaging device having a large number of pixels, generally, a method of reading out charges of all pixels by performing partial reading a plurality of times, that is, a reading method in which one frame is composed of a plurality of fields is used (Patent Document). 1). Thus, when reading out image signals in a plurality of fields, if there is a gap on the back of the lens barrel or the imaging device, light leaked from this gap (hereinafter referred to as light leakage) even in a light-shielded state. When exposure is performed, a larger offset component is applied to a field whose reading order is later. For this reason, when the fields are combined to form one frame, a luminance step occurs for each line.

  FIG. 9 shows a conventional imaging sequence in such a readout method. FIG. 9 shows that time advances in the direction of the axis of time T (arrow). In FIG. 9, the first stage shows the operation of the mechanical shutter, the second stage shows the operation of the electronic shutter, and the third stage shows the field output from the image sensor. Until time t0, the electric charge remaining in the photodiode is swept away toward the substrate by the electronic shutter pulse. Exposure is performed from time t0 until the mechanical shutter is closed at time t1. From time t2 to time t6, charges in the A field (Afi), B field (Bfi), C field (Cfi), D field (Dfi), E field (Efi), and F field (Ffi) are sequentially read out. Then, the read charge is transferred through the vertical charge transfer path and the horizontal charge transfer path, and is output as a voltage from the output unit.

  At this time, the time t1 to t2 is the light leakage accumulation time in the A field, the time t1 to t3 is the light leakage accumulation time in the B field, the time t1 to t4 is the light leakage accumulation time in the C field, and the time t1 to t5 is This is the accumulation time of light leakage in the D field. The time t1 to t6 is the light leakage accumulation time in the E field, and the time t1 to t7 is the light leakage accumulation time in the F field.

FIG. 10 is a diagram showing the output level of each line when a uniform surface is imaged by a conventional method when there is light leakage from a lens barrel or the like using an image sensor for 6-field readout. Specifically, FIG. 10A shows an output level where signal processing is not performed, and FIG. 10B shows an output level after low pass filter processing.
In the A field (Afi), the reading order is the earliest, followed by reading out charges in the order of the B field (Bfi), C field (Cfi), D field (Dfi), E field (Efi), and F field (Ffi). . The offset component due to light leakage sequentially increases from the A field (Afi) and has a period of 6 fields, resulting in horizontal stripes every 6 lines on the image. In image processing, low-pass filter processing is performed in order to suppress sensitivity variations between pixels and noise components. However, as shown in FIG. 10 (b), even if low-pass filter processing is performed on the result shown in FIG. 10 (a), the level difference in luminance is reduced, but horizontal stripes every 6 lines still remain. Will be noticeable.

  Generally, two types of methods are used to deal with the luminance difference generated in this way. The first method is a method called black image subtraction. This method is a method of “capturing under the same shooting conditions as in the main exposure with the mechanical shutter closed, obtaining a black image, and subtracting the black image from the output image in the main exposure”. The second method calculates the correction signal of each field from the difference between the field with the least offset component due to light leakage and the other fields, and subtracts the correction signal from each field to reduce the offset component due to light leakage. This is a removal method (see Patent Document 2).

JP 2000-201355 A JP-A-2005-151168

However, in the first method (black image subtraction), the imaging apparatus must be exposed for the same time as the main exposure, and a very long shooting time is required particularly when shooting for a long time. Further, random noise increases by performing black image subtraction, which may lead to degradation of image quality.
In the second method (a method of subtracting the correction signal from each field), it is necessary to perform arithmetic processing on the output signal. For this reason, it is necessary to prepare a memory and a calculation device necessary for the calculation process, which leads to an increase in cost, and a time period from photographing to image output is required for the calculation time period. In addition, when there are many noise components on the image, such as when shooting with high sensitivity setting, the calculation accuracy of the correction signal cannot be sufficiently obtained. For this reason, there is a possibility that problems such as overcorrection and residual correction may occur.
The present invention has been made in view of the above problems, and an object of the present invention is to reduce the influence on the image quality of a luminance step caused by light leakage without performing measures by hardware or performing signal processing on an output signal.

A first aspect of the solid-state imaging device of the present invention, an image of one frame based on the charge photoelectrically converted by the photoelectric conversion means, N (N is integer) is divided into individual fields, for each divided field As a low-pass filter process to be performed on the image signal based on the charge read out by the reading means, the control means for controlling the reading order of the charge of the field at different timing, the control means for controlling the reading order of the charge of the field , Filter means for performing smoothing between adjacent pixels in the vertical direction of the image, and the control means outputs a K-th field (K is an integer equal to or greater than 1) as a K-th field and is output The n-th line (n is an integer equal to or greater than 1 and n) when the line read out as the first field is the first line. N) is, when n is an odd number, becomes the line to be read as the n field, if n is an even number, so as not to line read out from the n-th field, control the order of reading the charge of the field Then, a difference in average value of luminance due to light leakage between pixels adjacent in the vertical direction after the low-pass filter processing is performed is within a predetermined range in each of the lines. To do.
A second aspect of the solid-state imaging device of the present invention, an image of one frame based on the charge photoelectrically converted by the photoelectric conversion means, N (N is integer) is divided into individual fields, for each divided field As a low-pass filter process to be performed on the image signal based on the charge read out by the reading means, the control means for controlling the reading order of the charge of the field at different timing, the control means for controlling the reading order of the charge of the field , Filter means for performing smoothing between adjacent pixels in the vertical direction of the image, and the control means outputs a K-th field (K is an integer equal to or greater than 1) as a K-th field and is output The n-th line (n is an integer equal to or greater than 1 and n) when the line read out as the first field is the first line. N) is, when n is an even number, becomes the line to be read as the n field, if n is an odd number, so as not to line read out from the n-th field, control the order of reading the charge of the field Then, a difference in average value of luminance due to light leakage between pixels adjacent in the vertical direction after the low-pass filter processing is performed is within a predetermined range in each of the lines. To do.
A third aspect of the solid-state imaging device of the present invention, an image of one frame based on the charge photoelectrically converted by the photoelectric conversion means, 2N + 1 (N is integer) is divided into individual fields, for each divided field As a low-pass filter process to be performed on the image signal based on the charge read out by the reading means, the control means for controlling the reading order of the charge of the field at different timing, the control means for controlling the reading order of the charge of the field , Filter means for performing smoothing between adjacent pixels in the vertical direction of the image, and the control means outputs a K-th field (K is an integer equal to or greater than 1) as a K-th field and is output The nth line (n is an integer greater than or equal to 1) when the line read out as the first field is the first line above. N ≦ 2N + 1) is a line that is read as the nth field when n is 1 ≦ n ≦ 2N + 1 and is odd, and when n is 1 ≦ n ≦ 2N + 1 and is even, The luminance due to light leakage between adjacent pixels in the vertical direction after the low-pass filter processing is performed by controlling the readout order of the charges in the field so that the line is read as the (2N + 2-n) field. The difference between the average values is within a predetermined range for each of the lines .
A fourth aspect of the solid-state imaging device of the present invention, an image of one frame based on the charge photoelectrically converted by the photoelectric conversion means, 2N (N is integer) is divided into individual fields, for each divided field As a low-pass filter process to be performed on the image signal based on the charge read out by the reading means, the control means for controlling the reading order of the charge of the field at different timing, the control means for controlling the reading order of the charge of the field , Filter means for performing smoothing between adjacent pixels in the vertical direction of the image, and the control means outputs a K-th field (K is an integer equal to or greater than 1) as a K-th field and is output The n-th line (where n is an integer equal to or greater than 1) when the line read out as the first field is the first line above ≦ 2N), when n is 1 ≦ n ≦ N and is odd, or when n is N + 1 ≦ n ≦ 2N and is even, the line is read as the nth field, and n Is 1 ≦ n ≦ N and an even number, or when n is N + 1 ≦ n ≦ 2N and an odd number, the line is read as the (2N + 1−n) field, The difference in the average luminance due to light leakage between adjacent pixels in the vertical direction after the low-pass filter processing is controlled by controlling the readout order of the electric charges in the field is within a predetermined range in each of the lines. It is characterized by becoming .

  According to the present invention, the reading order of field image signals is controlled so that the difference in luminance between adjacent fields in the reading order is reduced. Therefore, it is possible to reduce the influence on the image quality of the luminance step caused by light leakage without taking measures by hardware or performing signal processing on the output signal.

It is a figure which shows the structure of an imaging device. It is a figure which shows the structure of a solid-state image sensor. It is a figure which shows a part of color filter array. It is a figure which shows the imaging sequence which concerns on 1st Embodiment. It is a figure which shows the output level of each line which concerns on 1st Embodiment. It is a figure which shows the imaging sequence which concerns on 2nd Embodiment. It is a figure which shows the 1st example of the output level of each line which concerns on 2nd Embodiment. It is a figure which shows the 2nd example of the output level of each line which concerns on 2nd Embodiment. It is a figure which shows the conventional imaging sequence. It is a figure which shows the output level of each conventional line.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
First, the first embodiment will be described. In the present embodiment, an image sensor that constitutes one frame with six fields will be described as an example.

FIG. 1 is a diagram illustrating an example of an outline of a system configuration of an imaging apparatus (solid-state imaging apparatus) using an imaging element.
In FIG. 1, an imaging apparatus 100 includes a lens unit 101 (lens), a lens driving unit 102, a mechanical shutter 103 (mechanical shutter), a diaphragm 104, and a mechanical shutter / diaphragm driving unit 105 (shutter / diaphragm driving unit). And a solid-state image sensor 106. Further, the imaging apparatus 100 includes a CDS / A / D circuit 107 (CDS / A / D), an imaging signal processing circuit 108, a timing generation unit 109, an overall control calculation unit 110, a first memory unit 111, A second memory unit 112 and a display unit 113 are provided. Further, the imaging apparatus 100 includes an external interface unit (external I / F unit) 114, a recording medium control interface unit (recording medium control I / F unit) 115, a recording medium 116, and an operation unit 117.

  The subject image that has passed through the lens unit 101 is adjusted to an appropriate amount of light by the aperture 104 and formed on the solid-state image sensor 106. The subject image coupled to the solid-state image sensor 106 is subjected to correlated double sampling, gain adjustment, and A / D conversion in the CDS / A / D circuit 107 to obtain R, G1, G2, and B signals. Are sent to the imaging signal processing circuit 108. The imaging signal processing circuit 108 performs various image signal processing such as low-pass filter processing, shading processing, and WB processing for reducing noise, various corrections, compression of image data, and the like.

  The lens driving unit 102 controls driving of the lens unit 101 such as zooming and focusing. The mechanical shutter 103 is a shutter mechanism having only a curtain corresponding to the rear curtain of a focal plane type shutter used in a single-lens reflex camera. The mechanical shutter 103 and the diaphragm 104 are driven and controlled by a mechanical shutter / diaphragm driving unit 105. The timing generator 109 outputs various timing signals to the solid-state imaging device 106 and the imaging signal processing circuit 108.

  The overall control calculation unit 110 controls the entire imaging apparatus 100 and performs various calculations. The first memory unit 111 temporarily stores image data. The recording medium control interface unit 115 records image data and the like on the recording medium 116 and reads image data and the like from the recording medium 116. The display unit 113 displays image data. The recording medium 116 is a detachable storage medium such as a semiconductor memory, and records image data and the like. The external interface unit 114 is an interface for communicating with an external computer G or the like. The second memory unit 112 stores a calculation result or the like in the overall control calculation unit 110. Information related to the driving conditions of the imaging device 100 set by the user via the operation unit 117 is sent to the overall control calculation unit 110, and the overall control calculation unit 110 controls the entire imaging device 100 based on these pieces of information. .

FIG. 2 is a diagram illustrating an example of a schematic configuration of the solid-state image sensor 106.
In FIG. 2, the solid-state imaging device 106 includes a photodiode 201, a vertical charge transfer path 202, a horizontal charge transfer path 203, an output unit 204, a buffer storage cell 205, and a transfer gate 206.
The vertical charge transfer path 202 includes electrodes V1 to V12 that are transfer electrodes to which drive pulses φV1 to φV12 are applied, respectively. The electrodes V 1, V 3, V 5, V 7, V 9, V 11 also serve as readout electrodes for reading out charges from the photodiode 201 to the vertical charge transfer path 202. The buffer storage cell 205 and transfer gate 206 at the final stage of the vertical charge transfer path 202 are configured to include transfer electrodes BS and TS to which drive pulses φBS and φTS are applied, respectively. The horizontal charge transfer path 203 includes electrodes H1 and H2, which are transfer electrodes to which two-phase drive pulses φH1 and φH2 are applied, respectively.

  The signal charge photoelectrically converted by the photodiode 201 is sent from the timing generator 109 to the vertical charge transfer path 202 by applying a read pulse to the electrodes V1, V3, V5, V7, V9, and V11. At this time, a field read by the electrode V1 is an A field, a field read by the electrode V3 is a B field, and a field read by the electrode V5 is a C field. Similarly, a field read by the electrode V7 is a D field, a field read by the electrode V9 is an E field, and a field read by the electrode V11 is an F field. The charges read by the electrodes V1, V3, V5, V7, and V9 are further transferred sequentially in the direction of the horizontal charge transfer path 203 by drive pulses φV1 to φV12, φBS, and φTS. The horizontal charge transfer path 203 transfers one row of signal charges transferred from the vertical charge transfer path 202 to the output unit 204 by two-phase drive pulses φH1 and φH2, and the output unit 204 transfers the signal charges transferred. Is converted to voltage and output.

FIG. 3 is a diagram illustrating an example of a part of the color filter array used in the solid-state image sensor 106. Here, the first color filter is red (R), the second color filter is green (G), the third color filter is green (G), and the fourth color filter is blue (B). Show. This array of color filter arrays is called a Bayer array, among the color filter arrays of primary colors, and is a color filter array having high resolution and excellent color reproducibility.
In FIG. 3, the first row is an A field that is composed of only the third color filter green (G) and the fourth color filter blue (B), and is read by the electrode V1. The second row is a B field that is composed of only red (R) of the first color filter and green (G) of the second color filter and is read out by the electrode V3. The third row is a C field that is composed of only the third color filter green (G) and the fourth color filter blue (B), and is read by the electrode V5. The fourth row is a D field that is composed only of red (R) of the first color filter and green (G) of the second color filter and is read by the electrode V7. The fifth row is an E field which is composed of only the third color filter green (G) and the fourth color filter blue (B) and is read out by the electrode V9. The sixth row is an F field which is composed of only the red (R) of the first color filter and the green (G) of the second color filter and is read out by the electrode V11. Similarly, in the seventh and subsequent rows, the A field, the B field, the C field,... And six fields are arranged in order in the image area.

Next, low-pass filter processing that is normally performed in the imaging signal processing circuit 108 (filter means) for noise reduction will be described. The output value of the pixel to be processed is X (i, j), and the output values of adjacent pixels in the vertical direction are X (i, j-2), X (i, j-1), and X (i, j), respectively. +1) and X (i, j + 2). Then, the output value Y (i, j) after the low-pass filter processing is expressed as in the following (Expression 1) (where i and j are integers of 0 or more).
Y (i, j) = {X (i, j-2) + 4 * X (i, j-1) + 6 * X (i, j) + 4 * X (i, j + 1) + X ( i, j + 2)} / 16 (Formula 1)
As an example, the result of applying (Equation 1) to the output value shown in FIG. When the output value of each line is (Afi, Bfi, Cfi, Dfi, Efi, Ffi) = (9, 11, 13, 15, 17, 19), the low pass filter processing of (Equation 1) is as follows: Adapted. The values after low-pass filter processing of each line are Afi ′, Bfi ′, Cfi ′, Dfi ′, Efi ′, and Ffi ′.

Afi ′ = {17 + 4 × 19 + 6 × 9 + 4 × 11 + 13} /16=12.8
Bfi ′ = {19 + 4 × 9 + 6 × 11 + 4 × 13 + 15} /16=11.8
Cfi ′ = {9 + 4 × 11 + 6 × 13 + 4 × 15 + 17} /16=13.0
Dfi ′ = {11 + 4 × 13 + 6 × 15 + 4 × 17 + 19} /16=15.0
Efi ′ = {13 + 4 × 15 + 6 × 17 + 4 × 19 + 9} /16=16.3
Ffi ′ = {15 + 4 × 17 + 6 × 19 + 4 × 9 + 11} /16=15.3

As can be seen from these calculation results, the conventional driving method as described in the background art cannot sufficiently reduce the luminance step by the low-pass filter processing of (Equation 1).
Therefore, in this embodiment, the low-pass filter processing of (Equation 1) is performed after reading the charges in each field in the following reading order so as to reduce the luminance step.
In the present embodiment, a case where the number of field divisions is N (N is a natural number of 3 or more) will be described. The K-th field to be read is the K-th field, the first line read as the first field on the image is the first row, the n-th line counted from it is the n-th row (n is an integer of 1 or more, n ≦ N). At this time, the function K (n) indicating the number of the field from which the n-th line is read is expressed by the following (formula 2).

When n is even K (n) = n and when n is odd K (n) ≠ n
Or when n is an even number K (n) ≠ n and when n is an odd number K (n) = n
... (Formula 2)
(Equation 2) is similarly applied to the arrangement order in the positive direction in the vertical direction and the arrangement order in the negative direction from the first field (A field). As described above, in this embodiment, when n is an odd number (even number), the line is read as the nth field, and when n is an even number (odd number), the line is not read from the nth field. The reading order of the field charges is determined.

  When the field division number N is N = 6, for example, lines to be read out are arranged in order on the image so as to satisfy (Equation 2). That is, the fifth field (E field), the second field (B field), the first field (A field), the fourth field (D field), the third field (C field), and the sixth field (F field). The lines to be read out are arranged in order.

  FIG. 4 is a diagram illustrating an example of an imaging sequence of the imaging apparatus 100 under the control of the overall control calculation unit 110 (control unit) when the field signals are read in the reading order according to (Equation 2). FIG. 4 shows that time advances in the direction of the axis of time T (arrow). In FIG. 4, the first stage shows the operation of the mechanical shutter 103, the second stage shows the operation of the electronic shutter, and the third stage shows a field output from the solid-state image sensor 106. Until time t0, the electric charge remaining in the photodiode 201 is swept away toward the substrate by the electronic shutter pulse. Exposure is performed from time t0 until mechanical shutter 103 is closed at time t1. Before the charge of the photodiode 201 is read, the vertical charge transfer path 202 and the horizontal charge transfer path 203 are driven at high speed during a period of time t1 to t2, so that dark current components generated in the vertical charge transfer path 202 are Unnecessary charges are swept away. At time t2, when a read pulse is applied to the electrode V9 from the timing generator 109 (readout means), the charge in the E field (described as Efi) is read out. The read charges are transferred through the vertical charge transfer path 202 and the horizontal charge transfer path 203, converted into a voltage by the output unit 204, and output. Subsequently, similarly, a readout pulse is sequentially applied from the timing generator 109 (reading means) to the electrodes V3, V1, V7, V5, and V11, and the charges in the following fields are read out. That is, charges in the B field (Bfi), A field (Afi), D field (Dfi), C field (Cfi), and F field (Ffi) are read out. Then, the read charges are transferred through the vertical charge transfer path 202 and the horizontal charge transfer path 203 and output as a voltage from the output unit 204.

FIG. 5 shows an example of the output level of each line when a uniform surface (a surface with uniform luminance) is imaged in a state where light leaks from a lens barrel and the like, and charges are read out in the imaging sequence shown in FIG. FIG. Specifically, FIG. 5A shows an output level output from the solid-state imaging device 106 and immediately before entering the imaging signal processing circuit 108 via the CDS / A / D circuit 107, and FIG. 5B shows imaging signal processing. The output level after low-pass filter processing is performed by the circuit 108 is shown.
Since there is light leakage, exposure is performed until charge is read out in each field after time t1 in FIG. 4, and this is superimposed on the signal component as an offset component. The offset component due to this light leakage becomes the largest in the F field with the slowest readout, then increases in the order of the C field, D field, A field, B field, and E field, resulting in a luminance step for each line.

  In the calculation of (Expression 1), the specific gravity of the influence of adjacent pixels (adjacent pixels) is large. For this reason, in accordance with this characteristic, the average value between adjacent pixels becomes the same output level in all lines, so that differential smoothing with adjacent pixels can be performed as shown in FIG. It will work effectively.

  In this embodiment, the reading order of either the even lines or the odd lines on the image is changed as compared with the conventional method of arranging on the image in the field order read out. In this embodiment, smoothing with a low-pass filter can be effectively performed in this way, and it is possible to reduce the luminance step.

  FIG. 4 shows an example in which the reading order of the even lines is fixed (not changed). Similarly, when the reading order of the odd lines is fixed, the arrangement order in which the smoothing by the low-pass filter is effectively applied is also shown. realizable. For example, when the field division number N = 6, for example, the charge of each line is read in the order of the first field, the fourth field, the third field, the sixth field, the fifth field, and the second field. be able to.

  As described above, in the present embodiment, the signal based on the charges read out by changing the reading order of the fields of the odd-numbered lines (even-numbered lines) and changing the reading order of all the fields of the even-numbered lines (odd-numbered lines). Low pass filter processing was performed on Specifically, when the low-pass filter processing is performed on the output signal output from the solid-state imaging device 106 by imaging the surface with uniform brightness, the signal difference between fields on the output image becomes a predetermined value or less. The reading order is as follows. In this embodiment, in this way, by changing the order of the fields to be read out so that the spatial frequency of the horizontal stripes due to light leakage is increased, the difference in luminance between the fields adjacent to each other in the reading order is changed before the reading order is changed. Can be made smaller. Therefore, in an image captured by a solid-state imaging device that performs a plurality of field readouts, the effects of luminance steps caused by light incident from gaps such as the lens barrel and the back surface of the imaging device on the image quality are measured by hardware measures and output signals. Can be reduced without signal processing.

In the present embodiment, an image sensor that constitutes one frame with six fields is shown as an example, but the same can be realized even if the number of divisions of one frame is other than six.
In the present embodiment, the reading order effective for reducing the luminance step is shown by the low-pass filter of (Expression 1), but a low-pass filter other than (Expression 1) may be used.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. This embodiment is different from the first embodiment mainly in the method for determining the field reading order. Therefore, in the description of the present embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals as those in FIGS.
In the present embodiment, the low-pass filter processing of (Equation 1) is performed after reading the charges in each field in the following reading order so that the luminance step is reduced.

  First, a case where the number of field divisions is an odd number (2N + 1 (N is an integer of 1 or more)) will be described. The K-th field to be read is the K-th field, the first line read as the first field on the image is the first row, the n-th line counted from it is the n-th row (n is an integer of 1 or more, n ≦ 2N + 1). At this time, the function K (n) indicating the order in which the n-th line is read is expressed by the following (Expression 3) and (Expression 4).

(1 ≦ n ≦ 2N + 1, where n is an odd number) K (n) = n (Expression 3)
(1 ≦ n ≦ 2N + 1, where n is an even number) K (n) = 2N + 2-n (Expression 4)

(Equation 3) and (Equation 4) are similarly applied regardless of the arrangement order of the positive direction in the vertical direction and the arrangement order of the negative direction, counting from the first field. .
For example, when the number of field divisions is 5 (N = 2), on the image, the first field, the fourth field, the third field, the second field, so as to satisfy (Equation 3) and (Equation 4), Lines read as the fifth field are arranged in order. In this case, K (1) = 1, K (2) = 4, K (3) = 3, K (4) = 2, and K (5) = 5. Similarly, when the number of field divisions is 9 (N = 4), on the image, the first field, the eighth field, the third field, the sixth field, the fifth field, the fourth field, the seventh field, Lines read out as the 2nd field and the 9th field are arranged in order. In addition, even if the number of field divisions is 3, 7, 11,..., If they are odd numbers represented by 2N + 1 (N is an integer of 1 or more), they are similarly arranged according to (Expression 3) and (Expression 4). By changing the order (reading order), the influence of the luminance step can be minimized.

  Next, a case where the number of field divisions is an even number (2N (N is an integer of 2 or more)) will be described. The K-th field to be read is the K-th field, the first line read as the first field on the image is the first row, the n-th line counted from it is the n-th row (n is an integer of 1 or more, n ≦ 2N). At this time, the function K (n) indicating the number of the field from which the n-th line is read is expressed by the following (Expression 5) to (Expression 8).

(1 ≦ n ≦ N, where n is an odd number) K (n) = n (Formula 5)
(1 ≦ n ≦ N, where n is an even number) K (n) = 2N + 1−n (Expression 6)
(N + 1 ≦ n ≦ 2N, where n is an odd number) K (n) = 2N + 1−n (Expression 7)
(N + 1 ≦ n ≦ 2N, where n is an even number) K (n) = n (Expression 8)

(Equation 5) to (Equation 8) are applied in the same way regardless of the arrangement order in the positive direction in the vertical direction or the arrangement order in the negative direction, counting from the first field. .
For example, when the number of field divisions is 6 (N = 3), the lines read as the first field, the fifth field, the third field, the fourth field, the second field, and the sixth field are sequentially displayed on the image. line up. In this case, K (1) = 1, K (2) = 5, K (3) = 3, K (4) = 4, K (5) = 2, K (6) = 6 Is 8 (N = 4), the first field is read as the seventh field, the third field, the fifth field, the fourth field, the sixth field, the second field, and the eighth field on the image. Lines are arranged in order. In addition, even if the number of field divisions is 4, 10, 12,..., They are similarly arranged according to (Expression 5) to (Expression 8) as long as they are even numbers represented by 2N (N is an integer of 2 or more). By changing the order (reading order), the influence of the luminance step can be minimized.

  The reading order of the above fields is derived from the result of simulating the reading order most effective for reducing the luminance step with the existing low-pass filter, and for any case where the number of field divisions is 3 or more. Is also effective.

  In FIG. 6, the number of field divisions is 6, and the imaging apparatus 100 performs imaging under the control of the overall control calculation unit 110 (control unit) when the field signals are read in the reading order according to (Equation 5) to (Equation 8). It is a figure which shows an example of a sequence. Since the operation from time t0 to t2 is the same as the operation described in FIG. 4, detailed description thereof is omitted here.

  At time t2, when a read pulse is applied to the electrode V3 from the timing generator 109 (read means), the charge in the A field (Afi) is read. The read charges are transferred through the vertical charge transfer path 202 and the horizontal charge transfer path 203, converted into a voltage by the output unit 204, and output. Subsequently, similarly, a readout pulse is sequentially applied from the timing generator 109 (reading means) to the electrodes V9, V5, V7, V3, and V11 to read out charges in the following fields. That is, charges in the E field (Efi), C field (Cfi), D field (Dfi), B field (Bfi), and F field (Ffi) are read out. Then, the read charges are transferred through the vertical charge transfer path 202 and the horizontal charge transfer path 203 and output as a voltage from the output unit 204.

FIG. 7 shows an example of the output level of each line when a uniform surface (a surface with uniform luminance) is imaged in a state where light leaks from a lens barrel or the like, and charges are read out in the imaging sequence shown in FIG. FIG. Specifically, FIG. 7A shows an output level output from the solid-state imaging device 106 and immediately before entering the imaging signal processing circuit 108 through the CDS / A / D circuit 107, and FIG. 7B shows imaging signal processing. The output level after low-pass filter processing is performed by the circuit 108 is shown.
As shown in FIG. 7B, in the present embodiment, the same effects as described in the first embodiment can be obtained regardless of the number of field divisions equal to or greater than three.

FIG. 8 shows an image of a uniform surface (a surface with uniform luminance) captured by a solid-state imaging device that forms one frame with five fields in a state where light leaks from a lens barrel or the like. FIG. 6 is a diagram illustrating an example of an output level of each line when electric charges are read out in an imaging sequence according to FIG. Specifically, FIG. 8A shows an output level output from the solid-state imaging device 106 and immediately before entering the imaging signal processing circuit 108 via the CDS / A / D circuit 107, and FIG. 8B shows imaging signal processing. The output level after low-pass filter processing is performed by the circuit 108 is shown. As shown in FIG. 8B, even if the solid-state image sensor other than the solid-state image sensor that constitutes one frame with six fields has the same effect as that of the case where the number of divisions of one frame is six.
In the present embodiment, the reading order effective for reducing the luminance step is shown by the low-pass filter of (Expression 1), but a low-pass filter other than (Expression 1) may be used.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

(Other examples)
The present invention is also realized by executing the following processing. That is, first, software (computer program) that realizes the functions of the above embodiments is supplied to a system or apparatus via a network or various storage media. Then, the computer (or CPU, MPU, etc.) of the system or apparatus reads and executes the computer program.

  DESCRIPTION OF SYMBOLS 100 Imaging device, 106 Solid-state image sensor, 108 Imaging signal processing circuit

Claims (11)

Reading means an image of one frame based on the charge photoelectrically converted, N (N is the integer) is divided into individual fields and reading charges of each field at different timings for each divided field in the photoelectric conversion means,
Control means for controlling the reading order of charges in the field ;
Filter means for performing smoothing between adjacent pixels in the vertical direction of the image as low-pass filter processing performed on the image signal based on the electric charge read by the reading means ;
The control means sets the Kth field (K is an integer equal to or greater than 1) as the Kth field, and the nth line when the line read as the first field on the output image is the first line. (N is an integer equal to or greater than 1 and n ≦ N). When n is an odd number, the line is read as the nth field. When n is an even number, the line is not read from the nth field. As described above, the difference in the average value of luminance due to light leakage between pixels adjacent in the vertical direction after the low-pass filter processing is controlled by controlling the readout order of the charges in the field is predetermined for each of the lines. A solid-state imaging device characterized by being in the range . Reading means an image of one frame based on the charge photoelectrically converted, N (N is the integer) is divided into individual fields and reading charges of each field at different timings for each divided field in the photoelectric conversion means,
Control means for controlling the reading order of charges in the field ;
Filter means for performing smoothing between adjacent pixels in the vertical direction of the image as low-pass filter processing performed on the image signal based on the electric charge read by the reading means ;
The control means sets the Kth field (K is an integer equal to or greater than 1) as the Kth field, and the nth line when the line read as the first field on the output image is the first line. (N is an integer equal to or greater than 1 and n ≦ N). When n is an even number, the line is read as the nth field. When n is an odd number, the line is not read from the nth field. As described above, the difference in the average value of luminance due to light leakage between pixels adjacent in the vertical direction after the low-pass filter processing is controlled by controlling the readout order of the charges in the field is predetermined for each of the lines. A solid-state imaging device characterized by being in the range . Reading means an image of one frame based on the charge photoelectrically converted, 2N + 1 (N is the integer) is divided into individual fields and reading charges of each field at different timings for each divided field in the photoelectric conversion means,
Control means for controlling the reading order of charges in the field ;
Filter means for performing smoothing between adjacent pixels in the vertical direction of the image as low-pass filter processing performed on the image signal based on the electric charge read by the reading means ;
The control means sets the Kth field (K is an integer equal to or greater than 1) as the Kth field, and the nth line when the line read as the first field on the output image is the first line. (N is an integer equal to or greater than 1 and n ≦ 2N + 1), but when n is 1 ≦ n ≦ 2N + 1 and is an odd number, the line is read as the nth field, and n is 1 ≦ n ≦ 2N + 1 In the case of an even number, the charge readout order of the field is controlled so that the line is read as the (2N + 2-n) field, and the vertical direction after the low-pass filter processing is performed. A solid-state imaging device characterized in that a difference in average value of luminance due to light leakage between adjacent pixels falls within a predetermined range in each of the lines . Reading means an image of one frame based on the charge photoelectrically converted, 2N (N is the integer) is divided into individual fields and reading charges of each field at different timings for each divided field in the photoelectric conversion means,
Control means for controlling the reading order of charges in the field ;
Filter means for performing smoothing between adjacent pixels in the vertical direction of the image as low-pass filter processing performed on the image signal based on the electric charge read by the reading means ;
The control means sets the Kth field (K is an integer equal to or greater than 1) as the Kth field, and the nth line when the line read as the first field on the output image is the first line. (N is an integer of 1 or more and n ≦ 2N),
When n is 1 ≦ n ≦ N and is odd, or when n is N + 1 ≦ n ≦ 2N and is even, the line is read as the nth field,
When n is 1 ≦ n ≦ N and an even number, or when n is N + 1 ≦ n ≦ 2N and is an odd number, the line is read as the (2N + 1−n) field. The difference in the average value of luminance due to light leakage between adjacent pixels in the vertical direction after the low-pass filter processing is controlled by controlling the readout order of the electric charges in the field is within a predetermined range in each of the lines. A solid-state image pickup device characterized by being placed inside . 5. The average value of luminance due to light leakage between adjacent pixels in the vertical direction after the low-pass filter processing is made to be the same in each of the lines. 6. The solid-state imaging device according to claim 1. A reading step the image of one frame based on the charge photoelectrically converted, N (N is the integer) is divided into individual fields and reads the respective fields of charge at different timings for each divided field in the photoelectric conversion means,
A control step for controlling the reading order of the charges in the field ;
As a low-pass filter process performed on the image signal based on the electric charge read out in the read-out step, a filter step of performing smoothing between adjacent pixels in the vertical direction of the image ,
In the control step, the Kth field (K is an integer equal to or greater than 1) is the Kth field, and the line read as the first field on the output image is the first line. (N is an integer equal to or greater than 1 and n ≦ N). When n is an odd number, the line is read as the nth field. When n is an even number, the line is not read from the nth field. As described above, the difference in the average value of luminance due to light leakage between pixels adjacent in the vertical direction after the low-pass filter processing is controlled by controlling the readout order of the charges in the field is predetermined for each of the lines. A method for driving a solid-state imaging device, wherein the solid-state imaging device is in a range of . A reading step the image of one frame based on the charge photoelectrically converted, N (N is the integer) is divided into individual fields and reads the respective fields of charge at different timings for each divided field in the photoelectric conversion means,
A control step for controlling the reading order of the charges in the field ;
As a low-pass filter process performed on the image signal based on the electric charge read out in the read-out step, a filter step of performing smoothing between adjacent pixels in the vertical direction of the image ,
In the control step, the Kth field (K is an integer equal to or greater than 1) is the Kth field, and the line read as the first field on the output image is the first line. (N is an integer equal to or greater than 1 and n ≦ N). When n is an even number, the line is read as the nth field. When n is an odd number, the line is not read from the nth field. As described above, the difference in the average value of luminance due to light leakage between pixels adjacent in the vertical direction after the low-pass filter processing is controlled by controlling the readout order of the charges in the field is predetermined for each of the lines. A method for driving a solid-state imaging device, wherein the solid-state imaging device is in a range of . A reading step the image of one frame based on the charge photoelectrically converted, 2N + 1 (N is the integer) is divided into individual fields and reads the respective fields of charge at different timings for each divided field in the photoelectric conversion means,
A control step for controlling the reading order of the charges in the field ;
As a low-pass filter process performed on the image signal based on the electric charge read out in the read-out step, a filter step of performing smoothing between adjacent pixels in the vertical direction of the image ,
In the control step, the Kth field (K is an integer equal to or greater than 1) is the Kth field, and the line read as the first field on the output image is the first line. (N is an integer equal to or greater than 1 and n ≦ 2N + 1), but when n is 1 ≦ n ≦ 2N + 1 and is an odd number, the line is read as the nth field, and n is 1 ≦ n ≦ 2N + 1 In the case of an even number, the charge readout order of the field is controlled so that the line is read as the (2N + 2-n) field, and the vertical direction after the low-pass filter processing is performed. the difference between the average value of the brightness due to light leakage between adjacent pixels, the solid-state imaging device, characterized in that set to be within a predetermined range in each of the lines Dynamic way. A reading step the image of one frame based on the charge photoelectrically converted, 2N (N is the integer) is divided into individual fields and reads the respective fields of charge at different timings for each divided field in the photoelectric conversion means,
A control step for controlling the reading order of the charges in the field ;
As a low-pass filter process performed on the image signal based on the electric charge read out in the read-out step, a filter step of performing smoothing between adjacent pixels in the vertical direction of the image ,
In the control step, the Kth field (K is an integer equal to or greater than 1) is the Kth field, and the line read as the first field on the output image is the first line. (N is an integer of 1 or more and n ≦ 2N),
When n is 1 ≦ n ≦ N and is odd, or when n is N + 1 ≦ n ≦ 2N and is even, the line is read as the nth field,
When n is 1 ≦ n ≦ N and an even number, or when n is N + 1 ≦ n ≦ 2N and is an odd number, the line is read as the (2N + 1−n) field. The difference in the average value of luminance due to light leakage between adjacent pixels in the vertical direction after the low-pass filter processing is controlled by controlling the readout order of the electric charges in the field is within a predetermined range in each of the lines. A method of driving a solid-state imaging device, wherein The average value of luminance due to light leakage between adjacent pixels in the vertical direction after the low-pass filter processing is made to be the same in each of the lines. A method for driving the solid-state imaging device according to claim 1. Computer program characterized by executing the steps of the method for driving the solid-state imaging device according to the computer what Re one of claims 6-10.

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