JP2003348453A - Image signal processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image signal processing apparatus for enhancing the immunity of a system to external disturbance and obtaining a stable and sharp image. <P>SOLUTION: In the image signal processing apparatus provided with: a correlate double sampling circuit 2 for applying correlate double sampling to a pixel signal outputted from a solid-state image pickup apparatus 1 having a valid pixel area 12 and shaded areas 13, 14 in a light receiving surface; an amplifier circuit 3 for amplifying the pixel signal outputted from the correlate double sampling circuit 2; and an offset correction circuit 6 for outputting an offset level for black level correction to the correlate double sampling circuit 2 and the amplifier circuit 3 on the basis of the pixel signal of the shade areas 13, 14 outputted from the amplifier circuit 3, the offset correction circuit 6 obtains a calculation reference level being the offset level for black level correction for each imaging period and approaches the calculation reference level to the calculation reference level by using a relaxation coefficient from the reference level before update being the offset level just before update. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing apparatus for obtaining a clear image from an image signal output from a solid-state image sensor such as a CCD image sensor or a CMOS image sensor.

[0002]

2. Description of the Related Art An image signal processing apparatus for digitally processing pixel signals sequentially obtained from a solid-state imaging device such as a CCD image sensor or a CMOS image sensor usually includes a correlated double sampling circuit, an amplifier circuit, an A / D conversion circuit, An offset correction circuit is provided.

A correlated double sampling circuit is a circuit for suppressing noise of a pixel signal. The correlated double sampling circuit converts a pixel signal composed of a pair of a pedestal level (generally a black level) and a signal level from a solid-state image sensor. Then, the pedestal level is clamped to the clamp potential, and the clamp is released during the scanning period in which the signal level is being output, and the change from the pedestal level to the signal level is sampled and held. In particular, a light-shielding region is provided on an array of solid-state imaging devices such as CCDs, and pixel signals in the light-shielding region are fixed at a black level.

[0004] The amplifying circuit is a circuit that amplifies a signal output from the correlated double sampling circuit at an amplification rate controlled according to externally applied data. The A / D conversion circuit is a circuit that samples an analog signal output from the amplifier circuit, performs quantization and encoding, and converts the analog signal into a digital signal.

Further, it is ideal that the black level, which is the pedestal level, does not have an offset. However, an offset voltage is generated in an actual solid-state image pickup device. It needs to be corrected. The offset correction circuit realizes this function, and usually adjusts the offset voltage of the amplifier circuit based on a signal digitized by the A / D conversion circuit.

However, in the conventional image signal processing apparatus as described above, there is a problem that the black level shift occurs when the amplification factor of the amplifier circuit is changed in order to ensure sufficient luminance or the like. .

When the light-shielding regions on the array of the solid-state imaging device are arranged at a plurality of locations, for example, at the upper end and the lower end of the array surface, a signal as a black level is provided between the light-shielding regions at different positions. There was also a problem that output varied.

Accordingly, the present applicant has filed a Japanese Patent Application No. 2000-39.
No. 3581 solves the above problem. This application is to solve the black level shift, when calculating the black level correction value by referring to the pixel signal output from the light-shielded region in the solid-state imaging device in the solid-state imaging device, the amplification factor to a plurality of values Described are an image signal processing apparatus and an image signal processing method for obtaining a correction value for obtaining a stable black level regardless of the amplification rate from a plurality of obtained light-shielded area outputs.

[0009]

However, the image signal processing apparatus and the image signal processing method according to the above-mentioned application provide a light shielding area during the driving period for one screen even when the amplification factor is not changed during the driving period. Because it is a method to correct the black level only from the output, when applied at the time of continuous shooting of multiple images,
There is a drawback that the system is susceptible to system disturbance and the black level tends to vary between successive screens.

Further, the black level correction method of the above application forms a feedback loop in which a black level correction value is obtained from a light-shielded area output, and the correction value is applied to a light-shielded area output of the next screen. There has been a problem that oscillation and ringing are likely to occur due to disturbances in the system or changes in set values.

[0011] The present invention has been made in view of the above,
During continuous imaging, the output of a light-shielded area in an arbitrary screen is processed, and when a black level correction value is obtained, this black level correction value is not immediately applied to the output of the succeeding effective pixel area. Image signal processing that makes it possible to increase the resistance to disturbances and adjust the convergence speed to the target value by adopting a method of approaching the black level correction value to be updated from the black level correction value to the update value with the relaxation coefficient γ. The aim is to obtain a device.

[0012]

In order to achieve the above object, an image signal processing apparatus according to the present invention relates to an image signal processing apparatus which correlates pixel signals output from a solid-state imaging device having an effective pixel area and a light shielding area in a light receiving surface. A correlated double sampling circuit for performing double sampling, an amplifying circuit for amplifying a pixel signal output from the correlated double sampling circuit, and the correlation based on the pixel signal in the light-shielded region output from the amplifying circuit. In an image signal processing apparatus including a double sampling circuit and an offset correction circuit that outputs an offset potential for black level correction to the amplification circuit, the offset correction circuit includes an offset potential for black level correction for each imaging cycle. Is calculated, and the calculated reference potential is calculated from the pre-update reference potential which is the offset potential immediately before the update. Characterized in that close with a relaxation factor to calculate the reference potential.

According to the present invention, the offset correction circuit obtains a calculated reference potential, which is an offset potential for black level correction, for each imaging cycle, and determines this calculated reference potential as the offset potential immediately before the update, which is the offset potential before the update. The reference potential can be made closer to the calculated reference potential with a relaxation coefficient.

[0014] The image signal processing apparatus according to the next invention comprises:
In the invention described above, the offset correction circuit calculates a relaxation coefficient γ as a difference between the calculated reference potential and the reference potential before update.
A value obtained by multiplying the reference potential by an arbitrary real number between 0 and 1 is corrected by an updated reference potential added to the pre-update reference potential.

According to the present invention, the offset correction circuit determines the difference between the calculated reference potential and the pre-update reference potential by the relaxation coefficient γ.
(A real number between 0 and 1) can be corrected by the updated reference potential obtained by adding the value multiplied to the pre-update reference potential.

[0016] The image signal processing apparatus according to the next invention comprises:
In the above invention, the offset correction circuit changes a relaxation coefficient to be multiplied by a value of an amplification factor.

According to the present invention, the offset correction circuit can change the relaxation coefficient to be multiplied by the amplification factor.

An image signal processing apparatus according to the next invention has
In the above invention, the offset correction circuit dynamically changes the relaxation coefficient by using a predetermined change in a set value of the circuit or an external condition as a trigger.

According to the present invention, the offset correction circuit can dynamically change the relaxation coefficient triggered by a predetermined change in the set value of the circuit or an external condition.

An image signal processing apparatus according to the next invention is:
In the above invention, the offset correction circuit uses a predetermined change in the amplification factor as a trigger.

According to the present invention, the offset correction circuit can be triggered by a predetermined change in the amplification factor.

An image signal processing device according to the next invention is characterized in that:
In the above invention, the offset correction circuit is triggered by a predetermined change in the accumulation time of the pixel.

According to the present invention, the offset correction circuit can be triggered by a predetermined change in the pixel accumulation time.

An image signal processing apparatus according to the next invention has
In the above invention, the offset correction circuit includes an output of a first light-shielded area scanned and output before scanning of the effective pixel area and a second light-shielded area scanned and output after scanning of the effective pixel area. An operation of referring to both the output of the first light-shielded region and the output of the second light-shielded region, and an operation of referencing only the output of the first light-shielded region when calculating the updated reference potential from the output Is dynamically switched.

According to this invention, the offset correction circuit scans and outputs the first light-shielded area before scanning the effective pixel area and the second light-shielded area that is scanned and output after scanning the effective pixel area. When calculating the updated reference potential from the output of the area, the operation of referring to both the output of the first light-shielded area and the output of the second light-shielded area, and the operation of referring only to the output of the first light-shielded area The operation can be dynamically switched.

An image signal processing apparatus according to the next invention has
In the above invention, the offset correction circuit dynamically switches an operation of referring to a predetermined change in a set value of the circuit or an external condition as a trigger.

According to the present invention, the offset correction circuit can dynamically switch the operation of referring to a predetermined change in the set value of the circuit or an external condition as a trigger.

The image signal processing device according to the next invention is
In the above invention, when the amplification factor is high, the calculated reference potential is corrected from a calculated value to a predetermined white level.

According to the present invention, when the amplification factor is high, the calculated reference potential can be corrected from the calculated value toward a predetermined white level.

An image signal processing device according to the next invention is characterized in that:
In the above invention, when the absolute value of the difference between the calculated reference potential and the pre-update reference potential exceeds a predetermined value, the change in the update potential is suppressed to a predetermined value.

According to the present invention, when the absolute value of the difference between the calculated reference potential and the pre-update reference potential exceeds a predetermined value, the change in the update potential can be suppressed to a predetermined value.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an image signal processing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a block diagram showing a schematic configuration of the image signal processing device according to the first embodiment of the present invention. The image signal processing device shown in FIG. 1 includes a solid-state imaging device 1, a correlated double sampling circuit 2, an amplification circuit 3,
A / D conversion circuit 4, an amplification factor setting register 5, and an offset correction circuit 6 are provided.

In FIG. 1, a solid-state imaging device 1 includes a light receiving section (not shown) in which elements for converting an optical signal into an electric signal are arranged on an array, and sequentially scans and outputs signals obtained from the respective elements at a predetermined timing. (Not shown). The elements arranged on this array include a light-shielding region 13, an effective pixel region 12, and a light that is scanned after the effective pixel region 12, which are shielded by a light-impermeable filter scanned before the effective pixel region. It is arranged in the order of the light-shielding area 14 which is shielded by a filter. The solid-state imaging device 1 scans the light-shielding region 13,
The output of the pixel signal is repeated with the scanning of 2 and the scanning of the light shielding area 14 as one cycle, and the obtained pixel signal is output to the correlated double sampling circuit 2 at the subsequent stage. This pixel signal passes through a correlated double sampling circuit 2 and an amplification circuit 3 at the subsequent stage,
A digital output is obtained by the D conversion circuit 4. Note that the pixel signals output from the light-shielding regions 13 and 14 represent the black level of the solid-state imaging device 1.

In FIG. 1, the correlated double sampling circuit 2 sequentially generates signal voltages based on pixel signals sequentially obtained from the solid-state imaging device 1 and outputs the signal voltages to the subsequent amplification circuit 3 as pixel signals. The black level of the pixel signal is adjusted by the input reference potential 21. The amplification circuit 3 amplifies the input signal at the amplification factor set by the amplification factor setting register 5 and outputs the signal to the A / D conversion circuit 4 at the subsequent stage. The black level of this output signal is adjusted by the input reference potential 31. The A / D conversion circuit 4 outputs the input analog signal as a digital output.

In FIG. 1, the amplification factor setting register 5
The amplification factor is switched to a predetermined amplification factor during the scanning of the light-shielded regions 13 and 14 of the solid-state imaging device 1, and the amplification factor is set in the amplification circuit 3 at a timing specified by a control device (not shown), and the amplification factor is offset-corrected. The circuit 6 is notified.

The offset correction circuit 6 is based on the digital output of the A / D conversion circuit 4 comprising outputs at a plurality of amplification factors, and the black level of this digital output is adjusted to a desired value (usually a digital output) regardless of the amplification factor. Of the reference potentials 21 and 31 are calculated. Reference potentials 21 and 31 for adjusting these black levels to ideal values
Are calculated as a calculated reference potential V ₂₁ (ideal) and a calculated reference potential V ₃₁ (ideal), respectively.

In the aforementioned application, the reference potentials 21 and 31
From the calculated reference potentials V ₂₁ (ideal) and V
₃₁ (ideal), but in the first embodiment,
The reference potentials 21 and 31 are updated based on the following update formula. Here, the pre-update reference potential 21 of the pre-update reference electric potential V ₂₁ (old), before updating the reference potential 31 of the pre-update reference electric potential V _{3 1} (old), is actually outputted to the correlation double sampling circuit 2 The reference potential 21 is updated to the updated reference potential V ₂₁ (new), and the reference potential 31 actually output to the amplifier circuit 3 is changed to the updated reference potential V _21.
31 (new), the update formula is

V ₂₁ (new) = V ₂₁ (old) + [V ₂₁ (ideal) −V ₂₁ (old)] × γ (Equation 1) V ₃₁ (new) = V ₃₁ (old) + [ V ₃₁ (ideal) −V ₃₁ (old)] × γ (Equation 2) Here, γ is a relaxation coefficient and takes an arbitrary real value between 0 and 1.

The timing at which this updating formula is applied is based on the pixel signal outputs obtained from the light-shielded regions 13 and 14, and after the updated values of the reference potentials 21 and 31 are calculated by the formulas 1 and 2, the effective timing is calculated. This is applied from the time when the pixel signal of the pixel region 12 is output.

The relaxation coefficient γ takes a value close to “1” (for example, 0.8) during a period of several screens immediately after the change of the amplification factor, and changes from “1” during other periods without change. It is controlled by a control device (not shown) so as to take a small value (for example, 0.1).

That is, since γ is updated by the change of the amplification factor as a trigger immediately after the change of the amplification factor with respect to the update value calculated by the offset correction circuit 6, a clear image with uniform levels can be obtained more quickly. Can be. On the other hand, during the period when the amplification factor is not changed, the reference potential follows the updated value slowly, so that even if there is disturbance to the circuit or the updated value fluctuates due to non-ideality, the black level does not fluctuate. And a stable image output can be obtained.

Further, since the light-shielding regions 13 and 14 are provided before and after the effective pixel region 12 and the correction value of the black level is calculated by referring to both of them, for example, the output of the solid-state image pickup device 1 is changed to a gradation for manufacturing reasons. , The black level can be corrected to a substantially intermediate value between the light-shielding regions 13 and 14.

In the first embodiment, an example in which a change in the amplification factor is used as a trigger has been described. However, other changes in conditions that lead to a change in black level, for example, a pixel accumulation time or temperature, may be used as a trigger. It is equally possible to do so.

FIG. 2 is an explanatory diagram showing an example of the configuration of the light-shielding region of the solid-state imaging device. In the first embodiment, the light shielding region 1
3 scan, effective pixel area 12 scan and light-shield area 14
Is a method of calculating the correction value of the black level with one scan as one cycle. Therefore, even if there is a light shielding area at the beginning and end of each scanning line as shown in FIG. Techniques can be applied.

Immediately after the change of the circuit set value such as the image accumulation time, the calculated reference potential V ₂₁ (ideal) of the equation 1 and the equation 2
The image signal processing device that uses the calculated reference potential V ₃₁ (ideal) as an update value as it is and the image signal processing device that does not update the reference potential at all except immediately after a change in the circuit setting value also have a relaxation coefficient γ
Are “1” or “0”, respectively, as an example of the first embodiment.

Further, by setting the relaxation coefficient γ to a function corresponding to the amplification factor instead of a constant value, the frequency characteristics of the feedback loop can be improved, and a stable response can be obtained at all possible setting values of the amplification factor. It is also possible to optimize as follows.

As described above, according to the first embodiment, γ is updated with respect to the update value calculated by the offset correction circuit immediately after the amplification factor is changed, using the change in the amplification factor as a trigger.
During the period when the amplification rate is not changed, the reference potential is made to follow the updated value slowly, so that a clear image with a uniform level can be obtained more quickly, and the circuit is updated by disturbance or non-ideality of the circuit. Even if the value fluctuates, a stable image in which the black level does not flutter can be obtained.

Embodiment 2 The configuration of the image signal processing device according to the second embodiment is the same as that of the image signal processing device according to the first embodiment shown in FIG. Also, the operation will be described focusing on parts different from the first embodiment.

Changing the circuit set values such as the image storage time
For example, the scanning is usually performed at the boundary of the operation cycle of the solid-state imaging device 1, for example, between the time when the scanning of the light shielding area 14 is completed and the time when the scanning of the next light shielding area 13 is started. In the second embodiment, when the update values of the reference potentials 21 and 31 are calculated, while the imaging is continued at a constant circuit set value,
Although both pixel signal outputs obtained from the light-shielded regions 13 and 14 are referred to, immediately after the circuit setting value is changed, only the output from the light-shielded region 13 scanned after the change is referred to.

As described above, according to the image signal processing apparatus of the second embodiment, the output of the light-shielded area 13 is used instead of the output of the light-shielded area 14 when the change of the apparatus setting value is used as a trigger. , The shaded area output obtained before switching the set value can be excluded from the reference data of the correction value calculation,
The black level can be corrected without being affected by the state before the change.

Embodiment 3 FIG. The configuration of the image signal processing device according to the third embodiment is the same as that of the image signal processing device according to the first embodiment shown in FIG. Also, the operation will be described focusing on parts different from the first embodiment.

FIG. 3 is a graph showing an example of the relationship between the amplification factor and the black level target value in the third embodiment. The third embodiment is the same as the first embodiment in that the updated values of the reference potentials 21 and 31 are calculated based on the image signal outputs obtained from the light-shielded regions 13 and 14, but the set value of the amplification factor is If it is larger than a certain level, the target value of the black level is calculated to be whiter than usual.

In the first embodiment, the minimum value of the A / D output range is set as the target value of the black level output irrespective of the amplification factor as in the case of 81. In the third embodiment, the black level is output in the range where the amplification factor is high. It is intended to increase the target value.

As described above, according to the image signal processing apparatus of the third embodiment, when the set value of the amplification factor is larger than a certain value, the black level is set to be whiter than usual.
It is possible to prevent underexposure which is likely to occur at a high amplification rate, and improve image quality.

Embodiment 4 . The image signal processing apparatus according to the fourth embodiment has the same configuration as the image signal processing apparatus according to the first embodiment shown in FIG. Also, the operation will be described focusing on parts different from the first embodiment.

The calculation of the updated reference potentials V ₂₁ (new) and V ₃₁ (new), which are the updated values of the reference potentials 21 and 31, based on the pixel signal outputs obtained from the light-shielded regions 13 and 14 is described in the embodiment. 1, but the calculated reference potential V ₂₁ (ide
al) and the absolute value of the difference between the reference potential V ₂₁ (old) before update and the difference between the calculated reference potential V ₃₁ (ideal) and the reference potential V ₃₁ (old) before update from certain values dV _21max and dV _31max . If the value is larger, only the fixed value is updated.

That is, the updated reference potential V ₂₁ (new) actually output to the correlated double sampling circuit 2 is calculated by the following equation.

V ₂₁ (new) = V ₂₁ (old) + [V ₂₁ (ideal) −V ₂₁ (old)] × γ (Equation 3) (ABS ((V ₂₁ (ideal) −V ₂₁ ( old)) × γ) <dV _21max ) V ₂₁ (new) = V ₂₁ ± dV _21max (Equation 4) (ABS ((V ₂₁ (ideal) −V ₂₁ (old)) × γ)> dV _21max )

Similarly, an updated reference potential V ₃₁ (new) actually output to the amplifier circuit 3 is calculated by the following equation.

V ₃₁ (new) = V ₃₁ (old) + [V ₃₁ (ideal) −V ₃₁ (old)] × γ (Equation 5) (ABS ([V ₃₁ (ideal) −V ₃₁ ( old)] × γ) <dV _31max ) V ₃₁ (new) = V ₃₁ ± dV _31max (Equation 6) (ABS ([V ₃₁ (ideal) −V ₃₁ (old)] × γ)> dV _31max )

By setting the reference potential to the correlated double sampling circuit 2 and the amplifying circuit 3 based on the conditional expressions of Expressions 3 to 6, a sudden change in the offset correction value can be made regardless of the circuit setting conditions. Can be avoided.

As described above, according to the image signal processing device of the fourth embodiment, when the updated value of the reference potential exceeds a certain value, the reference value is not changed beyond the certain value, so that it is likely to occur when the correction is made abruptly. Screen flicker can be prevented.

Embodiment 5 FIG. 4 is a block diagram illustrating a schematic configuration of the image signal processing device according to the fifth embodiment. This image signal processing device is the same as that of the first embodiment up to the portion that outputs the output signal of the solid-state imaging device 1 to the correlated double sampling circuit 2 and the amplification circuit 3, but does not perform A / D conversion thereafter. And outputs a signal to the offset correction circuit 6 while keeping the analog value. The offset correction circuit 6 internally performs an analog operation to calculate updated values of the reference potentials 21 and 31. The image signal processing apparatus according to the fifth embodiment is different from the image signal processing apparatus according to the first embodiment except that the digital signal does not pass on the way.
Performs exactly the same operation as.

As described above, according to the image signal processing apparatus of the fifth embodiment, even if the A / D conversion circuit is not provided, the amplification factor is changed immediately after the amplification factor is changed with respect to the updated value calculated by the offset correction circuit. Triggered by the change of γ, the period during which the amplification factor is not changed, the reference potential is made to follow the updated value slowly, so that a clear image with a uniform level can be obtained more quickly. Even if the update value fluctuates due to disturbance to the circuit or non-ideality, a stable image in which the black level does not fluctuate can be obtained.

Embodiment 6 FIG. FIG. 5 is a block diagram illustrating a schematic configuration of the image signal processing device according to the sixth embodiment. This image signal processing device is the same as that of the first embodiment up to the portion for sending the output signal of the solid-state imaging device 1 to the correlated double sampling circuit 2, but thereafter, the pixel signal is input range variable in which the input range is variable. Sent to the A / D conversion circuit 71,
Digital output.

The input range of the input range variable A / D conversion circuit 71 is given by an amplification factor A / D range conversion circuit 72. This input range switching is performed, for example, such that the smaller the amount of light applied to the cell, the smaller the pixel signal output, and the larger the amount of light applied to the cell, the larger the pixel signal output. At this time, by switching the input range according to the pixel signal output, an optimal dynamic range can be secured without depending on the pixel signal output.

The other operation is that the offset correction circuit 6 supplies the reference potential 31 to the amplification circuit 3 but the amplification factor A
Only the difference is that the reference potential 31 is applied to the / D range conversion circuit 72, and the rest can be considered exactly as in the first embodiment.

As described above, according to the image signal processing apparatus of the sixth embodiment, the range variable A / D
Even with a system that uses a conversion circuit, it is possible to obtain a stable image that does not fluctuate at the black level due to disturbances and non-idealities of the circuit, and to secure the optimal dynamic range without depending on the pixel signal output. it can.

FIG. 6 is a block diagram showing a schematic configuration of a modification of the image signal processing device of FIG. FIG. 5 shows a correlated double sampling circuit 2, an input range variable A / D conversion circuit 7,
1 is provided in the image signal processing apparatus, but as shown in FIG. 6, a correlated double sampling circuit array 92 corresponding to each scanning row, a range variable A /
It can be replaced with a form including the D conversion circuit array 93.

[0071]

As described above, according to the present invention, the offset correction circuit obtains the calculated reference potential, which is the offset potential for black level correction, for each imaging cycle.
Since the calculated reference potential is made closer to the calculated reference potential with a relaxation coefficient from the pre-update reference potential, which is the offset potential immediately before the update, even if the amplification factor of the amplifier circuit is changed to an arbitrary value, the black level is not changed. Variations can be prevented, and a clearer and more stable image can be obtained.

According to the next invention, the offset correction circuit calculates the relaxation coefficient γ as the difference between the calculated reference potential and the reference potential before update.
(An arbitrary real number between 0 and 1) is corrected by the updated reference potential added to the pre-update reference potential. Therefore, even if the amplification factor of the amplifier circuit is changed to an arbitrary value, It is possible to prevent the fluctuation of the black level and to obtain a clearer and more stable image.

According to the next invention, since the offset correction circuit changes the relaxation coefficient to be multiplied by the value of the amplification factor, the offset correction circuit optimizes the frequency characteristic of the feedback path for the correction of the black level that changes with the amplification factor. The effect that it can be made is produced.

According to the next invention, the offset correction circuit dynamically changes the relaxation coefficient by using a predetermined change in the set value of the circuit or the external condition as a trigger. When the offset readjustment is completed and the condition is not changed at the same time, it is possible to obtain a stable continuous imaging result in which the black level does not fluctuate.

According to the next invention, since the offset correction circuit uses a predetermined change in the amplification factor as a trigger, a stable continuous imaging result can be obtained even when the amplification factor is dynamically changed. It has the effect of being able to do so.

According to the next invention, the offset correction circuit uses a predetermined change in the accumulation time of the pixel as a trigger, so that even when the accumulation time is dynamically changed, the black level is not changed. There is an effect that it is possible to obtain a stable continuous imaging result that does not flutter.

According to the next invention, the offset correction circuit scans and outputs the first light-shielded area before scanning the effective pixel area and the second output which is scanned and output after scanning the effective pixel area. When calculating the update reference potential from the output of the light-shielded area, the operation of referring to both the output of the first light-shielded area and the output of the second light-shielded area, and the operation of referring only to the output of the first light-shielded area If the output of either of the two light-shielded areas becomes inappropriate as the reference black level of the succeeding effective pixel area for any reason, the calculation is temporarily performed. By switching the method, there is an effect that an operation of calculating a correction value from an inappropriate output can be avoided.

According to the next invention, the offset correction circuit dynamically switches the operation of referring to the set value of the circuit or a predetermined change in the external condition as a trigger. There is an effect that the obtained light-shielded area output can be excluded from the reference data for the correction value calculation.

According to the next invention, when the amplification factor is high, the calculated reference potential is corrected from the calculated value toward a predetermined white level. This has the effect of avoiding crushing and improving image quality.

According to the next invention, when the absolute value of the difference between the calculated reference potential and the pre-update reference potential exceeds a predetermined value, the change in the updated potential is suppressed to a predetermined value. This has the effect of preventing the oscillation and the flickering of the screen, which often occur, from occurring.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an image signal processing device according to a first embodiment of the present invention;

FIG. 2 is an explanatory diagram illustrating an example of a configuration of a light shielding area of the solid-state imaging device.

FIG. 3 is a graph showing an example of a relationship between an amplification factor and a black level target value according to the third embodiment.

FIG. 4 is a block diagram illustrating a schematic configuration of an image signal processing device according to a fifth embodiment.

FIG. 5 is a block diagram illustrating a schematic configuration of an image signal processing device according to a sixth embodiment.

FIG. 6 is a block diagram illustrating a schematic configuration of a modification of the image signal processing device of FIG. 5;

[Explanation of symbols]

1 solid-state imaging device, 2 correlated double sampling circuit, 3
Amplifying circuit, 4 A / D conversion circuit, 5 gain setting register, 6 offset correction circuit, 12 effective pixel area,
13, 14 shading area, 21, 31 reference potential, 71
Input range variable A / D conversion circuit, 72 amplification rate A / D range conversion circuit, 92 correlated double sampling circuit array, 93 range variable A / D conversion circuit array.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kenichi Shimoson             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo 3             Rishi Electric Co., Ltd. F term (reference) 5C024 CX06 CX31 GZ39 GZ40 HX13                       HX18 HX23 HX28 HX29 HX30

Claims (10)

[Claims] 1. A correlated double sampling circuit for performing correlated double sampling on a pixel signal output from a solid-state imaging device having an effective pixel area and a light shielding area in a light receiving surface, and a signal output from the correlated double sampling circuit. Amplifying circuit for amplifying a pixel signal to be output, and an offset for outputting an offset potential for black level correction to the correlated double sampling circuit and the amplifying circuit based on the pixel signal in the light-shielded region output from the amplifying circuit. In an image signal processing device including a correction circuit, the offset correction circuit determines a calculation reference potential that is an offset potential for black level correction for each imaging cycle,
An image signal processing apparatus, wherein the calculated reference potential is made closer to the calculated reference potential with a relaxation coefficient from a pre-update reference potential which is an offset potential immediately before the update. 2. The offset correction circuit according to claim 1, wherein a difference between the calculated reference potential and the pre-update reference potential is a relaxation coefficient γ (0 to 0).
2. The image signal processing device according to claim 1, wherein a value obtained by multiplying the reference potential by an arbitrary real number between 1 and 2 is corrected by an updated reference potential added to the pre-update reference potential. 3. The image signal processing apparatus according to claim 2, wherein the offset correction circuit changes a relaxation coefficient to be multiplied by a value of an amplification factor. 4. The image signal processing apparatus according to claim 2, wherein the offset correction circuit dynamically changes the relaxation coefficient by using a predetermined change in a set value of the circuit or an external condition as a trigger. 5. The image signal processing apparatus according to claim 4, wherein the offset correction circuit uses a predetermined change in an amplification factor as a trigger. 6. The image signal processing apparatus according to claim 4, wherein the offset correction circuit uses a predetermined change in a pixel accumulation time as a trigger. 7. An offset correction circuit comprising: an output of a first light-shielded area scanned and output before scanning of an effective pixel area; and an output of a second light-shielded area scanned and output after scanning of the effective pixel area. An operation of referring to both the output of the first light-shielded region and the output of the second light-shielded region, and an operation of referencing only the output of the first light-shielded region when calculating the updated reference potential from the output The image signal processing apparatus according to claim 1, wherein the image signal is dynamically switched. 8. The image signal processing apparatus according to claim 7, wherein the offset correction circuit dynamically switches an operation of referring to a predetermined change in a set value of the circuit or an external condition as a trigger. 9. The apparatus according to claim 1, wherein the offset correction circuit corrects the calculated reference potential from a calculated value toward a predetermined white level when the amplification factor is high. 5. The image signal processing device according to 1. 10. The method according to claim 1, wherein the offset correction circuit suppresses a change in the update potential to a predetermined value when an absolute value of a difference between the calculated reference potential and the pre-update reference potential exceeds a predetermined value. Item 10. The image signal processing device according to any one of Items 1 to 9.