JPH0767038A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To improve the degradation of picture quality caused by fixed pattern noise by storing a fixed pattern noise signal as line information and subtracting this fixed pattern noise signal from the output signal of the detected valid picture element part of a solid-state imaging device. CONSTITUTION:An image pickup output signal supplied from an A/D converting circuit into an input terminal 10a is supplied to a subtracting circuit 4 and a select circuit 13. At this select circuit 13, the image pickup output signal of a CCD imaging device is supplied to an integration circuit 2, in this image pickup output signal, the image pickup output signal corresponding to a vertical optical black picture element part 1V of the CCD imaging device is supplied to the integration circuit 2, and the image pickup output signal corresponding to a horizontal optical black picture element part 1H is supplied to an integration circuit 14. When the signal is integrated at the circuit 2, the fixed pattern noise signal sharply appears. The circuit 14 supplies the output to an optical black clamp circuit 15 as a clamp signal. At the subtracting circuit 4, this fixed pattern noise signal is subtracted for each line signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device using a solid-state image pickup device such as a CCD image pickup device.

[0002]

2. Description of the Related Art Generally, in a solid-state image pickup device using a CCD image pickup element, periodic clock noise caused by the system and white lines due to a defect of a vertical transfer register are problems in image quality. Was there.

In particular, this white line has a fixed vertical stripe even though the level of occurrence is very small, and therefore, there is a problem that the white line is very prone to rubbing. Since the white line of the vertical stripe is very small in level, it is buried in noise and difficult to detect, and it is very difficult to correct it.

Further, in a solid-state image pickup device using a CCD image pickup element, as a phenomenon peculiar to the CCD image pickup element, image quality deterioration due to a smear phenomenon which occurs when intense light is incident is also a problem.

Regarding the deterioration of the image quality due to the smear phenomenon, there is currently no effective means for suppressing it.
Although it depends on the improvement of the characteristics of the D image pickup device, it is becoming difficult to improve the characteristics of the CCD image pickup device recently due to the reduction of the unit pixel size and the increase in the sensitivity due to the miniaturization.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to improve deterioration of image quality due to white lines due to periodic clock noise and defects of vertical transfer registers, and deterioration of image quality due to smear phenomenon.

[0007]

In the solid-state image pickup device of the present invention, for example, as shown in the drawings, the output signal of the solid-state image pickup element 1 and the vertical optical black pixel portion 1V of the solid-state image pickup element 1 is output on a pixel-by-pixel basis. Integrating means 2 for integrating with, and this integrating means 2
And a subtracting means 4 for subtracting the signal stored in the storage means 3 from the output signal of the effective pixel portion 1a of the solid-state image pickup device 1. is there.

[0008]

According to the present invention, since the output signals of the optical black pixel portion in the vertical direction of the solid-state image pickup device 1 are integrated (added and averaged) in pixel units, random noise components are averaged and become zero, The fixed pattern noise signal can be detected, the fixed pattern noise signal is stored as line information, and the fixed pattern noise signal is subtracted from the output signal of the effective pixel portion 1a of the solid-state image pickup device 1 to obtain the fixed pattern noise signal. It is possible to improve certain white lines and smear.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the solid-state image pickup device of the present invention will be described below with reference to the drawings. FIG. 2 shows a solid-state image pickup device using a CCD image pickup device according to this example. 1 in FIG.
Indicates a CCD image pickup device in which a subject is imaged on an image pickup surface through an optical system. This CCD image pickup device 1 is as shown in FIG. 3, and its sensor area is vertical and horizontal to the effective pixel portion 1a which is an image pickup area. It is composed of optical black pixel portions 1V and 1H for determining the black reference of the direction. In this example, the optical black pixel portions 1V and 1H are 12 lines in the vertical direction above the effective pixel portion 1a. It is composed of an optical black pixel portion 1V and an optical black pixel portion 1H of 40 pixels horizontally on the right side of the effective pixel portion 1a.

The optical black pixel portions 1V and 1H have a structure in which a light-shielding film is provided on the sensor, and the optical black pixel portion 1V has a white line and smear on the effective pixel portion 1a.
The image output signal obtained from the optical black pixel portion 1V includes white lines and smear signals at the same level as the image output signal obtained from the effective pixel portion 1a.

In FIG. 2, reference numeral 5 denotes a timing generator. The timing generator 5 generates various signals at appropriate timings. Timing signals from the timing generator 5 are passed through a drive circuit 6 to the CCD. It is supplied to the image pickup device 1, and by this timing signal, signal charge is read from each pixel (sensor) in the CCD image pickup device 1 to the vertical transfer register, vertical transfer by the vertical transfer register, horizontal transfer by the horizontal transfer register, etc. Drive.

Reference numeral 7 is a reference signal oscillator, and the reference signal obtained by the reference signal oscillator 7 is supplied to the timing generator 5.

The image pickup output signal of the CCD image pickup device 1 is sampled and held (S / H) and automatic gain control (AGC).
It is supplied to an analog-digital (A / D) conversion circuit 9 via a circuit 8, and this A / D conversion circuit 9 supplies it to a fixed pattern noise removing circuit 10 as, for example, 10-bit digital data. An image pickup output signal of a digital signal from which fixed pattern noise is removed, which is obtained on the output side of the removing circuit 10, is supplied to the signal processing circuit 11,
Various kinds of signal processing are performed in the signal processing circuit 11 to obtain a luminance signal and a chroma signal, and a video output signal is obtained at the output terminal 12 of the signal processing circuit 11.

In this example, the fixed pattern noise removing circuit 10 is constructed as shown in FIG. Referring to FIG. 1, the imaging output signal from the A / D conversion circuit 9 supplied to the input terminal 10a is supplied to the subtraction circuit 4 and the imaging output signal is supplied to the selection circuit 13.

In the select circuit 13, 12 lines of image pickup output signals corresponding to the vertical optical black pixel portion 1V of the CCD image pickup device 1 among the image pickup output signals are supplied to the integrating circuit 2. Of this image pickup output signal, the image pickup output signal of 40 pixels corresponding to the horizontal optical black pixel portion 1H of the CCD image pickup element 1 is integrated into the integration circuit 14
To be supplied to.

In this case, the integrating circuit 2 uses the line memory 3 to integrate (addition average) 12 lines of the output signal from the vertical optical black pixel portion 1V in pixel units. A fixed pattern noise signal is stored in the line memory 3 as a signal for one line.

That is, when the integrating circuit 2 performs integration (additional averaging), random noise components are averaged to zero, and fixed level noise signals such as small-level white lines and smear signals buried in random noise become clear. appear.

The integrator circuit 14 is designed to obtain an accurate optical black reference. The image pickup output signal of the optical black pixel portion 1H in the horizontal direction of the CCD image pickup device 1 is extracted and integrated to generate random noise. An optical black reference signal from which the component has been removed is obtained, and the optical black reference signal obtained at the output side of the integration circuit 14 is used as a clamp signal to obtain an optical black clamp circuit 15.
Supply to.

The fixed pattern noise signal for one line stored in the line memory 3 is supplied to the subtraction circuit 4 as a subtraction signal through the optical black clamp circuit 15.
The subtraction circuit 4 subtracts the fixed pattern noise signal for one line for each line signal of the image pickup output signal.

An image pickup output signal from which the fixed pattern noise signal obtained at the output side of the subtraction circuit 4 is removed is supplied to the signal processing circuit 11. Others are configured similarly to the conventional solid-state imaging device.

The operation of the solid-state image pickup device of this embodiment will be described below with reference to FIGS. 4 and 5. 4 and 5 are represented in analog for convenience of explanation.

In the CCD image pickup device 1, when there is no defect in the vertical transfer register or the like, there is no white line or the like and there is no smear phenomenon, the input signal of the integrating circuit 2 is a random noise component signal as shown in FIG. The one-line signal stored in the memory 31 is a constant reference signal as shown in FIG. 4B, and therefore the output side of the optical black clamp circuit 15 is the optical signal obtained at the output side of the integrating circuit 14 as shown in FIG. 4C. A constant signal clamped by the dynamic black reference signal is obtained,
On the output side of the subtraction circuit 4, an image pickup output signal in which the optical black reference is defined is obtained, and on the output side of the signal processing circuit 11, a good video output signal is obtained.

Further, in the CCD image pickup device 1, when there is a white line in the vertical direction and a smear phenomenon due to a defect such as a vertical register as shown in FIG. 3, the input signal of the integrating circuit 2 is as shown in FIG.
As shown in A, it is a signal including a random noise signal, a smear signal, and a white line signal, and is stored in the line memory 3.
The line signal becomes a fixed pattern noise signal including a smear signal and a white line signal as shown in FIG. 5B.

Therefore, a fixed pattern noise signal clamped by the optical black reference signal obtained at the output side of the integrating circuit 14 is obtained at the output side of the optical black clamp circuit 15 as shown in FIG. On the output side, the fixed pattern noise signal as shown in FIG. 5E is removed from the image pickup output signal including the smear signal and the white line signal as shown in FIG. 5D supplied to this input side, and the optical black reference is determined. An image pickup output signal is obtained and supplied to the signal processing circuit 11.

Therefore, at the output side of the signal processing circuit 11, a video output signal in which smear and white lines, which are fixed pattern noises, are improved is obtained, and according to this example, periodic clock noises and defects in the vertical transfer register are caused. There is an advantage that the deterioration of the image quality due to the white line and the deterioration of the image quality due to the smear phenomenon can be improved.

In the above embodiment, the output signal of the vertical optical black pixel portion 1V of the solid-state image pickup device 1 for one field is integrated pixel by pixel and stored in the line memory 3 as a signal for one line. However, it may be integrated over a plurality of fields and stored in the line memory 3 as a signal for one line. In this case, the fixed pattern noise signal can be detected even better. Further, the present invention is not limited to the above-described embodiments, and needless to say, various other configurations can be adopted without departing from the gist of the present invention.

[0027]

According to the present invention, it is possible to improve deterioration of image quality due to fixed pattern noise generated in the vertical direction such as deterioration of image quality due to white lines due to periodic clock noise or defects of vertical transfer register, deterioration of image quality due to smear phenomenon, and the like. Have a profit

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a main part of a solid-state imaging device of the present invention.

FIG. 2 is a configuration diagram showing an embodiment of the solid-state imaging device of the present invention.

FIG. 3 is a diagram for explaining the present invention.

FIG. 4 is a diagram for explaining the present invention.

FIG. 5 is a diagram for explaining the present invention.

[Explanation of symbols]

 1 CCD Image Sensor 1a Effective Pixel Part 1H Horizontal Optical Black Pixel Part 1V Vertical Optical Black Pixel Part 2 Integration Circuit 3 Line Memory 4 Subtraction Circuit 10 Fixed Pattern Noise Removal Circuit 11 Signal Processing Circuit

Claims (2)

[Claims] 1. A solid-state image sensor, integrating means for integrating an output signal of an optical black pixel portion of the solid-state image sensor in a vertical direction, and an output signal of the integrating means for one line. And a subtraction unit for subtracting the signal stored in the storage unit from the output signal of the effective pixel portion of the solid-state image sensor. 2. The solid-state image pickup device according to claim 1, wherein said integration means integrates an output signal of an optical black pixel portion of said solid-state image pickup device in a vertical direction over a plurality of fields in units of one pixel. A solid-state image pickup device characterized by the above.