JP2003174594A - Solid-state image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state image pickup device having a stable black level clamp by solving the problem that charges overflow to a horizontal optical black part and a black level becomes unstable in photographing an object of strong light by using the solid-state image pickup device. <P>SOLUTION: A first optical black part h1 and a second optical black part h2 are provided on an end part in a horizontal direction of an image pickup area d of a solid-state image pickup element 1. When the black level fluctuates, a clamp pulse A and a clamp pulse B are switched and supplied to a clamp circuit 3 on the basis of detected signals C by a black level fluctuation detection means 9 and thus stable clamp characteristics are obtained. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device in which an optical black portion is provided, and a signal obtained when the optical black portion is scanned is obtained. The present invention relates to a solid-state imaging device whose level is set to a reference black level. 2. Description of the Related Art A solid-state image pickup device (C
CD (Charge Coupled Device))
Are provided in the horizontal and vertical directions, respectively, with optical black pixels that are optically shielded during an optical black period. The video signal level of the optical black portion is clamped by a clamp circuit, and the level is set to a black level, so that a black subject can be captured in black. As a simple method of clamping, a method using one type of horizontal clamping pulse is generally used. Hereinafter, a conventional solid-state imaging device will be described. FIG. 4 is a block diagram illustrating a conventional solid-state imaging device. In FIG. 4, 1 is a solid-state imaging device, 2 is a sample-hold circuit, 3 is a clamp circuit as a clamp means, 4 is an analog-digital converter circuit (hereinafter, referred to as an AD converter circuit) as an AD converter, and 5 is a digital circuit. A signal processing circuit, 6 is a synchronization signal generating circuit, A is a clamp pulse, a is an analog signal, and b is a digital signal. FIG. 3 is a schematic diagram showing a configuration example of the solid-state imaging device 1. In FIG. 3, d is an imaging area, h1 is a horizontal optical black portion, h2 is a horizontal optical black portion, v1 is a vertical optical black portion, v2 is a vertical optical black portion, and e is an example of a high-luminance subject. The signals of the solid-state imaging device 1 are read in the horizontal direction (arrow X direction), sequentially read in the vertical direction (arrow Y direction), and the signals of all pixels are output. The clamp valve A is a clamp valve for clamping the horizontal optical black portion h1. The operation of the conventional solid-state imaging device configured as described above will be described below. The solid-state imaging device 1 photoelectrically converts light from a subject and supplies an output to a sample-and-hold circuit 2. The sample hold circuit 2 converts an output signal supplied from the solid-state imaging device 1 into a continuous signal. The clamp circuit 3 determines a reference black level based on the continuous signal supplied from the sample hold circuit 2 and the clamp pulse A supplied from the synchronizing signal generation circuit 6, and outputs an analog signal a. The AD conversion circuit AD-converts the analog signal a supplied from the clamp circuit 3 and outputs a 10-bit digital signal b. Further, the digital signal processing circuit 5 performs gain control, gamma processing, white balance processing, compression / expansion processing, and the like on the digital signal b, and outputs it as a video signal.
In the synchronizing signal generation circuit 6, signals such as a solid-state image sensor driving pulse, a sample hold pulse, a clamp pulse, an AD conversion circuit driving pulse, and a composite synchronizing signal pulse are generated, and the solid-state image sensor driving pulse is supplied to the solid-state image sensor 1. The sample / hold pulse is supplied to the sample / hold circuit 2, the clamp pulse A is supplied to the clamp circuit 3, the AD conversion circuit driving pulse is supplied to the AD conversion circuit 4, and the composite synchronizing signal pulse is supplied to the digital signal processing circuit 5.
Supplied to [0008] However, in the above-described conventional configuration, as shown in FIG. 3, the position of the end of the imaging region d of the solid-state imaging device 1 is relatively close to the horizontal optical black portion h1. When a high-luminance subject e (e.g., the sun, an electric light, etc.) that emits light is present, light from the high-luminance subject e leaks to the periphery, and the horizontal optical black portion h1
Part of the light enters, and the light is photoelectrically converted. In such a case, the level of the video signal when scanning the horizontal optical black portion h1 is shifted from the level corresponding to black, but the above-described clamp pulse is configured to clamp the horizontal optical black portion h1. Therefore, the shifted level is used as a reference. And, when the standards are out of order, the image becomes extremely unsightly. Further, strong light from the high-luminance subject e may enter not only the horizontal optical black portions h1 and h2 but also the vertical optical black portions v1 and v2, and both the horizontal and vertical optical black portions. There is also the possibility of entering. That is, when only one type of horizontal optical black portion is clamped, the black level may become unstable when capturing a high-luminance subject such as the sun. Conversely, not only the horizontal optical black portion but also the vertical optical black portion may be unstable. When the black portion is also clamped, there is a problem that the black level may fluctuate due to the influence of vertical smear when capturing a high-luminance subject. The present invention solves the above-mentioned conventional problems. When photographing a normal subject, the horizontal optical black portion h1 is clamped, and the black level of the horizontal optical black portion h1 is increased by a high-luminance subject with strong light. In the case of a fluctuation, the horizontal optical black portion h2, which is arranged in the opposite direction to the horizontal optical black portion h1 and is not affected by the high-luminance subject, is switched to be clamped. Regardless, sometimes, a solid-state imaging device with a stable black level can be provided. In order to achieve this object, a solid-state image pickup device according to the present invention comprises a first optical black portion optically shielded from both ends in a horizontal direction of an image pickup area and a second optical black portion. A solid-state imaging device having two optical black portions; a clamp unit for clamping a black level of an output signal of the solid-state imaging device; an analog-digital conversion unit for performing analog-to-digital conversion of the output signal clamped by the clamp unit; When the black level of the signal fluctuates, the black level fluctuation detecting means for detecting that the black level has fluctuated using the digital signal output from the analog-digital conversion means to generate a black level fluctuation detecting signal, and the clamp means A clamp pulse for generating a first clamp pulse and a second clamp pulse for clamping a black level of an output signal Generating means, and switching means for switching between the first clamp pulse and the second clamp pulse based on the black level fluctuation detection signal and supplying the same to the clamp means, wherein the first clamp pulse is applied only to the first optical black portion. And the second clamp pulse is a pulse for clamping only the second optical black portion. With this configuration, it is possible to always provide a solid-state imaging device having a stable black level irrespective of normal shooting or high-brightness shooting. The first aspect of the present invention is directed to a first optical black portion and a second optical black portion which are optically shielded at both ends in the horizontal direction of an image pickup area. A solid-state imaging device, a clamp unit for clamping a black level of an output signal of the solid-state imaging device, an analog-digital conversion unit for analog-to-digital conversion of the output signal clamped by the clamp unit, and a black level of the output signal. The black level fluctuation detecting means for detecting the fluctuation of the black level using the digital signal output from the analog-to-digital conversion means to generate a black level fluctuation detection signal when the fluctuation occurs, and the clamp means for controlling the black level of the output signal. Pulse generating means for generating a first clamp pulse and a second clamp pulse for clamping Switching means for switching the first and second clamp pulses based on the black level fluctuation detection signal and supplying the same to the clamp means, wherein the first clamp pulse is a pulse for clamping only the first optical black portion. The second clamp pulse is a pulse for clamping only the second optical black portion, and clamps the first horizontal optical black portion when photographing a normal subject. Then, when the black level of the first horizontal optical black portion is changed by a high-luminance subject of strong light,
By switching to clamp the second horizontal optical black portion which is not affected by the high-luminance subject because it is arranged in the opposite direction to the first horizontal optical black portion, it is possible to control the normal and high-luminance shooting. In addition, it has an effect that an image with a stable black level can always be sold. FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a block diagram showing the configuration of a solid-state imaging device according to Embodiment 1 of the present invention. In FIG. Is omitted. In FIG. 1, reference numeral 7 denotes a synchronizing signal generating circuit which is a clamp pulse generating means, 8 denotes a switching circuit which is a switching means, 9 denotes a black level fluctuation detecting circuit which is a black level fluctuation detecting means, B denotes a clamp pulse, and C denotes a detection signal. It is. The synchronizing signal generating circuit 7 is obtained by adding a function of generating a clamp pulse B to the synchronizing signal generating circuit 6 of the prior art. The switching circuit 8 selects and outputs the clamp pulse A and the clamp pulse B based on the detection signal C, and supplies the same to the clamp circuit 3. When the black level fluctuation detecting circuit 9 detects the fluctuation of the black level from the digital signal b,
The detection signal C is output. The clamp valve B is a clamp valve for clamping the horizontal optical black portion h2. The operation of the solid-state imaging device configured as described above will be described. The solid-state imaging device 1 supplies an output obtained by photoelectrically converting light from a subject to a sample-and-hold circuit 2, and the sample-and-hold circuit 2 converts the output signal supplied from the solid-state imaging device 1 into a continuous signal. The clamp circuit 3 determines a reference black level based on the signal supplied from the sample hold circuit 2 and the clamp pulse supplied from the switching circuit 8, and outputs an analog signal a. The AD conversion circuit 4 AD-converts the analog signal a supplied from the clamp circuit 3 and outputs a 10-bit digital signal b. Further, the digital signal processing circuit 5 performs gain control, gamma processing, white balance processing, compression / expansion processing, and the like on the digital signal b, and outputs it as a video signal. In the synchronization signal generation circuit 7, signals such as a solid-state imaging device driving pulse, a sample hold pulse, a clamp pulse A, a clamp pulse B, an AD conversion circuit driving pulse, and a composite synchronization signal pulse are generated. The sample / hold pulse is supplied to the image pickup device 1, the sample / hold pulse is supplied to the sample / hold circuit 2, the clamp pulse A and the clamp pulse B are supplied to the switching circuit 8, the AD conversion circuit drive pulse is supplied to the AD conversion circuit 4, and The signal pulse is supplied to the digital signal processing circuit 5. The black level fluctuation detection circuit 9 reads information of the horizontal optical black portion h1 of the digital signal b output from the AD conversion circuit 4, and changes the state of the detection signal C from L to H as described later. The switching circuit 8 is normally connected to the A side and outputs the clamp pulse A. However, when the detection signal C becomes H, it is connected to the B side and outputs the clamp pulse B. Next, the operation of detecting a change in black level will be described in detail with reference to FIG. FIG. 2 is a timing chart for explaining the operation of the solid-state imaging device according to the first embodiment of the present invention. In FIG. 2, 2a is a waveform of the analog signal a, 2b is a data array of the digital signal b, 2c is a pre-pranking pulse waveform indicating a horizontal retrace period from the horizontal optical black h1 to the horizontal optical black h2, 2A.
Is a waveform of the clamp pulse A, 2B is a waveform of the clamp pulse B, va is a clamp voltage at a normal time, vb is a reference voltage for detecting a black level fluctuation, vc is an example of a clamp voltage at a black level fluctuation, and va ≦ vb <Vc. The analog signal a output from the clamp circuit 3 is applied to the horizontal optical black portion h in the horizontal direction (the direction of the arrow X).
2. Corresponding to the imaging area d and the horizontal optical black portion h1, the clamp level is usually clamped by the clamp pulse A so that the black level voltage becomes the clamp voltage va. Next, the analog signal a is composed of a horizontal optical black portion h2, an imaging region d, a horizontal optical black portion h1, and data b1, b2, b3, and b4 corresponding to a horizontal blanking period in the horizontal direction by the AD conversion circuit 4. It is converted to a digital signal b. The black level fluctuation detection circuit 9 prepares digital data corresponding to the reference voltage vb for detecting the black level fluctuation in advance. It is assumed that the horizontal optical plaque h1 has been fluctuated by the high-luminance object e. The signal output from the solid-state imaging device 1 is converted into a continuous signal by the sample-and-hold circuit 2 and supplied to the clamp circuit 3 in the same manner as in the normal case. However, the horizontal optical signal of the analog signal a clamped by the clamp circuit 3 is used. Black part h1
Is not the clamp voltage va but the clamp voltage vc. The analog signal a having become the clamp voltage vc is converted into a digital signal b by the AD conversion circuit 4. At this time, since the data b3 is digital data corresponding to the clamp voltage vc, when the black level fluctuation detecting circuit 9 acquires the data b3 of the digital signal b, the digital data corresponding to the previously prepared reference voltage vb Detects fluctuations in black level by comparing with
The detection signal C changes its state from L to H and outputs it. The switching circuit 8 outputs a clamp pulse A based on the detection signal C.
, And switches to the clamp pulse B, and outputs the same to the clamp circuit 3. Since the clamp circuit 3 clamps at the timing of the clamp pulse B, it clamps the horizontal optical black portion h2 to the reference voltage va. At this time, since there is no high-luminance subject e on the side of the horizontal optical black portion h2, a normal black level can be obtained. When the horizontal optical black portion h1 is no longer affected by the high-luminance subject e and the data b3 is compared with the digital data corresponding to the black-level fluctuation detection reference voltage vb and it is determined that the data b3 has returned to the normal black level, the detection signal C is output. By returning the state from H to L and outputting the same, the switching circuit 8 switches from the clamp pulse B to the clamp pulse A, outputs the same, supplies the same to the clamp circuit 3, and returns to the normal operation. Since the horizontal optical black parts h1 and h2 are located on the opposite sides of the screen, objects with strong light such as the sun do not exist at both ends of the screen at the same time, and a normal black level is always obtained at either side. You can get. As described above, according to the first embodiment, the solid-state imaging device having the first optical black portion and the second optical black portion optically shielded at both ends in the horizontal direction of the imaging region. 1, a clamp circuit 3 for clamping the black level of the output signal of the solid-state imaging device 1, and an A / D converter for AD-converting the output signal clamped by the clamp circuit 3.
Black level fluctuation detection for generating a black level fluctuation detection signal by detecting, using the digital signal output by the AD conversion circuit 4, when the black level of the output signal fluctuates, A circuit 9, a clamp pulse generating means for generating a first clamp pulse and a second clamp pulse for the clamp circuit 3 to clamp the black level of the output signal, and a first clamp pulse and a second clamp pulse. A switching circuit (8) for switching based on a black level fluctuation detection signal and supplying it to the clamping means;
Is a pulse for clamping only the first optical black portion, and the second clamp pulse is a pulse for clamping only the second optical black portion. It is possible to always supply a solid-state imaging device having a stable black level irrespective of shooting and high-brightness shooting. In the first embodiment, the switching circuit 8 and the synchronizing signal generating circuit 7 have different configurations.
May be incorporated in the synchronization signal generation circuit 7. Although the black level detecting means is a black level detecting circuit, the processing may be performed by software such as a microcomputer. Further, although the detection signal C is an L or H control signal, it may be a command such as serial data. As described above, according to the present invention, when photographing a normal subject, the horizontal optical black portion h1 is clamped, and a high-luminance subject of strong light is photographed, and the black level varies. In this case, by switching to clamp the horizontal optical black portion h2 which is not affected, it is possible to always supply a solid-state imaging device having a stable black level irrespective of normal shooting or high brightness shooting.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a configuration of a solid-state imaging device according to a first embodiment of the present invention. FIG. 2 is a timing chart for explaining an operation of the solid-state imaging device according to the first embodiment. 3 is a schematic diagram showing a configuration example of the solid-state imaging device 1. FIG. 4 is a block diagram illustrating a conventional solid-state imaging device. [Description of References] 1 solid-state imaging device 2 sample hold (S / H) circuit 3 clamp circuit 4 AD Conversion circuit 5 Digital signal processing circuit 6 Synchronous signal generating circuit 7 Synchronous signal generating circuit 8 Switching circuit 9 Black level fluctuation detecting circuit

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 5C021 PA13 PA52 PA62 PA92 SA11                       XA42 XA48                 5C024 CX04 GY01 GZ38 HX09 HX13                       HX23 HX29 HX50

Claims (1)

Claims: 1. A solid-state imaging device having a first optical black portion and a second optical black portion optically shielded at both ends in a horizontal direction of an imaging region, and the solid-state imaging device. Clamp means for clamping the black level of the output signal of the element; analog-digital conversion means for performing an analog-to-digital conversion of the output signal clamped by the clamp means; and when the black level of the output signal fluctuates, the black level changes. A black level fluctuation detecting means for detecting the fluctuation using a digital signal output by the analog-digital converting means to generate a black level fluctuation detecting signal, and the clamping means for clamping a black level of the output signal. Clamp pulse generating means for generating a first clamp pulse and a second clamp pulse of the first Switching means for switching the pulse and the second clamp pulse based on the black level variation detection signal and supplying the same to the clamp means, wherein the first clamp pulse clamps only the first optical black portion. A solid-state imaging device, wherein the second clamp pulse is a pulse for clamping only the second optical black portion.