JP2977056B2 - Solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an XY address type solid-state image pickup device used in a television camera or the like, and more particularly, to an optical black (hereinafter abbreviated as OB) pixel portion in each vertical pixel column. The present invention relates to a solid-state imaging device having a type that has an effect of suppressing blooming on an OB pixel portion.

[0002]

2. Description of the Related Art In general, an XY address type solid-state imaging device includes a pixel array 101 in which a large number of pixels are arranged in a matrix as shown in FIG. One pixel is composed of one photodiode, and a bias voltage applied to this diode is applied to a vertical shift register (vertical scanning).
A pixel signal based on an optical signal is fetched by controlling with a pulse from the scanning circuit 102, and then a horizontal scanning switch 104 is opened and closed by a horizontal shift register (horizontal scanning circuit) 103 to send a video signal to an output line 105. It has become. And the pixel array 101
Is formed separately from the light receiving pixel portion 101-1 and an OB pixel portion 101-2 in which a light receiving pixel is covered with a light-shielding film. It is an optical black part to create a level.

Normally, the OB pixel section 101-2 is arranged in parallel with the vertical shift register 102 as shown in FIG. 4 so that the OB pixel section is read every horizontal read cycle. For example, when pixel reading needs to be performed at a high driving frequency, the horizontal cycle is short,
There is a drawback that the readout period of the pixel portion is shortened and it is difficult to use the circuit.

That is, the signal from the OB pixel becomes the reference black level after being clamped on the circuit, but the period required for clamping is generally 1 μs or more, and therefore the OB
It takes about 2 μs to read out the pixel section.
When the OB pixel portion is arranged in parallel with the vertical shift register as shown in FIG. 2, when 256 lines are read out in one field, the required reading time of the OB pixel portion is 2 ×
256 = 512 μs. Assuming that reading is performed at a high speed of 10 times speed, 1 field = 1 ÷ (60 × 10) ≒ 1670
In μs, the result is 512 ÷ 1670 結 0.31, which means that sufficient clamping cannot be performed unless 31% of the entire pixel array is allocated to the OB pixel portion.

As a measure to overcome this, as shown in FIG.
A structure in which the B pixel section 101-2 is provided in parallel with the horizontal shift register 103 has been considered. In this configuration, since there is a sufficient clamping period during one horizontal scanning period (1670 ÷ 256 = 6.5 μs), the OB pixel portion may be one horizontal line, and the proportion of the OB pixel in the entire pixel array is 1, 25
6 ≒ 0.004, that is, a calculation less than 0.5% is sufficient, and it can be said that the type in which the OB pixels are arranged in parallel with the horizontal shift register is effective for high-speed reading.

[0006]

However, in the case of the arrangement of the OB pixel section shown in FIG. 5, excessive current from a light receiving pixel due to a large amount of incident light is transmitted to other light receiving pixels via a vertical common line. Intrusion, which causes blooming as shown in FIG. 6, and produces a flaw P on the video signal as shown in FIG.

If the flaw P is mixed into the OB pixel portion, the reference black level will be disturbed, causing a misclamp and disturbing the entire video signal. That is, in general, as shown in FIG. 8, the OB pixel signal clamping circuit connects a series capacitor 112 to the output side of a buffer 111 provided on the video signal line, and sets the output side of the capacitor 112 to the reference black level a. Switch the corresponding DC power supply 113
Through a switch 113.
Is turned on / off at a constant cycle by a clamp pulse shown in FIG. 9, and the average potential on the video signal line during the on period is set to the reference black level. Therefore, if there is a flaw component due to blooming as shown in FIG. , The clamp potential becomes a level b different from the original reference black level a, and a misclamp state occurs, and the black level of the entire screen fluctuates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in a conventional XY address type solid-state image pickup device provided with an OB pixel portion for each pixel column in the vertical direction. It is an object of the present invention to provide a solid-state imaging device in which blooming is not mixed into an OB pixel portion.

[0009]

In order to solve the above problems, the present invention is directed to a vertical pixel column having a light receiving pixel portion and an optical black pixel portion as shown in the conceptual diagram of FIG. Are connected by vertical common lines,
X- which reads pixel signals through the common line
In the Y-address type solid-state imaging device, the light receiving pixel portion A
And the common line D of the optical black pixel portion B are separated from each other.

In the solid-state image pickup device having the above-described configuration, the common lines C and D in the vertical direction are connected to the light receiving pixel portions A and
Since the light is separated from the pixel section B, an excessive current of the light receiving pixel section A due to a large amount of incident light is prevented from entering the OB pixel section B, and a reference black level free from scratches can be obtained.

[0011]

Next, an embodiment will be described. FIG. 2 is a circuit diagram showing a first embodiment of the solid-state imaging device according to the present invention. In the figure, reference numeral 1 denotes a light-receiving pixel portion in which light-receiving pixels are arranged in a matrix, and 2 denotes an OB pixel portion formed by covering a light-shielding film on the pixel portion, which is formed completely separated from the light-receiving pixel portion 1. . Pixel columns arranged in the horizontal direction of the light receiving pixel unit 1 and the OB pixel unit 2 share a vertical selection line 3-
1, 3-2,..., 3-5 and 4-1 and 4-2, respectively, and a vertical selection pulse is supplied from the vertical shift register 5.

The pixel columns arranged in the vertical direction of the light-receiving pixel section 1 are commonly connected to signal lines 6-1, 6-2,... 6-6, and each signal line is connected to a horizontal shift register 7. And is connected to a light receiving pixel output line 9 via a horizontal scanning switch 8 driven by. On the other hand, signal lines 10-1, 10-2,..., 10-6 are commonly connected to the pixel columns arranged in the vertical direction of the OB pixel section 2, and each signal line is driven by the horizontal shift register 7. OB pixel output line via the horizontal scanning switch 11
Connected to 12.

Each of the output lines 9 and 12 has a changeover switch 13 controlled by a control signal from the vertical shift register 5.
Through the common output line 14.

In this embodiment, the completely separated light receiving pixel unit 1 and OB pixel unit 2 are controlled by two horizontal scanning switches 8 and 11 driven by one horizontal shift register 7. And a switch 13 for controlling the output lines 9 and 12 provided separately in the light receiving pixel unit 1 and the OB pixel unit 2 by the vertical shift register 5 in order to prevent intrusion of excessive current from the light receiving pixel unit 1. Thus, the OB pixel output line 12 is controlled so as to be connected to the OB output side when reading out, and the light receiving pixel output line 9 is connected to the light receiving output side when reading out the light receiving pixel output line 9. Thus, it is possible to prevent an excessive current from entering the OB pixel unit 2 from the light receiving pixel unit 1 and obtain a reference black level free from scratches.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention. Members which are the same as or correspond to those of the first embodiment shown in FIG. 2 are denoted by the same reference numerals. In this embodiment, two horizontal shift registers 7-1 and 7-2 are provided, and the light-receiving pixel unit-side horizontal scanning switch 8 and the OB pixel unit-side horizontal scanning switch 11 are connected to separate horizontal shift registers 7-1 and 7-. 2 is configured to be driven. In this embodiment, a changeover switch for switching and connecting the output lines 9 and 12 is not required.

[0016]

As described above with reference to the embodiments,
According to the present invention, since the common line of the light receiving pixel portion and the common line of the OB pixel portion are separated, blooming is prevented from being mixed into the OB pixel portion, and even at the time of high-speed reading,
A reference black level without misclamp can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for explaining a solid-state imaging device according to the present invention.

FIG. 2 is a circuit configuration diagram showing a first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a second embodiment.

FIG. 4 is a circuit diagram showing a configuration example of a conventional XY address type solid-state imaging device.

FIG. 5 is a circuit configuration diagram showing another configuration example of a conventional XY address type solid-state imaging device.

FIG. 6 is a diagram showing a mode of occurrence of blooming.

FIG. 7 is a diagram illustrating a video signal in which a scratch due to blooming has occurred.

FIG. 8 is a diagram showing a clamp processing circuit for an OB signal.

9 is a signal waveform diagram for explaining an operation of the clamp processing circuit shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light-receiving pixel part 2 OB pixel part 3-1 ..., 4-1 ... Vertical selection line 5 Vertical shift register 6-1 ... Signal line 7 Horizontal shift register 8 Horizontal scanning switch 9 Light-receiving pixel Output line 10-1, ... Signal line 11 Horizontal scanning switch 12 OB pixel output line 13 Changeover switch

Claims (4)

(57) [Claims] 1. An XY address system in which each vertical pixel row having a light receiving pixel portion and an optical black pixel portion is connected by each vertical common line, and a pixel signal is read through the common line. Wherein the common line of the light receiving pixel portion and the common line of the optical black pixel portion are separated from each other. 2. The method according to claim 1, wherein the light receiving pixel unit and the optical unit
The common line of the black pixel section is a horizontal scanning circuit
Via first and second switches controlled by
Light receiving pixel output line and optical black pixel
Output line, the light receiving pixel output line and the
The optical black pixel output line is the third switch
Characterized by being connected to a common output line via
The solid-state imaging device according to claim 1. 3. The vertical switch according to claim 3, wherein the third switch is a vertical scanning circuit.
3. The solid-state imaging device according to claim 2, wherein
element. 4. The light receiving pixel section and the optical
The common lines of the black pixel portion are the first and second lines, respectively.
First and second switches controlled by the horizontal scanning circuit of FIG.
Through the light receiving pixel output line and the optical
.Connected to the black pixel output line, the light receiving pixel output
Line and the optical black pixel output line
2. The solid-state imaging device according to claim 1, wherein the imaging device is connected in common.
Image element.