JPH0583547A - Photoelectric converter - Google Patents

Abstract

PURPOSE:To reduce the number of elements constituting a read system circuit by extracting a noise output only from one part of picture elements and using the output for correcting the noise of neighbor picture elements. CONSTITUTION:The noise levels of partial picture elements 1, m+1 and 2m+1 are detected, and the signal levels of all the picture elements 1-3m are corrected according to the detected noise levels of the partial picture elements 1, m+1 and 2m+1. Namely, this device is equipped with the picture element parts 1-3m to output electric signals corresponding to the quantity of incident light, signal output line 13 to output signals (S) extracted from the picture elements 1-3m, and noise output line to output noise extracted only from the picture elements 1, m+1 and 2m+1 among the respective picture elements 1-3m, and the picture elements to output the noise are limited to only the partial picture elements 1, m+1 and 2m+1 among all the picture elements 1-3m. In this case, one block is composed of one step of a picture element constituting element A and the (m-1) steps of picture element constituting elements B, and signals outputted from the respective picture elements in one block are respectively corrected by the noise outputted from the constitutive element A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device, and more particularly to a photoelectric conversion device for correcting noise of a photoelectric conversion element.

[0002]

2. Description of the Related Art Conventionally, in order to correct noise included in an output signal of a photoelectric conversion element, a noise output and a signal output are taken out from each pixel and a process of subtracting the noise output from the signal output has been performed. For example, the same structure as a bipolar transistor is used, and the base region (it becomes the control electrode region)
Carriers accumulated in the emitter (becomes the main electrode region)
In a photoelectric conversion device using an amplification type photoelectric conversion element taken out from, the processing is performed by the following readout system circuit.

FIG. 8 is a conceptual diagram of a read line of a conventional photoelectric conversion device. FIG. 9 is an equivalent circuit diagram of one pixel of a readout system circuit for extracting the signal output and noise output of the conventional example. The circuit shown in FIG. 9 shows an equivalent circuit of the constituent element A of the pixel 1 in FIG.

In FIG. 8, 1 to 3 m are pixel portions for outputting electric signals corresponding to the amount of incident light, 13 is a signal output line for outputting a signal (S) taken out from the pixels 1 to 3 m, 1
Reference numeral 4 is a noise output line that outputs noise (N) extracted from the pixels 1 to 3 m.

In FIG. 9, reference numeral 21 denotes a bipolar transistor (which serves as an amplification type photoelectric conversion element) forming a pixel,
22 NMOS transistors serving as switching means operated by pulse phi _VRS for resetting to connect the emitter of the bipolar transistor 21 to the reference voltage V _R, 23 is reset to connect the base of the bipolar transistor 21 to the reference voltage V _BB A PMOS transistor, which operates as a switch means by a pulse φ _{RES for} performing, a transfer capacitor C _TS for temporarily holding the signal output to the emitter of the bipolar transistor 21, CTS, 2
Reference numeral 7 is a transfer capacitance C _TN for temporarily holding the noise output to the emitter of the bipolar transistor 21, and 24 is a pulse φ for transferring the signal output to the emitter of the bipolar transistor 21 to the transfer capacitance C _TS 26. An NMOS transistor serving as switch means operated by _TS , 25 is an NMOS transistor serving as switch means operated by a pulse φ _TN for transferring noise output to the emitter of the bipolar transistor 21 to the transfer capacitor C _TN 27, 28, 29 Are transfer capacities C _TS 26,
N as a switch means which is operated by the pulse φ _CRS for connecting the C _TN 27 to the reference voltage V _R and performing the reset.
MOS transistors, 32 and 33, output lines for outputting signals and noise, respectively, and 30 and 31, output signals and noise, which are temporarily held in the transfer capacitors C _TS 26 and C _TN 27, to the output lines 32 and 33, respectively. It is an NMOS transistor as a switch means that operates by a pulse φ _{SR for} .

The operation of the above configuration will be described with reference to the timing chart of FIG.

FIG. 10 is a timing chart for explaining the operation of the above photoelectric conversion device.

First, a positive pulse voltage is applied to φ _CRS to reset the charges remaining in the transfer capacitors C _TS 26 and C _TN 27. Then, a positive pulse voltage is added to φ _TS , the emitter of the bipolar transistor 21 and the transfer capacitor C _TS 26 are connected, and the signal voltage output to the emitter is transferred to the transfer capacitor C _TS 26 (signal reading operation). ..

Next, a negative pulse voltage is added to φ _RES to clamp the base of the bipolar transistor 21 to the reference voltage V _BB . Then, a positive pulse voltage is added to φ _VRS to cause the emitter of the bipolar transistor 21 to have a reference voltage V
_R is connected to the base of the bipolar transistor 21
A current flows between the emitters and carriers remaining in the base disappear (reset operation).

Next, a positive pulse voltage is added to φ _TN , the emitter of the bipolar transistor 21 and the transfer capacitance C _TN 27
And the noise voltage output to the emitter is transferred to the transfer capacitor C _TN 27 (noise reading operation).
After the reset operation is repeated once more, the base and emitter of the bipolar transistor 21 are brought into a floating state to start accumulation of photocharges, and at the same time, the transfer capacitance C _TS 26,
The signal and noise temporarily held in the C _TN 27 are output to the output lines 32 and 33, respectively (accumulation operation).

When the accumulation operation is completed, the signal reading operation is resumed, and a series of operations are sequentially repeated.

A noise-corrected image signal can be obtained by taking the differential output of the signal output and the noise output by the above sensor operation.

[0013]

However, in the above-mentioned conventional example, for each pixel, a signal output MOS transistor, a noise output MOS transistor, a transfer capacitor,
Since the wiring is required, there is a problem that it becomes an obstacle to miniaturization of the pixel, and the chip area increases, which causes a cost increase.

It is an object of the present invention to provide a photoelectric conversion device in which the number of constituent elements of each pixel readout system circuit is reduced by increasing the efficiency of the correction circuit in order to solve the above problems.

[0015]

In order to achieve the above object, the photoelectric conversion device of the present invention detects the noise level of a part of pixels, and detects all the noise levels by the detected noise level of a part of pixels. It is characterized in that the signal level of the pixel is corrected.

Further, the photoelectric conversion device of the present invention detects the noise level of at least one line sensor among the arrayed line sensors, and detects the signal level of all line sensors according to the detected noise level of the line sensor. It is characterized by correcting the level.

[0017]

In the noise correction method of extracting the noise output and the signal output from each pixel and subtracting the noise output from the signal output described with reference to FIGS. Fixed pattern noise due to manufacturing variations for each pixel. It is possible to correct two types of shading noise caused by the inclination of the characteristic distribution in each pixel and the chip of the readout circuit system.

Although the fixed pattern noise of has various values for each pixel, the shading of results from the slope of the characteristic distribution, so that the noise of the pixel has a value close to the noise of the neighboring pixels. Focusing on the taking, when the shading noise is dominant as compared with the fixed pattern noise of, it has been found that the signal from the pixel can be corrected by the noise output from the neighboring pixels, and the present invention has been achieved. Is.

That is, the photoelectric conversion device of the present invention is used for noise correction when the noise from some pixels has a value close to the noise of other pixels, such as the noise of shading. The signal output and noise output are taken out from some pixels, only the signal output is taken out from other pixels, and the noise output from the other pixels is substituted for the noise output of the other pixels to correct the signal output. As a result, the number of constituent elements of the read circuit system required for noise output is significantly reduced.

Further, the photoelectric conversion device of the present invention takes out the noise output of at least one line of the plurality of line sensors, and substitutes this noise output to correct the signal level of all the line sensors to obtain the noise output. Therefore, the number of constituent elements of the readout circuit system, which is necessary for that purpose, is significantly reduced.

[0021]

Embodiments of the present invention will be described in detail below with reference to the drawings. (First Embodiment) This embodiment is an example in which noise correction is performed by the present invention when the shading caused by the inclination of the characteristic distribution in the chip is more dominant than the fixed pattern noise which is the variation for each pixel. ..

FIG. 1 is a conceptual diagram of a read line of a photoelectric conversion device according to the first embodiment of the present invention. FIG. 2 shows the first of the present invention.
FIG. 7 is an equivalent circuit diagram of a read-out circuit for one pixel that extracts only the signal output of the photoelectric conversion device of the example.

Since the constituent members shown in FIG. 2 are the same as the constituent members shown in FIG. 9, the same reference numerals are given and the description thereof will be omitted.

In FIG. 1, 1 to 3 m are pixel portions for outputting electric signals corresponding to the amount of incident light, 13 is a signal output line for outputting a signal (S) taken out from the pixels 1 to 3 m, 1
4'is pixel 1, m + 1, 2m + 1 in each pixel 1-3m
It is a noise output line that outputs the noise (N) extracted only from. That is, in the present embodiment, it is a part of all the pixels 1 to 3 m that outputs noise, that is, a pixel 1, m +
Only 1,2m + 1. Here, pixels 1, m + 1, 2
The constituent element A of m + 1 is the same as the equivalent circuit shown in FIG. 9 of the conventional example, and the pixels 2 to m, m + 2 to 2m, and 2m + 2.
The 3 m component B is the equivalent circuit shown in FIG.
This is a read-out system circuit only for signal output, in which a read-out system circuit for noise output is eliminated from the equivalent circuit shown in FIG. In this embodiment, one stage of the pixel component A having the same circuit configuration as that of the conventional example shown in FIG. 9 and m− of the pixel component B shown in FIG.
One stage constitutes one block, and the signal output from each pixel in one block is noise-corrected using the noise output from the constituent element A.

FIG. 3 is a diagram showing the correspondence between the noise output of each pixel and the pixel. As shown in FIG. 3, the noise output (N) of each pixel is dominated by the shading caused by the inclination of the characteristic distribution in the chip rather than the fixed pattern noise which is the variation for each pixel. In such a case, if a noise output of one pixel is obtained for every several pixels, it may be used as a noise correction in the vicinity by correlating and substituting.

FIG. 4 is a circuit diagram of a differential circuit for correcting the signal level of a pixel, which is connected to the signal output line 13 and the noise output line 14 '.

In FIG. 4, 41 is a sample hold (S / S) for sampling and holding the noise output (S).
H) circuit, N ′ is a noise output in which a noise output of a predetermined pixel (for example, pixel 1) is continuously output for a period of m pixels sampled and held, and 42 is a signal output (S) and a sampled and held noise output ( N ') is a differential amplifier for taking the differential, 43 is an output terminal, and SN' is a differential output.

The noise correction operation in the above configuration will be described below.

First, the signal output of the pixel 1 shown in FIG. 1 is read out to the signal output line 13, the noise output (N) of the pixel 1 is read out to the noise output line 14 ', and then the signal output of the pixel 2 (S). ) Is read out to the output line 13. This read operation is performed by the circuits shown in FIGS. 9 and 2 as described in the conventional example. Hereinafter, the output of each pixel is sequentially pixel 1, m +
Only 1 and 2m + 1 signal output (S) and noise output (N),
Only the signal output (S) is read from the other pixels.

Next, noise correction is performed by the circuit shown in FIG. In the following description, the signal of a certain pixel i is S
i and noise are described as Ni.

First, the signal output S ₁ of the pixel 1 is directly input to the positive input terminal of the differential amplifier 42, and the noise output N ₁ of the pixel ₁ is input to the negative input terminal of the differential amplifier 42 through the sample hold circuit 41. , (S ₁ −N ₁ ) obtained by canceling the noise component and correcting the noise is obtained at the output terminal 43. Next pixel 2
When the signal output S _{2 of} is output to the output line 13, it is directly input to the positive input terminal of the differential amplifier 42, and the pixel 1
Noise output N ₁ is input. Therefore, (S ₂ −N ₁ ) is output to the output terminal 43. Thus, (S ₁ −
_{N 1), (S 2 -N} 1), (S 3 -N 1), (S 4 -N
₁ ), ..., ( _{Sm + 1-} Nm _{+ 1} ), ( _{Sm + 2-} Nm _{+ 1} ),
( _{Sm + 3−} Nm _{+ 1} ), ( _{Sm + 4−} Nm _{+ 1} ), ..., (S
_{2m + 1-} N2m _{+ 1} ), ( _{S2m + 2-} N2m _{+ 1} ), ( _{S2m + 3-} N
_{2m + 1} ), (S _{2m + 4-} N _{2m + 1} ), ... Are output to the output terminal 43.

As explained above, the noise output N is shown in FIG.
If the shading is dominant over the fixed pattern noise as described above, the image unevenness due to the shading can be improved and a sufficient correction effect can be obtained even with such noise correction. (Second Embodiment) In this embodiment, the signal level of all line sensors is corrected by the noise level of one of the arranged R, G, B line sensors.

FIG. 5 is an equivalent circuit diagram of a read system circuit for taking out the signal and noise output of the photoelectric conversion device according to the second embodiment of the present invention.

In the figure, 21R, 21G, 21B
Are bipolar transistors forming pixels of R signal, G signal and B signal respectively, and 22R, 22G and 22B are bipolar transistors 21R, 21G and 21B, respectively.
As switch means operated by φ _VRS for connecting the emitter of the transistor to the reference voltage V _R and performing reset
Transistors 23R, 23G and 23B are NMOS transistors as switch means which are operated by φ _RES for connecting the bases of the bipolar transistors 21R, 21G and 21B to the reference voltage V _BB and resetting, and 26R, 26G and 26B, respectively. Transfer capacitors C _TRS , C for temporarily holding the signals output to the emitters of the bipolar transistors 21R, 21G, 21B
_TGS , C _TBS and 27R are bipolar transistors 21R
Of the transfer capacitors _CTRN , 24R, 24G, and 24B for temporarily holding the noise output to the emitters of the bipolar transistors 21R, 21G, and 21B, respectively.
An NMOS transistor as a switch means operated by φ _TS for transferring to the transistor, 25R is an NMOS transistor as a switch means operated by φ _TN for transferring the noise output to the emitter of the bipolar transistor 21R to the transfer capacitor C _TRN 27R. Transistor, 28R, 28
G and 28B are transfer capacities 26R, 26G and 26B, respectively.
_Is connected to the reference voltage V _R and reset by φ _{CRS, which} is an NMOS transistor as a switch means,
29R is an NMOS transistor, 32R, 32G, 32 as a switch means which operates by φ _CRS for connecting the transfer capacitance C _TRN 27R to the reference voltage V _R and resetting it.
B and 33R are signals R _S , G signals G _S , and B signals B, respectively.
_S, an output line for outputting the R noise R _N, 30R, 3
0G, 30B and 31R are transfer capacities 26R and 26, respectively.
G, 26B, a signal temporarily stored in the transfer capacitor C _TRN 27R, noise is an NMOS transistor as a switch means operated by φ _SR for outputting to the output lines 32R, 32G, 32B, 33R.

FIG. 6 is a block diagram of an RGB three-line sensor having the reading system circuit of FIG. 5 as a constituent element. In FIG. 6, R1 to R8 are pixels for R (Red) signals, G1 to G8 are pixels for G (Green) signals, and B1.
To B8 are pixels for B (Blue) signals, RO1 to RO8
Are read-out circuits for R1, G1, B1 to R8, G8 and B8, respectively. In the above configuration, the R, G and B pixels simultaneously perform the sensor operation as in the conventional example,
As output, only R outputs signal R _S and noise R _N ,
For G and B, only signals G _S and B _S are output.

FIG. 7 is a differential circuit diagram for correcting the signal level of the RGB three-line sensor. In FIG.
2G and 42B are differential amplifiers for R, G and B, respectively, and 43R, 43G and 43B are R, G and B differential output terminals, respectively.

By using a circuit as shown in FIG. 7, R
The output terminal 43R is output differential output of the R signal R _S and R noise _{R N (R out = R S} -R N) is, G output terminal 43
For G, the differential output of G signal G _S and R noise R _N (G _out =
G _S -R _N) is outputted, the B output terminal 43B differential output of the B signal B _S and R noise _{R N (B out = B S} -R N)
Is output. As described above, in the present embodiment, a simple readout system circuit for outputting only R noise is used.
Shading correction of three outputs of G and B can be performed and image unevenness can be improved.

[0038]

As described in detail above, in the photoelectric conversion device of the present invention, the noise output is taken out from only some pixels and is used for noise correction of neighboring pixels, so that the number of constituent elements of the readout system circuit is increased. Can be significantly reduced. In addition, the noise output of at least one line of the multiple line sensors is taken out, and the noise output is used as a substitute to correct the signal level of all line sensors, thereby configuring the readout circuit system necessary for noise output. The number of elements can be significantly reduced.

As a result, the photoelectric conversion device of the present invention is advantageous for miniaturization of pixels, and has an effect of reducing the chip area and cost.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a read line of a photoelectric conversion device according to a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a read-out circuit for one pixel that extracts only the signal output of the photoelectric conversion device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing correspondence between noise output of each pixel and pixel.

FIG. 4 is a circuit diagram of a differential circuit for correcting a signal level of a pixel, which is connected to a signal output line 13 and a noise output line 14 '.

FIG. 5 is an equivalent circuit diagram of a read system circuit for extracting a signal and noise output of the photoelectric conversion device according to the second embodiment of the present invention.

6 is an RGB diagram in which the readout system circuit of FIG. 5 is a component.
3 is a block diagram of the 3-line sensor of FIG.

FIG. 7 is a signal level correction differential circuit diagram of the line sensor of the second embodiment of the present invention.

FIG. 8 is a conceptual diagram of a read line of a conventional photoelectric conversion device.

FIG. 9 is an equivalent circuit diagram of one pixel of a readout system circuit that extracts a signal output and a noise output of a conventional example.

FIG. 10 is a timing chart illustrating the operation of the photoelectric conversion device of the conventional example.

[Explanation of symbols]

1 to 3 m pixel 13 signal output line 14 noise output line 14 'noise output line 41 sample hold circuit 42 differential amplifier S signal output N noise output R _S R signal output R _N R noise output G _S G signal output B _S B signal Output R1 to R8 R signal pixel G1 to G8 G signal pixel B1 to B8 B signal pixel 42R R differential amplifier 42G G differential amplifier 42B B differential amplifier

Claims (2)

[Claims] 1. A photoelectric conversion device, characterized in that the noise level of some pixels is detected, and the signal levels of all pixels are corrected by the detected noise levels of some pixels. 2. A plurality of line sensors arranged,
A photoelectric conversion device characterized by detecting a noise level of at least one line sensor and correcting the signal levels of all the line sensors according to the detected noise level of the line sensor.