JPH022792A - Infrared image pickup element and its driving method - Google Patents

Abstract

PURPOSE:To correct the sensitivity and the dark current of each image element individually and to remarkably reduce a noise of fixed pattern by impressing a bias voltage on each of detectors after outputting a signal from an individual detector in a detector group. CONSTITUTION:A signal charge corresponding to an incident infrared ray from an abject photoelectrically transduced and accumulated by an ultraviolet ray image pickup element 3 is read out in a row direction row by row by a horizontal scan pulse supplied from an X shift register 1 at every cycle to a gate of a transistor TRTrmn, and is accumulated in a capacitor Cn. And a reset TRTrR supplies the drain voltage of the TRTrR to a diode Dmn by a reset operation via a TRTrR, a TRTrhn, the accumulation capacitor Cn, and a TRTrmn in the above sequence. Therefore, an output signal in which dispersion in the sensitivity and the dark current are reduced can be obtained by controlling the voltage supplied from a D/A converter 6 to the drain of the TRTrR at every image element so as to correct the dispersion in the sensitivity and the dark current of each diode Dmn.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an infrared imaging device, and more particularly to an infrared imaging device in which a plurality of detector groups are configured in one or two dimensions, and a method for driving the same.

[Conventional technology]

Mercury cadmium telluride (HgCdT
Infrared imaging devices using detectors made of materials such as InSb and indium antimony (InSb) are known.

FIG. 4 is a schematic configuration diagram showing an example of the configuration of a two-dimensional infrared imaging device in which detectors are arranged two-dimensionally as an example of such an infrared imaging device. In the figure, the detector is Hg
A diode using materials such as CdTe or InSb.
The plurality of diodes Dll, 012°013~Dmn
are arranged two-dimensionally in the row (X) and column (Y) directions, and each diode has a transistor Trl for reading out signals.
l, Tr12. Tr13 to Trmn are combined.

In each diode, the signal charge generated by photoelectric conversion of the incoming infrared rays is transferred from the X-shift register 13 to the transistor Trmn (+=1, 2e-m, n=:1
, 2°...n), the diode D11,021,031,041→01
2. D22. D32. D42 → D13, D23. D3
3... are read out in the order of storage capacitor Cn (n=
1,2t=・n). Transistor TrQn
(n=Q1.Q, ...Qn) is the diode Dun
(m=1e2.-m, n=1°2, . . . n), and a constant voltage is applied to its gate.

Next, the transistor Tr connected to the storage capacitor Cn
hn is for reading out the signal charge accumulated in the storage capacitor Cn, and Trh is used from the Y-shift register 14.
C1, C2 by the scanning pulse supplied to the gate of n
, C3, C4, etc., and the read signal charges are output to the outside via the buffer transistor Tro. The reset transistor TrR resets the signal charge every period of the scanning pulse supplied to the gate of the Y-shift register 14 or Trhn.

[Problem to be solved by the invention]

In the conventional technology described above, the sensitivity and dark current of each diode serving as a detector are not constant, but vary from pixel to pixel, resulting in well-known fixed pattern noise.

In order to remove this fixed pattern noise, the fixed pattern noise information was conventionally stored in digital memory to correct the video signal, but the size of the fixed pattern noise was larger than the target video signal. Correction requires a resolution of 12 to 16 bits for the A/D converter that captures the fixed pattern noise information, which makes correction difficult, increases the size of the imaging device, and has the disadvantage of poor image quality. 6. It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and to provide an infrared imaging device with small fixed pattern noise and a method for driving the same.

[Means to solve the problem]

In order to achieve the above object, the infrared imaging device of the present invention includes a plurality of detector groups arranged one-dimensionally or two-dimensionally that receive incident infrared rays and perform photoelectric conversion, and a group of detectors that perform photoelectric conversion by this detector group. In an infrared imaging device equipped with a scanning means for sequentially scanning and reading out signal charges corresponding to incident infrared rays accumulated at regular intervals, each detection is performed after outputting a signal from each detector of the detector group. The device has means for applying a bias voltage to each of the devices.

Furthermore, in the method for driving an infrared imaging device of the present invention,
The infrared rays incident on a plurality of detector groups arranged one-dimensionally or two-dimensionally are photoelectrically converted and accumulated, and the accumulated signal charges corresponding to the incident infrared rays are sequentially scanned at regular intervals and read out 5 individually. After outputting the signals from the detectors, a bias voltage is applied to each detector, and the applied bias voltage is controlled for each detector.

[Effect]

The bias voltage applied to each detector is applied in correspondence with the fixed pattern noise of each detector, and the bias voltage applied to each detector is controlled based on the fixed pattern noise information stored in the storage means. The operating point of each device is set independently.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing the configuration of an infrared imaging device according to the present invention. In the figure, the detector is HgCdTe or In
A diode using a substance such as Sb, and a plurality of diodes D11,012,013-Dmn are arranged two-dimensionally in the row (X) and column (Y) directions, and each diode is equipped with a transistor for reading out signals. Trll, Tr12.
Tr13 to Trmn are combined.

In each diode, the signal charge generated by photoelectric conversion of the incoming infrared rays is transferred from the X-shift register 1 to the transistor Trmn (m=1.2t=m, n=1.2
Dll, 021,031,041→012. D22. D
32. D42→013. D23. D33... is read out in the order of storage capacitor Cn (n = 1.2°...
・Accumulated in n).

Next, the transistor Tr connected to the storage capacitor Cn
hn (hn=h1*t12t"'hn) is for reading the signal charge accumulated in the storage capacitor Cn,
CI, C2, C3, C4, etc. are read out in this order by the scanning pulse supplied from the Y-shift register 2 to the gate of Trhn, and the read signal charges are output to the outside via the buffer transistor Tro. Ru. The reset transistor TrR is connected from Y-shift register 2 to Trhn.
The signal charge is reset every period of the scanning pulse supplied to the gate of the gate.

Next, FIG. 2 is a block diagram illustrating a method for driving an infrared imaging device according to the present invention. Referring to FIGS. 1 and 2, as mentioned above, the signal charges corresponding to the incident infrared rays from the subject that are photoelectrically converted and accumulated in the infrared imaging element 3 are transferred from the X-shift register 1 to the transistor at regular intervals. The data is sequentially read out column by column in the row direction by a horizontal scanning pulse supplied to the gate of Trmn, and stored in the storage capacitor Cn.

Next, the accumulated signal charges are sequentially output pixel by pixel by a vertical scanning pulse supplied from the Y-shift register to the gate of the transistor Trhn.

A control signal generator 4 controls the X-shift register 1 and the Y-shift register 2 to generate scanning pulses. At this time, the control signal generator 4 supplies a reset pulse to the reset transistor TrR every time a signal for each pixel is output, resets the signal charge read out to the gate of the buffer transistor Tro by the transistor Trhn, and starts from the next pixel. Prepare for signal output.

Next, the storage circuit 5 is a means for storing a correction signal corresponding to the fixed pattern noise of the infrared image sensor 3, and when the signal charge is read out for each pixel, it outputs the stored correction signal at the same time. /A converter 6. The output of the D/A converter 6 is supplied to the drain of the reset transistor TrR. As mentioned above, the reset transistor TrR
performs an operation to reset the signal charge read out to the gate of the buffer transistor Tro for each pixel, and as is clear from the figure, this reset operation causes
Transistor T r R4 Trhn-4 Storage capacitor Cn → diode Dmn via transistor Trmn
The drain voltage of the TrR is supplied to the TrR. That is, the drain voltage of the transistor TrR is supplied as a bias voltage to each diode. Therefore, if the voltage supplied from the D/A converter 6 to the drain of the reset transistor TrR is controlled for each pixel so as to correct the variations in sensitivity and dark current of each diode Dmn, the sensitivity and dark current will be reduced. An output signal with reduced variation can be obtained.

The signal processing circuit 7 is a processing circuit for completely eliminating remaining variations from the output signal in which the variations in sensitivity and dark current have been reduced. FIG. 3 shows its block diagram. The output of the infrared image sensor circuit 8 having the configuration shown in FIG. 2 is A
The data is digitized by the /D converter 9 and taken into the storage circuit 10. The captured signal is used in an arithmetic circuit 11 to calculate the amount of correction required for variation correction, and then stored in the memory circuit 10 again.

The correction circuit 12 subtracts the correction amount from the output of the A/D converter to obtain a uniform image signal. At this time, the output of the infrared image sensor is obtained by the means described in Fig. 2, so that an output signal with reduced variations in sensitivity and dark current is obtained, so the signal processing after the A/D converter is less than before.
Signal processing with a resolution of 2 to 14 bits or less is sufficient.

As is clear from the above description, in this embodiment, the bias voltage applied to the detector is controlled for each pixel.

In this configuration, the sensitivity of each pixel.

Dark current can be corrected individually and fixed pattern noise can be significantly reduced.

In the above description, an example in which the infrared detectors are arranged in a two-dimensional array has been described, but it is clear from the detailed explanation that an infrared imaging device can be realized using the same construction method even in the case of a -dimensional array.

Since the configuration in this case is obvious to those skilled in the art, detailed explanation will be omitted.

〔Effect of the invention〕

As described above, the present invention has the effect of realizing an infrared imaging device that can significantly reduce fixed pattern noise.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the infrared imaging device of the present invention, Fig. 2 is a block diagram showing its driving method, Fig. 3 is a block diagram showing a signal processing circuit for fixed pattern noise removal, and Fig. 4 is a block diagram showing the conventional infrared imaging device. FIG. 2 is a schematic configuration diagram showing the configuration of an infrared imaging device. 1.13...X-shift register 3...Infrared imaging device 5.10...Storage circuit 7...Signal processing circuit 9...A/D converter 12...Correction circuit 2.14 ... Y-shift register 4 ... Control signal generator 6 ... D/A converter 8 ... Infrared image sensor circuit 11 ... Arithmetic circuit

Claims (2)

[Claims] (1) A group of multiple detectors arranged in one or two dimensions that receive incident infrared rays and photoelectrically convert them, and a signal charge corresponding to the incident infrared rays that is photoelectrically converted and accumulated by this detector group at a certain period. In the infrared imaging device, the infrared imaging device is equipped with a scanning means for sequentially scanning and reading out each detector, including means for applying a bias voltage to each detector individually after outputting a signal from each detector of the detector group. Characteristic infrared imaging device. (2) The infrared rays incident on a plurality of detector groups arranged one-dimensionally or two-dimensionally are photoelectrically converted and accumulated, and the accumulated signal charges corresponding to the incident infrared rays are sequentially scanned at regular intervals. After reading out and outputting the signals from the individual detectors,
1. A method for driving an infrared imaging device, comprising applying a bias voltage to each detector and controlling the applied bias voltage for each detector.