JPH08204163A - Infrared rays detector - Google Patents

Abstract

PURPOSE: To provide an output circuit which can be simply constituted by increasing the charge amount which can be treated by a picture element of a two dimensional infrared rays detector. CONSTITUTION: Charge input (q) is inputted to an integrator 2 via a switch 1. Charge accumulated in a capacitance 22 of the integrator 2 is inputted to a comparator 5 and compared with a specified potential, and a judgment signal is obtained. The judgment signal is inputted to a control circuit 4, and discharging accumulated charge is discharged by the switch. A counter 6 counts the number of times of discharge, and the counted value is made the output of a detector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detector, and more particularly to an output circuit of a two-dimensional infrared detector having detector elements arranged in a matrix.

[0002]

2. Description of the Related Art An output circuit generally used in a conventional two-dimensional infrared detector is shown in FIG. In the figure, the charge q generated in each pixel is input to the input terminal 10, passes through the output gate (OG) 12, and then is reset gate (RG) 14.
The charge capacity (CFJ) 13 set to a predetermined reset voltage (VR) 17 is opened and closed for a predetermined time.

FIG. 4 shows a time chart of the control voltage (φR) 15 of the reset gate (RG) 14 and the output voltage of the charge capacity (CFJ) 13 in this case. In the figure, the control voltage (φR) 15 is at a high level for a predetermined reset time (T _RS ) every one pixel read time (T _R ) cycle. As a result, the reset gate (RG) 14 is turned on for the time T _RS , and the reset voltage (VR) 17 is applied to the charge capacitance (CFJ) 13.

After the charge capacity (CFJ) 13 is charged to the reset voltage (VR) during the reset time (T _RS ), the reset gate (RG) 14 is turned off and the charge input (q) is changed. Is entered. The electric charge that is input gives a negative electric potential, so that the electric potential decreases. However, immediately after the reset time (T _RS ), the potential is constant (field through voltage) VF because it is affected by the stray capacitance.

The voltage change from the field through voltage VF to the minimum value of the potential is indicated by ΔV _S. This voltage change ΔV _S has a different value for each pixel read time.

This potential change ΔV _S , after passing through the amplifier circuit 16, is output from the output terminal 18 to the outside.

Regarding the output circuit of the infrared detector as described above, for example, Hiroo Takemura, "Design of VTR with ultra-small camera", Trikep (August 26, 1991)
Issued in detail).

[0008]

Since the output circuit of this conventional two-dimensional infrared detector has a structure as shown in FIG. 3, the amount of charge that can be handled by one pixel is limited by the capacity of the charge capacity 13. Therefore, there is a problem that it is difficult to select an appropriate capacity to receive the data. Further, since the capacity of the charge capacity 13 is limited by the charge read rate, physical size, semiconductor manufacturing process, etc., when a large amount of charge is to be handled, it may be stored outside the infrared detector depending on the charge read method. There is also a problem that it is necessary to provide a charge capacity.

[0009]

An infrared detector according to the present invention receives an electric charge generated in any one pixel of the infrared detector, accumulates the amount of electric charge, and charges an electric charge capacity of the integrating unit. The discharging means that discharges the discharged electric charge when it reaches the maximum capacity, the charging means that further charges the integrating means after the discharging, the means that repeats the discharging means and the charging means, and the number of times of charging and discharging. And counting means for counting.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of an output circuit of a two-dimensional infrared detector according to the present invention. A part of the signal charge (q) generated in one pixel among the pixels arranged in a matrix passes through the output gate (OG) 12 and the integrator 2 including the operational amplifier 23, the charge capacitance 22 and the switch 21. Is accumulated in the charge capacity 22 by In this case, the switch 1 is turned on and the switch 21 is turned off by the control signal 31 of the control circuit 4. Further, the voltage value of the constant voltage source 7 is set to be the same as the voltage value output from the integrator 2 when the signal charge q is filled up to the maximum capacity in the charge capacity 22. The comparator 5 outputs a determination signal to the control circuit 4 when the output of the integrator 2 becomes equal to the set voltage value when the capacity is charged to the maximum. Upon receiving this determination signal, the control circuit 4 immediately outputs the control signal 31 to turn on the switch 21. When the switch 21 is turned on, the charge accumulated in the charge capacity 22 is discharged, and when the discharge is completed, the switch 21 is turned off and the accumulation of the remaining charge is started again.

The operation described above is repeated based on the master clock 33 input to the control circuit 4. That is, the control circuit 4 repeats this operation for each pixel during the integration time of the pixel given by the pixel clock signal 34, and the number of times the signal is sent from the control circuit 4 to the switch 21 (that is, charging / discharging). The number of times) is counted by the counter 6 and output as a digital value of n (positive integer) bits. By the above operation, the charge amount generated in each pixel can be obtained as an n-bit digital value.

Next, the operation of each part in FIG. 1 will be described with reference to the drawings.

FIG. 2 is a diagram showing the waveform of each part of the output circuit of the infrared detector of FIG. In this figure, (a)
Is the M-th pixel given by the pixel clock 34 and (M
7 shows an output waveform of the integrator 2 in the +1) th pixel. Charging and discharging are repeated four times for the counting of the Mth pixel. As a result, four pulses are generated at the output of the comparator 5 as shown in (b).

The output signal 32 of the control circuit 4 is the counter 6
To (c), an n-bit parallel digital output is obtained. Note that (d) is the pixel clock 3
4 is a waveform showing 4 and each pixel is counted in synchronization with this clock.

The specific construction of each part in this figure is as follows. The structure of the comparator 5 can be, for example, a simple comparator using a known operational amplifier.

Further, the control circuit has a function of detecting the judgment signal of the comparator 5, outputting the control signal 31 based on the clock signal of the master clock 33 and outputting the output signal 22 to the counter 6. Have This function can be easily configured by a normal ethics gate. Further, it goes without saying that the CPU can be configured without using the logic gate.

[0018]

As described above, according to the present invention, since the number of times the charge capacity is charged and discharged is counted, the pixel generated charge amount is not limited by the capacity of the charge capacity formed in the infrared detector. Can be detected.

Further, since the output obtained by the present invention is a digital value, it also has an effect that the analog processing which has been necessary in the conventional image pickup apparatus becomes unnecessary. Further, since the pixel generated charge amount detection of the present invention can be configured by a digital processing circuit, there is an effect that miniaturization and low power consumption can be achieved by integration.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a time chart of each part of the block diagram shown in FIG.

FIG. 3 is a configuration diagram of a conventional output circuit.

FIG. 4 is a time chart of each part of the block diagram shown in FIG.

[Explanation of symbols]

 1 Output Gate 2 Integrator 3 Inverter 4 Control Circuit 5 Comparator 6 Counter 7 Reference Voltage 10 Charge Input Terminal 11 Bias Voltage 12 Output Gate 13 Charge Capacity (CFJ) 14 Reset Gate 15 Control Voltage (φR) 16 Amplification Circuit 17 Reset Voltage 18 output terminal 21 FET switch 22 charge capacity 23 operational amplifier 31 control signal 32 control circuit 4 output 33 master clock signal 34 pixel clock signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 5/33

Claims (2)

[Claims] 1. An integrating means for receiving an electric charge generated in any one pixel of an infrared detector and accumulating the electric charge amount, and a discharging means for discharging when an electric charge charged in a charge capacity of the integrating means reaches a maximum capacity. Infrared detection comprising: a charging means for charging the discharge means and the charging means after the discharging; a means for repeating the discharging means and the charging means; and a counting means for counting the number of times of charging / discharging. vessel. 2. An integration circuit for inputting the charge generated in any one pixel of the infrared detector and charging the charge amount to a charge capacity, and an output voltage of the integration circuit and a maximum capacity of the charge capacity. A comparator for comparing a predetermined reference voltage and outputting a judgment signal when they match each other, and a control signal for discharging the charge capacity to the integrating circuit when the judgment signal of the comparator is input, for charging / discharging An infrared detector, comprising: a control circuit that repeats the above steps; and a counter that inputs the output signal of the control circuit and counts the output signal.