JPH01222582A - Photoelectric converter and its drive method - Google Patents

Abstract

PURPOSE:To reduce noise by providing a reset means to a control electrode area so as to apply difference processing to a sensor output and a sensor noise. CONSTITUTION:A reset means Qrs is provided to the control electrode area. Then after the control electrode area of the optical sensors Tr, Qrs is reset, a sensor noise is read just before the storage of a light stimulated carrier is started, a sensor output is read after the end of storage of light stimulated carrier so as to apply difference processing between the sensor noise and the sensor output. Thus, the noise reduction is attained. The sensor noise is read just before the start of storage of light stimulated carrier so as to increase the correlation of a drive noise further resulting in reducing further a steady noise between sensor cells.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoelectric conversion device intended to reduce noise and a method for driving the same.

[Prior Art] In a conventional photoelectric conversion device using a base accumulation type sensor that accumulates carriers generated by optical excitation in the base of a bipolar transistor, the following method is used to remove sensor noise. The drive system is adopted.

First, after resetting the sensor, an accumulation operation is performed to accumulate photoexcited carriers at the base, and then the sensor output including senna noise is read out and temporarily accumulated.Next, after resetting the sensor, the photoexcited carriers are accumulated at the base of the sensor. The component is read out as sensor noise, and differential processing is performed together with the sensor output to obtain a sensor signal from which sensor noise has been removed from the sensor output.

In this way, to obtain the sensor output and sensor noise,
Both the reset operation and the readout operation are performed, thereby increasing the correlation between the actually generated drive noise component and the read sensor noise (Japanese Patent Application No. 61-22962).
No. 5, Japanese Patent Application No. 123872-1982).

[Problem to be Solved by the Invention 1] However, the higher the correlation between drive noises, the higher the noise removal effect, and the fixed noise between each sensor cell can be reduced.

An object of the present invention is to provide a photoelectric conversion device and a method for driving the same, which achieve noise reduction by further increasing the correlation of drive noise.

[Means for Solving the Problems 1] A photoelectric conversion device according to the present invention includes a transistor that accumulates photoexcited carriers in a control electrode region, and a reset means that selectively sets the control electrode region to a constant potential or a floating state. In a photoelectric conversion device having a sensor, a first storage means for storing sensor output of the optical sensor, a second storage means for storing sensor noise of the optical sensor, and sensors stored in the first and second storage means. The present invention is characterized in that it includes a difference processing means for performing difference processing between the output and the sensor noise.

A method for driving a photoelectric conversion device according to the present invention is a method for driving a photoelectric conversion device having an optical sensor of a type that accumulates photoexcited carriers in a control electrode region of a transistor, and after resetting the control electrode region of the optical sensor, The present invention is characterized in that sensor noise is read out immediately before starting accumulation of photoexcited carriers, sensor output is read out after accumulation of photoexcited carriers is completed, and difference processing between the sensor noise and the sensor output is performed.

[Function] The optical sensor provided with a reset means in the control electrode area has the following features:
Although it is highly sensitive and produces little noise by itself, significant noise reduction can be achieved by performing differential processing between the sensor output and sensor noise.

Furthermore, by reading out sensor noise immediately before the start of accumulation of photoexcited carriers, the correlation of drive noise can be further improved, and as a result, fixed noise between sensor cells can be further reduced.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1(A) is a partial circuit diagram of a line sensor which is an embodiment of the photoelectric conversion device according to the present invention, and FIG.
) is a signal waveform diagram for explaining the operation.

In the same figure (A), a reset transistor Qra is equivalently connected to the base of the bipolar transistor 'r', and a positive voltage V, (here, 0.6V) is applied. A reset pulse φ is input to the gate electrode.A photosensor is configured by the transistors Tr and Q□, and photoexcited carriers (here, holes) are accumulated at the base of the transistor Tr.

A constant positive voltage is applied to the collector electrode of the transistor Tr, and the emitter electrode is connected to the transistor Q2, and a constant voltage Vv, (here, ground potential) is applied. A pulse φvR is applied to the gate electrode of the transistor Q.

Further, the emitter electrode of the transistor Tr is connected to a storage capacitor CT and Cr2 through transistors QL I and Qtz, respectively, and is further connected to output lines NL and S through transistors QgI and QII2, respectively.
Connected to L.

The capacitors CT and Cr2 are each provided with a discharge transistor Q rh, which is turned on by a pulse φCR.
10FF control is performed. Also, transistor Q
A scanning pulse φ, , is input from the Silato register 1 to the gate electrodes of s + and Q 112.

Output lines SL and NL are connected to non-inverting and inverting input terminals of differential amplifier 2, respectively.

An embodiment of a method for driving an apparatus having such a configuration will be described with reference to FIG.

First, in period t1, pulses φVR1φT1 and φ
. 2 and turn on the transistors Q"r, Qt
+ and Qt2 are turned ON to remove unnecessary carriers from the emitter of the transistor Tr, unnecessary carriers from the capacitor CT, and CT2.

Next, in the second period t2, the pulse φ falls and the reset transistor Q□ is turned on, thereby removing unnecessary carriers remaining at the base of the optical sensor. As a result, the base potential V of the transistor "rra" is changed to the potential V
It is reset to BB, but at that time, the transistor Q r
When g is conductive, a noise component VKTC is generated and is added to the base potential.

After the period t2 has elapsed, the pulse φ rises, whereby the base potential v8 is swung by the potential v6 due to the ratio of the gate capacitance of the transistors Q and Ig to the parasitic capacitance of the base of the transistor Tr. That is, the reset operation during period t2 generates a Vgrc+v6 noise component.

Next, in the period Ta, the pulse φa rises and the transistor Qt+ is turned on. As a result, drive noise v1 is accumulated in the capacitor CT. Here, the drive noise v0 is expressed by the following equation.

V s = V 6 + V XTC + V n However,
(2) is feedback noise at the time of reading.

Subsequently, in a period t4, photoexcited carriers accumulate at the base of the transistor Tr, and the base potential Va rises.

After the period t4 has elapsed, in the period t5, the pulse φ7□ rises by -q, and the transistor Q12 is turned on. As a result, an output corresponding to the amount of carriers accumulated in the transistor Tr is transferred from the emitter to the capacitor CT2. As a result, the signal v accumulated in the capacitor CT is expressed by the following equation.

V s ” V I, + V nrc + V n +
V p However, V'R is feedback noise at the time of reading.

In this way, capacitors CT and CT each have noise V
, and signal v3 are accumulated, and the scanning pulse φH causes the transistors Qfil and Q to be accumulated. When turned ON, the signals are transferred to the output lines NL and SL, respectively, and subjected to differential processing by the differential amplifier 2.

Therefore, the output terminal of the differential amplifier 2 outputs a sensor signal v'g expressed by the following equation.

y′s: V B V N = V p + (
V'RV R) Thus, the swing component v6 and the noise VIITC when the transistor Q□ is turned on are completely eliminated. In addition, the feedback noise at the time of reading (v′□
-V*) is almost zero in the dark, and even in the light Vp＞
V′□−v,), which can be almost ignored.

Therefore, the sensor signal becomes V's''rVp, and the optical information can be faithfully exchanged into an electrical signal.

Similarly, the optical information from the optical sensors arranged in a line is photoelectrically converted, and the scanning pulse φ□ from the shift register l
The signals are sequentially output from the differential amplifier 2 at the timing of .

FIG. 2 is a timing chart showing another embodiment of the method for driving a photoelectric conversion device according to the present invention.

In this embodiment, the pulse φ performed in the embodiment described in -A.

Nyorori Set (hereinafter referred to as "Complete Refresh")
After that, transient refresh is performed using the transistor operation of the transistor Tr.

First, during the period L', the transistor Q rh is turned on by the pulse φC□, and the capacitors C'1 and C
'Clear 2.

Subsequently, in a period t″1, the transistor Q1 is turned on by the pulse φVR, and the emitter of the transistor Tr is cleared.

In the period t2, the pulse φ is lowered to turn on the reset transistor Q□ to reset the base and fix the base potential to V811 (complete refresh). This potential V all may be any potential that provides a forward bias to the sensor emitter. Here, V, , = 1.5 V.

Subsequently, in period t'2, the transistor Qr is turned on by the pulse φVH, and the emitter is set to the potential VvR(
Here, transient refresh is performed at 0.5V).
As a result, the base potential Va further decreases. At that time, the noise component (v6+vKTc) and the noise VTI+ generated during transient refresh rapidly decrease,
(v6 + VIITc)' and VOR, respectively.

In period t3, pulse φ7. Transistor Q
When tr is ON, the sensor noise V is expressed by the following formula:
'N capacitor CT.

V'N = (V a +VKTCl' +VTR+
VR Next, after the accumulation operation of photoexcited carriers, the period L
4, the pulse φT2 causes the transistor Q t
2 is turned ON, and the signal V'3 containing the accumulated voltage Vp is transferred to the capacitor (2 T2 - V's = V p +y''
N, and V″+ = (va +VKTC) ′+
V; R+V'R.

The sensor output V'g accumulated in the capacitors CTl and CTz in this way and the sensor noise V'N are differentially processed by the differential amplifier 2 to obtain a sensor signal from which drive noise has been removed.

In the above embodiments, driving noise was removed within the sensor, but the memory means may be provided separately outside the sensor.

Similar noise processing can be performed in area sensors by providing memory means outside the sensor.

[Effects of the Invention] As explained in detail above, the photoelectric conversion device according to the present invention has the following features:
Although it is highly sensitive and produces little noise by itself, further noise reduction can be achieved by performing differential processing between the sensor output and sensor noise.

In addition, in the driving method according to the present invention, by reading out the sensor noise immediately before the accumulation of photoexcited carriers starts, it is possible to further improve the correlation of the driving noise, and as a result, the fixed noise between sensor cells can be further reduced. can.

[Brief explanation of the drawing]

FIG. 1(A) is a partial circuit diagram of a line sensor which is an embodiment of the photoelectric conversion device according to the present invention, and FIG.
) is a signal waveform diagram for explaining one embodiment of the driving method, and FIG. 2 is a timing chart for explaining another embodiment of the method for driving a photoelectric conversion device according to the present invention. ■...Horizontal shift register. 2.-Differential amplifier. 'rr--Bipolar transistor of optical sensor, Qt
8...Reset transistor. Agent Patent Attorney Jo Yamashita 1st Sen (A)

Claims (2)

[Claims] (1) In a photoelectric conversion device having an optical sensor comprising a transistor that accumulates photoexcited carriers in a control electrode region and a reset means that selectively sets the control electrode region to a constant potential or a floating state, the sensor output of the optical sensor a first storage means for storing the sensor noise of the optical sensor; a second storage means for storing the sensor noise of the optical sensor; and a difference processing means for performing differential processing between the sensor output and the sensor noise stored in the first and second storage means. A photoelectric conversion device characterized in that: (2) In a method for driving a photoelectric conversion device having a photosensor that accumulates photoexcited carriers in a control electrode region of a transistor, after resetting the control electrode region of the photosensor, immediately before starting accumulation of photoexcited carriers, the sensor A method for driving a photoelectric conversion device, comprising reading out noise, reading out a sensor output after accumulation of photoexcited carriers, and performing differential processing between the sensor noise and the sensor output.