JPH01183258A - Contact type image sensor - Google Patents

Abstract

PURPOSE:To remove the influence of inter wiring capacity and earth capacity to be given to a signal current by providing a means to ground the respective picture element of a sensor during the whole or only a part of a period while a read switch is off. CONSTITUTION:A shift register 38 which turns off each of reset switches 34-37 during the period while the read switches 27-30 turn on respectively, and turns on the respective reset switches 34-37 during the whole or a part of the period is provided. Namely, during the period while the respective read switches 27-30 are off, the reset switches 34-37 ground the sensor picture elements 4-15 through terminals 16-19. Accordingly, electric charge is not charged in the earth capacities 23-26, and besides, the inter wiring capacities 20-22 too come to be the earth capacity, and the influence upon the signal current of other sensor picture element is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contact type image sensor, and more particularly to a matrix-driven photoconductor type VI layer type image sensor with an improved S/N ratio. .

[Conventional technology]

Recently, dense layer image sensors have been increasingly used in facsimiles and 0Ca-+.

There are several types of contact type image sensors, but the matrix-driven photoconductive (photoconductor) M image sensor is superior in that it can reduce costs because it eliminates the need for an IC switch to drive the sensor. There is.

FIG. 4 is a block diagram of a conventional matrix-driven photoconductive image sensor, and FIG. 5 is a time chart thereof.

In Figures 4 and 5, the number of sensor leaves is 12. Although the matrix configuration is 3×4,
The principle is the same for sensors with 1000 pixels or more that are actually used.

In FIG. 4, drive pulses 41 to 43 shown in FIG. a1!5 are applied to terminals 1 to 3, respectively. Further, each of the successive output switches 27 to 30 is turned on when the pulses 44 to 47 issued from the shift register 31 are at the recitation level, and turned off when the pulses are at the low level. Therefore, the current flowing through each of the pixels 4 to 15 of the sensor is detected by the detection circuit 32 during periods 54 to 65, respectively, and an output signal is output to the terminal 33. In the valley elements 4 to 15 of the sensor, the isoelectricity 54 (
Since the reciprocal of the resistance changes, a signal current proportional to the amount of incident light flows to the detection circuit 32.

[Problem that the invention seeks to solve]

In the conventional matrix-driven photoconductive image sensor described above, there are a large number of readout switches 27 to 30 and shift registers 31, so they are often combined into ta or several ICs, and the terminals 16 to 19 and readout switches 27 to 30 are The wiring between the two is relatively long, over 10 cm.
In addition, the spacing between the wires is as small as 05111II or less, so the capacitances 20 to 22 between the wires are relatively large, and the signals ′:It flowing in each of the grooves 4 to 15 of the center t interfere with each other.
L. For example, the signal current flowing to pixel 7 is 7JW, and the signal current flowing to pixel 4 is
and 10 signal currents.

In addition, the ground planes t23 to t26 are also relatively large, and each pixel 4 to
During the period when the readout switches 27 to 30 connected to 15 are off, charges &C are photoelectrically applied to the ground voltage and 123 to 26.
Therefore, signal 11! flow is affected.

For example, the signal current flowing to the pixel 7 is
is detected by the detection circuit 32 together with the electric charges charged in the ground capacitance 24 from the terminals 1 to 3 through the pixels 7 to 9 during the period when the terminals 1 to 3 are turned off.

As described above, the conventional matrix-driven photoconductive area image sensor has the drawback that the signal current is affected by the inter-wiring capacitance and the ground capacitance, resulting in a deterioration of the S/N ratio.

The purpose of the present invention is to provide a means for grounding each pixel of the sensor only for all or part of the period when the lead-out switch is off, thereby eliminating the influence of the wiring and ground capacitance on the signal line. Therefore, it is an object of the present invention to provide an @st type image sensor that overcomes the above drawbacks.

[Means for solving problems]

The compact image sensor of the present invention has N x 14 i&! photoconductors arranged in a straight line whose resistance value changes depending on the amount of incident light. J tree, N wires connecting one end of each N i-string, and means for sequentially applying a pulse voltage of duty 1/N to each of the N wires in accordance with the order of the pixels in both sets. , M wires that successively connect the other end of the pixel to N pixels each, M readout switches whose ends are connected to the 1vI wires, and M readout switches. A detection circuit whose other end is focused and connected,
A'T
AF M wires and one readout switch, one end of which is connected to each coupling f5, and the other end of which is grounded. The reset switch in M1 is turned off and each of the M reset switches is turned on during all or part of other periods.

[Laughter example]

The present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention, and FIG. 2 is a time chart thereof. In No. 1!1, terminals 1 to 3.
Sensor element 4-15. Terminal 16~19° Wiring Questions and Answers 1i2
0-22. Amount of ground response 23-26. Read switch 27~
30. The system registers 31° to 65 are also the same as those shown in FIG.

Reset switches 34 to 37 are respectively) washout switch 2
The pulses 74 to 77 in FIG. 2 generated by the shift register 38 turn on when they are at high level, and turn off when they are at low level.

That is, the reset switches 34 to 37 close the terminals 16 to 19 while the read switches 27 to 30 are off.
The sensor IIi elements 4 to 15 are grounded through the ground. Therefore, the ground capacitors 23 to 26 are not charged with electric charge, and the center capacitors 20 to 22 also serve as ground capacitances, and there is no influence of the signal current of the Senna pixel.

FIG. 3 is a time chart of the second embodiment of the present invention, which is the same as wt=usIH. When the pulses 84 to 87 generated from the shift register 38 are at a high level, the reset switches 34 to 37 are turned on, and the reset switches 34 to 37 are turned on during the period immediately before the one end output switches 27 to 30 are turned on.
9 to ground the sensor pixels 4 to 15. therefore,
The electric charge charged in the ground cover 23 to 26 is released just before the bladder outlet switches 27 to 30 are turned on, so the direct number N
It will not affect the L style.

[Effects of the Invention] As explained above, the present invention resets each pixel of the sensor by using a reset switch provided in parallel with the readout switch during all or part of the period when the exposure switch is off. This has the effect of eliminating the effects of inter-wiring capacitance and ground capacitance on the signal current rather than grounding.

[Brief explanation of the drawing]

Figure 1 α is a block diagram of an embodiment of the present invention, Figures 2 and 3 are time charts of 7, Figure 4 is a conventional block diagram, 45
The problem is the time chart. 4 to 15...Sensor pixels, 20 to 22...
・Capacitance between wires, 23~26 ・Old ・Capacity between lines, 27~
3o: wire removal switch, 32: detection circuit, 34-37: reset switch. Agent Patent Attorney Shinme Uchihara l Leap 4 Le t5:'in sun&f xy to Jo: nit sui? F 34-L37: Rizezu F Zwif Kaya 2 Revised Kaya 3 Figure/-17 No. 4 Figures 4 to 15: Ze〉Spell element 2θ to 22 Shakutobi - Salary amount 23 to 26. Penalty and longevity dispute 27~3θ: 5i1 switch

Claims (1)

[Claims] N×M pixels in which photoconductors whose resistance value changes depending on the amount of incident light are arranged in a straight line; N wirings connecting one end of each N pixel; means for sequentially applying a pulse voltage with a duty of 1/N to each of the wirings; M wirings that successively connect the other ends of the pixels to N pixels each; and one end connected to each of the M wirings. According to the order of the M readout switches, the detection circuit connected to the other ends of the M readout switches, and the pixels connected by the M wires,
means for sequentially turning on the readout switches for a period N times the pulse width of the pulse voltage, one end of which is connected to each coupling portion of the M wires and the M readout switches, and the other end is grounded. Each of the M reset switches is turned off during a period in which each of the M reset switches and the M readout switches are turned on, and each of the M reset switches is turned on during all or part of other periods. A close-contact image sensor characterized by comprising means.