JPH0779330A - Close contact image sensor - Google Patents

Abstract

PURPOSE:To prevent deterioration in the S/N of a picture signal due to a field- through of a transistor (TR) transferring a picture signal in the close contact image sensor of the system extracting picture signals outputted from plural photoelectric conversion elements in the unit of a predetermined number separately for plural number of times and storing the picture signals sequentially. CONSTITUTION:The close contact image sensor provided with plural photoelectric conversion elements 11-11 to 11-mn, TRs 10-11 to 10mn blocked in the unit of a predetermined number of TRs to extract picture signals outputted from the elements in the unit of a predetermined number for plural number of times separately, a predetermined number of storage means 15-1 to 15-n storing the extracted picture signals and a means 3 applying a control signal sequentially to gates of the TRs of each block is provided with a dummy block (comprising the photoelectric conversion elements 11-01 to 11-0n and TRs 10-01 to 1-0n or the like) generating a field-through to cancel the field-through of an initial block for one scanning period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor for optically reading an image and converting it into an electric signal, and more particularly to a contact image sensor used for reading a document such as a facsimile.

[0002]

2. Description of the Related Art An example of this type of contact image sensor is shown in FIG. A large number of photoelectric conversion elements 11-11 to 11-1n, 11-21 to 11-2n, 1 on the sensor substrate 1.
1-m1 to 11-mn (hereinafter, 11-11 to 11-m
n) are arranged in a straight line and each photoelectric conversion element 11-11 to 11-11.
11-mn includes transistors 10-11 to 10-1n, 10-21 to 10-2n, which are FETs, respectively.
10-m1 to 10-mn (hereinafter, 10-11 to 10-m
n) the drain and the other end of which is grounded to the capacitor 12-
11-12-1n, 12-21-12-2n, 12-m
1 to 12-mn (hereinafter, 12-11 to 12-mn) are connected. Then, the transistors 10-11 to 10
The source of −mn is selectively read wirings 13-1 to 13-n
, And is connected to the image signal detection circuit 2 through this. Ground capacitances 15-1 to 15-n are connected to these read wirings 13-1 to 13-n, respectively. The gates of the transistors 10-11 to 10-mn are selectively connected to the gate wirings 14-1 to 14-m, and are connected to the shift register 31 provided in the drive circuit 3 through these. The DC power supply 32 provided in the drive circuit 3 is connected to the other ends of the photoelectric conversion elements 11-11 to 11-mn.

On the other hand, the image signal detection circuit 2 includes first to third analog switches SW-11 to SW-1n, S.
W-21 to SW-2n and SW-31 to SW-3n are provided and connected to the read wirings 13-1 to 13-n.
The first analog switches SW-11 to SW-1n are operated by the signal from the pulse circuit 20. Further, the second analog switches SW-21 to SW-2n are operated by the signal from the pulse circuit 21. Similarly, the third analog switches SW-31 to SW-3n are connected to the shift register 2
It is operated by the signal from 2. A DC power supply 24 is connected to the analog switches SW-11 to SW-1n. Capacitors 25-1 to 25-n are connected to the read wirings 13-1 to 13-n, and an amplifier 23 is connected to the terminal portions of the read wirings 13-1 to 13-n to output signals. Is configured to output.

The operation of the contact image sensor having such a structure will be described with reference to the time chart of FIG.
Photoelectric conversion elements 11-11 to 11- arranged on one straight line
A DC voltage is applied to mn from the DC power supply 31 of the drive circuit 3. Then, when light having a brightness corresponding to the light and shade of the document is incident, an electric signal having a level corresponding to the light is output as an image signal, and the image signal is respectively supplied to the capacitor 12-11.
~ 12-mn. On the other hand, the transistor 10-
11 to 10-mn include the shift register 31 of the drive circuit 3.
The gate control signal B shown in FIGS. 14A1 and 14A2 to 14A through the gate wirings 14-1 to 14-m, respectively.
1, B2 to BM are applied. Therefore, the transistors 10-11 to 10-mn are turned on for a certain period every scanning period according to the gate control signal, and the capacitor 1
The image signals accumulated in 2-11 to 12-mn are transferred to the ground capacitances 15-1 to 15-n of the read wirings 13-1 to 13-n. For example, the image signal of the capacitor 12-11 is t
In the period of 1, it is transferred to the ground capacity 15-1 and the capacitor 1
The image signal of 2-1n is transferred to the ground capacitance 15-n in the period of t1, the image signal of the capacitor 12-21 is transferred to the ground capacitance 15-1 in the period of t2, and the image signal of the capacitor 12-m1 is t2. Is transferred to the ground capacitance 15-1 during the period of, and the image signal of the capacitor 12-mn receives the ground capacitance of 1 during the period of t2.
5-n.

Analog switch SW of the image signal detection circuit 2
-21 to SW-2n are turned on by the control signal PH of FIG. 11 (b) applied from the pulse circuit 21,
The image signals transferred to the ground capacitances 15-1 to 15-n are transferred again to the capacitors 25-1 to 25-n, respectively.
For example, the image signal of the capacitor 12-11 is transferred to the capacitor 25-1 during the period of t4, and the image signal of the capacitor 12-1n
Image signal is transferred to the capacitor 25-n during the period t4, the image signal of the capacitor 12-21 is transferred to the capacitor 25-1 during the period t5, and the image signal of the capacitor 12-m1 is transferred to the capacitor 25-t during the period t6. -1, and the image signal of the capacitor 12-mn is transferred to the capacitor 25-n during the period of t6. The pulse circuit 21 is configured such that the periods of t4, t5, and t6 have a constant phase relationship with the periods of t1, t2, and t3, respectively.

Further, the analog-groove switches SW-11 to SW
-1n is applied from the pulse circuit 20 in FIG.
Control signal PR of the anaguro switch SW-21
~ SW-2n is turned on immediately after it is turned off, and the ground capacitances 15-1 to 15-n and the capacitors 12-11 to 12-mn are reset to the DC voltage applied from the DC power supply 24. To be done. For example, ground capacity 15
-1 to 15-n are all reset during the period when the control signal PR is turned on, and the capacitors 12-11 to 12-1n
Are reset during the period of t7, the capacitors 12-21 are reset during the period of t8, and the capacitors 12-m1 to 1
2-mn is reset during the period of t9.

Further, the analog-groove switches SW-31 to SW
-3n is turned on by the control signals P1 to PN of FIG. 11 (d1) to (dN) applied from the shift register 22, and the image signals transferred to the capacitors 25-1 to 25-n are The signals are sequentially output through the amplifier 23. For example, the image signal of the capacitor 12-11 is output during the period of t10, and the image signal of the capacitor 12-1n is t1.
The image signal of the capacitor 12-21 is output during the period of t12, the image signal of the capacitor 12-m1 is output during the period of t13, and the image signal of the capacitor 12-mn is output during the period of t14. To be done.

[0008]

In this conventional contact type image sensor, the gate control signals B1 to BM are applied to the image signal output by the feedthrough of the transistors 10-11 to 10-mn for transferring the image signal. Therefore, there is a problem that the S / N is deteriorated. That is, in the feedthroughs of the transistors 10-11 to 10-mn, the ground capacitances 15-1 to 15-n of the read wirings 13-1 to 13-n at the time t15 when the gate control signal B1 rises.
The feedthrough applied to the image signal accumulated in the image becomes a problem. With this feedthrough, the ground capacity is 15
The DC levels of the image signals stored in -1 to 15-n increase. Therefore, as shown in FIGS. 11E and 11F, the image signal output when the original is all black or all white is the photoelectric conversion elements 11-11 to 11-mn and the capacitor 12-.
In the period t19 corresponding to 11 to 12-mn, the DC level rises and the S / N deteriorates. Since the decrease of the DC level in the period t20 is the ineffective part of the image signal, it does not affect the S / N.

The feedthrough applied to the image signals stored in the capacitors 12-11 to 12-mn by the gate control signals B1 to BM is the capacitors 12-11 to 12-11.
Since it is uniformly applied to all 12-mn and is canceled by the rising and falling of each of the gate control signals B1 to BM, there is almost no change in the DC level of the image signal output, which is not a big problem. Also, ground capacity 1
Among the feedthroughs applied to the image signals stored in 5-1 to 15-n, the feedthrough occurring at t16 when the gate control signal B2 rises is canceled and the feedthrough caused by the fall of the gate control signal B1. Therefore, there is almost no change in the DC level of the image signal output, which is not a big problem. Further, the gate control signal B
The DC level of the image signals accumulated in the ground capacitances 15-1 to 15-n decreases due to the feedthrough occurring at t18 when M falls. However, the image signal of which the DC level is lowered is the photoelectric conversion elements 11-11 to 11-m.
It is an ineffective part which is not an effective part of the image signal accumulated in the capacitors 12-11 to 12-mn from n and does not cause a big problem even if the DC level is lowered. The purpose of the present invention is to
An object of the present invention is to provide a contact-type image sensor in which S / N deterioration due to transistor feedthrough is prevented.

[0010]

A contact image sensor of the present invention stores image signals from a plurality of photoelectric conversion elements arranged in a straight line in the same number of capacitors, and stores the stored image signals in a transistor. By this, a predetermined number of blocks are sequentially extracted in a plurality of times, and the extracted image signals are sequentially stored in an accumulating unit in a predetermined number of times, and the phases of the transistors are different for each block. In a contact-type image sensor that sequentially turns on according to a control signal to extract an image signal to a storage unit, a signal having a polarity opposite to that of a control signal applied to the transistor is applied to the storage unit in order to cancel field through in the transistor. The means to do is provided.
Further, there is provided means for matching the timing at which the block is changed from the ON state to the OFF state with the timing at which the block which is next changed from the OFF state to the ON state is changed from the OFF state to the ON state. Further, in the contact image sensor in which the first to third switches are provided and the image signals are taken out and the storage means is reset by these switches, the reset is performed in a part or all of a predetermined period. The means to do is provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. 1 is a circuit diagram of a first embodiment of the present invention. In FIG. 1, the same parts as those of the conventional configuration shown in FIG. In this embodiment, in addition to the structure of the conventional contact type image sensor shown in FIG. 10, photoelectric conversion elements 11-01 to 11-0n, capacitors 12-01 to 12-0n, transistors 10-01 to 1 are used.
0-0n is newly provided by the number of read wirings 13-1 to 13-n. That is, the transistors 10-01 to 10-0
The photoelectric conversion elements 11-01 to 11-0 are respectively connected to the drains of n.
n and capacitors 12-01 to 12-0n are connected, and read wirings 13-1 to 13-n are connected to the sources, respectively. Then, the gate control signal B0 is applied to the gates of the transistors 10-01 to 10-0n from the shift register 31A of the drive circuit 3 through the gate wiring 14-0.

The operation of this configuration will be described with reference to the time chart of FIG. The gate control signal B0 of FIG. 2 (a0)
Is applied to the gate. When the gate control signal B1 rises, which is a problem in the conventional contact image sensor, t1
The feedthrough of 5 is canceled with the feedthrough caused by the rise of the gate control signal B0. Therefore, as shown in FIGS. 2E and 2F, the DC level of the image signal output when the original is all black and all white is the same in the period t19 and other effective portions, and the S / N There is no deterioration.
The rise of the DC level in the period t22 of the image signal output due to the feedthrough at the rising t21 of the gate control signal B0 and the fall of the DC level in the period t20 of the image signal output due to the feedthrough at the falling t18 of the gate control signal BM , And both have no effect on the S / N because they are invalid portions of the image signal.

FIG. 3 is a circuit diagram of a second embodiment of the present invention. In this embodiment, the photoelectric conversion element 11 of the embodiment of FIG.
-01 to 11-0n, capacitors 12-01 to 12-0
n, instead of the transistors 10-01 to 10-0n,
The capacitors 16-1 to 16-n are read wirings 13-1 to 13-1.
3-n are newly provided. Capacitor 16-1
To 16-n are set to capacitance values corresponding to the amount of feedthrough of the transistors 10-11 to 10-mn, one terminal is connected to the read wirings 13-1 to 13-n, and the other terminal is connected to the other terminals. The gate control signal B0 is applied from the shift register 31A of the drive circuit 3 through the gate wiring 14-0.

According to this structure, as shown in the time chart of FIG. 4, the feedthrough at the time t15 when the gate control signal 1 rises is applied to the falling of the gate control signal B0 through the capacitors 16-1 to 16-n. 4E and 4F, the DC level of the image signal output becomes the same as that in the period 19 and other effective portions, and the S / N does not deteriorate. In addition, the output from the pulse circuit 20A of the image signal detection circuit 2 shown in FIG.
Control signal P of the switches SW-11 to SW-1n in (c)
R is turned on in the periods t23 and t24. Ground capacitance 15 due to feedthrough at t21 when the gate control signal B0 rises and at t18 when the gate control signal BM falls.
The fluctuations in the DC level of the image signals of -1 to 15-n occur during the period t2.
Since it is reset at 3 and t24, the DC level does not change during the image signal output periods t22 and t20.

FIG. 5 is a circuit diagram of a third embodiment of the present invention. In the conventional contact image sensor shown in FIG.
Gate wiring 14 is connected to the transistors 10-m1 to 10-mn.
1 through the shift register 91 of the drive circuit 3.
While the gate control signal BM of 1 (aM) is applied, the gate control signal BM is applied from the shift register 31B of the drive circuit 3 of FIG. 5 in this embodiment. According to this configuration, as shown in the time chart of FIG. 6, the gate control signal BM of FIG. 6 (aM) has a wider pulse width than the other gate control signals B1 to B (M-1), and the falling edge is low. Gate control signal B1 at t15 and t25
Coincides with the rise of. Therefore, when the gate control signal B1 rises t15 and t25, the ground capacitance 15-
The feedthrough applied to the image signals of 1 to 15-n is
The feedthrough applied at the fall of the gate control signal BM is canceled. Therefore, the ground capacity 15-1
The fluctuation of the DC level of the image signal of 15-n and the image signal output of FIGS. 6E and 6F does not occur.

In this embodiment, the image signals accumulated in the capacitors 12-m1 to 12-mn during the period of the pulse width difference t26 of the gate control signal BM of the conventional contact image sensor are switched during the period of t27 to t30. SW-11 to SW
−1n, and the transistors 10-m1 to 10-mn are reset. Therefore, during the period of t26, image signals are not accumulated in the capacitors 12-m1 to 12-mn, and
The signal level of the image signal when the document shown in (f) is completely white slightly decreases during the period t31.

7 to 9 show the fourth to sixth embodiments of the present invention.
6 is a time chart showing the operation of the embodiment, and since the circuit configuration of each embodiment is the same as the configuration of FIG. 5, it will be described with reference to FIG. However, a part of the configuration, that is, the shift register 31B of the drive circuit 3 and the pulse circuit 2 of the image signal detection circuit 2
Although each configuration of 0 and its operation are slightly different, the description will be given using the reference numerals shown in FIG. 5 for convenience.

In the fourth embodiment of the present invention shown in FIG.
In the conventional contact image sensor, the transistor 10-
The gate control signal B1 of FIG. 11 (a1) is applied from 11 to 10-1n from the shift register 31 of the drive circuit 3 to the shift register 31B of the drive circuit 3 through the gate wiring 14-1 in this embodiment. From Figure 7 (a1)
Gate control signal B1 is applied. The gate control signal B1 has a wider pulse width than the other gate control signals B2 to BM, and has a rising edge at t18, which coincides with the falling edge of the gate control signal BM. Therefore, the feedthrough applied to the image signals of the ground capacitances 15-1 to 15-n at the time t18 of the rise of the gate control signal B1 is canceled with the feedthrough applied at the fall of the gate control signal BM. Therefore, the DC levels of the image signals of the ground capacitances 15-1 to 15-n and the image signal outputs of FIGS. 7E and 7F do not change.

Further, the switches SW-11 to SW-1 of the image signal detecting circuit 2 during the period t32 of the pulse width of the gate control signal B1 of this embodiment and the conventional contact type image sensor.
n and SW-21 to SW-2n are pulse circuits 20 respectively.
7 and 21 are turned off by the control signals PH and PR shown in FIGS. 7B and 7C. Therefore,
Even if the transistors 10-11 to 10-1n are in the ON state during the period of t32, the capacitors 12-11 to 12-1
The image signal stored in n is not reset, and the signal level of the image signal when the original of FIG.

In the fifth embodiment of the present invention shown in FIG.
Gate control signals B1 to B of the conventional contact image sensor
The falling timing of (M-1) is the same as the rising timing of the next gate control signals B2 to BM and the switch S.
It almost coincided with the falling timing of the control signal PR of W-11 to SW-1. On the other hand, in this embodiment, the shift register 31B of the drive circuit 3 generates the signal shown in FIG.
The gate control signals B1 to BM of (a1) to (aM) are faster than those of the conventional contact image sensor, and the switch SW-
The control signals of 11 to SW-1n are in the ON state t33 to
It falls at the timing of t34.

The image signals of the ground capacitances 15-1 to 15-n include the gate control signals B1 to B of FIGS. 8 (a1) to 8 (aM).
The feedthrough is applied only at the rising time t15 to t17 of M. When the gate control signals B1 to BM fall t
The feedthrough applied to 33 to t34 is the capacitor 12- because the ground capacitances 15-1 to 15-n are reset by the switch SW-11 to SW-1n control signal PR in FIG. 8C even after the application. It is not applied to the image signals transferred from 11 to 12-mn. Therefore, FIG.
The DC level of the image signal outputs of (e) and (f) is higher in the effective portion t35 than in the ineffective portion, but is effective portion t35.
There is no deterioration in S / N because it rises uniformly within the interior.

In the sixth embodiment of the present invention shown in FIG.
From the shift register 31B of the drive circuit 3 shown in FIG.
The gate control signals B1 to BM of (aM) are applied. These gate control signals B1 to BM are shown in FIG.
Similarly to the gate control signals B1 to BM of (aM), t33 to
It falls at the timing of t34, and turns off during the period when the switch control signal PH in FIG. 9B is on.
9 (a1) for the image signals of the ground capacities 15-1 to 15-n.
~ (AM) gate control signals B1 to BM rise time t
The feedthroughs from 15 to t17 and t36 to t37 at the fall are applied, but the feedthrough at the rise t15 is canceled from the feedthrough at the fall t36, and the feedthrough at the rise t17 is the feed at the fall t37. Since it is canceled through, the DC level of the image signal does not change. Also, at the time of rising t38
.About.t39 and falling t33 to t34 are not applied to the image signal because the ground capacitances 15-1 to 15-n are reset by the switch control signal PR in FIG. 9C even after application. Therefore, the fluctuation of the DC level of the image signal output in FIGS. 9E and 9F does not occur.

[0023]

As described above, according to the present invention, the image signal from the photoelectric conversion element is applied to the transistor in a structure in which the image signal is sequentially taken out by the transistor in a plurality of blocks in a fixed number of blocks and sequentially stored in the storage means. Since a means for applying a signal having a polarity opposite to that of the control signal to the storage means is provided, there is an effect that field through in the transistor can be canceled and deterioration of S / N of the image signal output can be eliminated. In this case, a dummy block that generates a feedthrough for canceling the feedthrough of the first block of one scanning period, or a feedthrough of the last block of the one scanning period and a feedthrough of the first block of the next scanning period is used. By providing a means for canceling, a means for applying a uniform feedthrough in all blocks, or a means for canceling feedthrough in each of all blocks, it is possible to suitably eliminate the S / N deterioration.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of an image sensor of the present invention.

FIG. 2 is a time chart showing the operation of each part of the first embodiment.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a time chart showing the operation of each part of the second embodiment.

FIG. 5 is a circuit diagram of a third embodiment of the present invention.

FIG. 6 is a time chart showing the operation of each part of the third embodiment.

FIG. 7 is a time chart showing the operation of the fourth embodiment of the present invention.

FIG. 8 is a time chart showing the operation of the fifth embodiment of the present invention.

FIG. 9 is a time chart showing the operation of the sixth embodiment of the present invention.

FIG. 10 is a circuit diagram of an example of a conventional image sensor.

11 is a time chart showing the operation of each part of the image sensor of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor substrate 2 Image signal detection circuit 3 Driving circuit 10-01 to 10-mn Transistor 11-01 to 11-mn Photoelectric conversion element 12-01 to 12-mn Capacitor 13-1 to 13-n Read wiring 14-1 to 14-n Gate wiring 15-1 to 15-n Ground capacitance 20, 20A, 21 Pulse circuit 22 Shift register 31, 31A, 31B Shift register SW-11 to SW-1n switch SW-21 to SW-2n switch SW-31 ~ SW-3n switch

Claims (8)

[Claims] 1. A plurality of photoelectric conversion elements arranged in a straight line, capacitors of the same number as the photoelectric conversion elements in which image signals output from each of the photoelectric conversion elements are accumulated, and images accumulated in the capacitors. The same number of transistors as the capacitors are divided into a plurality of blocks by a certain number so that the signal is divided into a plurality of times by a certain number of units and sequentially extracted, and the extracted image signal is divided by the certain number of times into a plurality of times. A predetermined number of accumulating means for accumulating sequentially, the plurality of transistors being commonly applied to the gates of all the transistors in each block, and sequentially turned on according to control signals having different phases for each block. As a result, in the contact type image sensor in which the image signal is taken out to the accumulating unit, one scanning period among the plurality of blocks is performed. Then, at the timing when the block that is first changed from the off state to the on state is changed from the off state to the on state, a signal having a polarity opposite to the control signal applied to the gate of the transistor of the block is applied to the certain number of storage means. A contact type image sensor characterized by being applied. 2. A means for applying a signal of opposite polarity, together with a transistor of one block of the plurality of blocks, and a fixed number of transistors connected to the storage means, is first turned off in one scanning period. Means for applying a control signal to all the gates of the certain number of transistors at a timing when the block that can be changed from the on state to the on state is changed from the off state to the on state. The contact image sensor according to claim 1. 3. A means for applying signals of opposite polarities, and another constant number of capacitors respectively connected between said fixed number of storage means, and first turned off state during one scanning period. At the timing of changing the changed block from the OFF state to the ON state, a signal having the same voltage and the opposite polarity to the control signal applied to the gate of the transistor of each block is applied through the other constant capacitor. The contact type image sensor according to claim 1. 4. A plurality of photoelectric conversion elements arranged in a straight line, capacitors of the same number as the photoelectric conversion elements in which image signals output from each of the photoelectric conversion elements are accumulated, and images accumulated in the capacitors. The same number of transistors as the capacitors are divided into a plurality of blocks by a certain number so that the signal is divided into a plurality of times by a certain number of units and sequentially extracted, and the extracted image signal is divided by the certain number of times into a plurality of times. A predetermined number of accumulating means for accumulating sequentially, the plurality of transistors being commonly applied to the gates of all the transistors in each block, and sequentially turned on according to control signals having different phases for each block. In the contact-type image sensor in which the image signal is taken out to the storage means, each block of the plurality of blocks is in an ON state. The contact image sensor, wherein the timing at which the state is changed to the off state is matched with the timing at which the block that is subsequently changed from the off state to the on state is changed from the off state to the on state. 5. The contact-type image sensor according to claim 4, wherein each block of the plurality of blocks is sequentially turned on for the same period of time except for a block which is finally changed from an on state to an off state within one scanning period. 6. The contact image sensor according to claim 4, wherein each block of the plurality of blocks is sequentially turned on for the same time except for a block which is first turned on within one scanning period. 7. A plurality of photoelectric conversion elements arranged in a straight line, capacitors of the same number as the photoelectric conversion elements in which image signals output from each of the photoelectric conversion elements are accumulated, and images accumulated in the capacitors. The same number of transistors as the capacitors are divided into a plurality of blocks by a certain number so that the signal is divided into a plurality of times by a certain number of units and sequentially extracted, and the extracted image signal is divided by the certain number of times into a plurality of times. A certain number of accumulating means that are sequentially accumulated, a certain number of first switches from which the image signals accumulated in the accumulating means are simultaneously extracted, and a certain number of image signals extracted from the first switch are accumulated A second capacitor, and a predetermined number of second switches for resetting the first capacitor and the accumulating means to a predetermined voltage. The divided transistors are commonly applied to the gates of all the transistors in each block, and are sequentially turned on by a control signal having a different phase for each block. Of the image signal by the first switch and subsequent reset by the second switch, every time the plurality of transistors are sequentially turned on for each block. In the above, the timing at which each block of the plurality of blocks is changed from the ON state to the OFF state is earlier than the timing at which the block that is subsequently changed from the OFF state to the ON state is changed from the OFF state to the ON state, and each block is After being turned from the on state to the off state, the switch from the off state to the on state can be changed next. Tsu contact image sensor click, characterized in that the reset by a period of some or all the second switches period until changed from the OFF state to the ON state is performed. 8. The contact image sensor according to claim 7, wherein each of the blocks is turned off during a period in which an image signal is taken out by the first switch.