JPS58191565A - Solid-state photoelectric conversion device - Google Patents

Abstract

PURPOSE:To eliminate an exclusive use IC, by turning on thin film transistors (TRs) in one block at the same time, detecting signals at a detection circuit being the same number as that of sensor elements in the block and scanning the result. CONSTITUTION:Thin film TRs 9 are provided in series with each photoelectric conversion element, and the TRs 9 are diviced into blocks 2 of the same number. Gates 10 of the TRs 9 in the same block are connected in common and sensors 8 are provided. Signals are led to a read circuit 3 comprising detection circuits being the same number as the elements of one block and a scanning circuit scanning the outputs through a wiring group connecting the TRs 9 corresponding to the blocks 2. Thus, the signal of the blocks in which the TR9 group is turned on is detected at the same time and read out through scanning.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact type image sensor used in a sensor portion of a document reading device such as a facsimile machine and a method for driving the same in order to reduce the size and cost of a document reading device such as a facsimile machine.

In recent years, in IfA reading devices such as facsimiles, with the aim of downsizing and lowering costs, there has been an active development of contact type image sensors that can correspond to the document surface in a ratio of 1 to 1K and can reduce the size of the optical system. Several types of image sensors have been devised as a method for realizing this, but these image sensors are broadly classified into storage type and non-storage type in terms of driving method.

The former accumulates the charge generated by light during one line scanning time in a charge conversion element such as a tidy odd diode, and takes this as a. Because the charge is accumulated, the signal ratio between dark and bright is also large, and it is especially sensitive to photoresponses. has the advantage of being fast. At present, products using a Saticon membrane or an amorphous silicon film have been announced. The latter simply utilizes one property of a photoconductor, which accumulates charge, and detects the intensity of light reflected on the document surface as a change in the resistance of the sensor element, and uses the secondary current of light. It has the disadvantage of slow photoresponse.

However, when it comes to driving the sensor, storage type image sensors currently have a major drawback in that they require a dedicated IC with the functions of a shift register and an analog switch array.

In one-valve storage type image sensors, it is necessary to have a rectifying contact on one side of the valve.Thus, it is possible to drive in matrix or box type, the number of switches is small, a dedicated IC is not required, and the cost is low. It is very advantageous in this respect.As a way to solve the drawbacks of this storage type image sensor, it is conceivable to configure the part corresponding to this IC with thin film transistors built on the same substrate. This is because there are two reasons why this application has not been published so far. One is that the mobility of thin film transistors is generally very small compared to transistors made of single crystals, and the response speed is slow. Therefore, the sieve speed cannot be switched. The other point is that it is important to manufacture thin film transistors uniformly over a large area with good reproducibility and in an integrated manner. Another secondary reason is that if a relatively high-speed thin film transistor array and a contact image sensor array are fabricated on the same substrate, the process becomes extremely complicated.

The purpose of the present invention is to take into account the above circumstances, and to
Eliminate the above drawbacks and create an accumulative image safety “j-7”
The object of the present invention is to provide a high-speed solid-state charge conversion device that uses a wire and a thin film transistor array and does not require an IC.

According to the present invention, when an accumulation type image sensor array and a thin film transistor 7 array are configured as a pair on a substrate, and when the thin film transistor 7 array is divided into several layers and this is scanned, the thin film transistors in one block are is simultaneously KON, and the electric charge of the storage & store image No. 7 element corresponding to that professional, RI is detected by the same number of cells as the number of cells in the flow, for example, a capacitor JP block, etc. The circuit detects the signals at the same time, and then the switch is activated.

A solid-state photoelectric conversion device is obtained, which is characterized in that a signal is read out by scanning the photoelectric conversion device using a photodiode.

The following describes the basic structure of the present invention, and the principles and effects of the contact type image sensor and its driving method of the present invention while illustrating some embodiments.

FIGS. 1(a) and 1(b) show the basic structure of a contact type image sensor according to the present invention. In FIG. 1(,), 1 is a drive circuit that sequentially switches each of the processors (1) to (n), and 2 is one flow of storage type image sensor 7 rays and thin film transistor array. The specific configuration is as shown in FIG. 1(b)K. 170. As shown in the figure, the number of bits is nX 1y1 ml since there are n pairs of sensor elements and transistor elements of ml·1. Reference numeral 3 designates a detection circuit for the m-axis, a scanning circuit for fixing the detection circuit, and, if necessary, an amplifier, a buffer, or an integrator added to the scanning path. Reference numeral 4 is a power supply for applying voltage to the sensor, but there is also a method of using this power supply as a ground and using this power supply for the reading circuit 3. 5 is a wiring group from the common gate of the thin film transistor of each flow to the driver circuit l, and 6 is a wiring group of each flow.

Connect the signal lines from the respective corresponding bits of each block, that is, the respective j bits of each block, to a common wiring group, button, and 7 to the reading circuit.
Figure 8 shows the equivalent circuit of the storage-refining image sensor. ing. S(i,j)Fii Pro, Rino'th sensor element is shown.

9 is a thin film transistor, and as shown in the figure, the sensor l
One circuit is connected to each bit, and the gates are connected in common to the driver circuit I through a wiring I OK. Wiring group 5 is a group of 0 wires lO.
It is. Further, 11 is a wiring group leading to the reading circuit 3, and 6 is a wiring group in which the wirings coming out from bits 8(1,j) to S(n,j) are common.

The outline of the operation is as follows. Assume that scanning is being performed and the signal cage side is placed on the sensor. To explain from the 1st bit, the 91st drive circuit l
As a result, the thin film transistor array of the flock 1 is turned on, and the 7 signal portions of the sensor elements from the 1st bit to the mth bit to the The switch array inside performs sequential switching from 1 bit to m bits and reads the signal.

At this time, there are several possible timings for turning off the thin film transistor 7 lay depending on where the reading time of the reading circuit falls, but at least it must be completely turned off by the time the thin film transistor 7 lay of the next block is switched. No. Finally, the charge remaining in the reading circuit is completely reset, and the next step is to replace the thin film transistor 7 layer.

Enter Nang. Hereafter, this operation will be described as n70. Continue until

In this way, by switching the thin film transistor only once and moving the charge just once, it is possible to effectively increase the scanning speed even if a thin film transistor with a slow response speed is used. . For example, if a thin film transistor with a response speed of 100 μ is used as a switch, and the scanning speed of 1 bit in the reading circuit is 5 μ, then the scanning speed of the read circuit is 200 μ9eC to 250 μ( 5) becomes □,
If this is adjusted to a uniform speed, it will be 20 to 25 μ per l bi and g.
This means that switching is performed at the speed of paper.

Since the thin film transistor requires 200 μm for ON-OFF, in this case, scanning can be performed approximately 10 times faster than scanning using a single trap thin film transistor.

In addition, since a thin film transistor with a slow response speed can be used in this way, if the speed ratio of the reading circuit and the number of elements m are increased, it can be used satisfactorily even if the characteristics of the thin film transistor vary. Therefore, the yield improves. Therefore, it becomes possible to compensate for all the drawbacks of the thin film transistor mentioned above.

Next, the operation will be described in detail while illustrating two embodiments of the detection circuit and the scanning circuit of the reading circuit and a switching timing chart.

Figure 2 (a), (b), and (c) show the reading circuit 03.
There are no fruitful examples. In FIG. 2(,), 12 indicates a resettable integrator, and 13 indicates a switching FIT. Also (11, +2>,...&n)
corresponds to the lth to mVth signal lines of each pro. In this embodiment, the detection circuit is an integrator, and the integrator integrates the flaw signal on the storage St type image sensor, converts the signal into voltage, and sequentially switches the switching FETs to read the signal. . If the integrator is then reset, the reading circuit returns to its initial state.

#2 In figure (b), 14 is a charge storage capacitor, 1
5 is FBT for reset, 16#i switch, FET for Nang
, 17 is an integrator or an amplifier such as 77, and 1
When 7 is an integrator, all the electric power accumulated in the charge storage capacitor flows into the integrator, so the reset FETFi 15 is not necessary.

In Fig. 2(c), 18 is a detection circuit, which consists of a first-stage detector consisting of a readout resistor and preamplifier Fi19, a sample hold circuit 20, a comparator 21, and a TTL or CMO8 level converter 22. . Further, 23 is a scanning circuit consisting of a shift register of a parallel/serial converter. In this embodiment, the signal is binarized into a white level and a black level by the detection circuit, and this binarized signal is scanned by a shift register.

Furthermore, depending on the configuration of the subsequent signal processing system, it is also possible to process the L and R signals as they are without performing scanning using a shift register.

Figure 3 (,) shows the timing of the switching pulses in the embodiments of Figures 2 (a) and (b).
.

(b), Fig. 3 ta> shows the case where 17 is a buffer in the embodiment of Fig. 2 (,) and the embodiment of Fig. 2 (b), and the operation is as described above. . Also, Figure 3 (b
) is the case where 17 is an integrator in the configuration shown in Figure 2(b),
The lyse shown here is the lyse of the Tobalsian integrator 17.

enters the circuit. The difference in operation is that since the integrator is IIJ, it is necessary to reset the integrator every bit and bit, and as mentioned above, the reset FF1T is not required and all bits are not reset at the same time. Basically, they are almost the same.

Next, FIG. 4 (!11, (b) shows an example of the switching timing of the thin film transistor array and the operation timing of the reading circuit, and the section (B) in the figure is the section (!
It corresponds to B). In Figure 4, (C), (1
) is 71, the output from the driving circuit is 270. The amount is shown below. (d) , (
f) is the response waveform of the thin film transistor.

As is clear from the diagram, K14 diagram (1) sequentially reads the signal electric images transferred to the reading circuit after the thin film transistor is completely turned OFF, and ME4 diagram (b) shows that the #4 membrane trunk transistor is turned ON. When the process is almost completed, start reading the signal. m person is thin film transistor switch/chi/
This is the timing when the noise associated with the game is so loud that it cannot be ignored by Hakugo Roshi.

This is a case where the Is sound can be ignored. The main sources of this noise are the feedthrough of switching pulses through the capacitance between the gate and source or drain of the thin film transistor, and the
111, and by using a thin film transistor t-0FF as shown in FIG. 4(a), a contradictory W sound can be generated and canceled. By performing the cystectomy operation, a signal with reduced noise can be obtained. However, if this kind of noise is small enough, the timing shown in #4 (b), which can increase the scanning speed of the second and second steps, is better.Iwa, these two examples are all about timing. That's not to say.

What I would like to emphasize here is that this method is essentially different from the signal readout method using a matrix or box type drive circuit as shown in FIG. 5 of the solid-state photoelectric conversion device of the present invention. The difference between Figure #15 and Figure 1 (Hata) is in the part 24.25, which is a resistor and video 7 block that are generally used for signal readout of FBT25Fili multilayer image sensors for switching that can be switched. A readout circuit such as a readout circuit or an integrator. Kf8 like this! Although they are very similar in terms of L circuits, this circuit's field is quite similar, and even if switching pulses are sent from P rough circuit L to the gates of P and R thin film transistors, as long as the 24 SW and NNG FETs are not ONL. Although there is an electric field between the source and drain of a thin film transistor, there is actually no electric field in the thin film transistor i;jONl. The thin film transistor starts to turn on after the FIT for switch and switch connected to the thin film transistor turns on. is ON L, O
It takes time to turn the FF, and the operating speed does not increase at all.

Next, an example of the storage image seven sensor elements and thin film transistors is shown in Figure 6. This example is a sensor,
Both transistors are made of amorphous silicon 't'', 26 is a glass substrate, 27 is 8.0. or IT
The transparent common electrode 28 is a continuous part made of Cr ff metal and determines the length of the sensor opening in the sub-scanning direction. 29 is an amorphous silicon film with a thickness of 2 to 3 μm made by doping 8i, N, film 30 with horn or oxygen cape to a thickness of about 100 to 200 A, and 31 is a film doped with poro/N. It is a pWi amorphous silylon wire with a thickness of 02~(L4μm, 29.31 is a layer that acts as a charge injection blocker, and J-130 is a layer that generates 100% by light, and 29~31 is an accumulation layer image. 7/. 32 is A1 electric which serves as the upper bending electric machine of the sensor and the drain electrode of the thin film transistor, 3311A1 O'/
-,
5 μm f) 8 i B N4 film, which is a critical layer for thin film transistors. It is the gate electrode of 36FiA1 and 3
3 to 36 are influenced by thin film transistors. 37 is a light-shielding film that prevents light from entering the thin film transistor.If the structure of the device allows light to enter from the OI1m side where the element is located, it must be placed above the thin film transistor.This was used for the thin film transistor. This is because amorphous silicon has photoconductivity. This is the light from the 38#i original.

As in this embodiment, the sensor section and the thin film transistor section of the solid-state photoelectric conversion device of the present invention can be formed on the same substrate with the same material. It can also form productivity,
It is possible to manufacture it reliably and at low cost. Other examples include Sachicon and Cd as storage type image sensors.
Thin film transistors using Cd8 or Cd8, etc. are the same as thin film transistors (thin film transistors using Cd8, Cd8s+, etc. as materials, polycrystalline 8i formed by evaporation of Sl, or amorphous silicon by laser 7 anneal to polycrystallize it. It is also possible to use the same material as the material.

As described above, according to the present invention, it is possible to obtain a solid-state photoelectric conversion device using a highly sensitive and high-speed integrated image sensor and having a drive circuit that does not require a dedicated 1C. It is useful for hut making and low cost.

[Brief explanation of the drawing]

@ l IW (ml, (b) is the basic configuration of the cling-type image sensor of the present invention, Fig. 2 (a), (b),
(C1 shows two examples of one part of the reading circuit section, FIGS. 3(a) and 3(b) are timing charts of switching in the reading circuit, and FIGS. 4(m) and (bl are professional and , an example of switching between NANG and reading circuit, and timing of NANG, Fig. 5 shows an image sensor with matori and kumeya drive circuits, and Fig. 6 shows an example of an integrated image sensor and a thin film transistor. 1... Boo, ri drive circuit, 2... L bu, ri, 3-U* of storage type image sensor and thin film transistor array.
[o+il, 4-Iden 8.5\, Wiring Yu, 691. Common wiring group, 7... common t&, 8-- storage type image sensor element, 9-- thin film transistor, 10... common gate, 11... wiring group, 12... integrator, 13.16
... FIT for switching, 14... Capacitor for signal charge storage, 15... - FET for reset, 17...
・Buffer or integrator, 18...-detection circuit, 19...
・First stage detection circuit, 20・-Sample hold circuit, 21
... Comparator, 22 ... Level converter, 23
-...Shift register, 24...Switching FE
T, 25...Detection circuit, 26...Glass substrate, 27
... common electrode, 28 ... light shielding film, 29 ... 8is
N+ film, 30... High resistance amorphous silicon film, 31...
・pfJ amorphous silicon film, 32...Top 1ml of the sensor that also serves as a drain electrode.Polar electrode 3...Source 1
! Pole, 34...Amorphous silicon film, 35...8i,
N, film, 36--gate, 37... light-shielding film, Mi 38..., signal light. Representative Patent Attorney Susumu Hakubi Figure 2 (and Figure 3 CQ) (b) '$4 Figure (θ)

Claims (1)

[Claims] 1. In a one-dimensional or two-dimensional image sensor that operates in an accumulation type, a thin film transistor is provided in series for each photoelectric conversion element, and the thin film transistors are divided into groups each having the same number of transistors, each of which is identical to the other. Equipped with a sensor section characterized in that the gates of the thin film transistors in the processor and the controller are shared, the elements of the controller and the controller can be connected to each other by a wiring group that connects the thin film transistors corresponding to each processor. The solid-state light is characterized in that it leads to a reading circuit consisting of the same number of detection circuits and a scanning circuit that scans the output thereof, simultaneously detects No. 46 of Fp and R when a group of thin film transistors are turned on, and scans and reads them. conversion device. 2. The photoelectric conversion element has a structure other than electrodes where light enters (from μm 1 to st, N, lli<, ^resistance amorphous silicon, p-type amorphous silicon film, claim 1). 3. The solid-state photoelectric conversion device according to claim 1, wherein the thin film transistor uses amorphous η silicon as a material and an 8i, N, or 8i0. film as an insulating film. 4. The solid-state photoelectric conversion device according to claim 1, wherein the detection circuit is a signal divider or a sample hold circuit, and the scanning circuit has a reading path that is an analog switch. 5. The output circuit receives a signal. A solid-state photoelectric conversion device according to claim 1, comprising a reading circuit including a binarization circuit and a scanning circuit of a shift rental type.