JPH09219823A - Contact area sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high definition robust against noise from the outside. SOLUTION: This sensor is provided with a light-receiving voltage generation circuit 4 capable of absorbing all the photoelectric charges outputted onto a signal line. As a photoelectric change is efficiently converted into a signal voltage by this circuit, the sensor becomes robust against the external noise. In addition, plural light-receiving voltage generation circuit 4 and a multiplexer 5 for a high-speed parallel-serial conversion circuit made from crystal silicon are added so as to obtain a two-dimensional image sensor of low noise and the low cost which forms a large screen being the strong point of a two-dimensional image sensor made from amorphous silicon or polisilicon and is provided with a high speed being the strong point of crystal silicon in addition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact area sensor for reading image information on a plane.

[0002]

2. Description of the Related Art FIG. 25 is a block diagram showing a configuration example of a conventional contact area sensor. In this figure, TF
In the T sensor unit 100, sensor cells forming each pixel are arranged in a two-dimensional matrix. Each sensor cell has a light receiving element S'xx that generates an electric charge according to the amount of received light, a capacitor Cxx that stores the electric charge generated in the light receiving element, and a switching element TRxx that reads the electric charge into a source line Sx. Composed of and.

The sub-scanning shift register 101 is shown in FIG.
As shown in, one gate line is sequentially selected from the plurality of gate lines Gx of the TFT sensor unit 100,
The switching element TRxx connected to the gate line is turned on. Further, the main scanning shift register 102
Is a plurality of source lines Sx of the TFT sensor unit 100.
One switching element is sequentially selected from the switching elements TFx connected to each of the above, and the switching element is turned on.

By the above-described operations of the sub-scanning shift register 101 and the main-scanning shift register 102, one sensor cell is sequentially selected from the sensor array of the TFT sensor section 100, and the electric charge generated in the sensor cell is output as a video signal. To be done.

[0005]

By the way, in the conventional contact area sensor shown in FIG. 25, when the charge amount Q of one sensor cell is selected and read out to the source line Sx, the signal voltage E is generated in the sensor cell. 1 of the voltage
/ 100 to decrease. The reason for this will be described below.
When the capacitance of the charge storage capacitor is Cs and the voltage generated in the charge storage capacitor is Vs, the charge amount Q of one sensor cell can be expressed by the following equation. Q = Cs × Vs When all the charge amount Q is transferred to the source line Sx,
Since the wiring capacitance Cx of the source line Sx is about 100 times the capacitance of the charge storage capacitor Cxx of each sensor cell, the signal voltage E generated in the source line Sx can be expressed by the following equation. E = Q / (Cs × 100) From the above, the signal voltage E can be expressed by the following equation using the capacitance Cs of the charge storage capacitor and the voltage Vs generated in the charge storage capacitor. E = (Cs × Vs) / (Cs × 100) Therefore, it can be seen that the relationship shown in the following equation holds. E = Vs / 100 That is, the charge amount Q of one sensor cell is selected,
When read to the source line Sx, the signal charge E is reduced to about 1/100 of the voltage generated in the sensor cell. As a result, in the conventional contact area sensor,
The signal voltage was buried in the leak noise of the drive pulse of my own, and the S / N ratio was very bad.

The present invention has been made under such a background, and an object of the present invention is to provide a contact area sensor capable of achieving high definition and strong against external noise.

[0007]

According to the first aspect of the present invention,
A plurality of light receiving elements that are arranged in a two-dimensional matrix in the X direction and the Y direction and that generate charges according to the amount of received light;
An emission control switching element that controls the emission of charges generated in each light receiving element and a charge emission terminal of each emission control switching element arranged in the X direction are commonly connected to form the charge transfer path. Multiple signal wires,
A plurality of scan wirings that connect the control terminals of the emission control switching elements arranged in the Y direction in common and form a path of a scan signal that controls the transfer of the charges, and the plurality of scan wirings sequentially to the scan wirings. A scan shift register that supplies a scan signal and is connected to each of the signal lines,
A plurality of light receiving voltage generating circuits that generate a light receiving voltage according to the amount of charges transferred on the signal wiring and hold the signal wiring at a reference potential or a bias potential determined by the reference potential, and light receiving voltage generation And a multiplexer for sequentially selecting one of the received light voltages generated by the circuit and transferring the selected received light voltage as a video signal.

According to a second aspect of the invention, in the contact area sensor according to the first aspect, the light receiving voltage generating circuit includes an operational amplifier, and the light receiving voltage is a signal output from an output terminal of the operational amplifier. , The signal wiring is connected to the negative input terminal of the operational amplifier, the positive input terminal of the operational amplifier is set to the reference potential, the charge between the output terminal and the negative input terminal of the operational amplifier, An absorption capacitor and a reset switching element that connects the output terminal and the negative input terminal when a reset pulse is input are connected in parallel.

According to a third aspect of the present invention, in the contact area sensor according to the second aspect, a first resistor is formed on a wiring connecting the reset switching element and the negative input terminal, A wiring connecting the reset switching element and the first resistor is set to the reference potential via a second resistor.

According to a fourth aspect of the invention, in the contact area sensor according to the third aspect, the output terminal of the operational amplifier is set to the reference potential via a fourth resistor, and the output of the operational amplifier is set. A third resistor is formed on a wire connecting the terminal and the fourth resistor, and among the terminals of the charge absorbing capacitor, the terminal connected to the output terminal side of the operational amplifier is the first resistor. 3 is connected to the midpoint between the fourth resistor and the fourth resistor, and among the terminals of the reset switching element, the terminal connected to the output terminal side of the operational amplifier is the output terminal and the third terminal.
It is characterized in that it is connected on a wiring connecting with the resistance of.

According to a fifth aspect of the present invention, in the contact area sensor according to the first aspect, the light receiving voltage generating circuit includes a first operational amplifier and a second operational amplifier, and the light receiving voltage is the first operational amplifier. It is a signal output from the output terminal of the operational amplifier, the output terminal of the first operational amplifier is connected to the positive input terminal of the second operational amplifier, and the signal wiring is the negative input terminal of the first operational amplifier. The positive input terminal of the first operational amplifier and the negative input terminal of the second operational amplifier are set to the reference potential, and the output terminal of the first operational amplifier and the first operational amplifier A charge absorbing capacitor is connected between the negative input terminal of the operational amplifier of
When a reset pulse is input, a reset switching element that connects the output terminal and the negative input terminal is connected in parallel between the output terminal of the operational amplifier and the negative input terminal of the first operational amplifier. A first resistor is formed on the wiring connecting the reset switching element and the negative input terminal of the first operational amplifier, and the wiring connecting the reset switching element and the first resistor. Is set to the reference potential via a second resistor.

According to a sixth aspect of the present invention, in the contact area sensor according to the first aspect, the light receiving voltage generating circuit includes an operational amplifier, and the light receiving voltage is a signal output from an output terminal of the operational amplifier. , The signal wiring is connected to the negative input terminal of the operational amplifier, the positive input terminal of the operational amplifier is set to a reference potential, and the light receiving voltage is provided between the output terminal and the negative input terminal of the operational amplifier. It is characterized in that a resistance element for feeding back is connected.

According to a seventh aspect of the present invention, in the contact area sensor according to the first aspect, the light receiving voltage generating circuit includes a transistor element, and a gate terminal (or a base terminal) of the transistor element is connected to the signal wiring. Connected to each other, the source terminal (or emitter terminal) of the transistor element is held at the reference potential, and the drain terminal and the gate terminal of the transistor element (or the collector terminal and the base terminal of the transistor element). Between the drain and the gate terminal of the transistor element (or between the collector terminal and the base terminal of the transistor element) when the reset pulse is input. The reset switching element is connected in parallel, and the signal wiring is Characterized in that it is held in the ground potential.

According to an eighth aspect of the present invention, in the contact area sensor according to any one of the first to seventh aspects, the signal wiring connecting the charge discharging terminal and the received voltage generating circuit has a protective resistance. It is characterized by having.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

§1. In the conventional technology, as shown in FIG. 25, in order to reduce the cost, a large number of switching elements TFx are arranged on a sensor substrate to form a read circuit. However, in the circuit configuration shown in this figure, when the charge amount Q of the sensor cell is selected and read to the source line Sx as described above, the output signal is reduced to about 1/100, and
A pulse for turning ON / OFF the switching element TFx flows into the output signal through the parasitic capacitance of the switching element TFx. The leak amount of this pulse is
It varies depending on the individual switching elements due to variations (individual differences) between the switching elements during manufacturing. Therefore, as fixed pattern noise, vertical (or horizontal) stripe-shaped light and dark appear on the read screen,
The screen quality is considerably degraded.

Since the switching element itself is made of amorphous silicon or polysilicon,
Many of these materials had crystal defects, and the signal charges were trapped in the defects, resulting in random noise. Further, in a switching element made of amorphous silicon or polysilicon, the switching speed is slow, which has been an obstacle to high-speed reading.

Therefore, the present invention provides a circuit capable of absorbing all the signal charges output on the signal wiring. As a result, the signal charges can be efficiently converted into the signal voltage and are less likely to be affected by noise. Further, according to the present invention, by using a plurality of light receiving voltage generating circuits,
High-speed reading is possible by reading the received light voltage in parallel and further using a multiplexer which is a parallel-serial conversion circuit. It is preferable that the light receiving element is formed on a transparent substrate using amorphous silicon or polysilicon. The light receiving voltage generating circuit can be formed using single crystal silicon, but can also be formed with amorphous silicon or polysilicon on the light transmitting substrate at the same time as the light receiving element. Since the multiplexer is required to have high speed, it is preferable to use single crystal silicon.

In the conventional two-dimensional sensor, the switching element is made of a thin film transistor, and the optical sensor element is made of p-type.
A photoconductive material such as a diode having an -i-n structure or cadmium selenium sulfide (CdS-Se) is used. Therefore, due to the difference in the structures of the two films, it was not possible to form them both at once, and they were formed individually. Therefore, the two-dimensional sensor requires a double manufacturing process, which is complicated and costly. For this reason,
In the present invention, the optical sensor element is a thin film phototransistor, and the switching elements have substantially the same structure, thereby simplifying the manufacturing process.

However, the thin film phototransistor has a p-
Compared with the photodiode having the i-n structure, the dark current is large, and if it takes a long time to read a signal, the dark current is accumulated at the time of accumulating photocharges, which may be converted into signal charges. In order to avoid this, high-speed reading is performed using the plurality of light-receiving voltage generating circuits and the multiplexer, and the above-mentioned problem is solved. As described above, by combining the thin film phototransistor, the plurality of light receiving voltage generating circuits and the multiplexer, it is possible to overcome the above-mentioned various drawbacks and provide an inexpensive two-dimensional image sensor.

§2. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration example of a contact area sensor according to the first embodiment of the present invention. The contact area sensor shown in this figure is roughly divided into a scan shift register 1, a TFT sensor section 2, and an external drive circuit 3.
It is composed of The scanning shift register 1 sequentially selects one gate line from a plurality of gate lines Gx and supplies a scanning signal to the selected gate line. As a result, among the switching elements (TFTs) on the TFT sensor unit 2, the switching element connected to the selected gate line is turned on.

On the TFT sensor portion 2 shown in FIG. 1, sensor cells forming each pixel are arranged in a two-dimensional matrix. Each sensor cell receives a light and generates a charge corresponding to the amount of the received light, a light receiving element Sxx, a capacitor Cxx for storing the charge generated in the light receiving element, and a switching element TRx for reading the charge to a source line Sx.
It consists of x and. Among them, as described above in “§1. Outline”, the light receiving element according to the present embodiment (light receiving element Sxx shown in FIG. 1) is the light receiving element according to the conventional technique (see FIG. 25).
The structure is different from the light receiving element S'xx) shown in FIG.

Further, FIG. 2 shows the contact area sensor shown in FIG. 1 in which the protective resistor PR is provided on the signal wiring connecting the charge discharging terminal of the TFT sensor section 2 and the received voltage generating circuit 4.
It is a circuit diagram which shows the example which inserted x. 1 and 2 have exactly the same circuit configuration except for the protection resistor PRx.
In FIG. 2, the protection resistor PRx is provided in the external drive circuit 3 when the gate line and the source line are short-circuited.
It is for protecting the operational amplifier inside and the drive power supply of the operational amplifier. The resistance value of the protection resistor PRx is sufficiently smaller than the resistance value when the transistor TRxx is in the ON state (that is, the ON resistance of the transistor TRxx). In the present embodiment, the protection resistance P
The resistance value of Rx is, for example, 100 [KΩ].

Next, details of the TFT sensor section 2 will be described. FIG. 3 is a plan view showing the structure of one sensor cell on the TFT sensor unit 2 shown in FIG. 1, and FIG.
FIG. 4 is a cross-sectional view of the TFT sensor unit 2 shown in FIG. 3, taken along the line AA ′ shown in FIG. The TFT sensor unit 2 is roughly divided into switching elements (SW-TFT: TR shown in FIG.
xx), a photocharge storage capacitor CS (corresponding to Cxx shown in FIG. 1), a TFT sensor (light receiving element: corresponding to Sxx shown in FIG. 1), and a TFT sensor section 2 provided below. It is composed of a window into which light output from a light source (backlight: not shown) is incident on a document. The size of one TFT sensor shown in the plan view of FIG. 3 is 5 [μm] wide.
X Length is 8 [μm]. Further, in the cross-sectional view of FIG. 4, black portions are metal layers, dot portions are amorphous silicon layers, and other unmarked portions are transparent insulating layers made of silicon nitride.

FIG. 5 is a graph showing the characteristics of the thin film transistors forming the TFT sensor shown in FIG. 3 or 4. In this figure, the horizontal axis represents the gate voltage Vg of the thin film transistor, and the vertical axis represents the drain current Id when a constant voltage (for example, 12 [V]) is applied between the drain and the source of the thin film transistor. . Further, in the figure, the thick line indicates 1000
Shows the case where [lux] light is applied, and the thin line (Dark)
Shows the case where the thin film transistor was not exposed to light. In addition, in the TFT sensor according to the present embodiment, the light output from the backlight does not reflect on the document and is transmitted to the TF.
A light shielding electrode is provided to prevent the T sensor from directly hitting. VB shown in FIG. 5 is the light-shielding electrode voltage applied to this light-shielding electrode.

From this figure, when the light-shielding electrode voltage VB has a sufficient value (in the example shown in this figure, the light-shielding electrode voltage VB =
In the case where the gate voltage Vg is negative, the value of the drain current Id is significantly different between the case where light is applied to the thin film transistor and the case where light is not applied thereto in the region where the gate voltage Vg is negative. That is, it is understood that the thin film transistor has high sensitivity to light in the region where the gate voltage Vg is negative.

The external drive circuit 3 shown in FIG. 1 comprises a plurality of received light voltage generation circuits 4 and one multiplexer 5. The multiplexer 5 selects one output signal from the output signals of the plurality of received light voltage generation circuits 4 and outputs the selected output signal as a video signal.

FIG. 6 is a circuit diagram of the received light voltage generation circuit 4 shown in FIG. As shown in this figure, the source line of the TFT sensor unit 2 is connected to the negative input terminal of the operational amplifier OP. The positive input terminal of the operational amplifier OP is connected to the reference potential (0 [V]). A charge absorbing capacitor CO and a reset switching element (transistor Tr) are provided between the output terminal and the negative input terminal of the operational amplifier OP.
And are connected in parallel.

Next, the operation of the contact area sensor having the above structure will be described. FIG. 7 is an explanatory diagram showing the operating principle of the contact area sensor according to the present embodiment. In addition, in this figure, for simplification of description, one sensor cell on the TFT sensor unit 2 and the light-receiving voltage generating circuit 4 connected to the sensor cell are taken out and illustrated. Further, since the gate electrode of the TFT sensor shown in this figure is fixedly connected to −15 [V], the TFT sensor is in an OFF state (a high resistance state between the source and drain) when the TFT sensor is not receiving light. Is. In this figure, since the positive input terminal of the operational amplifier is connected to GND (0 [V]), the potential of the negative input terminal (source line) also becomes 0 [V].

When the TFT sensor is exposed to light in such a state, the resistance between the source and the drain is lowered from the OFF state of the TFT sensor according to the intensity of the light, and the source
A current flows between the drains, and the voltage of the capacitor CS drops (photoelectric charges are stored in the capacitor CS). After the photocharge is accumulated in the capacitor CS, the switching TFT
The (SW-TFT) is turned on and the charges are read out on the source line. As a result, the voltage on the source line is 0 [V] (GND level) because of the read charges.
Go down.

When the voltage on the source line drops, the operational amplifier detects the voltage on the source line and raises the voltage at the output of the operational amplifier. When the voltage of the output of the operational amplifier rises, the voltage raises the voltage on the source line through the capacitor C0, and the potential of the source line returns to the original 0.
It returns to [V]. The increase in the output of the operational amplifier at this time becomes the received light voltage (photoelectric charge output voltage) and is output to the multiplexer (see FIG. 1). Since the voltage on the source line is always 0 [V] by the above-described operation, the charge of the pixel read immediately before this does not remain, and thus an afterimage does not remain.

FIG. 8 and FIG. 9 show two sensor cells as one.
It is explanatory drawing which shows the operation principle of a contact type area sensor when it connects in common to one source line. The operations of the sensor cells A and B and the received light voltage generation circuit 4 shown in these figures are the same as those described with reference to FIG. In FIG. 8A, the photocharge −Q generated in the sensor cell B is read. At the same time, in the sensor cell A, the photocharge −q is accumulated in the capacitor of the sensor cell A. Next, in FIG. 8B, the reset switching element Tr of the received light voltage generation circuit 4 is turned on to reset the charge accumulated in the charge absorbing capacitor CO. At the same time, sensor cell A continues to accumulate photocharge -q,
The sensor cell B also starts accumulating the photocharge -Q.

Next, in FIG. 9A, the photocharge -q generated in the sensor cell A is read. At the same time, in the sensor cell B, the photocharge -Q is stored in the capacitor of the sensor cell B. Then, in FIG. 9B, the reset switching element Tr of the light receiving voltage generating circuit 4 is turned on again to reset the charge accumulated in the charge absorbing capacitor CO. At the same time, the sensor cell B continues to accumulate the photocharge -Q, and the sensor cell A also starts accumulating the photocharge -q. The contact area sensor shown in FIGS. 8 and 9 repeats the above cycle. This is the end of the description of the operation of the contact area sensor having the above configuration.

§3. Second Embodiment Next, a second embodiment of the present invention will be described. The configuration example of the contact area sensor according to the present embodiment is the same as the circuit shown in FIG. 1 (the circuit of the first embodiment) except for the light receiving voltage generating circuit in the external drive circuit. In the first embodiment, the circuit shown in FIG. 6 is used as the received light voltage generation circuit, but in the present embodiment, the circuit shown in FIG. 10 is used instead of the circuit shown in FIG.

In the light receiving voltage generating circuit shown in FIG. 10, a resistor R2 is provided in order to reduce the appearance of the reset pulse on the input side of the operational amplifier OP via the parasitic capacitance Cd between the gate and drain of the transistor Tr. It was Since the impedance (resistance value against AC) ZC of the parasitic capacitance Cd can be calculated by ZC = 1 / (2πfCd) [Ω], for example, the harmonic frequency f of the reset pulse f = 100 [kHz], Cd = 0 .5
If [pF], then ZC = 1 / (2 × 3.14 × 100 × 10 3 × 0.5 × 1
0-12) = 3.2 [MΩ]. Therefore, the resistance value of the resistor R2 is set to 3.2 [MΩ].
Is less than 1/10, the amount of voltage leaking to the input side of the operational amplifier OP is 1/1 due to the resistance division of ZC and R2.
0 or less. Therefore, the resistance value of the resistor R2 is 1 [kΩ] to
100 [kΩ] is appropriate.

Next, how to determine the resistance value of the resistor R1 shown in FIG. 10 will be described. The potential difference between the two inputs of an ideal operational amplifier that is operating normally is 0 [V], but in reality,
There is an offset voltage of about 10 [mV]. While the signal is being read (approximately 60 μsec), the offset voltage causes a leakage current to flow through the resistors R 1 and R 2 to the GN.
Flow to D. Since this leak current appears at the output of the operational amplifier together with the signal current, it causes noise. For this reason, it is desirable that the resistance R1 be as high as possible. However, if the resistance is too high, the signal current accumulated in the capacitor C0 cannot be reset during a predetermined reset period. Therefore, the resistance value of the resistor R1 is 10
0 [kΩ] to 220 [MΩ] is appropriate.

§4. Third Embodiment Next, a third embodiment of the invention will be described. The configuration example of the contact area sensor according to the present embodiment is the same as the circuit shown in FIG. 1 (the circuit of the first embodiment) except for the light receiving voltage generating circuit in the external drive circuit. In the present embodiment, the circuit shown in FIG. 11 is used as the received light voltage generation circuit instead of the circuit shown in FIG.

In the light receiving voltage generating circuit shown in FIG. 11, since the signal charge storage (feedback) capacitor C0 is connected to the middle point of the resistors R3 and R4,
From the midpoint of 3 and the resistor R4, the same signal output as the signal output of the operational amplifier shown in FIG. 6 or 10 is obtained. In this figure, the operational amplifier operates to output a voltage higher by the division ratio of the resistors R3 and R4 in order to generate a voltage at the midpoint between the resistors R3 and R4. The input voltage of the multiplexer, A / D converter, etc. provided in the subsequent stage of this operational amplifier is about 1 [V], and the voltage for resetting is as high as possible (about 10 [V] in one example). Since the resistance value of R1 can be increased, such a circuit configuration is adopted. Therefore, both resistors R3 and R4
The resistance value can be selected in a wide range from 10 [Ω] to 1 [MΩ].

§5. Fourth Embodiment Next, a fourth embodiment of the present invention will be described. The configuration example of the contact area sensor according to the present embodiment is the same as the circuit shown in FIG. 1 (the circuit of the first embodiment) except for the light receiving voltage generating circuit in the external drive circuit. In this embodiment, the circuit shown in FIG. 12 is used as the received light voltage generation circuit instead of the circuit shown in FIG.

FIG. 12 is a circuit diagram showing an example of the received light voltage generating circuit according to the present embodiment. If the voltage for resetting the capacitor C0 is as high as possible, the resistance value of the resistor R1 can be made high, and the leak current which becomes noise can be reduced. Therefore, this figure shows an example using a comparator, which is more effective than the voltage adjustment by the resistance division shown in FIG. The comparator OP2 operates only when the signal charge storage (feedback) capacitor C0 is reset. When the signal is read, if the output of the operational amplifier OP is a little, the comparator OP
2 detects that the potential of the output of the operational amplifier OP deviates from the GND potential, and raises the output voltage to the power supply voltage. Thereby, even if the resistance value of the resistor R1 is high, the resetting can be sufficiently performed.

§6. Fifth Embodiment Next, a fifth embodiment of the present invention will be described. The configuration example of the contact area sensor according to the present embodiment is the same as the circuit shown in FIG. 1 (the circuit of the first embodiment) except for the light receiving voltage generating circuit in the external drive circuit. In the present embodiment, the circuit shown in FIG. 13 is used as the received light voltage generation circuit instead of the circuit shown in FIG.

FIG. 13 is a circuit diagram showing an example of the received light voltage generating circuit according to the present embodiment. In this figure, an inverting amplifier composed of an operational amplifier OP and a resistor R0 is used as the received light voltage generation circuit. An integrating circuit including an integrating resistor Ri, an operational amplifier OPi, an integrating capacitor Ci, and a reset switch SWi is provided at the subsequent stage of the received light voltage generating circuit.

It should be noted that, in general, 40 is set on the source line.
Since the parasitic capacitance of [pF] exists, when the input resistance value on the negative input terminal side of the operational amplifier OP is large, the charge reading speed becomes very slow, but in the circuit example shown in FIG. Since the input resistance value on the negative input terminal side can be made almost 0 [Ω], the influence of the parasitic capacitance (40 [pF]) on the source wiring can be ignored.

Also in the circuit diagram shown in FIG. 13, it is conceivable to insert a protective resistor on the source line as in the circuit diagram shown in FIG. FIG. 14 is a circuit diagram showing an example in which a protection resistor PR is inserted in the circuit diagram shown in FIG. 13 and 14 have exactly the same circuit configuration except the presence or absence of the protection resistor PR. In FIG.
The protection resistor PR protects the operational amplifier OP (and OPi) and the driving power supply of the operational amplifier OP (and OPi) when the gate line and the source line of the SW-TFT are short-circuited.

Considering the read speed due to the parasitic capacitance (40 [pF]) on the source line, the resistance value of the protection resistor PR neglects the decrease in read speed determined by the product of the parasitic capacitance. It must be small enough to be able to. Further, the resistance value of the protection resistor PR needs to be sufficiently smaller than the ON resistance value of the SW-TFT. Therefore, in the present embodiment, as the resistance value of the protection resistor PR, specifically, 1 to 100 [k
Ω] is possible.

§7. Application Example FIG. 15 is an explanatory diagram showing an example of a case where the contact area sensor according to the present invention is connected as a peripheral device of a personal computer. In this figure, 10 is a peripheral device connected by a SCSI interface (external hard disk drive, magneto-optical disk drive, CD-ROM)
11 is a SCSI interface board for connecting the peripheral device to a personal computer. As shown in this figure, when the contact area sensor according to the present invention is connected to a personal computer, an interface such as SCSI is used.

FIG. 16 is a sectional view showing an application example in the case of capturing color image information using the contact area sensor according to the present invention. As shown in this figure, RG
When the fluorescent lamps of three colors B are sequentially turned on and applied to the original, color image information can be obtained, so that an expensive color filter such as a conventional CCD camera is unnecessary. Also, RG
Compared with a CCD camera that shoots B as one pixel, the resolution is tripled even with the same pixel. Further, in the present invention,
Since all the light accumulated charges can be read out to the received light voltage generation circuit,
At the time of color reading, the afterimage does not occur even if the lights of the three colors of RGB are instantly switched without a time interval.

FIG. 17 is an explanatory diagram showing an application example when a fingerprint is read by using the contact area sensor according to the present invention. In this figure, the angle of effective incident light when the reflected light from the fingerprint enters the TFT sensor is set to 45 ° in advance. The light emitted from the light source wraps around at the valley line of the fingerprint, and a large amount of light enters the TFT sensor. Further, in the ridge line of the fingerprint, since the ridge portion is in close contact with the pressing surface of the finger, the light emitted from the light source does not go around and only a small amount of light is incident on the TFT sensor. Thereby, the valley line and the ridge line of the fingerprint can be distinguished and the image information of the fingerprint can be captured.

If the finger is strongly pressed against the contact area sensor, the valley line may be crushed and it may be difficult to distinguish the valley line and the ridge line. For this reason, as shown in this figure, a pressure sensing film is provided under the light source, and a spring and a contact are provided between the light source and the pressure sensing film. An image reading device such as a computer is notified so that an optimum image is captured.

FIG. 18 is a circuit diagram showing an application example in which the number of received light voltage generation circuits is reduced in order to form an inexpensive system. In the circuit previously shown in FIG.
One light-receiving voltage generating circuit 4 is provided for each source line, and the two are connected in a one-to-one correspondence. That is,
In the circuit shown in FIG. 1, the output signal of each received light voltage generation circuit 4 is input to the multiplexer 5, and the multiplexer 5
In, one output signal is sequentially selected to become a video signal.

On the other hand, as shown in FIG. 18, a multiplexer is provided in the preceding stage of the received light voltage generation circuit 4, and a plurality of source lines are sequentially switched by the multiplexer,
By selecting one source line and inputting the signal of the selected source line to the light receiving voltage generation circuit 4,
It is also conceivable that the number of received light voltage generation circuits 4 is smaller than the number of source lines. Here, the unselected source lines are connected to the reference voltage via the active switches ASWxx. By doing so, the photocharges read on the unselected source lines quickly disappear from the source lines, and thereafter, the photocharges remain on the selected source lines and the afterimages remain. It is possible to avoid such a problem as occurring. Note that, in the circuit shown in FIG. 18, the circuit of the fourth embodiment shown in FIG. 12 is used as the received light voltage generation circuit 4, but in addition to this, FIG. 6 (first embodiment) or FIG. (Second Embodiment) or FIG. 11 (Third Embodiment)
It is also possible to use the circuit shown in the embodiment) or FIG. 13 (fifth embodiment).

19 and 20 are explanatory views showing an application example in the case of increasing the resolution of the contact area sensor according to the present embodiment. First, light is incident from the direction shown in FIG. Therefore, in this figure,
The light that hits the A2 part of the original is the TF shown in A of the figure.
The light incident on the T sensor and hitting the portion B2 of the document enters the TFT sensor shown by B in the figure. As a result, the image information at A2 and B2 on the original can be obtained. Although only a part of the original and the contact area sensor on the cross-sectional view is illustrated and described in this figure, it goes without saying that the original and the contact area sensor are spread two-dimensionally (in a plane). Therefore, in FIG. 19, the image information is read in one of the two areas in the checkered pattern on the original.

Next, light is incident from the direction shown in FIG. As a result, in this figure, the light hitting the portion A1 of the original enters the TFT sensor shown by A in the same figure, and the light hitting the portion B1 of the original becomes the TFT shown by B in the same figure. It is incident on the sensor. As a result, the image information at A1 and B1 on the original can be acquired. As described above, by changing the direction of the light incident from the light source, it is possible to obtain the image information of the contact portion even when the TFT sensor is not provided in the contact portion (just below). You can That is, in the contact area sensor according to the present invention, even if the arrangement of the TFT sensors is sparse on the image reading surface, the light receiving density can be increased by changing the direction of the light incident from the light source. .

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific structure is not limited to this embodiment, and the design change and the like without departing from the gist of the present invention. Even this is included in this invention. For example,
The received light voltage generation circuit shown in the above-described first to fifth embodiments (see FIGS. 6, 10, 11, 12, and 13).
In the above, the operational amplifier OP is used to detect the voltage on the source line, but it is also possible to use a transistor element instead of the operational amplifier OP.

FIG. 21 is a circuit diagram showing an example of the received light voltage generating circuit in the case where a transistor is used instead of the operational amplifier OP in the received light voltage generating circuit shown in FIG.
As shown in this figure, the source line of the TFT sensor unit 2 is connected to the gate terminal of the transistor MOS. The source terminal of the transistor MOS is connected to a reference potential (0 [V]). Further, between the drain terminal and the gate terminal of the transistor MOS, a charge absorbing capacitor C0, and when a reset pulse is input, a reset switching element () that connects between the drain terminal and the gate terminal of the transistor MOS. And the transistor Tr) are connected in parallel. The operation of the received light voltage generating circuit shown in FIG. 21 is basically the same as the operation of the received light voltage generating circuit shown in FIG. However, the source line shown in FIG. 21 has an offset voltage (bias potential Ve) corresponding to the source-gate voltage of the transistor MOS.
Get on.

FIG. 22 is a circuit diagram showing another example of the received light voltage generating circuit using a transistor element. FIG.
The circuit shown in FIG. 2 is a circuit which detects a slight voltage fluctuation on the source line and feeds it back by increasing the amplification degree of the circuit shown in FIG. 21, and consequently suppresses the voltage fluctuation on the source line. . To increase the amplification degree, a constant current source is connected to the drain terminal of the transistor MOS instead of the drain resistance RL shown in FIG.
Since the resistance value of this constant current source can be considered to be almost infinite, a small change in the drain current ID of the transistor MOS causes a large voltage drop at the drain terminal of the transistor MOS as shown in the following equation. ΔVD = ΔID × RD ΔVD: Change in drain voltage ΔID: Change in drain current RD: Output resistance value of drain terminal (= resistance value of constant current source → ∽ [Ω])

Further, the transistor MOS2 shown in FIG.
The source-follower circuit of (1) is provided as a buffer circuit for avoiding a decrease in amplification factor because the input resistance of the multiplexer connected to the next stage has a finite value. Since the transistor MOS2 is a source-follower circuit, even if the input resistance of the multiplexer fluctuates and the drain current of the transistor MOS2 increases, the gate-source voltage V
GS hardly changes (that is, the transistor MO
S2 has a small output resistance).

Further, in the circuit diagram shown in FIG. 1, all the charges generated in the TFT sensor section 2 are taken out in the same direction (to the right in FIG. 1). The arrangement of each circuit is not limited to this. As an example of the extraction pattern, as shown in FIG. 23, charges on adjacent source lines are extracted in opposite directions (staggered extraction).
Can be considered. As another example of the extraction pattern, as shown in FIG. 24, pixels arranged in a two-dimensional matrix are divided into four blocks, that is, upper, lower, left, and right, and charges are extracted in each block (upper, lower, left, and right division). Takeout) is possible.

§8. Advantages over conventional products (a) Advantages in comparison with CCD cameras No expensive color filters are required. As shown in FIG. 16, if the fluorescent lamps of three colors of RGB are sequentially turned on and applied to the document, color image information can be obtained. The resolution is tripled. Since fluorescent image lights of three colors of RGB are sequentially turned on and color image information can be obtained by being applied to a document, the resolution is tripled even with the same pixel as compared with a CCD camera which takes RGB as one pixel.

The device is thin and small. Since a document reader using a CCD needs a reduction optical system, the thickness of the reader cannot be made smaller than the width of the document. However, the contact area sensor according to the present invention does not require the reduction optical system, so that the device can be made thin and small. There is no noise on the screen (S / N ratio is good). The contact area sensor according to the present invention has a wider light receiving area than a CCD camera, and since it is in close contact, there is little loss of light, and strong object light can be obtained by backlight illumination, so photoelectric conversion sensitivity is improved. Therefore, the storage capacity can be increased, and the inclusion of pulse noise in the gate drive pulse or the like can be reduced.

The illumination light is not dazzling and is not affected by outside light. When taking a picture with a TV camera, a large stand for the camera and lighting must be installed, and because the illumination light is dazzling, it is not easy to use the CCD camera next to a personal computer. It doesn't. In addition, illumination light such as a fluorescent light on the ceiling moves into the subject. In the contact area sensor according to the present invention, the light emitted by the backlight passes through the window array for illumination arranged in the sensor,
Since it hits the document that is in close contact with the sensor, no separate illumination is required, and the illumination light does not leak outside.

The system becomes cheaper. When a large number of people take image data, the combination of the polaroid camera and the two-dimensional contact type TFT image scanner according to the present invention, or the combination of the film with lens and the two-dimensional contact type TFT image scanner according to the present invention,
It can be constructed at a lower cost than a system using a CCD camera or the like.
In addition, even when a small number of people input images to a computer with a CCD camera or the like, no photo is left at hand, so in most cases, a hard copy becomes necessary. Therefore, a system including a combination of a CCD camera and a color hard copy machine becomes expensive.

(B) Advantages in comparison with the conventional two-dimensional contact type TFT image scanner The manufacturing process is simple. Conventional two-dimensional contact type T
Since the FT image scanner uses a photodiode as a photoelectric conversion element, it is a switching element α-
Since a Si TFT has to be separately formed, for this reason,
The manufacturing process was complicated. In the contact area sensor according to the present invention, since the α-Si TFT is used for both elements (switching element and optical sensor element), it can be manufactured in one process, and the conventional two-dimensional contact TFT can be manufactured. The manufacturing process is simple compared to image scanners.

Afterimage does not occur. Since all the light accumulated charges can be read out to the readout circuit, no residual image is generated even when the lights of the three colors of RGB are instantly switched at the time of color reading without a time interval. High resolution. Since all the light accumulated charges can be read out to the readout circuit, a reset switch TFT is provided in the pixel.
Becomes unnecessary. Therefore, each pixel can be made small, and the number of pixels per unit area can be increased. Crosstalk between signals does not occur. Since the read circuit is current read (the input resistance of the amplifier is 0 [Ω]) and voltage is hardly generated on the sensor array signal wiring, crosstalk between signals does not occur at the wiring crossover portion.

(C) Advantages in comparison with the conventional line type scanner Pen input is possible. The contact area sensor according to the present invention can be used as a mouse. In Europe and America,
Since the contact area sensor according to the present invention can be used for inputting one's own signature, remote approval is possible. further,
The contact area sensor according to the present invention is most suitable for handwriting input when using graphic software. You can enter your fingerprint. Since the fingerprint can be read easily because it can be attached to the finger, the automatic teller machine (AT
It can be used for security check of M) and ID recognition of computer security.

The reading speed is fast. Conventional scanners store photocharges line by line and then read out the charges to the outside, so it took about 30 seconds to 1 minute to read, but in the contact area sensor according to the present invention, the entire screen is displayed. At the same time, it accumulates photocharges, so the reading is 1
It will be possible in about a second. You can quickly adjust the frame. Except when a CCD camera is used, the conventional scanner has a slow reading speed, so that it takes a lot of time to match the image frames.

There is no need to provide a new installation place.
Since the contact area sensor according to the present invention can be used in place of the conventional mouse, it can be placed in the space where the mouse has been moved so far. Compact and thin. Since the contact area sensor according to the present invention does not have a mechanical drive system and an array lens optical system, it can be made compact and thin.

[0067]

As described above, according to the present invention, since the potential of the signal wiring is always held at the reference potential by the light receiving voltage generating circuit, it is possible to absorb all the signal charges on the signal wiring. Thus, the signal voltage can be efficiently converted. As a result, a contact type area sensor that is resistant to external noise can be configured.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration example of a contact area sensor according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of a contact area sensor to which a protection resistor PRx is added.

FIG. 3 is a plan view showing the structure of a sensor cell.

FIG. 4 is a cross-sectional view showing the structure of a sensor cell.

FIG. 5 is a graph showing characteristics of a thin film transistor that constitutes a TFT sensor.

FIG. 6 is a circuit diagram showing an example of a received voltage generating circuit according to the present embodiment.

FIG. 7 is an explanatory diagram showing the operation principle of the contact area sensor according to the present embodiment.

FIG. 8 is an explanatory diagram showing the operating principle of the contact area sensor when two sensor cells are commonly connected to one source line.

FIG. 9 is an explanatory diagram showing the operation principle of the contact area sensor when two sensor cells are commonly connected to one source line.

FIG. 10 is a circuit diagram showing an example of a received voltage generating circuit according to the present embodiment.

FIG. 11 is a circuit diagram showing an example of a received voltage generating circuit according to the present embodiment.

FIG. 12 is a circuit diagram showing an example of a received light voltage generation circuit according to the present embodiment.

FIG. 13 is a circuit diagram showing an example of a received light voltage generation circuit according to the present embodiment.

14 is a circuit diagram showing an example in which a protection resistor PR is added to the circuit diagram shown in FIG.

FIG. 15 is an explanatory diagram showing an example of connection as a peripheral device of a personal computer.

FIG. 16 is a cross-sectional view showing an application example in the case of capturing color image information.

FIG. 17 is an explanatory diagram showing an application example when a fingerprint is read.

FIG. 18 is a circuit diagram showing an application example when the number of received light voltage generation circuits is reduced.

FIG. 19 is an explanatory diagram showing an application example in the case of increasing the resolution.

FIG. 20 is an explanatory diagram showing an application example in the case of increasing the resolution.

FIG. 21 is a circuit diagram showing an example of a received light voltage generating circuit using a transistor element.

FIG. 22 is a circuit diagram showing another example of the received light voltage generation circuit using a transistor element.

FIG. 23 is an explanatory diagram showing an example of a charge extraction pattern (staggered extraction).

FIG. 24 is an explanatory diagram showing another example of charge extraction patterns (upper, lower, left, and right divided extraction).

FIG. 25 is a block diagram showing a configuration example of a conventional contact area sensor.

[Explanation of symbols]

1 ... Scan shift register, 2 ... TFT sensor section,
3 ... External drive circuit, 4 ... Receiving voltage generation circuit, 5
...... Multiplexer

Claims (8)

[Claims] 1. A plurality of light receiving elements, which are arranged in a two-dimensional matrix in the X and Y directions and generate charges according to the amount of received light, and an emission for controlling the emission of the charges generated in each of the light receiving elements. A control switching element, a plurality of signal wirings that commonly connect the charge emission terminals of the emission control switching elements arranged in the X direction to form the charge transfer path, and the signal wirings arranged in the Y direction. A plurality of scan lines that connect the control terminals of the emission control switching elements in common and form a scan signal path that controls the transfer of the charges, and a scan shift register that sequentially supplies the scan signals to the plurality of scan lines. And a light-receiving voltage that is connected to each of the signal wirings, generates a light-receiving voltage according to the amount of charges transferred on the signal wirings, and
A plurality of light receiving voltage generating circuits for holding the signal wiring at a reference potential or a bias potential determined by the reference potential, and one of the light receiving voltages generated by each light receiving voltage generating circuit are sequentially selected, and the selected light receiving voltage is selected. And a multiplexer that transfers the signal as a video signal. 2. The contact area sensor according to claim 1, wherein the light receiving voltage generating circuit includes an operational amplifier, the light receiving voltage is a signal output from an output terminal of the operational amplifier, and the signal wiring is the signal wiring. Connected to the negative input terminal of the operational amplifier, the positive input terminal of the operational amplifier is set to the reference potential, between the output terminal of the operational amplifier and the negative input terminal, a charge absorption capacitor and a reset A contact-type area sensor, wherein a reset switching element that connects the output terminal and the negative input terminal when a pulse is input is connected in parallel. 3. The contact area sensor according to claim 2, wherein a first resistor is formed on a wiring connecting the reset switching element and the negative input terminal, and the reset switching element is connected to the reset switching element. The contact area sensor, wherein the wiring connecting to the first resistor is set to the reference potential via a second resistor. 4. The contact area sensor according to claim 3, wherein the output terminal of the operational amplifier is set to the reference potential via a fourth resistor, and the output terminal of the operational amplifier and the fourth terminal are connected to each other. A third resistor is formed on a wire connecting the resistor and a terminal connected to the output terminal side of the operational amplifier among terminals of the charge absorbing capacitor is the third resistor and the third resistor. 4 is connected to the middle point of the resistor, and among the terminals of the reset switching element, the terminal connected to the output terminal side of the operational amplifier is a wiring connecting the output terminal and the third resistor. A contact area sensor characterized by being connected to the top. 5. The contact area sensor according to claim 1, wherein the light receiving voltage generating circuit includes a first operational amplifier and a second operational amplifier, and the light receiving voltage is output from an output terminal of the first operational amplifier. The output terminal of the first operational amplifier and the positive input terminal of the second operational amplifier are connected, and the signal wiring is connected to the negative input terminal of the first operational amplifier, The positive input terminal of the first operational amplifier, and the second
The negative input terminal of the operational amplifier is set to the reference potential, and a charge absorption capacitor is connected between the output terminal of the first operational amplifier and the negative input terminal of the first operational amplifier. Between the output terminal of the second operational amplifier and the negative input terminal of the first operational amplifier, a reset switching element that connects the output terminal and the negative input terminal is connected in parallel when a reset pulse is input. A first resistor is formed on a line connecting the reset switching element and the negative input terminal of the first operational amplifier, and the reset switching element and the first resistor are connected to each other. The contact type area sensor, wherein a wiring connecting to and is set to the reference potential via a second resistor. 6. The contact area sensor according to claim 1, wherein the light receiving voltage generating circuit includes an operational amplifier, the light receiving voltage is a signal output from an output terminal of the operational amplifier, and the signal wiring is the signal wiring. Connected to the negative input terminal of the operational amplifier, the positive input terminal of the operational amplifier is set to the reference potential, between the output terminal of the operational amplifier and the negative input terminal, there is a resistance element for feeding back the received light voltage. Contact type area sensor characterized by being connected. 7. The contact area sensor according to claim 1, wherein the received voltage generating circuit includes a transistor element, and a gate terminal (or a base terminal) of the transistor element is connected to the signal line, The source terminal (or emitter terminal) of the transistor element is held at the reference potential, and between the drain terminal and the gate terminal of the transistor element (or between the collector terminal and the base terminal of the transistor element), A charge absorbing capacitor and a reset switching element that connects between the drain terminal and the gate terminal of the transistor element (or between the collector terminal and the base terminal of the transistor element) when a reset pulse is input They are connected in parallel, and the signal wiring is held at the bias potential. Contact area sensor, characterized in that there. 8. The contact area sensor according to claim 1, wherein the signal wiring connecting the charge discharging terminal and the received light voltage generating circuit has a protective resistance. Contact area sensor.