JP3316702B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus,
More specifically, the present invention relates to an image reading apparatus capable of reading an image with high accuracy even when the light amount of a light source fluctuates.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus usually has a built-in light source and a photodiode or a TFT (Thin Film Transistor).
or) are arranged in a matrix. Then, the document is illuminated from a built-in light source, and the reflected light reflected by the document is incident on each photosensor. Each photosensor is provided with a precharge voltage in advance at each reading timing, generates a charge according to the amount of incident light, and outputs the voltage.
It decreases from a value corresponding to the precharge voltage according to the amount of incident light. By detecting the output voltage of each photosensor at each predetermined timing, the amount of light applied to each photosensor is detected, and an image is read.

[0003]

However, in such a conventional image reading apparatus, a constant precharge voltage is always applied to the photosensor irrespective of the light amount of the light source. Changes, the output voltage of each photosensor also changes, and there is a problem that a detection error of the irradiation light amount occurs. Further, in the conventional image reading apparatus, since the light source is built in the apparatus, there is a problem that the image reading apparatus itself is increased in size and cost, and it is difficult to be driven by a battery. .

In particular, when the light amount of the light source decreases, as shown in FIG. 7, the output of the photosensor during light irradiation (shown by a solid line L1 in FIG. 7) and the output of the photosensor during non-light irradiation (FIG. (Indicated by the middle broken line L2) is small, and a detection error of the irradiation light amount is likely to occur, and there is a problem that an image cannot be read accurately. In FIG. 7, the photosensor is reset during the period indicated by a to make the output of the photosensor 0 [V], and precharged during the period indicated by b, and the photosensor is precharged by +10 [V]. Supplying charging voltage. Then, the photosensor is in the sensing state for a period indicated by c, and during this sensing period, the clock CK is set to +10 [V], and the output of the photosensor is read.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and adjusts a precharge voltage in accordance with the light amount of a light source to detect an accurate irradiation light amount even when the light amount of the light source fluctuates. Can read the image with high accuracy,
Also, using external light as a light source, the device can be downsized,
It is an object of the present invention to provide an image reading device that can reduce costs and can be driven by a battery.

[0006]

According to the present invention, there is provided an image reading apparatus, comprising: an output line and image light reading means connected to the output line and having an image photosensor for detecting image light; The above object is achieved by providing a precharge unit that changes a voltage supplied to the output line according to the brightness of the light source.

In this case, the precharge means has, for example, a light source photosensor for receiving light from the light source and generating a current according to the brightness thereof. Is also good.

Further, the image photosensor may be configured such that, for example, an irradiation light amount detection element and a selection switch element are integrally formed.

Further, the photosensor for the light source of the precharge means may have, for example, a structure in which a light source light quantity detection element and a selection switch element are integrally formed.

Further, for example, a plurality of the image photosensors are arranged in a matrix, and the light source photosensors of the precharge means are arranged in the matrix. Provided for each row or column of photosensors, and each output line of each image photosensor connected to the row or column may be precharged simultaneously.

[0011]

According to the present invention, the precharge voltage supplied to the output line of each image photosensor of the image light reading means is changed in accordance with the brightness of the light source. However, the difference between the output voltage of the photosensor at the time of light irradiation and that at the time of non-light irradiation can be made sufficiently large, an accurate amount of light can be detected, and an image can be read with high accuracy. By using the light source as a light source, the device can be reduced in size and cost, and can be driven by a battery.

Further, since each of the image photosensors and the light source photosensors of the precharge means have both the function of the irradiation light amount detecting element, the function of the selection switch element, and the function of the selection transistor, the image reading apparatus is used. Can be further reduced in size, the cost can be further reduced, and the density of pixels can be increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

1 to 6 are views showing an embodiment of an image reading apparatus, FIG. 1 is a circuit diagram of a main part of the image reading apparatus, FIG. 2 is an enlarged sectional view of the photosensor of FIG. FIG. 3 is an equivalent circuit diagram of the photosensor of FIG. 2, FIG. 4 is a diagram showing a signal waveform of the photosensor and a reading timing signal waveform when the light amount is small, and FIG. 5 is a signal waveform of the photosensor when the light amount is medium. FIG. 6 is a diagram showing a signal waveform of a photo sensor and a waveform of a read timing signal when the light amount is large.

Referring to FIG. 1, an image reading apparatus 1 includes a photo sensor area 2 and a precharge circuit 3. The photo sensor area 2 includes nine image photo sensors 4 for simplicity of explanation. They are arranged in a matrix in three rows and three columns.

Each image photosensor 4 has its top gate electrode (TG) connected to top gate lines 5a to 5c arranged in the row direction.
To 5c are supplied with top gate voltages TG1 to TG3 from a top address decoder (not shown). Further, the bottom gate electrode (B
G) shows bottom gate lines 6a to 6c wired in the row direction.
The bottom gate lines 6a to 6c are supplied with bottom gate voltages BG1 to BG3 from a row address decoder (not shown). Further, each image photosensor 4 has its drain electrode (D) connected to signal lines (output lines) 7a to 7c arranged in the column direction, and its source electrode (S) connected in common. Grounded. Each of the signal lines 7a to 7c is connected to a column switch (not shown).
7c and the output of each image photosensor 4 via the column switch.

The precharge circuit 3 is connected to the signal line 7
Three light source photosensors 8a arranged for each of a to 7c
To 8c, and each light source photosensor 8a to 8c
Are connected to the signal lines 7a to 7d, respectively.
c. In addition, each light source photosensor 8a
The precharge signal lines 9 are connected to the top gate electrodes (TGs) of the
Is supplied with a precharge signal PR from a control circuit (not shown). Further, a bottom gate line 6d is connected to a bottom gate electrode (BG) of each of the light source photosensors 8a to 8c, and a bottom gate voltage BG0 from a row address decoder (not shown) is connected to the bottom gate line 6d. Applied. A precharge power supply line 10 is connected to the source electrodes (S) of the light source photosensors 8a to 8c. The precharge power supply line 10 has a +10 [V] precharge from a power supply circuit (not shown). A charging voltage is supplied. Light from the light source is incident on the light source photosensors 8a to 8c, and as described later, the light source photosensors 8a to 8c are used.
c, the operation timing is controlled by the precharge signal PR input to the top gate electrode (TG), and the precharge voltage input to the source electrode (S) is changed according to the amount of light of the incident light source. And outputs the signal to each of the signal lines 7a to 7c.

The image photosensors 4 in the photosensor area 2 and the light source photosensors 8a to 8c in the precharge circuit 3 are configured as shown in FIG.

That is, the image photosensor 4 and the light source photosensors 8a to 8c basically have the same configuration in which an inverted staggered thin film transistor and a coplanar thin film transistor are combined into a single semiconductor layer. ing.

FIG. 2 is an enlarged sectional view showing an example of the structure of the image photosensor 4 and the light source photosensors 8a to 8c. That is, a bottom gate electrode (BG) 21 is formed on a transparent insulating substrate 20 made of glass or the like, and silicon nitride (SiN) is formed so as to cover the bottom gate electrode (BG) 21 and the insulating substrate 20. ) Is formed. On the bottom gate electrode (BG) 21, a semiconductor layer 23 is formed at a position facing the bottom gate electrode (BG) 21, and the semiconductor layer 23 is made of i-type amorphous silicon (ia-Si). ). This semiconductor layer 2
3, a source electrode (S) 24 and a drain electrode (D) 25 are formed on the semiconductor layer 23 at positions facing each other at a predetermined interval, and the source electrode (S)
The drain electrode (D) 25 and the drain electrode (D) 25 are connected to the semiconductor layer 23 via n ⁺ silicon layers 26 and 27 made of amorphous silicon in which a dopant such as phosphorus is diffused. These constitute a bottom transistor (inverted stagger type thin film transistor), and this bottom transistor has a function as a selection switch element described later.

The portion between the source electrode (S) 24 and the drain electrode (D) 25 and the portion of the semiconductor layer 23 between the source electrode (S) 24 and the drain electrode (D) 25 are made of a top gate insulating material made of transparent silicon nitride. A top gate electrode (TG) 29 made of a transparent conductive material is formed on the top gate insulating film 28 at a position facing the bottom gate electrode (BG) 21 on the top gate insulating film 28. . The top gate electrode (TG) 29 is connected to an electron
In order to generate hole pairs, not only the channel region of the semiconductor layer 23 but also the n ⁺ silicon layer 26, as shown in FIG.
27 is desirably formed so as to cover the upper surface. Although not shown, this top gate electrode (TG) 2
A transparent overcoat film made of silicon nitride is formed so as to cover the gate insulating film 9 and the top gate insulating film 28, thereby protecting the film. The top gate electrode (TG) 2
9, a top transistor (coplanar thin film transistor) is formed by the top gate insulating film 28, the semiconductor layer 23, the source electrode (S) 24, and the drain electrode (D) 25. It has a function as an element.

In this embodiment, as shown in FIG. 2, the image photosensor 4 and the light source photosensors 8a to 8c are irradiated with irradiation light A from the top gate electrode (TG) 29 side. A is the top gate electrode (TG) 2
9 and the top gate insulating film 28 and the semiconductor layer 2
3 is irradiated. Note that the image photosensor 4 and the light source photosensors 8a to 8c are not limited to those that irradiate the irradiation light A from the top gate electrode 1 side, as is apparent from the above-described configuration. Even if the irradiation is performed from the (BG) 21 side, the operation described below can be similarly performed.

As described above, the image photosensor 4 and the light source photosensors 8a to 8c have a configuration in which an inverted staggered thin film transistor and a coplanar type thin film transistor are combined, and their equivalent circuits are as shown in FIG. Can be shown.

In the image photosensor 4 and the light source photosensors 8a to 8c, for example, the bottom gate electrode (BG) is 500 ° (angstrom), the bottom gate insulating film 22 is 2000 °, and the semiconductor layer 23 is 1500 °.
Å 500 of source electrode (S) and drain electrode (D)
Å, n ⁺ silicon layers 26 and 27 are 250Å, top gate insulating film 28 is 2000Å, top gate electrode (TG)
29 is formed at 500 ° and the overcoat film is formed at 2000 °, and the source electrode (S) 24 on the semiconductor layer 23 is formed.
And the drain electrode (D) 25 is formed at a distance of 7 μm.

The image photosensor 4 and the light source photosensors 8a to 8c operate as follows.

That is, the bottom gate electrode (B) of the image photosensor 4 and the light source photosensors 8a to 8c.
G) When a positive voltage, for example, +10 [V] is applied to 21, an n-channel is formed in the bottom transistor.
Here, the source electrode (S) 24-drain electrode (D) 2
When a positive voltage, for example, +5 [V] is applied between 5, the electrons are supplied from the source electrode (S) 24 side, and a current flows. In this state, when a negative voltage, for example, −20 [V] at a level for extinguishing the channel due to the electric field of the bottom gate electrode (BG) 21 is applied to the top gate electrode (TG) 29, the top gate electrode (TG) 29 Acts in a direction to reduce the influence of the electric field of the bottom gate electrode (BG) 21 on the channel layer. As a result, the depletion layer extends in the thickness direction of the semiconductor layer 23 and pinches off the n-channel. At this time, when the irradiation light A is irradiated from the top gate electrode (TG) 29 side, an electron-hole pair is induced on the top gate electrode (TG) 29 side of the semiconductor layer 23. Since -20 [V] is applied to the top gate electrode (TG) 29, the induced holes are accumulated in the channel region and cancel the electric field of the top gate electrode (TG) 29. Therefore, an n-channel is formed in the channel region of the semiconductor layer 23, and a current flows. Source electrode (S) 2
The current flowing between the 4-drain electrode (D) 25 (hereinafter, drain current I _DS ) changes according to the amount of irradiation light A.

As described above, in the image photosensor 4 and the light source photosensors 8a to 8c, the electric field from the top gate electrode (TG) 29 is changed by the bottom gate electrode (BG) 2
Since the n-channel is pinched off by controlling so as to prevent the channel formation by the electric field from 1, the drain current I _DS flowing without light irradiation is extremely small, for example, 10 ⁻¹⁴ A. Degree. As a result, an image photosensor 4 and the light source for the photo sensor 8a~8c is able to sufficiently increase the difference between the drain current I _DS at the time of light non-irradiating light irradiation,
In addition, the amplification factor of the bottom transistor at this time changes depending on the amount of irradiated light, and the S / N ratio can be increased.

The image photosensor 4 and the light source photosensors 8a to 8c are provided with a bottom gate electrode (BG).
When the top gate electrode (TG) 29 is set to, for example, 0 [V] while a positive voltage (+10 [V]) is applied to the trap 21, the trap voltage between the semiconductor layer 23 and the top gate insulating film 28 is changed. The holes can be discharged from the holes to refresh, that is, reset. That is, the image photosensor 4 and the light source photosensors 8a to 8c
Is used continuously, trap levels between the top gate insulating film 28 and the semiconductor layer 23 are filled with holes generated by light irradiation and holes injected from the drain electrode (D) 25. In addition, the channel resistance in the non-light irradiation state also becomes small, and the drain current _IDS increases in the no light irradiation. Therefore, 0 is applied to the top gate electrode (TG) 29.
[V] is applied to cause the holes to be discharged, and reset.

Further, the image photosensor 4 and the light source photosensors 8a to 8c are provided with a bottom gate electrode (B
G) When a positive voltage is not applied to 21, no channel is formed in the bottom transistor, and even if light irradiation is performed, the drain current I _DS does not flow, and the non-selected state can be obtained. That is, the photo sensor 4 and the photo sensor 8a~8c light source image by controlling the voltage V _BG applied to the bottom gate electrode (BG) 21, it can be controlled and selected or deselected.
In this non-selected state, the top gate electrode (T
G) When 0 [V] is applied to 29, similarly to the above, holes can be discharged from the trap level between the semiconductor layer 23 and the top gate insulating film 28 to reset.

Therefore, the image photosensor 4 and the light source photosensors 8a to 8c have the top gate voltage V
_{By controlling TG} to, for example, 0 [V] and -20 [V], the sense state and the reset state can be controlled, and the bottom gate voltage V _BG can be set to, for example, 0 [V].
By controlling to [V] and +10 [V], the selected state and the non-selected state can be controlled. as a result,
By controlling the top gate voltage V _TG and the bottom gate voltage V _BG , the image photosensor 4 and the light source photosensors 8a to 8c can themselves function as an irradiation light amount detection element and as a selection switch element. It can be operated as a device having the above function.

[0031] Thus, the photo sensor 4 and the photo sensor 8a~8c light source image, in the sense state, when the light irradiation, the drain current I _DS flows, its output voltage drops, the drain The magnitude of the current I _DS , that is, the decrease of the output voltage depends on the irradiation light amount,
The output voltage of the image photosensor 4 and the light source photosensors 8a to 8c is reduced due to a leak current. Therefore, in the light source photosensors 8a to 8c in the photosensor area 2, even if the degree of whiteness of the detection target such as a document is the same, when the light amount of the light source changes, the output voltage of the light source photosensors 8a to 8c also changes. . Therefore, in the present embodiment, as described later, the voltage value of the precharge voltage supplied to the light source photosensors 8a to 8c is adjusted according to the light amount of the light source.

The fact that the image photosensor 4 and the light source photosensors 8a to 8c have both a function as an irradiation light amount detection element and a function as a selection switch element is shown in FIG. Thus, it is applied to the photosensor area 2. Therefore, as shown in FIG. 1, the photosensor area 2 can omit the selection transistor provided in the conventional photosensor array, and can integrate and reduce the size of the photosensor area 2. The area 2 and thus the image reading device 1 can be reduced in size, and the image reading device 1 can be made inexpensive.

The image reading apparatus 1 does not include a light source, but uses an external light source such as natural light or external light such as a fluorescent lamp in a room where the image reading apparatus 1 is installed. . Therefore, the size of the image reading device 1 can be further reduced, and the cost of the image reading device 1 can be further reduced.

Next, the operation will be described.

The image reading apparatus 1 reads the output of each image photosensor 4 in the photosensor area 2 by a so-called line sequential reading method. That is, to each image photo sensor 4 in the photo sensor area 2, top gate voltages TG1 to TG3 are applied from a top address decoder (not shown) and bottom gate voltages BG1 to BG3 from a low address decoder (not shown) for each row. Is applied to control the reset state and the sense state, and to control the selected state and the non-selected state. Then, the outputs of the image photosensors 4 in each selected state are sequentially taken out via signal lines 7a to 7c and a column switch (not shown).

That is, as shown in FIGS. 4 to 6, the image reading device 1 sets the reading period T as one cycle, and during this reading period T, the top gate voltages TG1 to TG3 of the respective image photosensors 4. And bottom gate voltages BG1 to BG
3 is switched as described below, the signal of each image photosensor 4 is read out.

First, as shown in FIGS. 4 to 6, during the reset period indicated by a, the top gate voltages TG1 to TG
3 is set to +5 [V], and the photosensors 4 for each image in the row direction are reset.

Next, in the precharge period shown in b, each light source photosensor 8a to 8
8c, +10 [V] as a bottom gate voltage BG0 and 0 [V] as a precharge signal PR as a top gate voltage TG are applied to each of the light source photosensors 8a to 8c.
In the sense state. The photosensor 8a~8c for each light source of the precharge circuit 3 during the precharge period, the signal lines and the drain current I _DS corresponding to the quantity of the light source 7a~
The signal lines (output lines) 7a to 7c of the respective image photosensors 4 in the photosensor area 2 are supplied via the photosensor area 7c, and the respective image photosensors 4 are precharged by the drain current _IDS . Therefore, the signal lines (output lines) 7a to 7c of the respective image photosensors 4 in the photosensor area 2 connected to the signal lines (output lines) 7a to 7c.
As shown in FIGS. 4 to 6, a precharge voltage having a voltage value corresponding to the light amount of the light source is supplied to 7c.

For example, when the light amount of the external light source is small (when the illuminance is low), a voltage lower than +10 [V] is supplied to the image photosensor 4 as a precharge voltage as shown in FIG. When the amount of light from the external light source is moderate, as shown in FIG. 5, a voltage higher than the precharge voltage in FIG. 4 but lower than +10 [V] is set as the precharge voltage as a signal line ( Output line)
7a to 7c. When the amount of light from the external light source is sufficiently large (illuminance is high), as shown in FIG. 6, +10 [V] is supplied to the signal lines (output lines) 7a to 7c of the image photosensor 4 as a precharge voltage. You.

When the precharge voltage is supplied in this manner, next, the top gate voltages VTG1 to TG3 are set to 0.
[V] to bring the image photosensor 4 into the sensing state. At this time, the image photosensor 4, as described above, since outputs the drain current I _DS according to the irradiation amount of light,
As shown in FIGS. 4 to 6, the output voltage decreases from the precharged voltage as time elapses according to the irradiation light amount. In this sense state, the outputs of the image photosensors 4 arranged in the row direction are output from the signal lines (output lines) 7a to 7c at the timing of the clock CK.
Sequentially.

However, each image photosensor 4 has:
As described above, since the precharge voltage having the voltage value corresponding to the light amount of the light source is supplied, as shown in FIGS. 4 to 6, the output of the image photosensor 4 at the time of light irradiation (see FIGS. 6 (indicated by a solid line L3) and the output of the image photosensor 4 during non-light irradiation (indicated by a broken line L4 in FIGS. 4 to 6) can be made sufficiently large, and the detection of the irradiation light amount can be performed. It can be performed with high accuracy. As a result, an image can be read accurately. That is, as shown in FIG. 4, when the light amount of the light source is small, the precharge voltage is low, and the light irradiation in the sensing state makes the discharge of the image photosensor 4 easy. The difference between the output of the sensor 4 (solid line L3) and the output of the image photosensor 4 during non-light irradiation (dashed line L4) can be made sufficiently large. In addition, when the light amount of the light source is medium, the precharge voltage is slightly increased as shown in FIG.
Similarly, the difference between the output (solid line L3) of the image photosensor 4 when irradiating light with a moderate amount of light and the output (dashed line L4) of the image photosensor 4 during non-light irradiation is made sufficiently large. be able to. Further, when the light amount of the light source is large, as shown in FIG.
Similarly, the difference between the output (solid line L3) of the image photosensor 4 when irradiating a large amount of light and the output (dashed line L4) of the image photosensor 4 during non-light irradiation is made sufficiently large. be able to.

As described above, in the image reading apparatus 1 of the present embodiment, the precharge voltage to be supplied in advance to the signal lines (output lines) 7a to 7c of each image photosensor 4 in accordance with the irradiation light amount of the light source. Photo sensor 8a for light source
8c, the difference between the output voltage of the image photosensor 4 at the time of light irradiation and the time of non-light irradiation can be made sufficiently large even if the light amount of the light source fluctuates. , The image can be read with high accuracy, the external light can be used as a light source, the size of the image reading device 1 can be reduced, and the cost of the image reading device 1 can be reduced. Further, the image reading apparatus 1 can be driven by a battery, and the usability of the image reading and governing 1 can be improved.

The light source photosensors 8a to 8c included in the image photosensor 4 and the precharge means are arranged such that the source electrode (S) 24 and the drain electrode (D) 25 face each other with the semiconductor layer 23 interposed therebetween. These semiconductor layers 2
3. Source electrode (S) 24 and drain electrode (D) 25
And a pair of gate electrodes 2 at positions opposing the semiconductor layer 23 on both sides thereof with insulating films 22 and 28 interposed therebetween.
1 and 29 are arranged, and one of the pair of gate electrodes 21 and 29 is used as a light irradiation side, and light irradiated from the light irradiation side passes through the insulating films 22 and 28 on the light irradiation side. Therefore, the image photosensor 4 and the light source photosensors 8a to 8c can have both a function as an irradiation light amount detection element and a function as a selection switch element. The image reading device 1 can be further reduced in size, the cost can be further reduced, and the density of pixels can be increased.

In the above embodiment, a so-called double gate type photo sensor is used as each image photo sensor 4 in the photo sensor area 2. However, the present invention is not limited to this. The present invention can be similarly applied to the case where is used.

In the above embodiment, the pre-charge light source photosensors 8a to 8c are provided for each column. However, it is not necessary to provide the photosensors 8a to 8c for each column. In addition, a double-gate photosensor is used for precharging, but any type can be used as long as the precharge voltage can be adjusted according to the light amount of the light source. good.

[0046]

According to the present invention, the precharge voltage supplied to the output line of each image photosensor of the image light reading means is changed according to the brightness of the light source.
Even if the light amount of the light source fluctuates, the difference in the output voltage of the photosensor between light irradiation and non-light irradiation can be made sufficiently large, and an accurate light amount can be detected and an image can be read with high accuracy. In addition, by using external light as a light source, the size of the device can be reduced, the cost can be reduced, and the battery can be driven.

Each of the image photosensors and the light source photosensor of the precharge means has both the function of the irradiation light amount detecting element, the function of the selection switch element, and the function of the selection transistor. Can be further reduced in size, the cost can be further reduced, and the density of pixels can be increased.

[Brief description of the drawings]

FIG. 1 is a main part circuit configuration diagram of an embodiment of an image reading apparatus according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a photo sensor applied to a photo sensor area of the image reading device of FIG.

FIG. 3 is an equivalent circuit of the photosensor of FIG. 2;

FIG. 4 is a diagram showing a precharge voltage when a light amount of a light source is small, and an output of an image photosensor at the time of light irradiation and non-light irradiation at that time.

FIG. 5 is a diagram showing a precharge voltage when the light amount of the light source is medium, and an output of the image photosensor at the time of light irradiation and non-light irradiation at that time.

FIG. 6 is a diagram showing a precharge voltage when the light amount of the light source is large, and an output of the image photosensor at the time of light irradiation and non-light irradiation at that time.

FIG. 7 is a diagram showing a precharge voltage when a light amount of a light source by a conventional photosensor is small, and an output of the photosensor at the time of light irradiation and non-light irradiation at that time.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 2 Photosensor area 3 Precharge circuit 4 Image photosensor 5a-5c Top gate line 6a-6c Bottom gate line 7a-7c Signal line (output line) 8a-8c Light source photosensor 9 Precharge signal line PR precharge voltage 20 Insulating substrate 21 Bottom gate electrode (BG) 22 Bottom gate insulating film 23 Semiconductor layer 24 Source electrode (S) 25 Drain electrode (D) 26, 27 n ⁺ silicon layer 28 Top gate insulating film 29 Top gate Electrode (TG)

Claims (5)

(57) [Claims] 1. An image light reading means having an output line and an image photosensor connected to the output line for detecting image light, and connected to the output line and supplied to the output line according to the brightness of a light source. An image reading apparatus comprising: a precharge unit that changes a voltage to be applied. 2. The image reading apparatus according to claim 1, wherein said precharge means includes a light source photosensor for receiving light from a light source and generating a current corresponding to the brightness of the light. 3. The image photosensor according to claim 1, wherein the irradiation light amount detection element and the selection switch element are integrally formed.
The image reading device according to claim 1. 4. The image according to claim 2, wherein the light source photosensor of the precharge means has a structure in which a light source light quantity detection element and a selection switch element are integrally formed. Reader. 5. A plurality of image photosensors are arranged in a matrix, and the light source photosensors of the precharge means are arranged in rows or columns of the image photosensors arranged in a matrix. 5. The image reading apparatus according to claim 3, wherein each output line of each image photosensor connected to said row or column is simultaneously precharged.