JPH06276365A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain the picture reader which reads a picture in a required minimum time by changing the resolution of an image sensor. CONSTITUTION:In the case of reading at a low resolution, a control means 10 sends a gate pulse from odd number and even number gate pulse generating circuits 8, 9 to odd number and even number gate signal lines 4, 5. A charge generated in an odd number light receiving element and an even number light receiving element 1 is transferred simultaneously to a wire capacitance of a common signal line 6 from odd number and even number charge transfer sections 2, 3 in each block and stored. Then each common signal line 6 is scanned by a read IC7 and a voltage of the common signal line 6 is outputted at an output terminal Com in time series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device for reading an image, such as an image scanner or a facsimile.

[0002]

2. Description of the Related Art As an image sensor that has been used conventionally, there is a contact image sensor that projects image information of a document or the like on the image sensor in a one-to-one manner and converts it into an electric signal. As one of the contact type image sensors, for example, as disclosed in Japanese Patent Laid-Open No. 62-67864,
A TFT drive type image sensor has been developed. This T
In the FT drive type image sensor, the projected image is divided into a large number of images, each light receiving element receives the light, and the charges generated in each light receiving element are used in a specific block unit between wirings by a thin film transistor switch element (TFT). The data is temporarily stored in a capacitor and sequentially read out as an electric signal in time series at a speed of several hundred KHz to several hundred MHz. This TFT drive type image sensor can read by a single gate driving IC and a single reading IC by the operation of the TFT, so the number of driving ICs and reading ICs that drive the image sensor can be reduced. Is what you can do.

In this TFT drive type image sensor, the light receiving element is divided into a plurality of blocks in order to read at high resolution at high speed, as described in the above-mentioned document and Japanese Patent Laid-Open No. 1-94655. Then, for each block, a common wiring is provided for the light receiving elements in the block,
There is a technique of driving a TFT connected to one light receiving element in each block, and transferring charges generated in the light receiving element to a common wiring for each block.

In the TFT drive type image sensor having such a structure, even when a low-density image is read with low-resolution information, after reading with high resolution, image data is thinned or averaged to perform pixel processing. There is a problem that the density conversion must be performed, the reading time becomes long, and a large amount of image memory is required.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image reading apparatus which changes the resolution of an image sensor and reads an image in a necessary minimum time. It is what

[0006]

According to the present invention, an image reading apparatus for reading an image is provided with a light receiving element array in which a plurality of light receiving elements are arranged as one block and an output side of each light receiving element. A switching element, a block-specific common data line that commonly connects the output sides of the switching elements corresponding to the light-receiving elements of each block, a read circuit connected to each block-specific common data line, and each block A plurality of control lines connected to switching elements corresponding to light receiving elements having the same ordinal number, a drive circuit for controlling the drive of the plurality of control lines, and a density control for controlling the operation of the drive circuit according to the read density. Means, one or more control lines are driven according to the read density, and one or more receiving lines are provided to the read circuit of each block. It is characterized in that the signal from the device is read.

[0007]

According to the present invention, since the density control means is provided, when the resolution is reduced by the image to be read, the drive circuit is controlled so that two or more control lines are driven. As a result, the switching elements corresponding to the two or more light receiving elements in each block become conductive, and the signals of the two or more light receiving elements are simultaneously output to the common data line. A low-resolution image can be obtained without performing image processing such as taking an average. At this time, since the charges of two or more light receiving elements in each block are transferred by one driving, it is possible to reduce the number of driving times until the entire light receiving element array is scanned, and it is possible to reduce the number of times required. Image information can be read.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an overall block diagram of an embodiment of an image reading apparatus of the present invention, and FIG. 2 is an explanatory view of one block of gate wiring in an embodiment of the image reading apparatus of the present invention. In the figure, 1 is a light receiving element array, 2 is an odd-numbered charge transfer section, 3 is an even-numbered charge transfer section, 4 is an odd-numbered gate signal line, 5 is an even-numbered gate signal line, and 6 is a common signal line. , 7 is a reading IC, 8 is an odd-numbered gate pulse generation circuit, 9 is an even-numbered gate pulse generation circuit, 10 is control means, 11 is a light receiving element, and 12 is a thin film transistor. Here, for simplification, a case of driving with two scanning circuits will be described.

The light-receiving element array 1 includes a light-receiving element 11 such as a photodiode on an insulating substrate such as glass.
One block is composed of × m blocks, and n blocks are arranged. The odd-numbered charge transfer section 2 is composed of the thin film transistors 12 connected to the odd-numbered light-receiving elements 11 respectively, and the even-numbered charge transfer section 3 is connected to the even-numbered thin-film transistors 12 of each light-receiving element 11. It is composed of Thin film transistor 12
Performs an on / off operation in response to a signal from the gate line, and transfers the charge accumulated in the light receiving element 11 to the common signal line. In FIG. 1, each rectangle of the light receiving element array 1 and the odd-numbered and even-numbered charge transfer units 2 and 3 indicates a block. Further, in FIG. 2, the light receiving element 11 of the i-th block is replaced by the light receiving elements PD _{1-1, i} , P
D _{2-1, i} , PD _{1-2, i} , PD _{2-2, i} , ..., PD
_{1-m, i} , PD _{2-m, i} , corresponding thin film transistor 12
Are thin film transistors T _{1-1, i} , T _{2-1, i} , T
_{2-1, i} , T _{2-2, i} , ..., T _1-m , T _2-m .

The common signal line 6 is provided for each block, n in number, and holds the charges transferred by each thin film transistor 12 in the block in the wiring capacitance C _Li (i = 1 to n) for reading. Lead to IC7. To the reading IC 7, n common signal lines 6 are connected, and the read signals transferred from the common signal line 6 are sequentially selectively scanned and output.

The odd-numbered gate pulse generation circuit 8 generates a gate signal for driving the thin film transistor 12 of the odd-numbered charge transfer section 2 that transfers the odd-numbered charges of each light receiving element 11, and outputs the odd-numbered gate. It is sent to the signal line 4. Further, the even-numbered gate pulse generation circuit 9 generates a gate signal for driving the thin film transistor 12 of the even-numbered charge transfer unit 3 that transfers the even-numbered charges of each light receiving element 11, and outputs the even-numbered gate signal. Send to line 5. Each of the odd-numbered gate signal line 4 and the even-numbered gate signal line 5 is composed of n / 2 lines, and each signal line is connected to the gate of the thin film transistor 12 corresponding to the light receiving element 11 having the same ordinal number of each block. It is connected.
For example, one gate line G _1-1 , G _1-2 , ..., G _1-m of the odd-numbered gate signal line 4 shown in FIG. 2 is the first, third, ... .., respectively connected to the gates of the thin film transistors 12 corresponding to the (2m-1) th light receiving element 11. The same applies to the even-numbered gate signal line 5.

The control means 10 controls the odd-numbered gate pulse generation circuit 8 and the even-numbered gate pulse generation circuit 9. At this time, the control means 10 performs control according to the reading density based on the selection signal. That is, at the time of high-density reading, the odd-numbered or even-numbered gate pulse generation circuits 8 and 9 are alternately operated to sequentially scan the light receiving elements 11 in each block. When reading at low density, the odd-numbered and even-numbered gate pulse generation circuits 8 and 9 are simultaneously operated to simultaneously output the charges of the odd-numbered light-receiving element 11 and the even-numbered light-receiving element 11 to the common signal line 6. Control to let.

Next, a driving method in one embodiment of the image reading apparatus of the present invention will be described. First, a case of reading at high density will be described with reference to FIG. Figure 3
FIG. 7 is a timing chart of gate signals at the time of high-density reading. In this case, for example, the arrangement density of the light receiving elements is 6
The case of 00 dpi corresponds to reading at a density of 600 dpi.

When the start pulse ST is input to the control means 10 and the reading IC 7, the operation starts in synchronization with the clock CK. The control means 10 first transmits the gate pulse φG _1-1 from the odd-numbered gate pulse generation circuit 8 to the gate line G _1-1 in the odd-numbered gate signal line 4. In each block, the thin film transistor T
_{1-1, i} (i = 1 to n) is turned on, and the light receiving element PD
_The electric charge generated in _{1-1, i} (i = 1 to n) is the wiring capacitance C _Li.
(I = 1 to n), and accumulated. Then, the electric charge accumulated in each wiring capacitance C _Li (i = 1 to n) changes the potential of each common signal line 6. By sequentially turning on analog switches SW _i (i = 1 to n) (not shown) in the reading IC 7, the voltage value of each common signal line 6 is output to the output terminal Com in time series. Then, after the signal potential is detected, the reset switch RS _i (i = 1 to n) (not shown) in the reading IC 7 is turned on to charge accumulated in each wiring capacitance C _Li (i = 1 to n). To prepare for the next reading.

Next, the control means 10 transmits the gate pulse φG _2-1 from the even-numbered gate pulse generation circuit 9 to the gate line G _2-1 in the even-numbered gate signal line 5. In each block, the thin film transistor T _{2-1, i} (i
= 1 to n) are turned on, and the light receiving elements PD _{2-1, i} (i = 1)
To n), the charge generated in each of the wiring capacitances C _Li (i = 1 to n)
Transferred to and accumulated. Then, each wiring capacitance C _Li (i = 1 to 1
The electric charge accumulated in n) changes the potential of each common signal line 6. By sequentially turning on analog switches SW _i (i = 1 to n) (not shown) in the reading IC 7, the voltage value of each common signal line 6 is output to the output terminal Com in time series. Then, after detecting the signal potential, a reset switch RS _i (i =
1 to n) are turned on, each wiring capacitance C _Li (i
= 1 to n) to discharge the accumulated charge and prepare for the next reading.

Similarly, the control means 10 alternately transmits gate pulses from the odd-numbered gate pulse generation circuit 8 and the even-numbered gate pulse generation circuit 9, and sequentially,
Thin film transistor T _{1-2, i} (i = 1 to n) to T
By turning on _{2-m, i} (i = 1 to n), the charges generated in the light receiving element can be sequentially transferred to obtain one line of image information. Further, a document feeding means such as a roller or a moving means of a unit having an image sensor mounted thereon relatively moves the image sensor and the document to perform sub-scanning to obtain an image signal of the entire document.

Next, the case of reading at low density will be described with reference to FIG. FIG. 4 is a timing chart of gate signals at the time of low density reading. Here, 1 /
The case of reading at a density of 2 will be described as an example. In this case, for example, when the array density of the light receiving elements is 600 dpi, this corresponds to reading at a density of 300 dpi.

When the start pulse ST is input to the control means 10 and the reading IC 7, the operation starts in synchronization with the clock CK. A signal for reading at low density is input to the control means 10 as a selection signal. By the control means 10, first, from the odd-numbered gate pulse generation circuit 8 and the even-numbered gate pulse generation circuit 9, the gate line G _1-1 in the odd-numbered gate signal line 4 and the even-numbered gate signal line 5 The gate pulse φG _1-1 and the gate pulse φG _2-1 are transmitted to the gate line G _2-1 .
In each block, the thin film transistors T _{1-1, i} and the thin film transistors T _{2-1, i} (i = 1 to n) are turned on, and the light receiving elements PD _{1-1, i} and the light receiving elements PD _{2-1, i} (i
= 1 to n), the charge generated in each wiring capacitance C _Li (i = 1 to 1)
n) and stored. And each wiring capacitance C _Li
Each common signal line 6 is generated by the charges accumulated in (i = 1 to n).
The electric potential of changes. By sequentially turning on analog switches SW _i (i = 1 to n) (not shown) in the reading IC 7, the voltage value of the common signal line 6 is output to the output terminal Com in time series. After detecting the signal potential, a reset switch RS _{i (} not shown) in the reading IC 7
By turning on (i = 1 to n), each wiring capacitance C
The charges accumulated in L _i (i = 1 to n) are discharged to prepare for the next reading.

Similarly, at the next timing, the controller 1
0, the odd-numbered gate pulse generating circuit 8 and the even-numbered gate pulse generating circuit gate lines G _1-2 of odd-numbered gate signal line 4 to 9 and the even-numbered gate signal line in the fifth gate line G _{2 The} gate pulse φG _1-2 and the gate pulse φG _2-2 are transmitted to _-2 . In each block, the thin film transistors T _{1-1, i} and the thin film transistors T _{2-2, i} (i = 1 to n) are turned on, and the light receiving element PD
_The charges generated in _{1-2, i} and the light receiving element PD _{2-2, i} (i = 1 to n) are transferred to and accumulated in each wiring capacitance CL _i (i = 1 to n). Then, each wiring capacitance C _Li (i = 1 to 1
The potential of each common signal line 6 changes due to the charges accumulated in n). By sequentially turning on analog switches SW _i (i = 1 to n) (not shown) in the reading IC 7, the voltage value of the common signal line 6 is output to the output terminal (Com) in time series. After detecting the signal potential, the reset switch RS _i (i
= 1 to n), the wiring capacitance C
Electrification accumulated in _Li (i = 1 to n) is discharged to prepare for the next reading.

In this way, odd-numbered gate pulse
Generating circuit 8 and even-numbered gate pulse generating circuit 9
Gate pulse is transmitted from_{1-3, i}~ T_{1-m, i}and
T_{2- 3, i}~ T_{2-m, i}Turn on (i = 1 to n) sequentially
By doing so, the charges generated in the light receiving element are sequentially transferred,
Image information for one line can be obtained. In addition, low
A document feeding means such as LA or image sensor is installed.
Use the unit's moving means to align the image sensor with the original.
Sub-scanning is performed by moving in opposite directions, and the entire document is
To obtain the image signal of. At this time, the relative movement amount is high
By scanning twice the number of
The read density can also be halved.

By the above operation, for example, the resolution is halved.
If you drop it in the
It becomes possible to complete the line reading, and
It is equivalent to that read by an image sensor with the resolution of. At this time, low-density reading can be performed without requiring image processing such as pixel density conversion.

In the above-described embodiment, the switchable image densities are of two types, equal size and 1/2, but not limited to this.
For example, if reading at a density of 1/3,
Three gate pulse generation circuits are prepared, each of which is 3j-
The second, 3j−1, and 3jth (j = 1 to k) thin film transistors may be controlled to be driven. At this time, each group may be composed of 3 × k light receiving elements. Further, it is of course possible to set three or more densities and switch them.

Further, the thin film transistor 1 described with reference to FIG.
2 are directly connected to the light receiving element 11, respectively,
It is not limited to this. The thin film transistor 12 may be provided by interposing an appropriate circuit between the light receiving element 11 and the thin film transistor 12, such as a batch transfer switch circuit and a storage capacitor.

[0024]

As is apparent from the above description, according to the present invention, the signals of a plurality of light receiving elements are simultaneously output to the common data line when the image to be read is reduced in resolution and read. It is possible to obtain a low-resolution image without performing image processing such as averaging that has been performed, and it is possible to reduce the number of times of driving until the entire light-receiving element array is scanned. The image information can be read out in time.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of an image reading apparatus of the present invention.

FIG. 2 is an explanatory diagram of one block of gate wiring in one embodiment of the image reading apparatus of the present invention.

FIG. 3 is a timing chart of gate signals at the time of high-density reading.

FIG. 4 is a timing chart of gate signals during low-density reading.

[Explanation of symbols]

1 light receiving element array, 2 odd number charge transfer section, 3
Charge transfer section for even number, gate signal line for odd number,
5 even-numbered gate signal lines, 6 common signal lines, 7 reading ICs, 8 even-numbered gate pulse generation circuits,
9 odd number gate pulse generation circuit, 10 control means, 11 light receiving element, 12 thin film transistor.

Claims (1)

[Claims] 1. An image reading apparatus for reading an image, wherein a light receiving element array in which a plurality of light receiving elements are arranged as one block, a switching element provided on the output side of each light receiving element, and a light receiving element of each block are provided. Common data line unique to the block that connects the output side of the switching elements corresponding to the elements in common, the read circuit connected to the common data line unique to each block, and the light receiving element having the same ordinal number of each block The read density includes a plurality of control lines connected to the corresponding switching elements, a drive circuit for controlling the drive of the plurality of control lines, and a density control unit for controlling the operation of the drive circuit according to the read density. One or more control lines are driven according to the above, and the signals from one or more light receiving elements are read out to the readout circuit of each block. An image reading device characterized in that