JPH06303378A - Picture reader - Google Patents

Abstract

PURPOSE:To provide a picture reader capable of changing the resolution of reading corresponding to the resolution of an original. CONSTITUTION:Plural photodiodes for constituting a photodetector array 1 are alternately connected to a first electric charge transfer part 2 and a second electric charge transfer part 3. In the meantime, the first electric charge transfer part 2 is driven by a first gate pulse generator 5 and the second electric charge transfer part 3 is driven by the second gate pulse generator 6 respectively. Further, whether both of the first and second gate pulse generators 5 and 6 or only one of them is in an operating state is controlled by a control circuit 7, signal reading from all the photodiodes of the photodetector array 1 or the signal reading from half the number of the photodiodes can be selected by setting the operating state and the reading resolution can be switched.

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,
In particular, it relates to improvement of resolution characteristics in an image reading apparatus having an image sensor composed of a plurality of light receiving elements.

[0002]

2. Description of the Related Art Conventionally, as this type of image reading apparatus,
For example, a so-called contact type image including a plurality of light receiving elements.
A thin film field effect transistor (TFT) as a switching element connected to each light receiving element of the image sensor, and several thin film field effect transistor (TFT) sources are mutually connected. It is well known and well known that the gates are connected to each other while the gates are so-called matrix wiring so that the photocharges generated in the light receiving elements can be simultaneously read out from the light receiving elements at the same position for each block (for example, , JP-A-1-94655).

[0003]

However, in the image reading apparatus as described above, the image signals are read from all the light receiving elements constituting the image sensor regardless of the resolution of the original, and the image signal is read. Since processing is performed, even if the original document itself has a low resolution and it is not necessary to read it at a high resolution, the result is that the same reading as a high resolution document is performed. , It takes more time to read than originally needed,
There is a problem that not only the processing speed of the device is lowered, but also the capacity of the memory for temporarily storing the image signal in the external device is made unnecessarily large, so that the so-called cost performance is lowered. .

The present invention has been made in view of the above circumstances, and provides an image reading apparatus capable of changing the reading resolution according to a document.

[0005]

SUMMARY OF THE INVENTION An image reading apparatus according to the present invention is an image sensor including a plurality of light receiving elements, and transfers charges generated in the light receiving elements provided on the output side of the plurality of light receiving elements. A plurality of switching elements,
Switching control means for controlling the operation of the plurality of switching elements, the plurality of switching control means connected to the plurality of light receiving elements at a constant number of light receiving elements, and the operation of each of the plurality of switching control means And an operation control means for controlling the operation.

[0006]

When the operation control means controls the operation and non-operation of the plurality of switching control means and all the switching control means operate, the electric charge is output to the outside from all the light receiving elements through the switching elements. On the other hand, when the specific switching control means is brought into the operating state, the electric charges are read out only from the light receiving elements connected to the switching elements driven by the specific switching control means, and all the light receiving elements are read. Among these, since the charges are read out only from a specific light receiving element for every plurality of light receiving elements, the processing time can be shortened with a low resolution.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to the present invention will be described below with reference to FIGS. Here, FIG. 1 is a schematic configuration diagram showing one configuration example of the image reading apparatus according to the present invention, FIG. 2 is a circuit diagram showing a specific configuration example in one block of the image reading apparatus shown in FIG. 1, and FIG. Is a timing chart regarding main signals for explaining the operation of the apparatus when reading at high resolution, and FIG. 4 is a timing chart regarding main signals for explaining the operation of the apparatus when reading at low resolution. is there.

This image reading apparatus comprises a light receiving element array 1
A first charge transfer section 2, a second charge transfer section 3, a read IC 4, a first gate pulse generator 5, a second gate pulse generator 6, and a control circuit 7. , Are the main components (see FIG. 1). Light receiving element array 1
Is composed of, for example, a plurality of photodiodes PD as light receiving elements, and is a so-called line image sensor in this embodiment. Further, the light receiving element array 1 has 2 × m photodiodes PD as one block and n blocks are formed. In FIG. 1, this one block is shown by a rectangular frame, and FIG. 2 shows a specific circuit example for this one block.

The first charge transfer section 2 and the second charge transfer section 3 together form a photodiode that constitutes the light receiving element array 1.
The photocharge generated in the PD PD is transferred to the wiring capacitance CL formed between the n common signal lines 8 connecting the first and second charge transfer units 2 and 3 and the read IC 4 and the ground. It is for doing. In this embodiment, both the first and second charge transfer units 2 and 3 are thin film field effect transistors (TFTs) as switching elements.
The difference is that the first charge transfer unit 2 is connected to the previous photodiode.
In the block of the PD PD, the suffix variable a is connected to the photodiode PD having an odd number, while the second charge transfer unit 3 uses the photodiode PD whose suffix variable a is an even number. It is connected to (details will be described later).

The read IC 4 detects the potential change of the common signal line 8 due to the wiring capacitance CL for each common signal line 8 and outputs it in order to the output terminal 4a. In the present embodiment, the number of blocks is set. N common signal lines 8 corresponding to are connected to the input terminal of the read IC 4. The first and second gate pulse generators 5 and 6 as switching control means both generate a gate pulse applied to the gate of the thin film field effect transistor (details will be described later). The gate pulse generator 5 of FIG. 2 supplies the gate pulse input to the gate of the thin film field effect transistor forming the first charge transfer section 2 to the second gate pulse generator 6
Generates a gate pulse to be input to the gate of the thin film field effect transistor which constitutes the second charge transfer section 3. Control circuit 7 as operation control means
Controls the operation timings of the read IC 4, the first and second gate pulse generators 5 and 6, and controls the operating and non-operating states of the first and second gate pulse generators 5 and 6. It has functions such as setting.

Next, with reference to FIG. 2, a concrete connection example of the photodiode PD per block and the thin film field effect transistor connected thereto will be described. In one block, 2 × m photo diode PDs are provided as shown in FIG. 2, and these photo diodes P are provided.
Assuming that the suffix variables a, b, i are used for identification such as ab, i, first, for convenience, two photodiodes PD are set as a set. For example, in FIG. If you add
~ M corresponds to the suffix variable b. In each pair of two photodiodes, the photodiode PD on the right side of the paper in FIG. 2 is 1, and the photodiode PD on the left side is 2. Corresponds to the suffix variable a. Further, the suffix variable i is used as a number for identifying a block, and in FIG.
Is indicated by. The thin-film field-effect transistor is also identified by adding the Suffux variables a, b, i after T in the same manner as described above.

The cathodes of the respective photodiodes PD are connected to each other so that the power source voltage VB is applied thereto, and the thin film field effect transistor T is connected to the anode.
The drain of is connected. The source side of all the thin film field effect transistors T in one block are connected to each other, and the read ICs are connected via one common signal line 8.
4 is connected to the input terminal. In addition, the gates of the thin film field effect transistors in one block are respectively drawn out by wiring, and in other blocks, the suffix variable b is mutually connected to the gates of the same thin film field effect transistor T, First gate pulse generator 5 or second gate pulse generator 5
It is adapted to be connected to the gate pulse generator 6. That is, each thin film field effect transistor T1-1,1,
T1-1,2 ... The gate of T1-1, n is the gate signal line G1-1
In addition, each thin film field effect transistor T2-1,1, T2-1,2
..Gates of thin film field effect transistors T having the same suffix variable a and suffix variable b between blocks such that the gate of T2-1, n is connected to the gate signal line G2-1 Are the gate signal lines G1-i (i = 1 to m) and G2-i (i =
1 to m). And the suffix variable a
Is an odd number, that is, 1 is a gate signal line G1-i (i = 1 to n) to which the gate of the thin film field effect transistor T is connected.
Is a gate signal line G2-i (i = 1 to i) to which the gate of the thin film field effect transistor T having a suffix variable a of an even number, that is 2, is connected to the first gate pulse generator 5. n)
Are respectively connected to the second gate pulse generator 6.

Next, the operation of this apparatus will be described with reference to FIGS. 3 and 4. First, a case of reading a document with high resolution, that is, a case of using all the photodiodes PD constituting the light receiving element array 1 will be described with reference to FIG. First, the selection signal SE with a logical value "1" is input to the control circuit 7 from an external circuit (not shown). This selection signal SE has a high-resolution reading operation using all the photodiodes PD of the light-receiving element array 1 and a low-resolution reading operation using half of the photodiodes PDD forming the light-receiving element array 1. For example, when a logical value “1” is input, a high-resolution reading operation is performed, and when a logical value “0” is input, a low-resolution reading operation is performed. It is going to be done. That is, in the high-resolution reading operation, the control circuit 7 puts both the first and second gate pulse generators 5 and 6 into the operating state, while in the low-resolution reading operation, the control circuit 7 makes the first operation. Only the gate pulse circuit 5 is set in the operating state.

When a start pulse (abbreviated as "ST" in FIG. 3 (a)) is input to the control circuit 7 and the read IC 4 from an external circuit (not shown), a series of operations is started (FIG. 3). 3 (a)). After the start pulse is input, the first gate pulse generator 5 outputs a gate pulse ΦG1-1 in synchronization with the clock (CK) signal input via the control circuit 7 (see FIG. Three
(See (b)), the suffix variable a is 1 and the suffix variable b is in each block via the gate signal line G1-1.
Is a thin film field effect transistor T of 1, namely T1-1, i
It is applied to each of (i = 1 to n), and they become conductive.

As a result, the thin film field effect transistors T1-1, i (i = 1 to n) are connected to the wiring capacitance CLi (i = 1 to n) formed between the common signal line 8 and the ground. Charges transferred from the respective photodiodes PD1-1, i (i = 1 to n) are accumulated via the photodiodes PD1-1, i, and the potential of the common signal line 8 becomes a potential corresponding to the transferred charge amount. Then, in the read IC 4, n analog switches (not shown) provided therein are sequentially operated, so that the photodiodes PD1-1, i (i = 1 to n) are output to the output terminal 4a. ), That is, the image signals are sequentially output. Next, a gate pulse .PHI.G2-1 from the second gate pulse generator 6 is transmitted through the gate signal line G2-1 in each block, and the suffix variable a is 2 and the suffix variable b is 1. The field effect transistor T is applied to each gate of T2-1, i (i = 1 to n) (see FIG. 3 (e)). As a result, the signal corresponding to the charge generated in each photodiode PD2-1, i (i = 1 to n) through each thin film field effect transistor T2-1, i (i = 1 to n) is first. Output terminal 4 in the same manner as described in
It will be read from a.

Then, again the first gate pulse generator 5
A gate pulse ΦG1-2 is output from the gate signal line G
In each block through 1-2, suffix variable a
Is applied to each of the thin film field effect transistors T having the suffix variable b of 1 and the suffix variable b of 2, that is, T1-2, i (i = 1 to n). Then, through each thin film field effect transistor T1-2, i (i = 1 to n), each photodiode P is connected.
The image signals from D1-2, i (i = 1 to n) are sequentially read out to the output terminal 4a of the reading IC 4 in the same manner as described above. After that, the gate pulse .PHI.G2-2 is output from the second gate pulse generator 6 to read out the image signal from each photodiode PD2-2, i (i = 1 to n). I
The data is sequentially read from the output terminal 4a of C4.

Thereafter, similarly, the first gate pulse generator 5 and the second gate pulse generator 6 are alternately gated.
The pulse .PHI.G is output, and the image signal is read out from each block simultaneously for each one photodiode. Next, referring to FIG. 4, when a document (not shown) is read at a low resolution, that is, half of the photodiodes PD constituting the light receiving element array 1 are used to scan the document. The case of reading will be described. As in the case of high resolution, the start pulse is input to the control circuit 7 from the external circuit (see FIG. 4).
(See (a)), the first gate pulse generator 5
The gate pulse .PHI.G1-i (i = 1 to m) is sequentially output only from. Then, by the respective gate pulses ΦG1-i (i = 1 to m), the image signals are sequentially read from each block from the thin film field effect transistor T having the suffix variable a of 1 from i = 1. Therefore, in this case, the information amount of the image signal is half that in the case of reading at the high resolution described above. In addition, the time required for reading is halved compared to the case of high resolution.

In this embodiment, a photodiode with a suffix variable a of 1 is read when reading at low resolution.
Although the image signal is obtained from only the PD PD, the image signal may be obtained from only the photodiode PD having the suffix variable a of 2, which is essentially the same. Further, in this embodiment, two photodiodes PD are set as one set, and the photodiodes are
One of the two thin film field effect transistors T connected to the respective PDs is driven by the first gate pulse generator 5 and the other is driven by the second gate pulse generator 6, and these two gates are driven. -By setting the operation and non-operation of the pulse generators 5 and 6, a high-resolution reading operation for reading charges from all the photodiodes PD and a low-resolution reading operation for reading charges for every other photodiode PD. However, the number of gate pulse generators is increased and the desired resolution can be switched. .

In the present embodiment, the thin film transistor T constituting the first charge transfer section 2 or the second charge transfer section 3 directly connected to the photodiode PD constituting the light receiving element array 1 is replaced by the first thin film transistor T. Gate pulse generator 5 or second
It was controlled by the gate pulse generator 6 of
It goes without saying that another stage charge transfer section may be provided between the light receiving element array 1 and the first and second charge transfer sections 2 and 3.

FIG. 5 shows an example in which one more charge transfer section is provided between the light receiving element array 1 and the first and second charge transfer sections 2 and 3 as described above. This example will be schematically described with reference to FIG. 1. A batch transfer thin film transistor TT is provided between the light receiving element array 1 and the first and second charge transfer units 2 and 3. That is, the batch transfer thin film transistors TT are provided in the same number as the photodiodes PD, the drains thereof are the anodes of the photodiodes PD, and the sources are the first charge transfer section 2 or the second charge transfer portion 2. It is connected to the drain of the thin film transistor T that forms the charge transfer unit 3. Also,
The source of the batch transfer thin film transistor TT is provided with a batch transfer capacitor CT whose one end is grounded.
The charges of the photodiode PD are once stored.

Further, each batch transfer thin film transistor T.
The gates of T are connected to each other by a common wiring, and all gate transfer thin film transistors are turned on at the same time by applying a gate signal from a gate pulse generator (not shown). It has become. Since the operation of the embodiment shown in FIG. 5 is basically the same as that of the above-mentioned embodiment, the description thereof will be omitted here.

In the present embodiment, in the light-receiving element array 1 composed of a plurality of photodiodes PD, two photodiodes PD are set as one set, and one of the photodiodes PD is set as one photodiode PD. The thin film field effect transistor T connected is driven by the first gate pulse generator 5, and the thin film field effect transistor T connected to the other photodiode PD is driven by the second gate pulse generator 6. When operating the first and second gate pulse generators 5 and 6, signals are read out from all the photodiodes PD and only the first gate pulse generator 5 is operated. In this case, signals are read out from half the photo diode PDs of the light receiving element array 1, so that high resolution reading and low resolution are performed according to the resolution of the original. Since it is possible to read at low resolution, it eliminates the conventional inconvenience that it takes longer than necessary to read a low resolution original at high resolution, and it is suitable for processing until the signal reading the original is output. The time required will be shortened.

[0023]

As described above, according to the present invention,
By configuring so that a light receiving element that reads out electric charges according to a desired reading resolution and a light receiving element that does not read out electric charges can be selected, for example, when reading a low-resolution original, among all the light receiving elements, Since the reading and signal output of the original are performed in a state equivalent to thinning a certain number of light receiving elements, the processing time is shortened compared to the conventional case, and the reading resolution can be changed according to the resolution of the original. Therefore, it is possible to provide an image reading apparatus having good operation efficiency.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a schematic configuration of an image reading apparatus according to the present invention.

FIG. 2 is a circuit diagram showing an example of a specific circuit per block in the schematic diagram shown in FIG.

FIG. 3 is a timing chart for explaining an operation when reading at high resolution.

FIG. 4 is a timing chart for explaining an operation when reading at low resolution.

FIG. 5 is a circuit diagram showing another embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light receiving element array, 2 ... 1st charge transfer part, 3 ...
A second charge transfer section, 5 ... a first gate pulse generator,
6 ... Second gate pulse generator, 7 ... Control circuit

Claims (1)

[Claims] 1. An image sensor comprising a plurality of light receiving elements, a plurality of switching elements each provided on an output side of the plurality of light receiving elements for transferring charges generated in the light receiving elements, and a plurality of the switching elements. Switching control means for controlling operation, which is connected to a plurality of light receiving elements at a constant number of light receiving elements, and operation control for controlling operation and non-operation of each of the plurality of switching control means An image reading apparatus comprising: