JPH0575780A - Picture reader - Google Patents

Abstract

PURPOSE:To quicken a reading speed without changing a light storage time by summing picture element outputs of n-sets of solid-state image pickup elements adjacent to each other and outputting the sum when a picture is read with a resolution being 1/n of a highest resolution. CONSTITUTION:Coding picture data stored on a magneto-optical disk device 17 are read by a SCSI bus transfer control circuit 13 via a SCSI bus 14 and stored tentatively in a picture data buffer RAM 12 by a picture data transfer control circuit 15. Then coded picture data are read from the RAM 12 by the circuit 15, fed to a picture data expansion circuit 11, in which the data are subjected to decoding expansion processing. At reproduction output, since an input changeover circuit 9 is thrown to the position of the circuit 11, decoded original binary picture data are fed to a picture display device 16 via the circuit 9, on which the reproduced picture is displayed. Thus, read speed is quickened more without changing the light storage time.

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 for reading originals by a collective image pickup element, and more particularly to an image reading apparatus for continuously reading sheet-like originals conveyed by a solid-state image pickup element at high speed. is there.

[0002]

2. Description of the Related Art An image information file device for converting image information into a digital signal, storing and storing it in a file medium such as an optical disk or a magneto-optical disk, searching as necessary, reproducing the read image information, and printing or displaying. Various proposals have been made and put to practical use.

In such an image information file device, a group image pickup device, for example, a CCD having a large number of pixels is usually used.
The original image is read by the image sensor at 400 dpi (dot).
In many cases, an image information file device having a high fidelity of an image to be read and output is stored in an external file device, stored and stored in an external file device, searched, and output with high resolution. On the other hand, the capacity of the current external file device such as a magneto-optical disk is still insufficient for accumulating and storing a large amount of original images read at a high resolution of 400 dpi or more. Further, in order to increase the input speed of the original image, there are many applications in which a large amount of image information is stored and stored at high speed even if the image quality is slightly degraded.
It will be read at a low resolution of 200 dpi or less. Therefore, in the actual image information file device, the reading resolution of the original image is, for example, 400 dpi or 200 dpi.
In general, it is configured so that it can be selected by switching to either i or 100 dpi.

That is, in order to construct an image reading apparatus in which a plurality of image reading resolutions can be switched and selected, a CCD image sensor having a high number of pixels corresponding to the highest resolution among a plurality of selectable resolutions is prepared and a low resolution is provided. When reading at the resolution, in the main scanning direction, unnecessary pixel outputs among the pixel outputs sequentially output from the CCD image sensor are thinned to obtain a predetermined low resolution, while in the sub scanning direction, the original image and the CCD are obtained. It is common to deal with the problem by increasing the relative moving speed between the image sensors.

[0005]

However, in the above-mentioned conventional example, as a method of lowering the resolution on the main scanning side, all the pixels of the CCD image sensor are once read at the highest resolution, and then unnecessary pixels are thinned out and discarded. Since this method is adopted, the use efficiency of the pixels of the CCD image sensor is reduced, which is a major limitation when increasing the reading speed during low-resolution reading. For example, if the same original is 400 dp
Considering the case of reading at two different resolutions, i and 200 dpi, in the case of 200 dpi, it is 1/4 of the total number of read pixels compared to the case of 400 dpi.
If all the pixels of the D image sensor are used efficiently, the speed on the sub-scanning side should be quadrupled. However, in this case, as described above, when scanning on the main scanning side, half of the pixels
Is discarded, the speed on the sub-scanning side can actually be increased only twice. Here, if the driving clock frequency of the CCD image sensor is doubled, the speed on the sub-scanning side can be quadrupled, but in this case, the light accumulation time of each pixel of the CCD image sensor is 1 /
It becomes 2. Therefore, as a countermeasure against this, it is necessary to double the irradiation light amount of the document, which not only causes an increase in cost, but also increases the sub-scanning side, that is, the document reading speed when the light source has no margin. Is impossible.

An object of the present invention is to solve the above-mentioned problems and to provide an image reading apparatus capable of increasing the reading speed without changing the light accumulation time.

[0007]

In order to achieve such an object, the present invention provides a solid-state image pickup device for reading an original image,
In an image reading apparatus having a resolution switching means for switching the image reading resolution by the solid-state imaging device to any one of a plurality of predetermined image reading resolutions, a resolution of 1 / n (n is a positive integer) of the maximum resolution. When reading, the synthesizing means is provided for adding and synthesizing outputs of n adjacent pixels of the solid-state image sensor.

[0008]

In the present invention, when reading at a resolution of 1 / n (n is a positive integer) of the highest resolution, the synthesizing means adds and synthesizes the outputs of n adjacent pixels of the solid-state image pickup device and outputs the result.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

In the figure, reference numeral 1 is a CCD image sensor for reading a sheet-like document p. Reference numeral 2 denotes a light source that illuminates the surface of the original, and is controlled by a light amount control circuit (not shown) so that the light amount is always constant. A CCD drive timing control circuit 3 is an MPU (not shown).
(Microprocessor unit) Each signal group described later is supplied in accordance with the reading resolution designated by the bus. Four
Reference numerals a and 4b respectively denote transport rollers for transporting a sheet-shaped document, and 5 denotes a document feeding motor. Reference numeral 6 denotes a document feed motor control / drive circuit, which controls the motor so as to feed a document at a constant transport speed designated by an MPU bus (not shown). 7 is a CCD image sensor 1
It is an amplifier that amplifies the analog image signal read by the device to a required level. Reference numeral 8 denotes an image binarization circuit, which performs A / D (analog / digital) conversion of the analog image signal amplified by the amplifier 7 to convert it into digital multi-valued image data, and a digital image necessary for image quality improvement. After performing processing (for example, shading correction, edge enhancement processing, etc.), binary image data is finally generated by a digital comparator or the like. An input switching circuit 9 selects one of the binary image data of two systems and outputs it to the next stage. Reference numeral 10 is an image data compression (encoding) circuit,
The binary image data selected by the input switching circuit 9 is subjected to encoded data compression processing. An image data decompression (decoding) circuit 11 decodes the coded image data to restore and reproduce the original binary image data. Reference numeral 12 denotes a (coded) image data buffer RAM for temporarily storing and recording the coded image data output from the image data compression circuit 10. 13 is SC
A SCSI bus transfer control circuit that controls data transfer with an SI (Small Computer System Interface) bus, and 14 is a SCSI bus that finally outputs encoded image data. An image data transfer control circuit (DMA transfer control circuit) 15 controls transfer of encoded image data between the above devices. An image display device 16 reproduces a visible image by developing a binary pixel data string two-dimensionally.

Next, the operation of the apparatus of this embodiment will be described.

The analog image data read by the CCD image sensor 1 is amplified to a required signal level by an amplifier 7, and then the analog image data is A / D converted by an image binarization circuit 8 to obtain a digital multi-valued image. Converted to data. Further, after performing necessary digital image processing for improving image quality, binarization processing is performed.

At the time of reading the original, the input switching circuit 9 causes the CC
Since it is connected to the binary image data side of the D image sensor side, the monitor image is sequentially displayed on the image display device 16 based on the image data continuously read by the CCD image sensor, and simultaneously read. The image data is sent to the image data compression circuit 10 and is encoded and compressed. As a coding method, MH (Mo
defined Huffman) method, MR (Modif
ied Read method, MMR (Modified)
MR) method or the like can be used.

The encoded image data generated by the image data compression circuit 10 is temporarily stored and stored in the image data buffer RAM 12 under the control of the image data transfer control circuit 15. After the completion of reading one original, the image data transfer circuit 15 again controls the data to be read from the image data buffer RAM 12, sent to the SCSI bus transfer control circuit 13, and finally output to the SCSI bus 14. , Are stored and stored on the magneto-optical disk device 17.

Next, the operation of reading the coded image data accumulated and stored on the magneto-optical disk device 17 will be described.

First, the encoded image data accumulated and stored in the magneto-optical disk device 17 is read by the SCSI bus transfer control circuit 13 via the SCSI bus 14, and is controlled by the image data transfer control circuit 15 to be used for image data. It is temporarily stored in the buffer RAM 12. Next, the coded image data is read from the image data buffer RAM 12 under the control of the image data transfer control circuit 15 and sent to the image data expansion circuit 11 where it is decoded and expanded.

At the time of image reproduction and output, the input switching circuit 9 is connected to the side of the image data expansion circuit 11, so that the decoded original binary image data is sent to the image display device 16 via the input switching circuit 9 to display an image. The reproduced image is displayed on the device 16.

The above is the basic operation of the image reading apparatus of the present embodiment at the time of reading an image and reproducing and outputting a stored image.

Next, the driving timing of the CCD driving timing control circuit 3 when the reading resolution of the image reading apparatus of this embodiment is changed will be described in detail.

FIG. 2 is an explanatory view of a CCD driving system according to the embodiment of the present invention, and FIG. 2A shows a CCD at the time of high resolution reading.
FIG. 2B shows a drive pulse waveform group, and FIG. 2B shows a CCD drive pulse waveform group at a low resolution (half the resolution at a high resolution).

The signal charge corresponding to the accumulated light amount of each pixel is
It is transferred to the next stage at the change points of the CCD drive clocks φ1 and φ2, and finally sent from the transfer unit of the CCD to the output unit.
The analog signal charge accumulated in the output section is sampled at the rising edge of the reset pulse and sent to the next stage.
Next, the analog signal charge accumulated in the output section is released during the reset pulse period, and preparation for receiving the next signal charge is performed.

At low resolution (that is, half the resolution of high resolution), twice the frequency (1
Since the reference clock of (/ 2 cycle time) is given to the CCD drive timing control circuit 3, the cycle of the CCD drive pulses φ1 and φ2 is halved, and the output rate of the signal charges is doubled. On the other hand, the reset pulse for releasing the signal charge accumulated in the output section is output at a ratio of 1 pulse to the signal charge output for two pixels in order to maintain the same timing as that at the time of high resolution. Therefore, as a result, in the output section, the signal charge outputs of two adjacent pixels are added and combined and output to the next stage.

On the other hand, since the frequency of the reference clock is doubled, the period of the shift start pulse is naturally halved, and the light accumulation time (lux / sec) for each pixel is 1/2.
Therefore, it is possible to keep the light accumulation time after the addition synthesis of the two pixel signal charge outputs relatively the same. Also, 2
By adding and synthesizing the individual pixel signal charge outputs, the output rate of the image data to the circuit of the next stage can be kept the same as that at the time of high resolution even though the reference clock is doubled. At the same time, the speed on the sub-scanning side (that is, the document conveying speed) is set to 4 (= 2 ² ) times as high as that at the high resolution, so that the resolution on the sub-scanning side can be made to correspond to the main scanning side. Therefore, in this case, the document feed motor control / drive circuit 6 controls the motor 5 to convey the document at a speed four times as high as that at the time of high resolution.

[0025]

As described above, according to the present invention,
When reading at the resolution of 1 / n of the highest resolution, the output of n adjacent pixels of the solid-state image sensor is added and combined and output, so the reading speed can be increased without changing the light accumulation time. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart for explaining a CCD driving system according to the embodiment of the present invention.

[Explanation of symbols]

 1 original reading CCD image sensor 2 original irradiation light source 3 CCD driving timing control circuit 5 original feeding motor 6 original feeding motor control / drive circuit 8 image binarization circuit 9 input switching circuit 10 image data compression circuit 11 image data Decompression circuit 15 Image data transfer control circuit 16 Image display device

Claims (3)

[Claims] 1. An image reading apparatus having a solid-state image sensor for reading an original image and resolution switching means for switching the image-reading resolution by the solid-state image sensor to one of a plurality of predetermined image reading resolutions. When reading at a resolution of 1 / n of the resolution (n is a positive integer), an image reading apparatus is provided with a synthesizing unit that adds and synthesizes outputs of n adjacent pixels of the solid-state image sensor. .. 2. The synthesizing means according to claim 1, when the image is read at the highest resolution, applies a reset pulse for discharging electric charge to each pixel output of the solid-state image pickup device to obtain 1 / n (of the highest resolution). When reading an image with a resolution of (n is a positive integer), the reset pulse is applied only once for every n pixel outputs. 3. The combination means according to claim 1, wherein when the image is read at a resolution of 1 / n of the maximum resolution, n adjacent pixels are combined and added, and at the same time, the solid-state image sensor is at the maximum resolution. An image reading device characterized by being driven at a drive clock frequency of n times.