JPH05236211A - Picture reader - Google Patents

Abstract

PURPOSE:To improve the resolution at one side reading by changing number of effective picture elements of an image sensor to be read or changing the carrying speed depending on whether both of front and rear sides of an original are read or the one side is read. CONSTITUTION:A CCD of 2048 picture element level is used for CCD image sensor units 1a, 1b on the front side and the rear side to form the units and when both sides of the original are read with a resolution of 200dpi, the unit employing a 5000 picture element level CCD is used in place of the front side read unit 1a. Then, only a command selecting only a front side picture signal is sent to a synthesis/separation circuit 3 comprising analog switches, and a half speed command is sent to an original feed motor control/drive circuit 9. Thus, the front side of the original is read by a resolution of 400dpi and the resolution is doubled. In this case, a sensor discriminating both sides or one side is provided to a carrier line to replace the sensor unit automatically.

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, and more particularly, to an image reading apparatus which continuously conveys sheet-like originals and reads both sides or one side of an original image by image sensors provided above and below the conveying path. ..

[0002]

2. Description of the Related Art Various image information file apparatuses have been put into practical use in which image information is stored in a file medium such as an optical disk or a magneto-optical disk, and if necessary, retrieved, read image information is reproduced, and printed or displayed. ..

As a high-speed and simple input means for a double-sided original document to such an image information file device, each CCD image sensor is arranged above and below a conveying path for conveying a sheet-like original document, and both front and back sides of the double-sided original document are arranged. 2. Description of the Related Art An image reading device that continuously reads in one scanning line and performs a predetermined process has been put into practical use.

[0004]

However, in the above-mentioned conventional example, when reading both sides, as shown in FIG. 3 (A), the image data on both the front and back sides are continuously read to form one scanning line. Therefore, when reading a one-sided original, as shown in FIG. 3B, after reading both sides once within one scanning line, the front side (that is, the first half of one scanning line) or the back side (that is, one scanning) is read. Only the latter half of the line) is selected as a valid image, and the data on the unnecessary side is discarded.

As described above, in the conventional example, the period which is twice as long as the period required to actually read the one-sided original is set as the CCD drive period, and half the period is wasted. That is, the single-sided reading function is merely provided as an additional function of double-sided reading, and the reading resolution is exactly the same even when reading one side, and the performance of the apparatus itself cannot be fully exhibited. was there.

Therefore, in view of the above points, an object of the present invention is to provide an image reading apparatus with a double-sided reading function, which is configured so as to obtain an optimum use mode even at the time of single-sided reading.

[0007]

In order to achieve such an object, the present invention comprises a conveying means for conveying an original, and a pair of image sensors installed on both front and back sides of the original conveyed by the conveying means. When reading both sides of the original, first reading means for sequentially reading the image signals of the original from the pair of image sensors and synthesizing and outputting the signals in one scanning line period, and only one side of the original In the case of reading, the second reading means for outputting the output of the image sensor on the one side as a signal for the one scanning line period is provided.

Here, the case of reading both front and back sides of the original,
Depending on the case where one side of the document is read, the configuration in which the number of effective reading pixels of the image sensor is changed, or when both the front and back sides of the document are read and when one side of the document is read,
By adopting a configuration in which the document conveyance speed is changed, it is possible to increase the resolution during single-sided reading.

[0009]

According to the above-described structure of the present invention, when reading one side of an original, a read signal can be arbitrarily formed within a range included in one scanning line period when reading both sides of an original. The resolution can be increased by increasing the number of effective pixels.

[0010]

Embodiment 1 FIG. 1 is a block diagram showing the basic construction of an embodiment of the present invention. In the figure, 1a and 1b are CCs for simultaneously reading the front and back sides of a sheet-like document being conveyed.
It is a D image sensor unit. The image sensor units 1a and 1b can be easily removed and can be replaced in units. Therefore, a unit to which a CCD image sensor having a different number of pixels is attached is prepared in advance and can be selected according to the application.

Reference numeral 2 is a CCD drive control circuit for operating the two CCD image sensor units 1a and 1b. 3 is two CCD image sensor units 1
In order to combine or separate the analog image data from a and 1b, a combination of analog switches is used.
It is a separation circuit. Reference numeral 4 denotes an internal circuit after A / D (analog / digital) conversion of the analog image data from the synthesizing / separating circuit 3 into digital multi-valued image data and further performing necessary digital image processing for image quality improvement. 2 is an image binarization circuit that binarizes the digital comparator.

Reference numeral 5 denotes an image data compression / expansion circuit that encodes and compresses an image when reading an original and expands the image for decoding when the image is reproduced. A compressed image data file device 6 stores the image data coded and compressed by the image data compression / expansion circuit 5. 7
Is an image display device for displaying a read image at the time of reading, and displaying a reproduced image which is searched by the image data file device 6 and decoded and expanded by the image data compression / expansion circuit 5 at the time of image reproduction.

Reference numeral 8 is an original feed motor for continuously conveying sheet-like originals, and 9 is an original feed motor control / drive circuit for controlling and driving the original feed motor. Reference numerals 10a and 10b are fluorescent lamps which are light sources for illuminating the front and back surfaces of the original to be read, and 11 is a fluorescent lamp 10a and
This is a fluorescent lamp control circuit for illuminating a document, which controls the light amount of 10b.

FIG. 2 shows the details of the document reading section included in the basic configuration of this embodiment. In this figure, the two-sided (or one-sided) original document 26 conveyed along the space between the conveyance guides 22a and 22b by each of the two pairs of conveyance rollers 20a, 20b, 20c and 20d is physically provided at substantially the same position. Read by the reading unit. The image (reflected light) on the surface of the document 26 is read glass 21a and total reflection mirror plate 23.
The image is projected and imaged on the CCD image sensor 25a for surface reading through an optical path passing through a and the imaging lens 24a. On the other hand, the image (reflected light) on the back surface of the original 26 is read glass 21b, total reflection mirror plate 23b, and imaging lens 2
The image is projected and imaged on the back surface reading CCD image sensor 25b through an optical path passing through 4b.

FIGS. 3 and 4 show the CC in this embodiment.
Timing showing the driving timing of the D image sensor
It is a chart. In addition, an explanatory diagram showing the correspondence between the composite image and the actual image is added to the lower side of both figures.

In FIGS. 3 and 4, SH1 is a synchronizing signal for starting the output of a pixel row to the front surface reading CCD image sensor unit 1a. From the rising edge e1, the front surface reading CCD image sensor 1a.
The output of the pixel column is started from, and the effective pixel signal is output during the period t1. Further, the synchronization signal SH2 is output to the back surface reading CCD image sensor unit 1b, and the output of the pixel row is output from the back surface side CCD unit 1b from the rising edge e2 of this signal SH2 during the section t2. ..

Here, FIG. 3A is a timing chart at the time of reading a double-sided original normally, and section t3 is C for the front side.
In the vicinity of the conversion point P1 of the effective pixel section t1 of the CD 1a and the effective section t2 of the back CCD 1b, both effective signals are switched by an analog switch, and a combined image output section is shown as one combined image signal.

Conventionally, in a document reading apparatus capable of double-sided reading, combining front and back image signals, and processing by a single image processing system, in order to alternately combine front and back image signals, the synchronization signal is used. The cycles of SH1 and SH2 are set to be twice or more of t1 and t2 in the period required to actually output the signal of the effective pixel column, and when reading a single-sided original,
As shown in FIG. 3B, the effective pixel output section t1 or t2 can be output in a cycle that is half or less of the cycle of the CCD synchronization signal SH1 or SH2. That is, by outputting the pixel output of either one of the front and back sides as it is as a composite image, the image signal is output only in the first half in the section t4.
The second half is an invalid section in which the image signal is not output.

Therefore, in the present embodiment, in the case of single-sided document reading, the CCD image sensor unit 1a or 1b for reading the document on either the front side or the back side has twice the number of pixels as the unit used when reading the double-sided document. CCD with
Even if it is converted into an image sensor unit,
As shown in the timing chart of (A), it is possible to output a signal of a maximum of double pixel rows from the CCD for a period t4 without any modification to the synchronization signal SH1 or SH2 applied to the CCD image sensor. You can

That is, since the original having the same width is read by the CCD having a maximum of twice the pixel row, the resolution can be improved to a maximum of two times in the main scanning direction. In addition, the document feeding speed must be at least 1 for double-sided scanning.
If it is set to / 2, the resolution in the sub-scanning direction can be doubled at the maximum.

As described above, when both sides of the document are read, both sides of the CCD image sensor units 1a and 1b are constructed by using CCDs of 2048 pixel level so that the original can be read at the resolution of 200 dpi. In a document reading apparatus based on
The D image sensor unit 1a is replaced with a unit using a CCD of 5000 pixel level, and a command for selecting only the image signal on the surface is sent to the combining / separating circuit 3 composed of analog switches, and the document is fed. Motor control /
By sending a half speed command to the drive circuit 9, it is possible to configure an original reading device capable of reading one surface of the original at a resolution of 400 dpi.

Further, when the image sensor unit is replaced, a sensor for determining whether the original is double-sided or single-sided may be provided in advance in the conveyance path, and the unit may be automatically replaced according to the determination. It may be possible to manually replace it according to the above.

As described above, in the double-sided image reading apparatus configured so that the image signals of the front and back are combined and the image processing system after reading is completed by one system, the reading CC
By replacing the D image sensor unit with a unit using a CCD having a different number of pixels, an image reading device having two types of operation modes is configured, so that the circuit configuration or the like is not changed and one side At the time of reading, it is possible to improve the reading resolution up to 2 times.

Of course, as shown in FIG.
By preparing a unit composed of a CCD image sensor of 0 pixel, 2300 pixel, 2500 pixel, 3600 pixel, etc. in advance, replacing it at the time of reading a single-sided original, and adjusting the original feeding speed according to the number of each pixel. , It becomes possible to read the original at each resolution.

Embodiment 2 FIG. 5 is a block diagram showing the basic construction of another embodiment of the present invention. In the first embodiment shown in FIG. 1, when the resolution of a single-sided original is read at a higher resolution, the CCD image sensor unit has been replaced by another unit, but the second embodiment shown in FIG. Then the number of pixels is 2 in advance
The same effect is realized by using a CCD image sensor that can be switched in stages.

The second embodiment will be described in detail below with reference to FIGS. Here, FIG. 6 and FIG.
FIG. 6 is a timing chart for explaining the operation of the CCD image sensor used in the second embodiment shown in FIG.

In the present embodiment, as a means for switching the resolution between double-sided scanning and single-sided scanning, as shown in FIGS. 6 and 7, by switching between the channel separation mode and the channel synthesis mode of the CCD image sensor. There is. That is, in the CCD image sensor used in the present embodiment, the odd-numbered and even-numbered read effective pixel columns are arranged in a staggered pattern, and the odd-numbered pixel output and the even-numbered pixel output are separately output. A CCD that can switch the channel separation mode and the channel combination mode for outputting the combined output of both is externally used.

First, when reading both sides, the CCD is operated in the channel separation mode for both the front and back sides. For example, 500
When a CCD image sensor with 0 pixels is used, as shown in FIG. 6, if only even pixel outputs are used as outputs for both the front and back sides, the number of effective pixels is 5000/2 = 2500.
Image information for pixels is set to 5 in channel composition mode.
It is possible to output the image information for 000 pixels in a half period of time.

CCD in this channel separation mode
The operation of the image sensor will be described in detail with reference to the timing chart of FIG. 6 and the CCD image sensor of FIG.

If only even pixel outputs are used as outputs on both the front and back sides, the output of the shift register 2 becomes an output in which every other odd pixel output is missing, as shown in FIG. Although the number of effective pixels of this output is 5000/2 = 2500 pixels, the time required to output 2500 pixels is the same as the time required to output when the number of effective pixels is 5000 pixels. Therefore, the CCD image sensor used in the present embodiment is provided with the shift register 3 as shown in FIG. Pixels are output in which pixels are arranged side by side. Therefore, the output of the shift register 3 is 1/2 the time required to output 2500 pixels, as shown in FIG.

That is, as in FIG. 3A of the first embodiment, SH
During one cycle of 1 and SH2 (that is, the time to output the image information of 5000 pixels in the channel combination mode), it is possible to combine the image information of 2500 pixels on each of the front and back sides to form one line, and both sides It is possible to configure a device that reads a document with a resolution of 200 dpi.

Next, when reading a single-sided original, the CCD on either the front side or the backside is operated in the channel combination mode. In this case, as shown in FIG. 7, since the odd-numbered and even-numbered pixels are fully output from the one-sided CCD, the number of effective pixels of the signal output during one cycle of SH1 or SH2 is 5000 pixels. Becomes In this state, if an instruction to make the document feed motor 8 shown in FIG. 5 a speed that is 1/2 of that in double-sided scanning is output, FIG.
As in the case of replacing the CCD image sensor unit, one side of the front or back document is 400dp
A device that reads at a resolution of i can be configured. Needless to say, the image processing system after reading can obtain the same effect with the same configuration as that of the first embodiment.

FIG. 8 shows the structure of a CCD image sensor used in this embodiment, which is capable of channel separation and channel composition switching.

In the timing chart shown in FIG. 6, only even-numbered outputs are used in the separation mode, but it goes without saying that only odd-numbered outputs can be used.

[0035]

As described above, according to the present invention, in contrast to double-sided image reading in which both front and back sides of a document are read within one scanning line period, when one side of the document is read, for example, the effective number of read pixels of the image sensor is set to both sides. It is possible to improve the reading resolution up to 2 times without making any structural change by changing the reading resolution up to twice or up to 1/2.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an image reading apparatus that is a first embodiment of the present invention.

FIG. 2 is a sectional view showing details of an image reading unit in the present embodiment.

FIG. 3 is a diagram for explaining the operation of this embodiment.

FIG. 4 is a diagram for explaining the operation of this embodiment.

FIG. 5 is a block diagram showing a basic configuration of a second embodiment of the present invention.

FIG. 6 is a timing chart at the time of outputting the channel separation mode (when reading a double-sided original).

FIG. 7 is a timing chart at the time of outputting the channel combination mode (at the time of reading a single-sided document with high resolution).

FIG. 8 is a diagram showing a structure of a CCD image sensor for channel separation / channel combination mode switching.

[Explanation of symbols]

 1a Front-side reading CCD image sensor unit 1b Back-side reading CCD image sensor unit 2 CCD drive / control circuit 3 Combining / separating circuit 4 Image binarization circuit 8 Original feed motor 9 Original feed motor control / drive circuit

Claims (3)

[Claims] 1. A conveying means for conveying an original, a pair of image sensors respectively installed on both front and back sides of the original conveyed by the conveying means, and when reading both sides of the original, the pair of images is read. First reading means for sequentially reading the image signals of the original from the sensor and synthesizing and outputting the signals in one scanning line period; and when reading only one side of the original, the image sensor output of the one side is referred to as the one An image reading apparatus comprising a second reading means for outputting as a signal of a scanning line period. 2. The image reading apparatus according to claim 1, wherein the number of effective reading pixels of the image sensor is changed depending on whether the front and back sides of the original are read or the single side of the original is read. 3. The image reading apparatus according to claim 1, wherein the feeding speed of the original is changed depending on whether the front and back sides of the original are read or the single side of the original is read.