JP2008227989A - Document reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document reader in which both sides of a document can be read using two line sensors and whose manufacturing costs are further reduced. <P>SOLUTION: Both sides of the document are read using a CCD line sensor for the front side and a CCD line sensor for the rear side. A first output term T1 during which an SH pulse is output to the CCD line sensor for the front side, and a second output term T2 during which an SH pulse is output to the CCD line sensor for the rear side, are alternately switched and in response to switching timing, a transfer pulse output from one transfer pulse output section is input to a shift register for the front side and a shift register for the rear side while being switched alternately. Thus, it is not necessary to separately provide transfer pulse output sections for outputting transfer pulses to the shift register for the front side and the shift register for the rear side, and the manufacturing costs can be further reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a document reading apparatus, and more particularly to a document reading apparatus capable of reading both sides of a document.

  As a document reading apparatus capable of reading both sides of a document, in addition to one that sequentially reads the front and back surfaces of the document by reversing the front and back using a single line sensor, What can read both sides in parallel using a line sensor is known. An original reading apparatus capable of reading both sides of an original in parallel using two line sensors can read the original at a higher speed than a configuration in which the original is turned upside down.

  In the document reading apparatus provided with such two line sensors, light is irradiated on the front and back surfaces of the document, and the reflected light from the front surface is accumulated for each line by one line sensor and photoelectrically converted. The line light can be generated for both sides of the document by accumulating the reflected light from each line by the other line sensor and performing photoelectric conversion (for example, Patent Document 1). Each line data of the front and back sides of the document generated in this way is input from each line sensor to the corresponding shift register, and each line data of the front and back sides is alternately transferred from these shift registers to one line. It is synthesized every time. The synthesized line data is converted into a digital value by an A / D converter, and image processing such as compression processing is performed.

  FIG. 5 is a block diagram showing an example of a conventional document reading apparatus. This document reading apparatus includes a front surface CCD (Charge Coupled Devices) unit 104A for reading the front surface of a document, and a back surface CCD unit 104B for reading the back surface of the document, and uses these CCD units 104A and 104B. Thus, both sides of the document can be read in parallel.

  The front surface CCD unit 104A includes a front surface CCD line sensor 141A that receives reflected light from the surface of the document, and a front surface shift register 142A that receives line data generated by the front surface CCD line sensor 141A. Is provided. On the other hand, the back surface CCD unit 104B receives the reflected light from the back surface of the original, and the back surface CCD line sensor 141B and the back surface shift register 142B to which the line data generated by the back surface CCD line sensor 141B is input. And are provided.

  In this example, the front surface CCD unit 104A and the rear surface CCD unit 104B are driven by different drive circuits. That is, the front surface CCD unit 104A is driven by the front surface CCD drive circuit 140A, and the back surface CCD unit 104B is driven by the back surface CCD drive circuit 140B. The front surface CCD drive circuit 140A includes a front surface SH (Shift) pulse output unit 143A and a front surface transfer pulse output unit 144A. On the other hand, the back surface CCD drive circuit 140B includes a back surface SH pulse output unit 143B and a back surface transfer pulse output unit 144B.

  The front surface SH pulse output unit 143A outputs an SH pulse at a predetermined reading cycle that defines the light accumulation time for one line in the front surface CCD line sensor 141A. That is, when the SH pulse is output from the front surface SH pulse output unit 143A, line data is input from the front surface CCD line sensor 141A to the front surface shift register 142A, and the accumulated charge of the front surface CCD line sensor 141A is reset. Thereafter, the reflected light from the next line of the document is accumulated in the front surface CCD line sensor 141A until the next SH pulse is input in the reading cycle. The back surface SH pulse output unit 143B outputs SH pulses at a predetermined reading cycle that defines the light accumulation time for one line in the back surface CCD line sensor 141B in the same manner as the front surface SH pulse output unit 143A.

  The front surface transfer pulse output unit 144A outputs the transfer pulse to the front surface shift register 142A, thereby transferring the line data input from the front surface CCD line sensor 141A to the front surface shift register 142A to the synthesis circuit 145. On the other hand, the back surface transfer pulse output unit 144B outputs the transfer pulse to the back surface shift register 142B, thereby transferring the line data input from the back surface CCD line sensor 141B to the back surface shift register 142B to the combining circuit 145. . By alternately transferring line data from the front-side shift register 142A and the back-side shift register 142B, the synthesis circuit 145 can synthesize the line data on the front and back sides of the document for each line. The line data synthesized by the synthesis circuit 145 is digitized by the A / D conversion circuit 149, and image processing such as compression processing is performed in the image processing circuit 147.

  FIG. 6 is a waveform diagram of the SH pulse and the transfer pulse that are output when both sides of the original are read by the original reading apparatus of FIG. In this example, as shown in FIGS. 6A and 6C, the front-side SH pulse output unit 143A and the rear-side SH pulse output unit 143B alternately output SH pulses at the same reading cycle TR. .

  When the SH pulse is output from the surface SH pulse output unit 143A, the line data generated by photoelectrically converting the light accumulated in the surface CCD line sensor 141A from the previous SH pulse output until then, Input from the front surface CCD line sensor 141A to the front surface shift register 142A. Therefore, as shown in FIG. 6B, when the SH pulse is output from the surface SH pulse output unit 143A, the transfer pulse is not output from the surface transfer pulse output unit 144A.

  Similarly, when an SH pulse is output from the back-side SH pulse output unit 143B, a line generated by photoelectrically converting light accumulated in the back-side CCD line sensor 141B from the previous SH pulse output until then. Data is input from the back surface CCD line sensor 141B to the back surface shift register 142B. Therefore, as shown in FIG. 6D, when the SH pulse is output from the back surface SH pulse output unit 143B, the transfer pulse is not output from the back surface transfer pulse output unit 144B.

Here, the period at which the SH pulses are output from the front surface SH pulse output unit 143A and the rear surface SH pulse output unit 143B can be changed according to the reading resolution of the document. That is, by increasing the reading cycle TR as the original reading resolution is set higher, the data amount for one line photoelectrically converted by the CCD line sensors 141A and 141B is increased, and the original reading resolution is set lower. By shortening the reading cycle TR, the data amount for one line that is photoelectrically converted by the CCD line sensors 141A and 141B can be reduced.
Japanese Patent Laid-Open No. 7-58945

  However, the conventional document reading apparatus as shown in FIGS. 5 and 6 has a problem that two driving circuits must be provided to drive the front surface CCD unit 104A and the rear surface CCD unit 104B, respectively. . That is, the front-side transfer pulse output unit 144A outputs a transfer pulse to the front-side shift register 142A when the front-side SH pulse output unit 143A does not output the SH pulse, and the rear-side SH pulse output unit 143B outputs the SH pulse. There is a problem in that a back-side transfer pulse output unit 144B that outputs a transfer pulse to the back-side shift register 142B when it is not output must be provided separately.

  Further, when different reading resolutions are set for the front surface and the back surface of the document, it is necessary to change the cycle of outputting the SH pulses from the front surface SH pulse output unit 143A and the back surface SH pulse output unit 143B. Therefore, there is a problem that the front surface SH pulse output unit 143A and the rear surface SH pulse output unit 143B must be provided separately.

  As described above, when the two drive circuits are provided to drive the front surface CCD unit 104A and the rear surface CCD unit 104B, there is a problem that the manufacturing cost of the document reading apparatus increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an original reading apparatus that can read both sides of an original using two line sensors and can reduce manufacturing costs. .

  A document reading apparatus according to a first aspect of the present invention irradiates light on the front and back surfaces of a document, accumulates reflected light from the surface for each line by a first line sensor, performs photoelectric conversion, and generates by the photoelectric conversion. The input line data is input to the first shift register, and the reflected light from the back surface is accumulated for each line by the second line sensor to perform photoelectric conversion, and the line data generated by the photoelectric conversion is shifted to the second shift register. A document reading apparatus that generates image data on both sides of a document by inputting the data into a register and converting the line data into a digital value. The document reading device performs SH processing on the first and second line sensors at the same reading cycle. SH pulse output means for outputting a pulse and a transfer pulse for transferring the line data input to the first and second shift registers. Transfer pulse output means, wherein the SH pulse output means alternately switches between a first output period and a second output period each comprising a half period of the reading cycle, and the first output period is set as a pulse width. A first SH pulse is output to the first line sensor, a second SH pulse having a pulse width of the second output period is output to the second line sensor, and the transfer pulse output means is in the first output period. A transfer pulse is output to the second shift register and a transfer pulse is output to the first shift register during the second output period.

  According to such a configuration, the first output period for outputting the first SH pulse to the first line sensor and the second output period for outputting the second SH pulse to the second line sensor are alternately switched, and the switching timing is switched. Accordingly, transfer pulses output from one transfer pulse output means can be switched and input to the first and second shift registers alternately. In this way, both line data of the front and back sides of the document input to the first and second shift registers are transferred based on the transfer pulse, so that both sides of the document can be read using two line sensors. it can. Further, since it is not necessary to separately provide transfer pulse output means for outputting transfer pulses to the first and second shift registers, the manufacturing cost can be further reduced.

  In addition to the above-described configuration, the document reading apparatus according to the second aspect of the present invention includes reading resolution setting means for setting the reading resolution of the front and back sides of the document, and different reading resolutions for the front and back sides of the document by the reading resolution setting means. Is set, the image data of the reading surface on which the reading resolution is set lower among the image data on the front surface and the back surface of the original document transferred from the first and second shift registers and digitized. And a resolution converting means for reducing the resolution in the scanning direction.

  According to such a configuration, even when different reading resolutions are set for the front surface and the back surface of the document, the first and second line sensors are output without changing the cycle of outputting the SH pulse. The resolution in the sub-scanning direction of the image data on the reading surface set to a lower reading resolution among the image data on the front surface and the back surface of the document transferred from the second shift register and digitized can be reduced. . Therefore, unlike the configuration in which the cycle of outputting the SH pulse to the first and second line sensors is changed, the SH pulse can be output at a constant cycle by using one SH pulse output means. Cost can be further reduced.

  According to the present invention, the first output period in which the first SH pulse is output to the first line sensor and the second output period in which the second SH pulse is output to the second line sensor are alternately switched, and according to the switching timing. Thus, the transfer pulse output from one transfer pulse output means can be alternately switched and input to the first and second shift registers. As a result, both sides of the document can be read using two line sensors, and there is no need to separately provide transfer pulse output means for outputting transfer pulses to the first and second shift registers. Can be reduced.

  FIG. 1 is a schematic diagram illustrating an example of an internal configuration of a document reading apparatus 1 according to an embodiment of the present invention. In this document reading device 1, a plurality of documents can be set on the document tray 2, and the documents on the document tray 2 are sequentially conveyed one by one by the document conveying mechanism 3, and Image data on both sides of each document can be generated by reading the images on the front and back sides of the document in parallel with the two CCD units 4A and 4B. Documents that can be read by the document reading apparatus 1 are not limited to paper, and include other thin sheet documents.

  The document transport mechanism 3 is a document transport unit including a pickup roller 5, a paper feed roller 6, a separation roller 7, a plurality of transport rollers 8 and a discharge roller 9. The documents on the document tray 2 are sequentially sent out one by one to the transport path 10 by the rotating pickup roller 5. At this time, due to static electricity or the like generated between the overlapping originals, so-called double feeding may occur when two or more originals are sent out to the conveyance path 10 in a state of being overlapped. When such double feeding occurs, the second and subsequent originals are separated by the separation roller 7 and sent back to the original tray 2 so that only the first original is conveyed to the conveyance path 10. It is like that.

  Here, the paper feed roller 6 and the separation roller 7 are arranged so as to face each other with the conveyance path 10 interposed therebetween. Similar to the pickup roller 5, the paper feed roller 6 rotates in a direction to transport the paper in the transport path 10 to the downstream side. On the other hand, the separation roller 7 rotates in a direction in which the paper in the transport path 10 is sent back to the upstream side. As a result, even when two or more originals are overlapped by the pickup roller 5 and sent to the conveyance path 10, the first original is conveyed downstream by the paper feed roller 6, and the second and subsequent originals are conveyed. The document can be sent back to the document tray 2 by the separation roller 7.

  The document sent out from the paper feed roller 6 to the downstream side of the conveyance path 10 is further conveyed to the downstream side by a plurality of conveyance rollers 8 provided in the conveyance path 10, and is discharged to the outside through the discharge roller 9. . A document conveyed in the conveyance path 10 is scanned on the front and back images by two CCD units 4A and 4B provided in the middle of the conveyance path 10, and image data on both sides of the document is generated.

  The two CCD units 4A and 4B are original reading means for optically reading the image of the original, respectively. The front CCD unit 4A for reading the front side of the original and the back CCD unit 4B for reading the back side of the original. It consists of. These CCD units 4A and 4B are arranged so as to face each other across the conveyance path 10, and irradiate light in opposite directions toward a common reading position in the conveyance path 10, and pass through the reading position. By receiving the reflected light from the original, an electrical signal corresponding to the amount of received light is output.

  More specifically, the front CCD unit 4A accumulates and photoelectrically converts a light source that emits light toward the surface of the document in the transport path 10 and reflected light from the surface of the document for each line. A surface CCD line sensor and the like are provided. On the other hand, the back surface CCD unit 4B has a light source that irradiates light toward the back surface of the document in the conveyance path 10, and a back surface CCD line that accumulates reflected light from the back surface of the document for each line and performs photoelectric conversion. Sensors are provided.

  Each CCD line sensor provided in the front surface CCD unit 4A and the rear surface CCD unit 4B is configured by arranging a plurality of CCDs as light receiving elements in a line shape. When scanning a document on both sides, main scanning is realized by outputting signals corresponding to the amount of received light from a plurality of CCD line sensors of the CCD unit 4A for the front surface and the CCD unit 4B for the back surface. Line data for one line per line is generated. On the other hand, the sub-scan is realized by conveying the document in a direction orthogonal to the direction in which the plurality of CCDs of each CCD line sensor are arranged.

  In the middle of the conveyance path 10, a plurality of document detection sensors 11, 12, and 13 are provided for detecting a document passing through the conveyance path 10. In this example, the first document detection sensor 11 is provided on the downstream side of the paper feed roller 6, and the second document detection sensor 12 is provided on the downstream side of the first document detection sensor 11 and on the upstream side of the reading positions of the CCD units 4A and 4B. And a third document detection sensor 13 is provided downstream of the reading position of the CCD units 4A and 4B. These document detection sensors 11, 12, and 13 are made of optical sensors, for example, and detect the document by irradiating light toward the conveyance path 10 and receiving reflected light from the document passing through the conveyance path 10. be able to.

  The first document detection sensor 11 detects a document sent into the conveyance path 10 through the paper feed roller 6. Based on the output signal from the first document detection sensor 11, the presence or absence of the document can be determined. The second document detection sensor 12 detects the leading edge and the trailing edge of the document conveyed in the conveyance path 10. Based on the output signal from the second document detection sensor 12, the leading edge position and the trailing edge position of the document are specified, and the reading start and the reading end control are performed at timings corresponding to these positions. Can be accurately read from the rear end to the rear end, and the reading range of the original can be prevented from being shifted. The third document detection sensor 13 detects a document that has passed the reading positions of the CCD units 4A and 4B. Based on the output signal from the third document detection sensor 13, it is possible to determine the timing for sending the subsequent document to the transport path 10.

  FIG. 2 is a block diagram showing an electrical configuration of the document reading apparatus 1. The front surface CCD unit 4A is provided with a front surface shift register 42A to which line data generated by photoelectric conversion of the front surface CCD line sensor 41A is input in addition to the front surface CCD line sensor 41A. On the other hand, the back surface CCD unit 4B includes a back surface shift register 42B to which line data generated by photoelectric conversion of the back surface CCD line sensor 41B is input in addition to the back surface CCD line sensor 41B. Yes.

  In the present embodiment, the front CCD unit 4A and the back CCD unit 4B are driven by a common CCD drive circuit 40, respectively. The CCD drive circuit 40 includes an SH pulse output unit 43 and a transfer pulse output unit 44. The SH pulse output unit 43 is an SH pulse output unit that outputs an SH pulse at the same reading cycle to the front surface CCD line sensor 41A and the rear surface CCD line sensor 41B. The front CCD line sensor 41A inputs line data to the front shift register 42A based on the SH pulse input from the SH pulse output unit 43. On the other hand, the back surface CCD line sensor 41B inputs line data to the back surface shift register 42B based on the SH pulse input from the SH pulse output unit 43.

  The cycle in which the SH pulse is output from the SH pulse output unit 43 defines the light accumulation time for one line in the front surface CCD line sensor 41A and the rear surface CCD line sensor 41B. That is, when an SH pulse is output from the SH pulse output unit 43 to the surface CCD line sensor 41A, line data is input from the surface CCD line sensor 41A to the surface shift register 42A, and the surface CCD line sensor 41A After the accumulated charge is reset, the reflected light from the next line on the surface of the original is accumulated in the front CCD line sensor 41A until the next SH pulse is input in the reading cycle.

  Similarly, when an SH pulse is output from the SH pulse output unit 43 to the back surface CCD line sensor 41B, line data is input from the back surface CCD line sensor 41B to the back surface shift register 42B, and the back surface CCD line sensor 41B. After the accumulated charge is reset, the reflected light from the next line on the back side of the document is stored in the back surface CCD line sensor 41B until the next SH pulse is input in the reading cycle. .

  The transfer pulse output unit 44 is transfer pulse output means for outputting transfer pulses to the front surface shift register 42A and the back surface shift register 42B. The front-side shift register 42 </ b> A transfers line data on the front side of the document input from the front-surface CCD line sensor 41 </ b> A to the synthesis circuit 45 based on the transfer pulse from the transfer pulse output unit 44. On the other hand, the back-side shift register 42B transfers the back-side line data of the document input from the back-side CCD line sensor 41B to the combining circuit 45 based on the transfer pulse from the transfer pulse output unit 44.

  The transfer pulse output unit 44 alternately outputs transfer pulses at a predetermined cycle to the front-side shift register 42A and the back-side shift register 42B. As a result, the line data is alternately transferred from the front-side shift register 42A and the back-side shift register 42B to the combining circuit 45. In the combining circuit 45, each line data on the front and back sides of the document is one continuous line for each line. Synthesized into data. The line data is converted into a digital value by the A / D conversion circuit 49, whereby image data on both sides of the document is generated.

  The image data of the front and back sides of the original synthesized by the synthesis circuit 45 and digitized by the A / D conversion circuit 49 is subjected to image processing after the resolution in the sub-scanning direction is converted by the resolution conversion circuit 46 as necessary. Predetermined image processing is performed in the circuit 47 and stored in a memory (not shown). The image processing performed by the image processing circuit 47 may include various image processing such as binarization processing in addition to resolution conversion in the main scanning direction, shading correction, and compression processing.

  The reading resolution setting unit 48 is a reading resolution setting unit that sets the reading resolution of the front and back sides of the document, and can set the reading resolution separately for the front and back sides of the document. The document reading resolution may be set by the user directly inputting a numerical value, or when the user sets another numerical value such as a variable magnification, the reading resolution corresponding to the numerical value is set. May be configured.

  In the present embodiment, the document conveyance speed of the document conveyance mechanism 3 is changed according to the document reading resolution set by the reading resolution setting unit 48 based on a user operation. In other words, the higher the document reading resolution is set, the slower the document transport speed increases the number of pixels per unit area when reading the document. The lower the document reading resolution is set, the more the document is transported. By increasing the speed, the number of pixels per unit area when reading a document is reduced. More specifically, the document is transported at a transport speed corresponding to the scanning resolution set higher than the scanning resolution of the front and back surfaces of the document set by the scanning resolution setting unit 48. .

  The resolution conversion circuit 46 converts the resolution (output resolution) of the image data to be output to the image processing circuit 47 in the sub-scanning direction based on the reading resolution of the front and back sides of the document set by the reading resolution setting unit 48. It is a conversion means. As described above, even when the reading resolution setting unit 48 sets different reading resolutions for the front surface and the back surface of the document, the document is transported at a transport speed corresponding to a higher reading resolution. Therefore, the resolution of the image data on the front and back sides of the digitized document output from the A / D conversion circuit 49 is the same.

  Therefore, in the present embodiment, the resolution in the sub-scanning direction of the image data of the reading surface set to a lower reading resolution among the image data of the front surface and the back surface of the original document output from the synthesis circuit 45 and digitized. The resolution conversion circuit 46 performs the process of reducing the image quality, so that the resolution in the sub-scanning direction of the image data output to the image processing circuit 47 is different between the front surface and the back surface of the document. If the process of reducing the resolution in the sub-scanning direction of the image data on the front or back side of the document performed by the resolution conversion circuit 46 is a process that reduces the number of lines of the image data, for example, some lines are thinned out. It may be processing.

  FIG. 3 is a waveform diagram of the SH pulse and the transfer pulse that are output when both sides of the original are read by the original reading apparatus 1 of FIG. As shown in FIGS. 3A and 3B, the SH pulse output unit 43 alternately outputs SH pulses at the same reading cycle TR to the front surface CCD line sensor 41A and the rear surface CCD line sensor 41B. is doing.

  The pulse width of the SH pulse (hereinafter referred to as “surface SH pulse”) output from the SH pulse output unit 43 to the front surface CCD line sensor 41A is in the first output period T1, which is a half period of the reading cycle TR. It corresponds. On the other hand, the pulse width of the SH pulse output from the SH pulse output unit 43 to the back surface CCD line sensor 41B (hereinafter referred to as “back surface SH pulse”) is a second output period consisting of a half period of the reading cycle TR. It corresponds to T2. That is, the SH pulse output unit 43 alternately switches the first output period T1 and the second output period T2 each having a half period of the reading period TR, and generates the surface SH pulse having the first output period T1 as a pulse width. While outputting to the front surface CCD line sensor 41A, a back surface SH pulse having a pulse width of the second output period T2 is output to the back surface CCD line sensor 41B.

  The transfer pulse output unit 44 outputs a transfer pulse at a constant cycle shorter than the first output period T1 and the second output period T2, and outputs the transfer pulse to the front-side shift register 42A and the back-surface for every predetermined time. The shift register 42B is alternately switched. More specifically, the first output period T1 in which the front surface SH pulse is output to the front surface CCD line sensor 41A is a back surface transfer period in which the transfer pulse is output to the rear surface shift register 42B, and the back surface CCD line is output. The second output period T2 in which the back surface SH pulse is output to the sensor 41B is a front surface transfer period in which the transfer pulse is output to the front surface shift register 42A.

  That is, the surface SH pulse is output to the surface CCD line sensor 41A, and the line data is input from the surface CCD line sensor 41A to the surface shift register 42A. The transfer pulse is not input. Further, during the second output period T2 in which a back surface SH pulse is output to the back surface CCD line sensor 41B and line data is input from the back surface CCD line sensor 41B to the back surface shift register 42B, the back surface shift register 42B The transfer pulse is not input.

  FIG. 4 is a flowchart showing an example of processing performed by the resolution conversion circuit 46. The resolution conversion circuit 46, when the reading resolution of the front surface and the back surface of the document set by the reading resolution setting unit 48 is the same (Yes in step S101), is output from the synthesis circuit 45 and digitized. The image data on the back side is input to the image processing circuit 47 without converting the resolution.

  On the other hand, when the reading resolutions of the front and back sides of the document set by the reading resolution setting unit 48 are different (No in step S101), and the reading resolution of the front side is set lower than the back side. (Yes in step S102), the resolution conversion circuit 46 performs a process of reducing the resolution of the image data on the front surface among the respective image data on the front surface and the back surface of the document output from the synthesis circuit 45 and digitized (step S103). ).

  On the other hand, when the reading resolutions of the front and back sides of the document set by the reading resolution setting unit 48 are different (No in step S101), the reading resolution of the back side is set lower than the front side. (No in step S102), the resolution conversion circuit 46 performs a process of reducing the resolution of the image data on the back side of the image data on the front side and the back side of the document output from the synthesis circuit 45 and digitized (step S102). Step S104).

  In the present embodiment, the first output period T1 for outputting the front surface SH pulse to the front surface CCD line sensor 41A and the second output period T2 for outputting the rear surface SH pulse to the rear surface CCD line sensor 41B are alternately switched. Depending on the switching timing, the transfer pulse output from one transfer pulse output unit 44 can be alternately input to the front shift register 42A and the rear shift register 42B. In this way, the two CCD line sensors 41A and 41B are used by transferring the line data on the front and back sides of the document input to the front and back shift registers 42A and 42B based on the transfer pulse. Can scan both sides of the document. In addition, since it is not necessary to separately provide a transfer pulse output unit that outputs a transfer pulse to the front surface shift register 42A and the back surface shift register 42B, the manufacturing cost can be further reduced.

  Further, in this embodiment, even when different reading resolutions are set for the front surface and the back surface of the document, the cycle of outputting SH pulses to the front surface CCD line sensor 41A and the back surface CCD line sensor 41B is changed. In the resolution conversion circuit 46, the reading resolution of the image data of the front and back sides of the original transferred from the front-side shift register 42A and the back-side shift register 42B is set lower. The resolution in the sub-scanning direction of the surface image data can be reduced. Accordingly, unlike the configuration in which the cycle of outputting the SH pulse to the front surface CCD line sensor 41A and the rear surface CCD line sensor 41B is changed, the SH pulse is output at a constant cycle by using one SH pulse output unit 43. Therefore, the manufacturing cost can be further reduced.

  In the above embodiment, as an example of the document reading apparatus 1, a configuration has been described in which both sides of a document are read by the front surface CCD unit 4A and the back surface CCD unit 4B, and the generated image data on both sides of the document is stored in a memory. However, the document reading apparatus 1 may be incorporated in an image forming apparatus such as a copying machine so that images based on the image data on both sides of the generated document are printed on paper.

1 is a schematic diagram illustrating an example of an internal configuration of a document reading apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating an electrical configuration of the document reading apparatus. FIG. FIG. 3 is a waveform diagram of an SH pulse and a transfer pulse that are output when both sides of an original are read by the original reading apparatus of FIG. 2. It is the flowchart which showed an example of the process performed by the resolution conversion circuit. It is a block diagram showing an example of a conventional document reading apparatus. FIG. 6 is a waveform diagram of an SH pulse and a transfer pulse that are output when both sides of an original are read by the original reading apparatus of FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Document reader 3 Document conveyance mechanism 4A Front surface CCD unit 4B Rear surface CCD unit 40 CCD drive circuit 41A Front surface CCD line sensor 41B Rear surface CCD line sensor 42A Front surface shift register 42B Back surface shift register 43 SH pulse output unit 44 Transfer pulse output unit 45 Synthesis circuit 46 Resolution conversion circuit 47 Image processing circuit 48 Reading resolution setting unit 49 A / D conversion circuit

Claims (2)

The front and back surfaces of the document are irradiated with light, the reflected light from the front surface is accumulated for each line by the first line sensor, photoelectrically converted, and line data generated by the photoelectric conversion is input to the first shift register. In addition, the reflected light from the back surface is accumulated for each line by the second line sensor, photoelectrically converted, line data generated by the photoelectric conversion is input to the second shift register, and the line data is converted into a digital value. A document reading device that generates image data on both sides of a document by converting to
SH pulse output means for outputting SH pulses at the same reading period to the first and second line sensors,
Transfer pulse output means for outputting a transfer pulse for transferring the line data input to the first and second shift registers,
The SH pulse output means alternately switches between a first output period and a second output period, each of which is a half of the reading period, and outputs a first SH pulse having the first output period as a pulse width to the first line. And outputs a second SH pulse having a pulse width in the second output period to the second line sensor.
The transfer pulse output means outputs a transfer pulse to the second shift register during the first output period and outputs a transfer pulse to the first shift register during the second output period. Document reader. Reading resolution setting means for setting the reading resolution of the front and back sides of the document;
Of the image data on the front and back sides of the original document transferred from the first and second shift registers and digitized when different reading resolutions are set on the front and back sides of the document by the reading resolution setting means, 2. The document reading apparatus according to claim 1, further comprising resolution conversion means for reducing the resolution in the sub-scanning direction of the image data on the reading surface set at a lower reading resolution.

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