JP2009124481A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus which simultaneously reads both sides of an original, the image reading apparatus automatically performing registration adjustment, at a read starting position on a front/rear side of the original. <P>SOLUTION: Image reading is started, immediately prior to the original passes, and a shadow part caused by thickness of the original is detected from the images read. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that simultaneously reads both sides of a document fed from an automatic document feeder, and more particularly to registration adjustment of a reading start position on the front surface / back surface of a document.

An image reading device that scans a document fed from an automatic document feeder is configured to detect a document reading start position in a sub-scanning direction orthogonal to an image sensor arranged in a row for reading a document. Fixed position detecting means is provided.
The operation will be described with reference to FIGS. 5 and 6. When reading of the document 1 is started, the document 1 set on the automatic document feeder 10 is transported by the transport roller 2 in the first CIS 6 direction.

  On the way, a detection signal is output from the original fixed position detecting means 3 at a timing when the original 1 passes through the original front end fixed position detecting means 3.

  The first CIS 6 starts reading the document 1 after the document 1 having a distance 1200 between the document leading edge position detecting means 3 and the first CIS 6 determined based on the information is transported.

  However, the distance 1200 determined in advance by the accumulation of the document reading start position component assembly position varies from apparatus to apparatus.

  Therefore, the registration adjustment in the sub-scanning direction is performed so that the original 1 is read at a predetermined set position after the assembly.

  As a document position correcting device that automatically corrects the reading position of a document, for example, as proposed in JP-A-5-328052, a black document or a document on which a reference line is printed for registration adjustment is used. In some cases, the distance between the document leading edge position detecting means and the image sensor is corrected from the document leading edge fixed position detection signal and the actually read registration adjustment document.

FIG. 12 is a schematic diagram of a document feeding system viewed from the side of an image reading apparatus according to a conventional example.
JP-A-5-328052

  Conventionally, it has been necessary to prepare and set a document for registration adjustment in order to automatically correct the document reading position of the automatic document feeder, and there has been a problem that the operation is complicated.

  In addition, in the image reading apparatus for simultaneous double-sided reading described in this proposal, the front and back two CISs are arranged at different positions in the paper feed direction of the document, so that each CIS position is also corrected. There is a need. SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that automatically performs registration adjustment of the reading start position of the front surface / back surface of a document in an image reading device that simultaneously reads both sides of a document fed from an automatic document feeder. Is to provide.

  In order to achieve the above object, in an image reading apparatus that reads a document conveyed from an automatic document feeder to an exposure unit, first and second image sensors CIS that respectively read the front and back surfaces of the document, and sub-scanning of the document A document leading end position detecting unit for detecting a fixed position in the direction, a document leading end detecting unit for detecting the leading end position of the document from the image data of each document read by the first and second CISs, and a document feed amount. A document feed amount measuring means for measuring, and using the position information of the document detected by the document tip fixed position detecting means as a reference, the document leading edge position information read by the first CIS and the second image are read. Image position correction information is generated from the leading edge position information of the original document and the document feed amount information between the first and second CIS, and the surface image of the document read by the first CIS and the document read by the second CIS Each image destination of the back side image of An image reading apparatus comprising correcting an end position.

  As described above, according to the present invention, in an image reading apparatus that simultaneously reads both sides of an original, image reading is started immediately before the original passes, and a shadow portion based on the thickness of the original is detected from the read image. It is possible to automatically perform registration adjustment of the reading start position of the front surface / back surface.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  FIG. 1 is a schematic diagram of a document feeding system viewed from the side of an image reading apparatus that best represents the features of the present invention, and FIG. 2 is a system block diagram of the image reading apparatus of this embodiment. FIG. 4 is a schematic diagram of a document feeding system showing an initial position of a document to be read in the image reading apparatus of the present embodiment, and FIG. 4 shows that the document to be read in the image reading apparatus of the present embodiment has reached a fixed position at the front end of the document. FIG. 5 is a schematic diagram of the document feeding system showing the position, and FIG. 5 is a schematic diagram of the document feeding system showing the position where the document to be read has reached the reading position of the first CIS in the image reading apparatus of the present embodiment. FIG. 6 is a schematic diagram of the document feeding system showing the position where the document to be read in the image reading apparatus of this embodiment has reached the reading position of the second CIS, and FIG. 7 is the image of this embodiment. To the reader FIG. 8 is a schematic diagram of the document feeding system showing in detail the image reading start position when the document to be read reaches the first CIS reading position, and FIG. 8 is a document to be read in the image reading apparatus of this embodiment. FIG. 9 is a schematic diagram of a document feeding system showing in detail an image reading start position before image reading is started after the first CIS has reached the first CIS reading position, and FIG. 9 shows this embodiment. FIG. 2 is a schematic diagram of a document feeding system showing in detail an image reading start position after an actual document image reading is started after the document to be read in the image reading apparatus reaches the first CIS reading position; 10 is a flowchart showing an image reading sequence in the image reading apparatus of this embodiment, and FIG. 11 is a scan image read from the first CIS 6 in the image reading apparatus of this embodiment.

  In FIG. 1, 1 is a document on which characters or images are printed on both front and back sides, 2 is a transport roller driven by a stepper motor (not shown) to transport the document 1, and 3 is for detecting a fixed position of the front end of the document. A photosensor composed of a photodiode and a phototransistor, 4 is a pickup sensor that turns on the output of the photosensor 3 when the document 1 passes the document detection fixed position, and 6 is for reading an image on the surface of the document 1. In addition, an image sensor that performs photoelectric conversion arranged in a line perpendicular to the paper feeding direction of the original 1, an LED for irradiating the original 1, and the light emitted from the LED are guided in the direction in which the image sensor is arranged. The first CIS (Contact Image Sensor) 7 composed of a light guide and a lens for condensing the reflected light applied to the LED on the image sensor is emitted from the light guide of the first CIS 6. The first white reference plate for correcting the uniformity of the reflected light of the LED light in the image sensor direction, 8 the second CIS for reading the image of the back side of the document 1, and 9 the second CIS 8 A second white reference plate for correcting the uniformity of reflected light, 10 is a housing of the image reading apparatus, and 11 is a document setting unit for setting a document 1.

  In FIG. 2, 6a is a first LED constituting the first CIS 6, 6b is a first image sensor constituting the first CIS 6, 8a is a second LED constituting the second CIS 8, and 8b is a second LED. The second image sensor constituting the second CIS 8, 20 is an LED driving unit comprising an operational amplifier and a transistor for driving the first LED 6 a and the second LED 8 a, and 21 is the first image sensor 6 b and the second image sensor 6. The analog signal processing unit 22 includes transistors for performing output level adjustment and filter processing of the image signal of the original document converted into the analog electric signal output from the second image sensor 8 b. An A / D unit 23 for converting an analog signal obtained by scanning the output document into a digital signal, and a step mode for rotating the transport roller 2 by a control signal from the control unit 26. A step motor driving unit composed of a transistor for driving the data 24, 24 is a step motor that rotates in response to a step signal from the step motor driving unit 23 and drives the conveying roller, and 25 is an A / D unit 22. A memory unit 26 configured by a DRAM or the like for storing a digital image signal of an original input from the CPU, controls the image reading apparatus of the present embodiment, and communicates with a host PC (not shown) via the USB interface 27 for scanning. 27 is a USB interface unit for communicating with the host PC built in the control unit 26.

  In FIG. 5, reference numeral 50 denotes a preset distance between the pickup sensor 4 for detecting the document front end fixed position and the first CIS 6 for reading the surface of the document 1.

  In FIG. 6, reference numeral 60 denotes a preset distance between the first CIS 6 that reads the front surface of the document 1 and the second CIS 8 that reads the back surface of the document.

  In FIG. 7, 6c is a first CIS substrate on which the first image sensor 6b, the first LED 6a, and the like are mounted, and 6d is a first light that condenses the reflected light of the first LED 6a on the first image sensor 6b. The lens 6e is a first light guide for guiding the light emitted from the first LED 6a in the direction in which the first image sensor 6b is disposed, and 70 is when the document 1 reaches the reading position of the first CIS 6 The path from which the light emitted from the first light guide 6e is reflected by the first white reference plate 7 and enters the first lens 6d is shown.

  In FIG. 8, reference numeral 80 denotes image reading after the document 1 reaches the reading position of the first CIS 6, and light emitted from the first light guide 6 e is applied to the document 1 before the actual document is read. This shows a state where the light is blocked and the reflected light does not enter the first lens 6d.

  In FIG. 9, reference numeral 90 denotes an actual image 1 read after the document 1 reaches the reading position of the first CIS 6, and then the light emitted from the first light guide 6 e is reflected on the document 1. A path for entering the first lens 6d is shown.

  In FIG. 11, reference numeral 1100 denotes a scanned image portion of the first white reference plate 6 of an image scanned from the first CIS 6, and 1101 denotes a shadow portion generated by the thickness of the original 1 of the image scanned from the first CIS 6. A scanned image portion 1102 is a scanned image portion of the document 1 of an image scanned from the first CIS 6.

  In the above configuration, the operation when reading both sides of a document according to this embodiment will be described with reference to the flowchart of FIG.

  First, a scan start command is issued from the host PC (not shown) to the control unit 26 via the USB interface 27.

(Step S1001 in FIG. 10)
The control unit 26 rotates the step motor 24 via the stepper motor driving unit 23, and the step motor 24 rotates the transport roller 2 to feed the document 1 in the first CIS 6 direction.

(Step S1002 in FIG. 10)
At this time, when the document 1 conveyed to the conveyance roller 2 reaches the position of the pickup sensor 4, a detection signal is output from the photo sensor 3 to the control unit 26.

(Step S1003 in FIG. 10)
When it is input to the control unit 26 by a detection signal from the photosensor 3 that the document 1 has reached the original document tip fixed position, the control unit 26 corresponds to a preset distance 50 between the pickup sensor 4 and the first CIS 6. The step motor 24 is driven by the number of motor steps to be carried, and the document 1 is conveyed to the reading start position of the first CIS 6.

(Step S1004 in FIG. 10)
When a motor step corresponding to a preset distance 50 is output, the first CIS 6 starts image scanning on the surface of the document 1, and the surface image of the document 1 output from the first CIS 6 is an A / D portion. The image is transferred from the control unit 26 to the memory unit 25 via the USB 22 and transferred to the host PC via the USB interface 27.

(Step S1005 in FIG. 10)
Subsequently, the control unit 26 drives the step motor 24 by a motor step corresponding to a preset distance 60 between the first CIS 6 and the second CIS 8 and conveys the document 1 to the reading start position of the second CIS 8.

(Step S1006 in FIG. 10)
When a motor step corresponding to a preset distance 60 is output, the second CIS 8 starts image scanning on the back side of the document 1, and the back image of the document 1 output from the second CIS 8 is an A / D portion. The image is transferred from the control unit 26 to the memory unit 25 via the USB 22 and transferred to the host PC via the USB interface 27.

(Step S1007 in FIG. 10)
The control unit 26 drives the step motor 24 to convey the document 1 until the image reading of the reading range of the document 1 instructed by the host PC is completed.

(Step S1008 in FIG. 10)
When the image reading of the reading range of the document 1 instructed by the host PC is completed, the control unit 26 stops the image reading of the first CIS 6 and the second CIS 8 and drives the step motor 24 to discharge the document 1. The end of image reading is notified to the host PC via the USB interface 27.

(Step S1009 in FIG. 10)
In the host PC, the surface image of the document scanned from the first CIS 6 is an image portion 1100 of the first white reference plate 6 scanned as white density in order from the document transport direction, as shown in FIG. It is composed of a shadow portion 1101 generated by the thickness of the original 1 scanned as the density and an actual surface image portion 1102 of the original 1.

  The host PC inspects the density of the image line by line from the leading edge of the scanned image to detect a line serving as a boundary between the dark density shadow portion 1101 generated by the thickness of the document and the actual document scan portion.

(Step S1010 in FIG. 10)
The host PC can obtain only an image obtained by scanning the actual surface of the original by discarding the image from the first line of the surface image of the scanned original to the detected line.

(Step S1011 in FIG. 10)
The back side image of the document 1 scanned from the second CIS 8 is also composed of the image portion of the white reference plate, the shadow portion generated by the thickness of the document, and the actual back side document portion in the same manner as the front side scanned from the first CIS 6. The boundary line between the shadow portion and the actual back side document portion is detected in the host PC.

(Step S1012 in FIG. 10)
The host PC can obtain only the scanned image of the back side of the original document by discarding the image from the first line of the back side image of the scanned document to the detected line.

(Step S1013 in FIG. 10)
Thus, a series of document scanning operations is completed.

(Step S1014 in FIG. 10)
From the next scan, based on the position of the position detection sensor, the first CIS starts reading images from the position where the first paper feed correction amount and the second CIS add the second paper feed correction amount. .

1 is a schematic diagram of a document feeding system viewed from the side of an image reading apparatus according to a first embodiment of the present invention. 1 is a system block diagram of an image reading apparatus according to a first embodiment of the present invention. 1 is a schematic diagram of a document feeding system showing an initial position of a document to be read according to a first embodiment of the present invention. FIG. 1 is a schematic diagram of a document feeding system showing a position where a document to be read according to a first embodiment of the present invention has reached a document leading end fixed position. FIG. 1 is a schematic diagram of a document feeding system showing a position where a document to be read according to a first embodiment of the present invention reaches a first CIS reading position; FIG. FIG. 3 is a schematic diagram of a document feeding system showing a position where a document to be read according to the first embodiment of the present invention reaches a reading position of a second CIS. 1 is a schematic diagram of a document feeding system showing in detail an image reading start position when a document to be read according to a first embodiment of the present invention reaches a first CIS reading position; FIG. An original document feeding system which starts image reading after a document to be read according to the first embodiment of the present invention reaches the first CIS reading position and shows an image reading start position before reading an actual document in detail. FIG. FIG. 2 is a schematic diagram of a document feeding system showing in detail an image reading start position after an actual document image reading is started after a document to be read reaches a first CIS reading position according to the first embodiment of the present invention. Figure. FIG. 3 is a flowchart showing an image reading sequence according to the first embodiment of the present invention. The scanned image read from the 1st CIS6 concerning the 1st example of the present invention. FIG. 10 is a schematic diagram of a document feeding system viewed from the side of an image reading apparatus according to a conventional example.

Explanation of symbols

1 Document 2 Transport roller 3 Photo sensor 4 Pickup sensor 6 First CIS (Contact Image Sensor)
7 First white reference plate 8 Second CIS
9 Second white reference plate 10 Case 11 Document setting unit 6a First LED
6b First image sensor 8a Second LED
8b Second image sensor 20 LED driving unit 21 Analog signal processing unit 22 A / D unit 23 Step motor driving unit 24 Step motor 25 Memory unit 26 Control unit 27 USB interface unit 50 Pickup sensor for detecting the document front end fixed position 4 and a first CIS 6 that reads the front surface of the original document 1 60 A predetermined distance between the first CIS 6 that reads the front surface of the original document 1 and a second CIS 8 that reads the back side of the original document 6c First CIS substrate 6d First lens 6e First light guide 70 Light emitted from the first light guide 6e when the document 1 reaches the reading position of the first CIS 6 is applied to the first white reference plate 7. A path 80 that reflects and enters the first lens 6d 80 The state before the original 1 reaches the reading position of the first CIS 6 and image reading starts and the actual original is not read In this state, the light emitted from the first light guide 6e is blocked by the original 1 and the reflected light does not enter the first lens 6d. 90 After the original 1 reaches the reading position of the first CIS 6, A path through which light emitted from the first light guide 6e is reflected by the document 1 and enters the first lens 6d after the image reading of the document 1 is started. 1100 Scan image portion of the first white reference plate 6 1101 Scanned image portion of shadow portion generated by thickness of document 1 1102 Scanned image portion of document 1

Claims (2)

In an image reading apparatus that reads a document conveyed from an automatic document feeder to an exposure unit,
First and second image sensors CIS for reading the front and back sides of the document,
A document leading edge fixed position detecting means for detecting a fixed position in the sub-scanning direction of the document;
A document leading edge detecting means for detecting the leading edge position of the document from the image data of each document read by the first and second CIS;
A document feed amount measuring means for measuring a document feed amount;
Based on the document position information detected by the document tip fixed position detection means, the document tip position information read by the first CIS, the document tip position information read by the second image, the first and first Image position correction information is generated from the document feed amount information between the two CISs, and the leading edge position of each of the front image of the document read by the first CIS and the back image of the document read by the second CIS is corrected. An image reading apparatus. The image reading apparatus according to claim 1, further comprising means for recording image position correction information,
In subsequent image reading, the first and second CIS document reading start positions are corrected by the document feed amount calculated from the image position correction information with reference to the document position information detected by the document leading edge detection means. An image reading apparatus.

Images