JP2004328154A - Original reading apparatus and original reading method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an original reading apparatus and an original reading method capable of accurately detecting a size of an original even in the case of an original of an indefinite form without the adverse effect of a shadow of the original. <P>SOLUTION: When a first scanning unit 15 exists in the vicinity of a tip of an original, a first light source 41 is turned off and a second light source 42 is turned on. Then a short shadow is caused at the tip of the original, the short shadow at the tip of the original is read resulting in that the tip of the original is detected. Further, when the first scanning unit 15 exists in the vicinity of a tail end of the original, the first light source 41 is turned on and the second light source 42 is turned off. Then a short shadow is caused at the tail end of the original, the short shadow at the tail end of the original is read resulting in that the tail end of the original is detected. Since the tip and the tail end of the original M are detected in this way, the size of the original can accurately be discriminated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a document reading apparatus and a document reading method for reading a document while irradiating the document with light, which is used in a copying machine, a facsimile machine, or the like.
[0002]
[Prior art]
As this type of apparatus, there are a document moving method in which a document is scanned and read while transporting the document, and a document fixing method in which the document is scanned and read after the document is placed and positioned.
[0003]
In either method, the size of the document is detected in order to accurately read the document. In the former document movement method, a sensor is provided in the document conveyance path, the conveyed document is detected by the sensor, the detection timing by the sensor, the conveyance speed of the document, the distance from the sensor position to the document reading position, etc. , The leading and trailing edges of the original in the read image are detected, and the shadows of the leading and trailing edges of the original are erased by image processing, and then the size of the original is accurately identified.
[0004]
In the latter document fixing method, the document is read by pre-scanning, the size of the document is identified based on the read image, and then the document is read by main scanning.
[0005]
However, in the original fixing method, the size of the original is directly determined from the image including the shadow without erasing the shadows at the leading and trailing ends of the original by image processing as in the original moving method. As a result, the size of the document could not be accurately determined. For example, as shown in FIG. 7A, a document is placed on a platen glass 101, and while the document 103 is illuminated from a diagonally lower left by a light source 102 below the platen glass 101, the light source 102 is moved. Is read, an image is read in which no shadow is produced at the leading edge of the document and a long shadow R is produced at the trailing edge of the document. Similarly, as shown in FIG. 7B, when the light source 102 is moved and the document 103 is read while illuminating the document 103 from diagonally below right, a long shadow R occurs at the leading end of the document and An image in which no shadow is produced at the end will be read. For this reason, the leading and trailing edges of the document cannot be accurately specified, and the size of the document cannot be determined accurately.
[0006]
On the other hand, in Japanese Patent Application Laid-Open No. H10-157, an adjustment sheet with a white background is read, the shadow of the edge of the adjustment sheet is stored in a non-volatile memory, and the shadow of the end of the adjustment sheet in the non-volatile memory is used to copy the original. A technique of masking an edge shadow has been disclosed.
[0007]
Patent Document 2 discloses a technique in which a first document edge detection unit and a second document edge detection unit detect edges of a document, respectively, and select one having a large size among the edges. ing.
[0008]
[Patent Document 1]
JP 2001-189830 A [Patent Document 2]
JP-A-10-224563
[Problems to be solved by the invention]
However, in Japanese Patent Application Laid-Open No. H11-163, when a document having the same size as the adjustment paper is read, the shadow at the edge of the document can be masked. However, for a document having a size different from the adjustment paper, the shadow at the edge of the document is masked. I couldn't. For this reason, even if the technique of Patent Document 1 is applied, it is difficult to always accurately determine the size of the document.
[0010]
Further, in Patent Document 2, although the edge of the document can be detected without being affected by noise or dust, or by the characters or lines of the document, the shadow of the document is not considered.
[0011]
Therefore, the present invention has been made in view of the above-described conventional problems, and it is possible to accurately detect the size of a document without being affected by the shadow of the document and even for an irregular type document. An object of the present invention is to provide a possible original reading apparatus and an original reading method.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a document reading apparatus that reads a document while irradiating the document with light, a plurality of light sources that irradiate the document with light, simultaneous lighting of each light source, and switching of each light source. Control means for reading the original while sequentially turning on the light.
[0013]
According to the present invention having such a configuration, a document is read while simultaneously turning on each light source for illuminating the document and switching and lighting each light source sequentially. When the light sources are turned on at the same time, the surface of the document can be uniformly irradiated, and the surface of the document can be read well. Further, when each light source is switched and lit, light is emitted to the edge of the document from various appropriate angles, so that a short shadow occurs at both the leading edge and the trailing edge of the document. Therefore, the size of the document can be accurately determined by accurately detecting the leading edge and the trailing edge of the document. Further, there is no need to provide a sensor for detecting the leading and trailing edges and size of the document.
[0014]
In the present invention, the light sources are arranged side by side in the scanning direction of the document, and a light source near the scan start position and a light source near the scan end position are provided. The control unit simultaneously turns on the light source near the scan start position and the light source near the scan end position to read the document. Alternatively, the control unit selectively turns on the light source near the scan start position and the light source near the scan end position to detect the edge of the document.
[0015]
If the light source near the scan start position and the light source near the scan end position are provided and the respective light sources are turned on at the same time, the surface of the document can be uniformly illuminated and the surface of the document can be read well. . Also, if the light source near the scan start position and the light source near the scan end position are selectively turned on to illuminate the leading and trailing edges of the document obliquely, shadows of the leading and trailing edges of the document are generated. The leading and trailing edges of the document can be detected.
[0016]
Further, in the present invention, the control unit turns on one of the light source near the scan start position and the light source near the scan end position at the start of scanning of the document to detect the leading edge of the document at the scan start position and scan the document. The detection of both ends of the document separated in the direction perpendicular to the direction is performed. Then, the control means, when starting scanning of the original, detects both ends of the original separated from each other in a direction orthogonal to the scanning direction, and based on the width of the original document, which is the distance between both ends, the scanning end position side. The rear end position of the document is predicted, and during scanning of the document, the light source near the scan start position and the light source near the scan end position are simultaneously turned on at least in a range excluding the vicinity of the rear end of the document. Alternatively, the control means may detect both ends of the document separated in a direction perpendicular to the scanning direction at the start of scanning of the document, and based on the width of the document, which is the distance between the both ends, determine the scanning end position. The rear end position of the original is predicted, and during scanning of the original, either the light source near the scan start position or the light source near the scan end position is turned on near the rear end of the original.
[0017]
As described above, when the scanning of the original is started, if both ends of the original separated from each other in the direction orthogonal to the scanning direction are detected, based on the width of the original document, which is the separation distance between both ends, the original after the original at the scan end position is detected. The end position can be predicted. This is because, if the original is of a standard size (A5, B5, A4, B4, etc.), when the width of the original is specified, the length of the original is also specified. Then, during scanning of the document, if the light source near the scan start position and the light source near the scan end position are simultaneously turned on at least in a range excluding the vicinity of the rear end of the document, the surface of the document is uniformly irradiated, Can be satisfactorily read. Alternatively, if one of the light source near the scan start position and the light source near the scan end position is turned on near the rear end of the original during scanning of the original, the rear end of the original is illuminated from an oblique direction, and the original is illuminated. , And the trailing edge of the document can be detected.
[0018]
Further, in the present invention, the control unit reads the document while sequentially turning on each light source and switching on each light source during the pre-scan of each light source.
[0019]
In this way, at the time of pre-scanning of each light source, if the original is read, the leading and trailing edges of the original are accurately detected as described above, and the size of the original is accurately determined, At the time of the main scan, the original can be read accurately according to the size of the original.
[0020]
On the other hand, the present invention provides an original reading method for reading an original while irradiating the original with light. In the original reading method, a plurality of light sources for irradiating the original are simultaneously turned on and the respective light sources are switched on and on, and the original is read. I have.
[0021]
According to the method of the present invention, the same operation and effect as those of the original reading apparatus of the present invention can be achieved.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0023]
FIG. 1 is a side view showing an image forming apparatus to which an embodiment of a document reading apparatus according to the present invention is applied. The image forming apparatus 1 includes a document transport unit 2, a document reading device 3, a printing unit 4, a recording paper transport unit 5, a paper feed unit 6, and a paper discharge tray 7.
[0024]
When at least one document is set on the document set tray 11, the document transport unit 2 pulls out the document one by one from the document set tray 11 and conveys the document one by one. The conveyance of the document is temporarily stopped, and the leading end of the document is made parallel to the PS roller pair 12. Then, after synchronizing with the image recording operation by the printing unit 4, the clutch between the PS roller pair 12 and the drive shaft is turned on, the PS roller pair 12 is driven to rotate, and the original is conveyed again by the PS roller pair 12. Then, the document is passed between the platen glass 8a and the document pressing plate 9.
[0025]
In the original reading device 3, when the original is transported, the original is exposed by the first scanning unit 15, and the reflected light from the original is guided to the image forming lens 17 by the first and second scanning units 15 and 16, and the image forming lens The document image is formed on a photoelectric conversion element (hereinafter referred to as a CCD) 18 by 17. The CCD 18 repeatedly scans and reads the document in the main scanning direction, and outputs image data indicating the document.
[0026]
When the original is placed on the platen glass 8b, the first and second scanning units 15, 16 are moved while maintaining a predetermined speed relationship with each other, and the first scanning unit 15 moves the first and second scanning units 15, 16 on the platen glass 8b. The original is exposed, the reflected light from the original is guided to the imaging lens 17 by the first and second scanning units 15 and 16, and the original is imaged on the CCD 18 by the imaging lens 17.
[0027]
The image data output from the CCD 18 is subjected to various types of image processing by a control circuit such as a microcomputer (shown in FIG. 2), and then output to the printing unit 4.
[0028]
The printing unit 4 records an original indicated by image data on a recording sheet, and includes a photosensitive drum 21, a charger 22, a laser scan unit (hereinafter, referred to as LSU) 23, a developing unit 24, a transfer unit 25, A cleaning device 26, a static eliminator (not shown), a fixing device 27, and the like are provided. The photoreceptor drum 21 rotates in one direction, and after its surface is cleaned by the cleaning device 26 and the static eliminator, the surface is uniformly charged by the charger 22. The laser scan unit 23 modulates a laser beam according to the image data, and repeatedly scans the surface of the photosensitive drum 21 in the main scanning direction with the laser beam to form an electrostatic latent image on the surface of the photosensitive drum 21. The developing device 24 supplies the toner to the surface of the photosensitive drum 21 to develop the electrostatic latent image, and forms a visible image of the toner on the surface of the photosensitive drum 21. The transfer unit 25 transfers the visible image of the toner on the surface of the photoconductor drum 21 onto the recording paper transported by the recording paper transport unit 5. The fixing device 27 heats and presses the recording paper to fix a visible image of the toner on the recording paper. Thereafter, the recording paper is further transported by the recording paper transport unit 5 to the paper discharge tray 7 and discharged.
[0029]
The recording paper transport unit 5 includes a pair of PS rollers 28 for transporting the recording paper, a plurality of pairs of transport rollers 29, a transport path 31, a reverse transport path 32, and the like. The transport path 31 receives the recording paper from the paper feeding unit 6 and transports it to the printing unit 4, and further transports the recording paper to the paper discharge tray 7. The reverse transport path 32 receives the recording paper from the printing unit 4, reverses the recording paper, and transports the recording paper to the printing unit 4 again. A plurality of detection switches for detecting the passage of the recording paper are arranged in these conveyance paths 31 and 32, and control of the recording paper conveyance timing and the like is performed according to the detection of each detection switch.
[0030]
The paper supply unit 6 stores unused recording paper and supplies the unused recording paper to the recording paper transport unit 5, and includes a paper supply cassette 33 and a manual feed tray 34. The recording paper is stacked and stored in the paper feed cassette 33, and the recording paper is pulled out one by one by a half-moon-shaped pickup roller 35 and conveyed. The recording paper is also placed on the manual feed tray 34, the recording paper is pulled out by the pickup roller 36, and the recording paper is transported by the feed roller 37. When the recording paper is pulled out from the paper feed cassette 33 or the manual feed tray 34 and its leading end reaches the pair of PS rollers 28, the conveyance of the recording paper is temporarily stopped, and the leading end of the recording paper is made parallel to the pair of PS rollers 28. After that, the recording paper is conveyed to the transfer unit 25 of the printing unit 4 by the pair of PS rollers 28.
[0031]
In the document reading apparatus 3 of the present embodiment, the first scanning unit 15 is provided with two light sources, that is, first and second light sources 41 and 42, as shown in FIG. Is provided with a reflection mirror 15a.
[0032]
The first and second light sources 41 and 42 irradiate light to the document M on the platen glass 8b. A part of the reflected light from the document M passes between the first and second light sources 41 and 42, is reflected by the reflection mirror 15a, enters the second scanning unit 16, and further reflects each reflection of the second scanning unit 16. The light is reflected by the mirrors 16 a and 16 b and enters the CCD 18 via the imaging lens 17. The CCD 18 repeatedly scans the original M in the main scanning direction and reads the original M, and outputs image data indicating the original M to a control circuit 40 such as a microcomputer. Therefore, the reading position of the document M is illuminated from both sides of the first and second light sources 41 and 42. It can be said that the original M is being read at the center between the first and second light sources 41 and 42.
[0033]
The control circuit 40 controls the driving of the first and second light sources 41 and 42 through the first and second inverters 43 and 44. The first and second inverters 43 and 44 have a circuit configuration as shown in FIG. 3, for example, and apply an AC driving voltage to the first and second light sources 41 and 42, which are cold cathode fluorescent lamps. , 42 are turned on. The control circuit 40 controls on / off of a switch 46 between the first and second inverters 43 and 44 and the power supply 45 to turn on and off the first and second light sources 41 and 42.
[0034]
Here, when the document M is placed on the platen glass 8b as described above, the first and second scanning units 15 and 16 are moved while maintaining a predetermined speed relationship with each other, and the document M is moved. An image is formed on the CCD 18 and the original M is read by the CCD 18. This is called a main scan.
[0035]
Then, at the time of main scanning, the control circuit 40 turns on the switches 46 of the first and second inverters 43 and 44, and the first and second light sources 41 of the first scanning unit 15 as shown in FIG. , 42 are kept lit to uniformly illuminate the surface of the document M so that the surface of the document M can be read well.
[0036]
In addition, before the main scan, a pre-scan for determining the size and type (color image, monochrome image, text document, photo document, etc.) of the document M is performed. Also in this pre-scanning, the first and second scanning units 15 and 16 are moved while maintaining a predetermined speed relationship with each other, an image of the original M is formed on the CCD 18, and the original M is read by the CCD 18.
[0037]
Then, the control circuit 40 switches the switches 46 of the first and second inverters 43 and 44 on and off at appropriate timing during the pre-scan, and as shown in FIG. 4B, the first circuit of the first scanning unit 15 The simultaneous lighting of the first and second light sources 41 and 42 and the switching lighting of the first and second light sources 41 and 42 are periodically repeated. This is for detecting the leading end position and the trailing end position of the document M, or reading the surface of the document M to determine the type of the document M.
[0038]
For example, as shown in FIG. 5A, when the reflection mirror 15a of the first scanning unit 15 is near the leading end of the document M, the first light source 41 is turned off and the second light source 42 is turned on. A short shadow r occurs at the leading end of M, and the short shadow r at the leading end of the document M is read by the CCD 18 via the first scanning unit 15, the second scanning unit, and the imaging lens 17. Conversely, when the first light source 41 is turned on and the second light source 42 is turned off, no shadow is formed on the leading end of the document M.
[0039]
Therefore, when the first light source 41 is turned off and the second light source 42 is turned on during pre-scanning, if the image read by the CCD 18 includes a black area, the black area is It can be regarded as a shadow of the leading end or an image of the document M.
[0040]
When the reflection mirror 15a of the first scanning unit 15 is near the rear end of the document M as shown in FIG. 5B, the first light source 41 is turned on and the second light source 42 is turned off. A short shadow r occurs at the rear end of the document M, and the short shadow r at the rear end of the document M is read by the CCD 18 via the first scanning unit 15, the second scanning unit, and the imaging lens 17. Conversely, when the first light source 41 is turned off and the second light source 42 is turned on, no shadow is produced at the rear end of the document M.
[0041]
For this reason, when the first light source 41 is turned on and the second light source 42 is turned off during pre-scanning, if the image read by the CCD 18 includes a black area, this black area is It can be regarded as a shadow at the rear end or an image of the document M.
[0042]
Further, when the first and second light sources 41 and 42 are simultaneously turned on when the reflection mirror 15a of the first scanning unit 15 is located between the front end and the rear end of the document M, the surface of the document is uniformly illuminated, The surface of the document M is read by the CCD 18 via the first scanning unit 15, the second scanning unit, and the imaging lens 17. When the first and second light sources 41 and 42 are simultaneously turned on when the reflection mirror 15a of the first scanning unit 15 is near one of the front end and the rear end of the document M, the front and rear of the document M are turned on. There is no shadow at either end.
[0043]
For this reason, when the first and second light sources 41 and 42 are turned on during pre-scanning, if the image read by the CCD 18 includes a black area, the black area is regarded as an image of the original M. Can be.
[0044]
FIG. 6 shows the state of the leading end and the trailing end of the original M based on the image read by the CCD 18 when the first and second light sources 41 and 42 are simultaneously turned on and switched on, and the type of the original M is determined. 9 is a flowchart illustrating a process for determining the state of the image.
[0045]
First, at the same time as the start of the pre-scan, the control circuit 40 controls the switch 46 between the first and second inverters 43 and 44 and the power supply 45 to turn on and off, and the first scanning unit 15 as shown in FIG. The lighting cycle of the first and second light sources 41 and 42 is started. This lighting cycle is sufficiently shorter than the pre-scan cycle, and a large number of lighting cycles are repeated through one pre-scan.
[0046]
The control circuit 40 samples the image read by the CCD 18 at the timing when only the first light source 41 is turned on during the pre-scan (step S101), and determines whether or not this image includes a black area. Is determined (step S102). If the image includes a black region (“Yes” in step S102), the control circuit 40 regards the black region as a shadow of the leading edge of the document M or an image of the document M, and The detection flag is set to "1" (step S103). If the image does not include a black area (“No” in step S102), the detection flag of the leading end of the document M is left at “0”.
[0047]
At the timing when only the second light source 42 is turned on (step S104), the control circuit 40 samples the image read by the CCD 18 and determines whether or not this image includes a black area (step S104). Step S105). If a black area is included in the image (“Yes” in step S105), the control circuit 40 regards the black area as a shadow at the rear end of the original M or an image of the original M, and The end detection flag is set to "1" (step S106). If the image does not include a black area ("No" in step S105), the detection flag at the rear end of the document M is left at "0".
[0048]
Further, the control circuit 40 samples the image read by the CCD 18 at the timing when the first and second light sources 41 and 42 are simultaneously turned on (step S107), and determines whether the image includes a black area. Is determined (step S108). If the image includes a black area (“Yes” in step S108), the control circuit 40 determines that the black area is not a shadow of the leading or trailing edge of the document M, but is a shadow of the image of the document M. Thus, the detection flag of the leading edge and the detection flag of the trailing edge of the document M are set to “0” (step S109). If the image does not include a black area ("No" in step S108), the control circuit 40 leaves the detection flag of the leading or trailing edge of the document M as it is.
[0049]
Thereafter, similarly, steps S101 to S109 are repeated from the start to the end of the prescan.
[0050]
At the time of pre-scanning, the CCD 18 first reads the leading edge of the document, then reads the surface of the document, and finally reads the trailing edge of the document. Therefore, the detection flag of the leading edge of the document M is first set to “1”, and then the detection flag of the leading edge and the trailing edge of the document M are set to “0” by the processing of the flowchart of FIG. Finally, the detection flag at the rear end of the document M is set to "1".
[0051]
Therefore, the control unit 42 measures the time from the time when the leading end detection flag is set to “1” to the time when the trailing end detection flag is set to “1”. The speed (movement speed of the first scanning unit 15) is multiplied to determine the distance from the leading edge to the trailing edge of the document M, that is, the size of the document M.
[0052]
When both the leading and trailing edge detection flags are set to “0”, the control unit 42 determines the type of the document M based on the image read by the CCD 18.
[0053]
As described above, in the document reading apparatus 3 of the present embodiment, at the time of pre-scanning, the first and second light sources 41 and 42 of the first scanning unit 15 are periodically and repeatedly switched on and off, while the first and second light sources 41 and 42 are periodically repeated. Since the short shadows at the leading and trailing edges of the document M are read at the center of the two light sources 41 and 42 to detect the leading and trailing edges of the document M, the size of the document can be accurately determined. Further, since two light sources are used, the load per light source can be reduced.
[0054]
By the way, when the first and second light sources 41 and 42 of the first scanning unit 15 are turned on, regardless of the positions of the first and second light sources 41 and 42, both ends of the document separated in a direction orthogonal to the scanning direction are provided. Since each shadow occurs, both ends of the document may be detected and the distance between both ends of the document, that is, the width of the document may be obtained.
[0055]
If the lengths and widths of various standard sizes are stored in a memory in advance, the length of the original is determined, and then the length of the standard size corresponding to the width is calculated to predict the original length. Can be.
[0056]
Further, when the leading edge of the document is detected, both ends of the document are detected at the same time, and the width of the document is obtained, and the length of the standard size corresponding to this width is obtained, and the length of the document is predicted. . Then, based on the detection timing of the leading edge of the document, the predicted length of the document, and the prescan speed, the reading timing near the trailing edge of the document is predicted, and the reading near the trailing edge is detected based on the timing of detecting the leading edge of the document. Until the timing, the first and second light sources 41 and 42 are simultaneously turned on, the surface of the document is read, and the type of the document is determined. Further, at the reading timing near the rear end of the original, the first and second light sources 41 and 42 are switched and turned on, the shadow at the rear end of the original is read, and the rear end of the original is detected. Thus, unnecessary switching lighting of the first and second light sources 41 and 42 is not performed, and the load on the first and second light sources 41 and 42 can be reduced.
[0057]
Note that the present invention is not limited to the above-described embodiment, and can be variously modified. For example, the leading and trailing edges and both ends of the document may be detected during the main scan.
[0058]
【The invention's effect】
As described above, according to the present invention, a document is read while simultaneously turning on each light source for illuminating the document and switching on and off each light source sequentially. When the light sources are turned on at the same time, the surface of the document can be uniformly irradiated, and the surface of the document can be read well. Further, when each light source is switched and lit, light is emitted to the edge of the document from various appropriate angles, so that a short shadow occurs at both the leading edge and the trailing edge of the document. Therefore, the size of the document can be accurately determined by accurately detecting the leading edge and the trailing edge of the document. Further, there is no need to provide a sensor for detecting the leading and trailing edges and size of the document.
[0059]
In addition, since a light source near the scan start position and a light source near the scan end position are provided and the respective light sources are turned on at the same time, the surface of the document can be uniformly irradiated, and the surface of the document can be read well. it can. In addition, since the light source near the scan start position and the light source near the scan end position are selectively turned on to illuminate the leading and trailing edges of the document from an oblique direction, shadows at the leading and trailing edges of the document are generated. Thus, the leading and trailing edges of the document can be detected.
[0060]
Further, at the time of starting the scanning of the document, the both ends of the document separated in a direction orthogonal to the scanning direction are detected, and the rear end position of the document on the scanning end position side is determined based on the width of the document which is the distance between the both ends. Is predicted. During scanning of the document, the light source near the scan start position and the light source near the scan end position are simultaneously turned on at least in a range excluding the vicinity of the rear end of the document. Thus, the surface of the document can be satisfactorily read. Alternatively, during scanning of the original, either the light source near the scan start position or the light source near the scan end position is lit near the rear end of the original, so that the rear end of the original is illuminated obliquely. Then, a shadow of the trailing edge of the document is generated, and the trailing edge of the document can be detected.
[Brief description of the drawings]
FIG. 1 is a side view illustrating an image forming apparatus to which an embodiment of a document reading apparatus according to the present invention is applied.
FIG. 2 is a side view schematically showing the document reading apparatus according to the embodiment.
FIG. 3 is a circuit diagram illustrating an inverter device of the document reading apparatus according to the embodiment.
FIG. 4A is a diagram showing a lighting sequence of first and second light sources of a first scanning unit at the time of main scanning, and FIG. 4B is a diagram showing first and second light sources of the first scanning unit at the time of pre-scanning; It is a figure which shows the lighting sequence of a light source.
5A is a diagram showing a shadow of a leading end of a document when the second light source of the first scanning unit is turned on, and FIG. 5B is a diagram showing a rear end of the document when the first light source of the first scanning unit is turned on. It is a figure showing a shadow.
FIG. 6 is a flowchart illustrating a process performed by the document reading apparatus according to the embodiment.
FIG. 7A is a diagram illustrating a shadow at the leading edge of a document in a conventional apparatus, and FIG. 7B is a diagram illustrating a shadow at a trailing edge of the document.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 Image forming apparatus 2 Document transport unit 3 Document reader 4 Printing unit 5 Recording paper transport unit 6 Paper feed unit 7 Paper discharge tray 15 First scanning unit 16 Second scanning unit 17 Imaging lens 18 CCD
40 control circuit 41 first light source 42 second light source 43 first inverter 44 second inverter 45 power supply 46 switch

Claims (9)

In a document reading device that reads a document while irradiating the document with light,
A plurality of light sources for irradiating light to the original,
A document reading apparatus comprising: a control unit for reading a document while sequentially turning on each light source and switching on each light source sequentially. 2. The document reading apparatus according to claim 1, wherein the light sources are arranged side by side in a scanning direction of the document, and a light source near a scan start position and a light source near a scan end position are provided. 3. The document reading apparatus according to claim 2, wherein the control unit simultaneously turns on the light source near the scan start position and the light source near the scan end position to read the document. 3. The document reading apparatus according to claim 2, wherein the control unit selectively turns on a light source near the scan start position and a light source near the scan end position to detect an end of the document. The control means turns on either the light source near the scan start position or the light source near the scan end position when starting scanning of the document, and detects the leading edge of the document on the scan start position side and separates the light source in a direction perpendicular to the scanning direction. 3. The document reading apparatus according to claim 2, wherein both ends of the read document are detected. The control means detects the both ends of the document separated in a direction perpendicular to the scanning direction at the start of scanning of the document, and based on the width of the document which is the distance between the both ends, the control unit detects A rear end position is predicted, and a light source near a scan start position and a light source near a scan end position are simultaneously turned on during scanning of a document, at least in a range excluding the vicinity of the rear end of the document. Item 6. The document reading device according to Item 5. The control means detects the both ends of the document separated in a direction perpendicular to the scanning direction at the start of scanning of the document, and based on the width of the document which is the distance between the both ends, the control unit detects 6. A rear end position is predicted, and during scanning of a document, one of a light source near a scan start position and a light source near a scan end position is turned on near the rear end of the document. 2. The document reading device according to 1. 2. The document reading apparatus according to claim 1, wherein the control unit reads the document while sequentially turning on each light source and switching on each light source sequentially during prescanning of the document. In a document reading method of reading a document while irradiating the document with light,
An original reading method, wherein an original is read while simultaneously turning on a plurality of light sources for irradiating the original and sequentially switching on and off the respective light sources.

Images