Patent Application
20110043874
The present invention relates to an image reading apparatus and, in particular, to an image reading apparatus, an image formation apparatus, method and program product which eliminate the effect of outside light on an image of an original in a so-called sky-shot in which the original is read with the platen cover open.
A platen glass (original reading surface) of an image reading apparatus of a copying machine and the like is conventionally provided with an openable and closeable platen cover that covers an original placed on the platen glass.
Typically, a thin original is read with the platen cover closed to cut off outside light whereas a thick original such as a book is read with a platen cover open in a so-called sky-shot. In the sky-shot, outside light cannot be cut off by the platen cover and the effect of outside light incident on the platen glass cause a problem that a wrong original range is read and the size of the original is not correctly recognized.
In order to address the problem, Patent Document 1, for example, proposes an image reading apparatus which includes control unit for, each time a scan line is to be read, turning off a light source and causing an image reading section to read outside light information entering a platen with a cover open and with an original placed on the platen, then turning on the light source and causing the image reading section to read an image of the original, and image processing circuit for eliminating the effect of outside light detected from the read image of the original on the basis of the outside light information.
Although the method for detecting the size of the original described in Patent Document 1 can detect the size of the original, the detection method requires, every time a scan line is read, turning off the light source and causing the image reading section to read outside light information entering the platen and then turning on the light source and causing the image reading section to read the image of the original. Accordingly, the method requires a long scanning time.
The present invention has been made in light of these circumstances and an object of the present invention is to provide an image reading apparatus and others which accurately detect the size of an original to read the original while eliminating the effect of outside light incident on a platen glass in a sky-shot, and reduce the time for detecting the size of the original and increase the efficiency.
Patent Document 1: Japanese Laid-open Patent Publication No. 2007-28413
According to the present invention, there is provided an image reading apparatus including a platen on which an original is to be placed, an openable and closeable cover for covering the platen, an original illuminating light source, a plurality of photoelectric conversion elements mounted on a sensor board, and an image formation element array including a plurality of image formation elements arranged in an array, the image reading apparatus including: white reference detector for generating a white reference value acting as a white reference during original reading; detector for detecting an output signal from the photoelectric conversion elements when an operation to read the original is performed with the cover open; comparator for comparing the output signal with the white reference value on a scan-line-by-scan-line basis; and controller for adding an original reading operation to be performed with the original illuminating light source turned off during an original reading operation on a scan-line-by-scan-line basis if the comparison by the comparator shows that a value greater than or equal to the white reference value exists in the output signal.
An image formation apparatus according to the present invention includes the image reading apparatus described above and image processor for eliminating an area other than an image of an original that is contained in a read image obtained through an original reading operation by the image reading apparatus.
According to the present invention, there is provided an image reading method in an image reading apparatus including a platen on which an original is to be placed, an openable and closeable cover for covering the platen, an original illuminating light source, a plurality of photoelectric conversion elements mounted on a sensor board, and an image formation element array including a plurality of image formation elements arranged in an array, the image reading method including: white reference detection step of generating a white reference value acting as a white reference during original reading; detection step of detecting an output signal from the photoelectric conversion elements when an operation to read the original is performed with the cover open; comparison step of comparing the output signal with the white reference value on a scan-line-by-scan-line basis; and control step of adding an original reading operation to be performed with the original illuminating light source turned off during an original reading operation on a scan-line-by-scan-line basis if the comparison at the comparison step shows that a value greater than or equal to the white reference value exists in the output signal.
According to the present invention, there is provided an image formation method in an image formation apparatus including a platen on which an original is to be placed, an openable and closeable cover for covering the platen, an original illuminating light source, a plurality of photoelectric conversion elements mounted on a sensor board, and an image formation element array including a plurality of image formation elements arranged in an array, the image formation method including: white reference detection step of generating a white reference value acting as a white reference during original reading; detection step of detecting an output signal from the photoelectric conversion elements when an operation to read the original is performed with the cover open; comparison step of comparing the output signal with the white reference value on a scan-line-by-scan-line basis; control step of adding an original reading operation to be performed with the original illuminating light source turned off during an original reading operation if the comparison at the comparison step shows that a value greater than or equal to the white reference value exists in the output signal; and image processing step of eliminating an area other than an image of an original that is contained in a read image obtained through an original reading operation.
A program product according to the present invention causes a computer to execute the steps of the image reading method described above.
A program product according to the invention causes a computer to execute the steps of the image formation method described above.
According to the present invention described above, an output signal of a read image is compared with a white reference value in a so-called sky-shot in which the original is read with a cover that covers a platen open, and if a value greater or equal to the white reference value exists in the output signal of the read image, a reading operation performed with the light source turned off is added to each reading operation to read one scan line, thereby reducing the time required for detecting the size of the original and increasing the efficiency.
An exemplary copying machine incorporating an image reading apparatus according to the present invention will be described as an embodiment of the present invention with reference to drawings.
The image reading section 30 includes a platen glass 31 as a platen, an openable and closeable platen cover 32 provided to cover an original 34 placed on the platen glass 31, and an image sensor unit 33 which is a contact image sensor (CIS) unit as an image reading apparatus.
As illustrated in
Reference numeral 36 denotes a light guide which guides light emitted from the light source unit 35 to the original 34. Reference numeral 37 denotes a rod lens array 37 which is an image formation element array. Reference numeral 38 denotes a sensor board 38 which is a board on which photoelectric conversion elements 39k (where k is a natural number in the range from 1 to 8) are mounted.
The photoelectric conversion elements 39k convert reflected light (an image of an original) focused by the rod lens array 37 to an output signal. While provided in the present embodiment, any number of photoelectric conversion elements 39k may be provided.
Reference numeral 40 in
When an image reading operation is initiated in the configuration, first a control unit 100 disposed in the image formation section 50 issues an instruction to generate data acting as a white reference value and turn on the light-emitting elements 35r, 35g and 35b provided in the light source unit 35 one after another to cause them to emit light so that the emitted light illuminates the surface of the white reference member 40 through light guide 36. The emitted light is reflected by the white reference member 40 and is focused on the photoelectric conversion elements 39k provided on the sensor board 38 through the rod lens array 37 to form an image. By reading one scan line of all of RGB rays of the reflected light in the main scanning direction, data acting as a white reference value is generated. Then the image sensor unit 33 is moved in a sub scanning direction to the original reading start position.
At the original reading start position, the light-emitting elements 35r, 35g and 35b provided in the light source unit 35 are turned on one after another to substantially uniformly illuminate the surface of the original 34 through the light guide 36 in linear manner in the main scanning direction with emitted light. The illuminating light is reflected by the original 34 and is focused on the photoelectric conversion elements 39k provided on the sensor board 38 by the rod lens array 37 to form an image. An operation to read one scan line of the reflected light from the original 34 is accomplished by reading one scan line of all of RGB rays of the reflected light.
After one scan line has been read, the image sensor unit 33 performs the operation of reading another scan line while moving by one scan line in the sub scanning direction and illuminating the original 34 with light. By repeating the reading operation, the entire surface of the original 34 is scanned. In this way, the original is read scan-line by scan-line (normal reading).
The white reference value is a reference value used in shading correction and is data corresponding to an image having a uniform white concentration distribution. The shading correction is applied to an image of an original 34 in order to increase reproducibility of the shades of gray of the original 34. Specifically, light amount adjustment for adjusting the amount of emission of light illuminating the original 34 from the light source unit 35 through the light guide 36 is performed and gain adjustment for adjusting the gain of an image signal output from the photoelectric conversion elements 39k is performed. In addition, unevenness of the amount of light in the light source unit 35 and the rod lens array 37 and unevenness of sensitivity of the photoelectric conversion elements 39k are corrected pixel by pixel.
Reflected light from the original 34 is converted by the photoelectric conversion elements 39k to an output signal and then is output to the control unit 100, where image processing based on the white reference value, which will be described later, is applied to the signal, and the resulting signal is output to an image formation section 50 as image print data.
The image formation section 50 has the function of the so-called printer (output device) and has the following configuration.
As illustrated in
The paper feed tray 51 can contain sheets of a predetermined size and feeds the sheets as the image formation section 50 forms an image. The transfer unit 53 forms an electrostatic latent image from image print data subjected to image processing in the control unit 100 and causes toner to adhere to the electrostatic latent image to form a toner image. The toner image is transferred onto the intermediate transfer belt 54 and then onto a sheet, which is then pressed and heated by the fuser unit 55 to fix the toner image on the sheet, thereby printing the image.
The rod lens array 37 is an optical component including multiple tiny rod lenses 41 which are image formation elements, arranged in an array in such a manner that their optical axes are in parallel with one another and fixed with an opaque resin, and together generate a single continuous 100%-scale erected real image.
The rod lens array 37 has a structure that eliminates outside light incident on the rod lens array 37 at an angle greater than an aperture angle a depicted in
When incident outside light, for example light from a fluorescent lamp, is outside the aperture angle a of the rod lens array 37 having the structure described above, the illuminance of the outside light entering the rod lens array 37 through the platen glass 31 will change.
Accordingly, there is a problem that even if the illuminance around the copying machine 1 does not change, the illuminance of outside light entering the aperture angle a of the rod lens array 37 through the platen glass 31 can change due to movement of the image sensor unit 33.
Illustration 401 represents an image of the original 34 that was read under conditions where the output signal of outside light entering the aperture angle a of the rod lens array 37 had a value less than or equal to the white reference value and the light source unit 35 was turned off.
Illustration 402 represents an image of the original 34 that was read under conditions where there was a value greater than or equal to the white reference value in the output signal of outside light entering the aperture angle a of the rod lens array 37 and the light source unit 35 was turned off.
Illustration 403 represents an image of the original 34 that was read under conditions where the output signal of outside light entering the aperture angle a of the rod lens array 37 had the value less than or equal to the white reference value and the light source unit 35 was turned on.
Illustration 404 represents an image of the original 34 that was read under conditions where there is a value greater than or equal to the white reference value in the output signal of outside light entering the aperture angle a of the rod lens array 37 and the light source unit 35 is turned on.
In illustration 402 in
In illustration 403, the value of the output signal of reflected light from the original 34 and the value of the output signal of outside light entering the aperture angle a of the rod lens array through the platen glass 31 are detected to less than or equal to the white reference value. Therefore, this case indicates that the region where the outside light is incident is erroneously detected as a black image and a boundary is generated between the reflected light from the original 34 and the outside light region.
In this way, the boundary of the original 34 can be identified under the conditions in illustrations 402 and 403. Therefore the edges of the original 34 can be detected during a sky-shot. However, under the conditions in illustrations 401 and 404, the boundary of the original 34 cannot be detected and therefore the edges of the original 34 cannot be detected during a sky-shot.
When sky-shot is performed under the conditions in illustrations 401 and 404, the region of the original 34 can be erroneously detected because of the effect of outside light entering the aperture angle a of the rod lens array 37. For example, if the area erroneously detected is outside the region of the original 34, a black region remains in a printed image; if the area erroneously detected is inside the region of the original 34, a portion of a printed image is deleted. Therefore, under the conditions in illustrations 401 and 404, the light source unit 35 needs to be turned on or off to detect the boundary. It should be noted that the frames in
Here, the light source unit 35 performs color reading by switching the light-emitting elements. The switching of the light-emitting elements is driven in a time-division manner by a control circuit 103 provided in the control unit 100, which will be described later. For example, the light-emitting elements are independently turned on in the order R→G→B each time an operation to read one scan line is performed. When a monochrome original such as a text document is read, the original can be read by turning on only one or both of the light-emitting elements 35r and 35g. In this case, since the light-emitting element 35b is not turned on, the reading speed can be increased and power consumption can be saved.
It is assumed in the present embodiment that when color reading is performed, a light-emitting-element turn-off state (D) is included in the turn-on sequence, like R→G→B→D, for example, thereby adding an operation to read one scan line of the original 34 with the light source unit 35 turned off. It is also assumed that when monochrome reading is performed, the sequence G→D, for example, is performed to add an operation to read one scan line of the original 34 with the light source unit 35 turned off.
In the present embodiment, an output signal of outside light entering the aperture angle a of the rod lens array 37 is detected and the light source unit 35 is turned on and off for correct recognition of original size.
In the configuration of the present embodiment described above, there is an output difference in output signal output from the photoelectric conversion elements 39k between reflected light from an original 34 and the region of outside light. Therefore, as illustrated in
A configuration and operation of the control unit 100 which performs image processing in the image reading apparatus to which the present invention can be applied will be described in detail with reference to
The control unit 100 includes a detection circuit 101, which is detection means, a comparison circuit 102, which is comparison means, a control circuit 103, which is control means, and an image processing circuit 104, which is image processing means.
When a reading operation is initiated in this configuration, first the light source unit 35 is turned on and one scan line of reflected light from the white reference member 40 is read by the detection circuit 101 to generate data that acts as a white reference value. The white reference value data is output to the comparison circuit 102 and the image processing circuit 104.
Then, the image sensor unit 33 is moved to the original reading start position. A platen cover open/closed sensor, not illustrated, determines whether the platen cover 32 is open or closed. If the platen cover 32 is open, the control circuit 103 determines that the image reading process is to be performed with sky-shot.
Then, the control circuit 103 causes the detection circuit 101 to turn on the light source unit 35 to perform an operation to read one scan line to detect a read image (reflected light from the original 34 and outside light entering the aperture angle a of the rod lens array 37 through the platen glass 31) and outputs the read image to the comparison circuit 102 and the image processing circuit 104 as an output signal. The read image output to the comparison circuit 102 as the output signal of the read image is compared with the white reference value.
If the comparison shows that a value greater than or equal to the white reference value exists in the output signal of the read image, an operation to read one scan line of the reflected light from the original 34 is performed with the light source unit turned off and the read data is output to the image processing circuit 104 as data for detecting the edges of the original 34.
Then, image sensor unit 33 again detects a read image while moving in the sub scanning direction by one scan line, and outputs the read image to the comparison circuit 102 and the image processing circuit 104 as an output signal. Again, the read image is compared with the white reference value at the comparison circuit 102. If there is not a change in the relation between the read image and the white reference value, the sequence of the operation of reading one scan line with the light source unit 35 turned off and outputting to the image processing circuit 104 is repeated each time an operation to read one scan line is performed until all data is read.
As a result, the read image as reflected light read with the light source unit 35 turned on and the read image as data for detecting the edges of the original read with the light source unit 35 turned off are output to the image processing circuit 104.
On the other hand, if the value of the output signal of the read image is less than or equal to the white reference value, the image sensor unit 33 again detects a read image while moving in the sub scanning direction by one scan line, and outputs the read image to the comparison circuit 102 and the image processing circuit 104 as an output signal. The read image is compared with the white reference value at the comparison circuit 102. If there is not a change in relation between the output signal of the read image and the white reference value, the edges of the original can be detected from the read image and therefore the read image reading operation is repeated until all data has been read.
The read image output to the image processing circuit 104 is subjected to shading correction, then to original edge detection for detecting the boundary between the region of reflected light from the original 34 and the region of outside light, and white masking is performed on the basis of the detected edges of the original to mask the region of the outside light. The resulting read image is output to the image formation section as image print data. The image formation section prints the image on the basis of the output image print data. The white masking is processing to mask the region of outside light on the basis of the detected edges of the original to eliminate the region of the outside light from the print range in the image print data.
As illustrated in
The detection circuit 101 reads one scan line of reflected light from the white reference member 40 to generate a white reference value and outputs the white reference value to the comparison circuit 102 and the image processing circuit 104 (step S201). Then the control circuit 103 moves the image sensor unit 33 in the sub scanning direction.
Then, the control circuit 103 determines, on the basis of a detection signal provided from the platen cover open/closed sensor (not illustrated), whether the platen cover 32 is open or closed (step S202). If the control circuit 103 determines that the platen cover 32 is closed (step S202: NO), the control circuit 103 determines that the reading operation is normal reading for reading the original with the platen cover 32 closed rather than sky-shot, and proceeds to normal processing (step S203).
On the other hand, the control circuit 103 determines that the platen cover 32 is open (step S202: YES), the control circuit 103 determines that the reading operation is sky-shot and directs the detection circuit 101 to perform an operation to read one scan line of the reading surface of the platen glass 31 (step S204). The control circuit 103 controls the movement of the image sensor unit 33 in the sub scanning direction and also controls the timings of turning on and off of the LEDs of the light source unit 35. Thus, one scan line of reflected light from the original 34 is read with the light-emitting elements of the light source unit 35 turned on.
Then the detection circuit 101 outputs the read image of the scan line to the comparison circuit 102 and the image processing circuit 104. The comparison circuit 102 receives the white reference value and the read image and compares the output signal of the read image with the white reference value (step S205).
Here, if there is a value in the output signal of the read image that is greater than or equal to the white reference value (step S205: YES), an operation to read one scan line of reflected light from the original 34 is performed at the same location with the LEDs of the light source unit 35 turned off by the control circuit 103 and the read image is output to the image processing circuit 104 as data for detecting the edges of the original 34 (step S206).
Then, the control circuit 103 determines whether scanning of the entire original 34 in the sub scanning direction has been completed or not (step S207). If the scanning has not been completed (step S207: NO), the control circuit 103 returns to step S204 and repeats the process from step S204 through step S207. If the scanning has been completed (step S208: YES), the process will end.
On the other hand, if the value of the output signal of the read image is less than or equal to the white reference value (step S205: NO), the control circuit 103 determines whether the scanning of the entire original 34 in the sub scanning direction has been completed or not (step S210). If the scanning has not been completed (step S208: NO), the control circuit 103 returns to step S204 and repeats the process in steps S204 S205 and S208. If the scanning has been completed (step S208: YES), the process will end.
If there is a change in the relation between the output signal of the read image and the white reference value before the scanning in the sub scanning direction of the entire image 34 has been completed at step S205, the process proceeds to steps S204 through S207 or steps S204 S205 and S208 depending on the result of step S205.
When the image processing circuit 104 receives all output signals of the scanned read image, the image processing circuit 104 applies shading correction to the read image on the basis of the white reference value and then performs original edge detection to detect the boundary between the region of the reflected light from the original 34 and the region of outside light (step S209).
The image processing circuit 104 uses a mask signal to perform white masking of the region of outside light on the basis of the edges of the original detected at step S209 and outputs the result to the image formation section 50 as image print data (step S210).
Then, the image formation section 50 prints the image on the basis of the image print data output from the image processing circuit 104 (step S211). With this, sky-shot image reading will end (step S212).
In this way, according to the present embodiment, when image processing is performed in the so-called sky-shot in which an original is read with the platen cover open, a white reference value read from the white reference member 40 is compared with the output signal of a read image containing reflected light from the original 34 and outside light entering the aperture angle a of the rod lens array 37 through the platen glass 31. Only if the comparison shows that a value greater than or equal to the whiter reference value exists in the output signal of the read image, an operation to read one scan line with the light source unit 35 turned off is added to an operation to read one scan line with the light source unit 35 turned on.
With the configuration, according to the present embodiment, the edges of an original 34 can be detected by recognizing the size of the original on the basis of the boundary between the region of reflected light from the original 34 and the region of outside light regardless of the illuminance around the copying machine 1, and white masking can be applied to the region of the outside light around the original 34. Accordingly, the effect of outside light other than the reflected light from the light source unit 35 can be eliminated from an image of the original during sky-shot. In addition, since an image reading operation is performed with the light turned off as necessary, the time required for original size detection can be reduced and the efficiency can be increased.
Furthermore, since the function of detection control supporting sky-shot can be added simply by making a minor modification to the image sensor unit and an image processing program rather than a major modification, the functionality of the copying machine 1 can be improved at low cost.
Since comparison between the white reference value and the output signal of a read image is performed each time an operation to read one scan line is performed, a quick response can be made to a change in illuminance around the copying machine 1 and the effect of outside light can be eliminated to allow the original to be reliably read.
While the contact image sensor unit is used in the image reading section in the present embodiment, a minification optical system image sensor unit may be used instead.
Light-emitting elements provided in the light source unit 35 may be white light sources and RGB filters may be used to accomplish color reading. In this case, the same effects that have been described above can be provided by repeating an operation to read one scan line with light turned on and an operation to read one scan line with light turned off.
The present invention is a technique useful for image reading apparatuses of image scanners, facsimile machines, copying machines and the like.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/058580 | 5/1/2009 | WO | 00 | 9/10/2010 |
