Image forming apparatus and control method thereof

An image forming apparatus including: a reflection member to reflect light at a first position spaced a predetermined distance from a scan glass; a moving unit to move the reflection member between the first position and a second position; and a control unit to generate initial reference data from an image signal transmitted from a scanning device to receive the light reflected by the reflection member. When the initial reference data is not suitable for shading correction, the control unit controls the moving unit to move the reflection member to the second position for reference data reacquisition.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2007-125978, filed Dec. 6, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate to an image forming apparatus that performs shading correction to prevent quality deterioration of image data and a control method thereof.

2. Description of the Related Art

Generally, an image forming apparatus (such as a digital multifunction machine, a copying machine, a scanner, and a facsimile) includes a scanning device to scan image data of a document. The scanning device emits light from a light source to the document and photoelectrically converts the light reflected from the document through an image sensor to generate an image signal.

During the generation of the image signal of the document, the image signal may be distorted due to a deviation of the light source or a non-uniformity of light quantity. The distortion of the image signal is known as a shading phenomenon.

A general image forming apparatus performs shading correction to compensate for the distortion of the image signal. The shading correction includes an image processing operation that compares image data of a document with reference data to decide a white pixel value or a black pixel value, and corrects an abnormal pixel with values of surrounding pixels. The reference data is image data read from a white reference plane before the image of the document is acquired.

According to the conventional art, the shading correction is performed on the abnormal pixel irrespective of whether the abnormal pixel is generated due to contamination of the white reference plane or contamination of a scan glass or an optical path.

The abnormal pixel generated due to the contamination of the scan glass or the optical path is repetitively generated whenever the document is scanned. For this reason, shading correction is performed to prevent quality deterioration.

However, when reference data is acquired from a white reference plane of a white bar disposed above the scan glass, the quality of the image data of the document may not be deteriorated, because the scanning process is carried out while the document is located between the white bar and the scan glass. Consequently, when the shading correction is performed within the range in which the abnormal pixel is generated, the quality of the image data of the document deteriorates.

SUMMARY OF THE INVENTION

Aspects of the present invention provide an image forming apparatus and a method of controlling the same that prevent unnecessary shading correction of an abnormal pixel generated due to the contamination of a white bar.

According to an aspect of the present invention, there is provided an image forming apparatus having a scan glass and a scanning device to generate image data of a document placed on the scan glass, the image forming apparatus including: a reflection member to reflect light to the scanning device when the reflection member is at a first position spaced a first predetermined distance from the scan glass; a moving unit to move the reflection member between the first position and a second position spaced a second predetermined distance from the scan glass; and a control unit to determine whether first image data generated from the light reflected off of the reflection member and received by the scanning device when the reflection member is in the first position is suitable for image correction, and to control the moving unit to move the reflection member to the second position to generate second image data when the first image data is not suitable for the image correction.

The moving unit may include a solenoid coupled to the reflection member to move the reflection member between the first and second positions when the solenoid is energized.

The control unit may determine whether the image data of the document is to be corrected according to a difference between a level of one or more abnormal pixels included in the first image data and a level of the one or more abnormal pixels included in the second image data.

The control unit may not correct the image data of the document when it is determined that the first image data is not suitable due to contamination of the reflection member.

The reflection member may have a white-colored surface facing a first side of the scan glass, while the scanning device may be located at a second side of the scan glass, opposite the first side.

According to another aspect of the present invention, there is provided a control method of an image forming apparatus having a scan glass and a scanning device to generate image data of a document placed on the scan glass, the control method including: reflecting light from a reflection member of the image forming apparatus to the scanning device when the reflection member is at a first position spaced a first predetermined distance from the scan glass; generating first image data from the light reflected from the reflection member and received by the scanning device when the reflection member is in the first position: determining whether the first image data is suitable for image correction on the image data of the document; and moving the reflection member from the first position to a second position to generate second image data when the first image data is not suitable for the image correction.

The determining of whether the first image data is suitable includes determining whether the first image data is suitable based on an abnormal pixel included in the waveform of an image signal corresponding to the data.

The control method may further include determining a difference between a level of an abnormal pixel included in the first image data and a level of the abnormal pixel included in the second image data and determining whether the data is to be corrected according to the difference.

The image data of the document may not be corrected when the difference between the levels is greater than a predetermined value.

The abnormal pixel may be determined to result from contamination of the reflection member when the difference between the levels is greater than the predetermined value.

The image data of the document may be corrected when the difference between the levels is less than a predetermined value.

The abnormal pixels may be determined to have been generated due to contamination of the scan glass or an optical path of the scanning device when the difference between the levels is less than the predetermined value.

According to yet another aspect of the present invention, there is provided a control method of an image forming apparatus having a scan glass, a reflection member, and a scanning device to generate image data of a document placed on the scan glass between the scan glass and the reflection member, the control method including: determining whether first reference data generated from light reflected off of the reflection member and received by the scanning device when the reflection member is in a first position is suitable for image correction; if the first reference data is not suitable for the image correction, determining whether the first reference data is not suitable for the image correction because of the reflection member; and determining that the image data of the document is not to be corrected if the first reference data is determined to not be suitable for the image correction because of the reflection member.

According to still another aspect of the present invention, there is provided an image forming apparatus having a scan glass and a scanning device to generate image data of a document placed on the scan glass, the image forming apparatus including: a reflection member to reflect light to the scanning device when the reflection member is spaced a first predetermined distance from the scan glass; and a control unit to determine whether first image data generated from the light reflected off of the reflection member and received by the scanning device when the reflection member is spaced the first predetermined distance from the scan glass is suitable for image correction, and to control the reflection member, the scanning device, and/or the scan glass such that the reflection member is spaced a second predetermined distance from the scan glass, different from the first predetermined distance, to generate second image data when the first image data is not suitable for the image correction.

According to another aspect of the present invention, there is provided an image forming apparatus having a scan glass and a scanning device to generate image data of a document placed on the scan glass, the image forming apparatus including: a reflection member to reflect light to the scanning device when the reflection member is spaced a first predetermined distance from the scan glass, and to reflect light to the scanning device when the reflection member is spaced a second predetermined distance from the scan glass, different from the first predetermined distance; and a control unit to generate first image data from the light reflected off of the reflection member when the reflection member is spaced the first predetermined distance from the scan glass, to generate second image data from the light reflected off of the reflection member when the reflection member is spaced the second predetermined distance from the scan glass, and to compare the first image data to the second image data in order to determine if the image data of the document is to be corrected.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a view schematically illustrating a structure of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus includes a scanning device to acquire the image of a document. According to how the document is fed for scanning, the scanning device may generally be classified as a flat bed type scanning device or a sheet feed type scanning device.

Referring toFIG. 1, the image forming apparatus includes a sheet feed type automatic document feeder (ADF) to automatically move a document to a scanning position.

Specifically, a document1to be scanned is placed on a document loading plate10. The document1, placed on the document loading plate10, is supplied to a document feed path11by a paper supply unit (not shown). Feed motors12and13to drive a plurality of feed rollers and a document detection sensor14to detect the document being fed are mounted on or in proximity to the document feed path.

Furthermore, a scan glass40is mounted at one end of the document feed path11. A white bar20is disposed above the scan glass40as a reflection member, and a scanning device50is disposed below the scan glass40.

The scanning device50includes a light source51to emit light, a light guide member52to reflect the emitted light, and an image sensor53to receive the reflected light and output the waveform of an image signal. It is understood that according to other embodiments, the light guide member52may be omitted, or more than one light guide member52may be included to guide the light to the image sensor53. The scanning device50may further include a condensing lens (not shown) to condense light. A contact image sensor may be used as an image sensor. However, it is understood that aspects of the present invention are not limited thereto. For example, a charge coupled device (CCD) may alternatively be used.

The white bar20guides the document1being fed along the document feed path11. The white bar20has a bottom21that is a white reference face used for shading correction. Furthermore, the white bar20is coupled to a moving unit30.

The moving unit30includes a case31having an inner space into and out of which a solenoid32moves, and an elastic member33connected between the solenoid32and the white bar20to elastically support the document depending upon the thickness of the document. The solenoid32rises, when the solenoid32is energized, and lowers when the energizing of the solenoid32is interrupted under the control of a control unit, which will be described below.

FIG. 2is a block diagram of an image forming apparatus according to an embodiment of the present invention. Referring toFIG. 2, the image forming apparatus includes feed motors12and13, a document detection sensor14, a solenoid32, a light source51, an image sensor53, a manipulation panel60, a control unit70, a memory71, a motor drive unit80, a solenoid drive unit90, and a light source module drive unit100. The manipulation panel60may be mounted at an outside surface of the apparatus such that a user can conveniently manipulate the manipulation panel60. The manipulation panel60includes an input unit61to allow a user to input a command and a display unit62to display information of the inputted command and information of an operating state of the image forming apparatus. The input unit61and the display unit62may be integrated into one unit, such as a touch screen on which an input is received according to a touch of the user.

When the document1is placed on the document loading plate10, the control unit70controls the motor drive unit80to drive the first feed motor12and/or the second feed motor13such that the document1is fed by the first feed motor12and/or the second feed motor13. The document detection sensor14detects the document1being fed and provides the detection result to the control unit70.

When the document1is located between the white bar20and the scan glass40, the control unit70controls the light source module drive unit100to emit light from the light source51to the document1. The light emitted from the light source51is reflected by the document1and inputted to the scanning device50. The reflected light, inputted to the scanning device50, is guided to the image sensor53by the light guide member52. As described above, it is understood that according to other aspects, the light guide member52may be omitted, or more than one light guide member52may be included.

The image sensor53provides the waveform of an image signal to the control unit70. The control unit70digitizes the waveform of the image signal inputted thereto, and performs image correction (such as shading correction and background treatment). The memory71stores reference data used for the image correction. When the image correction is completed, the control unit70may transmit the scanned image data to a host computer via an interface unit (not shown), perform a printing operation using a printer engine module (not shown), and/or transmit the scanned image data via a network using a communication connection module.

Hereinafter, an operation of acquiring the reference data will be described. Before the document1is fed, the control unit70controls the light source51to emit light to the bottom21of the white bar20through the light source module drive unit100. The light, reflected by the bottom21, is inputted to the scanning device50via the scan glass40. The image sensor53receives the light reflected from the bottom21and provides the waveform of an image signal to the control unit70.

The control unit70digitizes the waveform of the image signal and determines whether the digitized waveform is recognized as reference data. When the digitized waveform is recognized as the reference data, the digitized waveform is stored in the memory71. Whether the digitized waveform is recognized as the reference data is determined according to whether an abnormal pixel exists. When no abnormal pixel exists, the digitized waveform is directly recognized as the reference data.

When an abnormal pixel E1exists in a signal waveform S1corresponding to the initially acquired reference data, as shown inFIG. 4A, the white bar20is moved to reacquire the reference data. Then, the reacquired digitized waveform is recognized as the reference data according to a change in a level of the abnormal pixels.

FIG. 3is a view illustrating a movement of a white bar according to an embodiment of the present invention. Referring toFIG. 3, when the reference data is initially acquired, the white bar20is located at a position spaced a reference distance D1from the scan glass40. When the reference data is reacquired, the control unit70energizes the solenoid32through a solenoid drive unit90to raise the white bar20. At this time, the white bar20is moved within an effective range T between the reference distance D1and the maximum distance Dmax. Preferably, the white bar20is located at a position spaced the maximum distance Dmax from the scan glass40. Here, the maximum distance may be the distance to the farthest position from which the scanning device50can recognize when the white bar20becomes more distant from the scan glass40.

Referring toFIG. 4B, when an abnormal pixel E2exists in a signal waveform S2corresponding to the reacquired reference data, the control unit70compares the level of this abnormal pixel E2with the level of the initial abnormal pixel E1(illustrated inFIG. 4A). When the change in level of the abnormal pixels is large, the control unit70recognizes that the recognition ability of the scanning device50has been affected by the movement of the white bar20. Specifically, when the bottom21of the white bar20is contaminated due to scratches, the level of the abnormal pixel E2of the signal waveform S2corresponding to the reference data reacquired from the light reflected by the bottom21and inputted to the scanning device50as the white bar20becomes more distant from the scan glass40decreases in proportion to the distance in which the white bar is moved. At this time, the change in level of the abnormal pixels is large.

As shown inFIG. 4C, the level of an abnormal pixel E2of a signal waveform S2corresponding to the reference data acquired from the light reflected by the bottom21and inputted to the scanning device50decreases as the white bar20becomes more distant from the scan glass40. As can be seen, however, the change in level of the abnormal pixels is relatively small. Specifically, when the abnormal pixel is generated due to scratches on the surface of the scan glass40or contamination caused by dust on the optical path in the scanning device, to which the reflected light is inputted, the level of the abnormal pixel of the reacquired reference data does not greatly decrease, if at all. In this case, the reference data is corrected. The correction of the reference data is performed using the values of pixels around the abnormal pixel. However, it is understood that aspects of the present invention are not limited thereto. For example, alternatively, the reference data may be corrected with the mean value of the surrounding pixels. Also, the control unit70may display a cause of the abnormal pixel through the display unit62so that a user can act accordingly.

FIG. 5is a flow chart illustrating a control method of an image forming apparatus according to an embodiment of the present invention. Referring toFIGS. 2,3, and5, to perform shading correction with respect to image data of a document1, reference data is acquired prior to acquiring the image data of the document.

The control unit70controls the light source module drive unit100to emit light from the light source51to the bottom21of the white bar20, before the document1is placed thereon, and initially acquires reference data of an image signal from the image sensor53of the scanning device50, to which light reflected by the bottom21is inputted in operation200.

The control unit70determines whether an abnormal pixel exists in a signal waveform corresponding to the initially acquired reference data in operation202. When it is determined that no abnormal pixel exists in the reference data (operation202), the initially acquired reference data is recognized as reference data for shading correction and is stored in the memory71in operation203. The reference data stored in the memory71is used to perform shading correction on the image data of the document hereafter.

When it is determined that an abnormal pixel exists in the reference data (operation202) (i.e., an abnormal pixel E1having a level different from those of the surrounding pixels exists in a signal waveform S1, as shown inFIG. 4A), the initially acquired reference data is not recognized as the reference data for shading correction, and the white bar20is moved to reacquire the reference data in operation204. Specifically, the control unit70controls the solenoid drive unit90to energize the solenoid32. As a result, the white bar20connected to one side of the solenoid32is raised. When the white bar20is moved to a position spaced the maximum distance Dmax from the scan glass40, the energizing of the solenoid32is interrupted. It is understood that aspects of the present invention are not limited to reacquiring the reference data from a position that is higher than an initial position. According to other aspects, the reacquired reference data may be acquired from a position closer to the scan glass than the initial position.

Subsequently, the control unit70emits light from the light sources51to the bottom21of the white bar20and receives an image signal from the image sensor53of the scanning device50, to which the light reflected by the bottom21is inputted, to reacquire the reference data in operation206.

Subsequently, the control unit70compares the level of the abnormal pixel of the signal waveform corresponding to the reference data with the level of the abnormal pixel of the signal waveform corresponding to the initially acquired reference data to determine whether the change in level of the abnormal pixels is large in operation208. For example, the control unit may determine that the change in level of the abnormal pixels is large if the change is greater than a predetermined reference value.

When it is determined that the change in level of the abnormal pixels is large (operation208), the bottom21of the white bar20is determined to be contaminated. When the bottom21is contaminated as described above, the contamination has no influence on the shading correction to the image data of the scanned document. Consequently, the acquired reference data is stored in the memory71in operation203. At this time, the initially acquired reference data is stored in the memory71.

When it is determined that the change in level of the abnormal pixels is not large (operation208), the control unit70determines that the abnormal pixel is generated due to factors other than the white bar20(such as scratches on the surface of the scan glass40or contamination caused by dust on the optical path in the scanning device to which the reflected light is inputted), and corrects the value of the abnormal pixel with the values of the surrounding pixels in operation210. Then, the corrected reference data is stored in the memory71in operation203.

After the reference data is stored in the memory as described above, the white bar20is lowered such that the white bar20is located at a position spaced from the scan glass40by the reference distance D1. Subsequently, the document1, placed on the document loading plate10, is automatically fed and scanned by the scanning device50. Then, shading correction is performed on the image data of the scanned document using the reference data stored in the memory71.

According to aspects of the present invention, the image forming apparatus does not perform shading correction when an abnormal pixel is generated due to contamination of the white bar located on the scan glass, thereby preventing quality degradation of the document image.

Aspects of the present invention can also be embodied as computer-readable codes on a computer-readable recording medium. Also, codes and code segments to accomplish the present invention can be easily construed by programmers skilled in the art to which the present invention pertains. The computer-readable recording medium is any data storage device that can store data which can be thereafter read by a computer system or computer code processing apparatus. Examples of the computer-readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, and optical data storage devices. The computer-readable recording medium can also be distributed over network-coupled computer systems so that the computer-readable code is stored and executed in a distributed fashion. Aspects of the present invention may also be realized as a data signal embodied in a carrier wave and comprising a program readable by a computer and transmittable over the Internet.