JP2006033386A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute the correction of positional shifts due to color aberration of a lens suitable for each of the following reading methods in an image reader provided with both methods for reading an image by scanning an original manuscript laid on the glass of an original manuscript platen, and for reading an image by scanning an original manuscript transferred by an ADF for transferring an original manuscript by a roller or the like. <P>SOLUTION: The optimum correction of positional shifts can be always executed by correcting the positional shifts due to the color aberration of a lens with a correction coefficient suitable for each of the following methods, in a constitution provided with both methods for reading the image by scanning the original manuscript laid on the glass of the original manuscript platen, and for reading the image by scanning the original manuscript transferred by the ADF for transferring the original manuscript by the roller or the like. Positional shift correction processing can be simplified by arranging a positional shift correction circuit to the pre-stage of a mirror image correction circuit and a resolution conversion circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading technology such as a digital copying machine, a scanner, and a facsimile, and more particularly, to read original image data while conveying an original by an original conveying device (hereinafter referred to as ADF (Auto Document Feeder)) at the time of image reading. The present invention relates to an image reading apparatus having two reading methods: a reading method and a fixed reading method for reading a document image of a document placed on a platen glass.

  Conventionally, both a method of reading an image by scanning a document placed on a platen glass in a digital copying machine or the like and a method of scanning a document conveyed by an ADF that conveys the document by a roller or the like are provided. There is a configuration one.

  In a digital copying machine equipped with this type of ADF, when reading a document conveyed by the ADF, the optical stage of the image reading device provided below the ADF is moved to a reading position set in advance by a motor. Are stopped, irradiated with a lamp, and a document is transported between the document table glass and the ADF by a roller at a predetermined speed, and the transported document is scanned. When scanning the document placed on the scanner, there is a configuration in which the document is scanned by moving the optical table of the image reading apparatus by a motor and irradiating a lamp.

  A copy image can be obtained by performing processing in the printer unit based on the scanned data.

  In a configuration having two reading methods of this type, there is a problem in that the image quality varies depending on the reading method. For example, in Patent Document 1, in the reading mode placed on the platen glass, the document is in close contact. However, it has been pointed out that in the mode of reading a document conveyed by the ADF, a difference in reading density occurs due to the document slightly floating. In addition to the fact that the document is floating, it is known that a difference in the reading state of the document occurs due to document glass provided for each reading mode, manufacturing variations of components, and the like.

  Further, in an image reading apparatus that reads a color original, when light having image information from the original is converged on a color linear image sensor through a lens and image data is obtained by a photoelectric conversion element such as a CCD, it is caused by the chromatic aberration of the imaging lens. There is a problem that image deterioration occurs due to color misregistration of a read image, and a technique for correcting and improving this quality deterioration as in Patent Document 3 and Patent Document 4 is known.

JP-A-6-253148 JP 2002-320075 A JP-A-5-122542 Japanese Patent Laid-Open No. 5-137003

  The color shift of the read image due to the chromatic aberration of the imaging lens is the same as the reading state of the original between the two reading methods in the same manner as the difference in reading density between the two reading methods in the configuration having the two reading methods. Are different, the optical path length from the document to the lens changes and a difference occurs. When reading with either reading method, there is a problem that a difference occurs in the output image data between the two reading methods when correction is performed with the same misalignment correction coefficient.

  Even in the case of adopting a configuration as disclosed in Patent Document 2 in which there is almost no difference in chromatic aberration due to this lens, in the mode of reading a document conveyed by ADF, output image data read from the document is placed on the platen glass. Since the original reading position is reversed and becomes a mirror image with respect to the placed reading mode, a mirror image correction circuit for reversing the mirror image and correcting it to a normal image is generally provided. If the correction circuit is located before the correction circuit, it is necessary to invert the coefficient for correcting chromatic aberration in the main scanning direction as in the case of the image, and there is a problem that the processing becomes complicated.

  In addition, when converting the resolution of the read image data, if the chromatic aberration correction is performed after converting the resolution, the resolution of the chromatic aberration is also converted, so it is necessary to reset the coefficient for each converted resolution. There was a problem that processing became complicated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image reading apparatus capable of eliminating a difference in output images between reading methods.

  In order to achieve the above object, the invention described in claim 1 is a fixed reading method for reading a document image of a document placed on a platen glass and a flow reading method for reading a document sheet while being transported by a document feeding device. And an illuminating means for illuminating the original, a photoelectric conversion means for forming an image of reflected light from the original at a predetermined position and outputting a signal of a plurality of colors, and a correction coefficient calculated in advance for each pixel position. And a correction unit that corrects a positional deviation in the main scanning direction of the plurality of color signals based on a coefficient for correcting the positional deviation in the main scanning direction by the fixed reading method and the flow reading method. It is characterized by having each independently.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, the positional deviation amount of the other reading method is matched with the positional deviation amount of one of the reading methods.

  According to a third aspect of the present invention, there is provided a fixed reading method for reading a document image of a document placed on a platen glass and a flow reading method for reading a document sheet while being conveyed by a document feeding device. Illumination means for illuminating, photoelectric conversion means for forming reflected light from the original at a predetermined position and outputting signals of a plurality of colors, and reversing the image in the main scanning direction when the original is read by the flow reading method An image reading apparatus comprising: an image reversing unit that performs correction, and a correction unit that corrects a positional deviation in the main scanning direction of the plurality of color signals based on a correction coefficient calculated in advance for each pixel position. It arrange | positions before a means, It is characterized by the above-mentioned.

  The invention according to claim 4 has illumination means for illuminating the original on the platen glass, and photoelectric conversion means for forming an image of reflected light from the original at a predetermined position and outputting signals of a plurality of colors, A resolution conversion unit that converts the resolution of the image data read by the photoelectric conversion unit; a correction unit that corrects a displacement in the main scanning direction of the plurality of color signals based on a correction coefficient calculated in advance for each pixel position; In the image reading apparatus having the above, the correction unit is arranged in front of the resolution conversion unit.

  According to the present invention, there are two reading methods: a method of reading an image by scanning a document placed on a platen glass and a method of scanning a document conveyed by an ADF that conveys the document by a roller or the like. Even if the reading status of the document differs between the reading methods in the image reading apparatus having the configuration, the output image between the reading methods is used because the parameters for correcting the chromatic aberration by the lens most suitable for each reading method are used. It becomes possible to eliminate the difference.

  Further, even when the apparatus configuration as shown in FIG. 1 is adopted in which the other reading method is in a mirror image state with respect to one reading method when a document is read between the two reading methods, the chromatic aberration correction is performed. Since the correcting means for correcting the main scanning position deviation is arranged before the image inverting means in the main scanning direction, when there is no variation in chromatic aberration between the reading methods, it is not necessary to have a correction coefficient for each reading method. It becomes possible to simplify.

  Further, since the correcting means for correcting the main scanning position deviation for correcting the chromatic aberration is arranged before the resolution converting means, it is necessary to set the main scanning position deviation correction coefficient in accordance with the resolution converted by the resolution converting means. It is possible to eliminate or simplify the processing.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1>
FIG. 1 shows a configuration diagram of a general digital scanner provided with an ADF for reading a document image. The ADF 101 conveys the original 102 by the conveying roller 103, and the original 102 passes between the platen roller 104 and the original platen glass 106 of the image reading apparatus disposed on the housing 105.

  Next, the image reading apparatus disposed in the housing 105 includes a lamp 107 that irradiates light on the document surface, a mirror 108 that reflects light from the lamp 107 reflected by the document, and the lamp 107 and the mirror 108. Optical stage 109 and optical stage 112 for arranging mirrors 110 and 111 for directing the light reflected by the mirror 108 to the lens 116, and the optical stages 109 and 112 are connected to a motor 114 by a wire 113, and position sensors Reference numeral 115 denotes the home position of the optical table 109. The optical table 109 moves the optical tables 109 and 112 to scan the document on the document table glass 106 by rotating the motor 114 forward and backward based on this position. Can do.

  The motor 114 is provided with an encoder 302 (not shown) so that the number of pulses moved by the output of the encoder 302 can be known. Therefore, the positions of the optical benches 109 and 112 can be grasped by the encoder pulses from the encoder 302 provided in the position sensor 115 and the motor 114.

  The details of the CCD 117 include a lens 116 that collects reflected light from the document surface guided by the optical benches 109 and 112, and a CCD 117 that receives light from the document surface collected by the lens 116 and performs photoelectric conversion. Will be described later. The operation unit 118 includes a scan start instruction button from the user, a display for displaying the apparatus status, and the like (see FIG. 2 for details).

  Details of the CCD 117 will be described with reference to FIG.

  As shown in FIG. 3, the CCD 117 is a single IC package, and has a configuration in which 7500 main scanning pixels are arranged so that a photosensitive pixel array corresponding to each of three colors of RGB can read an A4 original at 600 dpi. Yes. Therefore, it is possible to read RGB at a time. The image signal output is output from three output pins, one pin for each line.

  The digital scanner according to the present embodiment uses this configuration to move the optical benches 109 and 112 in the direction of the ADF document reading position, and to read the transported document from the ADF 101, and the document on the platen glass 106. The original image can be read in two modes of the original table glass original reading mode that is placed and scanned by scanning the optical benches 109 and 112 in the sub-scanning direction.

  In the image reading apparatus having such an ADF, when an original is read in the ADF original reading mode, dust adheres to the original reading position of the original platen glass 118 as shown in the enlarged view of the ADF original reading portion in FIG. It is known that if it stays, dust is read and streaks occur in the read image.

  In the present embodiment, the document passes through a position that is lifted about 5 mm from the document table glass 118 so that dust or the like attached to the document is less likely to adhere to the document table glass 118. Therefore, the original is read at a position where the optical path length from the lens is different by 5 mm between the ADF original reading mode and the original table glass original reading mode.

  FIG. 5 is a control configuration diagram according to the present embodiment.

  A transport roller 103 that transports a document placed on the ADF 101, a platen roller 104 that guides the document to the document glass 118, a lamp 107 that irradiates light on the document surface, and optical benches 109 and 112 are moved in the sub-scanning direction to move the document. Motor 114 for scanning, encoder 302 for grasping the amount of movement of the motor 114, position sensor 115, CCD 117 for receiving light from the original surface and performing photoelectric conversion of three lines for each of RGB, RGB three output signals of CCD 117 are 8-bit digital A / D conversion circuits 301R, 301G, and 301B that perform A / D conversion on signals, and an A / D converted output signal from the CCD 117, and the result of reading the reference white plate 120 for the characteristics of the optical system such as the CCD 117 and the lens 116 Shading correction circuits 303R, 30 for correcting shading from G, 303B shading correction signals are received, position shift correction circuits 304R, 304G, 304B for correcting position shifts between RGB due to chromatic aberration of the lens 116, position shift correction image signals are received, and in the ADF document reading mode It has a mirror image processing circuit 305 that inverts the mirrored image data and corrects it to a normal image, and a scanner controller 306 that controls these to perform a document reading operation.

  Next, details of the misregistration correction circuit 304 will be described.

  A detailed block diagram of the misregistration correction circuit 304 is shown in FIG.

  The misregistration correction circuit 304 calculates the expression (A) using the data of three pixels in the filter circuit. For example, when it is desired to shift the position of 0.5 pixels to the left, K0 = 0.5, K1 = 0.5, Substitute K2 = 0. If it is desired to shift the position of 0.5 pixel to the right, K0 = 0, K1 = 0.5, and K2 = 0.5 are substituted.

X ′ = K0 × P (X−1) + K1 × P (X) + K2 × P (X + 1) (A)
X ′: data value after position shift correction P (X): input image data X: pixel position K0 to K2: position shift correction coefficient FIG. 7 shows R based on the G signal at the main scanning position of the CCD 117 of this embodiment. , B shows the amount of misregistration due to chromatic aberration. It is known that the chromatic aberration of the lens gradually increases as the imaging angle of view changes from the main scanning center position to the end as shown in the figure. Therefore, the coefficient setting for the misregistration correction circuit does not require correction coefficients corresponding to all the pixels of the CCD 117. For example, only the three-point representative coefficients of the left end, the center, and the right end are stored, and the other pixels are linear. It can be corrected by the interpolation coefficient. Therefore, the linear interpolation calculation of the coefficient at the current pixel position is performed by the linear interpolation unit in FIG. 6 from the representative coefficients of the left end part, the center part, and the right end part, and the position shift at each main scanning position is set by the filter circuit. to correct.

  The color misregistration that occurs when the RGB misregistration amounts differ due to the chromatic aberration of the lens is corrected by aligning the misregistration of the other two colors with one reference color without correcting all the RGB signals. be able to. The scanner controller 306 sets the three representative coefficients.

  Further, as for the chromatic aberration of this lens, when the optical path length is different between the ADF original reading mode and the original table glass original reading mode as in the present embodiment, the positional deviation amount changes depending on each. When the optical path length is different by 5 mm, the shift amount changes by about 10% (this rate of change varies depending on conditions such as lens design). Therefore, when correcting the positional deviation amount, it is necessary to set an optimal positional deviation coefficient suitable for each reading mode.

  This color misregistration measurement method is such that a black and white line chart with a pitch of about 100 dpi as shown in FIG. 8 is read by each reading method, which is read by the CCD 117 and converted by an A / D conversion circuit. The amount of misalignment shown in FIG. 7 is measured by calculating the amount of misalignment from the captured ideal position from the 8-bit image data.

  An operation for reading the document 102 placed on the ADF 101 and an operation for reading the document placed on the document table glass 106 will be described with reference to the flowchart of FIG.

  When the operation unit 118 is instructed to perform a reading operation in the ADF document reading mode, the scanner controller 306 moves the optical benches 109 and 112 to the reading position of the reference white plate 120 (S902). The lamp 107 is turned on, and white reference data used when the shading correction circuit 305 performs shading correction is fetched (S903).

  Next, the scanner controller 306 moves the optical benches 109 and 112 to the document reading position of the platen roller 104 (S904). Next, the scanner controller 306 transports the document 102 on the ADF 101 by the transport roller 103 (S905), and starts reading the document by the CCD 117 at the document reading position (S906). The scanner controller 306 performs shading correction by the shading correction circuit 305 on the RGB image signal read by the CCD 117 that has been A / D converted by the A / D conversion circuit 301 until the end of reading the document, and uses the ADF document reading mode for the misregistration correction circuit. The positional deviation correction coefficient is set to perform positional deviation correction, and the mirror image processing unit performs processing to correct the mirror image to a normal image (S907, S908). When the document reading is completed, the scanner controller 306 stops the conveying roller 103, turns off the lamp 107, moves the optical benches 109 and 112 to the reference white plate position, and ends the document reading operation (S909).

  Next, the reading operation when the manuscript glass original reading mode is designated by the operation unit 118 will be described.

  The scanner controller 306 moves the optical benches 109 and 112 to the reading position of the reference white plate 120 (S910). Next, the scanner controller 306 turns on the lamp 107 and is used when the shading correction circuit 305 performs shading correction. White reference data to be captured is captured (S911). Next, the scanner controller 306 starts reading the document by the CCD 117 by scanning the document on the document table glass with the optical tables 109 and 112 (S912, S913). The scanner controller 306 performs shading correction on the RGB image signal read by the CCD 117 that has been A / D converted by the A / D conversion circuit 301 until the end of reading of the document by the shading correction circuit 305, and reads the original platen glass document to the misalignment correction circuit. A misregistration correction coefficient for the mode is set and misregistration correction is performed, and a setting is made to pass through the mirror image processing unit and the document is read (S914, S915).

  When the document reading is completed, the scanner controller 306 turns off the lamp 107, moves the optical benches 109 and 112 to the reference white plate position, and ends the document reading operation (S916).

  Even when a positional shift due to chromatic aberration of the lens occurs due to the processing described above, the correction corresponding to each reading mode is performed, so that stable reading is always possible.

<Embodiment 2>
In the second embodiment, an operation when there is a resolution conversion circuit in addition to the configuration of the first embodiment will be described.

  When the resolution conversion circuit is arranged at the position shown in FIG. 10, for example, when the resolution of data read at 600 dpi is converted to 300 dpi, the amount of positional deviation due to chromatic aberration of the lens after conversion is halved in pixel units as shown in FIG. The misregistration correction coefficient setting set in the misregistration correction circuit must also be halved.

  The resolution conversion circuit is provided at the position shown in FIG. 12 so that the resolution conversion is performed after the position shift correction is performed, thereby simplifying a process that does not require complicated processing such as a position shift correction coefficient setting change by resolution conversion. It becomes possible to read the converted image. Since other configurations and processes are the same as those in the first embodiment, description thereof will be omitted.

<Embodiment 3>
The configuration shown in FIG. 13 is adopted so that the original is transported in close contact with the original table glass 118 in the ADF original reading mode so that the optical path length does not differ between the ADF original reading mode and the original table glass original reading mode. In this case, since the optical path length is the same between the two reading modes, chromatic aberration variation due to the lens does not occur between the two reading modes. The control at the time of adopting such a configuration will be described.

  If the variation in chromatic aberration is not between the two reading modes, the misregistration correction circuit is arranged in the preceding stage of the mirror image processing circuit as shown in FIG. 5, so that the misregistration correction coefficient is set in the main scanning direction in the ADF reading mode. It is not necessary to invert, and in either reading mode, it is possible to correct the positional deviation due to the chromatic aberration of the lens with the same positional deviation correction coefficient, and it is possible to perform image reading with simplified processing.

  Since other configurations and processes are the same as those in the first embodiment, description thereof will be omitted.

It is an apparatus block diagram. It is a figure which shows an operation part. It is a CCD block diagram. FIG. 3 is a configuration diagram of an ADF document reading unit. It is a control block diagram. It is a position shift correction circuit configuration diagram. It is a figure which shows position shift amount. It is a chart for position shift measurement. There is a flowchart indicating a document reading operation. It is a control block diagram. It is a figure which shows position shift amount. It is a control block diagram. FIG. 3 is a configuration diagram of an ADF document reading unit.

Explanation of symbols

101 ADF
102 Document 103 Transport roller 104 Platen roller 107 Lamp 117 CCD
306 Scanner controller

Claims (4)

An illuminating means for illuminating a document, the stationary reading method for reading a document image of a document placed on a platen glass, and a flow reading method for reading a document sheet while being transported by a document feeder, and the document And a photoelectric conversion means for imaging a reflected light from a predetermined position to output a signal of a plurality of colors, and correcting a positional deviation in the main scanning direction of the plurality of color signals based on a correction coefficient calculated in advance for each pixel position. In an image reading apparatus comprising a correction means,
An image reading apparatus characterized in that a coefficient for correcting a positional deviation in the main scanning direction is independently provided by the fixed reading method and the flow reading method.   The image reading apparatus according to claim 1, wherein the positional deviation amount of one reading method is matched with the positional deviation amount of the other reading method. An illuminating means for illuminating a document, the stationary reading method for reading a document image of a document placed on a platen glass, and a flow reading method for reading a document sheet while being transported by a document feeder, and the document A photoelectric conversion unit that forms an image of reflected light from a predetermined position and outputs a signal of a plurality of colors; an image inversion unit that inverts an image in a main scanning direction when reading a document by the flow reading method; and a pixel position In an image reading apparatus comprising correction means for correcting a positional deviation in the main scanning direction of the plurality of color signals based on a correction coefficient calculated in advance every time,
An image reading apparatus, wherein the correction unit is arranged in a stage preceding the image inversion unit. Illumination means for illuminating the original on the platen glass, and photoelectric conversion means for forming an image of reflected light from the original at a predetermined position and outputting signals of a plurality of colors, read by the photoelectric conversion means An image reading apparatus comprising: a resolution conversion unit that converts the resolution of image data; and a correction unit that corrects a positional deviation in the main scanning direction of the plurality of color signals based on a correction coefficient calculated in advance for each pixel position.
An image reading apparatus, wherein the correction unit is arranged in a stage preceding the resolution conversion unit.

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