JP2005333590A - Image reading apparatus, image reading method, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of alleviating variation in image resolution between 3 colors of RGB when a color image on a manuscript is read, even if the value of (reading scale factor) × (sensor line spacing) is below in decimal point. <P>SOLUTION: The image reading apparatus comprises an one-dimensional image sensor 58, an optical drive portion 59, and a control unit 35. The sensor 58 includes a reading sensor for light detection of R color, G color, and B color composed of a plurality of light receiving element sequences and arranged with a predetermined spacing at a sub scanning direction perpendicular to a main scanning direction. Moreover, the sensor 58 reads optical information on each color simultaneously at different positions of the sub scanning direction for a manuscript 30, at which light is irradiated with an optical source. The optical drive portion 59 moves the sensor 58 or the manuscript 30 relatively for the sub scanning direction. The control unit 35 corrects position shift of a reading sensor for each color light detection in the sub scanning direction, for the optical information read and obtained by the sensor 58 from the moved manuscript 30. In addition, the control unit 35 adjusts a rate of linear extrapolation between read lines before and behind to correct image resolution between each color components. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, an image reading method, and an image forming apparatus for correcting a sub-scan timing shift of image data from a three-line color CCD sensor generated according to a magnification ratio in a color scanner and a color copying machine equipped with the same. Is.

  In recent years, tandem type color printers, color copiers, color facsimile machines, multifunction machines of these, and the like have been increasingly used. In these color image forming apparatuses, yellow (Y), magenta (M), cyan (C), and black (BK) exposure means, developing means, photosensitive drums, and intermediate transfer belts or conveying material transfer belts are used. And a fixing device.

  For example, the Y-color exposure means draws an electrostatic latent image on the photosensitive drum based on arbitrary image information. In the developing device, a color toner image is formed by attaching a Y-color toner to the electrostatic latent image drawn on the photosensitive drum. The photosensitive drum transfers the toner image to the intermediate transfer belt. Similar processing is performed for the other M, C, and BK colors. The color toner image transferred to the intermediate transfer belt is transferred to a sheet and then fixed by a fixing device.

  By the way, according to this type of color image forming apparatus, a color scanner function using a one-dimensional image sensor such as a three-line color CCD sensor is provided. In this image sensor, a line-shaped reading sensor for detecting red (R), green (G) and blue (B) light is configured by arranging a plurality of light receiving element arrays in the main scanning direction. The pixels are divided at different positions in the sub-scanning direction of the document (sheet) that is arranged at a predetermined distance in the sub-scanning direction orthogonal to the light source and irradiated with light from the light source, and the light information of each color is simultaneously obtained. Read.

  According to such an image sensor, the input timing for a plurality of lines is shifted due to the structural reason in the sub-scanning direction of the RGB color reading sensors, that is, the arrangement intervals of the RGB color reading sensors. The shift in the input timing leads to a decrease in the modulation transfer function (also referred to as image resolution; Modulation Transfer Function; hereinafter referred to as MTF) of the scanner and a deterioration in image resolution between the respective colors. This shift in input timing in the sub-scanning direction is corrected by introducing a timing correction function.

  Further, when reading a document, the scaling factor becomes involved in the shift of the input timing. When the variable magnification is set as an integer such as 100% or 50%, it can be dealt with by providing means for correcting the integer line. For example, a FIFO memory for a plurality of lines is prepared for each color, and the input timing is adjusted by delaying the FIFO memory.

  However, the scaling factor may need to be set to a decimal point. For example, when an A3 size original is reduced to A4 size and an image is read, 70.7% is set as the scaling factor. In addition, an arbitrary magnification is designated steplessly as a zoom function. For example, 87.5% or 62.5% is set. In such a case, it is necessary to correct the decimal point line in addition to the integer line. The generation of the decimal point line is because the sub-scanning speed is changed according to the variable magnification, and a timing shift of less than one line occurs.

  Regarding this type of timing deviation correction function of less than one line, Patent Document 1 discloses an image reading apparatus, an image processing system, an image reading method, a medium for providing a control program, and a control program. According to this image reading apparatus, on the premise that a three-line color CCD image sensor is used, an inter-line correction unit and an MTF correction unit are provided, and the inter-line correction is performed by the inter-line correction unit so as to align the RGB colors. The The interline correction unit includes a delay circuit that adjusts the delay for integer lines and a linear interpolation circuit that corrects the delay for decimal lines. The delay for the decimal line is linearly interpolated using image data of two lines before and after. The MTF correction unit corrects the MTF difference between the RGB colors generated in the inter-line correction unit to make the resolution uniform. Black character determination processing is performed based on the RGB color image in which the MTF difference is corrected. As described above, when the image reading apparatus is configured to include the interline correction unit and the MTF correction unit, the black character determination accuracy is improved.

FIG. 13 is a diagram showing a correction example of the image read data Dr, Dg, Db by the image sensor 58 according to the conventional example.
An image sensor 58 shown in FIG. 13 is a module that constitutes a three-line color CCD image sensor and has a function capable of closely reading a document image at an equal magnification. In FIG. 13, each rectangle represents a read pixel. The three reading sensors Lr, Lg, and Lb for detecting R, G, and B color light are arranged in a line in the main scanning direction on the same semiconductor substrate, and predetermined in the sub-scanning direction orthogonal to the main scanning direction. Are arranged at a distance of.

  The document image is detected simultaneously by three reading sensors Lr, Lg, and Lb divided in the sub-scanning direction. The reading sensor Lr constitutes a line-shaped sensor that reads R-color light, and has a light-receiving element array for detecting R-color light arranged in the main scanning direction. The reading sensor Lg constitutes a line-shaped sensor that reads G color light, and has a light receiving element array for G color light detection arranged in the main scanning direction. The reading sensor Lb constitutes a line-shaped sensor that reads B-color light, and has a light-receiving element array for detecting B-color light arranged in the main scanning direction.

  Further, in the line-shaped reading sensors Lr, Lg, and Lb for detecting RGB color light, the distance between the sensors is, for example, 4 lines apart from the resolution of 600 dpi in the sub-scanning direction. That is, when the zoom ratio is 100%, the distance between the read sensor Lr for detecting the R color light and the read sensor Lg for detecting the G color light is 4 lines apart, and the read sensor for detecting the R color light. The distance between the sensor between Lr and the reading sensor Lb for detecting the B color light is in a state where there is an interval of 8 lines. As a result, the image sensor 58 divides pixels at different positions in the sub-scanning direction of the original 30 irradiated with light from the light source, and reads light information of R color, G color, and B color simultaneously.

In the line-to-line correction unit as found in Patent Document 1, when the magnification ratio is 100%, in FIG. 13, corresponding to the arrangement interval of the reading sensors Lr and Lg between the R color and the G color with reference to the R color. The 4 line FIFO memory absorbs the timing deviation for 4 lines, and the 8 line FIFO memory absorbs the timing deviation for 8 lines corresponding to the arrangement sensor interval of the reading sensors Lr and Lb between the R and B colors. In this example, pixel values R _n , G _n , B _n (n = 1, 2, 3,...) Each indicate a data group for one line main scanning. In the example shown in FIG. 13, the pixel values R ₁ , R ₂ ... For the R color constitute the R color component image read data Dr. The pixel values G ₁ , G ₂ ... For the G color constitute the G color component image read data Dg. The pixel values B ₁ , B ₂ ... For the B color constitute the B color component image read data Db.

  As described above, in the reading process at the same magnification (variable magnification = 100%), when RGB 3 channel image reading signals are obtained at intervals of 4 lines, R color = no delay, G color 4 line delay, B color = The timing is adjusted via the FIFO, such as an 8-line delay. When the zoom ratio is 75%, the delay amount between lines is 3 lines, and the delay amount of the FIFO is adjusted such that R color = no delay, G color = 3 line delay, B color = 6 line delay, and so on. It is made like.

FIGS. 14 and 15 are diagrams showing linear interpolation examples (parts 1 and 2) of the image read data Dr, Dg, and Db when the scaling point is set.
According to the linear interpolation example of the image read data Dr, Dg, and Db shown in FIG. 14, when the scaling factor is set to the decimal point, for example, the interline delay is set to 3.5 lines. This corresponds to a case where the width of 4 lines between the reading sensors Lr, Lg, and Lb adjacent to each other is read in a sub-scanning time of 4 lines × 87.5% = 3.5 lines. Here, with respect to the deviation amount of the 3.5 line interval, the 0.5 line portion is set to 0.5 to 0.5 between the two consecutive lines before and after the linear interpolation process, that is, the average between the two pixels. It is dealt with by finding the value.

  Here, when G color is used as a reference, R color = 0 line + 0.5 line, G color = 4 line, B color = 7 line + 0.5 line delay. Regarding integer lines, G color = 4 lines are absorbed by the 4 line FIFO memory, and B color = 7 lines are absorbed by the 7 line FIFO memory.

  For the 0.5 decimal point line, as seen in the inter-line correction unit of Patent Document 1, interpolation processing is performed by connecting a linear interpolation circuit after the delay circuit. According to this linear interpolation circuit, when the G color is used as a reference with respect to the delay of 0.5 lines, the pixel values of the R color and the B color are averaged, that is, (previous line data + next line data). ) / 2 (0.5: 0.5). The output value obtained by this interpolation processing is used as image read data corresponding to a 0.5 line shift timing.

According to this type of linear interpolation processing, in FIG. 15, the pixel values of the first line with respect to R color _{R 1 = [R 1.1, R} 1.2, R 1.3 ··· R 1.n] ( where n is the main The number of scanning pixels) and the new pixel value R _1.5 = (R ₁ + R ₂ ) / interpolated from the pixel value R ₂ = [R _2.1 , R _2.2 , R _2.3 ... R _2.n ] of the second line. 2 = [(R _1.1 + R _2.1 ) / 2, (R _1.2 + R _2.2 ) / 2, (R _1.3 + R _2.3 ) / 2... (R _1.n + R _2.n ) / 2] is output. Similarly new pixel value R _2.5 where the pixel value of the second line R ₂ and the interpolation from the pixel value R ₃ of the third line is output.

Further, a new pixel value B _1.5 obtained by performing interpolation processing on the B color from the pixel value B ₁ of the first line and the pixel value B ₂ of the second line is output. Similarly new pixel value B _2.5 in which the pixel values of the second line B ₂ and the interpolation from the pixel value B ₃ of the third line is output. For the G color, the pixel value G ₁ of the first line, the pixel value G ₂ of the second line, etc. are output as they are without performing linear interpolation processing. As a result of this interpolation processing, the pixel values R _1.5 , R _2.5 ... For the R color constitute the R color component image read data Dr. The pixel values G ₁ , G ₂ ... For the G color constitute the G color component image read data Dg. The pixel values B _1.5 , B _2.5 ... For the B color constitute the B color component image read data Db. Thus, the delay of the decimal point line, that is, 0.5 line is dealt with.

  Patent Document 2 discloses a scanner and a color image forming apparatus. According to this scanner, on the premise that the reading timing in the sub-scanning direction is shifted by a plurality of lines due to the structure of the 3-line color CCD sensor, the color / monochrome switching switch is provided and the sub-scanning speed in the monochrome image reading operation is provided. The switch is operated so as to switch to N times the sub-scanning speed in the color image reading operation. By configuring the scanner in this way, the time required for the monochrome image reading operation can be shortened.

Japanese Unexamined Patent Publication No. 2003-174568 (page 6, FIG. 4) Japanese Unexamined Patent Publication No. 2003-101725 (page 8, FIG. 4)

  However, the conventional image reading apparatus and the color image forming apparatus to which the image reading apparatus is applied have the following problems.

  i. An image reading apparatus having an image sensor such as a 3-line CCD sensor including Patent Documents 1 and 2 is provided with an interline correction unit, and when a scaling factor is set by a decimal point, an integer line is set by a delay circuit. The decimal point line is corrected by a linear interpolation circuit. For example, when a variable magnification (hereinafter also referred to as a document reading magnification) is set with a decimal point, interpolation calculation processing is performed for the other R and B colors with reference to the G color.

  Accordingly, the black horizontal thin line after image formation does not have the same RGB color level, and the RB color line is blurred in the sub-scanning direction, resulting in color blurring. As described above, since the MTFs of RGB colors vary, there is a possibility that the color image forming apparatus to which the image reading apparatus is applied may lead to a decrease in image forming quality.

  ii. According to Patent Document 1, an MTF correction unit is provided after the interline correction unit, and the MTF deteriorated by the interline correction unit is corrected later by a spatial filter for MTF correction or the like. Therefore, it is necessary to provide an MTF correction unit for aligning the resolution separately from the interline correction unit, which may increase the cost.

  Therefore, the present invention solves the above-described problem, and when reading a color image on a document (sheet), it is possible to make the image resolutions of red, green and blue uniform, and (reading magnification) Even if the magnification ratio is set so that the x (sensor line interval) has a value below the decimal point, the image reading apparatus and image that can reduce variations in image resolution among the three colors of red, green, and blue An object is to provide a reading method and an image forming apparatus.

  In order to solve the above-described problems, an image reading apparatus according to the present invention is an apparatus for reading a color image formed on an arbitrary sheet, and includes a light source for irradiating the sheet with light and a plurality of light receiving element arrays. Line-shaped reading sensors for detecting red, green and blue light arranged in the direction are arranged at a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction, and light is emitted from the light source. A one-dimensional image sensor that divides pixels at different positions in the sub-scanning direction of the sheet and reads light information of each color at the same time, and a moving means that relatively moves the image sensor or the sheet in the sub-scanning direction, With respect to the light information obtained by reading with the image sensor from the sheet moved by this moving means, the positional deviation in the sub-scanning direction between the line-shaped reading sensors for detecting each color light is corrected. And correction means for correcting the image resolution between the respective color components by adjusting the ratio of linear interpolation between the preceding and following reading lines with respect to the optical information subjected to the positional deviation correction. is there.

  According to the image reading apparatus of the present invention, when reading a color image formed on an arbitrary sheet, a plurality of light receiving element arrays are arranged in the main scanning direction, and are used for red, green, and blue light detection. A one-dimensional image sensor is used in which line-shaped reading sensors are arranged at a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction. Light is applied to the sheet from the light source. The moving means moves the image sensor or the sheet relatively in the sub-scanning direction.

  The image sensor reads light information of each color simultaneously at different positions in the sub-scanning direction of the sheet irradiated with light from the light source. On the premise of this, the correction means corrects the positional deviation in the sub-scanning direction of each color light detection line-shaped reading sensor with respect to the optical information obtained by reading by the image sensor from the sheet moved by the moving means. . Further, the correcting means adjusts the image resolution between the respective color components by adjusting the ratio of linear interpolation between the preceding and following reading lines with respect to the optical information subjected to the positional deviation correction.

  Therefore, it is possible to control in a direction that reduces the relative difference between the red, green, and blue image resolutions, in other words, in a direction that aligns the resolutions, and it is possible to prevent color bleeding. Moreover, since the ratio of linear interpolation between the preceding and following reading lines can be adjusted according to the original reading magnification, even if (reading magnification) x (sensor line interval) has a value below the decimal point, the black horizontal thin line For read signals such as red, green and blue, the read signals can be brought close to the same level.

  An image reading method according to the present invention is a method of reading a color image formed on an arbitrary sheet, and is used for detecting red, green and blue light configured by arranging a plurality of light receiving element arrays in the main scanning direction. A linear reading sensor is arranged at a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction, and the pixels are divided at different positions in the sub-scanning direction to simultaneously read light information of each color. Using the original image sensor, the sheet or the image sensor is moved relatively in the sub-scanning direction, and the light information irradiated from the sheet and returned from the sheet is read. Corrects the positional deviation in the sub-scanning direction between the line-shaped reading sensors for color light detection, and adjusts the linear interpolation ratio between the preceding and following reading lines to resolve the image between each color component. It is characterized in that corrected.

  According to the image reading method of the present invention, when a color image formed on an arbitrary sheet is read, the direction in which the relative difference between the red, green and blue image resolutions is reduced, that is, the resolutions are aligned. The direction can be controlled, and color bleeding can be prevented. Moreover, since the ratio of linear interpolation between the preceding and following reading lines can be adjusted according to the original reading magnification, even if (reading magnification) x (sensor line interval) has a value below the decimal point, the black horizontal thin line For read signals such as red, green and blue, the read signals can be brought close to the same level.

  An image forming apparatus according to the present invention is an apparatus that reads a color image formed on an arbitrary sheet to form a color image. The image reading apparatus reads a color image formed on a sheet, and the image reading apparatus An image forming unit configured to form a color image based on color image information obtained by reading, and the image reading device includes a light source that irradiates light to the sheet and a plurality of light receiving element arrays arranged in the main scanning direction. The red, green, and blue light detection line-shaped reading sensors are arranged at a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction, and the light is irradiated by the light source in the sub-scanning direction. A one-dimensional image sensor that divides pixels at different positions and simultaneously reads light information of each color, a moving means that relatively moves the image sensor or sheet in the sub-scanning direction, and the movement Regarding the optical information read by the image sensor from the sheet moved by the stage, the positional deviation in the sub-scanning direction between each color light detection line-shaped reading sensor is corrected, and the optical information subjected to the positional deviation correction is corrected. And a correction means for correcting the image resolution between the respective color components by adjusting the rate of linear interpolation between the preceding and following reading lines.

  According to the image forming apparatus according to the present invention, the image reading apparatus according to the present invention is applied when a color image formed on an arbitrary sheet is read to form a color image. That is, the image reading device reads a color image formed on the sheet. The image forming means forms a color image based on the color image information obtained by reading with the image reading apparatus.

  Therefore, variation in image resolution among the three colors of red, green, and blue can be reduced. Thereby, even when (reading magnification) × (sensor line interval) has a value below the decimal point, it is possible to form a high-quality image that is not colored by a black horizontal thin line or the like.

  According to the image reading apparatus and the image reading method of the present invention, when reading a color image formed on an arbitrary sheet, red, green, and blue light detection lines are obtained with respect to optical information obtained by reading with an image sensor. Correction means for correcting the positional deviation in the sub-scanning direction between the reading sensors in the shape of the image, and further, this correction means adjusts the ratio of linear interpolation between the preceding and following reading lines for the optical information whose positional deviation is corrected. Thus, the image resolution between the respective color components is corrected.

  With this configuration, it is possible to control the direction in which the relative difference between the red, green, and blue image resolutions is reduced, that is, the direction in which the resolutions are aligned, and color bleeding can be prevented. Moreover, since the ratio of linear interpolation between the preceding and following reading lines can be adjusted according to the original reading magnification, even if (reading magnification) x (sensor line interval) has a value below the decimal point, the black horizontal thin line For read signals such as red, green and blue, the read signals can be brought close to the same level. Thereby, variation in image resolution (MTF) between the three colors of red, green, and blue can be reduced. Therefore, the apparatus can be sufficiently applied to an image forming apparatus with a color scanner.

  According to the image forming apparatus according to the present invention, the image reading apparatus according to the present invention is applied when a color image formed on an arbitrary sheet is read to form a color image.

  With this configuration, it is possible to reduce variations in image resolution among the three colors of red, green, and blue. Therefore, even when (reading magnification) × (sensor line interval) has a value below the decimal point, it is possible to form a high-quality image that is not colored by a black horizontal thin line or the like.

  Hereinafter, an image reading apparatus, an image reading method, and an image forming apparatus according to embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram showing a configuration example of a color scanner 100 as a first embodiment of the present invention.
In this embodiment, when reading a color image formed on an arbitrary sheet, optical information obtained by reading with an image sensor is detected in the sub-scanning direction between line-like reading sensors for detecting red, green and blue light. Compensation means for correcting misregistration is provided, and the optical information corrected for misregistration is adjusted by adjusting the linear interpolation ratio between the preceding and succeeding reading lines to correct the image resolution between the respective color components, and red, green In addition, the image resolution between the three colors of red, green, and blue (MTF) can be achieved even when (scanning magnification) × (sensor line interval) has a value below the decimal point. This is to reduce the variation of

  A color scanner 100 shown in FIG. 1 is an example of an image reading apparatus, and is an apparatus that reads a color image formed on an arbitrary sheet. In addition to the color scanner 100, the image reading apparatus is suitable for application to a tandem color printer, a color copying machine, a color facsimile apparatus, a complex machine of these, and the like. The color scanner 100 includes a scanner unit 11 and a scanner main body 11a, and constitutes a slit scan scanner. For example, an automatic document feeder (ADF) 40 is attached to the scanner body 11a and operates to automatically feed an arbitrary sheet (hereinafter referred to as a document 30) in the ADF mode. Here, the ADF mode refers to an operation of automatically feeding a document 30 placed on the ADF 40 and automatically reading a document image.

  The ADF 40 includes a document placing portion 41, a roller 42 a, a roller 42 b, a roller 43, a transport roller 44, and a paper discharge tray 46. One or a plurality of originals 30 are placed on the original placing portion 41. A roller 42 a and a roller 42 b are provided on the downstream side of the document placing portion 41. When the automatic paper feeding mode is selected, the document 30 fed out from the document placing portion 41 is U-shaped by the downstream roller 43. It is conveyed so as to rotate. When the ADF mode is selected, the recording surface of the original 30 is placed upward by the original placement portion 41.

  The scanner unit 11 reads the document 30 and acquires image reading information. The scanner unit 11 is provided with a one-dimensional image sensor 58. For example, when the document 30 is reversed in a U shape by the roller 43 in the ADF mode, the surface of the document 30 is read and an image reading signal Sout is output. To be made. A three-line color CCD image pickup device is used for the image sensor 58.

  The image sensor 58 includes three reading sensors for detecting red (R), green (G), and blue (B) light that are configured by arranging a plurality of light receiving element arrays in the main scanning direction. Pixels are divided at different positions in the sub-scanning direction of the document 30 that are arranged at a predetermined distance in the orthogonal sub-scanning direction and irradiated with light, and light information of R, G, and B colors is simultaneously obtained. It is made to read.

  The document 30 read by the scanner unit 11 is conveyed by the conveyance roller 44 and discharged to the discharge tray 46. The image sensor 58 outputs an RGB color-based image reading signal Sout obtained by reading the document 30 in the platen mode. Here, the platen mode refers to an operation of automatically reading an original image by scanning an optical drive system on the original 30 placed on the platen glass.

  In addition to the image sensor 58, the scanner unit 11 includes a first platen glass 51, a second platen glass (ADF glass) 52, a light source 53, mirrors 54, 55, and 56, an imaging optical unit 57, and an optical drive unit 59. Have. The light source 53 operates to irradiate the document 30 with light.

  The optical driving unit 59 constitutes an example of a moving unit and includes a motor 59 '. The motor 59 ′ is attached to the optical drive unit 59. The optical drive unit 59 operates to move the document 30 or the image sensor 58 relatively in the sub-scanning direction under the rotational force of the motor 59 '. In this example, the optical drive unit 59 moves the optical system such as the light source 53 and the mirrors 54, 55, and 56 in the sub-scanning direction in the platen mode. The sub-scanning direction is a direction orthogonal to the main scanning direction when the arrangement direction of the plurality of light receiving elements constituting the image sensor 58 is the main scanning direction. In this example, the motor 59 'is controlled so as to vary the reading speed in the sub-scanning direction in accordance with the document reading magnification (hereinafter referred to as variable magnification Z).

  On the other hand, a control unit 35 is provided in the scanner body. In this example, the control unit 35 is connected to the output stage of the above-described image sensor 58 and performs analog signal processing, correction processing, and memory access on the RGB color image reading signal Sout acquired by the scanner unit 11. Execute control etc.

  In this example, the correction unit 34 is provided in the control unit 35. The correction means 34 is a line for detecting R, G, and B light with respect to the optical information obtained by reading the original 30 from the original 30 through the optical system by the image sensor 58 in the platen mode. In addition to correcting the positional deviation in the sub-scanning direction of the reading sensor in the shape of the image, between the R, G, and B color components by adjusting the ratio of linear interpolation between the preceding and following reading lines with respect to the optical information subjected to the positional deviation correction The image resolution is corrected.

  In addition to the control unit 35, an operation panel 48 is provided in the scanner body. The operation panel 48 is an example of a setting unit, and is operated to set the zoom ratio Z when reading the document 30. The operation panel 48 is operated so as to output image read data Dout obtained by reading an arbitrary document 30 to a printer or the like. The operation unit 14 is operated to select the ADF mode or the platen mode. An output terminal 9 such as a USB standard is connected to the control unit 35. The output terminal 9 is connected to a printer or the like through a USB standard communication cable, and transmits image read data Dout.

  FIG. 2 is a conceptual diagram showing a configuration example of the image sensor 58 for three line colors. An image sensor 58 shown in FIG. 2 is a module that constitutes a CCD linear image sensor and has a function capable of closely reading a document image at an equal magnification. In FIG. 2, each rectangle represents a read pixel. When the image sensor 58 constitutes a 600 linear CCD linear image sensor module for 1 × magnification, assuming that the size of one pixel is a × b, a = 42 μm and b = 42 μm. The three reading sensors Lr, Lg, and Lb for detecting R, G, and B light are, for example, a light receiving element group (photo sensor array) of about 42 μm × 42 μm square in the main scanning direction on the same semiconductor substrate. Thousands are arranged in a line, and are arranged at a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction. In this example, if the arrangement pitch of the light receiving elements in the sub-scanning direction is w (= 4 × b), w is about 168 μm.

  The document image is simultaneously detected by three line-shaped reading sensors Lr, Lg, and Lb divided in the sub-scanning direction. The reading sensor Lr constitutes a line-shaped sensor that reads R-color light, and has a light-receiving element array for detecting R-color light arranged in the main scanning direction. The reading sensor Lg constitutes a line-shaped sensor that reads G color light, and has a light receiving element array for G color light detection arranged in the main scanning direction. The reading sensor Lb constitutes a line-shaped sensor that reads B-color light, and has a light-receiving element array for detecting B-color light arranged in the main scanning direction.

  Further, in the line-shaped reading sensors Lr, Lg, and Lb for detecting RGB color light, the distance between the sensors is 4 lines apart from the resolution of 600 dpi in the sub-scanning direction. That is, when the zoom ratio is 100%, the distance between the read sensor Lr for detecting the R color light and the read sensor Lg for detecting the G color light is 4 lines apart, and the read sensor for detecting the R color light. The distance between the sensor between Lr and the reading sensor Lb for detecting the B color light is in a state where there is an interval of 8 lines.

  Thereby, the image sensor 58 can divide the pixels and read the light information of the R color, the G color, and the B color at the same time at different positions in the sub-scanning direction of the document 30 irradiated with light from the light source 53. The image sensor 58 is not limited to a three-line color image sensor, and may be a contact image sensor, a three-line color CCD image pickup device including a reduction optical system, or the like.

  FIG. 3 is a block diagram illustrating a configuration example of a control system of the color scanner 100. The color scanner 100 shown in FIG. 3 has a control unit 35, and an image sensor 58 and an operation panel 48 are connected to the control unit 35. The control unit 35 includes the analog signal processing units 31R, 31G, and 31B for RGB colors, the correction processing units 32R, 32G, and 32B, the memory access control units 33R, 33G, and 33B, and the image memory 36. An optical system drive control unit 37 and an MPU (microprocessor) 15 are included.

  The analog signal processing unit 31R for the R color channel (Rch) has an analog / digital (A / D) converter (not shown). The analog signal processing unit 31R receives the R color component image reading signal Sout (= Sr) from the image sensor 58, performs A / D conversion, and outputs, for example, 10-bit image reading data Dr per pixel. Made.

  Similarly, the analog signal processing unit 31G of the G color channel (Gch) receives the G color component image read signal Sout (= Sg) from the image sensor 58, performs A / D conversion, and performs 10 bit per pixel. The image reading data Dg is output. The analog signal processing unit 31B of the B color channel (Bch) receives the B color component image reading signal Sout (= Sb) from the image sensor 58, performs A / D conversion, and reads 10-bit image reading data Db per pixel. Is output.

  The correction processing unit 32R performs a shading correction process, a timing correction process, a γ correction process, a scaling process, a spatial filter process, and the like. For example, the 10-bit R color channel image read data Dr per pixel from the analog signal processing unit 31R is subjected to a shading correction process, and then replaced with 8-bit image read data Dr through a γ conversion process.

  The correction processing unit 32G also performs a shading correction process, a timing correction process, a γ correction process, a scaling process, a spatial filter process, and the like. For example, 10-bit G color channel image read data Dg per pixel is subjected to a shading correction process from the analog signal processing unit 31G, and then replaced with 8-bit image read data Dg through a γ conversion process.

  The correction processing unit 32B is also configured to perform shading correction processing, timing correction processing, γ correction processing, scaling processing, spatial filter processing, and the like. For example, the 10-bit B color channel image read data Db per pixel is subjected to shading correction processing from the analog signal processing unit 31B, and then γ conversion processing is performed to replace it with 8-bit image read data Db.

  The correction processing units 32R, 32G, and 32B for each of the RGB color channels are provided with timing correction units 34R, 34G, and 34B that constitute an example of the correction unit 34. The correction processing unit 32R is provided with a timing correction unit 34R for detecting R color light with respect to the image reading data Dr obtained by reading from the document 30 moved by the optical drive unit 59 or the image sensor 58 through the optical system through the optical system. In addition to correcting the positional deviation in the sub-scanning direction between the reading sensor Lr and other color light detection sensors Lg, etc., linear interpolation between the preceding and subsequent reading lines with respect to the image reading data Dr corrected in positional deviation is performed. Is adjusted to correct the image resolution among the R, G, and B color components.

  The correction processing unit 32G is provided with a timing correction unit 34G. Similarly, with respect to the image reading data Dg, sub-scanning between the reading sensor Lg for detecting G color light, the reading sensor Lb for detecting other color light, and the like. In addition to correcting the misregistration in the direction, the image resolution between the R, G, and B color components is corrected by adjusting the linear interpolation ratio between the preceding and following reading lines for the image reading data Dg that has been corrected for misalignment. To be made.

  Further, the correction processing unit 32B is provided with a timing correction unit 34B. Similarly, with respect to the image read data Db, the sub-between the read sensor Lb for detecting B color light and the read sensor Lr for detecting other color light. In addition to correcting the positional deviation in the scanning direction, the image resolution between the R, G, and B color components is adjusted by adjusting the linear interpolation ratio between the preceding and following reading lines for the image reading data Db that has been corrected for the positional deviation. It is made to correct.

  An example of the internal configuration of the timing correction units 34R, 34G, and 34B for each RGB color channel will be described with reference to FIG. Further, an image processing unit (not shown) such as a γ correction unit, a scaling processing unit, and a spatial filter processing unit (not shown) is connected to the subsequent stage of each of the RGB color channel timing correction units 34R, 34G, and 34B. , Γ correction and the like are executed.

  The Rch memory access control unit 33R is connected to the correction processing unit 32R. The memory access control unit 33R writes and reads the image reading data Dr (MEM control). For example, the memory access control unit 33R encodes and compresses the image read data Dr, temporarily stores the compressed image read data Dr in the image memory 36, or decodes and decompresses the image read data Dr, and after decompression The compression / decompression control for outputting the image read data Dr to the printer or the like is executed.

  Further, the Gch memory access control unit 33G is connected to the correction processing unit 32G. The memory access control unit 33G performs MEM control on the image reading data Dg. For example, the memory access control unit 33G encodes and compresses the image reading data Dg, temporarily stores the compressed image reading data Dg in the image memory 36, or decodes and decompresses the image reading data Dg, and after decompressing The compression / decompression control for outputting the image read data Dg to a printer or the like is executed.

  Furthermore, a Bch memory access control unit 33B is connected to the correction processing unit 32B. The memory access control unit 33B performs MEM control on the image reading data Db. For example, the memory access control unit 33B encodes and compresses the image read data Db, temporarily stores the compressed image read data Db in the image memory 36, or decodes and decompresses the image read data Db, and after decompression The compression / decompression control for outputting the image read data Db to the printer or the like is executed. For the image memory 36, a DRAM or a hard disk is used.

  A system bus 29 is connected to the correction processing units 32R, 32G, and 32B and the memory access control units 33R, 33G, and 33B. An MPU (Micro Processor Unit) 15, an image memory 36, an optical system drive control unit 37, and an operation panel 48 are connected to the system bus 29. The system bus 29 includes a data bus for transferring data and a control bus for transmitting various control signals.

  In this example, the optical system drive controller 37 is connected to a motor 59 ′ of the optical drive system 59. The optical system drive control unit 37 is controlled by the MPU 15 to control the motor 59 '. For example, the optical system drive control unit 37 outputs a motor control signal S1 corresponding to the variable magnification Z to the motor 59 'so as to vary the reading speed in the sub-scanning direction. The motor 59 'rotates at a rotational speed based on the motor control signal S1 (motor control).

  The MPU 15 controls input / output of the correction processing units 32R, 32G, and 32B based on the scaling factor Z set by the operation panel 48. The operation panel 48 includes the operation unit 14 and the display unit 18. The operation unit 14 is operated so as to select the ADF mode or the platen mode in addition to being operated to set the zoom ratio Z when reading the document 30. The display unit 18 displays, for example, a percentage with respect to the scaling factor Z. In addition to integer settings such as 100%, 90%, and 80%, decimal points such as 87.5% and 72.8% can be set.

  For example, the MPU 15 outputs the interpolation coefficients k and 1-k corresponding to the scaling factor Z set by the operation unit 14 to the timing correction units 34R, 34G, and 34B. In this example, the MPU 15 sets an offset amount corresponding to the delay amount between the read sensors Lr, Lg, and Lb, and adds the offset amount set here to the delay amount between the read sensors Lr, Lg, and Lb. Then, the timing correction units 34R, 34G, and 34B are controlled so as to calculate the delay correction amount. Further, the MPU 15 sets the offset amount and the delay correction amount according to the sub-scanning speed corresponding to the variable magnification Z.

  The MPU 15 is not limited to these, and the MPU 15 sets the delay correction amount so that the absolute value of the difference in the interpolation coefficient k between the R color, the G color, and the B color is minimized by setting the scaling factor Z on the operation panel 48. Set. Also, the MPU 15 controls the timing correction units 34R, 34G, and 34B so that the delay correction amounts of the two colors of R, G, and B are equal to each other, or the delay correction amounts are in a complement relationship. To do.

FIG. 4 is a block diagram showing an internal configuration example of the timing correction unit 34G for the G color channel. The same configuration is adopted for the timing correction unit 34B for the B color channel.
In this embodiment, with respect to each of the RGB color three-channel image read signals Sin obtained from the image sensor 58, the delay between lines is corrected for each after A / D conversion. In this example, when the zoom ratio Z = 100%, the output of the read sensor Lg for detecting G color light arrives at a delay of 4 lines with respect to the output of the read sensor Lb for detecting B color light, and is used for detecting R color light. The output of the reading sensor Lr reaches 8 lines later than the output of the reading sensor Lb for detecting B color light.

  Therefore, in order to simultaneously output the outputs of the RGB color light detection sensors Lr, Lg, and Lb in parallel, the outputs of the G and B color light detection sensors Lg and Lb are used as the R color light detection sensor Lr. Align with the output timing. That is, the read sensor Lg for G color light detection is delayed by 4 lines with respect to the output of the read sensor Lr for R color light detection, and the output of the read sensor Lb for B color light detection is read for R color light detection. The output of the sensor Lr is delayed by 8 lines.

  Based on these assumptions, the outputs of the reading sensors Lg, Lg, and Lb for detecting each color light of RGB are simultaneously output in parallel. Corrections are made so as to align with the output timing of the reading sensor Lr.

  4 includes a delay circuit 61 and a linear interpolation circuit 70 for integer lines. The delay circuit 61 of the timing correction unit 34G corrects the deviation of the integer lines between the R color and G color reading sensors. The delay circuit 61 is composed of a FIFO memory having a variable number of delay stages. The linear interpolation circuit 70 corrects the deviation of the decimal line between the R color and G color reading sensors corrected by the delay circuit 61.

  For example, in the timing correction unit 34G, in order to correct the integer lines by the delay circuit 61, the image reading data for a plurality of lines is delayed by several stages for the G color image reading data Dg by the FIFO memory, and the linear interpolation circuit 70 Then, in order to correct the decimal line, linear interpolation is performed between two lines before and after the image reading data Dg.

  Further, the delay circuit 61 of the timing correction unit 34B for the B color channel (not shown) corrects the deviation of the integer lines between the R color and B color reading sensors. The delay circuit 61 is composed of a FIFO memory having a variable number of delay stages. The linear interpolation circuit 70 corrects the deviation of the decimal line between the R color and B color reading sensors corrected by the delay circuit 61.

  For example, in the timing correction unit 34B, in order to correct the integer lines by the delay circuit 61, the image reading data for a plurality of lines is delayed with respect to the B color image reading data Db, and the decimal line is corrected by the linear interpolation circuit 70. In order to do this, linear interpolation is performed between two consecutive lines before and after the image reading data Db.

  Note that the delay circuit 61 for the integer line in the previous stage is omitted from the timing correction unit 34R for the R color channel. This is because the outputs of the reading sensors Lg and Lb for detecting the G and B color lights are aligned with the output timing of the reading sensor Lr for detecting the R color light. The linear interpolation circuit 70 of the timing correction unit 34R corrects the shift of the decimal line between the G color and B color reading sensors.

  For example, the linear interpolation circuit 70 of the timing correction unit 34R performs linear interpolation between two consecutive lines before and after the image reading data Dr in order to correct the decimal line. The linear interpolation circuit 70 of the timing correction units 34R, 34G, and 34B for the RGB color channels described above adjusts the ratio of linear interpolation between the front and rear lines according to the scaling factor Z. When the outputs of the read sensors Lr and Lb for detecting the R and B color lights are aligned with the output timing of the read sensor Lg for detecting the G color light, a delay corresponding to the preceding integer line from the timing correction unit 34G for the G color channel. The circuit 61 is omitted.

The linear interpolation circuit 70 shown in FIG. 4 includes an input terminal 62, one front line buffer 71, two multipliers 72 and 74, two registers 73 and 75, and one adder 76. .
A front line buffer 71 and a first multiplier 72 are connected to the delay circuit 61 through an input terminal 62. A register 73 is connected to the multiplier 72, and an interpolation coefficient k is set (set). The multiplier 72 operates to multiply the output of the delay circuit 61 by the interpolation coefficient k set in the register 73.

  The front line buffer 71 is composed of a FIFO memory, and operates to delay the output of the delay circuit 61 by one line. A second multiplier 74 is connected to the front line buffer 71. A register 75 is connected to the multiplier 74, and an interpolation coefficient 1-k is set (set). The multiplier 74 operates to multiply the output of the previous line buffer 71 by the interpolation coefficient 1-k set in the register 75. For each of the multipliers 72 and 74, an arithmetic circuit for multiplying 8 bits is used. For example, an integer operation is performed using a value obtained by scaling an interpolation coefficient k, (k−1) or the like by 256 times. The

  An adder 76 is connected to the multiplier 72 and the multiplier 74, and operates so as to add the output of the multiplier 72 and the output of the multiplier 74. An output terminal 77 is connected to the adder 76 so that the addition result by the adder 76 is output. As a result, it is possible to obtain image reading data (line data) Dr corresponding to an intermediate position between two lines before and after in the sub-scanning direction. By configuring the RGB color 3-channel timing correction units 34R, 34G, and 34B in this way, it is possible to reduce variations in MTF among the three RGB colors.

  In this example, MTF deterioration is suppressed by adjusting the delay correction amount in consideration of MTF from the beginning. That is, at least the R and G colors between the RGB color reading sensors Lr, Lg, and Lb are arranged so that the value of the interpolation coefficient k is in the inverse ratio relationship. The ratio of linear interpolation means that the blurring is the most when 0.5: 0.5. Therefore, it is desirable that the ratio is as close to 0: 1 or 1: 0 as possible, but if this is not possible, it is desirable to make the resolution (blurring degree) as uniform as possible among the three colors.

  In this example, the MPU 15 calculates an appropriate timing delay correction amount (r, g, b) ′ according to the variable magnification Z, where α is the offset amount and Z is the variable magnification. Here, a fractional amount of delay between lines handled by the linear interpolation circuit 70 is assumed to be x lines, an integer thereof is assumed to be N lines, and a deviation amount between the respective colors at the timing of reading the same position of the document 30 is assumed to be N + x lines.

Further, as described above, the arrangement pitch between the RGB color reading sensors Lr, Lg, and Lb (the interval between the R color reading sensor Lr and the G color reading sensor Lg, the G color reading sensor Lg and the B color reading). WZ is obtained from the product of the variable magnification Z, where w is the distance from the sensor Lb) and the sub-scanning speed at the same magnification reading is 100%. Between the shift amount N + x between the colors and the product wZ, the equation (1), that is,
N + x = wZ (1)
Is given.

In the MPU 15, when the delay amount of each RGB color based on the R color is (r, g, b) and the timing delay correction amount is (r, g, b) ′, the offset amount α is the delay amount of each RGB color. To (r, g, b). By an arithmetic operation that adds a delay amount equal to each value, the equation (2), that is,
(R, g, b) → (0, x + N, 2x + 2N)
(R, g, b) ′ → (1, x + 1 + N, 2x + 1 + 2N)
→ (-x + 1, 1 + N, x + 1 + 2N)
→ (α−x + 1, α + 1 + N, α + x + 1 + 2N) (2)
Is obtained.

In addition, considering the G color as a reference and including a negative number, the R color and the G color correct timing deviation for ± (N + x) lines, and therefore, the decimal part is expressed by the equation (3), that is,
(R, g, b) ′ = (− x, 0, + x) (3)
When the offset amount α is added, the decimal part is the equation (4), that is,
(R, g, b) ′ = (− x + α, α, x + α) (4)

Further, when evaluating the RGB color resolution (blur) in the linear interpolation circuit 70, it is only necessary to evaluate how close the interpolation coefficient k or 1-k is to 0.5. Hereinafter, an evaluation function for evaluating the resolution of RGB colors is represented by F (X), X = k. With respect to the definition of the evaluation value F (k), if the numerical value range is between 0 and 0.5 indicating how much the interpolation coefficient k deviates from the integer value, the evaluation value F (k) is expressed by the following equation (5). That is,
When 0 ≦ k ≦ 0.5, F (k) = k,
When 0.5 ≦ k ≦ 1, F (k) = 1−k (5)
Indicated by

Furthermore, for the convenience of explanation, the definition area as shown in FIG. 5 is expanded in both positive and negative directions. FIG. 5 is a diagram illustrating an extended example of the definition area of the interpolation coefficient k. In FIG. 5, the vertical axis Y is the evaluation function F (X), and the horizontal axis X is the interpolation coefficient k. In this example, when the interpolation coefficient k is k <0, k> 1, the evaluation value F (k) is an expression (6), that is,
F (k) = (| k−int (k) |) (6)
Indicated by Where int (k) is the integer part of k.

  Here, when the fractional line is x ≧ 1/2, the offset amount α is set as α = − (1−x) / 2, and when the decimal line is x ≦ 1/2, the offset amount α Is set to α = x / 2, the sum of the decimal parts of the timing delay correction amounts F (r) and F (g) is an integer such that 2α−x is 0 or −1, and the interpolation coefficient k is the previous line. In addition, the resolution is aligned due to the inverse ratio in the rear line.

  6A and 6B are diagrams illustrating an example of the relationship between the offset amount α and the timing delay correction amounts F (r), F (g), and F (b).

  In this embodiment, when the decimal line x is fixed and the offset amount α is varied, the timing delay correction amounts F (r), F (g), and F (b) change as shown in FIGS. 6A and 6B. . 6A and 6B, the horizontal axis is the offset amount α, and the vertical axis is the decimal line x.

  In this example, the offset amount α takes either α = ± F (x) / 2, depending on whether the decimal line x is greater than 0.5. In FIG. 6A, when the decimal line x is x ≦ 0.5, a value of α ≧ 0 is selected as the offset amount α. In FIG. 6B, when x> 0.5, the offset amount α selects a value of α ≦ 0. As a result, F (r) = F (g) is obtained.

Here, the absolute value | F (r) −F (g) | is at most 1/3 or less for any decimal line x, which is smaller than 1/2 when the offset amount α is not added. When the offset amount α obtained here is reflected in the timing delay correction amount on the basis of the R color, the expression (2) ′, that is,
(R, g, b) ′ = (α, N + x + α, 2 (N + x) + α)
Or
(R, g, b) ′ = (1 + α, N + x + α + 1, 2 (N + x) + α + 1)
(2) '
Is obtained. Depending on whether the offset amount α is positive or negative, the integer N of each term in the equation (2) ′ is applied to the delay circuit 61 of the integer line for the G and B color channels, and the fractional x of each term in the equation is R This is applied to the linear interpolation circuit 70 for color, G color and B color channels. As a result, the RGB color correction units 34R, 34G, and 34B have the same RGB color resolution (blurring condition), and can prevent color bleeding.

  Note that even if the timing delay correction amounts F (r) and F (b) are compared, the offset amount α is added, so that the fractional portion of the timing delay correction amounts F (r) and F (b) (however, In the range up to ± 1/2, the absolute value of the difference up to the nearest integer is related to the degree of blur). It can be as follows.

  FIGS. 7 and 8 are diagrams showing examples of correction of the interline delay in the linear interpolation circuit 70 when Z = 87.5% and α = 0.25 (parts 1 and 2).

  In this embodiment, on the premise that a time lag of 1 line or less occurs in the sub-scan timing deviation, each of the RGB color reading sensors Lr, Lg, Lb and the scaling factor Z = 87.5% and 3.5 are obtained. Correct the line deviation. Even if the delay circuit 61 described above compensates for the shift of the integer lines, a shift of 0.5 lines still occurs. If only the R and B colors are interpolated, only the R and B colors are blurred as described in the conventional example. Therefore, linear interpolation processing is also performed for the G color.

  In this example, in order to make the degree of resolution deterioration (MTF reduction) for performing linear interpolation calculation in the sub-scanning direction as close as possible between RGB colors, it is as close to 0: 100% or 100%: 0 as possible (50%: 50). % Is the most blurred). For example, the linear interpolation ratios for each of the RGB colors are matched or reversed so that they are aligned. At least two colors are made to coincide with each other so that differences between the three colors as a whole can be reduced as much as possible.

  Accordingly, when the decimal point is set such that the zoom ratio Z is 87.5%, the G color MTF is lowered and the R and G color MTFs are raised. That is, the ratio of the G color linear interpolation processing is reduced from 1: 0 to 0.75: 0.25. Instead, the ratio of the R and G color linear interpolation processing is changed from 0.5: 0.5 to 0.25: 0.75. In this way, the degree of deterioration of the MTF for each color of RGB is made uniform so as to prevent the deterioration of the MTF when viewed in all the colors of RGB.

  In this example, when the zoom ratio is Z = 87.5%, the width of 4 lines between the reading sensors Lr, Lg, and Lb of the adjacent RGB colors is 4 × 87.5% = sub-line of 3.5 lines. Reading is performed in scanning time. Regarding the deviation amount of the 3.5 line interval, the N = 3 line of the integer part is corrected by the delay circuit 61 of the timing correction unit 34G, and the N = 7 line of the integer part is corrected by the delay circuit 61 of the timing correction unit 34B. The decimal part x = 0.5 lines is linearly interpolated between two consecutive lines by the linear interpolation circuit 70 of each timing correction unit 34R, 34G, 34B.

  In the linear interpolation circuit 70 of each of the timing correction units 34R, 34G, and 34B, the resolution (blurring degree) is made as uniform as possible. According to the expression (2) ′ described above, the timing delay correction amount (r, g, b) ′ between the RGB color reading sensors Lr, Lg, Lb ′ is set to the same amount of deviation and the delay amount of each RGB color. Since it may be added to (r, g, b), for example, α = 0.25 can be added as the offset amount α. The interpolation coefficient k is set to k: 1-k = 0.25: 0.75 or 0.75: 0.25 to correct the decimal part x = 0.5 line.

  According to the timing correction example shown in FIG. 7, the timing correction delay amount based on the G color F (r) = N + x, F (g) = N, and F (b) = N + x is equivalent to −0.25 line. When the offset amount α is added, the respective timing correction delay amounts are F (r) = 0 + 0.25, F (g) = 3 + 0.75, and F (b) = 7 + 0.25. Therefore, the timing correction unit 34R delays 0 lines for R color, the delay circuit 61 of the timing correction unit 34G delays 3 lines for G color, and the delay circuit 61 of the timing correction unit 34B delays 7 lines for B color. Sets the FIFO delay amount.

Further, in the linear interpolation circuit 70 of each timing correction unit 34R, 34G, 34B, with respect to the interpolation coefficient k between the two preceding and following lines, the image value of the current line of R color is R _n , and the image of the previous line The value is R _n−1 , the image value of the current line of G color is G _n , the image value of the previous line is G _n−1 , and the image value of the current line of B color is B _n , If the image value of the previous line is B _n-1 ,
R _n-1 : R _n = 75%: 25%
G _n-1 : G _n = 25%: 75%
B _n-1 : B _n = 75%: 25%
In other words, in the linear interpolation circuit 70 of each timing correction unit 34R, 34G, 34B, the linear interpolation amount (interpolation coefficient k, 1-k) between the two lines before and after is set. Interpolation coefficients k and 1-k have the same ratio of linear interpolation amounts between the two front and rear lines, or are inverse ratios with their complements as coefficient k, so that the resolution matches.

In this example, as shown in FIG. 8, in the subsequent stage of the delay circuit 61, the linear interpolation circuit 70 performs a new interpolation process on the R color from the pixel value R ₁ of the first line and the pixel value R ₂ of the second line. The pixel value R _1.75 is output. The second line pixel value R ₂ as a new pixel value R _2.75 which is interpolated from the pixel values R ₃ of the third line of the output in the same way. Pixel values R _1.75 , R _2.75 ... Constitute image read data Dr.

Further, a new pixel value B _1.75 obtained by _performing interpolation processing on the B color from the pixel value B ₁ of the first line and the pixel value B ₂ of the second line is output. The second line pixel value B ₂ with the new pixel value B _2.75 were interpolated from the pixel values B ₃ of the third line of the output in the same way. Pixel values B _1.75 , B _2.75 ... Constitute image read data Db.

In addition to the R and B colors, the G color is also linearly interpolated at a ratio of 1/4: 3/4 from the sub-scanning adjacent pixels. That is, a new pixel value G _1.25 obtained by performing interpolation processing on the G color from the pixel value G ₁ of the first line and the pixel value G ₂ of the second line is output. The second line pixel value G ₂ and the new pixel value G _2.25 were interpolated from the pixel values G ₃ of the third line of the output in the same way. Pixel values G _1.25 , G _2.25 ... Constitute image reading data Dg, and Dr, Dg, Db constitute image reading data Dout.

  As described above, the ratios of the R and G interpolation coefficients k are adjusted to prevent the MTF from being deteriorated or uneven. That is, the resolution of the G color is blurred by linear interpolation, but the degree of blurring of the other R and B colors is reduced, and the MTFs can be made uniform for the entire RGB color.

Next, an image reading method according to the present invention will be described. FIG. 9 is a flowchart illustrating an example of image reading in the color scanner 100.
In this embodiment, it is assumed that a color image is read from an arbitrary document 30 according to the setting of the variable magnification Z. In the color scanner 100, a one-dimensional image sensor 58 is used in which the RGB scanning sensors Lr, Lg, and Lb have a distance of 4 lines in the sub-scanning direction. In this example, the RGB color timing correction units 34R, 34G, and 34B are arranged in the sub-scanning direction of the read sensors Lr, Lg, and Lb for detecting light of R, G, and B colors with respect to the light information read by the image sensor 58. Correct the misalignment.

  Further, by performing an interpolation operation on each of the pixel values of the three colors and shifting the reference position by the offset amount α, the degree of variation in MTF between the RGB colors is made uniform. In this processing, the image resolution between the color components is corrected by adjusting the ratio of linear interpolation between the preceding and following reading lines.

  Under these image reading conditions, the MPU 15 waits for setting of the document 30 in step A1 of the flowchart shown in FIG. For example, the user opens the ADF 40 on the platen glass upward, places the document 30 with the image forming surface down on the platen glass, and then operates the ADF 40 downward to cover the platen cover 50. As a result, the document 30 placed on the platen glass is covered with the platen cover 50 with the image forming surface facing downward. The document 30 on the platen glass is recognized by the MPU 15 by a sheet detection signal indicating that “the document has been set on the platen glass” by a known sheet detection technique.

  Next, in step A2, the MPU 15 inputs and sets the variable magnification Z. The variable magnification Z is set by the user using the operation panel 48. The scaling factor Z can be input as an integer and a decimal point. The default value of the scaling factor Z is 100%. For example, 87.5% is set as the scaling factor Z of the decimal point. In step A3, the MPU 15 branches the control based on the ADF mode or the platen mode. In this example, since the platen mode is set, the process proceeds to step A4, and the control is branched by pressing the start or stop button. When the start button is pressed, the process proceeds to step A5, and the optical system drive control unit 37 is optically driven relative to the document 30 using the paper detection signal and the start-on signal generated by pressing the start button as a trigger. Starts moving in the sub-scanning direction.

  In step A6, the image sensor 58 reads the document 30. At this time, the image sensor 58 reads the light information of the R color, the G color, and the B color at the same time at different positions in the sub-scanning direction of the document 30 irradiated with light from the light source 53. An RGB color image reading signal Sout obtained by reading the document 30 is output from the image sensor 58 to the control unit 35. The image reading signal Sout is output in units of one page of the document 30.

  The control unit 35 receives the image reading signal Sout from the image sensor 58, and performs A / D conversion on the image reading signal Sout by the analog signal processing units 31R, 31G, and 31B of the RGB color channels. In this example, the image reading data Dr output from the analog signal processing unit 31R for the R color channel, the image reading data Dg output from the analog signal processing unit 31G for the G color channel, and the analog signal processing unit 31B for the B color channel. With respect to the output image read data Db, the delay between lines is corrected.

  For example, in the G color channel timing correction unit 34G shown in FIG. 4, in order to correct the integer lines by the delay circuit 61, the image read data for three lines is delayed by several stages for the image read data Dg by the FIFO memory. . In the linear interpolation circuit 70, in order to correct the decimal 0.5 line, linear interpolation is performed between two lines before and after the image reading data Dg.

  Further, in the B color channel timing correction unit 34B, in order to correct the integer lines by the delay circuit 61, the image read data for seven lines is delayed with respect to the image read data Db. In the linear interpolation circuit 70, linear interpolation is performed between two lines before and after the image reading data Db in order to correct the decimal 0.5 line. In the linear interpolation circuit 70 of the timing correction unit 34R for the R color channel, linear interpolation is performed between two lines before and after the image reading data Dr in order to correct the decimal 0.5 line. The linear interpolation circuit 70 of the timing correction units 34R, 34G, and 34B for the RGB color channels described above adjusts the ratio of linear interpolation between the front and rear lines according to the scaling factor Z.

  The image read data Dr, Dg, Db (= Din, Dout) of the above-mentioned RGB color 3 channels is stored in the image memory 36. The image reading data Din is stored in units of one page, and an end of flag (EOF) is added to the image reading data Din of the page. When the scanner 100 is used by connecting a printer or the like, the image reading data Dout to which an end of flag or the like is added for each page is output to the printer or the like. Thereafter, the process proceeds to step A11.

  When the user sets the document 30 on the ADF 40 in step A1, a sheet detection signal indicating that “the document is set on the ADF 40” is output to the MPU 15 by a known sheet detection technique. In step A2, the MPU 15 inputs and sets the variable magnification Z from the user in the same manner as in the platen mode. Thereafter, the process proceeds to step A3, and the MPU 15 branches the control based on the ADF mode or the platen mode. In this example, since the ADF mode is set, the process proceeds to step A7, and the control is further branched by pressing the start or stop button.

  In this example, when the start button is pressed, the process proceeds to step A8 where the original 30 is fed by the roller 43. At this time, the optical system drive control unit 37 starts feeding the document 30 in the sub-scanning direction relative to the optical system including the image sensor 58 using a paper detection signal and a start-on signal when the start button is pressed as a trigger. To do. Thereafter, the process proceeds to step A9 to execute an image reading process.

  In this example, when the document 30 reverses the roller 43 in a U shape, the image sensor 58 reads the surface of the document 30. At this time, the image sensor 58 reads the light information of the R color, the G color, and the B color at the same time at different positions in the sub-scanning direction of the document 30 irradiated with light from the light source 53. The image reading signal Sout is output from the image sensor 58 to the control unit 35 (ADF mode).

  Similarly to the platen mode, the control unit 35 receives the image reading signal Sout from the image sensor 58, and the image reading signal Sout is A / D converted by the analog signal processing units 31R, 31G, and 31B of the RGB color channels. To do. Even in the ADF mode, the inter-line delay is corrected for the RGB color three-channel image read data Dr, Dg, and Db output from the RGB color channel analog signal processing units 31R, 31G, and 31B. The image read data Dr, Dg, Db (= Din, Dout) are stored in the image memory 36 in the same manner as in the platen mode. Alternatively, the image reading data Dout is output to a printer or the like with an end-of-flag or the like added to each page.

  Thereafter, the process proceeds to step A10, and the MPU 15 determines whether or not the document 30 is the last page based on the detection of the paper detection signal. If the original 30 is not the last page, that is, if the original 30 remains on the original placement portion 41, the paper detection signal indicates “paper present”, so the process returns to step A9 to perform the above-described image reading process. It is made to repeat. If the document 30 is the last page, the process proceeds to step A11 after completing the image reading process.

  If the stop button is pressed in steps A4 and A7 described above, the process moves to step A11, and the MPU 15 makes an end determination regarding the image reading process. For example, the power-off information is detected and the image reading process is terminated. If the power-off information is not detected, the process returns to step A1 to wait for the document set. Thereafter, the above-described processing is repeated.

  As described above, according to the color scanner and the image reading method as the first embodiment of the present invention, when a color image is read from an arbitrary document 30 according to the setting of the variable magnification Z, the timing correction unit 34R, Reference numerals 34G and 34B denote sub-scanning directions of the reading sensors Lr, Lg, and Lb for detecting light of R, G, and B colors with respect to optical information obtained by reading the image sensor 58 from the original 30 moved by the optical driving unit 59. Correct the misalignment. Further, the timing correction units 34R, 34G, and 34B adjust the ratio of linear interpolation between the preceding and following reading lines with respect to the optical information subjected to the positional deviation correction, thereby adjusting the image resolution between the R, G, and B color components. It is made to correct.

  Therefore, even when there is a change in the sub-scanning speed due to linear interpolation using the variable magnification Z, the direction in which the relative difference between the R, G, and B image resolutions is reduced, in other words, the resolution is It is possible to control in the direction of alignment, and color bleeding can be prevented. In addition, since the ratio of linear interpolation between the preceding and succeeding reading lines can be adjusted according to the scaling factor Z, even if (scaling factor Z) x (sensor line interval) has a value after the decimal point, For read signals such as thin lines, the read signals for R, G, and B colors can be brought close to the same level.

  Thereby, variation in image resolution (MTF) between the three colors of R, G, and B can be reduced. Furthermore, the MTF correction circuit in the latter stage of the conventional example can be omitted. The color scanner 100 can be sufficiently applied to a color copying machine, a color facsimile machine, and a color complex machine thereof.

FIG. 10 is a conceptual diagram showing a configuration example of a color copying machine 200 as a second embodiment according to the present invention.
In this embodiment, the color copying machine 200 having the color scanner function shown in FIGS. 1 to 9 is configured, and a color image is read from an arbitrary document 30 based on the setting of the variable magnification Z and the ADF mode or the platen mode. A color image corresponding to the zoom ratio Z is formed.

  A color copying machine 200 shown in FIG. 10 is an example of an image forming apparatus, reads a color image formed on an arbitrary document 30, acquires image information, and superimposes colors on the image forming body based on the image information. A device for forming a color image. The color copying machine 200 includes a copying machine main body 201 and a color scanner 100. The scanner 100 is an example of an image reading apparatus and incorporates the functions described in the first embodiment, and reads a color image formed on the document 30.

  An ADF (automatic document feeder) 40 and a scanner unit (image reading / scanning / exposure device) 11 are arranged on the upper part of the copying machine main body 201. The document 30 placed on the document placement unit 41 of the ADF 40 is transported by a transport unit, and an image on one or both sides of the document 30 is scanned and exposed by the optical system of the scanner unit 11, and incident light reflecting image reading is imaged. It is read by the sensor 58.

  As described with reference to FIG. 2, the image sensor 58 includes three reading sensors Lr, Lg, and Lb for detecting R, G, and B color light configured by arranging a plurality of light receiving element arrays in the main scanning direction. Pixels are divided at different positions in the sub-scanning direction of the document 30 that are arranged at a predetermined distance in the sub-scanning direction and irradiated with light from the light source 53, and R, G, and B color light information is obtained. It is made to read at the same time.

  In addition to the image sensor 58, the scanner unit 11 includes a first platen glass 51, a second platen glass 52, a light source 53, mirrors 54, 55, 56, an imaging optical unit 57, and an optical drive unit 59. Yes. The optical drive unit 59 operates to move the document 30 or the image sensor 58 relatively in the sub-scanning direction. In this example, the optical drive unit 59 is provided with a motor 59 ', and moves the optical system such as the light source 53, the mirrors 54, 55, and 56 in the sub-scanning direction. In this example, the optical drive unit 59 is controlled by a motor so as to vary the reading speed in the sub-scanning direction according to the variable magnification Z.

  The analog image reading signal Sin photoelectrically converted by the image sensor 58 is subjected to analog processing, A / D conversion, shading correction, image compression processing, processing, and the like in an image processing unit (not shown) to become digital image data Din. . The image reading data Din is converted into image data Dy, Dm, Dc, Dk for Y, M, C, BK colors, and then image writing units (exposure means) 3Y, 3M, 3C constituting the image forming means 60. To 3K.

  The ADF 40 described above is provided with automatic double-sided document conveying means. The ADF 40 continuously reads the contents of a large number of documents 30 fed from the document placing section 41 at once, and accumulates the document contents in a storage means (electronic RDH function). This electronic RDH function is conveniently used when copying the contents of a large number of documents by the copying function or when transmitting a large number of documents 30 by the facsimile function.

  The copying machine main body 201 is called a tandem type color image forming apparatus. The copying machine main body 201 is provided with an image forming means 60. The image forming unit 60 forms a color image based on the image data Dy, Dm, Dc, Dk obtained by reading with the scanner 100. The image forming means 60 includes a plurality of sets of image forming units (image forming systems) 10Y, 10M, 10C, and 10K each having an image forming body for each color, an endless intermediate transfer belt (image transfer system) 6, and A sheet feeding / conveying unit including a sheet re-feeding mechanism (ADU mechanism) and a fixing device 17 for fixing the toner image are provided.

  The image forming unit 10Y that forms a yellow (Y) image includes a photosensitive drum 1Y as an image forming body that forms a Y-color toner image, and a Y-color charging disposed around the photosensitive drum 1Y. Means 2Y, exposure means 3Y, developing device 4Y, and image forming body cleaning means 8Y. An image forming unit 10M for forming a magenta (M) color image includes a photosensitive drum 1M as an image forming body for forming an M color toner image, an M color charging unit 2M, an exposure unit 3M, and a developing device 4M. And an image forming member cleaning means 8M.

  An image forming unit 10C for forming a cyan (C) color image includes a photosensitive drum 1C as an image forming body for forming a C toner image, a charging unit 2C for C color, an exposure unit 3C, and a developing device 4C. And an image forming member cleaning means 8C. An image forming unit 10K that forms a black (BK) color image includes a photosensitive drum 1K as an image forming body that forms a BK color toner image, a charging unit 2K for BK color, an exposure unit 3K, and a developing device 4K. And an image forming member cleaning means 8K.

  The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit. Development by the developing devices 4Y, 4M, 4C, and 4K is performed by reversal development in which a development bias in which an AC voltage is superimposed on a DC voltage having the same polarity (negative polarity in this embodiment) as the polarity of the toner to be used is applied. . The intermediate transfer belt 6 is wound around a plurality of rollers and is rotatably supported. Each of the Y, M, C, and BK colors formed on each of the photosensitive drums 1Y, 1M, 1C, and 1K. A toner image is transferred.

  Here, an outline of the image forming process will be described below. Each color image formed by the image forming units 10 </ b> Y, 10 </ b> M, 10 </ b> C, and 10 </ b> K is subjected to primary transfer bias (not shown) having a polarity (positive polarity in this embodiment) opposite to the toner to be used. Rollers 7Y, 7M, 7C, and 7K sequentially transfer onto the rotating intermediate transfer belt 6 to form a color image (color image: color toner image) that is synthesized by superimposing colors (primary transfer). .

  Further, below the image forming unit 60, sheet feeding cassettes 20A, 20B, and 20C constituting a sheet feeding unit are provided. The paper P accommodated in the paper feed cassette 20A and the like is fed by the feed roller 21 and the paper feed roller 22A provided in the cassette 20A and the like, and passes through the transport rollers 22B, 22C and 22D, the registration roller 23, and the like. The sheet is conveyed to the next transfer roller 7A, and the color image is collectively transferred from the intermediate transfer belt 6 to the sheet P on one surface (front surface) on the sheet P (secondary transfer).

  The paper P on which the color image has been transferred is fixed by the fixing device 17, is sandwiched between the paper discharge rollers 24, and is placed on a paper discharge tray 25 outside the apparatus. The transfer residual toner remaining on the peripheral surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the transfer is cleaned by the image forming body cleaning means 8Y, 8M, 8C, and 8K, and enters the next image forming cycle.

  At the time of double-sided image formation, the paper P formed on one side (front surface) and discharged from the fixing device 17 is branched from the document 30 discharge path by the branching unit 26, and each of the lower sides constituting the paper feeding and conveying unit. , The front and back are reversed by a reversing conveyance path 27B which is a refeeding mechanism (ADU mechanism), passes through the refeeding conveyance section 27C, and merges at the sheet feeding roller 22D.

  The reversely conveyed sheet P is conveyed again to the secondary transfer roller 7A through the registration roller 23, and a color image (color toner image) is collectively transferred onto the other side (back side) of the sheet P. On the other hand, after the color image is transferred to the paper P by the secondary transfer roller 7A, the residual toner is removed by the intermediate transfer belt cleaning means 8A from the intermediate transfer belt 6 that has separated the curvature of the paper P.

The time of forming these images, 52.3~63.9kg / m ² (1000 sheets) as the paper P about thin and 64.0~81.4kg / m ² (1000 sheets) of approximately plain paper, 83 .0~130.0kg / m ² (1000 sheets) about cardboard and 150.0kg / m ² (1000 sheets) about super thick paper is used. The thickness of the paper P (paper thickness) is about 0.05 to 0.15 mm.

  FIG. 11 is a block diagram illustrating a configuration example of a control system of the color copying machine 200. A color copying machine 200 shown in FIG. 11 includes a scanner unit 11, a control unit 35 ', a communication unit 19, a paper feeding unit 20, an operation panel 48, and an image forming unit 60.

  The scanner unit 11 includes the image sensor 58 and the optical drive unit 59 described with reference to FIG. The control unit 35 ′ includes an MPU 15, analog signal processing units 31R, 31G, and 31B for RGB colors, correction processing units 32R, 32G, and 32B, memory access control units 33R, 33G, and 33B, an image memory 36, and an optical system drive control unit. 37, a color conversion processing unit 38 and timing control units 39Y, 39M, 39C, and 39K are included. In addition, since the thing of the same name and code | symbol demonstrated in the 1st Example has the same function, the description is abbreviate | omitted.

  In this example, the operation panel 48 includes the operation unit 14 formed from a touch panel and the display unit 18 formed from a liquid crystal display element (LCD). The operation unit 14 is operated so as to set a zoom ratio Z when reading the document 30, and input image forming conditions such as setting of image density, selection of paper size, setting of the number of copying machines, and the like. Operated. The display unit 18 reduces the size of the document image based on the image reading data Dout acquired by the scanner unit 11 and displays a preview, or displays selection items related to image forming conditions based on the display data D2. Note that the image forming conditions and paper cassette selection information set on the operation panel 48 are output to the MPU 15 as operation data D3.

  In this example, the MPU 15 includes a ROM (Read Only Memory) 94, a CPU (Central Processing Unit) 95, and a work RAM (Random Access Memory) 96. The ROM 94 stores system program data for controlling the entire copying machine. The RAM 96 temporarily stores control commands and the like when executing the image processing mode. When the power is turned on, the CPU 95 reads the system program data from the ROM 94, starts up the system, and controls the entire copying machine.

  For example, the MPU 15 controls the image memory 36 or the like based on the image forming conditions set by the operation panel 48, or performs color processing based on the image data Dy, Dm, Dc, Dk color-converted by the color conversion processing unit 38. The image forming unit 60 is controlled to form an image. In this example, the MPU 15 outputs an image processing control signal S2 to the color conversion processing unit 38.

  In addition, the MPU 15 controls input / output of the correction processing units 32R, 32G, and 32B based on the scaling factor Z set by the operation panel 48 in the ADF mode or the platen mode. For example, the MPU 15 outputs the interpolation coefficient k corresponding to the variable magnification Z to the timing correction units 34R, 34G, and 34B. In the timing correction units 34R, 34G, and 34B, the interpolation coefficient k is set in the register 73, and the interpolation coefficient 1-k is set in the register 75. For details, refer to the first embodiment.

  In this example, a color conversion processing unit 38 is connected to the memory access control units 33R, 33G, and 33G shown in FIG. In the color conversion processing unit 38, the RGB color image read data Dout (= Dr, Dg, Db) read from the image memory 36 is converted into YMCK color image data Dy, Dm, Color conversion is performed to Dc and Dk. The color conversion processing unit 38 is provided with a lookup table (LUT) (not shown) for color conversion.

  Timing control units 39Y, 39M, 39C, and 39K are connected to the color conversion processing unit 38. The timing control unit 39Y receives the image data Dy from the color conversion processing unit 38 based on the timing control signal S3, performs PWM γ correction processing on the image data Dy, performs frequency conversion processing on the image data Dy, and based on the image data Dy. Thus, index synchronization detection processing is performed, or image data Dy is subjected to PWM (pulse width modulation) processing to output a laser drive signal Sy. The timing control signal S3 is output from the MPU 15 to each timing control unit 39Y, 39M, 39C, 39K.

  Similarly, the timing control unit 39M inputs image data Dm, performs PWM γ correction processing on the image data Dm, performs frequency conversion processing on the image data Dm, performs index synchronization detection processing based on the image data Dm, The image data Dm is PWM-processed to output a laser drive signal Sm.

  Similarly, the timing control unit 39C inputs image data Dc, performs PWM γ correction processing on the image data Dc, performs frequency conversion processing on the image data Dc, performs index synchronization detection processing based on the image data Dc, The image data Dc is PWM-processed to output a laser drive signal Sc.

  Similarly, the timing control unit 39K inputs the image data Dk, performs PWM γ correction processing on the image data Dk, performs frequency conversion processing on the image data Dk, performs index synchronization detection processing based on the image data Dk, The image data Dk is PWM-processed to output a laser drive signal Sk.

  In this example, the MPU 15 outputs an image formation control signal S4 to the image forming unit 60. The image forming unit 60 operates to input a laser drive signal Sy, Sm, Sc, Sk and an image formation control signal S4 to form a color image on a predetermined paper P. In this example, the image forming unit 60 is provided with laser diodes LDy, LDm, LDc, and LDk. The laser diode LDy generates a laser beam for Y color having a predetermined intensity based on the laser drive signal Sy.

  Similarly, the laser diode LDm generates a laser beam for M color having a predetermined intensity based on the laser drive signal Sm. The laser diode LDc generates a laser beam for C color having a predetermined intensity based on the laser drive signal Sc. The laser diode LDk generates a BK color laser beam having a predetermined intensity based on the laser drive signal Sk. An example of the internal configuration of the image forming unit 60 has been described with reference to FIG.

  In this example, the sheet feeding means 20 is connected to the system bus 29, and the sheet feeding cassettes 20A to 20C shown in FIG. 10 are controlled based on the sheet feeding control signal S5. For example, the paper feed unit 20 selects one of the paper feed cassettes 20A, 20B, and 20C based on the paper feed control signal S5, and transports the paper P fed from the paper feed cassette 20A, 20B, or 20C to the image forming system. To be made. The paper feed control signal S5 is supplied from the MPU 15 to the paper feed means 20.

  The communication means 19 is connected to a communication line such as a LAN, and is used when performing communication processing with an external computer or the like. For example, when a document image having a desired variable magnification Z read by the color copying machine 200 is image-formed and output by an external printer or the like, the communication means 19 transmits print data Dout ′ to the external printer. . The print data Dout 'is subjected to color conversion processing by the color conversion processing unit 38, and a color image can be formed on the basis of the variable magnification Z even in an external multi-function peripheral or printer.

Next, an example of image processing in the color copying machine 200 will be described. FIG. 12 is a flowchart showing an example of image processing in the color copying machine 200.
In this embodiment, it is assumed that a color image is formed by reading a color image from an arbitrary document 30 according to the setting of the zoom ratio Z. In the color scanner 100, a one-dimensional image sensor 58 is used in which the RGB scanning sensors Lr, Lg, and Lb have a distance of 4 lines in the sub-scanning direction. In this example, the RGB color timing correction units 34R, 34G, and 34B are arranged in the sub-scanning direction of the read sensors Lr, Lg, and Lb for detecting light of R, G, and B colors with respect to the light information read by the image sensor 58. Correct the misalignment.

  Further, by performing an interpolation operation on each of the pixel values of the three colors and shifting the reference position by the offset amount α, the degree of variation in MTF between the RGB colors is made uniform. In this processing, the image resolution between the color components is corrected by adjusting the ratio of linear interpolation between the preceding and following reading lines.

  With these as image forming conditions, the MPU 15 waits for a copy request in step Q1 of the flowchart shown in FIG. For example, the user opens the ADF 40 on the platen glass upward, places the document 30 with the image forming surface down on the platen glass, and then operates the ADF 40 downward to cover the platen cover 50. As a result, the document 30 placed on the platen glass is covered with the platen cover 50 with the image forming surface facing downward. The presence / absence of a document on the platen glass is output to the MPU 15 by a paper detection signal. The MPU 15 recognizes the copy request based on the paper detection signal.

  If there is a copy request, the process proceeds to step Q2, and the MPU 15 inputs and sets the zoom ratio Z and other image forming conditions. Here, the user operates the operation panel 48 to input image forming conditions such as the variable magnification Z, the paper size, and the number of copies. The variable magnification Z can be input as an integer and a decimal point. The default value of the scaling factor Z is 100%. For example, 87.5% is set as the scaling factor Z of the decimal point.

  In step Q3, the MPU 15 branches the control based on the ADF mode or the platen mode. In this example, since the platen mode is set, the process proceeds to step Q4, and the control is branched by pressing the start or stop button. If the start button is pressed, the process proceeds to step Q5, and the optical system drive control unit 37 controls the motor 59 ′ of the optical drive unit 59 to perform motor control using the paper detection signal and the start-on signal generated by pressing the start button as a trigger. The signal S1 is output to start moving the optical drive system in the sub-scanning direction relative to the document 30.

  In step Q6, the image sensor 58 executes image reading processing of the document 30. At this time, the image sensor 58 reads the light information of the R color, the G color, and the B color at the same time at different positions in the sub-scanning direction of the document 30 irradiated with light from the light source 53. An RGB color image reading signal Sout obtained by reading the document 30 is output from the image sensor 58 to the control unit 35 ′. The image reading signal Sout is output in units of one page of the document 30.

  The control unit 35 'receives the image reading signal Sout from the image sensor 58, and A / D converts the image reading signal Sout by the analog signal processing units 31R, 31G, and 31B of the RGB color channels. In this example, the image reading data Dr output from the analog signal processing unit 31R for the R color channel, the image reading data Dg output from the analog signal processing unit 31G for the G color channel, and the analog signal processing unit 31B for the B color channel. With respect to the output image read data Db, the delay between lines is corrected.

  For example, in the G color channel timing correction unit 34G shown in FIG. 4, in order to correct the integer lines by the delay circuit 61, the image read data for three lines is delayed by several stages for the image read data Dg by the FIFO memory. . In the linear interpolation circuit 70, in order to correct the decimal 0.5 line, linear interpolation is performed between two lines before and after the image reading data Dg.

  Further, in the B color channel timing correction unit 34B, in order to correct the integer lines by the delay circuit 61, the image read data for seven lines is delayed with respect to the image read data Db. In the linear interpolation circuit 70, linear interpolation is performed between two lines before and after the image reading data Db in order to correct the decimal 0.5 line. In the linear interpolation circuit 70 of the timing correction unit 34R for the R color channel, linear interpolation is performed between two lines before and after the image reading data Dr in order to correct the decimal 0.5 line. The linear interpolation circuit 70 of the timing correction units 34R, 34G, and 34B for the RGB color channels described above adjusts the ratio of linear interpolation between the front and rear lines according to the scaling factor Z.

  The above-described RGB color three-channel image read data Dr, Dg, Db is encoded and compressed by the memory access control units 33R, 33G, 33B, etc., and is temporarily stored in the image memory 36. The image reading data Din is stored in units of one page, and an end of flag (EOF) is added to the image reading data Din of the page.

  Then, the process proceeds to step Q7 to execute image forming processing. At this time, the memory access control units 33R, 33G, 33B, etc. read the RGB three-channel image read data Dr, Dg, Db from the image memory 36, decode the image read data Dr, Dg, Db, and decompress them. The decompressed image read data Dr, Dg, and Db are transferred to the color conversion processing unit 38 under the control of the memory access control units 33R, 33G, and 33B.

  The color conversion processing unit 38 converts the RGB color image read data Dr, Dg, Db read from the image memory 36 into YMCK color image data Dy, Dm, Dc, Dk based on the image processing control signal S2. Color conversion is made. The color-converted image data Dy, Dm, Dc, and Dk are output to the timing controllers 39Y, 39M, 39C, and 39K. At this time, the MPU 15 outputs a timing control signal S3 to each timing control unit 39Y, 39M, 39C, 39K.

  In the timing control unit 39Y, the image data Dy is input from the color conversion processing unit 38 based on the timing control signal S3, the image data Dy is subjected to PWM γ correction processing, and then subjected to frequency conversion processing. Further, the timing control unit 39Y detects an index signal based on the image data Dy and performs an index synchronization detection process in order to align the timing of the laser beam. Further, the timing control unit 39Y generates a laser drive signal Sy by subjecting a predetermined pulse signal to PWM (pulse width modulation) processing based on the image data Dy.

  Similarly, the timing control unit 39M inputs the image data Dm, performs PWM γ correction processing, frequency conversion processing, and index synchronization detection processing, or performs PWM processing on the image data Dm and outputs the laser drive signal Sm. Made. Similarly, the timing control unit 39C also receives the image data Dc, performs PWM γ correction processing, frequency conversion processing, index synchronization detection processing, or PWM-processes the image data Dc to output the laser drive signal Sc. Made. Similarly, the timing control unit 39K receives the image data Dk, performs PWM γ correction processing, frequency conversion processing, and index synchronization detection processing, or performs PWM processing on the image data Dk and outputs a laser drive signal Sk. Made.

  These laser drive signals Sy, Sm, Sc, Sk are output to the image forming means 60 together with the image formation control signal S4. The image forming unit 60 operates to input a laser drive signal Sy, Sm, Sc, Sk and an image formation control signal S4 to form a color image on a predetermined sheet P. For example, the laser diode LDy generates a laser beam for Y color having a predetermined intensity based on the laser drive signal Sy. The Y-color laser beam is scanned in the main scanning direction based on the image formation control signal S4, and is irradiated onto the photosensitive drum 1Y shown in FIG. An electrostatic latent image is exposed on the photosensitive drum 1Y by a laser beam for Y color (image writing). The electrostatic latent image exposed on the photosensitive drum 1Y is developed with a Y-color toner. The developed Y color toner image is transferred to the intermediate transfer belt 6.

  Similarly, the laser diode LDm generates a laser beam for M color having a predetermined intensity based on the laser drive signal Sm. The laser beam for M color is scanned in the main scanning direction based on the image formation control signal S4, and is irradiated onto the photosensitive drum 1M. The photosensitive drum 1M is exposed to an electrostatic latent image by an M color laser beam. The electrostatic latent image exposed on the photosensitive drum 1M is developed with an M color toner. The developed M color toner image is transferred to the intermediate transfer belt 6 and superimposed on the other colors on the belt.

  Further, the laser diode LDc generates a laser beam for C color having a predetermined intensity based on the laser drive signal Sc. The laser beam for C color is scanned in the main scanning direction based on the image forming control signal S4, and is irradiated onto the photosensitive drum 1C. An electrostatic latent image is exposed on the photosensitive drum 1C by a C-color laser beam. The electrostatic latent image exposed on the photosensitive drum 1C is developed with a C-color toner agent. The developed C color toner image is transferred to the intermediate transfer belt 6 and superimposed on the other Y and M colors on the belt.

  Furthermore, the laser diode LDk generates a BK color laser beam having a predetermined intensity based on the laser drive signal Sk. The laser beam for BK color is scanned in the main scanning direction and irradiated to the photosensitive drum 1K. An electrostatic latent image is exposed on the photosensitive drum 1K by a laser beam for K color. The electrostatic latent image exposed on the photosensitive drum 1K is developed with a BK toner. The developed BK color toner image is transferred to the intermediate transfer belt 6. The color toner image superimposed on the intermediate transfer belt 6 is transferred onto a predetermined paper P. The paper P is fed out from a paper feed cassette 20A, 20B, or 20C controlled by the paper feed means 20 based on a paper feed control signal S5. The paper feed control signal S5 is supplied from the MPU 15 to the paper feed means 20.

  When the user sets the document 30 on the ADF 40 in step Q1, a paper detection signal indicating that “the document is set on the ADF 40” is output to the MPU 15. In step Q2, the MPU 15 inputs and sets the zoom ratio Z and image forming conditions from the user in the same manner as in the platen mode. Thereafter, the process proceeds to step Q3, and the MPU 15 branches the control based on the ADF mode or the platen mode. In this example, since the ADF mode is set, the process proceeds to step Q8, and the control is further branched by pressing the start or stop button.

  In this example, when the start button is pressed, the process proceeds to step Q9 and the document 30 is started to be fed by the roller 43. At this time, the optical system drive control unit 37 uses a paper detection signal and a start-on signal by pressing the start button as a trigger, and the optical system drive control unit 37 outputs a motor control signal S1 to the motor 59 ′ of the optical drive unit 59. Then, the document 30 is started to be fed in the sub-scanning direction relative to the optical system including the image sensor 58.

  Thereafter, the process proceeds to step Q10 to execute an image reading process. In this example, when the document 30 reverses the roller 43 in a U shape, the image sensor 58 reads the surface of the document 30. At this time, the image sensor 58 reads the light information of the R color, the G color, and the B color at the same time at different positions in the sub-scanning direction of the document 30 irradiated with light from the light source 53. The image reading signal Sout is output from the image sensor 58 to the control unit 35 '(ADF mode).

  Similarly to the platen mode, the control unit 35 ′ inputs the image reading signal Sout from the image sensor 58, and the image reading signal Sout is A / D processed by the analog signal processing units 31 R, 31 G, and 31 B of the RGB color channels. Convert. Even in the ADF mode, the inter-line delay is corrected for the RGB color three-channel image read data Dr, Dg, and Db output from the RGB color channel analog signal processing units 31R, 31G, and 31B. The image read data Dr, Dg, Db are encoded and compressed by the memory access control units 33R, 33G, 33B, etc., and stored in the image memory 36 in the same manner as in the platen mode. The image reading data Din is stored in units of one page, and an end of flag (EOF) is added to the image reading data Din of the page.

  Then, the process proceeds to step Q10 to execute image forming processing. At this time, the memory access control units 33R, 33G, 33B, etc. read the image reading data Dr, Dg, Db of the RGB color three channels from the image memory 36 in the same manner as in the platen mode, and the image reading data Dr, Dg, Decrypt and decompress Db. The decompressed image read data Dr, Dg, and Db are transferred to the color conversion processing unit 38 under the control of the memory access control units 33R, 33G, and 33B.

  The color conversion processing unit 38 converts the RGB color image read data Dr, Dg, Db read from the image memory 36 into YMCK color image data Dy, Dm, Dc, Dk based on the image processing control signal S2. Color conversion is made. The color-converted image data Dy, Dm, Dc, and Dk are output to the timing controllers 39Y, 39M, 39C, and 39K.

  At this time, the timing control units 39Y, 39M, 39C, and 39K receive the image data Dy, Dm, Dc, and Dk from the color conversion processing unit 38 based on the timing control signal S3. These image data Dy, Dm, Dc, Dk are subjected to PWM γ correction processing by the respective timing control units 39Y, 39M, 39C, 39K, and then subjected to frequency conversion processing.

  In addition, in order to align the timings of the laser beams for the respective colors, index signals relating to the laser beams for the respective colors are detected based on the image data Dy, Dm, Dc, and Dk, and index synchronization detection processing is performed. Further, in each of the timing controllers 39Y, 39M, 39C, 39K, a predetermined pulse signal is subjected to PWM (pulse width modulation) processing based on the image data Dy, Dm, Dc, Dk, and the laser drive signals Sy, Sm, Sc and Sk are generated.

  These laser drive signals Sy, Sm, Sc, Sk are output to the image forming means 60 together with the image formation control signal S4. In the same way as in the platen mode, the image forming means 60 operates to input a laser drive signal Sy, Sm, Sc, Sk and an image formation control signal S4 to form a color image on a predetermined paper P (step). Q7).

  Thereafter, the process proceeds to step Q12, and the MPU 15 determines whether or not the original 30 is the last page based on the detection of the paper detection signal. If the original 30 is not the last page, that is, if the original 30 remains on the original placement portion 41, the paper detection signal indicates “paper present”, so the process returns to step Q10 to perform the above-described image forming process. It is made to repeat. If the original 30 is the last page, the process proceeds to step Q13 after completing the image forming process. Note that the number of formed images (number of printed sheets) is counted by a counter (not shown).

  If the stop button is pressed in steps Q4 and Q8 described above, the process proceeds to step Q13, and the MPU 15 makes an end determination regarding the image forming process. For example, the power-off information is detected and the image forming process is terminated. If power-off information is not detected, the process returns to step Q1 to wait for a copy request. Thereafter, the above-described processing is repeated.

  As described above, according to the image forming apparatus as the second embodiment of the present invention, when the color image formed on an arbitrary document 30 is read and the color image is formed, the scanner 100 according to the present invention is configured. Applied. That is, the scanner 100 reads a color image formed on the document 30. The image forming units 10Y, 10M, 10C, and 10K are configured to form color images based on the image data Dy, Dm, Dc, and Dk obtained by reading with the scanner 100. Accordingly, it is possible to reduce variations in image resolution among the three colors of R, G, and B. Thereby, even when (magnification Z) × (sensor line interval) has a value below the decimal point, it is possible to form a high-quality image that is not colored with black horizontal thin lines or the like.

  Further, regarding the image forming means 60, image forming units 10Y, 10M, 10C, and 10K that form toner images of Y color, M color, C color, and BK color on the photosensitive drums 1Y, 1M, 1C, and 1K, and these The case of having the image transfer belt 6 for transferring the toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1K for the respective colors has been described. However, the present invention is not limited to this, and the present invention is limited to one transfer. The present invention can also be applied to a color copying machine that forms a color image on transfer paper by superimposing colors on a material conveying belt.

  The present invention is very suitable when applied to a tandem type color printer, a color copying machine, a color facsimile machine, a multi-function machine thereof, or the like that reads a document including a color image in a black and white document to form a color image.

1 is a conceptual diagram illustrating a configuration example of a color scanner 100 as a first embodiment of the present invention. It is a conceptual diagram which shows the structural example of the image sensor 58 for 3 line colors. 2 is a block diagram illustrating a configuration example of a control system of the color scanner 100. FIG. It is a block diagram which shows the example of internal structures, such as the timing correction part 34G for G color channels. It is a figure which shows the example of an expansion of the definition area of the interpolation coefficient k. A and B are diagrams showing an example of the relationship between the offset amount α and the timing delay correction amounts F (r), F (g), and F (b). It is a figure which shows the correction example (the 1) of the delay between lines in the linear interpolation circuit 70 at the time of Z = 87.5% and (alpha) = 0.25. It is a figure which shows the correction example (the 2) of the delay between lines in the linear interpolation circuit 70 at the time of Z = 87.5% and (alpha) = 0.25. 3 is a flowchart illustrating an example of image reading in the color scanner 100. It is a conceptual diagram which shows the structural example of the color copying machine 200 as a 2nd Example which concerns on this invention. 2 is a block diagram illustrating a configuration example of a control system of a color copying machine 200. FIG. 3 is a flowchart illustrating an example of image formation in the color copying machine 200. It is a figure which shows the example of correction | amendment of the image reading data Dr, Dg, Db by the image sensor 58 which concerns on a prior art example. It is a figure which shows the linear interpolation example (the 1) of the image reading data Dr, Dg, Db at the time of variable magnification decimal point setting. It is a figure which shows the linear interpolation example (the 2) of the image reading data Dr, Dg, Db at the time of variable magnification decimal point setting.

Explanation of symbols

1Y, 1M, 1C, 1K Photosensitive drum (image forming body)
2Y, 2M, 2C, 2K charging means (image forming means)
3Y, 3M, 3C, 3K image writing unit (exposure means; image forming means)
4Y, 4M, 4C, 4K developing device (image forming means)
6 Intermediate transfer member (image forming member)
10Y, 10M, 10C, 10K Image forming unit (image forming means)
11 Scanner unit 11a Scanner body 14 Operation unit (operation panel)
15 MPU (control means)
17 Fixing device 18 Display (operation panel)
19 Communication means 20 Paper feed means 34 Correction means 34R, 34G, 34B Timing correction section (correction means)
38 color conversion processing unit 40 Automatic document feeder (ADF)
48 Operation panel 60 Image forming means 61 Delay circuit (correction means)
70 Linear interpolation circuit (correction means)
71 Front line buffer (correction means)
72 1st multiplier (correction means)
73 First register (correction means)
74 Second multiplier (correction means)
75 Second register (correction means)
76 Adder (correction means)
100 color scanner 200 color copier 201 copier body

Claims (15)

An apparatus for reading a color image formed on an arbitrary sheet,
A light source for irradiating the sheet with light;
Line-shaped reading sensors for detecting red, green, and blue light configured by arranging a plurality of light receiving element arrays in the main scanning direction are arranged at a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction. And a one-dimensional image sensor that simultaneously reads light information of each color by dividing pixels at different positions in the sub-scanning direction of the sheet irradiated with light by the light source;
Moving means for relatively moving the image sensor or the sheet in the sub-scanning direction;
With respect to the optical information obtained by reading by the image sensor from the sheet moved by the moving unit, the positional deviation in the sub-scanning direction between the reading sensors for detecting each color light is corrected and the positional deviation is corrected. An image reading apparatus comprising: correction means for adjusting the image resolution between the respective color components by adjusting a linear interpolation ratio between the preceding and following reading lines with respect to the optical information. The correction means includes
A delay circuit that corrects a deviation of an integer line between the red, green, and blue reading sensors;
The image reading apparatus according to claim 1, further comprising a linear interpolation circuit that corrects a shift of a decimal line between the reading sensors of each color corrected by the delay circuit. The linear interpolation circuit includes:
A first multiplier for multiplying an output of the delay circuit by an interpolation coefficient k;
A previous line buffer for delaying the output of the delay circuit by one line;
A second multiplier for multiplying the output of the previous line buffer by the interpolation coefficient 1-k;
The image reading apparatus according to claim 2, further comprising an adder that adds outputs of the first and second multipliers. Setting means for setting a document reading magnification when reading the sheet;
Control means for controlling input / output of the correction means based on the document reading magnification set by the setting means,
The control means includes
The image reading apparatus according to claim 1, wherein an interpolation coefficient k corresponding to the document reading magnification is output to the correction unit. The control means includes
Set the offset amount according to the delay amount between the reading sensors for each color light detection,
The image reading apparatus according to claim 4, wherein a delay correction amount is generated by adding the set offset amount to a delay amount between the reading sensors. The control means includes
5. The correction means is controlled so that delay correction amounts of linear interpolation of two colors of red, green, and blue are equal, or the delay correction amounts are in a complement relationship. Image reading device. The control means includes
The image reading apparatus according to claim 4, wherein the delay correction amount is set so that an absolute value of a difference in interpolation coefficients among the red, green, and blue colors is minimized. The control means includes
The image reading apparatus according to claim 4, wherein the offset amount and the delay correction amount are set according to a sub-scanning speed corresponding to the document reading magnification. A method for reading a color image formed on an arbitrary sheet,
Line-shaped reading sensors for detecting red, green, and blue light configured by arranging a plurality of light receiving element arrays in the main scanning direction are arranged at a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction. And using a one-dimensional image sensor that simultaneously reads light information of each color by dividing pixels at different positions in the sub-scanning direction,
While relatively moving the sheet or image sensor in the sub-scanning direction, reading the light information that irradiates the sheet with light and returns from the sheet,
In addition to correcting the positional deviation in the sub-scanning direction between the reading sensors for detecting each color light with respect to the read light information, the ratio of linear interpolation between the reading sensors before and after is adjusted to adjust between the color components. An image reading method comprising correcting image resolution.   The image reading method according to claim 9, wherein a ratio of linear interpolation between the front and rear reading sensors is adjusted according to a document reading magnification for reading the sheet. When correcting the image resolution between the color components,
Set the offset amount according to the delay amount between the reading sensors for each color light detection,
The image reading method according to claim 9, wherein a delay correction amount is generated by adding the set offset amount to a delay amount between the reading sensors. When correcting the image resolution between the color components,
10. The image reading method according to claim 9, wherein the delay correction amounts of linear interpolation of two colors of red, green, and blue are set to be equal or the delay correction amounts are set in a complement relationship. When correcting the image resolution between the color components,
The image reading method according to claim 9, wherein the delay correction amount is set so that an absolute value of a difference in interpolation coefficients among the red, green, and blue colors is minimized. When correcting the image resolution between the color components,
The image reading method according to claim 9, wherein the offset amount and the delay correction amount are set according to a sub-scanning speed corresponding to the document reading magnification. An apparatus for reading a color image formed on an arbitrary sheet to form a color image,
An image reading device for reading a color image formed on the sheet;
Image forming means for forming a color image based on color image information obtained by reading with the image reading device;
The image reading device includes:
A light source for irradiating the sheet with light;
Line-shaped reading sensors for detecting red, green, and blue light configured by arranging a plurality of light receiving element arrays in the main scanning direction are arranged at a predetermined distance in the sub-scanning direction orthogonal to the main scanning direction. And a one-dimensional image sensor that simultaneously reads light information of each color by dividing pixels at different positions in the sub-scanning direction of the sheet irradiated with light by the light source;
Moving means for relatively moving the image sensor or the sheet in the sub-scanning direction;
With respect to the optical information obtained by reading by the image sensor from the sheet moved by the moving means, the positional deviation in the sub-scanning direction between the reading sensors for detecting each color light is corrected and the positional deviation is corrected. An image forming apparatus comprising: a correcting unit that adjusts a ratio of linear interpolation between the reading sensors before and after the optical information to correct an image resolution between the respective color components.

Images