JP3848010B2 - Image reading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus applied to an image scanner apparatus, a facsimile apparatus, a digital copying machine, and the like, and more particularly to an image reading apparatus capable of reading both monochrome and color originals.
[0002]
[Prior art]
In an image reading apparatus, the level of each pixel of image data for one line obtained by reading a document having a uniform density should ideally be the same, but for each light receiving element of the image sensor. The level of each pixel of the obtained image data is not the same and varies due to unevenness of light reception sensitivity, non-uniformity of irradiation light from the light source for document illumination, non-uniformity of the optical system, etc. is there.
[0003]
Therefore, it is necessary to perform shading correction in which an image serving as a reference such as a white reference plate is read and stored as shading data, and the level of image data at the time of actual document reading is normalized by the shading data.
[0004]
[Problems to be solved by the invention]
In an image reading apparatus capable of reading both a monochrome document and a color document, monochrome image data obtained by reading the monochrome document and color image data for each primary color component such as RGB obtained by reading the color document Therefore, shading correction for monochrome images is required when reading a monochrome document, and shading data for color images for each primary color component is required when reading a color document.
[0005]
Therefore, in an image reading apparatus capable of reading both a monochrome document and a color document, it is necessary to store both shading data for monochrome images and shading data for color images, and a dedicated memory for storing each shading data However, there is a problem that the required memory capacity becomes large and the cost becomes high.
[0006]
The present invention has been made in view of such circumstances, and provides an image reading apparatus capable of minimizing the memory capacity required for storing the shading data for monochrome images and the shading data for color images of each primary color component. For the purpose.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, an image reading apparatus according to claim 1 is provided.An image reading apparatus capable of reading monochrome and color originals, and storing one line of shading data for either one of monochrome shading data for monochrome image data or shading data for each color component of color image data A storage area for storing all of the shading data for each color component of color image data different from the shading data stored in the first storage means and the monochrome image processing work area, or the shading data stored in the first storage means. Second storage means, and shading correction means for correcting the distortion of monochrome and color image data and normalizing the image data. In the case of color reading, the first storage means and the first storage means 2 For each color component of color image data from a plurality of different storage means Referring to E over loading data, and wherein the normalizing by shading correcting the color image data.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0016]
First, FIG. 1 shows a block configuration of an image reading apparatus 1 according to an embodiment of the present invention.
[0017]
In the figure, an image reading apparatus 1 reads a document image illuminated by a light source that is turned on or off by a light source driving unit 2 according to an instruction from a control unit 14 by a color sensor unit 6. The read document is moved relative to the color sensor unit 6 on the reading surface by the document transport unit 5, and the color sensor unit 6 outputs an image signal in units of lines while reading the document image. In addition, prior to the start of document reading, the color sensor unit 6 reads the white reference plate 4 illuminated by the light source 3 as necessary, and outputs an image signal as white level shading data.
[0018]
The color sensor unit 6 includes a color CCD image sensor, a color CIS (contact image) image sensor, and the like, and generates an analog image signal corresponding to the amount of light received from the reading surface. The analog image signal is a monochrome (BW) image signal at the time of reading in the monochrome mode, and is an image signal of each color component of RGB at the time of reading in the color mode. The A / D conversion unit 7 converts monochrome and color analog signals input from the color sensor unit 6 into monochrome and color multivalued image data. The shading correction unit 8 normalizes the monochrome and color image data from the A / D conversion unit 7 by correcting the distortion due to the difference in irradiation light between each pixel of the reading line, light receiving element sensitivity, and the like for each monochrome and color. To do. The first storage unit 9 is for storing shading data referred to for the shading correction processing in the shading correction unit 8. The monochrome image processing unit 11 performs processing such as threshold processing, dither processing, and error diffusion processing on the monochrome image data corrected by the shading correction unit 8 to generate N-value monochrome image data. The second storage unit 10 is used as a work area for monochrome image processing in the monochrome image processing unit 11, and stores shading data for color images as needed to be referred to the shading correction unit 8. Is.
[0019]
The color image data subjected to the shading correction for each color component of RGB by the shading correction unit 8 is output to the output unit 12. The monochrome image data corrected by the shading correction unit 8 and processed by the monochrome image processing unit 11 is output to the output unit 12.
[0020]
The output unit 12 differs depending on the device to which the image reading device 1 is applied. For example, in the case of an image scanner device, the output unit 12 is an external interface with other devices such as a personal computer, and may be a digital copying machine. For example, it is an internal interface to the plotter unit, and if it is a facsimile machine, it is a communication unit, and the present invention is not limited by the use of the image data output from the image reading apparatus 1.
[0021]
The third storage unit 13 serves as a work area for the control unit 14. The control unit 14 is a microcomputer that controls each unit of the apparatus. The operation display unit 15 is provided with various keys for accepting operation inputs from the user, and includes a liquid crystal display for displaying the operation state of the apparatus and a message to the user. The system bus 16 is a signal line through which each unit exchanges data.
[0022]
Here, since the shading correction unit 8 and the monochrome image processing unit 11 need to perform high-speed processing in real time when reading a document image, the shading correction unit 8 and the monochrome image processing unit 11 are generally configured as a dedicated image processing ASIC. The first storage unit 9 and the second storage unit 10 that are accessed at high speed by the processing unit 11 are also configured in the same ASIC. On the other hand, the third storage unit 13 is used as a work area for the control unit 14 to control each unit of the apparatus, and is used for storing control data and temporarily storing processed image data. Therefore, compared with the first storage unit 9 and the second storage unit 10, high-speed operation is not required, but it is required to have a relatively large capacity, so that it is configured by a general-purpose large-capacity DRAM or SRAM. ing.
[0023]
For comparison with the present invention, a conventional usage pattern of the first storage unit 9, the second storage unit 10, and the third storage unit 13 is shown in FIG.
[0024]
In the figure, conventionally, the first storage unit 9 individually stores BW shading data for BW image data and R, G, and B shading data for RGB primary color components of color image data, A memory capacity for four lines of image data was required. Further, the second storage unit 10 was used only as a work area for N-value conversion processing in the monochrome image processing unit 11. The third storage unit 13 is partially used as a control work area of the control unit 14, but there is an unused area.
[0025]
The BW shading data is referred to by the shading correction unit 8 only when reading in the monochrome mode, and the second storage unit 10 is used by the monochrome image processing unit 11 only when reading in the monochrome mode. On the other hand, the R, G, and B shading data are referred to by the shading correction unit 8 only when reading in the color mode, and when reading in the color mode, the monochrome image processing unit 11 uses the second storage unit. 10 is not used.
[0026]
In view of this, the image reading apparatus 1 according to the present embodiment performs image reading processing according to the first, second, or third embodiment described below.
[0027]
First, an image reading processing procedure according to the first embodiment will be described with reference to FIG.
[0028]
In the figure, the control unit 14 first has a current reading mode set by a reading mode setting key (not shown) of the operation display unit 15 being either a “monochrome” reading mode or a “color” reading mode. Is determined (decision 101).
[0029]
If it is determined in the “monochrome” mode in the determination 101, the light source driving unit 2 is controlled to turn on (turn on) the light source 3 (processing 102), and the monochrome image signal obtained by reading the white reference plate with the color sensor unit 6. Multi-value BW shading data obtained by A / D conversion by the A / D conversion unit 7 is stored in the first storage unit 9 (process 103).
[0030]
In this manner, BW shading data is collected prior to the start of monochrome document reading, and the BW image signal is output in units of reading lines by the color sensor unit 6 while the read document is conveyed by the document conveying unit 5 (process 104). ) A / D conversion is performed by the A / D conversion unit 7 to obtain multi-valued BW image data (processing 105), and the shading correction unit 8 stores the BW image data in the first storage unit 9 by processing 103. The stored BW shading data is referred to and normalized by shading correction (process 106), and the BW image data after the shading correction is processed by the monochrome image processing unit 11 using the second storage unit 10 as a work area. Processing (processing 107), and processing output from the output unit 12 (processing 108) is repeated until the reading of the document is completed (decision 109). No loop), the reading of the document is completed (Yes in decision 109), the light source by controlling the light source driver 2 to OFF (unlit) (processing 110), and ends the reading process.
[0031]
On the other hand, when the color mode is determined in the determination 101, the light source driving unit 2 is controlled to turn on (turn on) the light source 3 (processing 111), and the RGB obtained by reading the white reference plate with the color sensor unit 6 is obtained. The G shading data of the multivalued RGB shading data obtained by A / D converting the color image signals of the respective color components is stored in the first storage unit 9 (processing 112). Further, the RB shading data of the RGB shading data is stored in the second storage unit 10 (process 113).
[0032]
In this way, RGB shading data is collected prior to the start of color document reading, and an RGB image signal is output for each reading line by the color sensor unit 6 while the read document is conveyed by the document conveying unit 5 (processing 114). ), A / D conversion is performed by the A / D conversion unit 7 to obtain multivalued RGB image data (processing 115), and the shading correction unit 8 stores the RGB image data in the first storage unit 9 through processing 112. The stored G shading data and the RB shading data stored in the second storage unit 10 by the processing 113 are referred to and normalized by shading correction (processing 116), and the RGB image data after the shading correction is output. The process output from the unit 12 (process 117) is repeated until the reading of the document is completed (No loop of decision 118). ), The reading of the document is completed (Yes in decision 118), the light source by controlling the light source driver 2 to OFF (unlit) (processing 110), and ends the reading process.
[0033]
FIG. 4 shows how the first storage unit 9, the second storage unit 10, and the third storage unit 13 are used in the image processing procedure according to the first embodiment shown in FIG.
[0034]
In FIG. 4, the third storage unit 13 is the same as the conventional usage pattern shown in FIG. However, the first storage unit 9 has only a memory capacity for one line of image data, and is used for storing BW shading data during monochrome reading and used for storing G shading data during color reading. Is done. The second storage unit 10 is used as a work area for N-value conversion processing in the monochrome image processing unit 11 during monochrome reading, as in the conventional usage mode shown in FIG. It is effectively used for storing R shading data and B shading data.
[0035]
Thereby, shading correction at the time of reading each of monochrome and color can be performed while minimizing the memory capacity of the first storage unit 9 and the second storage unit 10 that require high-speed operation for high-speed access. become able to.
[0036]
Next, an image reading process procedure according to the second embodiment will be described with reference to FIGS. 5, 6, 7, and 8.
[0037]
In FIG. 5, the control unit 14 first sets the current reading mode set by a reading mode setting key (not shown) of the operation display unit 15 to “shading data” reading mode, “monochrome” reading mode, or “color”. It is determined which one of the reading modes is selected (determination 201).
[0038]
If it is determined in the determination 201 that the “shading data” reading mode is set, a shading data reading process is performed (process 202). If it is determined in the determination 201 that the “monochrome” reading mode is set, monochrome document reading processing is performed (processing 203). If it is determined in the determination 201 that the “color” reading mode is set, a color document reading process is performed (process 204).
[0039]
FIG. 6 shows a specific procedure of the shading data reading process according to the second embodiment in the process 202 of FIG.
[0040]
In FIG. 6, the control unit 14 controls the light source driving unit 2 to turn on (turn on) the light source 3 (processing 301), and read a monochrome image signal obtained by reading the white reference plate with the color sensor unit 6 as A / The multivalued BW shading data obtained by A / D conversion by the D conversion unit 7 is stored in the third storage unit 13 (processing 302). Further, the multivalued RGB shading data obtained by A / D converting the color image signals of the RGB color components obtained by reading the white reference plate with the color sensor unit 6 by the A / D conversion unit 7 is the third. It memorize | stores in the memory | storage part 13 (process 303). Then, the light source driving unit 2 is controlled to turn off the light source (process 304), and the shading data reading process ends.
[0041]
FIG. 7 shows a specific procedure of the monochrome document reading process according to the second embodiment in the process 203 of FIG.
[0042]
In FIG. 7, the control unit 14 controls the light source driving unit 2 to turn on (turn on) the light source 3 (processing 301), read BW shading data from the third storage unit 13, and store it in the first storage unit 9 ( Process 402).
[0043]
In this manner, BW shading data is stored in the first storage unit 9 prior to the start of monochrome document reading, and then the BW image signal is read in units of reading lines by the color sensor unit 6 while the read document is conveyed by the document conveying unit 5. (Processing 403), A / D conversion is performed by the A / D conversion unit 7 to obtain multi-valued BW image data (processing 404), and the shading correction unit 8 converts the BW image data into processing 402. The BW shading data stored in the first storage unit 9 is referred to and normalized by shading correction (process 405), and the BW image data after the shading correction is processed by the monochrome image processing unit 11 in the second storage unit 10 as a work area. N value conversion processing (processing 406), and output processing from the output unit 12 (processing 407) is repeated until the reading of the document is completed. (No loop decision 408), the reading of the document is completed (Yes in decision 408), the light source by controlling the light source driver 2 to OFF (unlit) (processing 409), and ends the reading process.
[0044]
FIG. 8 shows a specific procedure of the color document reading process according to the second embodiment in the process 204 of FIG.
[0045]
In FIG. 8, the control unit 14 controls the light source driving unit 2 to turn on (turn on) the light source 3 (processing 501), read G shading data from the third storage unit 13, and store it in the first storage unit 9. (Process 502), RB shading data is read from the third storage unit 13 and stored in the second storage unit 10 (Process 503).
[0046]
In this manner, prior to the start of color document reading, RGB shading data is stored in the first storage unit 9 and the second storage unit 10, respectively, and the read document is conveyed by the document conveying unit 5 by the color sensor unit 6. RGB image signals are output in units of reading lines (process 504), A / D conversion is performed by the A / D converter 7 to obtain multi-value RGB image data (process 505), and the RGB image data is subjected to shading correction. The unit 8 refers to the G shading data stored in the first storage unit 9 by the process 502 and the RB shading data stored in the second storage unit 10 by the process 503 and performs shading correction and normalization (process 506). ), A process of outputting the shading-corrected RGB image data from the output unit 12 (process 507), and the reading of the document is finished. Until the reading is finished (No loop of judgment 508), when the reading of the document is finished (Yes of judgment 508), the light source driving unit 2 is controlled to turn off the light source (process 509), and the reading process is finished. .
[0047]
FIG. 9 shows how the first storage unit 9, the second storage unit 10, and the third storage unit 13 are used in the image processing procedure according to the second embodiment shown in FIGS. 5, 6, 7, and 8. .
[0048]
In FIG. 9, the first storage unit 9 has only a memory capacity for one line of image data, and is used for storing BW shading data during monochrome reading, and for storing G shading data during color reading. Used for. The second storage unit 10 is used as a work area for N-value conversion processing in the monochrome image processing unit 11 during monochrome reading, as in the conventional usage mode shown in FIG. It is effectively used for storing R shading data and B shading data.
[0049]
The BW shading data stored in the first storage unit 9 during monochrome reading is lost by overwriting the G shading data during color reading, and the G shading data stored in the first storage unit 9 during color reading is lost during monochrome reading. BW shading data is overwritten and lost. Also, the RB shading data stored in the second storage unit 10 during color reading is lost due to the use of the second storage unit 10 by the monochrome image processing 11 during monochrome reading. Therefore, as it is, G shading data and RGB shading data must be collected again each time a monochrome document or color document is read. However, previously collected G shading data and RGB shading data are not stored in the third storage unit. Since it is stored in the use area and restored to the first storage unit 9 or the second storage unit 10 when necessary, the shading data is collected once at the time of installation of the device and the like. If stored in the storage unit 13, it is not necessary to recollect shading data when the document reading mode is switched from monochrome to color or from color to monochrome.
[0050]
Next, a third embodiment will be described. In the third embodiment, the image reading apparatus 1 shares a monochrome (BW) image signal and a G image signal among the color image signals of RGB color components. All the RGB image signals output from the image sensor 6 are valid, but only the G image signal out of the RGB image signals output from the color sensor unit 6 is valid as the BW image signal and the RB image signal is invalid during monochrome reading. It becomes.
[0051]
An image reading processing procedure according to the third embodiment will be described with reference to FIGS. 5, 10, 11, and 12.
[0052]
Since the image reading processing procedure shown in FIG. 5 has already been described in the description of the second embodiment, a redundant description will be omitted.
[0053]
FIG. 10 shows a specific procedure of the shading data reading process according to the third embodiment in the process 202 of FIG.
[0054]
In FIG. 10, the control unit 14 controls the light source driving unit 2 to turn on (turn on) the light source 3 (processing 601), and read the white reference plate with the color sensor unit 6 to obtain a BW (G) image signal. Multi-value BW / G shading data obtained by A / D conversion by the A / D conversion unit 7 is stored in the first storage unit 9 (process 602). Further, the multi-value RB shading data obtained by A / D converting the color image signal of each color component of RB obtained by reading the white reference plate with the color sensor unit 6 is the third. It memorize | stores in the memory | storage part 13 (process 303). Then, the light source driving unit 2 is controlled to turn off the light source (process 604), and the shading data reading process ends.
[0055]
FIG. 11 shows a specific procedure of the monochrome document reading process according to the third embodiment in the process 203 of FIG.
[0056]
In FIG. 11, the control unit 14 controls the light source driving unit 2 to turn on (turn on) the light source 3 (processing 701). Note that the BW / G shading data necessary for reading a monochrome document has already been stored in the first storage unit 9 by the processing 602 in FIG.
[0057]
As described above, prior to the start of monochrome document reading, the BW shading data is stored in the first storage unit 9 and the BW image signal is read in units of reading lines by the color sensor unit 6 while the read document is conveyed by the document conveying unit 5. (Processing 702), A / D conversion is performed by the A / D converter 7 to obtain multi-valued BW image data (Process 703), and the shading correction unit 8 uses the first storage unit The BW shading data stored in FIG. 9 is referred to and normalized by shading correction (process 704), and the monochrome image processing unit 11 uses the second storage unit 10 as a work area for the BW image data after the shading correction. N-value conversion processing (processing 705), processing output from the output unit 12 (processing 706), is repeated until the reading of the document is completed (N of determination 707) Loop), the reading of the document is completed (Yes in decision 707), the light source by controlling the light source driver 2 to OFF (unlit) (processing 708), and ends the reading process.
[0058]
FIG. 12 shows a specific procedure of the color document reading process according to the third embodiment in the process 204 of FIG.
[0059]
In FIG. 12, the control unit 14 controls the light source driving unit 2 to turn on (turn on) the light source 3 (process 801), read out RB shading data from the third storage unit 13, and store it in the second storage unit 10 ( Process 802). The G / BW shading data is already stored in the first storage unit 9 by the process 602 in FIG.
[0060]
In this manner, prior to the start of color document reading, RGB shading data is stored in the first storage unit 9 and the second storage unit 10, respectively, and the read document is conveyed by the document conveying unit 5 by the color sensor unit 6. RGB image signals are output in units of reading lines (process 803), A / D conversion is performed by the A / D converter 7 to obtain multi-value RGB image data (process 804), and the RGB image data is subjected to shading correction. The unit 8 refers to the G / BW shading data stored in the first storage unit 9 and the RB shading data stored in the second storage unit 10 by the processing 802 and normalizes the shading correction (processing 805). A process for outputting the shading-corrected RGB image data from the output unit 12 (process 806) until the reading of the document is completed. Ri returns (No loop decision 807), the reading of the document is completed (Yes in decision 807), the light source by controlling the light source driver 2 to OFF (unlit) (processing 808), and ends the reading process.
[0061]
FIG. 13 shows how the first storage unit 9, the second storage unit 10, and the third storage unit 13 are used in the image processing procedure according to the third embodiment shown in FIGS. 5, 10, 11, and 12. .
[0062]
In FIG. 13, the first storage unit 9 has a memory capacity corresponding to one line of image data, and is used for storing BW / G shading data shared during monochrome reading and color reading. The second storage unit 10 is used as a work area for N-value conversion processing in the monochrome image processing unit 11 during monochrome reading, as in the conventional usage mode shown in FIG. It is effectively used for storing R shading data and B shading data.
[0063]
Since the shading data stored in the first storage unit 9 is shared as BW shading data and G shading data, the BW shading data stored in the first storage unit 9 during monochrome reading is overwritten by the G shading data during color reading. Therefore, the G shading data stored in the first storage unit 9 during color reading is not overwritten with the BW shading data during monochrome reading. Therefore, the BW / G shading data is not erased from the first storage unit 9 even if it is not saved in the third storage unit 13. If a backup circuit is added to the first storage unit 9, the BW / G shading data stored in the first storage unit 9 can be retained even when the apparatus power is shut off. Further, since the shading data to be saved in the third storage unit is only RB shading data, the shading data that needs to be saved / restored can be minimized.
[0064]
In the second and third embodiments, at least the backup area of the third storage unit 13 that saves and stores BW shading data and RGB shading data is preferably constituted by a memory that can be backed up. As a result, BW shading data and RGB shading data can be held even when the apparatus power is cut off, and it is not necessary to recollect BW shading data and RGB shading data every time the apparatus is turned on. As a configuration of the backup area of the third storage unit 13, an electrically rewritable read-only memory, that is, a so-called flash ROM (FROM) can be used. A random access memory (RAM) backed up by a battery can also be used.
[0065]
In the embodiment described above, the case where the white level data obtained by reading the white reference plate illuminated by the light source 3 is used as the shading data has been described. However, the present invention is not limited thereto, and is illuminated by the light source 3. The same applies to the case where black level data obtained by reading a black reference plate (not shown) is used as shading data, and shading dark bell data obtained by reading an image with the light source 3 turned off. The same applies to the case of data, and it is possible to minimize the memory capacity for storing shading data for shading correction processing.
[0066]
【The invention's effect】
According to the first aspect of the present invention, each of monochrome and color reading is performed while minimizing the memory capacity of the first storage unit and the second storage unit that require high-speed operation for high-speed access. The effect that the shading correction at the time can be performed is obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image reading apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a conventional usage pattern of a first storage unit, a second storage unit, and a third storage unit.
FIG. 3 is a flowchart showing a reading processing procedure according to the first embodiment in the image reading apparatus according to the embodiment of the present invention;
FIG. 4 is a diagram illustrating a usage pattern of the first storage unit, the second storage unit, and the third storage unit in the first embodiment.
FIG. 5 is a flowchart showing a reading processing procedure according to second and third embodiments in the image reading apparatus according to the embodiment of the present invention;
FIG. 6 is a flowchart showing a specific procedure of a shading data reading process in a reading process procedure according to the second embodiment.
FIG. 7 is a flowchart showing a specific procedure of monochrome document reading processing in the reading processing procedure according to the second embodiment.
FIG. 8 is a flowchart showing a specific procedure of color document reading processing in the reading processing procedure according to the second embodiment.
FIG. 9 is a diagram illustrating a usage pattern in the second embodiment of the first storage unit, the second storage unit, and the third storage unit.
FIG. 10 is a flowchart showing a specific procedure of a shading data reading process in a reading process procedure according to the third embodiment.
FIG. 11 is a flowchart illustrating a specific procedure of a monochrome document reading process in a reading process procedure according to the third embodiment.
FIG. 12 is a flowchart showing a specific procedure of color document reading processing in the reading processing procedure according to the third embodiment.
FIG. 13 is a diagram illustrating a usage pattern in the third embodiment of the first storage unit, the second storage unit, and the third storage unit.
[Explanation of symbols]
1 Image reader
2 Light source drive
3 Light source
4 White reference plate
5 Document transport section
6 Color sensor
7 A / D converter
8 Shading correction part
9 First storage unit
10 Second storage unit
11 Monochrome image processing unit
12 Output section
13 Third storage unit
14 Control unit
15 Operation display
16 System bus

Claims (1)

  An image reading apparatus capable of reading monochrome and color originals,
  A first storage unit having a capacity of one line of image data for storing one-color component shading data of either monochrome image data for monochrome image data or shading data for each color component of color image data;
  A second storage means serving as a storage area for storing all of the shading data for each color component of color image data different from the work area for monochrome image processing or the shading data stored in the first storage means;
  Shading correction means for correcting distortion of monochrome and color image data and normalizing the image data,
  In the case of color reading, each color component shading data of color image data is referred to from a plurality of different storage means of the first storage means and the second storage means, and the color image data is normalized by shading correction.
  An image reading apparatus.

Images