JP5857485B2 - Image processing apparatus and control method thereof - Google Patents

Description

  The present invention provides an image processing unit that includes a document reading unit that reads a reflected light image of a document illuminated by an illumination light source and inputs image data of the document, and an image processing unit that performs predetermined processing on the document image data. The present invention relates to an apparatus and a control method thereof.

  In this type of image processing apparatus, in order to adjust the background of the document to paper white at the time of image output, the density value equal to or lower than the value set as the background skip amount is converted to 0 for the document image data. The “skip” process is often performed by image processing means.

  Now, when reading a reflected light image of a document, there is a problem that an image on the back side of the document (the surface opposite to the illuminated reading surface), particularly high-density characters, is seen through and the show-through image is read. . When the density value of the read show-through image is smaller than the background skip amount of the background skip processing, the show-through image is removed by the background skip processing. However, when the density value of the show-through image is larger than the background skip amount, the show-through image is not removed.

  The density of the show-through image varies depending on the transmittance or the paper thickness of the document, but even if the transmittance or the paper thickness of the document is the same, it also varies depending on the amount of light of the document illumination light source. The removal effect is also affected by the light source quantity. This will be described with reference to FIG.

  FIG. 11 is a schematic diagram showing the density of characters (front characters) on the reading surface and characters on the back surface (show-through characters) of the document read by the document reading means in relation to the background skip amount. The difference between (a) and (b) in FIG. 11 is that the amount of light from the illumination light source is greater in (a) than in (b), and the amount of document and background removal is the same.

  When the amount of light from the light source is large (a), the density of the read-through show character exceeds the background skip amount. Therefore, the show-through character cannot be removed by the background removal process.

  On the other hand, in the case of (b) in which the light amount of the light source is reduced, the density of the read-through show character is lower than the background skip amount, so that the show-through character can be removed by the background skip processing. That is, for this document, it is effective to reduce the amount of light source to remove show-through.

  However, when the amount of light source is reduced as shown in (b), the density of images such as table characters read from the reading surface of the document also decreases as a whole, so that the reading surface includes a pattern having highlight information. In the case of a manuscript, there is a problem that information on highlights to be lost increases due to the background skipping process, and the highlighted part of the design becomes splattered and gradation is deteriorated.

  Note that, in an image reading apparatus that reads a reflected light image of a document, a technique for measuring the transmittance and reflectance of a document and changing the amount of light of a document illumination light source according to the measured transmittance and reflectance is disclosed in Patent Document 1. It is described in.

  An object of the present invention is to provide a document reading unit that reads a reflected light image of a document illuminated by an illumination light source and inputs document image data, and a background skip amount for the document image data input from the document reading unit. In an image processing apparatus including at least an image processing unit that performs background removal processing for converting a density value equal to or less than a set value to 0, highlighting of a pattern on a document accompanying the change in the light amount of the illumination light source as described above It is to be able to suppress the gradation deterioration of the part.

The present invention provides a document reading unit that reads a reflected light image of a document illuminated by an illumination light source and inputs document image data, and a background skip amount for the document image data input from the document reading unit. The image processing apparatus includes an image processing unit that performs at least a background removal process for converting a density value equal to or less than a density value to 0.
Light source light quantity control means for adjusting the light quantity of the illumination light source according to the transmittance of the original or the paper thickness;
Based on the edge amount of the original image data, and the document type determination means for the document to determine the constant whether the with highlight information,
When it is determined that the document has highlight information, when the light amount of the illumination light source is adjusted to a value different from the default value by the light source light amount control unit, the background skip amount is set to the default value. Different from the above, there is a background skip amount control means for adjusting to a value smaller than the default value of the background skip amount according to the transmittance or paper thickness of the original.

According to the image processing apparatus of the present invention, by adjusting the amount of light of the illumination light source according to the transmittance of the document or the paper thickness, it is possible to reliably remove the show-through characters such as the characters on the document. On the other hand, when the document to be read is a document type including a pattern having highlight information, when the light amount of the illumination light source is adjusted to a value different from the default value, the background skip amount is different from the default value. By adjusting to a value smaller than the default value of the background skip amount according to the transmittance or paper thickness of the document, omission of highlight information on the document is suppressed, and the gradation property of the highlight portion of the pattern is improved. Can keep.

It is the simplified block diagram explaining the functional structure of the image processing apparatus which concerns on one Embodiment of this invention. It is a graph which shows the example of the input-output characteristic of the printer (gamma) correction | amendment part which serves as a background removal processing means. 6 is a graph showing the relationship between the transmittance of a document and the paper thickness. It is a flowchart for demonstrating the whole operation | movement of an image processing apparatus, and light source light quantity / background skip amount control. It is a flowchart for demonstrating the example of a procedure in the case of making a user intervene in the necessity determination of a background removal amount change. It is a figure which shows an example of the screen which asks a user of the necessity of a background removal amount change. It is a flowchart for demonstrating the example of a procedure in the case of making a user intervene in the setting value determination of the amount of ground removal. It is a figure which shows an example of the screen displayed when making a user intervene in the setting value determination of the amount of background skipping. FIG. 5 is a schematic cross-sectional view for explaining a specific configuration example of a document reading unit. It is a schematic diagram which shows the specific example of the transmittance | permeability (or paper thickness) detection means. It is a schematic diagram which shows the relationship between increase / decrease in light source light quantity and show-through density.

  The image processing apparatus according to the present invention includes a light source light quantity control unit that adjusts the light quantity of a light source for illumination according to the transmittance or paper thickness of a document, and a light source when the document is a document type including a pattern having highlight information. When the light amount of the illumination light source is adjusted to a value different from the default value by the light amount control means, the background skip amount is adjusted to a value according to the transmittance of the document or the paper thickness, which is different from the default value. And a ground removal amount control means.

  According to this configuration, it is possible to surely remove the show-through characters such as the characters on the document by adjusting the light amount of the illumination light source according to the transmittance of the document or the paper thickness. On the other hand, if the document is of a document type that includes a pattern with highlight information, when the amount of light from the illumination light source is adjusted to a value different from the default value, the background skip amount differs from the default value. By adjusting to a value corresponding to the transmittance or the paper thickness, it is possible to suppress omission of highlight information on the original and to maintain a good gradation in the highlight portion of the pattern.

  The above will be described more specifically with reference to FIG. For example, it is assumed that the background skip amount shown in FIGS. 11A and 11B is the default value, and that the light source light amount in FIG. 11A is the default value.

  When the original is read with the light source light amount adjusted to the default value, if the transmittance of the document is larger than the assumed transmittance (or if the paper thickness is thinner than the assumed paper thickness), as shown in FIG. On the other hand, since the density value of the show-through character exceeds the default value of the background skip amount, the show-through cannot be removed.

  In such a case, as shown in (b), the light source light amount is a value corresponding to the transmittance of the document or the paper thickness so that the density value of the show-through character is equal to or less than the default value of the background skip amount. By adjusting to (a value smaller than the default value), it becomes possible to remove a show-through such as a back letter. However, since the image density such as table characters generally decreases due to a decrease in the amount of light from the light source, if the original contains a pattern with highlight information, the background skipping amount is left at the default value. There are many lacks of highlight information, and the gradation of the highlight portion of the symbol is deteriorated. According to the present invention, in such a case, the highlight information on the document is lost due to the background skip processing by adjusting the background skip amount to a value smaller than the default value according to the transmittance or the paper thickness of the document. It is possible to keep the gradation property of the highlight portion of the pattern good.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a simplified block diagram for explaining a functional configuration of an image processing apparatus according to an embodiment of the present invention.

  The image processing apparatus shown in FIG. 1 reads a reflected light image of a document illuminated by an illuminating light source and inputs a document reading unit 100 that is a document reading unit that inputs document image data, and is input from the document reading unit 100. An image processing unit 101 that is an image processing unit that performs predetermined processing including background removal processing on the original image data, and a printer unit 102 that is an image forming unit that prints out the image data processed by the image processing unit 101 A light source light amount / background skip amount control unit 104 that is a means for adjusting the light amount of the document illumination light source in the document reading unit 100 and the background skip amount of the background skip processing in the image processing unit 101; The operation unit 105, which is a means for specifying, and the system control unit 106, which is a means for controlling each of the above units, are configured.

  The image processing unit 101 converts a scanner linear γ signal from a linear reflectance RGB signal to a density linear RGB signal with respect to the original image data input from the original reading unit 100, and the converted RGB signal. A filter processing unit 111 that performs filter processing for edge enhancement, smoothing, and the like and cyan (C), magenta (M), yellow (Y), black ( K) a color conversion unit 112 that converts CMYK signals corresponding to the color material, an image storage unit 113 that temporarily stores the CMYK image data after the color conversion, and an image read from the image storage unit 113. A printer γ correction unit 114 that performs γ correction on the C, M, Y, and K signals of the data in accordance with the output characteristics of the printer unit 102, and C, , Y, with respect to the K signal and a halftone processing unit 115 for performing halftone processing such as dithering or error diffusion process. According to the C, M, Y, and K signals after the halftone process, the printer unit 102 forms C, M, Y, and K plate images.

  The printer γ correction unit 114 converts the density value equal to or less than the value set as the background skip amount to 0 for CMYK image data in order to match the background of the document with paper white when the printer unit 102 outputs an image. In other words, so-called “skin removal” processing is also performed. That is, the printer γ correction unit 114 serves as a γ correction processing unit and a background removal processing unit. Then, it is possible to adjust the “skin skip amount” which is the extent of the background skip.

  FIG. 2 shows an example of input / output characteristics of the printer γ correction unit 114 for a certain signal among C, M, Y, and K signals.

  In the case of the input / output characteristics indicated by the solid line in FIG. 2, Tmax corresponds to the value (density value) set as the background skip amount, and for example, input signals (C, M, Y, When the value (input density value) of each K signal is equal to or lower than Tmax, the output signal value (output density value) is set to 0, and is output as paper white. When the background skip amount is adjusted to, for example, Tmin, the input / output characteristics as indicated by the broken line are obtained. It is also possible to set a value between Tmax and Tmin as the background skip amount. When a value between Tmax and Tmin is set as the background skip amount, when the input signal value (input density value) is equal to or lower than the set value, the output signal value (output density value) is maintained at 0, and the input signal value is When the set value is exceeded, the input / output characteristics will be such that the output signal value rises.

  In connection with the light source light amount / background skip amount control, the document reading unit 100 can be provided with a transmittance (or paper thickness) detecting means 120 for detecting the transmittance of the document (or the paper thickness of the document). A detection signal indicating the transmittance (or paper thickness) is output from the transmittance (or paper thickness) detection means 120, and this detection signal is input to the light source light quantity / background skip amount control unit 104. That is, the detected transmittance (or paper thickness) of the document is notified to the light source light amount / background skip amount control unit 104. Further, in the image processing unit 101, there can be provided a document type determining means 121 for determining whether or not a read document is a document type including a pattern having highlight information based on document image data. The determination result of the document type determination unit 121 is notified to the light source light quantity / background skip amount control unit 104.

  As the document type determination unit 121, for example, a unit that determines whether there is a halftone area based on document image data before scanner γ correction can be used. As a method for determining a halftone dot region, for example, “image region separation method of mixed character / design image” (Electronic Information and Communication Society Transactions Vol. J75-DII, No. 1, pp 39-47, January 1992) The halftone dot area detection method described can be used. In the detection of the halftone dot region by this method, pixels corresponding to the top and bottom of the halftone dot are detected in the local region. Specifically, in the 3 × 3 pixel block, the density level L of the central pixel is higher or lower than the density of all the surrounding pixels, and the opposite pixel exists on the diagonal line with the density level L and the central pixel in between. When the density levels (a, b) of the four pairs are | 2 × L−a−b |> TH (fixed threshold), the center pixel is set as a halftone dot region pixel. Then, for example, it is possible to adopt a method of determining a document in which a halftone dot region pixel is detected exceeding a certain number or a certain ratio as a document type including a pattern having highlight information.

  The document type determination method is not limited to the above method. For example, in order to reduce the processing amount, a plurality of lines of a document are set as target lines, and the target lines are detected using an appropriate edge detection filter or the like, based on the detected edge amount, It is also possible to use a simple method for determining whether or not a pattern having highlight information is included in the document.

  It is also possible for the user to designate the transmittance or paper thickness of the document to the light source light quantity / background skip amount control unit 104 via the operation unit 105. The transmittance can be specified by dividing the transmittance into several ranges and specifying the divided ranges. For example, it is possible to divide the transmittance into three ranges of “large”, “medium”, and “small” and specify the range. Similarly, for the paper thickness, it is possible to divide the paper thickness into ranges such as “thickness”, “average”, and “thin” and to specify the range. Since there is a correlation as shown in FIG. 3 between the paper thickness of the original and the transmittance, it is possible to specify the paper thickness of the original and convert the paper thickness into the transmittance, and vice versa. It is also possible to perform conversion.

  The user can also specify the document type to the light source light quantity / background skip amount control unit 104 via the operation unit 105. For example, in the configuration in which “text” mode, “photo” mode, and “text / photo” mode can be specified as the image quality mode, and the filter processing unit 111 selects a filter suitable for the specified image quality mode. When the user designates the “photo” mode or the “text / photo” mode, it is assumed that the “document type including a pattern having highlight information” is designated, and when the user designates the “text” mode, It can be assumed that “a document type not including a pattern having highlight information” is designated.

  The light source light amount / background skip amount control unit 104 includes a light amount change determination unit 130 and a light amount setting unit 131 constituting a “light source light amount control unit” for adjusting the light amount of the light source for document illumination, and a pattern having highlight information. A background skip amount change determination unit 132 and a background skip amount setting unit 133 that constitute “skin skip amount control means” that adjusts the background skip amount of the background skip processing in relation to the reading of the original.

  The light amount change determination unit 130 constituting the light source light amount control means sets the light amount of the light source for document illumination inside the document reading unit 100 to its default value based on the detected or designated document transmittance or paper thickness. It is means for determining whether or not it is necessary to change from (specified value). When the light amount change determination unit 130 determines that the light amount does not need to be changed, the light amount setting unit 131 that constitutes the light source light amount control unit together with the light amount change determination unit 130 sets the light amount setting value of the document illumination light source. If it is determined that it is necessary to change the light amount, the default value is set according to the detected or specified document transmittance or paper thickness. It is a means for changing to a value different from the default value.

  Note that the user can also instruct the light amount setting value 131 to change the setting value of the light source light amount via the operation unit 105. Such embodiments are also encompassed by the present invention.

  The “background skip amount control means” is used when the light source light amount control means adjusts the light source light amount to a value different from the default value when the original is a document type including a pattern having highlight information. This is a means for adjusting the background skip amount to a value according to the transmittance of the document or the paper thickness, which is different from the default value, so as to suppress the loss of highlight information due to processing.

  The background skip amount change determination unit 132 constituting the background skip amount control unit includes a pattern having highlight information by the document type determination unit 121 when the light source light amount is changed from the default value by the light source light amount control unit. Setting of the background skip amount in the printer γ correction unit 114 when it is determined that the type is a document type or when the user designates a document type including a pattern having highlight information through the operation unit 105 It is determined that it is necessary to change the value to a value other than the default value, and it is determined that it is not necessary to change the background skip amount when a document type that does not include a pattern having highlight information is determined or designated.

  If the background skip amount setting determination unit 132, which forms the background skip amount control unit together with the background skip amount change determination unit 132, determines that the background skip amount change determination unit 132 does not need to change the background skip amount, the printer The setting value of the background skip amount in the γ correction unit 114 is left as the default value, but when it is determined that the background skip amount needs to be changed, the highlight information on the document is missing due to the background skip processing. Is set to a value different from the default value according to the transmittance of the document or the paper thickness. The relationship between the increase / decrease in the amount of light source and the increase / decrease in the amount of background skip when changing the amount of background skip is basically that the amount of background skip is reduced when the amount of light source decrease.

  Note that an aspect in which the user can instruct the background skip amount setting unit 133 to increase or decrease the set value of the background skip amount through the operation unit 105 is also included in the present invention.

  FIG. 4 is a flowchart for explaining the overall operation of the image processing apparatus and the light source light quantity / background skip amount control. Hereinafter, it demonstrates along this flowchart.

  <Step S <b> 1> Prior to reading the document by the document reading unit 100, the transmittance (or paper thickness) of the document to be read is detected by the transmittance (or paper thickness) detection unit 120 provided in the document reading unit 100. However, this step is omitted when the transmittance (or paper thickness) of the document is designated by the user through the operation unit 105.

  <Step S2> In the light source light amount / background skip amount control unit 104, the light amount change determination unit 130 sets the light amount of the illumination light source based on the detected or specified document transmittance (or paper thickness). It is determined whether or not it is necessary to change from the default value.

  Here, for example, as shown in FIG. 3, three ranges of “thick”, “average”, and “thin” are set for the paper thickness of the document, and “small” and “medium” are set for the transmittance of the document corresponding to each of these ranges. It is assumed that three ranges of “large” are set. The light source light amount setting value F1 corresponding to the “small” range of the transmittance or the “thick” range of the paper thickness corresponds to the “medium” range of the transmittance or the “average” range of the paper thickness. A light source light amount setting value F2 and a light source light amount setting value F3 corresponding to the “large” range of transmittance or the “thin” range of paper thickness are respectively determined. These F1, F2, and F3 have a magnitude relationship of F1> F2> F3. The maximum light source light amount F1 is set as a default value of the light source light amount. This default value is determined assuming a document whose transmittance is “small” or whose paper thickness is “thick”.

  When the detected or designated transmittance is in the “small” range (or the paper thickness is in the “thick” range), the light amount change determining unit 130 defaults the light source light amount setting value. It is determined that there is no need to change from the value F1. When the detected or designated transmittance is not in the “small” range (or the paper thickness is in the “thick” range), the light amount change determination unit 130 needs to change the set value of the light source light amount from the default value F1. Is determined.

  <Steps S3 to S6> The operation when it is determined that the light amount change is not necessary is as follows.

  The light amount setting unit 131 keeps the set value of the light source light amount as the default value F1 (step S3). Accordingly, in the document reading unit 100, the document is read and the document image data is input to the image processing unit 101 in a state where the light amount of the illumination light source is controlled to the default value F1, and image processing for the document image data is performed. The first half (processing from the scanner γ correction unit 110 to the color conversion unit 112) is executed (step S4). The CMYK image data converted by the color conversion unit 112 is temporarily stored in the image storage unit 113.

  The background skip amount setting unit 133 maintains the default value of the background skip amount setting value of the printer γ correction unit 114 (step S5). Here, Tmax shown in FIG. 2 is set as a default value of the background skip amount. However, the background skip amount is set for each of the C, M, Y, and K signals, and the default value is also determined. As described above, when the set value of the light source quantity is the default value, the set value of the background skip amount is also kept at the default value regardless of the document type.

  In synchronization with the operation of the printer unit 102, CMYK image data is read from the image storage unit 113, and the C, M, Y, K signals are processed by the printer γ correction unit 114 (γ correction processing and background removal processing). ), Halftone processing such as dither processing and error diffusion processing is performed by the halftone processing unit 115. The C, M, Y, and K signals after the halftone processing are output as the plate recording signals to the writing unit of the C, M, Y, and K image forming stations inside the printer unit 102 (step S6). ).

  <Steps S7 to S12> The operation when it is determined that the light amount needs to be changed is as follows.

  The light amount setting unit 131 changes the set value of the light source light amount from the default value F1 to a value corresponding to the original transmittance or the paper thickness (step S7). Here, when the transmittance of the detected or designated document is “medium” (or the paper thickness is “normal”), a value F2 determined in advance corresponding to the transmittance (or the paper thickness). If the transmittance of the detected or specified document is “large” (or the paper thickness is “thin”), the transmittance (or the paper thickness) corresponds to the transmittance. The light amount setting value is changed to a predetermined value F3. As described above, there is a relationship of F1> F2> F3. That is, when the light intensity setting value is changed from the default value F1, the transmittance of the document is “medium” or “large” (or the paper thickness is “normal” or “thin”), and the transmittance is “ Since it is a condition that the back letter is more transparent than in the case of “small” (or the paper thickness is “thick”), as described with reference to FIG. 11, the setting value of the light amount is set to the default value F1 so as to enhance the show-through removal effect The value is changed to a smaller value F2 or F2.

  As a value corresponding to the transmittance in the range from “medium” to “large” (paper thickness in the range from “normal” to “thin”), the light intensity setting value is set to one value smaller than the default value F1. Such an embodiment is also included in the present invention.

  In the document reading unit 100, the document reading is executed in a state where the document illumination light source is turned on with a light amount corresponding to the light amount setting value (F2 or F3) smaller than the default value F1, and the document image data is converted into the image processing unit 101. The first half of the image processing (processing from the scanner γ correction unit 110 to the color conversion unit 112) is executed on the document image data (step S8). The CMYK image data converted by the color conversion unit 113 is temporarily stored in the image storage unit 113. During the document reading, the document type determination unit 121 performs document type determination.

  The background skip amount change determination unit 132 specifies such a document type when the document type determination unit 121 determines that the document type includes a pattern having highlight information, or through the operation unit 105 by the user. (For example, when the image quality mode of “Photo” or “Text / Photo” as described above is specified), it is determined that the background skip amount needs to be changed. Otherwise, it is determined that the change is unnecessary. (Step S9).

  If it is determined that it is not necessary to change the background skip amount, the background skip amount setting unit 133 maintains the default value of the background skip amount setting value of the printer γ correction unit 114 (step S10). Here, as described above, Tmax shown in FIG. 2 is set as a default value. However, the background skip amount is set for each of the C, M, Y, and K signals, and the default value is determined.

  On the other hand, if it is determined that the background skip amount needs to be changed, if the background skip amount setting value is the default value, the show-through process can be surely removed by the background skip processing. There is a problem that gradation is lost due to lack of highlight information. Therefore, the background skip amount setting unit 133 changes the set value of the background skip amount to a value smaller than the default value according to the transmittance of the document or the paper thickness (step S11). By doing so, it is possible to maintain a good gradation in the highlight portion of the design while suppressing loss of highlight information.

  For example, when the original transmittance is “large” (or the paper thickness is “thin”), the setting value of the background skip amount is changed from Tmax to Tmin shown in FIG. 2, and the original transmittance is “medium”. (Or the paper thickness is “normal”), the setting value of the background skip amount can be changed to an intermediate value between Tmax and Tmin shown in FIG. Tmax and Tmin are determined for each of the C, M, Y, and K signals.

  In synchronism with the operation of the printer unit 102, CMYK image data is read from the image storage unit 113, and each CMYK signal is subjected to processing (γ correction processing and background removal processing) by the printer γ correction unit 114. Thereafter, halftone processing such as dither processing and error diffusion processing is performed by the halftone processing unit 115. The C, M, Y, and K signals after the halftone processing are output as the respective plate recording signals to the writing unit of the C, M, Y, and K image forming stations inside the printer unit 102 (step S12). ).

  When the original reading unit 100 continuously reads a plurality of originals having the same transmittance or paper thickness and the same original type, only the first original is shown in FIG. It is also possible to adopt a control method in which the determination (steps S2 and S9) as shown is performed to set the light source light amount and the background skip amount, and to apply the settings to the second and subsequent originals.

  It is also possible to cause the user to intervene in determining whether or not to change the background removal amount. When enabling user intervention, step S9 in FIG. 4 can be changed to a processing procedure as shown in FIG. 5, for example. That is, the background skip amount change determination unit 132 checks whether or not the document type determined by the document type determination unit 121 is “document type including design” (step S21). If the document type determination result is not “document type including pattern”, it is determined that the background skip amount change is unnecessary.

  When the document type determination result is “document type including design”, user intervention is requested. That is, under the control of the system control unit 106, for example, a confirmation screen as shown in FIG. 6 is displayed on the touch panel 140 of the operation unit 106 (step S22) and waits for an instruction from the user (step S23). The user touches the “YES” button on the screen (YES instruction) when he / she wants to perform the background skip amount adjustment (highlight adjustment), and touches the “NO” button when he / she does not want to perform the background skip amount adjustment. (NO instruction). The YES instruction or the NO instruction is notified from the system control unit 106 to the background skip amount change determination unit 132. The background skip amount change determination unit 132 determines that the background skip amount needs to be changed if the user instruction is a YES instruction, and determines that the background skip amount change is unnecessary if the user instruction is a NO instruction (step S24). .

  It should be noted that the same user intervention can be made even when the user specifies the document type by specifying the image quality mode as described above. In this case, in step S21 in FIG. 5, for example, when the image quality mode is “photo” or “text / photo” mode, the determination result is YES, and when the image quality mode is “text” mode, the determination result is NO. become.

  It is also possible to reflect the user's intention in the adjustment of the background skip amount. In this case, step S11 in FIG. 4 can be changed to a processing procedure as shown in FIG. 7, for example.

  That is, under the control of the system control unit 106, for example, a screen as shown in FIG. 8 is displayed on the touch panel 140 of the operation unit 105 (step S31) and waits for input from the user (step S32).

  In FIG. 8, a “1” button, a “2” button, a “3” button, a “4” button, and a “5” button are value designation buttons used for designating the setting value of the background skip amount. As an example of the correspondence between these value designation buttons and the setting value of the background skip amount, the “1” button corresponds to the maximum setting value (default value) Tmax of the background skip amount shown in FIG. The buttons correspond to the minimum setting value Tmin of the background skip amount, and the “2” to “4” buttons have three setting values T2, T3, T4 allocated between Tmin and Tmax (where Tmax> T2> T3). > T4> Tmin) respectively. If the setting value of the background skip amount determined based on the document transmittance or the paper thickness as described above in the background skip amount setting unit 133 is, for example, an intermediate value T3 between Tmax and Tmin in FIG. On the touch panel 140 of 105, a “Δ” mark is displayed immediately below the “3” button, and “3” is displayed as a “recommended value”. The “confirm” button is a button that the user touches to confirm the set value of the background removal amount.

  When the user determines that the displayed “recommended value” can be left as it is, the user can confirm the setting of the background skip amount by immediately touching the “confirm” button.

  The user can change the setting value of the background skip amount from the “recommended value” automatically determined based on the transmittance or the paper thickness by touching the value designation button. In this example, by touching the “2” button, the set value of the background skip amount can be increased from the intermediate value T3 between Tmin and Tmax in FIG. 2 to the intermediate value T2 between the intermediate value and Tmax. (At the same time, the “△” mark moves directly below the “2” button). Conversely, by touching the “4” button, the set value of the background skip amount can be decreased from the intermediate value of Tmin and Tmax in FIG. 2 to the intermediate value T4 of the intermediate value and Tmin (“Δ” The "" mark moves directly below the "4" button). By touching the “1” button or the “5” button, the setting value of the background skip amount can be changed to Tmax or Tmin in FIG. 2 (the “Δ” mark is the “1” button or the “5” button). To go directly below).

  Now, when the user touches the value designation button in the input waiting state (step S33, value designation), the system control unit 106 moves the “Δ” mark directly below the touched value designation button as described above. The display on the touch panel 140 is updated (step S34), and the input is waited again (step S32).

  When the user touches the “confirm” button, a confirmation instruction is issued from the system control unit 106, and in response to this, the background skip amount setting unit 133 sets the set value of the background skip amount to a value immediately above the “Δ” mark. A value corresponding to the designated button is determined (step S35).

  As can be easily understood from FIG. 2, when the setting value of the background skipping amount is increased, the effect of preventing the show-through by the background skipping processing is enhanced, but on the other hand, the lack of highlight information on the manuscript increases. The image after the skipping process is skipped. Conversely, if the setting value of the background skip amount is decreased, the highlight information is less likely to be lost (however, suppression of show-through tends to be insufficient). As described above, the increase / decrease in the background skip amount is related to the reproducibility of the highlight information of the document image. For this reason, the expression “highlight” is used in FIGS. 6 and 8, but it may be expressed as “amount of background removal” instead.

  FIG. 9 is a schematic cross-sectional view for explaining an example of a specific configuration of the document reading unit 100. The document reading unit 100 shown here includes a scanner unit 200 and an automatic document feeder (ADF) 230 attached thereto.

  In the scanner unit 200, reference numeral 231 denotes a contact glass on which an original is placed, and reference numeral 232 denotes an illumination lamp as a light source for original illumination. A drive circuit (not shown) of the illumination lamp 232 turns on the illumination lamp 232 with a light amount corresponding to the set value of the light source light amount set by the light amount setting unit 131.

  A description will be given assuming that a document placed on the contact glass 231 is read. The original is illuminated by the illumination lamp 232, and the reflected light image of the original is reflected by the first mirror 233 in the direction opposite to the sub-scanning direction y (left direction in the figure). The illumination lamp 232 and the first mirror 233 are mounted on a first carriage (not shown) that is driven at a constant speed in the sub-scanning direction y (rightward in the figure) when reading a document. A second mirror 234 and a third mirror 235 are mounted on a second carriage (not shown) that is driven at a constant speed at a half speed in the same direction as the first carriage when reading a document. The reflected light image reflected by the first mirror 233 is reflected downward (z) by the second mirror 234, further reflected by the third mirror 235 in the sub-scanning direction y, converged by the lens 236 and imaged (CCD). ) 207 and converted into an electrical signal. Reference numeral 238 denotes a driving motor for the first and second carriages.

  A white reference plate 239 and a base point sensor 249 for detecting the first carriage are disposed between the reading glass 240 and the document starting edge positioning scale 251. The white reference plate 239 is used for shading correction. There is an image signal circuit (not shown) for performing shading correction processing on the image signal output from the CCD 207, and output data of the image signal circuit is original image data input to the image processing unit 101.

  Next, the ADF 230 will be described. In the ADF 230, the originals stacked on the original tray 241 are fed one by one between the conveying drum 244 and the pressing roller 245 by the pickup roller 242 and the registration roller pair 243. The transport drum 244 rotates counterclockwise in the figure, and the fed document passes over the reading glass 240 while being in close contact with the transport drum 244, and below the document tray 241 by the discharge rollers 246, 247A and 247B. Are discharged onto the paper discharge tray 248.

  When reading a document supplied by the ADF 230, the illumination lamp 230 moves immediately below the reading glass 240 and illuminates the document passing through the reading glass 240. The reflected light image of the original is incident on the CCD 207 via the mirrors 233, 234, 235 and the lens 236, and is converted into an electrical signal.

  The transmittance (or paper thickness) detecting means 120 may be configured to detect the transmittance (or paper thickness) of the document moving from the pickup roller 242 of the ADF 230 to the registration roller pair 243, for example. An example of such transmittance (or paper thickness) detecting means is schematically shown in FIG.

  The transmittance (or paper thickness) detection means 120 shown in FIG. 10 includes a detection head 300 and a transmittance (or paper thickness) detection circuit 303. The detection head 300 has a laser diode 301 serving as a light source and a phototransistor 302 serving as a light receiving element facing each other, and the document 304 being moved from the pickup roller 242 to the registration roller pair 243 is scanned with the laser diode 301 and the phototransistor 302. Are arranged in a positional relationship so as to cross the optical path between the two.

  The transmittance (or paper thickness) detection circuit 303 adjusts the document feeding operation and timing by the ADF 230 and energizes the laser diode 301 and the phototransistor 302. When there is no document in the optical path between the laser diode 301 and the phototransistor 302 (paper thickness = 0), the laser light emitted from the laser diode 301 is incident on the phototransistor 302 without being blocked by the document. The amount of received light 302 is maximized. When the original enters the optical path between the laser diode 301 and the phototransistor 302, the amount of light received by the phototransistor 302 decreases. However, as the transmittance of the original decreases (the paper thickness increases), the decrease in the amount of received light increases. The transmittance (or paper thickness) detection circuit 303 holds the current value of the phototransistor 302 at the timing when the margin of the document passes through the optical path between the laser diode 301 and the phototransistor 302, and sets the amount of light received by the phototransistor 302. A detection signal that is proportional, that is, proportional to the transmittance of the document (or inversely proportional to the paper thickness of the document) is output.

  The transmittance (or paper thickness) detecting means 120 is not limited to the one having the above-described configuration. Further, the detection position is not limited to the above example as long as it can be detected before reading the document.

  It is also possible to provide a transmittance (or paper thickness) detection means 120 for the document placed on the contact glass 231. Such a transmittance (or paper thickness) detecting means is provided with a light receiving element such as a phototransistor at an appropriate position of a pressure plate 248 for holding a document placed on the contact glass 231, and an illumination lamp at that position. It is possible to have a configuration in which the light 232 is turned on, the light transmitted through the document is received by the light receiving element, and a detection signal proportional to the amount of received light is output from the detection circuit.

  If the transmittance (or paper thickness) detecting means 120 for the document placed on the contact glass 231 is provided, the document is supplied by the ADF 230 even when the document on the contact glass 231 is read. It is possible to perform the same light source light amount control and background skip amount control as in reading. When such a transmittance (or paper thickness) detecting means 120 is not provided, the user can designate the transmittance (or paper thickness) of the document on the contact glass 231 in advance through the operation unit 105, so that the same light source light amount is obtained. It is possible to control and control the amount of background removal.

  In the image processing apparatus according to the embodiment described above, the printer γ correction unit 114 in the image processing unit 101 performs background removal processing together with γ correction. However, the background removal process may be performed independently of other processes. For example, for each of the C, M, Y, and K signals, there is separately provided a background removal processing means for converting a density value equal to or less than the set value of the background removal amount to 0, and C, M processed by the background removal processing means. , Y, K signals may be input to the printer γ correction means.

  The description of the light source light amount / background skip amount control in the above embodiment is also a procedure description of the control method of the present invention. For example, in FIG. 4, the steps S2 and S7 correspond to the light source light quantity control step, and the steps S9 and S11 correspond to the background skip amount control step.

DESCRIPTION OF SYMBOLS 100 Document reading part 101 Image processing part 102 Printer part 104 Light source light quantity / background skip amount control part 105 Operation part 106 System control part 110 Scanner gamma correction part 111 Filter processing part 112 Color conversion part 113 Image storage part 114 Printer gamma correction part ( Scattering treatment means)
115 Halftone Processing Unit 120 Transmittance (or Paper Thickness) Detection Unit 121 Document Type Determination Unit 130 Light Amount Change Determination Unit 131 Light Amount Setting Unit 132 Background Skipping Amount Change Determination Unit 133 Background Skipping Amount Setting Unit 140 Touch Panel

JP 2004-320472 A

Claims (7)

A document reading means for reading a reflected light image of a document illuminated by an illumination light source and inputting document image data;
An image processing apparatus comprising: image processing means for performing at least a background skip processing for converting a density value equal to or less than a value set as a background skip amount to document image data input from the document reading means. ,
Light source light quantity control means for adjusting the light quantity of the illumination light source according to the transmittance of the original or the paper thickness;
Based on the edge amount of the original image data, and the document type determination means for the document to determine the constant whether the with highlight information,
When it is determined that the document has highlight information, when the light amount of the illumination light source is adjusted to a value different from the default value by the light source light amount control means, the background skip amount is set to the default amount. An image processing apparatus comprising: a background skip amount control unit that adjusts to a value smaller than a default value of the background skip amount according to the transmittance or paper thickness of the document, which is different from the value. The image processing apparatus according to claim 1, wherein the document type determination unit determines the document type based on whether or not the highlight information is included. Means for the user to specify whether or not the document is of a document type including a pattern having highlight information;
The image processing apparatus according to claim 1, wherein the user specifies a document type designation to the background skip amount control unit. A detection means for detecting a transmittance or a paper thickness of the original in the original reading means;
The image processing apparatus according to claim 1, 2 or 3, wherein the transmittance or paper thickness of the document detected by the detection means is notified to the light source light quantity control means and the background skip amount control means. . 4. The image processing according to claim 1, further comprising means for a user to specify a transmittance or a paper thickness of the document for the light source light amount control unit and the background skip amount control unit. apparatus. A document reading unit that reads a reflected light image of a document illuminated by an illuminating light source and inputs document image data, and the document image data input from the document reading unit is less than or equal to a value set as a background skip amount. An image processing apparatus control method comprising: image processing means for performing at least a background removal process for converting a density value to 0,
A light source light amount control step of adjusting the light amount of the illumination light source according to the transmittance of the original or the paper thickness;
Based on the edge amount of the original image data, and the document type determination step of the original is determine constant whether with highlight information,
When it is determined that the document has highlight information, when the light amount of the illumination light source is adjusted to a value different from the default value by the light source light amount control step, the background skip amount is set to the default amount. A background skip amount control step for adjusting the background skip amount to a value smaller than the default value of the background skip amount according to the transmittance or paper thickness of the document, which is different from the value. Method. A document reading means for reading a reflected light image of a document illuminated by an illumination light source and inputting document image data;
An image processing apparatus comprising: an image processing unit that performs at least a background skip process for converting a density value equal to or less than a value set as a background skip amount to document image data input from the document reading unit; A program for
A light source light amount control procedure in which the image processing apparatus adjusts the light amount of the illumination light source according to the transmittance or paper thickness of the document;
The image processing apparatus, based on the edge amount of the original image data, and the document type determining step in which the original is determine constant whether with highlight information,
When the image processing apparatus, the document when it is determined to have a high light information, the light amount of the illumination light source by the light source light quantity control procedure is adjusted to its default value and different values, the A program for executing a background skip amount control procedure for adjusting the background skip amount to a value smaller than the default value of the background skip amount according to the transmittance or paper thickness of the document, which is different from the default value. .

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