JPH1013668A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can execute copying by means of correction for skipping the low density part or the high density part of hard copy or both parts at the time of copying without reducing the number of substantial gradation reproduction stages by skipping the low density part and the high density part of read data through the use of a specified original read reference value when an original is discriminated to be the specified one and standardizing it into eight bits data. SOLUTION: The printer control part 400 of a digital full color copying machine and a picture signal processing part 300 connected to the print head control part convert picture data obtained by a CCD sensor 14 into multivalue digital data. A shading correction part 302 shading-corrects multivalue digital data by using a shading correction coefficient α which is previously calculated by the prescribed reference value. Then, it is standardized into eight bits data having 256 gradations and it is sent to a succeeding circuit so as to execute a prescribed processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a digital copying machine.

[0002]

2. Description of the Related Art In an image forming apparatus such as a digital color copying machine, when a hard copy is used as an original, a decrease in saturation due to color turbidity, the occurrence of false contours, and a decrease in color development such as skin color are likely to occur. Was. This is due to the fact that a hard copy image generally has a narrower dynamic range for reproducing colors and densities and a lower resolution than silver halide photographs and the like. Therefore, a color image forming apparatus such as a conventional digital color copying machine forms an image using a gradation correction curve that skips a low density portion and a high density portion of a hard copy at the time of gradation correction. Has solved the above problem. Here, a gradation correction curve that skips the low-density portion and the high-density portion is, for example, such that gray close to black is printed blacker and gray close to white is printed whiter. 9 is a gradation correction curve used for performing correction for emphasizing a medium density portion.

[0003]

However, in the prior art, since the low-density portion and the high-density portion are skipped during tone correction, the actual number of tone reproduction steps is reduced. There was a problem that tone reproduction was reduced. That is,
Even if the gradation correction unit receives standardized 8-bit data of, for example, 256 gradations before the gradation correction, the gradation correction skips the low density part and the high density part in the data by 20 gradations each. If the correction has been made, there will be substantially only 216 gradation reproduction stages.

Accordingly, the present invention provides an image which can be copied by performing correction for skipping a low-density portion, a high-density portion, or both of the hard copy at the time of copying without reducing the actual number of gradation reproduction steps. It is an object to provide a forming device.

[0005]

In order to achieve the above object, the present invention provides a document determining means for determining whether or not a document is a specific document;
It has a low-density side reading reference value for a specific document, a high-density side reading reference value for a specific document, or both reading reference values, and when the document is determined by the document discriminating means to be a specific document, A reading reference value changing unit for normalizing by using the reading reference value for the specific document instead of the normal reading reference value.

The document discriminating means includes a pattern detecting section for detecting that a pattern indicating that the document is a specific document is attached to the document at the time of pre-scanning or at the start of scanning. It is characterized by determining that the original is a specific original by being attached. Further, the document discriminating means is a receiving unit for receiving an instruction as to whether or not the document is a specific document from an operator. The reading reference value changing means is configured to receive an instruction that the document is a specific document. In this case, the standardization is performed by using the reading reference value for the specific document instead of the normal reading reference value.

The pattern is one or more solid reference patterns formed outside the image area of the original, and the reading reference value changing means changes the reading reference value in accordance with the reading value of the reference pattern. Is determined, and standardization is performed by using the determined reading reference value. Further, the pattern is a pattern written in a color inconspicuous to a viewer on a part or the front of an image area, and the document discriminating means detects that the pattern is attached to a document. Is used to determine that the original is a specific original.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below using a digital full-color copying machine as an example. (1) First Embodiment (1-1) Overall Configuration of Digital Full-Color Copying Machine FIG. 1 is a diagram showing the overall configuration of a digital full-color copying machine according to a first embodiment of the present invention. The digital copier,
Image reader unit 1 that roughly reads document images
0, and a printer unit 20 for printing and reproducing the image read by the image reader unit on copy paper.

The scanner 1 in the image reader unit 10
Reference numeral 1 denotes an exposure lamp 12 for irradiating a document, a rod lens array 13 for condensing light reflected from the document, and a contact-type CCD image sensor 14 (hereinafter simply referred to as "a") for converting the condensed light into an electric signal. A CCD sensor ”). The scanner 11 uses the motor 1 when reading a document.
5, moves in the direction of the arrow (sub-scanning direction), and scans the original placed on the transparent platen 16. The reflected light of the document surface irradiated by the exposure lamp 12 is C
Photoelectric conversion is performed by the CD sensor 14. The image data obtained by the photoelectric conversion by the CCD sensor 14 is subjected to A / D conversion by the image signal processing unit 300, and then subjected to shading correction, density conversion, color correction processing, MTF correction processing, and the like. Is sent to the printer unit 20.

The print data sent to the printer unit 20 includes:
After gradation correction, D / A conversion is performed to obtain exposure data. In accordance with the exposure data, the laser unit of the print head unit 22 is driven to form an electrostatic latent image for each of the toners of C, M, Y, and BK, and the photosensitive drum 21 is charged uniformly by the charging charger 23. An electrostatic latent image is formed on the image. Thereafter, of the C, M, Y, and BK developing devices 24, the developing device of the color selected and moved to the position close to the photosensitive drum 21 develops the corresponding color.

On the other hand, the paper fed and conveyed from the paper feed cassette 25 is fed in synchronism with the suction position on the transfer drum 26, and is electrostatically adsorbed on the transfer film 28 by the adsorption means 27. You. The developed image on the photosensitive drum 21 is transferred to the transfer sheet 29 on the sheet.
Is transcribed. As described above, the processes of reading, forming a latent image by laser exposure, developing, and transferring are performed by the number of colors (four times in the case of normal full-color image formation).
After the repetition, the sheet is separated from the transfer drum, and the image is fixed by the fixing device 30.

On the back side of the platen 16, a reference plate 17 which is a black reference plate and a white reference plate for shading correction is provided. Also, at an easy-to-operate position on the front surface of the image reader unit 10, as shown by a dotted line, an operation panel 18 is provided.
Are provided, and ten keys for inputting the number of copies and copy keys for instructing start of copying are provided.

On the other hand, a control section 41 for controlling each section is provided above the printer section 20. The control unit 41 includes an image reader control unit 100, an image control unit 200, a printer control unit 400, and a print head control unit 500, as shown in FIGS. The image reader control unit 100 controls each unit of the image reader unit 10, receives a position signal indicating the position of the document on the platen 16 from the position detection switch 101, and, based on the position signal, via the drive I / O 102. ON / OFF of the exposure lamp 12 is controlled. Drive I
The drive of the motor 15 is controlled via the / O 102, the parallel I / O 103 and the scan motor driver 104, and the image data is read by moving the scanner 11 within a necessary range. On the other hand, the image reader control unit 100 is connected to the image control unit 200 by a bus. Image control unit 200
Are connected to each of the CCD sensor 14 and the image signal processing unit 300 via a bus. CCD sensor 14
Is input to the image signal processing unit 300, and necessary processing is performed.

The printer control section 400 controls general copying operations. Analog signals from various sensors 401 to 405 for automatic density control are input to the printer control unit 400, and various data are input via the parallel I / O 407 by key input to the operation panel 18. In the printer control unit 400, a control ROM 408 storing a control program and a data ROM 409 storing various data are connected. The printer control unit 400 includes various sensors 401 to 405, an operation panel 1
8, data from the data ROM 409, and the control RO
In order to control the copy control unit 410 and the display unit 411 according to the contents of M408 and to perform automatic density control,
A grid voltage generation unit 414 and a developer bias voltage generation unit 415 of the charger are controlled via the parallel I / O 412 and the drive I / O 413. The grid voltage generation unit 414 controls the surface potential of the photosensitive drum, and
15 controls the bias potential of the developing device,
The amount of toner adhering to the photosensitive drum is adjusted, and the density is adjusted.

The print head control section 500 controls the control RO.
The control operation is performed according to the control program stored in M501. Also, the print head controller 500
Are the image reader control unit 100 and the image signal processing unit 30
0 is connected via an image data bus, and based on an image signal input via the image data bus, γ correction is performed by referring to the contents of a data ROM 502 in which a γ correction conversion table is stored. . At this time, when the multi-valued dither method is used as the gradation expression method, dither processing is performed, and the laser diode driver 505 is controlled via the drive I / O 503 and the parallel I / O 504. The emission of the laser diode 506 is controlled by a laser diode driver 505. The print head control unit 500 is connected to the image reader control unit 100, the image signal processing unit 300, and the printer control unit 400 via a bus, and is synchronized with each other.

(1-2) Configuration of Image Signal Processing Unit FIG. 4 is a block diagram of the image signal processing unit 300. Hereinafter, each configuration will be described. Image data that is analog data of the three primary colors R, G, and B obtained by the photoelectric conversion of the CCD sensor 14 is converted by the A / D converter 301 into multi-valued digital data r, g, and b.

The shading correction unit 302 performs shading correction on the multi-valued digital data by using a previously calculated shading correction coefficient α, and
After normalizing the data to 8-bit data having 56 gradations, the 8-bit data is converted into the density conversion unit 304 and the area determination unit 30.
Send to 5. Hereinafter, the calculation of the shading correction coefficient α will be described. The shading correction unit 302
Is the CCD before calculating the shading correction coefficient α.
The correction of the variation in the sensitivity of each sensor and the unevenness of the light amount of the exposure lamp are performed, but the description of the correction is omitted. The same applies to Embodiments 2, 3, and 4 described below.

First, the shading correction unit 302 operates the platen 1 read by the CCD sensor 14 of the scanner 11.
6, the reading values of the black reference plate and the white reference plate for shading correction on the back side are received. The reading is V
a, Vb, the shading correction coefficient α
Is represented by the following equation.

[0019]

(Equation 1) Here, A and B are reading reference values for calculating a shading correction coefficient, and A and B are respectively a high density reading reference value (black reading reference value) and a low density reading reference value (white reading reference value). ). For A and B, a0 and b0, which are values that the shading correction unit 302 has internally during normal copying, respectively, are used. This a
0 and b0 are reading reference values for a normal copy mode. The values a0 and b0 take, for example, the minimum value 0 and the maximum value 255 of 256 gradations, respectively.

The shading correction unit 302 performs shading correction using the shading correction coefficient α obtained as described above. At this time, the read value from the CCD sensor 14, more precisely, the A / D converter 301
By applying Vout, which is the value of the multi-valued digital data received from the above, to the following equation, image data that is the value after shading correction is obtained.

[0021]

(Equation 2) Then, the shading correction unit 302 normalizes the obtained image data to 8-bit data, and sends the 8-bit data to the density conversion unit 304 and the area determination unit 305. For example, if Vb and Va are 1000 and 0, respectively, the value of the image data when the white reference plate is read is:

[0022]

(Equation 3) Becomes Similarly, the value of the image data when the black reference plate is read is

[0023]

(Equation 4) Becomes Note that the white reference plate and the black reference plate need not be completely white and black. When the operation panel 18 receives a generation mode instruction from the operator, the reference value changing unit 303 sets the read reference values a0 and b0 for the normal copy mode used by the shading correction unit 302 at the time of calculating the shading correction coefficient. The reference value changing unit 303 changes the read reference values a1 and b1 for the generation mode contained therein. In addition, the density conversion correction value c0 used by the density conversion unit 304 is changed to a density conversion correction value c1 for the generation mode contained therein. The density conversion correction value c1 is a correction value used for fine adjustment of the correction, and the density conversion correction value will be described later. Here, the generation mode is a mode in which a hard copy copy process is performed when a document used for copying is a hard copy. Specifically, in the generation mode, the shading correction unit 302 calculates a shading correction coefficient α using the generation mode reading reference values a1 and b1, and performs shading correction using the calculated shading correction coefficient α. I do. The reading reference values a1 and b1 for the generation mode are values that skip the low density portion and the high density portion of the hard copy, that is, a1 <a0 and b0 <b1. For example, the values of a1 and b1 are -20, 2
If it is 80, then the value of the image data when the white reference plate is read is:

[0024]

(Equation 5) And exceeds the maximum value 255 that can be represented by 256 gradations, so that the image data is output as 255. That is, when the original is whiter than the white reference plate or has a reflectance close to that of the white reference plate, the image data has the same value of 255.
Is output from the shading correction unit 302.

Similarly, the value of the image data when the black reference plate is read is

[0026]

(Equation 6) Is smaller than the minimum value 0 that can be expressed by 256 gradations, so that the image data is output as 0. That is,
If the original has a reflectance lower than that of the black reference plate or has a reflectance close to that of the black reference plate, the same image data 0 is output from the shading correction unit 302. By changing the reading reference value for the generation mode in this way, the reading range at the time of the generation copy is set to a required range, and operations such as reducing color turbidity by skipping a portion having a reflectance close to white are performed. be able to.

The density converter 304 converts the reflectance data of the original into actual density data and sends the density data to the color corrector 306. Conversion into density data is performed by the following equation. I. D. Data = -LOG ((C / c0) * ref.data) D. Data is density data output from the density conversion unit 304, and ref.data is data after shading correction input from the shading correction unit 302 to the density conversion unit 304. C is a density conversion correction value, and is a variable changed by the reference value changing unit 303. The value of C is determined by the reference value changing unit 303.
As a result, the density conversion correction value c0 at the time of copying in the normal mode is set unless it is changed.

Therefore, when copying in the normal mode, I.I. D. Data = -LOG (ref.data) The data after shading correction is converted into density data using the equation: On the other hand, in the generation mode, the density conversion unit 304 includes the density conversion correction value c1 for the generation mode by the reference value change unit 303.
Is set. Therefore, when copying in the generation mode, I.I. D. Data = -LOG ((c1 / c0) * ref.data) The data after shading correction is converted into density data using the formula:

Here, the density conversion correction value c1 in the generation mode usually has a relationship of c1> c0. In this way, the reason why the density conversion correction value for the generation mode is also changed in the generation mode is to perform fine adjustment of the correction by changing the above-described reading reference value. The color correction unit 306 performs color correction of the density data from the density conversion unit 304. UCR / BP processing,
Also, a masking process is performed, and the density data is converted into C, M, Y,
BK is converted into print data of each color.

An area determination unit 305 determines a color / color based on the image data output from the shading correction unit 302.
Image regions such as black and edge / non-edge portions are determined. Thereafter, the MTF correction unit 307 uses the determination result of the area determination unit 305 to perform MTF correction on the data after color correction by the color correction unit 306, such as smoothing processing and edge enhancement processing. This MTF correction is performed according to the contents set in advance by the operator through the operation panel 18. The MTF-corrected data is sent to the scaling / moving unit 308, and the data is subjected to a magnification change process based on a magnification or the like set in advance by the operator on the operation panel 18. Further, the image data subjected to the magnification change processing and the like is sent to the color balance unit 309, and the density and the color balance set in advance by the operator through the operation panel 18 are used.
The color balance is adjusted, and a reproduced image is formed on copy paper in the printer unit 20 based on the adjusted data.

The printer control unit 400 includes an operation panel 1
8 is connected and receives various instructions from the operator. FIG. 5 is an external view of the operation panel 18. The operation panel 18 includes an LCD touch panel 51, a start key 57, a numeric keypad 58, and an IC card insertion unit 61. On the LCD touch panel 51, a density button 53, a magnification button 54, a paper button 55, and a generation button 56 are displayed. The generation button 56 is a button for receiving a generation mode. When the generation mode instruction is received by this button, the printer control unit 400
The reference value changing unit 303 is notified that the current mode is the generation mode. Similarly, when the other buttons 53 to 55 are operated by the operator, various key inputs are accepted, and the printer control unit 400 transmits the instructions to the MTF correction unit 307, the scaling / moving unit 308, and the color balance unit 309.
Send to The number of copies and the like are input from the ten keys 58.
The display unit 52 displays the received number of copies and the like. The copy start key 57 receives an instruction to start copying. The IC card 60 is inserted into the IC card insertion section 61. The IC card 60 previously stores data such as the number of copies, a copy magnification, a paper size, and a generation mode. Simply by inserting the IC card 60 into the IC card insertion unit 61, the stored data can be read. The operation is the same as the input from the buttons 53 to 56 and the ten keys 58.

(1-3) Operation of Digital Full-Color Copying Machine The operation of the digital full-color copying machine according to the present embodiment will be described with reference to the flowcharts shown in FIGS. First, the operation panel 18 is
A generation mode instruction is received together with the designation of the copy magnification and the number of copies (step S101).
The copy start key is pressed (step S102), and if the current mode is the generation mode (step S10)
3) The reference value changing unit 303 (FIG. 4) sets the generation mode reading reference values a1 and b1 in the shading correction unit 302, and sets the density conversion correction value c1 for the generation mode in the density conversion unit 304. (Step S104). On the other hand, if the current mode is not the generation mode in step S103, the reference value change unit 303 sets the reading reference values a0 and b0 for the normal copy mode in the shading correction unit 302, and further sets the density conversion unit 304 for the normal copy mode. Is set (step S105). Next, the shading correction unit 302 performs a shading correction coefficient calculation process using the set reading reference value (step S106). Specifically, the processing of the flow shown in FIG. 7 is performed. First, the image reader control unit 100 includes a CCD
The sensor 14 and the exposure lamp 12 are turned on (step S201), and the motor 15 is driven to
Is moved to the black reference plate on the back side of the platen 16 (step S202). Then, the CCD sensor 14 detects the black level of the black reference plate, and stores the detection data V as a read value Va of the black reference plate (step S20).
3). Similarly, the image reader control section 100 moves the scanner 11 to the white reference plate on the back side of the platen 16 (step S204), causes the CCD sensor 14 to detect the white level of the white reference plate, and outputs the detection data V to the white reference plate. It is stored as the reference plate reading value Vb (step S205), and then the scanner 11 is moved to the home position (step S206). Next, the shading correction unit 302 calculates the shading correction coefficient α using the read values Va and Vb of the reference plate obtained by the above detection and the set read reference value (step S207). The set read reference values are a1 and b1 when the current mode is the generation mode, and are a0 and b0 when the current mode is the normal copy mode. Thus, the shading correction coefficient calculation processing ends.

Next, the image reader control section 100 performs a pre-scan process to detect a document size and the like (step S107). Next, the printer control unit 400 receives various internal environmental sensor inputs (step S10).
8) Further, the received various sensor inputs and process control operations (detection of photosensitive drum surface potential, A
After the conditions at the time of image formation are appropriately changed by detecting the toner adhesion amount of the IDC pattern, etc., the process proceeds to the copy process (step S109).

The printer control section 400 activates the components of the printer and conveys the paper in synchronization with the photosensitive drum and the transfer drum. The document is exposed, scanned, photoelectrically converted by the CCD sensor 14, read as reflectance data, and subjected to A / D conversion, and then subjected to shading correction using the previously calculated shading correction coefficient. At this time, if the previously calculated shading correction coefficient is a shading correction coefficient calculated for the generation mode, in the output data,
The data is obtained by skipping the low density part and the high density part. After the data is standardized to 8-bit data, density conversion is performed using the set density conversion correction value. At present, in the case of the generation mode, since the density conversion correction value for the generation mode is set, the density conversion is performed using the correction value. The density data obtained after the density conversion undergoes color correction processing, MTF correction processing, and the like, and is sent to the printer unit as print data. The printer unit exposes the surface of the photosensitive drum according to the received print data to form a latent image, develops the latent image, and transfers it to paper. After repeating these series of processes for the required colors, the sheet is separated from the transfer drum, and the image is fixed by the fixing device and output (step S110). If the number of copies is specified plurally, the copying process is repeated and the process is terminated (step S111).

As described above, according to the present embodiment, when an instruction of the generation mode is received from the operator, the shading correction unit reads the generation mode reading reference values, that is, the low density portion and the high density portion. The low-density part and high-density part are skipped during shading correction using the read reference value for skipping, and then standardized to 8-bit data. It is possible to make a copy in which correction for skipping low-density and high-density portions of a hard copy is performed without causing a decrease in the number of substantial tone reproduction steps caused by skipping high-density portions.

In this embodiment, the shading correction coefficient calculation processing is performed before the pre-scan, but the present invention is not limited to this. For example, the shading correction coefficient calculation processing may be performed for each copy operation in step S110. (2) Embodiment 2 In the digital full-color copying machine according to Embodiment 1 described above, the shading correction unit replaces the reading reference value used for normal copying in the generation mode with a reading reference value for the generation mode.
That is, the shading correction coefficient is calculated using the reading reference value for skipping the low-density portion and the high-density portion of the document, thereby realizing the shading correction for skipping the low-density portion and the high-density portion of the document. . On the other hand, in the second embodiment, the shading correction unit uses only the reading reference value used for normal copying as the reading reference value itself. In the generation mode, the white reference plate and the black reference plate for the generation mode are used to change the shading correction value, thereby skipping the low density portion and the high density portion of the original. Achieve shading correction.
Note that, unlike the first embodiment, the shading correction is performed by adjusting the output from the CCD sensor 14 for offset adjustment and gain adjustment.

Therefore, the configuration of the entire copying machine according to the present embodiment is substantially the same as that of the first embodiment, and therefore the description thereof is omitted, and the white reference plate for the generation mode, which is a different component from the first embodiment, is omitted. A platen including a black reference plate, an image reader control unit, and an image signal processing unit will be described. (2-1) Platen Including White Reference Plate and Black Reference Plate for Generation Mode FIG. 8 is an external view of a platen 81 having a reference plate 82 that is a white reference plate and a black reference plate in the second embodiment. . The platen is provided at the same position as the platen 16 in FIG. FIG. 8A is a diagram showing the appearance of the front side of the platen 81, and FIG.
FIG. 7 is a diagram showing the back side of the platen 81. On the back side of the platen 81, a reference plate 82 for generation mode is provided.
Is provided. The reference plate 82 includes a white reference plate Q0 and a black reference plate P0 for a normal copy mode, and a white reference plate Q1 and a black reference plate P1 for a generation mode. The white reference plate Q0 and the black reference plate P0 for the normal copy mode are the same as the white reference plate and the black reference plate in the first embodiment, and therefore, description thereof will be omitted. Next, the white reference plate Q1 for the generation mode is lower in brightness than the white reference plate Q0 for the normal mode, and is white close to gray. Similarly, the black reference plate P1 for the generation mode
Is higher in brightness than the black reference plate P0 for the normal copy mode, and is black close to gray. Accordingly, the range width of the density of the generation reference plate, that is, the density difference between the black reference plate and the white reference plate, is smaller than the range width of the normal copy mode reference plate. The four reference plates described above, that is, a white reference plate Q0 for normal copy, a white reference plate Q1 for generation mode, a black reference plate P0 for normal copy, and a white reference plate P1 for generation mode are shown in FIG. ), The scan position q0,
q1, p0, and p1.

(2-2) Image Reader Control Unit The image reader control unit 100 according to the present embodiment performs, at the time of the shading correction value change processing, the scan position information p of the internal reference plate for changing the shading correction value, q
, The white reference plates Q0, Q1 and the black reference plates P0, P
1 is read by the CCD sensor 14. In the scan position information p, q, as initial values, position information indicating the scan positions q0, p0 of the reference plate for the normal copy mode among the reference plates 82 is set as the scan position information.

The scan position information changing means is a means in the image reader control unit 100, and changes the scan position information depending on whether or not the generation mode is set.
Specifically, when the operator instructs the generation mode from the operation panel 18, a notification that the mode is the generation mode is received from the printer control unit 400, and the scan position information included in the image reader control unit is converted to the generation mode. Reference plate scan position q1, p1
To the location information indicating. Similarly, when there is no instruction of the generation mode, the scan position is changed to the scan position q0, p0 of the reference plate for the normal copy mode.

(2-3) Image Signal Processing Unit The image signal processing unit 300 according to the present embodiment includes a reference value changing unit 303 which is a component of the image signal processing unit 300 according to the first embodiment shown in FIG. Since the configuration is the same except that the configuration of the shading correction unit 302 is different, the description of the same components will be omitted, and the shading correction unit 302 that is a different component will be described.

The shading correction unit 302 performs shading correction, and performs shading correction value changing processing prior to shading correction. More specifically, a black reference plate and a white reference plate are read from the CCD sensor 14, and the read values Va and Vb of the black reference plate and the white reference plate are used as the black-side reading reference values included in the shading correction unit 302. The offset adjustment value and the gain adjustment value of the output voltage of the CCD sensor 14, which are output as a0 and the white-side reading reference value b0, are obtained. The shading correction unit 302 uses the obtained offset adjustment value and gain adjustment value to perform CCD shading correction.
The output voltage of the sensor 14 is corrected for each of R, G, and B, and then normalized to 8-bit data.

(2-4) Operation of Digital Full-Color Copying Machine The operation of the digital full-color copying machine in the present embodiment will be described with reference to flowcharts shown in FIGS. First, similarly to the flow of FIG. 6 of the first embodiment, various key input processes and the like are performed (step S30).
1. If the current mode is the generation mode (step S303), the scan position information changing means in the image reader control unit 100 determines the scan position information p of the reference plate for calculating the shading correction value.
q is the position p1 of the reference plate for the generation mode,
The position information is changed to the position information of q1 (step S304). On the other hand, if the current mode is not the generation mode in step S303, the scan position information is changed to the scan positions p0 and q0 of the reference plate for the normal copy mode by the scan position information changing means (step S30).
5). Next, based on the set scan position information,
The shading correction unit 302 performs a shading correction value change process (Step S306). More specifically, as shown in the flowchart of FIG. 10, after the CCD sensor 14 and the exposure lamp 12 are turned on (step S401), the image reader control unit 100 sets a reference plate for calculating a shading correction value therein. The scanner 11 is moved to the black reference plate on the back side of the platen 16 based on the scan position information (step S402). At this time, the scan position information p includes the reference plate P for the generation mode.
When the position information indicating the scan position p1 is stored, the scanner 11 is moved to the position of the black reference plate P1 for the generation mode. When the position information indicating the scan position p0 of the reference plate P0 is stored, the scanner 11 is moved to the position of the black reference plate P0 for the normal copy mode. After the movement, the scanner 1
The black level of the black reference plate read by one CCD sensor 14 is detected as Vp (step S403). The detected black level Vp is equal to the internal black-side reading reference value a0, and the shading correction unit 302
The offset adjustment value of the CCD sensor 14 as output from is obtained, and that value is stored (step S404).

Similarly, the image reader control unit 100
The scanner 11 is moved to the white reference plate (Step S40)
5). At this time, if position information indicating the scan position q1 of the generation mode reference plate Q1 is stored in the scan position information, the scanner 11 is moved to the position of the generation mode white reference plate Q1. Similarly, when the scan position information stores the position information indicating the scan position q0 of the reference plate Q0 for the normal copy mode, it is moved to the position of the white reference plate Q0 for the normal copy mode. After the movement, the white level of the black reference plate read by the CCD sensor 14 of the scanner 11 is detected as Vq (step S406), and the detected white level Vq is equal to the internal white-side reading reference value b0. A gain adjustment value of the CCD sensor 14 that is output from the shading correction unit 302 based on the value is obtained, and the obtained value is stored (step S407). The offset adjustment value and gain adjustment value obtained as described above are
When the reference plate read by the CCD sensor 14 is a reference plate having a narrow range width for the generation mode, the value becomes such that the narrow range width becomes 256 gradations. Similarly, when the reference plate read by the CCD sensor 14 is a reference plate for the normal copy mode, the value is such that a range width wider than that of the generation mode is set to 256 gradations.

After that, the image reader control unit 100
The scanner 11 is moved to the home position, and the exposure lamp 12
Is turned off (step S408). Thus, the shading correction value change processing ends. Next, as in FIG. 6 of the first embodiment, a pre-scan process, a sensor input process,
A process control operation or the like is performed (step S307)
To step S309), and a copy process is performed (step S309).
310). In the copying process, the CCD adjusted by the offset adjustment value and the gain adjustment value obtained earlier
The output value from the sensor 14 is used. The output value is A /
After D conversion, shading correction, density conversion, color correction processing, MTF correction processing, and the like, the data is sent to the printer unit as print data. If the number of copies is plural, the copying process is repeated and the process is terminated (step S
311).

As described above, the digital full-color copying machine of the present embodiment has two types of reference plates for normal copy mode and reference plates for generation mode as reading reference plates for changing shading correction values. Yes,
When an instruction of the generation mode is received from the operator, the shading correction unit calculates an offset adjustment value and a gain adjustment value for skipping the low-density part and the high-density part of the document using the reading reference plate for the generation mode. Since the shading correction is performed using the value, it is possible to perform a copy in which the correction for skipping the low-density and high-density portions of the hard copy is performed without reducing the actual number of gradation reproduction steps.

In this embodiment, the shading correction value changing process is performed before the pre-scan, but the present invention is not limited to this. For example, the shading correction value changing process may be performed prior to each copy operation in step S310. In addition, since it takes time to move the scanner 11 between the black reference plate and the white reference plate for each copy operation, only one of them may be used. (3) Embodiment 3 The shading correction unit in the digital full-color copying machine according to Embodiments 1 and 2 receives a generation mode instruction from the operator from the operation panel 18 and receives a generation mode instruction. Although the shading correction for the generation mode is performed, in the third embodiment, it is determined whether or not the original mode is set by determining whether or not the document has a specific reference pattern created in advance. Judgment is made, and in the case of the generation mode, shading correction for the generation mode is performed.

The overall configuration of the copying machine according to the present embodiment is substantially the same as that of the first embodiment, and an image signal processing unit which is a different component from the first embodiment will be described. (3-1) Image Signal Processing Unit FIG. 11 is a block diagram of the image signal processing unit 700 according to the present embodiment. In this figure, components denoted by the same reference numerals as those in FIG. 4 are the same components, and detailed description thereof will be omitted.

The reference pattern discriminating unit 701 receives the data read by the CCD sensor 14 from the shading correction unit 302 at the time of pre-scanning, and an encoded reference pattern indicating a machine code as shown in FIG. Determine if it exists. FIG. 12 is a diagram showing an example of a reference pattern. For example, a pattern indicating a machine code is Y in a part or the whole of an image area.
(Yellow) It is created in a single color. The reason why the single color Y is used is that it is necessary to make the color inconspicuous to humans so that the image of the original is not damaged as much as possible by applying the reference pattern to the original. If the color is inconspicuous, it is not necessary to limit to a single Y color. The reference pattern determining unit 701 determines whether or not a reference pattern exists based on whether or not the pattern exists at a specific position on the document. If the reference pattern exists, the reference pattern determining unit 701 notifies the reference value changing unit 703 that the reference pattern exists.

Further, the reference pattern determining section 701 also determines which copying machine the original has been copied on the basis of the read data of the reference pattern. More specifically, the reference pattern determination unit 701 has a list of machine codes of a plurality of copiers therein, extracts code data from the read data of the reference pattern, and stores the code data in one of the machine codes. By determining whether the document corresponds to the code, it is determined which copying machine the original has been copied. The determination result is sent to the printer control unit 400, and the printer control unit 4
00 causes the display unit to display a machine code indicating the output source of the document. In addition, the reference pattern determination unit 701 stores data for creating a reference pattern indicating the machine code of the own machine in a copy image at the time of copying.

The shading correction section 702 performs shading correction. At this time, a shading correction value change process is performed prior to the shading correction. Specifically, the reading values Va and Vb of the black reference plate and the white reference plate by the CCD sensor 14 are output from the shading correction unit 702 as values equal to a black-side reading reference value A and a white-side reading reference value B described later. Then, an offset adjustment value and a gain adjustment value of the output voltage of the CCD sensor 14 are obtained. At the time of shading correction, the shading correction unit 702 performs shading correction for each of R, G, and B using the obtained offset adjustment value and gain adjustment value, and then normalizes the data to 8-bit data. Here, the black-side reading reference value A and the white-side reading reference value B are
During normal copying, each of the shading correction units 7
A0 and b0, which are values 02 internally, are used. In addition, in the generation mode, the reference value changing unit 703 described later changes the reading reference values a1 and b1 for the generation mode. The reading reference values a1 and b1 for the generation mode have a relationship of a1 <a0 <b0 <b1 with respect to the reading reference value for normal copying so that the high density portion and the low density portion can be skipped. .

When the reference value changing unit 703 receives the notification that the reference pattern exists from the reference pattern discriminating unit 701, it determines that the current mode is the generation mode, and turns on the internal generation mode flag.
The shading correction unit 702 changes the read reference values a1 and b1 for the generation mode, instead of the read reference values a0 and b0 for the normal copy mode used in the shading correction value change processing. Also, the density converter 3
04 is made to use the density conversion correction value c1 for the generation mode instead of the density conversion correction value c0.

(3-2) Operation of Digital Full-Color Copying Machine The operation of the digital full-color copying machine in the present embodiment will be described with reference to flowcharts shown in FIGS. In FIG. 13, first, the digital full-color copying machine receives various key inputs from the operation panel 18 prior to copying (step S501). The operation panel 18 has, for example, a configuration in which a reference pattern button and a correction disable button are added to the operation panel 18 shown in FIG. The reference pattern button is a button for receiving an instruction as to whether or not to create the reference pattern shown in FIG. 12 on a document at the time of copying, and the correction value change disable button is a button for generation mode even if it is determined that there is a reference pattern. This button is used to accept an instruction not to make a request. When the copy start key is pressed after inputting various keys (step S502), the reference value changing unit 703 sets the reading reference values a0 and b0 for the normal copy mode in the shading correction unit 302, and further sets the density conversion unit 304. The density conversion correction value c for the normal copy mode
0 is set (step S503). Next, the shading correction unit 702 performs a shading correction value change process (step S504). Specifically, as shown in the flowchart of FIG. 14, after the CCD sensor 14 and the exposure lamp 12 are turned on (step S601), the image reader control unit 100 sets the scanner 11 to the black reference on the back side of the platen 16. It is moved to a plate (step S602). After the movement, the black level of the black reference plate read by the CCD sensor 14 is detected as Vp (step S603), and the black level Vp is equal to the black-side reading reference value a0 and is output from the shading correction unit 702. CCD like
The offset adjustment value of the output of the sensor 14 is obtained, and the value is stored (step S604). Similarly, the image reader control unit 100 moves the scanner 11 to the white reference plate (step S605), and the white level Vq of the white reference plate read by the CCD sensor 14 (step S60).
6) A gain adjustment value of the output of the CCD sensor 14 that is output from the shading correction unit 702 is obtained with a value equal to the white-side reading reference value b0, and the obtained value is stored (step S607). After that, the image reader control unit 100 moves the scanner 11 to the home position and turns off the exposure lamp 12 (Step S608). Thus, the shading correction value change processing ends.

Next, the image reader control section 100 performs a pre-scan process for checking the size of the document, the presence or absence of a reference pattern, and the like (step S505). Specifically, FIG.
As shown in FIG.
N (step S701), and no instruction indicating that the correction cannot be changed has not been received in step S501 (step S70).
2) If it is determined that the reference pattern exists in the document (step S703), the reference value changing unit 703 determines that the current mode is the generation mode, and turns on the internal generation mode flag (step S704). . The reference pattern determining unit 701 also determines which copy machine the original has been copied based on the read data of the reference pattern, and sends the determination result to the printer control unit 400. The printer control unit 400 causes the display unit to display a machine code indicating the output source of the document (step S705).

Next, the image reader control unit 100 causes the scanner 11 to detect the size of the document (step S70).
6) Then, the lamp is turned off, and the scanner 11 is returned (step S707). This is the end of the prescan processing. Next, in FIG. 13, if the generation mode flag is ON (step S50).
6) The reference value changing unit 703 includes a shading correction unit 7
02 is replaced with the reading reference values a0 and b0 for the normal copy mode used in the shading correction value changing process.
The reading reference values a1 and b1 for the generation mode are changed (step S507). The density conversion unit 30
4 causes the density conversion correction value c1 for the generation mode to be used instead of the density conversion correction value c0. Then, the shading correction value changing process is performed again by the shading correction unit 702 using the changed generation mode reading reference values a1 and b1 (step S508). Specifically, the processing shown in FIG. 14 is performed, and the reading reference values A1 and B1 use the reading reference values a1 and b1 for the generation mode instead of the reading reference values a0 and b0 for the normal copy mode. Other than that, the description is omitted.

Next, the printer control unit 400 receives various internal environmental sensor inputs, appropriately changes the conditions at the time of image formation by the received various sensor inputs and the process control operation, and then proceeds to a copy process. (Step S509). If an instruction to create a reference pattern has been received in step S501 (step S510), the reference pattern determination unit 701 sets
By outputting the data of the internal reference pattern to the color correction unit 306, the reference pattern shown in FIG. 13 is created at the time of copying (step S511).

In the copying process, shading correction is performed using the offset adjustment value and the gain adjustment value obtained earlier. At this time, if the offset adjustment value and the gain adjustment value previously obtained are those obtained using the reading reference values a1 and b1 for the generation mode, the output data includes a low density portion and a high density portion. The data is skipped. The density conversion is performed using the density conversion correction value for the generation mode. The density data obtained after the density conversion is subjected to color correction processing,
After the MTF correction processing and the like, the data is sent to the printer unit as print data, and the image is printed (step S51).
2). If the number of copies has been specified, the copying process is repeated and the process is terminated (step S513).

As described above, according to the present embodiment, the shading correction is performed using the generation reference value if the document has a reference pattern without receiving an instruction from the operator whether or not the mode is the generation mode. Can be. Further, since the reference pattern attached to the document is created in a single Y color, it is inconspicuous to a person and does not impair the image of the document.

In the present embodiment, based on the machine code determined by the reference pattern determining unit 701, the machine code indicating the output source of the document is only displayed on the display unit. A configuration may be provided in which a plurality of reading reference values corresponding to the obtained machine code are stored in advance, and the reading reference value corresponding to the machine code is set in the shading correction unit 702. (4) Embodiment 4 In the digital full-color copying machine according to Embodiment 3 described above, it is determined whether or not the original mode is set to the generation mode by determining whether or not there is a specific reference pattern created in advance in the document. Judgment is made, and in the generation mode, shading correction is performed using the correction value for the generation mode.

On the other hand, the present embodiment is the same as the third embodiment in that it is determined whether or not to switch to the generation mode by determining whether or not a document has a reference pattern. The shading correction in the present embodiment is different in that the density of the reference pattern is detected, and the correction value for generation is determined using the detected value.

Therefore, the configuration of the entire copying machine according to the present embodiment is almost the same as that of the third embodiment, and the image signal processing unit which is a different component will be described. (4-1) Image Signal Processing Unit FIG. 16 is a block diagram of the image signal processing unit 800 according to the present embodiment. In this figure, components denoted by the same reference numerals as those in FIGS. 4 and 16 are the same components, and detailed description thereof will be omitted.

The reference value determining unit 801 receives original read data at the time of pre-scanning, and determines whether or not a reference pattern exists at a predetermined position on the original. If a reference pattern exists in the document, the density of the reference pattern is detected, and the detected value is used to determine the shading correction unit 70.
2 determines the reading reference value to be used. Here, the reference pattern used in the present embodiment is, for example, four colors (C,
(M, Y, BK) solid patterns formed at predetermined positions outside the image area of the document. Reference value determination unit 80
The determination of the reading reference value performed by 1 is performed, for example, as follows. The detection value of the density of each color of the reference value is averaged, and the value is determined as the black-side reading reference value Ra used by the shading correction unit 702. Further, the detection value of the base of the reference pattern, that is, the detection value of the blank portion of the sheet is determined as the white-side reading reference value Rb used by the shading correction unit 702.

Further, the density conversion correction value C used by the density conversion unit 304 is determined by the reference value determination unit 801 as follows, for example. The reference value determination unit 801
Has a table as shown in FIG.
The table stores a plurality of sets 171 of a black-side reading reference value Ra and a white-side reading reference value Rb, and a plurality of density conversion correction values 172 corresponding to the set on a one-to-one basis. The reference value determination unit 801 determines the density conversion correction value C using the determined black side reading reference value Ra, white side reading reference value Rb, and the table.

The reference value changing unit 802 converts the black-side reading reference value and the white-side reading reference value used by the shading correction unit 702 into the black-side reading reference value Ra and the white-side reading reference value determined by the reference value determining unit 801. Rb, and similarly, the density conversion correction value used by the density conversion unit 304 is changed to the density conversion correction value C determined by the reference value determination unit 801. If the reference value determination unit 801 determines that the specific reference pattern does not exist in the document, the reference value for black side and the reference value for white side are changed to the read reference values a0 and b0 for normal copy, and the density is changed. The conversion correction value C is also changed to the reading reference value c0 for normal copying.

(4-2) Operation of Digital Full-Color Copying Machine The operation of the digital full-color copying machine according to the present embodiment will be described with reference to flowcharts shown in FIGS. First, similarly to the flow of FIG. 13 of the third embodiment, key input processing and various reference values a0, b0,
c0 is set (steps S801 to S80)
3) Next, a shading correction value change process is performed (step S804). The shading correction value changing process is the same as the flow shown in FIG. 14 of the third embodiment, and thus the description will be omitted.

Next, a prescan process is performed (step S805). The pre-scan processing is specifically described in FIG.
9, the first half performs processing such as detection of a reference pattern and setting of a generation mode flag, similarly to the flow of FIG. 15 of the third embodiment (steps S901 to S904). When the generation mode flag is turned on, the reference value determination unit 80
1 detects the density of the reference pattern (step S90)
5) Determine reference values Ra, Rb, and C from the detection result.
The reference value changing unit 802 has already
The reference value set in the density conversion unit 304 or the density conversion unit 304 is changed to the determined reference value (step S906). Thereafter, the image reader control unit 100 detects the size of the document and returns the scanner (step S90).
7, Step S908). This is the end of the prescan processing.

Hereinafter, in FIG. 18, step S807 will be described.
Subsequent processing is the same as the processing after step S506 in FIG. 13, and a description thereof will be omitted. As described above, according to the present embodiment, if the document has a reference pattern, it can be determined that the current mode is the generation mode, and the reading reference value used in the generation mode is the density value of the reference pattern attached to the document. Is detected, and a reading reference value suitable for each document is used.

The reference value determination unit 801 according to the fourth embodiment determines the density conversion correction value C using a table, but is not limited to this, and calculates the density conversion correction value C using the following equation. You may. C = (Ra-Rb) / R0 where R0 is a predetermined reference coefficient.

In this embodiment, the high-density reading reference value and the low-density reading reference value are changed. However, the present invention is not limited to this, and only one of them may be changed. Further, the detection of the reference pattern in the present embodiment may be performed at the start of the copy operation instead of at the time of the pre-scan. In this case, it is necessary to position the document such that the reference pattern attached to the document is at a predetermined position on the document table. However, since it is not necessary to perform prescanning, it is possible to speed up the first copy. There is an advantage.

In the second, third, and fourth embodiments, the shading correction is performed by correcting the output value of the CCD sensor 14 before the data is digitally processed. Similarly, shading correction may be performed using digitally processed data. In the first embodiment, the shading correction is performed using digitally processed data.
The present invention is not limited to this, and may be performed by adjusting the output before or during A / D conversion as described below.

The output before the A / D conversion is adjusted, for example, by adjusting the analog voltage from the CCD sensor input to the A / D converter. Specifically, as in the second, third, and fourth embodiments, the shading correction unit controls the input analog voltage so that the output from the shading correction unit becomes equal to the changed reading reference value. By changing the offset adjustment value and the gain adjustment value.

On the other hand, the output adjustment at the time of A / D conversion is performed by A / D conversion.
This is performed by changing the data value output from the A / D converter with respect to the analog voltage input to the D converter. Specifically, the output data value is changed so that the output from the A / D conversion unit becomes a value equal to the changed reading reference value. FIG. 20 shows that the output value from the A / D conversion unit is a value in which the high-density part and the low-density part are skipped by offset adjustment and gain adjustment. Here, RB and RW are reflectance data of the black reference plate and the white reference plate, respectively, and a0 and b0 are a black-side reading reference value and a white-side reading reference value in normal copying (Normal mode), respectively. is there. Similarly, a1 and b1 are a black-side reading reference value and a white-side reading reference value in the generation mode (G mode).

According to the figure, during normal copying, the output is offset-adjusted and gain-adjusted so that the input reflectance data of RB and RW are output as a0 and b0. At the time of generation copy, RB, RW
Is output as a1 and b1.
It can be seen that the output is adjusted for offset and gain.

[0073]

As described above, according to the present invention, when an original is determined to be a specific original, the low-density portion and the high-density portion of the read data are skipped using the reading reference value for the specific original. For example, since the data is standardized to 8-bit data, skipping the low-density part and high-density part of the data after the standardization as in the prior art does not cause a decrease in the number of actual gradation reproduction steps, thereby reducing the A copy can be made by performing a correction for skipping a low density portion, a high density portion, or both. Further, since this correction can be performed only by changing the reading reference value, it can be easily realized.

Further, the document discriminating means performs the pre-scan,
Or, at the start of scanning, a pattern detection unit that determines that the reference pattern is attached to the original is provided, and it is determined that the original is a specific original by detecting that the reference pattern is attached. It is possible to quickly and easily make a correction by skipping the low-density portion, the high-density portion, or both of the specific document.

The document discriminating means is a receiving unit for receiving an instruction from the operator as to whether the document is a specific document. When the receiving unit receives an instruction indicating that the document is the specific document, Since the reading reference value is changed to the reading reference value for the specific document, it is possible to make a copy on the document intended by the operator by performing correction for skipping the low density portion, the high density portion, or both.

The reading reference value changing means determines the reading reference value in accordance with the reading value of the solid reference pattern, and normalizes the reading reference value by using the determined reading reference value. A copy can be made by performing a correction for skipping a low-density portion, a high-density portion, or both by using a certain reading reference value. Further, since the pattern determined by the document discriminating means is a pattern written in a color inconspicuous to a viewer on a part or the front of the image area, even if the pattern is added, the image of the document is not damaged. It can be determined that the original is a specific original.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an entire digital full-color copying machine according to a first embodiment.

FIG. 2 is a block diagram of a part of a control system in the digital full-color copying machine.

FIG. 3 is a block diagram of another part of the control system.

FIG. 4 is a block diagram of an image signal processing unit in the control system.

FIG. 5 is an external view of an operation panel in the digital full-color copying machine.

FIG. 6 is a flowchart showing an operation in the digital full-color copying machine.

FIG. 7 is a flowchart showing a shading correction coefficient calculation process in the flowchart of FIG. 6;

FIG. 8 is an external view of a platen having a white reference plate and a black reference plate for a generation mode in a digital full-color copying machine according to a second embodiment.

FIG. 9 is a flowchart showing the operation of the digital full-color copying machine.

FIG. 10 is a flowchart showing a shading correction value changing process in the flowchart of FIG. 9;

FIG. 11 is a block diagram of an image signal processing unit in a digital full-color copying machine according to a third embodiment.

FIG. 12 is a diagram showing a reference pattern used in the digital full-color copying machine.

FIG. 13 is a flowchart showing the operation of the digital full-color copying machine.

FIG. 14 is a flowchart showing a shading correction value changing process in the flowchart of FIG. 13;

FIG. 15 is a flowchart showing a pre-scan process in the flowchart of FIG.

FIG. 16 is a block diagram of an image signal processing unit in a digital full-color copying machine according to a fourth embodiment.

FIG. 17 is a diagram showing a table used by a reference value determination unit of the image signal processing unit.

FIG. 18 is a flowchart showing an operation in the digital full-color copying machine.

FIG. 19 is a flowchart showing a pre-scan process in the flowchart of FIG. 18;

FIG. 20 is a diagram showing that an output value from an A / D conversion unit is a value in which a high-density part and a low-density part are skipped by offset adjustment and gain adjustment.

[Explanation of symbols]

 Reference Signs List 10 Image reader unit 11 Scanner 12 Exposure lamp 14 CCD sensor 16 Platen 17 Reference plate 18 Operation panel 20 Printer unit 21 Photoconductor drum 22 Print head unit 41 Control unit 81 Platen 82 Reference plate 100 Image reader control unit 200 Image control unit 300 Image Signal processing unit 301 A / D conversion unit 302 Shading correction unit 303 Reference value change unit 304 Density conversion unit 305 Area determination unit 306 Color correction unit 307 MTF correction unit 308 Moving unit 309 Color balance unit 400 Printer control unit 500 Print head control unit 700 image signal processing unit 701 reference pattern discriminating unit 702 shading correction unit 703 reference value changing unit 800 image signal processing unit 801 reference value determining unit 802 reference value changing unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kentaro Katori 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Masahiro Mitsuzaki Azuchi-cho, Chuo-ku, Osaka, Osaka 2-3-3, Osaka International Building Minolta Co., Ltd. (72) The inventor Katsuyuki Hirata 2-3-13, Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Co., Ltd.

Claims (5)

[Claims] An original is read, and the read data is standardized based on a high-density side reading reference value and a low-density side reading reference value so as to have a predetermined number of gradations. An image forming apparatus that forms an image based on the document, a document determining unit that determines whether the document is a specific document, and a low-density side reading reference value for a specific document in addition to the normal reading reference value. High-density side reading reference value for original,
Or when both of the reading reference values are provided and the document determining unit determines that the document is a specific document, the reading reference value for the specific document is used instead of the normal reading reference value. An image forming apparatus, comprising: a reading reference value changing unit for normalizing the data. 2. The apparatus according to claim 1, wherein the original discriminating means includes a pattern detecting unit that detects that a pattern indicating that the original is a specific original is attached to the original at the time of pre-scanning or at the start of scanning. 2. The image forming apparatus according to claim 1, wherein the attachment determines that the original is a specific original. 3. The document discriminating unit is a receiving unit that receives an instruction from an operator as to whether or not the document is a specific document. The reading reference value changing unit receives an instruction that the document is a specific document. 2. The image forming apparatus according to claim 1, wherein when received by the receiving unit, normalization is performed by using the reading reference value for the specific document instead of the normal reading reference value. 3. 4. The method according to claim 1, wherein the pattern is one or more solid reference patterns formed outside the image area of the document, and the reading reference value changing unit reads the reference value according to the reading value of the reference pattern. 3. The image forming apparatus according to claim 2, wherein the image forming apparatus determines the image data and uses the determined reading reference value to perform normalization. 5. The pattern is a pattern written in a color that is inconspicuous to a viewer on a part or the front of an image area, and the document discriminating means determines that the pattern is attached to a document. 3. The image forming apparatus according to claim 2, wherein the detection determines that the document is a specific document.