JPH09107487A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the image forming device which obtains a satisfactory color reproducibility with various document types and color materials by an easy method. SOLUTION: A document picture is read as picture signals of plural colors by a scanner 401 or the like, and read picture signals are transformed to gray level image signals by a gray level processing part 411, and an image is formed by a printer 412. In this process, a hue discrimination circuit 422 classifies RGB color image signals into prescribed areas and changes matrix coefficient values of a color conversion/UCR circuit 406 to perform operation and correction of the hue. In this correction, for example at least one of the gray level transformation characteristic of read signals and the transformation characteristic from read signals subjected to gray level transformation to image signals for formation of a color image is changed in accordance with the read signal obtained by reading a designated position of a first document and the read signal obtained by reading a designated position of a second document.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to a digital type copying machine, printer and fax machine.
The present invention relates to an image forming apparatus using a color adjustment method such as

[0002]

2. Description of the Related Art Conventionally, in a digital color copying machine,
When forming a full-color image in the process of copying the original,
The original is an RGB three-color CCD (Charge Coupled Device)
It is common to read in. Not only the digital method, but one of the basic performance required for color copiers
One of them is color reproducibility that is faithful to the original. However, there are various types of paper, including not only plain paper originals, but also photographic paper formed by the silver salt photographic method, thermal transfer paper, etc. It becomes a manuscript. Also, as a color material, printing ink, toner,
There are various coloring materials such as colored pencils, crayons, felt-tip pens, and highlighters.

In many cases, a color copying machine is set so as to obtain good color reproducibility with respect to a printed document. In the set state, a document other than the printed document such as photographic paper is copied. In that case, the problem that the color reproducibility deteriorates may occur. This is due to the metamerism of the manuscript,
The difference in the spectral reflection characteristics and the spectral transmission characteristics of the filter used in the CCD or the spectral sensitivity of the CCD (FIG. 21) are caused by the difference in the type of the original and the color material such as the printed original and the printing paper. As an example, the spectral reflectance a of a silver halide photographic (printing paper) document, the spectral reflectance b of a document copied with the image processing parameters set according to the print document, and the color of the copy for the photographic document with the naked eye. FIG. 22 shows the spectral reflectance c in the case where the color is matched with the state as seen in FIG.

As seen in FIGS. 21 and 22, R
Spectral reflectances a and b intersect near the peak value d of the spectral transmittance of each CCD filter of GB, and CC
It is expected that the RGB outputs of D are the same for the spectral reflectances a and b. However, in reality, this coincidence is based on the result obtained by multiplying the spectral characteristics of the light source of the copying machine, the spectral reflectance of the original, and the spectral sensitivity of the CCD, and integrating over all wavelengths. On the other hand, when viewed with the naked eye, the result is obtained by integrating the light source at the place where the manuscript is viewed, the spectral reflectance of the manuscript, and the spectral sensitivity of the human eye for all wavelengths. As a result, the obtained spectral reflectances are significantly different between the spectral reflectances a and b, indicating that the color reproduction is poor. As a fundamental method for improving the poor color reproducibility due to the difference in the document type, it is necessary to determine the document type.

For example, Japanese Patent Laid-Open No. 63-18713 as a prior art example 1
There is a method disclosed in No. 9 “Color manuscript classification method”. According to the document type classification method of this conventional example, the reflected light of a color document is measured using two types of sensors having sensitivity peaks at different wavelengths within the wavelength range of one of the three primary color lights. By comparing the obtained two types of measured values, the color original is classified into at least a photographic original and a printed original.

A conventional example 2 is disclosed in Japanese Patent Laid-Open No. 63-125057 "Color Image Processing Device". The image processing apparatus of the conventional example performs color processing such as various color conversions for each area. That is, when it is determined that the color represented by the read image data is the color before conversion designated by the conversion color designating means, the color before conversion is the color at the designated position on the original stored in the storage means. Convert to the target color after conversion. By this conversion, a plurality of desired colors are stored in advance in the memory, and compared with the one in which the selected color is converted,
It is possible to convert and output the color at the position specified on the original. Therefore, it is possible to perform conversion into a color other than the predetermined color stored in the memory. Furthermore, even if the color after color conversion is not actually output, conversion is performed with the original color as the target color, so that the color conversion that the user desires can be performed.

The method of the above-mentioned conventional example 1 is one of the theoretical solutions. However, this method is not generally used in color copiers at present because of cost and mechanical complexity.

Further, the apparatus disclosed in Conventional Example 2 is one method for converting one color into another color. However, as described above, due to the metamerism of the original, the color specified as the color after color conversion may be reproduced in a completely different color from the specified color depending on the type of original such as a thermal transfer original. is there. For example, when a color conversion coefficient for a print document is set and a silver salt photographic printing paper document, a thermal transfer document, or a document created with pastel crayons is specified as the target color, it will differ depending on the color (hue). Set to color. Even when the printing or printing paper original mode is set, different colors may be reproduced depending on the printing ink used, the color material of the printing paper, or the difference in the spectral reflectance of the surface. is there.
For these reasons, the following conventional example 3 is generally used in the color copying machine.

In the conventional example 3, the copying machine is provided with image processing parameters such as a printing original, a printing paper original, and color conversion coefficients combined with each other as a printing original / printing paper original mode, and the operation section of the copying machine is used. This is a method that allows selection.

[0010]

However, in the above-mentioned conventional example 3, even if good color reproducibility is obtained by the above-mentioned method with respect to the printing original / printing paper original, other original types, for example, When a full-color original created by the thermal transfer method or an original created by pastel crayon or the like is copied, a phenomenon similar to the phenomenon described in other conventional examples may occur. Therefore, it may be reproduced in a completely different color from the original.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of obtaining good color reproducibility by a simple method even with various kinds of originals and coloring materials.

[0012]

In order to achieve the above object, the image forming apparatus of the present invention comprises an image reading means for reading an image of a document as an image signal of a plurality of colors, and a means for gradation conversion of the read image signal. A means for forming a color image using color materials of a plurality of colors; a means for converting the gradation-converted image signal into an image signal for forming a color image; and a means for designating a reading position of a document. Having a first
Of the read signal obtained by reading the specified position of the original document and the read signal obtained by reading the specified position of the second original document It is characterized in that at least one of the conversion characteristics of means for converting a signal into an image signal for forming a color image is changed.

The designated position of the first original and the second position
A plurality of designated positions of the original, and an image of at least one of the first original and the second original is formed by the printing ink, and the image forming apparatus further specifies the original formed by the printing ink. It is better to have the means of In addition,
An image of at least one of the first original and the second original is formed by a silver salt photographic method, and the image forming apparatus may further include a unit for specifying a printing paper used in the silver salt photographic method.

Further, the image forming apparatus has a color patch generating means and a means for outputting the color patch generated by the color patch generating means to the transfer material, and either the first original document or the second original document is provided. One may be the output image of the color patch. Furthermore, the image forming apparatus has a color patch generation unit and a unit that outputs the color patch generated by the color patch generation unit to a transfer material.
One of the first document and the second document may be the output image of the color patch, and the other may be the copied image with toner.

The image of at least one of the first original document and the second original document is formed by toner, and the image forming apparatus may further have a means for specifying that the original document is a toner original document.

Further, the image forming apparatus may have a selection means for selecting whether the first original and the second original are plain paper. Furthermore, it is preferable to switch the classification means for classifying the color of the image signal into any one of a plurality of predetermined hues and the correction coefficient used in the predetermined calculation according to the classification by this classification means. Furthermore, registration means for registering image parameters, registration name setting means for setting a registration name by this registration means, display means for displaying the set name, and registration for selecting registration contents based on the displayed name. And a selection unit.

[0017]

Therefore, according to the image forming apparatus of the present invention,
The image of the original is read as an image signal of a plurality of colors, the read image signal is subjected to gradation conversion, and a color image is formed by using color materials of a plurality of colors. The gradation-converted image signal is converted into an image signal for forming a color image, and the reading position of the original is designated. From the read signal obtained by reading the specified position of the first original and the read signal obtained by reading the specified position of the second original, the gradation conversion characteristic of the read signal or the gradation conversion is performed. At least one of the conversion characteristics for converting the read signal into an image signal for forming a color image is changed. Therefore,
By changing this characteristic, the color tone of the read image signal
It is possible to make adjustments for each designated position.

[0018]

Embodiments of the image forming apparatus according to the present invention will now be described in detail with reference to the accompanying drawings. 1 to 20, there is shown an embodiment of the image forming apparatus of the present invention.
The following embodiments will be described when the image forming apparatus of the present invention is applied to an electrophotographic copying machine (hereinafter simply referred to as a copying machine).

An outline of the mechanism of the copying machine main body 101 of the embodiment will be described with reference to the mechanism diagram shown in FIG. Copier body 10
Φ120 [m as an image carrier placed in the center of 1
m] around the organic photoconductor (OPC) drum 102, the surface of the photoconductor drum 102 is charged by a charger 103, and the surface of the uniformly charged photoconductor drum 102 is irradiated with semiconductor laser light. A laser optical system 104 that forms an electrostatic latent image, a black developing device 105 that supplies toner of each color to the electrostatic latent image to develop it, and obtains a toner image for each color, and three colors of yellow Y, magenta M, and cyan C. Developing devices 106, 107, 108, an intermediate transfer belt 109 that sequentially transfers toner images of respective colors formed on the photosensitive drum 102, a bias roller 110 that applies a transfer voltage to the intermediate transfer belt 109, and a photosensitive member after transfer. Body drum 102
Cleaning device 1 for removing toner remaining on the surface of
11, a charge removing unit 112 for removing electric charges remaining on the surface of the photosensitive drum 102 after the transfer, and the like are sequentially arranged.

The intermediate transfer belt 109 is a transfer bias roller 113 for applying a voltage for transferring the transferred toner image to the transfer material, and a belt for cleaning the toner image remaining after the transfer to the transfer material. A cleaning device 114 is provided. Intermediate transfer belt 1
Transport belt 115 for transporting the transfer material separated from 09.
A fixing device 116 that heats and pressurizes the toner image to fix the toner image is disposed at the end of the fixing device 116, and a paper discharge tray 117 is attached to the outlet of the fixing device 116.

On the upper part of the laser optical system 104, a contact glass 118 as an original placing table arranged on the upper part of the copying machine main body 101, an exposure lamp 119 for irradiating the original on the contact glass 118 with scanning light, and from the original. The reflected light is guided to the imaging lens 122 by the reflection mirror 121, and is incident on the image sensor array 123 composed of a CCD which is a photoelectric conversion element. The image signal converted into an electric signal by the image sensor array 123 controls the laser oscillation of the semiconductor laser in the laser optical system 104 through an image processing device (not shown).

Next, the control system built in the copying machine will be described. As shown in FIG. 2, the control system includes a CPU 130 that is a main control unit, and a predetermined ROM 131 and a non-volatile RAM 132 are attached to the CPU 130. Further, in the CPU 130, a laser optical system controller 134, a power supply circuit 135, an optical sensor 136, a toner concentration sensor 137, an environment sensor 138, a photoconductor surface potential sensor 139, and a toner replenishing circuit 140 are provided to the CPU 130 via an interface I / O 133. , And the intermediate transfer belt drive unit 141 are connected to each other. The laser optical system controller 134 controls the laser optical system 104.
Of the developing device 105, 106, and the power supply circuit 135 applies a predetermined charging discharge voltage to the charging charger 113.
A developing bias having a predetermined voltage is applied to 107 and 108, and a predetermined transfer voltage is applied to the bias roller 110 and the transfer bias roller 113.

The optical sensor 136 is used for the photosensitive drum 10.
2 includes a light emitting element such as a light emitting diode and a light receiving element such as a photo sensor, which are arranged in the vicinity of the area after the transfer of 2, and the toner adhesion amount and the background in the toner image of the detection pattern latent image formed on the photoconductor drum 102. The amount of toner adhered to each part is detected for each color,
The so-called residual potential after the charge removal of the photoconductor is detected.

The detection output signal from the photoelectric sensor 136 is applied to a photoelectric sensor control unit (not shown).
The photoelectric sensor control unit obtains the ratio of the toner adhesion amount in the detection pattern toner image and the toner adhesion amount in the background portion, compares the ratio value with a reference value, and detects the fluctuation of the image density. The control value of 137 is corrected.

Further, the toner density sensor 137 is provided in each of the developing devices 105 to 108.
The toner density is detected based on the change in the magnetic permeability of the developer existing inside. The toner concentration sensor 137 compares the detected toner concentration value with a reference value, and when the toner concentration falls below a certain value and a toner shortage state occurs, a toner replenishment signal having a magnitude corresponding to the shortage amount is supplied. Toner supply circuit 1
It has a function of applying to 40.

The potential sensor 139 detects the surface potential of the photoconductor 102, which is an image carrier. The intermediate transfer belt drive unit 141 controls driving of the intermediate transfer belt.

A developer containing black toner and carrier is accommodated in the black developing device 105, which is agitated by the rotation of the developer agitating member 202, and on the developing sleeve 201, the developer regulating member 202 sleeves the sleeve. Adjust the amount of developer pumped up. The supplied developer is magnetically carried on the developing sleeve 201 and rotates as a magnetic brush in the rotating direction of the developing sleeve 201.

Next, the image processing section will be described with reference to the block diagram of FIG. In FIG. 3, 401 is a scanner,
Reference numeral 402 is a shading correction circuit, 403 is an RGBγ correction circuit, 404 is an image separation circuit, 405 is an MTF correction circuit, 406 is a color conversion-UCR processing circuit, 422 is a hue determination circuit, 407 is a scaling circuit, and 408 is image processing ( Create) circuit, 409 is an MTF filter, 410 is a γ correction circuit, 411 is a gradation processing circuit, 421 is a color patch generation means, and 412 is a printer.

The original to be copied is the color scanner 401.
Are separated into R, G, and B and read. The shading correction circuit 402 corrects unevenness of the image pickup device, unevenness of illumination of the light source, and the like. In the RGBγ correction circuit 403, the read signal from the scanner is converted from the reflectance data to the brightness data. The image separation circuit 404 determines the character portion and the photograph portion, and determines the chromatic color and the achromatic color.
The MTF correction circuit 405 corrects the deterioration of the MTF characteristics of the input system, particularly in a high frequency range. The color conversion-UCR processing circuit 406 corrects the difference between the color separation characteristic of the input system and the spectral characteristic of the color material of the output system, and the color material YM required for faithful color reproduction.
It is composed of a color correction processing unit for calculating the amount of C and a UCR processing unit for replacing a portion where three colors of YMC overlap with Bk (black). The color correction process can be realized by a matrix calculation as in the following formula (1).

[0030]

(Equation 1)

The matrix coefficient a _ij of the equation (1) is determined by the spectral characteristics of the input system and the output system (color material). Here, the first-order masking equation is taken as an example, but color correction can be performed more accurately by using a second-order term such as B ² and BG or a higher-order term. The UCR process can be performed by calculating using the following equation (2).

[0032]

(Equation 2)

In the equation (2), the symbol α is a coefficient that determines the amount of UCR, and when α = 1, 100% UCR processing is performed. The value of the coefficient α may be a constant value. For example, when the coefficient α is close to 1 in the high density portion and close to 0 in the highlight portion, the image in the highlight portion can be smoothed.

The hue determination circuit 422 calculates RGB, YM from the input RGB image signal data according to a predetermined arithmetic expression.
Classification is performed for each hue region such as C, and the matrix coefficient a _ij of the color conversion / UCR circuit 406 is classified according to the classified result.
Is changing the value of. Further, the arithmetic expression may be changed for each hue region, or the Neugebauer equation may be used.

The scaling circuit 407 performs vertical and horizontal scaling, and the image processing (create) circuit 408 performs repeat processing. The MTF filter 409 performs processing for changing the frequency characteristic of the image signal such as edge enhancement and smoothing according to the user's preference such as a sharp image or a soft image. The γ correction circuit 410 corrects the image signal according to the characteristics of the printer. In addition, the background can be removed at the same time. The gradation processing circuit 411 performs dither processing or pattern processing.

Further, interfaces I / F 413 and 414 are provided for processing the image data read by the scanner 401 with an external image processing device or the like, and outputting the image data from the external image processing device with the printer 412. ing. C for controlling the above image processing circuit
The PU 415, the ROM 416, and the RAM 417 are BU
It is connected in S418. The CPU 415 is connected to the system controller 419 through the serial I / F, and commands from the operation unit (FIG. 4) and the like are transmitted.

The color patch generating means 421 generates a color patch (FIG. 5) consisting of three colors of YMC or four colors of YMCK. In this color patch, the color tone is changed by sequentially changing the density of YMC and changing each combination. This changes the K (Black) component according to the UCR amount described above.

The operator can specify the mode and other processing conditions from the switches on the operation unit (FIG. 4). In the copy mode using the internal scanner, the scanner 401 is operated and the original is sequentially color-separated into R, G, and B and read, and the image processing unit performs the above-described shading correction, MTF correction, γ correction, color correction, and UCR processing. Is performed, and multi-valued processing is performed by gradation processing.

FIG. 4 is a bird's-eye view of the operation unit. The contact glass 501 on which the original is placed, the liquid crystal touch panel 502,
When a display editor 503 (hereinafter abbreviated as an editor) of liquid crystal display and various hard keys (switches) are pressed to depress the read key 504, the scanner reads an image of the original and displays it on the editor screen 503. On the editor screen 503, it is possible to specify an arbitrary position by enlarging an arbitrary position on the document or moving a cursor.

By selecting a command (not shown) on the operation unit screen, it is possible to read an arbitrary position of the document specified on the editor screen 503 with a scanner and display the read data.

A block diagram of the laser modulation circuit is shown in FIG. The writing frequency is 18.6 [MHz], and the scanning time for one pixel is 53.8 [nsec]. 8-bit image data can be subjected to γ conversion by a look-up table (LUT) 451.

The pulse width modulation circuit (PWM) 452 converts the 8-bit image signal into 4-value pulse width based on the higher 2-bit signal, and the power modulation circuit (PM) 453 converts the lower 6 bits to 64-value. Power modulation is performed, and the laser diode (LD) 454 emits light based on the modulated signal. The emission intensity is monitored by the photo detector (PD) 455, and correction is performed for each dot. The maximum intensity of the laser light is 8 bits (25
6 steps).

The light emission start timing of the laser light of the image signal subjected to the dither processing as described above is set so that the exposure distributions of two pixels are close to each other, as shown in FIGS. By using the pulse width modulation method, this pattern is shown in FIG.
As shown in c and d, the line pattern is continuous in the sub-scanning direction, and the width of this line pattern can form a latent image approximately proportional to the sum of N ₁ + N ₂ . As a result, the detection output of the optical sensor 136 has an advantage that the detection output has a good linearity with respect to the image signal as shown in FIG.

This varies depending on the beam diameter, and the beam diameter in the main scanning direction is 90% or less, preferably 80% with respect to the size of one pixel. This beam diameter is defined as the width when the intensity of the beam at rest is attenuated to 1 / e ² with respect to the maximum value. For example, 400DPI, 1 pixel 63.5μm
The desirable beam diameter in is less than 50 μm.

In the copying machine 101, as image quality modes, image processing parameters are set in advance so that optimum color reproducibility and image quality can be obtained when a print original, a photographic paper original, or a toner original is copied. There is.

The outline of these image processing parameters will be described. The print original that is not gravure print expresses shading depending on the size of the dot area ratio. Scanning these halftone dots with a scanner causes moire. In order to reduce the occurrence of this moire, the MTF correction circuit 405 of the image processing unit is
Smoothing process is performed, and the color conversion / UCR processing circuit 406 performs the color conversion characteristic matching the color reproduction characteristic of the printing ink.
The γ correction circuit 410 performs γ conversion.

On the other hand, moire does not occur in the silver halide photographic printing paper original, but in order to reduce the noise component of the scanner, the MTF correction circuit 405 performs a smoothing process weaker than that for the printing original to perform color conversion / color conversion. The UCR processing circuit 406 performs color conversion characteristics matching the spectral reflection characteristics of the printing paper, and the γ correction circuit 410 performs γ conversion.

Similarly, the toner original is subjected to the smoothing processing weaker than that for the print original at the MTF correction time 405,
The color conversion / UCR processing circuit 406 performs color conversion characteristics according to the spectral reflectance characteristics of the toner, and the γ correction circuit 410 performs γ conversion according to the toner original.

The toner original may be a copy of the original or may not exist when used as a printer. When a document is copied, the contrast is often stronger than that of the document.
The conversion characteristic is set so that the contrast is not emphasized. Regarding the color conversion characteristics, the spectral reflection characteristics of the toner used as the color material are often selected to be close to that of the printing ink, so the color conversion characteristics of printing are generally used. It is being appreciated.

A procedure example of the first embodiment will be described with reference to the flowchart of FIG. First, in step 1, an automatic selection mode of image parameters is selected. The first original is placed on the original table (S2). The reading position (original color) of the first original described above is designated by the editor (S3). The scanner reads the RGB data at the designated position (S4). This is data 1.

Next, the second original is placed on the original table (S
5) The reading position (target color) of the second original is designated by the editor (S6). The scanner reads the RGB data at the designated position (S7). This is data 2.
The image processing parameter to be used is selected from the data 1 and the data 2 so that the target color can be obtained from the original color (S).
8). Details of step S8 will be described later.

The selected image processing parameter is set (S9). The user is asked whether to register the selected result (S10). Step S10 is not essential here and may be registered after the adjustment is completed.
When registering, it is stored in the nonvolatile ROM (S11).
A method of selecting RGBγ in step S8 of FIG. 9 will be described.

[0053]

(Equation 3)

When the reading signal of the scanner when reading the original is the above expression (3), the RGBγ conversion table is obtained as follows. As an example,
For the red γ table array red [i] (i = 0, 1, ..., 255), a conversion table that passes the following three points is selected.

[0055]

(Equation 4)

When selecting the RGBγ conversion table,
As an example, several kinds of tables are calculated in advance using the following formula, and the table that passes the above points or is the closest table is selected:

[0057]

(Equation 5)

Here, n _in is an input signal and n _out output signal, and the reflectances of the white part and the black part of the document are r _w and r, respectively.
_k was used (this value uses the reflectance of plain paper). The parameter γ can take an arbitrary real number, and the curve degree of the table can be changed by changing this value (FIG. 10). Here, γ =
3-4 were used.

The correction of the color conversion coefficient is performed as follows.
From the equation (1), the following equation holds for a known original document (target color) such as printing, toner, and photographic paper original document for a certain color X.

[0060]

(Equation 6)

Here, (b, g, r) is the reading value of the scanner, (y, m, c) is the output of each YMC of the printer (this corresponds to the image density), the matrix coefficient a _ij (i, j = 1,2,3) is predetermined for each document type such as printing, toner, and printing paper. On the other hand, even for an original color (original color) having an unknown spectral reflection characteristic,
The same equation holds and the following equation (7) is obtained.

[0062]

(Equation 7)

However, here, the reading values of the unknown original are set to (b ′, g ′, r ′), and the unknown matrix coefficient c _ij (i, j =
By using 1,2,3), the same copy density (y, m, c) as when copying an original having known spectral reflection characteristics such as printing, toner and printing paper can be obtained (this is the purpose).
And Similarly, assuming that similar equations hold for Black and White, the following equations hold for known originals such as print, toner, and photographic paper originals.

[0064]

(Equation 8)

[0065]

(Equation 9)

Similarly, for unknown documents, the following equations (10) and (11) hold.

[0067]

(Equation 10)

[0068]

[Equation 11]

From the above equations (6) to (11), the equation (1
2) holds.

[0070]

(Equation 12)

By multiplying both sides of expression (12) by the inverse matrix of the matrix on the right side of the left side of expression (12), the required color conversion coefficient c _ij (i, j = 1,2,3) is calculated as follows. It is calculated by the formula.

[0072]

(Equation 13)

Here, [] ⁻¹ represents an inverse matrix. Further, (b, g, r) and (b ', g', r ') use the values after RGBγ conversion. In formula (13)

(B _w , g _w , r _w ) = (b ′ _w , g ′ _w , r ′ _w ), (14) (b _k , g _k , r _k ) = (b ′ _k , g ′ _k , r ′ _k ) (15), and by doing so, the color conversion coefficient to be obtained can be obtained by designating one of the original color and the target color.

The physical meaning assumed in this way is that equation (14) assumes that the reflectance of the background of paper is almost the same. This means that the color difference is small when the original types (paper types such as plain paper and photographic paper) are the same. This is effective when the printing paper mode, the printing mode, and the like are provided and each mode is selected according to the document type. Further, in a normal case (when the image is not a reverse image), the toner image is not placed on the background portion, so that the assumption of the color reproduction of the background portion has little influence.

The assumption of the equation (15) is valid because black has a low reflectance and therefore when a density near 0% is used, the difference between the originals is small. If the above assumptions are not satisfied due to different document types, sufficient color reproducibility may not be obtained, and therefore, the assumptions of equations (14) and (15) are not made, and each color ( It is also necessary to specify (White, Black). However, in this case, for the colors of achromatic colors such as White and Black, the correction / formula (3) is performed by the RGBγ table, and for the chromatic color, the formula (1
4), correction of the equation (13) assuming (15) is performed, 2
It is effective to make a step correction.

The above processing will be described with reference to the flowchart of FIG. Here, the target color and the document color have already been specified, and their RGB signals have already been read.

In step S21, if the target color and the document type of the original color (original type) are the same, the process proceeds to step S22. If the document types are different, the process proceeds to step S25. here,
The case of the same type of original means that it is for plain paper, photographic printing paper for silver halide photography, etc. which are already in the mode, and that other thermal transfer papers are different. If it is a photographic paper original in step S22, in step S23, if the maker of the photographic paper is the same, and if it is not a photographic paper original in step S22, the color conversion coefficient is calculated in the above-described method in step S24.

If it is determined in step S23 that the maker of the printing paper is different, and if the paper type of the original is different in step S21, the process proceeds to step S25. In step S25, when the target color is an achromatic color, the RGBγ conversion table is calculated by the method of Expression (3). When it is achromatic,
Simply, when the difference between the RGB signals is smaller than a certain value δ, that is,

The case may be such that | r-g | <δ and | g-b | <δ and | b-r | <δ. Here, | x | represents the absolute value of x.

If the target color is a chromatic color in step S25, the flow advances to step S26 to select whether to calculate a color conversion coefficient (S27) or an RGBγ conversion table (S28). can do. The above method can be similarly applied to a method of dividing a hue and using different color conversion coefficients. In this case, more detailed settings can be made by making the above settings for each of the divided areas, which is more effective in color reproduction.

The second embodiment will be described with reference to the flowchart of FIG. When a plurality of sets of original colors and target colors are designated as in the present embodiment, in order to simplify the operation, the originals for designating the original colors and the target colors are set on the original plate of the copying machine. It is good to put it on top at the same time. A3 size (420mm
X297 mm) or larger, the size of the first and second originals may be, for example, A4 (210 mm × 297 mm).
By specifying up to, the above procedure can be simplified and the operability is improved. This point is not limited to this embodiment, and may be applied to embodiments corresponding to other claims.

An automatic selection mode of image parameters is selected (S31). The first original and the second original are placed on the original table (S32). The reading position (original color) of the first original is designated by the editor (S33). RGB at the specified position
The scanner reads the data (S34). This is data 1.

Next, the reading position (target color) of the second original is designated by the editor (S35). R at the specified position
The scanner reads the GB data (S36). This is data 2. In step S37, step S33
The operations of to S36 are repeated as necessary. At this time, the original may be replaced if necessary.

From the data 1 and the data 2, the image processing parameter to be used is selected so that the target color can be obtained from the original color (S38). The selected image processing parameter is set (S39). The user is asked whether to register the selected result (S40). When registering, it is stored in the non-volatile ROM (S41).

The third embodiment will be described with reference to the flowchart of FIG. An automatic selection mode of image parameters is selected (S51). The first original and the second original are placed on the original table (S52). On the operation unit screen (FIG. 17), the second original is designated as a print original (S53). As a result, the image processing parameters for the print document (color conversion coefficient, spatial filter coefficient, gradation conversion table, gradation processing, etc.)
Is selected.

Reading position of the above-mentioned first original (original color)
Is designated by the display editor 503 (FIG. 4) (S54). The scanner reads the RGB data at the designated position (S55). This is data 1. Next, the second original is placed on the original table (S56), and the reading position (target color) of the second original is set to the display editor 5.
It is designated by 03 (S57). The scanner reads the RGB data at the designated position (S58). This is data 2.

From the data 1 and the data 2, the image processing parameter to be used is selected so that the target color can be obtained from the original color (S59). The selected image processing parameter is set (S60). The user is asked whether to register the selected result (S61). When registering, it is stored in the non-volatile ROM (S62).

In the first modification of the third embodiment, as shown in FIG.
In step S53 of 3, the printing paper original may be selected instead of the printing original. As a result, the image processing parameters for the photographic paper document are selected. This is effective in the following cases. The spectral reflectance of photographic paper differs depending on the maker of the photographic paper. Therefore, re
Due to the difference in reflectance on the d side (wavelength: λ = 600 to 700 [nm]),
Although there are photographic papers made by manufacturers that reproduce the copied material in almost the same color as the original, due to the balance with the spectral transmittance of the RGB filter used for the CCD of the scanner,
It may be reddish or the complementary tint of cyan may be strong. This is the blue side (wavelength: λ = 400 to 50
Due to the difference in reflectance at 0 [nm], the blue component becomes stronger, and conversely, the complementary yellow component becomes stronger. In such a case, RGB γ is used by using the image processing parameters (color conversion coefficient, γ conversion table) for the photographic paper original.
Color reproduction is improved by changing the color balance by the conversion table.

In the second modification of the third embodiment, as shown in FIG.
In step S53 of 3, the toner original is selected when the print original is selected. As a result, the image processing parameter for the toner original is selected.

In the case of a toner original, it is possible to select the print original mode instead of providing the toner original mode because it has a spectral reflectance characteristic similar to that of the printing ink as compared with a printing paper original. However, in order to obtain good color reproducibility, the spectral sensitivity in the vicinity of RED light (600 to 700 [nm]) is different from that of the printing ink. Must be set. When selecting the toner original, not only the "toner original" but also the "generation" mode may be selected.

The fourth embodiment will be described with reference to the flowchart of FIG. An automatic selection mode of image processing parameters is selected (S71). It is designated that the second original, which is the target color, is a toner original (S72). It is determined whether the color patch is output (S73), and if it is determined that the color patch is output, the color patch is output on the transfer paper (S7).
4).

Next, the first original is placed on the original table (S
75), and specify the position of the color to be matched with the editor (S76). The RGB data at the designated position is read by the scanner (S77). This is data 1.

Place the output color patch on the document table (S
78). The reading position of the output color patch is designated by the editor (S79). The RGB data at the designated position is read by the scanner (S80). This is data 2.

An image processing parameter to be used is selected from data 1 and data 2 (S81). The selected image processing parameter is set (S82). The user is asked whether or not to register the selected result (S83). When registering, it is stored in the non-volatile ROM (S84).

The fifth embodiment will be described with reference to the flowchart of FIG. An automatic selection mode of image processing parameters is selected (S91). It is designated that the first and second originals are toner originals (S92). A copy is made (S94) according to the necessity of the document whose color is to be matched (S93).

The obtained copy is placed on the platen (S9
5) Specify the position of the color you want to match with the editor (S
96). The scanner reads the RGB data at the designated position (S97). This is data 1 (original color). If necessary (S98), the built-in color patch is output to the transfer paper (S99). The output color patch is placed on the document table (S100). The reading position of the output color patch is designated by the editor (S101).

The scanner reads the RGB data at the designated position (S102). This is data 2. An image processing parameter to be used is selected from data 1 and data 2 (S103). The selected image processing parameter is set (S104). The user is asked whether to register the selected result (S105). When registering, it is stored in the non-volatile ROM (S106).

A method of calculating the color conversion coefficient will be described. Equation (7)
Similarly, the following formula is established for the original color and the target color.

[0100]

[Equation 14]

[0101]

(Equation 15)

Here, (b ', g', r ') is the reading value of the document scanner, which is unknown in the above setting method. (y, m, c) is the target color of the YMC color patch of the printer, and (y ', m', c ') is the YMC output of the copy when the original is copied as it is. Is obtained from the read values of RGB designated as. The matrix coefficient a _ij (i, j = 1,2,3) is the color conversion coefficient for the toner original, and c _ij (i, j = 1,2,3) is the color conversion coefficient to be obtained.

Similar to the equations (9) and (10), Black and Whi
Since te can be expressed in the same manner as in equations (16) and (17),

[0104]

(Equation 16)

[0105]

[Equation 17]

From equations (18) and (19), c _ij (i = 1,2,3)
And ask

[0107]

(Equation 18)

Is obtained. Similar to the equations (14) and (15), (y _w , m _w , c _w ) = (y _w ', m _w ', c _w ') (21) (y _k , m _k , c _k ). = (y _k ', m _k ', c _k ') ... (22) By setting (y, m, c), (y', m ', c'), a new color conversion coefficient c _ij ( i = 1,2,3) can be obtained.

The above method can be similarly applied to a method of dividing a hue and using different color conversion coefficients. In this case, more detailed settings can be made by making the above settings for each of the divided areas, which is more effective in color reproduction.

The sixth embodiment will be described with reference to the flowchart of FIG. An automatic selection mode of image parameters is selected (S111). The type of the second original (printing, printing paper, toner, etc.) is specified on the operation unit screen (FIG. 17) (S112). If the second original is a toner original (S113), color patches are added as necessary (S11).
4) and output (S115).

The first original and the second original are placed on the original table (S116). The reading position (original color) of the first original is designated by the editor (S117). RG at the specified position
The scanner reads the B data (S118). This is data 1. Next, the reading position (target color) of the second original is designated by the editor (S119). The scanner reads the RGB data at the designated position (S12
0). This is data 2.

When the first original is not plain paper (S12
In 1), the RGBγ conversion table is calculated from the data 1 and the data 2 so that the target color can be obtained from the document color (S
122), and then the color conversion coefficient is calculated (S12).
3). Set the selected image processing parameters (S1
24). The user is asked whether to register the selected result (S125). When registering, it is stored in the non-volatile ROM (S126).

A first modification of the sixth embodiment will be described. The above method can be similarly applied to a method of dividing a hue and using different color conversion coefficients. In this case,
By performing the above setting for each divided area, more detailed setting can be performed, which is more effective in color reproduction. From equations (1) and (2), Black can be added to give the following expression:

[0114]

[Equation 19]

Expression (23) is a generalized expression from Expression (1). (Y, m, c, k) is the output of YMCK four colors on the printer side, and (b, g, r, l) (( b, g, r) is an input (after RGBγ conversion) of the scanner, and a _i4 (i = 1 to 4) represents a constant term (which is not 0 when the background is colored).
When the target color (r, g, b) and the document color (r ', g', b ') are set for a certain color X described above, the color is divided into six hues of RGBYMC (an example is shown. ), When the read image signal (r, g, b) is classified into the hue of R (red), in the hue RY,

[0116]

(Equation 20)

[0117]

(Equation 21)

And are satisfied. Where (y _y , m _y , _cy ,
k _y) is a typical yellow color region, as far as not specified otherwise, the formula (24), using a common value in (25). For (y _w , m _w , c _w , k _w ) and (y _k , m _k , c _k , k _k ), the expression (2
4) and (25) have the same value. Similarly to Expression (13), from Expressions (24) and (25),

[0119]

(Equation 22)

Therefore, the matrix coefficient c required while maintaining continuity at the boundary between the hues of red and yellow
_ij (i, j = 1,2,3,4) can be calculated.

The boundary area with the hue RM is similarly obtained. The same applies when colors of other hues are designated as the document color and the target color.

At the time of registration, a registration name can be set in the image parameter to be registered by the operation unit shown in FIG. The registered name can be displayed as shown in FIG. 19 or FIG. 20, and the registered contents can be registered and called. The registered content is registered in the nonvolatile RAM 132 of FIG.

The above embodiment is one example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.

[0124]

As is apparent from the above description, the image forming apparatus of the present invention reads an image of a document as an image signal of a plurality of colors, performs gradation conversion on the read image signals, and applies a color material of a plurality of colors. To form a color image. In acquiring this image signal, the reading position of the document is designated. A read signal obtained by reading a specified position of the first original,
From the read signal obtained by reading the specified position of the second original, the gradation conversion characteristic of the read signal, or the conversion characteristic of converting the gradation-converted read signal into an image signal for forming a color image , At least one of the characteristics is changed. Therefore, by changing this characteristic,
The color tone of the read image signal can be adjusted for each designated position.

Therefore, according to the first to sixth aspects, it is possible to set the image processing parameters according to the document type by a simple operation.

According to claim 2, chromatic color, achromatic color,
The accuracy of color reproducibility is improved by setting a plurality of colors having different hues.

According to the third aspect, the difference in the color reproducibility of the ink depending on the manufacturer of the print original is corrected with higher accuracy, and the color reproducibility is improved.

According to the fourth aspect, it is possible to obtain the color reproducibility matched with the printing paper formed by the silver salt photographic method. As a result, the difference in color reproducibility due to the difference in spectral reflection characteristics between photographic paper manufacturers can be corrected with higher accuracy,
Color reproducibility is improved.

According to the fifth to seventh aspects, it is possible to obtain an image that matches the color reproducibility of the toner.

According to the fifth to sixth aspects, by using the color patch built in the image forming apparatus,
It is possible to specify from among the colors that can be expressed by the image forming apparatus to be used, and by outputting various colors with color patches, it is possible to quickly set the target color.

According to the eighth aspect, in the case of thermal transfer paper other than plain paper and photographic paper, the white (achromatic) color of the paper is obtained by changing the color balance by the RGBγ conversion table.
Reproducibility is improved, while in the case of plain paper, RGBγ
By not changing the color balance of the conversion table, it is possible to prevent coloring of white (background).

According to the ninth aspect, more detailed setting can be made by setting the color conversion coefficients of a plurality of hues.

According to the tenth aspect, by setting a name in the image parameter to be registered and displaying the registered name when calling the registered content, the registered content can be easily associated even if the registered content is forgotten. You will be able to.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view showing a mechanism of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a block diagram showing the control system of FIG.

FIG. 3 is a block diagram of a circuit configuration of FIG.

FIG. 4 is an overhead view of an operation unit.

FIG. 5 is a color patch diagram.

FIG. 6 is a block diagram of a laser modulation circuit.

FIG. 7 is a timing chart of light emission of laser light.

FIG. 8 is a characteristic diagram showing a detection output of the optical sensor.

FIG. 9 is a flowchart for explaining the first embodiment.

FIG. 10 is a diagram showing input / output characteristics of an RBGγ conversion table.

FIG. 11 is a flowchart illustrating an example of an image parameter calculation procedure.

FIG. 12 is a flowchart for explaining a second embodiment.

FIG. 13 is a flowchart for explaining a third embodiment.

FIG. 14 is a flowchart for explaining a fourth embodiment.

FIG. 15 is a flow chart for explaining a fifth embodiment.

FIG. 16 is a flowchart illustrating a sixth embodiment.

FIG. 17 is a diagram showing an example of an operation unit screen in a selection mode.

FIG. 18 is a plan view showing an example of key arrangement of an operation unit.

19 is a diagram showing a registration content example 1 in FIG.

20 is a diagram showing a second registered content example in FIG.

FIG. 21 is a spectral sensitivity characteristic diagram 1 of a conventional CCD.

FIG. 22 is a spectral sensitivity characteristic diagram 2 of a conventional CCD.

[Explanation of symbols]

 101 Copier Main Body 102 Organic Photoreceptor (OPC) Drum 103 Charging Charger 104 Laser Optical System 105 Black Developing Device 106, 107, 108 Color Developing Device 109 Intermediate Transfer Belt 110 Bias Roller 111 Cleaning Device 112 Electrification Unit 113 Transfer Bias Roller 114 Belt Cleaning device 115 Conveyor belt 116 Fixing device 117 Paper ejection tray 118 Contact glass 119 Exposure lamp 121 Reflecting mirror 122 Imaging lens 123 Image sensor array 130 CPU 131 ROM 132 RAM 133 I / O 134 Laser optical system controller 135 Power supply circuit 136 Optical Sensor 137 Toner concentration sensor 138 Environment sensor 139 Photoconductor surface potential sensor 140 Toner supply circuit 141 Intermediate transfer belt drive Part 201 developing sleeve 202 developer regulating member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 1/46 H04N 1/46 Z

Claims (10)

[Claims] 1. An image reading unit that reads an image of a document as an image signal of a plurality of colors, a unit that performs gradation conversion of the read image signal, and a unit that forms a color image using a plurality of color materials. And a means for converting the gradation-converted image signal into an image signal for forming a color image, and a means for designating a reading position of the original, which is obtained by reading the designated position of the first original. For forming the color image from the gradation conversion characteristics of the read signal or the gradation-converted read signal from the read signal obtained by reading the designated position of the second document. An image forming apparatus, characterized in that at least one of the conversion characteristics of means for converting into an image signal is changed. 2. A designated position of the first original and a second position of the first original.
2. The image forming apparatus according to claim 1, wherein the designated position of the document is plural. 3. An image of at least one of the first original and the second original is formed by printing ink, and the image forming apparatus further has means for specifying the original formed by the printing ink. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. 4. An image of at least one of the first original and the second original is formed by a silver salt photographic method, and the image forming apparatus further specifies a printing paper used in the silver salt photographic method. The image forming apparatus according to claim 1 or 2, further comprising: 5. The image forming apparatus further includes a color patch generation unit and a unit that outputs the color patch generated by the color patch generation unit to a transfer material, and the first original document and the second original document. One of the above is used as an output image of the color patch.
The image forming apparatus as described in the above. 6. The image forming apparatus further includes a color patch generation unit and a unit for outputting the color patch generated by the color patch generation unit to a transfer material, and the first original document and the second original document. 3. The image forming apparatus according to claim 1, wherein one of the two is used as an output image of the color patch, and the other is used as a copied image with toner. 7. An image of at least one of the first original and the second original is formed by toner, and the image forming apparatus further has means for specifying that the original is a toner original. Claim 1 characterized in that
The image forming apparatus according to any one of 2, 5, and 6. 8. The image forming apparatus further comprises a selection unit for selecting whether or not the first original and the second original are plain papers. The image forming apparatus according to item 1. 9. The image forming apparatus further switches a classification unit that classifies the color of the image signal into one of a plurality of predetermined hues, and a correction coefficient used in a predetermined calculation according to the classification performed by the classification unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. 10. The image forming apparatus further comprises registration means for registering image parameters, registration name setting means for setting a registration name by the registration means, display means for displaying the set name, and the displayed name. The image forming apparatus according to any one of claims 1 to 9, further comprising: a registration selecting unit that selects registration contents based on the.