JPH01166671A - Color picture reader - Google Patents

Abstract

PURPOSE:To copy an original characteristic in its hue into a natural state by revising a data with respect to the quantity of ink in response to a human sense to a color. CONSTITUTION:An analog color signal given from an image sensor 28 is inputted to a color masking circuit 39 via A/D converters 33-35 and shading circuits 36-38. A CPU 30 obtains a data with respect to the quantity of ink in response to the human sense to a color based on a digital color signal given from line RAMS 52-54 to set the conversion table of the masking circuit 39. The digital color signal converted by the masking circuit 39 is outputted via a binary/ intermediate tone processing circuit 51.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a color image reading device, and more specifically, it is included in a digital color copying machine, etc., and is used to detect color density that represents the intensity of red light, green light, and blue light, respectively. The present invention relates to a color image reading device that forms signals and generates signals representing ink amounts of cyan, magenta, and yellow colors based on these color signals.

[Prior Art] As a conventional color image reading device of this type, one shown in FIG. 2, for example, is known. Second
In the figure, 1 is a document on which a color image is drawn, and this document 1 is irradiated with white light of light R4 that receives driving force from a motor 2 and moves in the direction of arrow 3, and the reflected light is reflected in the direction of arrow 3. An image sensor 5 composed of a plurality of CCD elements arranged substantially at right angles to the color signal R9G represents the intensity of each red, green, and blue color of reflected light as a voltage value, respectively.
Converted to H. These color signals R, G, and B are converted from the reflection intensity of each color to a density value of each color in a logarithmic conversion circuit 6 and output as a color density signal (reflectance value is Rf, color density signal value is D, the logarithmic conversion circuit calculates D=-1ogRf).

These color density signals are converted from analog values to digital values by the A/D converter 7, and are converted into digital color density signals DR'.
, DG', DB' to the shading circuit 8. The shading circuit 8 corrects errors caused by uneven light emission of the light source 4 and variations in characteristics of the CCD elements constituting the image sensor 5, and then performs masking processing on the corrected digital color density signals DR", DG", and DB". Circuit 93. Engraving of specification (no change in content) The masking processing circuit 9 outputs the amount of ink for each color of cyan, magenta, and yellow based on the digital color density signals DR", DG", and DB". Signals C, M,
Y is formed and these output signals C,M.

Y is supplied to a printing device (not shown) via a halftone processing circuit 10 that performs dither processing and the like. 11 is each of the above circuits 7-
A central processing unit arithmetic unit (M
PU).

As a specific example of the masking processing circuit 9, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-216870, coefficients a00 to a22 representing the characteristics of printing ink and digital color density signals DR", DG79, D B
It is composed of a plurality of read-only memories that fixedly store the multiplication results by 7% for each color, and an adder circuit that adds the outputs of these read-only memories.

In general, the coefficients aOO to a22 are set so that the hues of pixels printed for various color samples are close to each other. Specifically, the coefficients aOO to a22 are set so that the hues of printed pixels are similar to each other for various color samples. , a large number of color samples each represented by (Lne, at, bne) values and (!j', h*' of printing color).

Squared error ΔE2 ΔE 2 = Σ ((LneLne') 2+
(al-a*') 2+(b-ho 5')2)
・ ・ ・ It is set so that (Formula 1) is minimized.

[Problems to be Solved by the Invention] However, the conventional masking processing circuit 9 described above has the following problems:
Since the values of coefficients a00 to a22 were set to minimize the squared error ΔE2 calculated by (Equation 1), good results were obtained for originals containing various hues on average. However, there is a problem in that it is not necessarily possible to obtain a natural color tone to the human senses. In other words, for example, when reproducing a document with a person's face on a green background, it is recommended to minimize the color shift of the person's face even if the area of the background in the document is larger than the area of the person's face. is preferable to human senses, but masking processing based on the average hue as described above does not necessarily provide a natural feeling.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a color image reading device that can obtain natural-looking copied images even from originals with uneven hue.

[Means for Solving the Problems] The present invention makes it possible to obtain images that are natural to human senses by selectively using coefficients that improve the reproducibility of hues in documents that particularly attract human attention. The gist of this method is to include a color signal forming section that outputs a plurality of color signals each representing the intensity of light of a plurality of specific wavelengths, and a color signal forming section that outputs a plurality of color signals each representing the intensity of light of a plurality of specific wavelengths; A conversion table that holds data related to ink amount for each of a plurality of color inks and outputs a plurality of signals each representing data related to the ink amount corresponding to the color signal based on the plurality of color signals, and output from the conversion table. an adder that calculates the amount of ink for any of the above colors based on data regarding the amount of ink each represented by a plurality of signals; A specifying means for specifying an area, and a chromaticity difference between a color sample in a uniform color space and a color sample in a uniform color space for a hue belonging to the hue space area specified by the specifying means among the plurality of hues represented by the color signal in the hue space. The present invention is characterized by comprising coefficient setting means for causing the conversion table to hold data regarding an ink amount selected to be smaller than a chromaticity difference with a color outside the area.

[Operation of the Invention] In the color image reading device according to the above configuration, when calculating the amount of ink for an arbitrary color, multiple values regarding the amount of ink corresponding to the color signal are calculated based on a plurality of color signals supplied from the color signal forming section. Read the data from the conversion table. When the data regarding the amount of ink for the arbitrary color is read out from the conversion table in this way, the data regarding the amount of ink is sent to the adder, and the adder calculates the amount of ink for the arbitrary color.

The calculation of the amount of ink is performed for each of the plurality of colors, and printing is performed, for example, according to the amount of ink related to the plurality of colors. Here, the data regarding the amount of ink is based on a predetermined hue in the document as specified by the operator. Since the chromaticity difference can be selected to be smaller than the chromaticity difference, the printed image has a smaller color shift with respect to a predetermined hue designated based on the operator's sense.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 3 are diagrams showing a color image reading device according to an embodiment of the present invention.

In the figure, 21 is a document 22 on which a color image is drawn.
When copying an original 22, an exposure lamp 23, a first mirror 24, a second mirror 25, a third mirror 26, and a lens 2 are placed on the original glass stand 21.
7 and an image sensor 28 receives driving force from a motor 31 controlled by a central processing unit (CPU) 30 and repeatedly moves in the direction of an arrow 32. As the optical system 29 moves, the original 22 is irradiated with white light, and the reflected light is reflected from the first, second, and third mirrors 24 . 25°26
The light passes through the lens system 27 and is supplied to the image sensor 28. This image sensor 28 is composed of three rows of CCD elements each having a filter that selectively passes red light (R), green light (G), and blue light (B). outputs analog color signals R, G, and B that represent the intensities of the red, green, and blue components in the reflected light as voltage values, respectively. The document 22 is scanned three times per document, and the reason for performing three scans per document in this way is to print with cyan ink based on the first scan, and print with cyan ink on the basis of the second scan.
Print with magenta ink based on the second scan,
This is to perform printing using yellow ink based on the third scan.

Analog color signal R output from the image sensor 28,
G, B are A/D converters 33, 3 for each three scans.
4.35, the analog value is converted to an 8-bit digital value, and the digital color signal DR.

Shading circuit 36.37.38 as DG, DB
sent to. The shading circuits 36, 37, and 38 correct errors caused by uneven light emission of the exposure lamp 23 and variations in characteristics of the CCD elements constituting the image sensor 28, and then output corrected digital color signals DR, DG, and DB.
is supplied to the color masking circuit 39. The color masking circuit 39 is a random access memory (random access memory) having an 8-bit address terminal and an 8-bit data input terminal as shown in FIG.
Hereinafter, simply referred to as RAM)) are digital color signals DR, D.
It includes a configuration in which the output signals of the RAMs 40, 41, and 42 are prepared for each of G and DB and are supplied in parallel to the input terminal of the adder 43.

The color masking circuit 39 outputs the digital color signals DR, DG, and DB to each of the RAMs 40, 41, and 42, as will be described in detail later.
cyan ink, magenta ink, or magenta ink corresponding to the red component intensity, green component intensity, and blue component intensity of the reflected light represented by the digital color signals DR, DG, and DB. Output data OR, OG, and OB regarding each ink amount of yellow ink, and add these data regarding the ink amount of cyan ink, magenta ink, or yellow ink, respectively, to represent the ink amount of cyan ink, magenta ink, or yellow ink. Output signals C1, Ml, Yl are formed. As described above, in this embodiment, since only the amount of cyan ink, magenta ink, or yellow ink is calculated in one scan of the document 22, the ram 40.
41, 42 must be rewritten after each scan and before the start of the next scan, and for this purpose, the shading circuits 36, 37, .
Selectors 44, 4 between 38 and rams 40, 41, 42
5.46, selector 47 . 48 and 49, the central processing unit 3o executes a predetermined calculation based on the coefficients aoO to a22, which will be described in detail later, held in the central processing unit 30 (controlled by the central processing unit 30) 50 to obtain data regarding ink of different colors. is calculated and transferred to RAMs 40, 41, and 42. The output of the color masking circuit 39 is supplied to a printing device (not shown) through a binary/halftone processing circuit 51 that performs dither processing, etc.
After being subjected to predetermined processing, it is supplied to a printing device (not shown).

Therefore, in this embodiment, the optical system 29 and the A/D converter 33
, 34, and 35 constitute a color signal forming section as a whole, and rams 40, 41, and 42 constitute a conversion table.

Next, data regarding the amount of ink held in the rams 40, 41, and 42 will be explained.

The data regarding the ink amount is the logarithm value of the calculation result on the right side when the digital color signals DR, DG, and DB are changed using the determinant shown below. In addition, ao.

~a02 is a constant coefficient determined in advance based on the spectral reflection characteristics, printing characteristics, etc. of cyan ink used in a printing device (not shown), and alo~a12 are constant coefficients determined in advance based on the spectral reflection characteristics, printing characteristics, etc. of magenta ink. It is a fixed constant coefficient. In addition, a20 to a22 are the spectral reflection characteristics of yellow ink,
This is a constant coefficient determined by printing characteristics, etc. These coefficients ao
O to a22 are stored in the read-only memory 5o for a plurality of sets, each corresponding to a plurality of hues for which reproducibility is important, as will be described in detail later. Furthermore, C, M, and Y indicate the amounts of cyan ink, magenta ink, and yellow ink, respectively.

Continuing with the explanation regarding the data regarding the ink amount, when printing with cyan ink, the logarithm value of the calculation result of aooXDR when changing the value of the digital color signal DR is stored in ram 4o and ram 41. stores the logarithmic value of the aol
The logarithm value of the calculation result of B is stored.

On the other hand, when printing with magenta ink, when the values of the digital color signals DR, DG, and DB are changed, a
The logarithmic values of the calculation results of lOXDR, allXDG, and a12XDB are each held in the RAM 40°41.42, and similarly, when printing with yellow ink, the values of the digital color signals DR, DG, and DB are stored, respectively. a20XDR, a21XDG, a22 when changed
The logarithm value of each calculation result of XDB is Ram 40. 4
1. 42, respectively.

When reading data regarding the amount of ink from these rams 40, 41, 42, the rams 40, 41, 42 are switched to read mode in response to a write/read control signal W/H supplied from the central processing unit 30. The selectors 44 to 49 control the shading circuit 3 by bus control signals supplied from the central processing unit 30.
Since the signals supplied from rams 6 to 38 are switched to the address terminals of rams 40, 41, and 42, and the output signals of rams 40, 41, and 42 are supplied to the adder 43, the rams 40, 41 From .42 onwards, the data regarding the ink amount stored in the addresses indicated by the values of the digital color signals DR, DG, and DB is outputted from the data input/output terminal to the adder 43. On the other hand, when the address signal is supplied from the central processing unit 30, the ram 40
．． 41 and 42 enter the write mode, and the central processing unit 30 transfers data regarding the new amount of ink supplied to the data input/output terminal via the data bus DB to the address bus A.
They are sequentially written to the addresses appearing in B.

An example of data regarding the amount of ink held in the rams 40, 41, 42 in this manner is shown in the table below.

The table below shows data regarding the amount of ink when a00=10110010 and the value of the digital color signal is changed from oooooooo to 11111111.

(Hereinafter, blank space) The data regarding the amount of ink read out from each of the rams 40, 41, and 42 in this manner is supplied to the adder 43, and added by the adder 43. Therefore, the output signal output from the adder 43 for each document scan represents the amount of cyan ink, magenta ink, or yellow ink.
There is no change in the translated content of the adder specification) ('7-1
Based on the output signal from the 0 East 243, a printing device (not shown) draws partial images of cyan, magenta, and yellow, and when these partial images of each color are combined, the image drawn on the original 22 is It will be copied.

Next, a coefficient a for calculating data regarding the amount of ink
00 to a22 will be explained. Coefficient aOO of this example
~a22, as mentioned above, has higher reproducibility of a specific hue than that of other hues, and specifically, the (L, a, b) values of color samples in a uniform color space and the print color. comb *'; aoo that minimizes the squared error ΔE2 (see formula 2), which is weighted by color k between ane', b*'> value
~a22 (hereinafter referred to as (aij)k) is selected.

△E2=ΣWk((LkNeLk*')2+(ak
2+ (bk ne bk ne') 2+ (bk ne bk ne'
) 2) (Formula 2) The coefficients a00 to a22 above are for a specific color (for example, blue), and the coefficients are set so that the chromaticity shift of the specific hue is smaller than the chromaticity shift of other hues. be done. Therefore, a plurality of such coefficient sets (aij) k are prepared for each different hue, and are stored in the read-only memory 50.

At the time of printing, a specific set is selected from a plurality of sets as will be described in detail later, and the central processing unit 30 selects the coefficient aoO constituting the knee set.
- a22 are sequentially read out to calculate data regarding the ink amount.

In this embodiment, the read-only memory 50 stores the coefficients aOO to a22 of each set, so the storage capacity of the read-only memory 50 may be relatively small, about 6 bytes. When data related to quantity is stored directly, each data is 8 bits, and 28 x 6 = 1. 5 (kilobytes) of storage capacity is required for each set (aij)k, leading to an increase in the storage capacity of the read-only memory 50.

The color image reading device according to this embodiment further includes line rams 52, 53, and 54 connected in parallel to the shading circuits 36, 37, and 38.
The outputs of 3 and 54 are supplied to data input/output terminals of the central processing unit 30. These line rams 52, 53. 54
temporarily stores the digital color signals DR, DG, DB output from the shading circuits 36, 37, 38 when selecting a predetermined coefficient set (aij) k from a plurality of sets, and then outputs the digital color signals DR, DG, DB from the central processing unit 30. provides data for determining the dominant hue of document 22. That is, when the user of the color image reading device according to the present embodiment specifies the Briscan mode using a mode designation switch (not shown) before copying the original 22, the central processing unit 30 communicates with the user via the communication system 55. Deactivating a printing device (not shown) in response to the transmitted Briscan mode signal, and
An operation command is given to the optical system 29 to start scanning the original 22. As the original 22 is scanned, the A/D conversion circuit 33.
34.35 and the shading circuits 36, 37.38. 53. 54 are supplied with digital color signals DR, DG, and DB, the central processing unit 30 forms a histogram of the hues of the original 220, and
After determining the dominant hue of 2, the set of coefficients (aij)
Determine k. Note that when starting copying without specifying the Briscan mode, the operator can directly specify a set of hue coefficients. That is, six switches 61 to 66 as shown in FIG. 7 are provided on the operation panel (not shown), and these switches 61 to 66 are as shown in FIG. It is possible to specify the hue space regions of red (R), yellow (Y), green (G), cyan (C), blue (B), and magenta (M). Therefore, these switches 61 to 66 constitute a specifying means.

When any of these switches 61 to 66 is operated, the hue space corresponding to the operated switch 61 to 66 is specified, and a set of coefficients (
aij)k is selected. On the other hand, the switches 61 to 6
If none of 6 is operated, a set of average hue coefficients expressed by (Equation 1) is specified.

Next, the operation of this embodiment will be sequentially explained with reference to the flowcharts shown in FIGS. 9 and 10.

When the operator desires to make a color copy of the original 22, places the original 22 at a predetermined position on the original glass table 21, and selects the Briscan mode, the central processing unit 30 performs step Sl.
When the selection of the Briscan mode is detected (Y), the Briscan subroutine SRI, which will be described in detail later, is executed, but if the judgment result in step S1 is No (N), coefficient data for a specific hue is specified. In step S2), if the hue space designation switches 61 to 66 are operated to read the hue designated by the operator and the determination result in step S2 is yes (Y), the switch 61 is Based on the operations in steps 66 to 66, a set of coefficients corresponding to the operated switch is selected from a plurality of sets of coefficients (step S3). - On the other hand, when the switch for hue specification is not operated, a set of averagely optimized coefficients determined according to (Equation 1) is selected (step S
4).

When the above-mentioned Briscan mode SRI starts, as shown in FIG. (Step S6). The motor 31 starts normal rotation in response to an instruction from the central processing unit 30, and starts blisscanning of the original 22 (step S7). With the start of this Briscan, digital color signals DR, DG are output from each shading circuit 36, 37, 38 as appropriate.

DB is output. Therefore, the central processing unit 30 reads the hue of each pixel from the line RAMs 52, 53, and 64 (step S8), and determines to which of the spaces Ri that the uniform color space is divided into a predetermined number the hue of the read pixel belongs. step S9), and is added to the histogram (step 510). In this way, while creating a histogram and executing bliscan for the entire range of the original document 22 (steps 38 to 510), it waits for the determination result in step s11 to be YES. Eventually, when the entire range of the original document 22 has been scanned, the judgment result of the Stub Sll becomes YES (Y), so the central processing unit 30 instructs the motor 31 to reverse the process. to return the optical system 29 to its initial position (step 512). Control then returns to the main routine shown in FIG.

When the histogram is thus completed, the central processing unit 30 determines the hue that appears most frequently based on the histogram, and determines a string of coefficients corresponding to the hue (step 513). In this way, Hara! When the set of coefficients for 22 dominant colors is determined, or the morning of the coefficient is determined by being specified by the operator or not being specified, the central processing 1Bit 30 calculates the coefficient (aij).
k is used to calculate data regarding the cyan ink and write these to the rams 40, 41, 42 (step 51).
4). Therefore, the central processing unit 3o and step S3.
S14 constitutes a coefficient setting means.

Eventually, when the switch to start copying is operated, the central processing unit 3o instructs the exposure lamp 23 to turn on, instructs the motor 31 to rotate forward, and performs the first scan. ) is started (step 515). When the first scan is completed in this manner, the central processing unit 30 repeats steps 514 to S15 to calculate data related to magenta ink, and performs the second scan. Similarly, when printing with magenta ink is completed, steps S14 to 515 are repeated again to perform printing with yellow ink.

Therefore, when the operator looks at the original 22 in step S3 and selects the color that attracts his attention, a color copy in a natural state that suits human senses can be obtained.

In the above embodiment, the data regarding the amount of ink held in the rams 40, 41, and 42 is rewritten each time the document is scanned, but the data regarding the amount of ink for three colors is stored in the large-capacity ram. You can stay there.

Further, in the above embodiment, explanation regarding the sign of aoo-a22 is omitted, but since some coefficients may be negative, it is preferable to use an adder 43 of a type capable of signed addition. . At this time,
As for the coefficient data to be written to the RAM, the most significant bit is the sign bit and the complement is written in advance, or since it is known in advance which data will be a negative number, the sign control circuit can be used as the RAM 40, 41, 42. It may be inserted between the adder 43 and the central processing unit 30 to control the sign control circuit to calculate a negative number for a negative coefficient.

[Effects of the Invention] As explained above, according to the present invention, it is possible to change the data regarding the amount of ink according to the human sense of color, so it is possible to copy originals with characteristic hues in a natural state. This effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the configuration of a color image reading device according to an embodiment of the present invention, FIG. 2 is a block circuit diagram showing the configuration of a conventional color image reading device, and FIG. 3 is an implementation example. FIG. 4 is a block diagram showing the detailed configuration of the optical system of the color image reading device according to the example, FIG. 4 is a plan view showing the arrangement of ram bins used in the masking processing circuit according to the example, and FIG. 5 is the example. 6 is a block circuit diagram showing the detailed configuration of the color masking circuit of one embodiment, FIG. 7 is a wiring diagram showing switch wiring, and FIG. 8 is a hue diagram. 9 is a flowchart showing the main routine of one embodiment; FIG. 10 is a flowchart showing the blisscan subroutine of one embodiment. 21... Original glass stand, 22... Original, 28... Image sensor, 29... Optical system, 30... Central processing unit, 33-36. ...A/D converter, 36-38...Φ...Shading circuit, 39...
...Color masking circuit, 40-42...Ram, (conversion table), 43...Adder, 50...Read-only memo 18 52-54...Line RAM, 61-66... switch. Patent applicant Minolta Camera Co., Ltd. Agent
Patent Attorney Kiyoshi Kuwai - (1 other person) Figure 2 Figure 4 Figure 5 Figure 8 Figure 7 Figure 9II! J Figure 10 Procedural Amendment (Method) 弗 April 5, 1986

Claims (1)

[Claims] (1) A color signal forming unit that outputs a plurality of color signals each representing the intensity of light of a plurality of specific wavelengths, and holds data regarding a plurality of ink amounts corresponding to the plurality of color signals for each of the plurality of colors of ink. and a conversion table that outputs a plurality of signals each representing data regarding the amount of ink corresponding to the color signal based on the plurality of color signals, and data regarding the amount of ink each represented by the plurality of signals output from the conversion table. In a color image reading device equipped with an adder that calculates the amount of ink for any of the above colors based on data, a designation that is operated by an operator to designate an arbitrary hue space region within a uniform color space. and a chromaticity difference between a color sample in a uniform color space and a color outside the hue space region for a hue belonging to the hue space region designated by the designation means among the plurality of hues represented by the color signal; 1. A color image reading device comprising: coefficient setting means for holding in the conversion table data regarding an ink amount selected to be smaller than a chromaticity difference.