JPS62283772A - Color picture copying device - Google Patents

Abstract

PURPOSE:To stably obtain reproducible signals R, G and B for the colors of an object by converting three-color separation signals by means of a data expansion constant and an off-set constant, and executing an copying operation. CONSTITUTION:Signals R, G and B obtained from a sensor 11 pass through an amplifier 12 and an A/D converter 13, digitalized, and added to a subtactor 14, where said signals are controlled by a CPU 20, and data from an orange base part RAM 21 subtracts the portion of an orange base. The signals are outputted from the subtractor 14 as data of the removed and pure signals R, G and B. Obtained data of signals R, G and B are inputted to a subtactor 15, where data are controlled by the CPU 20, and a histogram RAM 22 subtracts the off-set constants of respective chrominance signals from corresponding data of color signals. In a multiplier 16, the data expansion constant of respective chrominance signals are multiplied to data of corresponding chrominance signals. The outputs of the signals R, G and B from the multiplier 16 are converted to signals C, M and Y in a logarithm transforming circuit 17, corrected to signals C', M', and Y' in a masking circuit 18 and outputted to a copying device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color image copying device, and more particularly, to a color image copying device that digitally reads a color negative film and automatically transmits an image reading signal so as to reproduce the color of the subject when photographing the color negative film. This is a correction.

[Prior art] Color negative film is generally used to transfer an image of a subject formed on the film surface to a sensitive material that has spectral sensitivities in red, green, and blue, and develops colors in the complementary colors of cyan, magenta, and yellow. Record as an image.

Therefore, when reading a color negative film with a normal color copying device and copying it to reproduce the colors of the subject, the color negative film image is read with a red, green, and blue color separation sensor, and white and black are read. It is sufficient to invert the polarity to generate and output cyan, magenta, and yellow signals, which are the three primary colors of the image output device.

[Problem that the invention seeks to solve]

However, the relative and absolute values of each of the red (R), green (G), and blue ([1) color separation signals mentioned above vary greatly depending on the lighting conditions and exposure conditions when shooting color negative film, so they are not necessarily It does not necessarily reproduce the colors of the subject faithfully.

Figure 3 shows the image reading section (
2 is a block diagram showing a configuration for reading a negative image using a reader (hereinafter referred to as a reader). FIG. In the figure, a negative film 102 is illuminated by a halogen lamp 100 and a condenser lens 101, and a negative image is formed on the upper surface of an original platen glass 106 by a lens 103, a mirror 104 for bending the optical path, and a Fresnel lens +05 for correcting the divergence of the imaging light. is imaged. These include an infrared cut filter 107, an imaging lens 108, an R, G, and B color separation sensor 109.
The image reading unit 110 scans in the direction of the arrow and reads the image.

FIG. 4 is a block diagram showing the configuration of conventional signal processing when reading and copying a color original.

The color separation signal read by the RGB sensor 201 is A/
The signal is D-converted and input to the offset circuit 202. The offset circuit 202 uses the black (density 15) of a general reflective original.
The offset constant is subtracted so that the output becomes 0 when the value (approximately 2.0) is read. This constant can be set in advance.

Next, in the data decompression circuit 203, the white (f) of a general reflective original is
The data is expanded by multiplication by a constant so that when the A degree (005 to 0.08) is read, the output becomes the highest level (255 in the case of 8-bit data).

At this time, the degree of expansion is determined in advance by referring to the white data 204 obtained when a white original is read.

Next, the logarithmic conversion circuit 205 converts the R, G, and B data sent from the data expansion circuit 203 into density data C, M, and Y.
A color correction process generally called masking is applied to the density data generated by hN to obtain C'', M', and Y'.

These C'', M'', and Y' are sent to a color image output device (hereinafter referred to as a printer), and a copy image of the original image is output.

FIG. 5 is a characteristic diagram showing a conventional relationship between signal values and reflectances of originals and copied images in a four-quadrant graph.

As shown in Figure 2, a straight line 301 is the sensor output for the reflectance of the original, and as mentioned above, the reading output data of the reflective original is offset and expanded, so it is 0 for a black original and 0 for a white original. Maximum level output can be obtained.

A characteristic curve 302 shows the output (ie, density value) after logarithmic conversion of the sensor output, and a characteristic curve 303 shows the density gradation output characteristics of the printer. A straight line 304 indicates the reflectance of the copied image, and represents that the characteristic curves 302 and 303 cancel each other out, ultimately resulting in a linear characteristic.

Next, the case where a color negative film is read by the conventional color original copying apparatus shown in FIG. 4 will be explained.

FIG. 6 is a characteristic diagram of a four-quadrant graph showing the relationship of signal values when reading a color negative film corresponding to FIG.

Characteristic curves 401 and 402 are negative film transmittance versus subject reflectance, and characteristic curve 403 is a conversion curve of sensor output to density value. The characteristics that differ from the characteristics shown in FIG.
1 and 403, the black and white magnitude relationship is reversed.

By the way, the characteristic curve 401 is for color negative film,
It is not constant and varies greatly depending on the conditions at the time of shooting.

That is, if the exposure value at the time of shooting differs, the characteristic curve 401 may move in parallel up or down as shown by the dotted line in the characteristic curve 402, or
In some cases, the shape of the curve may change due to the illumination light source during photography, the gamma characteristics of the negative film, etc.

Furthermore, the fluctuations of the characteristic curves 401 corresponding to R, G, and B are different from each other. Therefore, unlike the color original reading signal processing configuration shown in FIG. 4 when copying a reflective original, the offset constant and data expansion coefficient in the offset circuit and data expansion circuit are different for each film, R, G, []
Everything has to be changed to suit each case.

Therefore, the purpose of the present invention is to provide a R
, G, and B signals.

(Means for Solving the Problems) In order to achieve such an object, the present invention provides a color image copying apparatus that images a color original on a three-color separation sensor, reads the image, and copies the image. Frequency distribution creation means for reading part or all of the image and creating a frequency distribution of the amplitude value versus frequency of occurrence of each of the three color separation signals; and obtaining upper and lower limits of the image signal amplitude value from the frequency distribution creation means. A means for determining the signal amplitude value to be expressed, and a constant calculated from the upper limit signal amplitude value and lower limit signal imaging width value.
It is characterized by comprising arithmetic means for respectively setting a data expansion constant and an offset constant for each of the three color separation signals, and converting the three color separation signals using the data expansion constant and the offset constant to perform a copying operation. do.

[Function] According to the present invention, a subtraction constant for offset and a multiplication constant for data expansion are determined independently for each color signal of R, G, and B for each target color and negative film. It is possible to obtain R, G, and B signals such that the characteristic curve of the negative film transmittance substantially always takes the same shape.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1A is a block diagram showing the configuration of an embodiment of a color image copying apparatus according to the present invention.

In the figure, 11 is a sensor that obtains R, G, and B signals, 12 is an amplifier, 13 is an A/D converter that converts the analog R, G, and B signals into digital values, and 14 is the data for the orange base part of the color negative film. 15 is a subtracter that subtracts the offset value. 16 is a multiplier that multiplies for data expansion. 17 is converting R, G, and B data into density data C, M, and Y. A logarithmic conversion circuit 18 is a masking circuit that performs color correction to remove asymmetric color components of the viewing color material.

20 is a CPU for performing the processing shown in Fig. 1, which will be described later.
, 21 is the RA that holds the data of the orange base part.
M, 22 is a histogram IIAM for storing the frequency of occurrence of each value of It, G, and B, and 23 is the first
This is a ROM that stores the control flowchart shown in FIG.

FIG. 1B is a flowchart showing a procedure for processing a color negative film image signal according to an embodiment of the present invention.

In this embodiment, a subtraction constant for offset and a multiplication constant for data expansion are determined independently for R, G, and B for each film of the target original image.

The process will be explained step by step according to the flowchart shown in FIG. 1B.

l) First, in step S1, a multiplication constant for data expansion is reset to 1, and in step S2, a subtraction constant for offset is reset to 0.

Next, the process proceeds to step S21, in which the orange base portion at the end of the color negative film is scanned. Then, in step S22, the R, G, and B data of the orange base part are roughly RA
Store in M21. The data of the orange base part is output to the subtracter 14, and only the pure color component, which is obtained by subtracting the data of the orange base part from the R, G, and B data, is sent to the subtracter 1.
Obtained in 4.

2) Next, in step S3, a part or all of the area where the negative image is formed is scanned by the R, G, B sensor and read, and in step S4, the three primary color signals R, G, output from the subtractor 14, For each of B, a histogram is created based on the frequency of occurrence of signal values.

' FIG. 2 is a histogram of each of R, G, and B of an embodiment according to the present invention.

3) Step S5 Find the minimum value <m1n) and maximum value (max) of the signal values of the R, G, and B histograms.

min and max are the minimum and maximum signal values that do not have a cumulative frequency of O.

The values of min and max are determined here by the following procedure.

(1) Let f (N) be the cumulative frequency at a certain signal value N.

(2) Let the minimum and maximum values of N such that f (N)≠O be N min *Nmax, respectively.

(3) f (N
) = Q, and set it as No.

(4) If No does not exist, min = Nm1n,
Determine max = Nmax.

(5) If No exists, No −Nm1n<Nma
When x - No, return to (2) with Nm1n=No. No-Nm1n≧Nmax - When No, Nmax
= Return to (2) as No.

The processing from (1) to (5) above is due to noise interference h<r
Although this is a measure for relieving such cases, it is not particularly limited to this method.

4) Proceed roughly to step S6 and determine the multiplication constant for data expansion of each of R, G, and B as (maximum level)/max.

Here, the maximum level is the maximum value that a signal value can take, and is, for example, 255 in the case of 8-bit data.

5) Next, in step S7, set the subtraction constant for each offset of R, G, and B (@large level) xmin /max
I decide.

Through the above processing, it is possible to self-help set the white level and black level for each of R, G, [1].
As shown in the figure, the characteristic curve 401 can always have the same shape.

In this way, the R, G, and B signals read from the original image are subjected to appropriate data expansion and offset processing.
Proceeding to step S8, the copying operation is started.

Here, the copying operation will be further explained with reference to FIG. 1A.

The R, G, B signals obtained by the sensor 11 are sent to the amplifier 12, A
It passes through the /D converter 13 and is converted into a digital signal and sent to the subtracter 14.
added to. The subtracter 14 is controlled by the CPo 20 and uses the data from the orange penis RAM 21.
Pure R with orange base subtracted and removed,
The subtracter 14 outputs the data as G and B signal data.

The data of the R, G, and B signals thus obtained is sent to the subtracter 15.
The subtracter 15 is controlled by the CPII 20, and the histogram RAM 22 is input to step s of FIG. 1B.
The offset constant for each color signal obtained in step 7 is subtracted from the corresponding color signal data. And further multiplier 16
Then, the data expansion constant for each color signal obtained in step s6 is multiplied by the corresponding data for each color signal.

The R, G, and B signal outputs of the multiplier 16 are converted into C, M, and Y signals by the logarithmic conversion circuit 17, and are converted into C' by the masking circuit 18.
, M'd' signals and sent to the copying machine.

In this embodiment, since a histogram is taken of the data from which the orange base portion has been removed, data with a wide dynamic range can be obtained.

In this embodiment, a case is shown in which signal processing of offset and expansion of sensor output is performed on a digital signal after A/[) conversion. A similar effect can be obtained by converting, for example, the gain of the analog amplifier of the sensor or the constant of the clamp circuit using the method described above before conversion.

Furthermore, the present invention is applicable not only to color negative films but also to color positive films, black-and-white negative films, black-and-white positive films, and the like.

(Effects of the Invention) As is clear from the above, according to the present invention, when copying a color negative film with a normal color original copying machine, density changes due to the exposure conditions at the time of photographing the color negative film and color balance due to the illumination light source. It is possible to always obtain a stable color copy image despite changes in gamma characteristics and film base color due to differences in film manufacturers.

[Brief explanation of drawings]

FIG. 1A is a block diagram showing the configuration of an embodiment according to the present invention, FIG. 1B is a flowchart showing the processing procedure of an embodiment according to the present invention, and FIG. 2 is a R, G diagram of an embodiment according to the present invention. , B histograms, Fig. 3 is a block diagram showing the configuration of a conventional color original copying device, Fig. 4 is a block diagram showing the configuration of conventional color original reading signal processing, and Fig. 5 shows conventional signal values and A characteristic diagram showing the relationship between image reflectance. FIG. 6 is a characteristic diagram of signal values when reading a conventional color negative film. DESCRIPTION OF SYMBOLS 11... Sensor, 12... Amplifier, 13... A/D converter, 14, is... Subtractor, 16... Multiplier, 17... Logarithmic conversion circuit, 18... Masking circuit, 20... CPU, 21... Orange base part RAM. 22...Histogram RAM. 23...ROM. 100...Halogen lamp, 101...Condenser, lens, 102...Negative film, 103...Lens, 104...Bending mirror, 105...Fresnel lens, 106... Original table Glass, 107... Infrared cut filter, 108... Imaging lens, 109... It, G, 8 color separation sensor, 201...
- RGB sensor, 202... Offset circuit, 203... Data expansion circuit, 204... White data, 205... Logarithmic conversion circuit, 206... Masking circuit, 301-304, 401-404--・Characteristic curve. Figure 2: Structure of conventional color original copying device Sheep's traditional words (showing the relationship between direct and image opposite!
Figure i1 Figure 5 Picture 1 Receiver N storage t Lesser Light film output + Transparency 2 of the signal value in the case of conventional color negative film 7 conversion
Figure 6 of 1 boat

Claims (1)

[Scope of Claims] A color image copying apparatus that images a color negative film on a three-color separation sensor, reads it, and copies it, reads a part or all of the projected image of the color negative film, and reads each of the three-color separation signals. a frequency distribution creation means for creating a frequency distribution of signal amplitude values versus occurrence frequencies; means for determining signal amplitude values representing upper and lower limits of image signal amplitude values from the frequency distribution creation means; and said upper limit signal amplitude value. , a calculation means for setting a data expansion constant and an offset constant for each of the three color separation signals using a constant calculated from a lower limit signal amplitude value, and with the data expansion constant and offset constant,
A color image copying apparatus characterized in that the three-color color separation signals are converted and a copying operation is performed.