JPH04280574A - Color picture reader - Google Patents

Abstract

PURPOSE:To read a color picture or an original with fidelity so as to display the picture onto a color monitor and to attain the same color reproduction onto an optional color monitor. CONSTITUTION:A reference color signal is generated from a reference color signal generating section 1d of a color picture reader and a reference color picture is displayed on a color monitor 3 based on the reference color signal. The reference color picture displayed on the color monitor 3 is led to a color sensor 1a of the color picture reader by an optical guide section 4, a color signal of the reference color picture is outputted from a read circuit 1c and a correction coefficient arithmetic section 1e calculates the color correction coefficient of a color conversion matrix based on the color signal of the reference color picture and the reference color signal. Thus, the color correction section 5 corrects and outputs the color signal read from the original by the color sensor 1a based on the color correction coefficient.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a color image reading device that converts color signals read from a color document into digital signals and outputs the digital signals, and particularly relates to the reading characteristics of a color image reading device and the light emission of a color monitor. The present invention relates to a color image reading device that faithfully converts the color of a document into a digital signal and outputs it without depending on the characteristics.

Color image reading devices used as image input devices for facsimiles and computers are R, G,
It reads the three colors B (red, green, blue) using a CCD image sensor, etc., and recently there has been a desire for further miniaturization, improved operation, higher resolution, and higher reading accuracy. .

0003

2. Description of the Related Art Color image reading apparatuses include a contact type color image reading apparatus and a reduction type color image reading apparatus. FIG. 3(a) is a block diagram of a contact type color image reading apparatus. be. A scanning line (reading line) 13 on the original 11 is illuminated by an illumination device such as a fluorescent lamp 12, and an image on this line is read. The reflected light from the reading line 13 is transmitted to the color sensor 1 by a rod lens array 14 (an arrangement of many thin glass lenses with diameter of approximately 1 mm).
The image is formed on 5. The color sensor 15 has a size equivalent to the width of the original to be read, and has a filter section 15a and a CCD line image sensor that detects the level of light passing through the filter section.
It has a detection element 15b such as a di-sensor. The filter section 15a has red, green, and
It is constructed by arranging three blue filters (R, G, B filters). Therefore, in reading at 16 pixels/mm, one pixel has a pitch of 62.5 μm, and the structure is such that there are three RGB pixels (each pixel has a pitch of 20.8 μm).

[0004] When reading a color image using such a color sensor, the sensor output is RGBRGBRGB.
The three colors are sequentially (serially) input to the reading circuit 16 as shown in FIG. The reading circuit 16 AD converts these sensor outputs into 8-bit digital data (levels 0 to 255) and outputs them as parallel three-color signals R, G, and B.

FIG. 3(b) is a block diagram of a reduction type color image reading device. Similar to the contact type, the scanning line (
The reading line) 13 is illuminated by a lighting device such as a fluorescent lamp 12, and the image on this line is read. The reflected light from the reading line 13 is reduced to 1/1 by the lens 17.
The image is reduced to about 0 and formed on the sensor 19 via the color filter 18.

The color filter 18 includes red, green, and blue filters 18a and 18b corresponding to each pixel of the reading line 13.
, 18c, and when detecting the red signal level of each pixel, the position is controlled so that the optical image from the lens 17 passes through the red filter 18a, and when detecting the green signal level, the optical image from the lens is controlled. The optical image is made to pass through the green filter 18b, and when detecting the blue signal level, the optical image from the lens is made to pass through the green filter 18b. That is, by reading one line of a color image three times, color signals of three colors of RGB corresponding to one pixel can be obtained.

The reading circuit 20 converts the sensor output into 8-bit digital data (levels 0 to 255),
Output as parallel three-color signals R, G, and B. Manuscript 1
Examples of 1 include sheet-like documents and thick books (book type), and the data read from these is processed by a host computer or stored in an external storage device such as a disk device. , and output to a CRT monitor, printer, etc.

FIG. 4 is an explanatory diagram of a desktop type image reading device (image scanner), in which the document cover 30
When turned over, a document table 31 appears, and a sheet-like or book-type document 11 is placed on the document table 31, similar to a copying machine, and the recorded image on the document 11 is read by moving the reading head 32 in the direction of the arrow. Read. As explained in Fig. 3, there are both close-contact type and reduced-type reading principles, as shown in Fig. 4(b).
shows the case of close contact type. Note that the same parts as in FIG. 3(a) are given the same reference numerals.

[0009] Such a desktop type reading device has a relatively fast reading speed (several tens of seconds/A4), can read large documents (A3 to A4) in one go, and Once the original is placed on the original table 31,
After that, just by turning on the switch, it automatically scans the entire surface of the document, saving you time and effort.

These conventional color reading devices are designed (selection of light sources, color separation filters, etc.) with the aim of accurate color reproduction. In other words, the RGB of the color reading device
The reading characteristics are determined by the irradiating fluorescent lamp, the spectral characteristics of the color filter, the sensor sensitivity, etc., so each of these components is selected and designed to faithfully output the colors of the original.

[0011]

A color image read by an image reading device as shown in FIG. 4 may be output to a color monitor. For example, DT can be used to search and display image data in a color filing system, or to process documents.
Now is the time to do things like P (desk top publishing). In these cases, there are individual differences between color monitor devices, and the colors of the displayed images may differ.

For example, the image of the reading result is displayed on a color monitor A.
When displayed on color monitor B, the image becomes reddish, and when displayed on color monitor B, the image becomes yellowish. This cannot be said to accurately reproduce the colors of the original, and the ``feel'' of the image changes. In electronic catalogs, etc., if the color of the original document image and the image reproduced on the monitor device differ, the overall feel of the image will change.
As a result, it becomes impossible to accurately convey the goodness of the product to the viewer. The individual differences between these color monitor devices are
By adjusting the emission gain of the three primary colors of the color monitor,
Although it is possible to adjust it to some extent, there is a problem that it takes a lot of effort to make the adjustment and also that it cannot be adjusted well.

From the above, it is an object of the present invention to be able to faithfully read a color image of a document and display it on a color monitor, and also to be able to output and display the read color image on a color monitor. To provide a color image reading device capable of reproducing the same colors even on a color monitor.

[0014]

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention. 1 is a color image reading device that reads a color image recorded on a document, 3 is a color monitor that displays a color image, and 4 is a reference color displayed on the color monitor.
A light guide section that guides an image to a color sensor 1a of a color image reading device 1, 1a is a color sensor, and 1c is a light guide section that sequentially reads out red, green, and blue color signals for each pixel from the color sensor 1a, and performs AD conversion. The output reading circuit 1d generates color signals of the reference colors (red, blue, green) and sends the reference colors to the color monitor 3.
1e is a reference color signal generation unit for displaying an image; 1e is a correction coefficient calculation unit for calculating a color correction coefficient based on the color signal of the reference color image output from the color sensor 1a and the reference color signal;
f is a color correction section that corrects the color signal output from the color sensor based on a correction coefficient.

[0015]

[Operation] Reference color signal generating section 1d of color image reading device 1
A reference color signal is generated, and a reference color image is displayed on the color monitor 3 based on the reference color signal. The reference color image displayed on the color monitor 3 is guided to the color sensor 1a of the color image reading device by the light guide section 4, and the color signal of the reference color image is outputted from the reading circuit 1c. In step 1e, a color correction coefficient of a color conversion matrix is calculated based on the color signal of the reference color image and the reference color signal. Thereby, the color correction section 5 thereafter corrects the color signal read from the document by the color sensor 1a based on the color correction coefficient and outputs the corrected color signal. In this way, the color correction coefficient is determined based on the reference color signal and the color signal obtained by reading the color image displayed on the color monitor using the reference color signal, and the color correction coefficient is calculated from the original based on the color correction coefficient. Since the color signals to be read are corrected, the color image of the document can be faithfully displayed on the color monitor without depending on the light emitting characteristics or reading characteristics of the color monitor, and the same color can be displayed on any color monitor. Reproduction becomes possible.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Overall Structure FIG. 2 is a block diagram of one embodiment of a color image reading apparatus according to the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In the figure, 1 is a color image reading unit that reads a color image recorded on a document or a reference color image (three color bars of red, green, and blue) displayed on a color monitor. 2 is a computer that performs predetermined processing on the color image data output from the color image reading device 1, stores it, reads it out, or performs editing processing; 3 is a color image output from the computer; a color monitor that displays a color image based on the data; 4 is a light guide section composed of an optical fiber or the like that guides the reference color image displayed on the color monitor to the color sensor of the color image reading device 1; It is. The light guide unit 4 includes a light intake unit 4a that captures a reference color image from the display screen of the color monitor 3, a transmission unit 4b such as an optical fiber that optically transmits the color image, and a transmission unit 4b of the color image reading device 1. It has an optical section 4c that is placed on a document table and inputs a color image to a color sensor.

Color image reading device In the color image reading device 1, 1a is a color sensor;
Reference numeral 1b denotes an optical system (see FIG.
compatible with rod lens arrays and lenses), 1c is color
A reading circuit sequentially reads out red, green, and blue color signals for each pixel from the sensor 1a, performs AD conversion, and outputs them; 1d is a reading circuit that generates red, green, and blue reference color signals RCS, which are reference colors, and outputs them to the color monitor 3; a reference color signal generation unit that displays a reference color image on the
1e is a correction coefficient calculation unit that calculates a color correction coefficient based on the color signal RCS' of the reference color image output from the color sensor 1a and the reference color signal RCS; 1f is a 3×3 correction coefficient calculation unit based on the color correction coefficient; A color correction section 1g performs matrix calculations to correct the color signals output from the color sensor, and a color correction section 1g uses the reference color signal RCS from the reference color signal generation section 1d when calculating color correction coefficients, and a color correction section 1f when reading an original. This is a switching circuit that outputs the color signal CLS from each of the two color image data as color image data.

Reference color signal generation unit The reference color signal generation unit 1d generates the reference color signal RCS so that three red, green, and blue color bars (reference color image) RCP are displayed on the color monitor 3. Output. In addition to red, green, and blue, 8 colors such as white, black, yellow, cyan, and magenta are selected, and 10 colors are selected from a color space that is uniform to the human eye (such as the Munsell color system). It can also be configured to display. Furthermore, when determining the color correction coefficient, all colors may not be displayed at once, but red, then green, and finally blue may be displayed.

Correction coefficient calculation unit The correction coefficient calculation unit 1e calculates the color by using the reference color signal RCS.
The color correction coefficient of the 3×3 color correction matrix is calculated based on the color signal RCS' and the reference color signal RCS when the color bar (reference color image) displayed on the monitor 3 is read. .

Now, let us assume that there are three reference colors, red, green, and blue, and the RGB reference color signals RCS are expressed as follows, and the RGB of red, green, and blue of the reference color image read by the color sensor 1a is expressed as follows. Assuming that the color signal RCS' is, the following equation holds true.

[0022] That is, regarding red

[0023]

[Math 1]

0024 holds, and for green

[0025]

[Math 2]

0026 holds, and for blue

[0027]

[Math 3]

##EQU1## holds true.

Therefore, the correction coefficient calculation section performs (1), (2)
, calculate nine color correction coefficients A1 to A9 from equation (3),
It is input to the color correction section 1f. In addition, when the number of reference colors is 8 colors or 4 or more colors such as 10 colors, the correction coefficient calculation unit 1e calculates the error between the sensor output of the reference color image and the reference color signal using the well-known least squares method. Nine color correction coefficients A1 to A9 of the color correction matrix are determined so as to be the minimum.

Color Correction Section The color correction section 1f corrects the color signal read from the original by 3×3 matrix calculation using the color correction coefficients A1 to A9, and outputs the corrected color signal CLS. That is, the color signals output from the color sensor 1a are divided into Ro, Go, Bo.
Then, the following formula

[0031]

[Math 4]

The color signal CLS(Ro', G
o', Bo'). For example, the color correction calculation is as follows:
This can be done using calculations such as a DSP (digital signal processor), or an L that realizes color correction.
It may also be done using a UT (lookup table).

Overall operation First, the color image displayed on the color monitor 3 is
The light guide section 4 is connected to the display screen of the color monitor 3 so as to guide it to the color sensor 1a of the image reading device 1.
It is placed between the image reading devices 1.

Next, a correction key (not shown) of the color image reading device 1 is pressed. Thereby, the reference color signal generating section 1d generates the reference color signal RCS. Reference color signal RCS
is output from the color image reading device 1 through the switching circuit 1g, and a color bar (reference color image) is displayed on the color monitor 3 via the computer 2.

The reference color image displayed on the color monitor 3 is transmitted through the light guide section 4 and the optical system 1b, guided to the color sensor 1a of the color image reading device 1, and is sent from the reading circuit 1c to the reference color image. The color signal RCS' of the image is sent to the correction coefficient calculation unit 1.
e.

The correction coefficient calculation section 1e calculates 3×3 from (1) to (3) based on the color signal RCS' and the reference color signal RCS.
The color correction coefficients A1 to A9 of the color correction matrix are calculated and input to the color correction section 1f. From the above, the color correction coefficient A
1 to A9 are determined.

Thereafter, when the mode is changed from the correction mode to the reading mode, the color signals read from the original are processed in the color correction section 1f.
The color signal CLS is subjected to the correction calculation of equation (4) and output from the switching circuit 1g.

In the above embodiments, the calculation of color correction coefficients and color correction were performed within the color image reading device, but a unit for performing these operations may be provided outside and connected to the color image reading device. You can also do it.

The present invention has been explained above using examples, but
The present invention can be modified in various ways according to the gist of the present invention as described in the claims, and the present invention does not exclude these modifications.

[0040]

As described above, according to the present invention, a color correction coefficient is determined based on a reference color signal and a color signal obtained by reading a color image displayed on a color monitor using the reference color signal. Since the color signal read from the original is corrected based on the color correction coefficient, the color image of the original can be faithfully read and displayed on the color monitor without depending on differences in the light emitting characteristics or reading characteristics of the color monitor. If you want to use another color monitor, you can reproduce the same color even if there are individual differences between color monitors.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a color image reading device.

FIG. 4 is an explanatory diagram of an image scanner.

[Explanation of symbols]

1. Color image reading device 1a...Color sensor 1c...Reading circuit 1d: Reference color signal generation section 1e...Correction coefficient calculation section 1f...Color correction section 3. Color monitor 4...Light guide section

Claims (1)

[Claims] [Claim 1] Red, green,
In a color image reading device that reads a color image recorded on a document by a color sensor that detects a blue level, a reference color signal generation section that generates a color signal of a reference color;
Reference color displayed on color monitor by reference color signal
a guide section that guides the image to the color sensor of the color image reading device; a correction coefficient calculation section that calculates a color correction coefficient based on the color signal of the reference color image output from the color sensor and the reference color signal; A color image reading device comprising: a color correction section that corrects a color signal output from a color sensor based on a correction coefficient.