JPS61269570A - Color discriminator - Google Patents

Abstract

PURPOSE:To discriminate surely an objective color by forming a level ratio of an objective color component to a complementary color component and comparing the level ratio with a prescribed value. CONSTITUTION:A read original 1 is lighted by a light source 2, reflected picture light is reflected in a mirror 3 and given to a luminous flux split device 5 via a red filter 6 and a cyan filter 7, and separated and the image is formed on line sensors 8, 9. Picture signals P1, P2 outputted from the sensors 8, 9 are converted into a ratio corresponding to its level by normalizing circuits 13, 14. Output signals D1, D2 of the circuits 13, 14 are given to a divider 15, where a ratio signal DR is compared with a ratio reference signal from a reference level setting device 17 to form a red discrimination signal RC. Thus, the objective color is discriminated surely.

Description

[Detailed description of the invention] [Technical field] The present invention relates to a color discrimination device that discriminates the color of an image.

[Prior Art] When inputting an image to a facsimile device, an image processing device, etc., it is often convenient if the color information of the image can also be determined.

For example, if a document to be transmitted by a facsimile machine has red writing, a seal, or an underline in red, if this red information can be output, more effective image axis transmission will be possible.

By the way, many methods have been proposed for distinguishing colors in this way, but most of them involve color separation of one color using one filter or the like.

However, if we consider the case of spectroscopy using a red filter to distinguish, for example, red, colors that contain more than a certain amount of red components, such as magenta, may also be discriminated as red, and for this reason, they may not be visually recognized as red. There is an inconvenience that colors other than the identified color are also identified as red.

Also, since the light reflected from paper with a white background is white light, the red component contained in this white light is also received, and the ratio of the red component of the background to the red component of the actual red part is not very large.
There has also been an inconvenience that a portion that is visually identified as red is not clearly identified as red.

[Objective] The present invention has been made to solve the above-mentioned disadvantages of the conventional technology, and an object of the present invention is to provide a color discrimination device that can reliably discriminate a target color.

[Configuration] In order to achieve this object, the present invention determines the target color by forming a level ratio between a target color component and a complementary color component of that color, and comparing the level ratio with a predetermined value. are doing.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an optical system of an image reading apparatus according to an embodiment of the present invention, and this embodiment shows a case where red color is discriminated.

In the figure, an original to be read 1 is illuminated with an image on its reading line by a light source 2, and the image light reflected from the reading line is reflected by a mirror 3 and guided to a lens 4, and then a half mirror or prism. A luminous flux splitting device 5 such as
It is divided into two parts.

The image light thus branched is passed through a red filter 6 with a transmission limit wavelength of 580 nm and a transmission limit wavelength of 620 nm, which transmits light with a wavelength longer than 620 nm, and a cyan filter 6 with a transmission limit wavelength of 620 nm, which transmits light with a wavelength shorter than 620 nm. After being separated through filters 7, images are formed on line sensors 8 and 9.

FIG. 2 shows a color discrimination device according to an embodiment of the present invention. Note that, in this figure, control systems such as the drive control system for the line sensors 8 and 9 and the sub-scanning mechanism, which are not directly related to the present invention, are omitted.

-3= In the figure, image signals PI and P2 output from line sensors 8 and 9 are applied to a normalization circuit 13.14 via an output circuit 11.12.

For example, similar to a well-known shading correction circuit that corrects shading of an image signal, the normalization circuits 13 and 14 use the output levels of the line sensors 8 and 9 when reading a standard white image as a reference value to adjust the output level of the original to be read. It has a function of converting the image signals PI and P2 obtained when reading the image signals into ratios to their levels, and this normalization circuit 13.14 absorbs the difference in transmittance between the red filter 6 and the cyan filter. be done.

The output signals DI and D2 of the normalization circuits 13 and 14 are respectively applied to the divisor input terminal and the dividend input terminal of the divider 15, and the divider 15 executes the operation 02/DI, and the corresponding result is The ratio signal DR is the comparator 1
6 is added to the comparison input terminal.

A reference level setter 1 is connected to the reference input terminal of this comparator 16.
7 is added to the ratio reference signal RR (described later), and the comparator 16 detects that the ratio signal DR is the ratio reference signal R
If the color is equal to or lower than R, a red discrimination signal RC is formed and output to the next stage image signal processing device (not shown).

Now, the inventors measured the above-mentioned ratio for 27 commercially available red writing instruments color samples plotted on the xy color coordinate plane as shown in FIG. We obtained the results as shown in the following table.

From the actual measurements obtained in this way, it was found that the above-mentioned ratios were all 0.4 or less in the areas colored by the red writing utensil.

Therefore, as the ratio reference signal RR marked with "-", 0.
By setting a value corresponding to 4, pixels corresponding to the red portion can be reliably determined.

Further, as shown in FIG. 4, the operations of the divider 15 and the comparator 16 can be realized by one ROM (read only memory) 20.

In this way, by forming the ratio of the target color component to be discriminated and its complementary color component and comparing that value with a predetermined value, the target color can be reliably detected.

Note that the above table is obtained when using the red filter 6 and cyan filter 7 with the characteristics described above. Therefore, when the red filter 6 and cyan filter 7 with different characteristics are combined, , it is necessary to change the setting value of the ratio reference signal RR described above depending on the combination.

In addition, in the embodiment described above, red is discriminated, but 1
The types of colors that can be distinguished are not limited to these; for example,
It can be blue or any other color. However, in this case, it is necessary to actually measure the ratio as described above in advance using a filter that transmits the color component to be determined and a filter that transmits its complementary color component. Furthermore, an apparatus for discriminating a plurality of color components can be configured in a similar manner.

[Effects] As explained above, according to the present invention, a target color can be determined by forming a level ratio between a target color component and a complementary color component of that color, and comparing the level ratio with a predetermined value. This provides the advantage of being able to reliably identify the target color.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an optical system according to an embodiment of the present invention, Fig. 2 is a block diagram showing a color discrimination device according to an embodiment of the present invention, and Fig. 3 is an xy color coordinate plane. FIG. 4 is a block diagram showing a color discrimination device according to another embodiment of the present invention. 5... Luminous flux splitter, 6... Red filter, 7...
Cyan filter, 8, 9... line sensor, 11.1
2... Output circuit, 13.14... Normalization circuit, 15
...divider. 16... Comparator, 17... Reference level setter, 20
...ROM (read only memory). Figure 1 Figure 2

Claims (2)

[Claims] (1) A light branching means for branching the image light on the reading line into a plurality of parts, a plurality of spectral filters for splitting the branched image light into different color components, and receiving the image light that has passed through each of the spectral filters. a plurality of line sensors that output image signals corresponding to each pixel; a normalization means that normalizes the output image signals of the plurality of line sensors according to a reference level corresponding to each of the image signals; and a calculation means for calculating the ratio of the image signals and comparing the obtained ratio with a reference value corresponding to the target color, and outputting the output of the calculation means as color information of the corresponding image signal. A color discrimination device characterized by: (2) A color discriminating device according to claim 1, wherein the spectral filter comprises two spectral filters that transmit a color component to be discriminated and a complementary color component of the color.