JP2954231B2 - Color image processing method and color image processing apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color image processing method and a color image processing apparatus.

[Prior Art] As shown in FIG. 7, in order to correct color shift in the color sensor shown in FIG. 6, the position shift of the color sensor 1 is shifted to green (G) and red (R) centering on the blue (B) component. Has been proposed to correct the positional deviation of each color component by linear primary interpolation of the following equations (1) and (2).

Reference numeral 2 denotes an A / D converter for converting an output digital signal of the color sensor 1; 3, an arithmetic circuit of Expression 1; 5, an arithmetic circuit of Expression 2; and 6, a delay circuit for adjusting delays by the arithmetic circuits 3 and 5. is there.

[Problems to be Solved by the Invention] According to the conventional method described above, as the frequency of the document image approaches the reading cycle of the color sensor as shown in FIG. Gn ', Rn') and the uncorrected color component (Bn) cause a difference in resolution, and the difference in resolution causes a color shift, resulting in poor resolution of a black thin line.

An object of the present invention is to provide a color image processing method and a color image processing apparatus which have solved the above problems.

The present invention has considered the following points. That is, as shown in FIG. 2, when the correction of only the phase of each color component of the color sensor is performed, assuming that the color component without smoothing, that is, the MTF characteristic of the center color component (Bn) of the color misregistration correction is 100%, 1, color components (Gn ', R
Since n ′) is equivalent to performing a 1: 2 smoothing operation, the deterioration of the MTF characteristic for a color component that is not subjected to color shift correction causes a rounded color balance, resulting in image deterioration.

Means for Solving the Problems In view of the above points, and in order to achieve the above object, the present invention provides a color sensor in which a plurality of elements corresponding to a plurality of color components are arranged on a line. From, the image data obtained by the element, the image data composed of the plurality of color components indicating the desired pixel is input, the phase and MTF characteristics of the plurality of color components constituting the image data indicating the desired pixel are Phase correction and MTF characteristic correction are performed on each of the plurality of color components so as to substantially match each other, and the plurality of color components subjected to the phase correction and the MTF characteristic correction are image data indicating the desired pixel. Are output as a plurality of color components.

Further, the present invention, from a color sensor in which a plurality of elements corresponding to each of a plurality of color components are arranged on a line, inputs image data composed of the plurality of color components indicating a desired pixel, and The phase and the MT for each of the plurality of color components so that the phase and the MTF characteristics of the plurality of color components constituting the image data representing a pixel substantially coincide with each other.
The correction means for correcting the F characteristics, the plurality of color components whose phase and MTF characteristics have been corrected by the correction means,
The image data representing the desired pixel is output as a plurality of color components.

[Operation] According to the present invention, the phase correction and the MTF characteristic correction are performed on each of the plurality of color components so that the phases and the MTF characteristics of the plurality of color components constituting the image data indicating the desired pixel substantially match each other. And outputs the plurality of color components subjected to the phase correction and the MTF characteristic correction as a plurality of color components constituting image data representing the desired pixel, thereby improving the read image quality.

Examples Hereinafter, the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a drawing showing an embodiment of the present invention. In FIG. 1, reference numeral 4 denotes an arithmetic circuit which performs smoothing at a ratio of 1: 6: 1. Equation 3 is corrected. Other configurations are the same as in FIG.
According to such a configuration, as shown in FIG.
MTF characteristics by 1: 2 smoothing operation circuits 3 and 5
The MTF characteristics by the 1: 6: 1 smoothing operation circuit 4 are almost the same. Therefore, by matching the phase of each color component with the MTF characteristic, it is possible to correct a color shift in the high-frequency image, thereby improving the color resolution and improving the image quality of the color image.

Embodiment 2 FIG. 3 is a drawing showing another embodiment of the present invention, in which 7 is a document, and 8 and 9 are lenses.

In the second embodiment, the lens 9 of the color component (Bn) not subjected to the color shift correction is equivalent to the MTF characteristic by the 1: 2 smoothing in FIG. 2 for the lens 8 of the color component (Rn, Gn) for which the color shift is corrected. By using the following, the color shift in the high-frequency image can be corrected, and the image quality of the color image is improved.

Third Embodiment FIG. 4 is a drawing showing a third embodiment of the present invention, in which 10 is a programmable smoothing circuit, and 11 is a CP.
CPU unit including U, ROM, RAM, I / O, etc.

In the third embodiment, parameters for correcting the G, B, and R signals from the A / D converter 2 according to Expressions 4, 5, and 6 shown below are set.
The setting of the smoothing circuit 10 by the CPU unit 11 corrects the color shift of the color sensor.

FIG. 5 is a diagram showing an example of a circuit configuration of the smoothing circuit 10. The parameters of the equations 4, 5, and 6 can be set in the multiplier 12 and the divider 14 by the CPU unit 11. 13 is an adder, and 15A, B and C are latches. The smoothing circuit 10 samples three pixels to perform smoothing. The number of samplings may be four or five pixels, and if the smoothing process is performed to match the phase of each color component and the MTF characteristic, the scope of the present invention will be described. Clearly within.

The one having a programmable smoothing circuit as in the third embodiment also has an effect of preventing the occurrence of moire by setting a parameter that prevents the occurrence of moire in the image reading apparatus.

[Effects of the Invention] As described above, according to the present invention, the MT of each color component
By making the F characteristics substantially coincide with each other, it is possible to eliminate the difference in the MTF characteristics that occurs when the phase correction of the color components is performed, and to improve the read image quality.

[Brief description of the drawings]

1 is a block diagram of Embodiment 1 of the present invention, FIG. 2 is a diagram showing MTF characteristics, FIG. 3 is a diagram showing an outline of Embodiment 2 of the present invention, FIG. 4 is a block diagram of Embodiment 3 of the present invention FIG. 5, FIG. 5 is a block diagram of a smoothing circuit, FIG. 6 is a diagram showing the structure of a color sensor, FIG. 7 is a block diagram of a conventional color image reading device, FIG. FIG. 4 is a diagram showing a relationship with a frequency of FIG.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Mitsuru Kurita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-63-61580 (JP, A) JP-A-63 −177655 (JP, A) (58) Fields surveyed (Int.Cl. ⁶ , DB name) H04N 1/40-1/409 H04N 1/46 H04N 1/60

Claims (4)

(57) [Claims] An image data composed of a plurality of color components indicating a desired pixel, obtained from a color sensor in which a plurality of elements corresponding to each of a plurality of color components are arranged on a line. The phase correction and the MTF characteristic correction are performed on each of the plurality of color components so that the phases and the MTF characteristics of the plurality of color components constituting the image data indicating the desired pixel substantially match each other. A color image processing method, comprising: outputting the plurality of color components subjected to the phase correction and the MTF characteristic correction as a plurality of color components constituting image data indicating the desired pixel. 2. A phase correction of second and third color components centering on a first color component in the image data indicating the desired pixel, and the second and third color components subjected to the phase correction are corrected. 2. The MTF characteristic of the first color component is corrected so that the MTF characteristic of the first color component is substantially the same as the MTF characteristic of the third color component.
3. The color image processing method according to item 1. 3. An image data comprising a plurality of color components indicating a desired pixel is inputted from a color sensor having a plurality of elements corresponding to each of a plurality of color components arranged on a line, and said desired pixel is inputted. Having a correcting means for correcting the phase and the MTF characteristic for each of the plurality of color components so that the phase and the MTF characteristic of the plurality of color components constituting the image data indicating each other substantially coincide with each other. A color image processing device, wherein the plurality of color components whose phase and MTF characteristics have been corrected are output as a plurality of color components constituting image data indicating the desired pixel. 4. The image processing apparatus according to claim 1, wherein said correction means is configured to output a second and third image data centered on a first color component in the image data representing the desired pixel.
And correcting the MTF characteristics of the first color component so that the MTF characteristics of the second and third color components are substantially the same as the corrected MTF characteristics of the second and third color components. The color image processing apparatus according to claim 3, wherein