JP2002190017A - Image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device capable of making uniform image degradation correction of the whole image. SOLUTION: A main scanning signal generating means 1 counts picture element positions. A filter coefficient generating means 2 computes a filter coefficient according to the counted picture element positions and sets the computed filter coefficient to a filter processing means 3. The filter processing means 3 carries out filter processing by specified convolution operation and delivers data to post-stage image processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image processing apparatus suitable for use in MTF correction of an image signal read by a scanner.

[0002]

2. Description of the Related Art Japanese Patent Application No. 63-244178 discloses a prior art in which a deterioration of a signal in a transmission system is uniformly corrected by filtering by a convolution operation. However, when the degree of deterioration differs depending on the pixel position (when the read image data is locally deteriorated), the MT that uniformly performs the entire image as in the above-described related art is used.
In some cases, the F correction filter cannot uniformly correct an image. For example, in a scanner using a CCD sensor, differences in the mounting accuracy of the CCD sensor and its board and the expansion of the circuit board on which the CCD sensor is mounted due to heat cause image deterioration in the left and right directions in the main scanning direction of image data. May vary in degree.

[0003]

In the case where the degree of signal deterioration in the main scanning direction differs depending on the pixel position as described above, it is necessary to correct the signal deterioration using an MTF correction filter as shown in the prior art. When the degree of correction is determined based on the pixels with a low degree of deterioration, the correction is insufficient for the pixels with a large degree of deterioration, and conversely, when the filter processing is determined according to the pixels with a low degree of correction, However, there is a problem in that pixels that are excessively corrected are generated, and image deterioration cannot be uniformly corrected for the entire image without excess or shortage.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and has as its object to provide an image processing apparatus capable of uniformly correcting image deterioration of an entire image.

[0005]

In order to achieve the above object, an image processing apparatus according to the present invention comprises: an image processing apparatus having a filter processing means for performing MTF correction of an image signal; MTF by location
A change means for dynamically changing the degree of correction is provided.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an image processing apparatus according to the first embodiment of the present invention. This embodiment relates to the first and second aspects of the present invention.
In FIG. 1, an image processing apparatus includes a main scanning signal generating unit 1 that generates a signal indicating a position of image data in a main scanning direction.
A filter coefficient generating means 2 for generating a coefficient of an operation performed in the filter processing in accordance with a signal sent from the main scanning signal generating means 1, and a filter processing using the filter coefficient generated by the filter coefficient generating means 2. And a filter processing means 3 for performing the following.

Here, the number of pixels in the main scanning direction is, for example, 40.
The number of pixels is 96. In the main scanning signal generating means 1, 0, 1, 2, 3, ... 4095 from the head of each line of the image data
And the count signal are sent to the filter coefficient generation means 2 at the next stage.

In the system shown here, for example, it is assumed that the deterioration of the image signal in the central part of the main scanning is small, and the deterioration is large toward the end. In this case, it is assumed that the filter coefficient for performing the most appropriate MTF correction at the pixel near the center (around the 2048th pixel) is as shown in FIG. FIG. 2B shows the most suitable filter coefficient for pixels around the end (0 or 4095) of the line. FIG. 2C shows a coefficient at each position in FIGS. 2A and 2B as a representative, and FIG. 2D shows a pixel value.

In the case of such a system, a filter coefficient for each pixel is obtained by the following equation. 0th pixel ~
Between the 2047th pixel x: Pixel position

From the 2048th pixel to the 4095th pixel, a = b = d = e = -1.0, c = 6.0- (x-2048.0) /2047.0 D '= 1.0 + (x-2048.0) /2047.0 (2) Note) All real number operations

FIG. 3 shows a processing flow. According to the above equations (1) and (2), five filter coefficients a, b, c, d, and e are calculated according to the pixel position. The filter coefficient generator 2 sets the calculated filter coefficient in the filter processor 3. The filter processing means 3 performs filter processing by a convolution operation according to the following equation according to the set coefficients, and passes the data to the subsequent image processing.

From the 0th pixel to the 2047th pixel, (a * s + b * t + c + d * u + e * v) / D (3) Between the 2048th pixel and the 4095th pixel (a * s + b * t + c + d * u + e * v) / D '... (4) Note) All real number operations

Next, a second embodiment of the present invention will be described. The present invention relates to the third aspect of the present invention. In the first embodiment, the filter coefficients are sequentially determined according to the positions of the pixels. For this reason, a multiplication circuit for performing a real number operation is required, which causes a problem that the cost is increased. This embodiment solves this problem.

FIG. 4 is a block diagram showing an image processing apparatus according to the present embodiment. The same reference numerals are given to parts corresponding to those in FIG. 1 and duplicate explanations are omitted. In FIG.
A pixel range determining means 4 is provided in place of the filter coefficient generating means 2 in FIG. Here, the number of pixels in the main scan is 40
It is assumed that there are 96 pixels.

It is assumed that the filter processing means 3 is configured so that the following filters can be selected in advance.
Coefficients as shown in FIGS. 5A to 5E can be selected according to the pixel position signal. 0 to 499: (a) 500 to 1547: (b) 1548 to 2547: (c) 2548 to 3595: (d) 3596 to 4095: (e)

FIG. 6 shows a processing flow. The main scanning signal generating means 1 generates signals of 0 to 4095 indicating the pixel positions of the main scanning, and sets the position signals in the pixel range determining means 4. The pixel range determining unit 4 sets the section index data indicating the pixel range in the filtering unit 3 according to the pixel position data.

The filter processing means 3 selects a filter coefficient in accordance with the above-mentioned section index data, and performs a filter processing operation.

The filter processing means 3 performs a filter operation using the above-described filter coefficients and passes the result to the subsequent image processing.

[0019]

As described above, according to the first and second aspects of the present invention, deterioration of image data due to the reading system can be uniformly corrected, and a good image can be obtained.

Further, according to the third aspect of the present invention, it is not necessary to mount a real multiplier for the filtering process, so that the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an image processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing filter coefficients and pixel values.

FIG. 3 is a flowchart showing an operation according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating an image processing apparatus according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing pixel positions and filter coefficients.

FIG. 6 is a flowchart showing an operation according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main scanning signal generation means 2 Filter coefficient generation means 3 Filter processing means 4 Pixel range determination means

Claims (3)

[Claims] 1. An image processing apparatus comprising a filter processing unit for performing MTF correction of an image signal, wherein a change unit for dynamically changing a degree of MTF correction according to a pixel position of the image signal is provided. Image processing apparatus. 2. The image processing apparatus according to claim 1, wherein the changing unit changes a filter coefficient of the filtering unit according to a pixel position. 3. The changing means divides one line of the image signal into a plurality of sections, determines a filter coefficient corresponding to each section in advance, determines which section a pixel is included in, and determines this determination. 2. The image processing apparatus according to claim 1, wherein a filter coefficient of said filter processing means is determined based on a result.