JPH09200515A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the limitation of minimum value of white reference data and to simplify the configuration of shading correcting operation circuit. SOLUTION: The data on a white reference surface are read by a scanner 1, converted to a digital image signal V11 by an A/D converter 2 and preserved in a following pixel register 3. Next, the next pixel register while reference data are outputted from the scanner 1, converted to a digital image signal V12 by the A/D converter 2 and preserved in the next pixel register 3. At such a time, the signal V11 preserved in the next picture element register 3 is transferred to a current pixel register 4. When the next white reference data are inputted, a signal V13 is inputted to the next pixel register 3, the signal V12 is inputted to the current pixel register 4, and the signal V11 is inputted to a preceding picture element register 5. From the point of time when three signals are arranged, abnormal picture element detecting processing 6 of current pixel data is performed. The average value of pixels V11 and V13 before and after a concerned pixel is calculated, that average value is compared with the current pixel V12 and when the difference is larger than a certain set value, the current pixel V12 is regarded as an abnormal pixel but when the difference is smaller, the current pixel is regarded as a normal pixel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus such as a facsimile apparatus having a shading correction function.

[0002]

2. Description of the Related Art An imaged image is accompanied by a non-uniform background image called shading due to effects of illumination unevenness, lens transmission unevenness, sensor sensitivity unevenness, and the like, so that the object does not serve as quantitative luminance information. . Therefore, by using the image of only the background light, a correction coefficient that makes the background light uniform is obtained for each pixel, recorded in memory, and multiplied by the original image containing the target object to obtain an accurate shading-free image. I am trying to obtain a high brightness image.

For example, in Japanese Unexamined Patent Publication No. 6-164919, an image signal read from an original is converted into digital image data A by an A / D converter, and white reference data is converted from the converted digital image data A. B and a predetermined constant K according to the number of quantization bits of the A / D converter are used to perform an operation by an arithmetic expression of (B × K) / A, and shading is performed on an image read by an image reading device. It is proposed to make a correction.

[0004]

In the above prior art, in order to eliminate the limitation of the minimum value of the white reference data, A /
Although the shading correction is performed by performing an operation using a predetermined constant according to the quantization bit of the D converter, in this method, the shading correction alone increases the number of arithmetic circuits to six.

Further, in the above-mentioned conventional technique, the bit abnormality of the image sensor is detected by comparing the pixel of interest and the preceding pixel, but with this method, the abnormality is detected when the pixel-to-pixel variation is large like a contact sensor. It may be detected.

Further, in the above-mentioned prior art, when a bit error of the image sensor occurs, it is dealt with only by the internal image processing. Therefore, an operator or the like adheres dust to the reading surface or breaks the sensor. I never noticed.

[0007]

According to a first aspect of the present invention, an image processing apparatus equipped with a shading correction function detects a minimum level of white reference data and selects the shading correction data according to the detection result. The present invention is characterized in that it has an equivalent function with a simpler configuration than the configuration of a single arithmetic circuit.

According to a second aspect of the present invention, in an image processing apparatus equipped with a shading correction function, when the white reference data is read, the average value of the pixels before and after the pixel of interest is taken, and the average value and the pixel of interest are taken. Characterized by detecting a bit abnormality of the image sensor by comparing,
Therefore, the accuracy of bit anomaly detection is improved by comparing the average value of the pixel of interest and the pixels before and after it.

According to a third aspect of the present invention, in an image processing apparatus equipped with a shading correction function, an abnormal state of the image sensor is detected based on the minimum level detection result of the white reference data and the bit abnormality detection result of the image sensor. Therefore, an abnormal display is displayed on the display unit.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a principal block diagram for explaining an embodiment of an image processing apparatus according to the present invention, and FIG.
Is a flow chart for explaining its operation. In the figure, reference numeral 1 is a scanner for reading an original, and after the level of an image signal V ₀ output by this scanner is optimized by a video amplifier circuit, A / The D converter 2 converts the image signal V ₀ into a digital image signal V ₁ . First,
In order to capture the shading correction data, the scanner 1 reads the data of the white reference plane. The scanner output image signal V ₀₁ of the read white reference data is converted into a digital image signal V ₁₁ by the A / D converter 2 and stored in the next pixel register 3. Next, the next pixel register white reference data V ₀₂ is output from the scanner, converted into a digital image signal V ₁₂ by the A / D converter 2, and stored in the next pixel register 3. At this time, V ₁₁ stored in the next pixel register 3 is transferred to the current pixel register 4.

[0011] Then, upon entering the next white reference data, the next pixel register 3 contains the V _13, V ₁₂ to the current pixel register 4, before entering the V ₁₁ in the pixel register 5, three uniform time Abnormal pixel detection processing of the current pixel data is performed by the abnormal pixel detection circuit 6. Here, first, the next pixel register 3
If the difference is larger than a certain set value by calculating the average value of the pixels V ₁₁ and V ₁₃ before and after the pixel of interest stored in the previous pixel register 5 and comparing the average value with the current pixel V _12. Regards the current pixel V ₁₂ as an abnormal pixel, and if it is small, regards it as a normal pixel. If it is an abnormal pixel,
The average value of the previous pixel and the next pixel is replaced with the current pixel for output. By the replacement, even if the current pixel becomes an abnormal pixel due to dust or the like, it is possible to obtain more optimal white reference data by taking the middle value of the preceding and following pixels.

When abnormal pixel detection is detected, the abnormal pixel detection counter 13 counts the number of abnormal pixel detections,
Depending on the value of this counter and the value of the minimum hold register 8, a warning such as dust adhesion or image sensor failure is displayed on the display. When the value of the counter 13 exceeds a certain set value and the value of the minimum hold register 8 is less than the certain set value, the instruction for issuing a warning is CP.
Issued by U. After the abnormal pixel correction is performed, the peak hold register 7 detects the peak value of the white reference data, and the minimum hold register 8 detects the minimum value of the white reference data. This sets the white reference plane to 2
The peak value and the minimum value are detected in the first reading, and the shading correction data is detected in the second reading by using the detected peak value and the minimum value.

The detection of the peak value and the minimum value is performed over the entire range of the white reference reading surface, and when the new peak value and the minimum value are detected, the values are stored in the respective registers. For the detection, the peak value is detected by the multiplexer 9,
Alternatively, the current pixel data is selected and output, and the multiplexer 10 selects and outputs the minimum value or the current pixel data. When a peak value is detected, the multiplexer 9 outputs the peak value and the multiplexer 10 outputs the current pixel data. When the current pixel is large, the current pixel data is stored in the peak hold register 7.

When the minimum value is detected, the multiplexer 9
More current pixel data, the minimum value from the multiplexer 10 is input to the adder 11 for calculation, and when the current pixel is small,
The current pixel data is stored in the monitor hold register 8. The calculation result is stored in the calculation result register 12, and the next calculation method is selected according to the value of this register. Then, by removing the detected minimum value by the peak value, the correction method for shading correction is selected based on the result.

As an example, when the bit number of the digital image signal is 8 bits and the data of the shading correction data stored in the RAM 15 is 6 bits,
When the peak value is 240 and the minimum value is 180, first, since the minimum value has reached 75% of the peak value, bits 7 and 6 of the shading correction data are fixed to 1. By storing the operation result in bit 5 to bit 0, the dynamic range becomes 6
4, which is larger than the difference 60 between the peak value and the minimum value. When the peak value is 240 and the minimum value is 80, only 30% of the minimum value is reached,
In this case, if bit 7 of shading correction data is fixed to 1, correction of 50% or less cannot be performed, so the operation result is stored in bit 7 to bit 2, and 1 or 0 is fixed in bit 1 and bit 0. By doing so, a dynamic range of 160 can be secured. Instead, since bit 1 and bit 0 are fixed, the correction accuracy is
64/160 = 40%. The selection of the number of bits to be stored and the fixing of the number of bits are performed in the memory I / F 14, and the selection of the number of bits is determined by the division result of the peak value and the minimum value. I /
Confirm the setting by looking at the O bit number select port. Also, the peak hold register and minimum hold register can be confirmed by the I / O port.

[0016]

According to the first aspect of the present invention, by detecting the minimum level of the white reference data and setting the dynamic range of the shading correction, there is a restriction that what percentage of the peak value of the white reference data is corrected. Since it is unnecessary, it is possible to eliminate the limitation on the minimum value of the white reference data and to simplify the circuit.

According to the second aspect of the present invention, by comparing the average value of the pixel of interest and the pixels before and after the pixel of interest to detect the bit abnormality of the image sensor, a scanner such as a contact sensor having a large variation in each pixel. The accuracy of bit abnormality detection of is improved.

According to the invention of claim 3, the detection of the minimum level of the white reference data and the detection of the bit anomaly are displayed on the display unit, so that dust adheres to the reading surface.
Also, it is possible to give a warning such as a failure of the image sensor.

[Brief description of drawings]

FIG. 1 is a principal block diagram for explaining an embodiment of an image processing apparatus according to the present invention.

FIG. 2 is a flowchart for explaining the operation of the image processing apparatus according to the present invention.

[Explanation of symbols]

1 ... Scanner (including video amplifier circuit), 2 ... A / D converter, 3 ... Next pixel register, 4 ... Current pixel register,
5 ... Previous pixel register, 6 ... Abnormal pixel detection circuit, 7 ... Peak hold register, 8 ... Minimum hold register,
9, 10 ... Multiplexer, 11 ... Adder, 12 ... Operation result register, 13 ... Abnormal pixel detection counter, 14 ... Memory I / F, 15 ... RAM.

Claims (3)

[Claims] 1. An image processing apparatus equipped with a shading correction function, wherein a minimum level of white reference data is detected, and shading correction data is selected according to the detection result. 2. An image processing apparatus equipped with a shading correction function, when reading white reference data, obtains an average value of pixels before and after a pixel of interest, and compares the average value with the pixel of interest. An image processing device characterized by detecting a bit abnormality of an image sensor. 3. An image processing apparatus equipped with a shading correction function, wherein an abnormal state of the image sensor is detected based on a minimum level detection result of white reference data and a bit abnormality detection result of the image sensor. Processing equipment.