MXPA97001312A - Apparatus for digital correction in an ima system - Google Patents

Abstract

The present invention relates to an apparatus for digital correction in an imaging system comprising: pre-processing element for adjusting the direct current gain of an image signal, an analog to digital converter for converting the adapted image signal a digital signal; a bit-increasing element for generating an increased bit signal in accordance with the digital signal and a plurality of nearby pixels; and post-processing elements for generating an image code by processing the increased bit signal through Gamma correction, shading, brightness, and darkening

Description

APPARATUS FOR DIGITAL CORRECTION IN AN IMAGE SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image system, and more particularly to an apparatus for digital correction in an image system that efficiently improves the taking of an image, preventing it from resulting in a false contour or defect in the image, and reduce the cost as long as it does not compromise the precision bits of the system. Generally the present invention provides an image capture apparatus, an image storage code, a displayed image and a correction pixel by methods such as shading correction, brightness, darkening and Gamma. It will also be used in high-contrast image processing, eg. text, the present invention is highly suitable for image processing without text, e.g. image or photograph, and it is applicable for image explorers. 2. Description of the Prior Art An image system makes use of the focusing of a reflection light beam through a photodetector to generate an image signal for the processing, storage and further display of the image. Among general applications, image scanners, camera recorders or facsimile machines are everywhere from modern offices to homes. Despite a few differences between these machines, there are two main types of imaging systems typical in the prior art, namely analog correction system and digital correction system. A functional block diagram of a typical analog correction in an image system is shown in Figure 1. It comprises a light source 10, a mirror 11, a lens 12, a charge coupled device (DAC) 13, an element of pre-processing, which is implemented as a direct current gain (DC) gain amplifier 14, an analog-to-digital converter (CAD) 15, a digital-to-analog converter (CDA) 16, a post-processing element 17, and an intermediate memorial 18. By using this system, the light source 10 is reflected from the surface of a text or an image that is reflected back from the mirror 11 and is focused by the lens 12, and then becomes to an image signal by the charge coupled device 13, the direct current gain of the image signal is automatically adjusted by the direct current gain voltage amplifier 14 and then fed to the analog-to-digital converter 15, which ref voltage Egress 19 (Vref) is continuously changed in accordance with a correction vector through the digital to analog converter 16 for the reason that the combination of the light source 10, the mirror 11, the lens 12 and the device coupled by load 13 possess a non-uniform response, formally called non-uniform response to light (RNUL); the adjustment of the contrast is carried out by means of a Gamma vector through the post-processing elements 17, and then it is stored in the buffer 18 for further processing or display of the image. There are some drawbacks associated with the typical previous analog correction in an imaging system; (1) although the system bits in the analog-to-digital converter 15 are increased, the bits in the digital-to-analog converter 16 consequently vary, the system of which completely drops slowly due to its high equivalent impedance; (2) for a digital to analog converter 16 with more bits, the cost grows and the availability is lower; (3) the reference voltage setting 19 of the analog-to-digital converter 15 through the digital-to-analog converter 16 will have a slow decrease to the analog-to-digital converter 15 due to the long installation time of the digital to analog converter 16; and (4) the fluctuation of the reference voltage 19 will cause noise, in addition to completely destabilizing the system.

A functional block diagram of a typical digital correction in an image system is shown in Figure 2. The major difference between this and the previous system is the substitution of the digital to analog converter 16 in Figure 1 by a divider 26 in Figure 2 for correcting an adjusted image signal from an analog-to-digital converter 25. Although the typical digital correction method eliminates the drawbacks mentioned above, the use of the divider 26 decreases the precision bits of the system, resulting in a contour. false or image defect. For example, assuming that the bits of the precision system are 8 bits and the non-uniform response to light (RNUL) is 50%, the bits of the system will be decreased by a subsequent shading correction through the divider 26, and will also decrease between two later, v.gr. in brightness correction to 25% of the total scale. At the end, there are 32, that is, 25, image steps instead of 256, that is 2 & , at the beginning, and these steps are lost when they appear as discontinuities in a histogram as shown in Figure 3b which is compared to a histogram in Figure 3a before the correction. Of the visual expression, there are some notable image defects that appear for example, on a photograph.

SUMMARY OF THE INVENTION Therefore, it is a principal object of this invention to provide an improved apparatus for digital correction in an imaging system to improve the efficiency in taking the image, preventing it from producing noise, and reducing the cost. It is a further object of the invention to provide an improved apparatus for correcting the non-uniform response to light (RNUL), which avoids the image defect, although it does not compromise the system precision bits of the system. Accordingly, the present invention provides an apparatus for digital correction in an image system comprising conversion elements for converting the image to an image signal; pro-processing element to automatically adjust the direct current gain of the image signal; an analog-to-digital converter for converting the adjusted image signal to a digital signal; bit increasing element for generating an increased bit signal; post-processing element for generating an image code by processing the increased bit signal through the correction of brightness, dimming, gamma and shading; and a buffer for storing the image code for further processing or display of the image.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a functional block diagram of a typical analog correction in an imaging system. Figure 2 is a functional block diagram of a typical digital correction in an image system. Figure 3a is a normal histogram of image codes. Figure 3b is a histogram of image codes resulting from the system of Figure 2. Figure 4 is a functional block diagram of the present invention. Figure 5a is the method for calculating the bit increment element with dimension 3x3. Figure 5b is the method for calculating the element to increase the bit with 1x3 dimension. Figure 5c is the method for calculating the bit incrementing element with 1x5 dimension. DESCRIPTION OF THE PREFERRED MODALITY A functional block diagram of the present invention is shown in Figure 4. It comprises a light source 39, a mirror 41, a lens 42, a charge coupled device (DAC) 43, an element of preprocessing, which is implemented as a direct current gain voltage amplifier 44, an analog-to-digital converter (CAD) 45, a bit enhancer element, which is implemented as a matrix filter 46, a post-processing element 47, and a buffer 48. By using this system, the light source 39 is reflected from the surface of a text or an image 40., being reflected back from the mirror 41, and being focused by the lens 42, and then converted to an image signal by the charge coupled device 43, in order to compensate for the fluctuation of the image signal or aging of the device coupled by load 43, the direct current gain of the image signal is automatically adjusted by the direct current gain voltage amplifier 44 and then fed to the analog-to-digital converter 45 to convert the adjusted image signal to a digital signal . The matrix filter 46, which is characterized in this invention, is used for the generation of an increased bit signal by performing the calculation in accordance with the digital signal and the nearby pixels 49, and is designed to avoid a decrease in the bits of system accuracy. The first example of the calculation method shown in Figure 5a is the filter 46 matrix with 3x3 dimension. The steps for generating an increased bit signal in that example are as follows: (a) calculate a first average of eight nearby pixels around a22í and (b) calculate a second average of the first average and the pixel 22- previous stages of the generation of an increased bit signal, the accuracy bit system increases by four, and they are sufficient for corrections without producing any defect in the image. Due to the extended use of the linear load coupled device which simplifies the system and reduces the cost, the second example of the calculation method as shown in Figure 5b is for the matrix filter 46 with 1x3 dimension. The steps for generating an increased bit signal in this second example are similar to those in Figure 5a except that an average of two neighboring pixels is calculated around a2 instead of eight nearby pixels, and the system is increased by two bits instead. of four. The third example shown in Figure 5c demonstrates the steps of generating an increased bit signal when calculating a rated average, for example (0.5 x ac, + a! + A3 +0.5 x a4) +3, where 0.5 is a Weight coefficient, after calculating an average of the weighted average and the pixel a2. The increased bit signal is then fed to the post-processing elements 47, which is implemented by a splitter / multiplier: Due to the non-uniform response to light (RNUL) of the combination of the mirror 41, the lens 42, the load-coupled device 43, and especially light source 39, an image system applied in an image scanner is instructed to scan a white board before use and the scanned pixels are stored as shading vector 50 for later use. In addition, the brightness vector 51, the darkening vector 52 or the Gamma vector 53 could optionally be fed to the post-processing element 47 to correct the increased bit signal and generate an image code, which is then fed into the memory intermediate 48 for processing or displaying additional image. Consequently, the present invention provides an apparatus that eliminates the drawbacks such as a delay system, of high cost, prone to noise and with image defect. Although the specific embodiments have been illustrated and written it will be obvious to those skilled in the art that various modifications may be made, such as the variation of the matrix filter dimension and weight coefficient, without departing from the spirit intended to be limited only. by the appended claims.

Claims (19)

1. An apparatus for digital correction in an image system comprising: pre-processing element for adjusting the direct current gain of an image signal; an analog-to-digital converter for converting the adapted image signal to a digital signal; a bit incrementing element for generating an increased bit signal in accordance with the digital signal and a plurality of nearby pixels; and post processing elements to generate an image code by processing the increased bit signal through Gamma correction, shading, brightness, and dimming.

2. The apparatus according to claim 1, wherein said pre-processing element is a direct current gain voltage amplifier.

3. The apparatus according to claim 1, wherein said bit incrementing element further performs the calculation to generate said increased bit signal.

The apparatus according to claim 3, wherein said bit enhancing element is a matrix filter with dimension m x n, where m and n are positive integers.

5. The eiparato in accordance with the claim 4, wherein said matrix filter has dimensions 3x3.

6. The apparatus in accordance with the claim 5, wherein said matrix filter performs the calculation comprising the steps of: (a) calculating a first average of the eight nearby pixels; and (b) generating said increased bit signal by calculating a second average of the first average and the value of said digital signal.

The apparatus according to claim 4, wherein said matrix filter has the dimension 1x3.

8. The apparatus according to claim 1, wherein said post-processing element is a divider.

9. The apparatus according to claim 1, wherein said post-processing element is a multiplier.

The apparatus according to claim 1, wherein said post-processing element further responds to a shading vector to correct the shading phenomenon.

11. The apparatus according to claim 1, wherein said post-processing element further responds to a Gamma vector for correction of the image contrast.

12. The apparatus according to claim 1, wherein said post-processing element further responds to a brightness vector.

The apparatus according to claim 1, wherein said post-processing element further responds to a darkening vector.

The apparatus according to claim 1, further comprising a buffer for storing said image code.

15. The apparatus according to claim 1, further comprising a converter element for converting the image to said image signal.

16. The apparatus according to claim 15, wherein said converter element comprises at least one device coupled with load.

17. An apparatus for digital correction in an imaging system comprising: a load-coupled device for converting image to an image signal; direct current gain voltage amplifier for adjusting the direct current gain of the image signal to compensate for the fluctuation of the image signal or aging of the coupled device with load; an analog-to-digital converter for converting the adjusted image signal to a digital signal; a matrix filter with mxn dimension, where m and n are positive integers, which generates an increased bit signal in accordance with the digital signal and a plurality of nearby pixels; post-processing element for generating an image code by processing the increased bit signal in response to a shading vector, a gamma vector, a brightness vector, and a darkening vector; and a buffer to store the image code.

18. The apparatus according to claim 17, wherein said matrix filter has the dimension of 3x3, and said matrix filter performs the calculation comprising the steps of: (a) calculating a first average of the eight nearby pixels; and (b) generating said increased bit signal by calculating a second average of the first average and the value of said digital signal.

19. The apparatus according to claim 17, wherein said post-processing element is a divider or a multiplier.