KR100250360B1 - The preprocessor of an image input apparatus and image distortion correcting method - Google Patents

Abstract

PURPOSE: The preprocessor of an image input unit and the method for compensating the image distortion by using the preprocessor is provided to minimize the chip size, to reduce the cost, and to minimize the error, by using an ADC (Analog/Digital Converter) for the excellent output. CONSTITUTION: The method comprises the following steps. The ADC converts the image signal into the digital data, which is orderly stored to the black compensation memory, and the black compensated data is created(S11). The Max detector finds the maximum value by comparing the digital data with the previous pixel value in size(S12). The detected digital data is orderly stored to the white compensation memory and the white compensated data is created(S13). The digital data, created by scanning the original image, is simultaneously processed by the black and the white compensation(S20). Finally, the ADC outputs the digital image data(S30).

Description

A preprocessor of an image input device and an image distortion correction method using the same.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input apparatus. More particularly, the present invention relates to an image input apparatus for obtaining an excellent output image by performing black and white correction processing on an analog image signal output from a charge coupled device (CCD) sensor. A processor and an image distortion correction method using the same.

In general, a scanner reflects light from a light source onto a document and reflects the reflected light to an image reading such as a charge coupled device (CCD) or a contact image sensor (CIS). The sensor converts it to an electrical output. On the other hand, the converted output value generally serves to be stored in a data storage device such as a hard disk of a computer.

As such, a scanner that reads the contents of documents such as documents and books may be manufactured as a single piece to be used exclusively for scanning, or may be configured as a single device of a multifunction device together with a copy machine and a fax machine.

The analog signal output from the CCD sensor, a photoelectric conversion device of a general color image processing apparatus, includes variations due to individual differences between pixels of a CCD sensor, a semiconductor element, and emits light such as a fluorescent lamp or a halogen lamp used as a light source. And deterioration of image quality in reading an input image due to distortion of the white reference plate or the like.

In order to prevent the deterioration of the image quality due to such circuit elements and components, the color image input device performs black correction to correct individual differences according to the device characteristics of the CCD sensor, a light source (fluorescent lamp or halogen lamp) and a white reference plate. Back correction is performed to remove the effects of distortion.

In general, a distortion correction process of a color image input device is performed in three steps.

First, black correction processing for acquiring black correction data that reads the magnitude of the dark current output from the pixel itself of the CCD sensor when no light is input to the CCD sensor, and subtracts the analog signal output from the CCD sensor by the correction data size. And a maximum value detecting step of applying power to the light source, performing a black correction process on the analog signal reflected on the white reference plate, and reading the maximum value of the output image signal; The back of the analog signal reflected on the back is detected by detecting the distortion of the light source and the white reference plate within the range of the maximum value detected in the maximum value detection step and the black reference voltage, and performs a uniform operation based on the back correction data generated. There is a correction process step.

1 is a configuration diagram showing a conventional preprocessor circuit configuration.

As shown, conventionally, while driving a CCD sensor in a state where power is not applied to a light source and outputting an analog image signal, an analog-to-digital converter (abbreviated as 'A / D converter' hereinafter referred to as 'A / D converter') 101 ) Performs an operation for acquiring black correction data, and converts the analog image signal output from the CCD sensor into digital data within the range of the black reference voltage (V _Bref ) and the black maximum voltage (V _Bmax ) and converts it into digital data. Save to 102.

The black correction memory 102 has a capacity equal to the number of effective pixels of the CCD sensor, and the black correction data is sequentially stored according to the output synchronization signal of the CCD sensor. The A / D converter 101 operates to be used only in the black correction data detection operation.

Next, power is supplied to the light source so that the reflected light reflected from the white reference plate is input to the sensor, and the data detected in the black calibration data detection operation is converted into a digital / analog converter (DAC: 'D / A converter'). D) to an analog value, the black compensator 104 performs a black correction operation by subtracting the size of the black correction data from the output signal of the CCD sensor.

The analog image signal of which black correction processing is completed is input to the A / D converter 105 for detecting the maximum value, and converted into a digital value in the range of the white maximum voltage (V _Wmax ) and the black reference voltage (V _Bref ). The data is compared with the magnitude of the maximum pixel data value detected immediately before in the maximum value detector 106 to detect the maximum pixel data value to complete the maximum value detection operation.

Next, power is supplied to the light source so that the reflected light reflected on the white reference plate is input to the sensor, and when the black calibration is completed, the black reference voltage (V _Bref ) and the maximum value detected by the maximum value detector (V _PEAK ) are input. The back correction data detection operation is performed as the A / D converter 107 converts the digital data into the digital data and stores it in the back correction memory 108 within the range of.

Therefore, in the case of performing an operation of reading an actual document image, power is supplied to a light source so that the reflected light reflected on the original is input to the sensor, and the analog signal output by photoelectric conversion according to the reflected light is input to compensate for black. The data stored in the black calibration memory 102 is provided to the black calibrator 104 via the D / A converter 103 to perform the black calibration operation.

In addition, in order to perform back correction, data stored in the back correction memory 108 is provided to the back corrector 110 via the D / A converter 109 to perform the back correction operation.

The distortion-corrected image signal is finally converted into digital image data within the range of the black reference voltage V _Bref by the A / D converter 111 and the maximum value V _PEAK detected by the maximum value detector. To read the data as digital data.

Here, in the case of a color image input device that is currently being commercialized, a circuit for performing distortion correction processing, which is essentially used, is made into an application specific integrated circuit (ASIC). Applied as circuit elements.

However, in the conventional distortion correction processing circuit, when a large number of A / D converters and D / A converters are used and ASIC is used, the circuit configuration becomes complicated, and as the size of the chip increases, power consumption increases, and the chip The die size, which is closely related to the manufacturing cost of, increases, which contributes to the cost increase.

In addition, the current trend that the image quality of the color image input device is mainly focused on, the resolution of the A / D converter converting an analog signal to a digital signal is increasing, the resolution of the A / D converter is usually 1 bit If the chip size increases, the chip size may be doubled up to two times. Therefore, using a plurality of A / D or D / A converters may not reduce the chip size.

Accordingly, the present invention was devised to solve such problems, and an object of the present invention is to simply design and apply a circuit that performs the same function, thereby reducing the burden of cost and stably performing circuit operation. Especially, in case of A / D converter, since it has close correlation with chip area according to the bit resolution applied to the circuit, it is possible to design a chip with multifunctional addition by reducing the number of A / D converters to a minimum. In addition, the mutual interference effect is small so that a stable signal processing effect can be obtained.

1 is a block diagram showing a conventional preprocessor circuit configuration,

2 is a block diagram showing a circuit configuration of a preprocessor according to the present invention;

3 is a system configuration diagram of an apparatus to which the present invention is applied;

4 is a flowchart showing an image data correction processing procedure according to the present invention.

<Description of the code | symbol about the principal part of drawing>

101,105,107,111,301: Analog / Digital Converter (ADC)

102,308: Black correction memory

103,109,302,303: Digital / Analog Convertor (DAC)

104: black correction unit 106,310: maximum value detector

108,309: Back correction memory 110: Back correction device

304,305: Latch 306,307: Selector

501: scanner control unit 502: ROM

503: RAM 504: color CCD sensor

505: buffer 506: multiplexer

507: analog switch 508: amplifier stage

509 preprocessor 510 memory buffer

511: interface 512: sensor driver

513: lamp driver 514: lamp

515: step motor 516: optical module

517: computer

According to an aspect of the present invention, there is provided an A / D converter for converting a control signal input from a control unit of an image input apparatus and an analog image signal detected by an image reading sensor of the image input apparatus into digital data; D / A converters which generate reference voltages when the / D converter performs an A / D conversion operation and provide them to the A / D converters, and store digital data of the reference voltages before storing the D / A converters. A latch provided as an input of the input, a black correction memory for storing black correction data output by performing an A / D conversion operation in the A / D converter, and an A / D conversion operation in the A / D converter. A back correction memory for storing the back correction data, a maximum value detector for detecting the maximum pixel data value in the black correction memory, a control signal input from the controller and the A / D conversion Depending on the mode of operation is characterized in that it comprises a selector for setting the reference voltage.

Preferably, the control signal is a black correction value generation mode selection signal, a maximum value detection mode selection signal, a back correction value generation mode selection signal, and an original image read mode selection signal.

Advantageously, said D / A converters comprise a first D / A converter for generating an upper reference voltage while said A / D converter performs A / D conversion, and said A / D converter performs A / D conversion. And a second D / A converter for generating a lower limit reference voltage during performance.

Preferably, the selectors are provided to the A / D converter and a first selector for selecting an upper limit reference voltage provided to the A / D converter according to a control signal input from the controller and the operation mode of the A / D converter And a second selector for selecting the lower limit reference voltage according to a control signal input from the controller and an operation mode of the A / D converter.

The image distortion correction method of the present invention for achieving the above objects comprises the steps of: generating reference data for image distortion correction; simultaneously performing black and white correction on an original image using the reference data; And outputting the original image that has undergone black correction and white correction as digital image data.

Preferably, the generating of the reference data includes generating black correction data for correcting a deviation due to individual difference according to device characteristics of an image reading sensor mounted in the image input device, and maximum pixel data in the black correction data. Detecting a value, and generating back correction data for removing the influence of distortion of the light source and the white reference plate mounted on the image input apparatus.

Hereinafter, the objects, features, and advantages of the present invention described above will be described in detail with reference to preferred embodiments of the present invention shown in the accompanying drawings.

2 is a block diagram showing a circuit configuration of a preprocessor according to the present invention.

As shown, the A / D converter 301 for converting the analog output signal of the sensor into a digital signal, and the upper and lower reference voltages during the A / D conversion operation of the A / D converter 301, respectively. Latch 304, 305 which stores the generated D / A converters 302 and 303, and digital data for the upper and lower reference voltages respectively, and a selector operable to select the upper and lower reference voltages according to the operation mode and the selection signal, respectively. 306 and 307, a black correction memory 308 for storing black correction data output from the A / D converter 301, and a back correction memory for storing back correction data output from the A / D converter 301 309 and a maximum value detector 310 for detecting the maximum value using the digital image data output from the A / D converter 301.

3 is a system configuration diagram of an apparatus to which the present invention is applied and illustrates a color image input apparatus by way of example.

As shown, the scanner control unit 501 generates timing signals necessary for performing a series of scan operations for reading the image of the document as digital data and controls the overall operation. The ROM 502 stores a program and reference data having a certain flow so that the scanner controller 501 can control the scanner system in a predetermined order. The RAM 503 stores temporary data generated while the scanner controller 501 controls the system. The lamp 514 outputs R, G, and B tricolor lights in order to read the image information of the document as the reflected light amount by the lamp driver 513 which receives the control signal from the scanner control unit 501. The tricolor light output from the lamp 514 is reflected to the original through the optical module 516 to form a path for input to the photoelectric conversion element, and a focal point is formed on the color charge coupling element sensor 504.

On the other hand, the step motor 515 receives the drive signal from the scanner control unit 501 to move the optical module 516 in the sub-scanning direction of the document at a predetermined resolution. The color charge coupling device sensor 504 photoelectrically converts color information of each of the three primary colors R, G, and B into electrical analog signals in proportion to the amount of light input through the optical module 516. The sensor driver 512 receives a predetermined signal from the scanner controller 501 and supplies a clock signal to the color charge coupled device sensor 504 so that the color charge coupled device sensor 504 operates properly. The buffer 505 transfers an analog signal output from the color charge coupled device sensor 504 to the rear stage and prevents distortion of the sensor signal by the circuit of the rear stage. The multiplexer 506 selects and outputs one of three color information signals simultaneously input according to a signal supplied from the scanner controller 501. The amplifying stage 508 converts the image signal selected and output from the multiplexer 506 into an output signal of a predetermined level and amplifies it according to a predetermined amplification degree to be connected to the input of the preprocessor 509. The analog switch 507 operates to amplify the image signal by selecting an amplification degree for each color according to the signal supplied from the scanner controller 501. The preprocessor 509 receives a signal that is converted into a signal of a predetermined level by the amplifier stage 508, performs black and white correction processing, converts an analog signal, and outputs the digital image data. The memory buffer 510 temporarily stores image data digitally converted by the preprocessor 509. The interface 511 transfers the image data stored in the memory buffer 510 to the computer 517 according to a certain transmission rule.

4 is a flowchart showing an image data correction processing procedure according to the present invention.

First, black calibration data is generated (step S11).

The maximum value of the image signal is detected from the generated black correction data. (Step S12)

After detecting the maximum value, back correction data is generated. (Step S13)

Distortion correction processing is performed on the original image (step S20).

The distortion correction data is output as digital image data. (Step S30)

Hereinafter, the operation of the color image input device of the present invention will be described in detail with reference to FIGS.

The overall operation is divided into four operation steps, which include a black correction data generation operation, a maximum value detection operation, a back correction data generation operation, and an original image reading operation.

First, the selection signal provided from the scanner control unit 501 to the preprocessor 509 to be supplied to the selectors 306 and 307 has a value of 0 in order to perform the black correction data generation operation, and the selected value of each selector is A / D. Inputs are made to two D / A converters 302 and 303 which set the upper and lower reference voltages of the converter 301.

That is, as shown in Table 1, the D value capable of outputting the black maximum voltage is input to the D / A converter 302, and the C value capable of outputting the black reference voltage is input to the D / A converter 303. During the operation of generating black correction data, the A / D converter 301 digitally outputs the image signal input within the range of the black reference voltage V _Bref as the lower limit reference voltage and the black maximum voltage V _Bmax as the upper limit reference voltage. The data is converted into data and stored in the black correction memory 308 sequentially (S11), thereby completing the operation.

Next, the selection signal provided from the scanner control unit 101 to the preprocessor 509 has a value of 1 and is provided to the selectors 306 and 307 to perform the maximum value detecting operation, and the selected value of each selector is an A / D converter. Inputs are made to two D / A converters 302 and 303 which set the upper and lower reference voltages of 301.

That is, as shown in Table 1, the B value capable of outputting the white maximum voltage is selected and input to the D / A converter 302, and is output from the black correction memory 308 to the D / A converter 303. The black correction data is selected and input so that the A / D converter 301 receives the image signal input within the range of the black correction voltage V _BLK as the lower limit reference voltage and the white maximum voltage V _Wmax as the upper limit reference voltage. Convert to

At this time, as the black correction data stored in the black correction memory 308 is interlocked with the pixel synchronizing signal and the correction data for each pixel is output, the black correction is simultaneously processed by the A / D converter 301.

The image data converted into digital data is input to the maximum value detector 310 to perform an operation of detecting the maximum value according to the large comparison with the previous pixel value (S12). As the processing for one line of the CCD sensor is completed, the maximum value detected in the area corresponding to the effective number of pixels of the CCD sensor is provided as one input value of the selector 306.

Next, the selection signal provided from the scanner controller 501 to the preprocessor 509 has a value of 2 and is provided to the selectors 306 and 307 to perform the back correction value generation operation, and the selected value of each selector is A / D. Inputs are made to two D / A converters that set the upper and lower reference voltages of the converter 301.

That is, as shown in Table 1, the maximum value detected by the maximum value detector 310 is selected and input to the D / A converter 302, and is output from the black correction memory 308 to the D / A converter 303. When the black correction data is selected and input, the A / D converter 301 digitally converts the image signal input within the range of the black correction voltage V _BLK as the lower limit reference voltage and the maximum voltage V _PEAK as the upper limit reference voltage. Convert to

The digital data generated in the process is sequentially stored in the back correction memory 309 to complete the back correction data generating operation S13.

When the back correction data generation operation is completed, the color image input device is in a state where all preparation operations have been completed, and the input operation of the original image can be actually started.

When the document is fixed and the document reading operation is started, the selection signal provided from the scanner control unit 501 to the preprocessor 509 has a value of 3 and is provided to the selectors 306 and 307, and the value selected by each selector is A. Inputs are made to two D / A converters 302 and 303 which set the upper and lower reference voltages of the / D converter 301.

That is, as shown in Table 1, the back correction data output from the back correction memory 309 is selected and input to the D / A converter 302, and the black correction memory 308 is input to the D / A converter 303. When the black correction data to be output is selected and input, the A / D converter 301 digitally outputs the image signal input within the range of the black correction voltage V _BLK as the lower limit reference voltage and the back correction voltage V _WHT as the upper limit reference voltage. Convert to data.

As such, the digital data generated in the document image reading process is performed simultaneously with the black correction process and the white correction process, thereby performing a desired correction operation (S20) with a simple circuit configuration.

Mode and high / low reference voltage according to the input value of the selector. division Selection value 0 One 2 3 Operation mode Create black correction value Maximum value detection Create Back Compensation Original image reading Upper voltage selection V _Bmax: A V _Wmax: B V _PEAK V _WHT Lower voltage selection V _Bref: C V _BLK V _BLK V _BLK

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will appreciate that the present invention may be modified without departing from the spirit and scope of the invention as defined in the appended claims. It will be appreciated that modifications or variations may be made. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

As described above, by applying the circuit according to the present invention to perform the correction process for the analog image signal, it is possible to easily process the appropriate correction process according to a simple circuit configuration. In addition, since the correction operation can be performed using only one A / D converter, the chip size can be miniaturized when the application-specific integrated circuit (ASIC) is used. In addition, when a circuit is constructed using a single product, the same circuit can be applied to various products as it develops a product having a different resolution of the A / D converter according to the model of the product, thereby reducing the cost. . In addition, since all correction operations can be performed by using one A / D converter, an error due to individual characteristics of a circuit element can be minimized, thereby obtaining an excellent output result.

Claims (6)

An A / D converter for converting a control signal input from a controller of an image input apparatus and an analog image signal detected and input by an image reading sensor of the image input apparatus into digital data; A D / A converter which generates a reference voltage when the A / D converter performs an A / D conversion operation and provides the A / D converter to the A / D converter; A latch storing digital data for the reference voltage and providing the digital data to an input of the D / A converter; A black correction memory for storing black correction data output by performing an A / D conversion operation in the A / D converter; A back correction memory configured to store back correction data output by performing an A / D conversion operation in the A / D converter; A maximum value detector for detecting a maximum pixel data value in the black correction memory; And And a selector for setting a reference voltage according to a control signal input from the controller and an operation mode of the A / D converter. The method of claim 1, wherein the control signal is Black correction value generation mode selection signal; A maximum value detection mode selection signal; A back correction value generation mode selection signal; And A preprocessor of an image input apparatus, characterized in that the original image reading mode selection signal. The method of claim 1, wherein the D / A converters A first D / A converter for generating an upper limit reference voltage while the A / D changer performs A / D conversion; And And a second D / A converter for generating a lower limit reference voltage while the A / D converter performs A / D conversion. The method of claim 1, wherein the selectors are A first selector for selecting an upper limit reference voltage provided to the A / D converter according to a control signal input from the controller and an operation mode of the A / D converter; And And a second selector for selecting a lower limit reference voltage provided to the A / D converter according to a control signal input from the controller and an operation mode of the A / D converter. Generating reference data for image distortion correction; Simultaneously performing black and white correction on an original image using the reference data; And And outputting the original image, which has been subjected to the black correction and the white correction, as digital image data. The method of claim 5, wherein the reference data generating step Generating black correction data for correcting a deviation caused by an individual difference according to an element characteristic of an image reading sensor mounted in the image input device; Detecting a maximum pixel data value from the black correction data; And And generating back correction data for removing the influence of the distortion of the light source and the white reference plate mounted in the image input apparatus.

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