TW569613B - Method for generating calibration curve - Google Patents

Abstract

A method for generating a calibration curve is disclosed. The method comprises the following steps. Calibration data of one image line of previous scan are firstly provided. Reference pixels are selected from the image line. Then a calibration board is scanned and calibration data of the reference pixels are generated. Calibration data of the reference pixels of previous scan are then selected from the calibration data of one image line of previous scan.

Description

569613 V. Description of the invention (1) 5-1 Field of the invention: The present invention relates to a method for generating a calibration curve, especially a method for generating a calibration curve by using reference points of image lines instead of all points. 5-2 Background of the Invention:

Optical scanners are used to capture and digitize images. For example, optical scanners are most commonly used to capture text or other images printed or printed on flat paper. The captured image is then digitized and stored or further processed by character recognition software to generate the text of the American Standard Code for Information Interchange A SC I I. A typical optical scanner includes a light source, a linearly arranged photo-sensing element (usually a charge-coupled element CCD, complementary metal-oxide-semiconductor transistor CMOS and CIS), and an analog amplifier (A na 1 〇g A mp 1 (ifier), an analog-to-digital converter, a control unit (C ο ntr ο 1 1 er), and a memory element.

The photo-sensing element contains a large number of linearly-coupled charge-coupled elements (CCDs). Each charge-coupled element CCD can capture the optical signal of a single pixel of the image. An entire row of charge-coupled device CCDs can capture the optical signals of an entire row of pixels in the image. By scanning across the entire document, the CCD can receive the image light signal of the entire document. Light signals reflecting self-scanning documents or penetrating self-scanning documents are converted into digital

Page 5 569613 V. Description of the Invention (2) The process of a bit signal consists of three steps. First, each photo-sensing element converts the received light signal into a charge, and the amount of charge depends on the intensity of the light and the exposure time. Secondly, the charge generated by the photo-sensing element is converted into an analog voltage by an analog amplifier. Finally, the analog voltage is digitized by the analog-to-digital converter for digital image processing and storage in the memory device. In conventional image scanners, image compensation corrections are required before each scan. This is because the status of the image scanner's components changes each time it is scanned. For example, the brightness of a cold-cathode tube (C ο 1 d C a t h 〇 d e F 1 uor e s c e n t Lamp) often changes with the duration of the turn on, the ambient temperature and the location. In addition, each element of a linear image sensing element such as a charge-coupled element CCD is not completely the same, and the response to the same optical signal is also different. Traditionally, a white calibration plate or a black calibration plate is used to generate a calibration curve. By scanning the white or black calibration plate, a calibration curve showing the relationship between all pixels of an image line and the brightness can be obtained. The data of this calibration curve is then used to calculate to generate the correction compensation data corresponding to each charge-coupled element CCD. However, the above image compensation correction method has many disadvantages. For example, a linear image sensing element array generally includes many image sensing elements. One image line includes three primary colors of red, green, and blue. Each color may have 10,0 0 0 image sensing elements. If after scanning the calibration plate, 3 or 2 image lines are selected to generate the calibration curve, there will be 10, 0 0 0 (pixels) X 3 (the three primary colors of red, green and blue) X 3 2 (image lines) = 9 Data of 6 0, 0 0 pixels need to be processed. Each pixel contains 1 to 2

569613 V. Description of the invention (3) Byte data represents 0 to 2 5 5 brightness values. Obviously processing such a large amount of data will slow down the speed and performance of the image scanner. Some traditional image scanners do not perform calibration before each scan. Instead, the previous calibration curve is used. This may cause the image brightness of the scanned image to be changed due to the changes in the components of the image scanner as the duration of opening, ambient temperature, and position Uneven and poor quality. Therefore, it is very necessary to propose a novel method for generating a calibration curve to overcome the shortcomings of the conventional image scanner, and the present invention can meet this demand. 5-3 Objects and Summary of the Invention: An object of the present invention is to provide a method for generating a calibration curve that requires minimal processing of data. Another object of the present invention is to provide a method for generating a calibration curve with high efficiency. In order to achieve the above object, the present invention provides a method for generating a calibration curve. The method for generating a calibration curve includes the following steps. First provide the calibration compensation data for the previous scan of an image line. Then select a plurality of reference point pixels in an image line. Then scan the calibration plate and generate calibration compensation data for the reference point pixels. Select parameters from the calibration compensation data of the previous scan

569613 V. Description of the invention (4) Examine the correction compensation data of the pixel at the point, and calculate the ratio between the correction compensation data of the reference point pixel and the correction compensation data of the reference point pixel of the previous scan. Multiplying the correction compensation data of all pixels of an image line by the previous scan can obtain the correction compensation data of all pixels of an image line. The foregoing brief description of the invention and the following detailed description are examples only and are not limiting. Other equivalent changes or modifications that do not depart from the spirit of the invention should be included in the patent scope of the invention. 5-4 Detailed description of the invention: It must be explained here that the method of generating a calibration curve described below contains only the necessary components and steps. At the same time, the present invention can be implemented by various conventional software and hardware. Only the system and operation mode required for understanding the present invention are mentioned here. The following detailed description will be made according to the accompanying drawings of the present invention. Please note that the drawings are simple forms. Referring to the first figure, the calibration curve of the relationship between all pixels and brightness of an image line is displayed. Before formally scanning, a calibration curve showing the relationship between all pixels and brightness of an image line can be obtained by scanning a white calibration plate. The data of this calibration curve is then used to calculate to generate the correction compensation data corresponding to each CCD. The calibration curve used to correct the image is generally obtained by scanning a calibration plate, taking the data of multiple image lines and averaging the data of these image lines. Referring to the second figure, the display

Page 8 569613 V. Description of the invention (5) A functional block diagram of an image scanner according to a preferred embodiment of the present invention. The light beam reflected from the surface of the calibration plate exposes the charge-coupled element 202, and the optical signal is converted into an analog voltage signal by the charge-coupled element 202. The analog voltage signal is then adjusted by a DC gain amplifier 204, and then the analog voltage signal is digitized by an analog digital converter 206 into a digital voltage signal. The digital voltage signal is then calculated by a correction device 208 to generate correction compensation data corresponding to each CCD. The correction compensation data is then stored in the memory 210. The third figure shows a flowchart of a preferred embodiment of the present invention. Before executing the method for generating a calibration curve of the present invention, the calibration curve and calibration compensation data corresponding to the previous scan of each charge-coupled element CCD must be established and stored in the memory. By scanning the white calibration plate, a calibration curve showing the relationship between all pixels of an image line and the brightness can be obtained. The data of this correction curve is then used to calculate to generate the correction compensation data D0 corresponding to each charge-coupled element CCD. The correction compensation data D0 is then stored in the memory 2 1 0. Before the next scan, since each time the scan is performed, the component status of the image scanner will change, a new calibration curve corresponding to the current state needs to be generated before each scan to perform image compensation correction. The method for generating a calibration curve of the present invention first selects a plurality of reference point pixels instead of all pixels from an image line in step 302. Then, in step 304, by scanning the correction plate, the correction compensation data DR 1 of the reference point pixels can be obtained through the image scanner function block diagram processing flow shown in the second figure. Then in step 3 06, the calibration device 2 0 8 is stored in the memory 2 1 0

569613 V. Description of the invention (6) In the correction compensation data DO, the correction compensation data DRO of the reference pixel is selected. Then in step 308, the correction device 208 calculates a ratio DR1 / DR0 of the correction compensation data DR1 and the correction compensation data DR0. In step 310, the correction device 208 multiplies the correction compensation data D 0 of all pixels of an image line by DR1 / DR0 to obtain the correction compensation data D b corresponding to each charge-coupled element CCD in this scan. In step 31 2, the correction compensation data D 1 is then stored in the memory 2 1 0. For linear image sensing elements,

The value of DR1 / DR0 is a constant. A new calibration curve can be obtained by selecting 32 (for example) image lines and averaging the correction compensation data D 1 for each image line. When a document or image is scanned formally, the light beam reflected from the document or image surface exposes the charge coupling element 202, and the light signal is converted into an analog voltage signal by the charge coupling element 202. The analog voltage signal is then adjusted by a DC gain amplifier 204, and then the analog voltage signal is digitized and converted into a digital voltage signal by the analog digital converter 206. The digital voltage signal is then transmitted to the calibration device 208. At the same time, the calibration device 208 also accesses the correction compensation data D1 from the memory 2 10. The digital voltage signal is combined with the correction compensation data D1 to calculate and generate an image signal for processing. For further image processing or display. The fourth figure shows the original calibration curve 4 0 2 and a new calibration curve 4 0 4 generated by the method of generating a calibration curve of the present invention.

In another preferred embodiment of the present invention, step 308 is changed to calculate the reciprocal DRO / DR1 of the ratio between the correction compensation data DR1 and the correction compensation data DR0 by the correction device 208, and step 3 0 can be omitted. DRO / DR1 can be backfilled to the DC gain amplifier 204 by the correction device 208. When the scan is officially launched

Page 10 569613 V. Description of the invention (7) " 'In the case of a document or an image, #the light beam reflected from the surface of the document or the image is exposed to the charge-coupled το member 2 0 2' and the optical signal is transmitted by the charge-coupled element 2 02 Into analog voltage signals. The analog voltage signal is then passed through a DC gain amplifier 204. Zhou Zheng then corresponding to the analog voltage signal of each charge-synthesizing element CCD is multiplied by the DC gain amplifier 204 by DR0 / DR1. The analog voltage signal is then digitized by the analog-to-digital converter 206 into a digital voltage signal. The digital voltage signal is then passed to the calibration device 208. The calibration device 208 uses the digital voltage signal to generate an image signal for further image processing or display. In addition, when the image sensing element is non-linear, the reference point can be selected to calculate the value of DR1 / DR0 at each point according to the method described above, and then the DR1 / DR of the other points obtained can be obtained by interpolation / (Interpolation Method) . From the side; when the image sensing is non-linear, the above DR1 / DR0 is not necessarily. Therefore, multiple reference points must be selected to calculate the DIU / DR0 values for each test, and then calculated by interpolation. Show the DRi / DRO value of the two adjacent reference points. As shown in the fifth picture, according to the third picture, take the test points & Bu 32 and ⑹, and scan the calibration plate to generate the reference, a, a2, and a3 correction compensation data ^, DR1 — ^ And 夂 the second child 3. Then, the original calibration curve 5 0 2 obtained from the W scans corresponds to DPn— \ pixels ^ 1, a2 and a3 correction compensation data DR0-al, DR0-a2, and letter,! 5 Tea test point pixels a 1 and a3 of DR 1 / DR0 rod burdock ^ 用 1 within each of the Mac test point pixels a: 1, a2, and 83 within the DR1 / DR0 value 圹 1 is different from the other pixels a4 and a5 DR1 / DR0 Value, so that a new normal curve 504 is obtained.

Page 11 569613 V. Description of the invention (8) The above detailed description of the invention is merely an example and not a limitation. Other equivalent changes or modifications that do not depart from the spirit of the invention should be included in the patent scope of the invention.

Page 569613 Brief description of the drawings In order to make the other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings to make a detailed description as follows: One image shows the correction curve of the relationship between all pixels of an image line and brightness; the second image shows a functional block diagram of an image scanner according to a preferred embodiment of the present invention; the third image shows a flowchart of one preferred embodiment of the present invention The fourth graph shows the original calibration curve and a new calibration curve generated by the method of the present invention, and the fifth graph shows the original calibration curve and a new calibration curve generated by the method of the present invention. Representative symbols of the main parts: 2 0 2 charge-coupled devices 2 0 4 DC gain amplifier 2 0 6 analog-to-digital converter 2 0 8 calibration device 2 1 0 memory

Page 13 569613 Brief description of the diagram 3 0 2 Select a plurality of reference point pixels in an image line 3 0 4 Scan the calibration plate and generate correction compensation data for reference point pixels DR 1 3 0 6 Select correction compensation data for reference point pixels DR 0 3 0 8 Calculate the ratio DR1 / DR0 of the correction compensation data DR 1 and the correction compensation data DRO 3 1 0 Multiply the correction compensation data DO of all pixels of an image line by DR1 / DR0 to obtain corresponding to each charge-coupled element CCD calibration compensation data D1 3 1 2 Store calibration compensation data D 1 to memory

4 0 2 Original calibration curve 4 0 4 New calibration curve 5 0 2 Original calibration curve 5 0 4 New calibration curve

Page 14

Claims (1)

569613 6. Scope of patent application 1. A method for generating a calibration curve, the method for generating a calibration curve includes providing correction compensation data of a previous scan of an image line; selecting a plurality of reference point pixels in the image line; Calibration plate; Generate the correction compensation data of the reference point pixels; Select the correction compensation data of the reference point pixels from the correction compensation data of the previous scan to calculate the correction compensation data of the reference point pixels and the reference point pixels of the previous scan The ratio of correction compensation data; using the ratio of pixels at the reference point is worth the correction compensation data for all pixels of the image line to generate a correction curve. 2. The method for generating a calibration curve as described in item 1 of the scope of patent application, wherein the above-mentioned correction plate includes a white correction plate. 3. The method for generating a calibration curve as described in item 1 of the scope of patent application, wherein the above-mentioned correction plate includes a black correction plate. 4. The method for generating a calibration curve as described in item 1 of the scope of the patent application, wherein the above-mentioned reference point pixel compensation data is converted to an analog voltage signal by converting the optical signal reflected from the calibration plate to adjust the analog voltage Signal, converting the analog voltage signal into a digital voltage signal and correcting and compensating the digital voltage signal. Page 15 569613 6. Application for patent scope 5. The method for generating a calibration curve as described in item 1 of the scope of patent application, wherein the above-mentioned calibration curve is the compensation data of the previous scan of all pixels of the image line They are all multiplied by the ratio of pixels at the reference point. 6. According to the method for generating a calibration curve described in item 1 of the scope of the patent application, when the ratio of the reference point pixels is not a certain value, the correction curve is obtained by interpolation from the ratio of the reference point pixels. 7. —A method for generating a calibration curve, the method for generating a calibration curve includes: providing correction compensation data of a previous scan of an image line; selecting a plurality of reference point pixels in the image line; hiding a calibration plate; generating The correction compensation data of the reference point pixel; The correction compensation data of the reference point pixel is selected from the correction compensation data of the previous scan; The correction compensation data of the reference point pixel of the previous scan and the correction compensation data of the reference point pixel are calculated. Ratio; backfill the ratio to a gain voltage amplifier; and correct the analog voltage signal of all pixels of the image line by correcting the ratio in the gain voltage amplifier. 8. The method for generating a calibration curve as described in item 7 of the scope of patent application, which Page 16 569613 6. The scope of the patent application mentioned above includes a white calibration plate. 9. The method for generating a calibration curve according to item 7 of the scope of the patent application, wherein the above-mentioned correction plate includes a black correction plate. 10. The method for generating a calibration curve as described in item 7 of the scope of patent application, wherein the above-mentioned reference point pixel compensation data is converted to an analog voltage signal by converting the light signal reflected from the calibration plate to adjust the analog signal Voltage signal, converting the analog voltage signal into a digital voltage signal, and correcting and compensating the digital voltage signal. 1 1. A device for generating a calibration curve, the device for generating a calibration curve includes: a charge handle element, the charge light-closing element receives an optical signal and converts the optical signal into an analog voltage signal; a DC gain amplifier, the DC The gain amplifier receives and adjusts the analog voltage signal; an analog-to-digital converter, which receives and converts the analog voltage signal into a digital voltage signal; A correction device receives and corrects the digital voltage signal. The correction device selects a plurality of reference point pixels from the memory, calculates correction compensation data of the reference point pixels, and a reference point of a previous scan. Multiply the ratio of the pixel's correction compensation data, store the ratio in the memory, and the correction compensation data of the previous scan of all pixels of the image line. Page 17 569613 6. Scope of patent application Use this ratio to get the correction compensation data of all pixels; a memory that stores the corrected and compensated digital voltage signal from the correction device. 1 2. A device for generating a calibration curve, the device for generating a calibration curve includes: a charge-coupled element that receives an optical signal and converts the optical signal into an analog voltage signal; a DC gain amplifier, the DC gain The amplifier receives and adjusts the analog voltage signal; An analog digital converter that receives and converts the analog voltage signal into a digital voltage signal; a correction device that receives and corrects the digital voltage signal and that the correction device selects a complex number from the memory For each reference point pixel, calculating the ratio of the correction compensation data of the reference point pixel from the previous scan to the correction compensation data of the reference point pixel, and backfilling the ratio to the gain voltage amplifier; a memory, the memory storing the The corrected digital voltage signal of the correction device. Page 18