Source: http://www.google.com/patents/US7483185?dq=6526440
Timestamp: 2017-05-26 11:23:52
Document Index: 422577923

Matched Legal Cases: ['arts 37', 'arts 37', 'arts 37', 'arts 37', 'arts 37', 'art 37', 'art 37', 'art 37', 'art 37', 'arts 37', 'arts 37', 'arts 37', 'arts 37']

Patent US7483185 - Method of calibrating image luminance values - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA method of calibrating image luminance values is provided. Firstly, scan N calibration charts to obtain N corresponding actual luminance values, where N is a positive integer larger than 2. Next, scan a document to obtain a scan luminance value. Then, provide N ideal luminance values corresponding to...http://www.google.com/patents/US7483185?utm_source=gb-gplus-sharePatent US7483185 - Method of calibrating image luminance valuesAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7483185 B2Publication typeGrantApplication numberUS 11/149,205Publication dateJan 27, 2009Filing dateJun 10, 2005Priority dateJun 11, 2004Fee statusLapsedAlso published asUS20050275903Publication number11149205, 149205, US 7483185 B2, US 7483185B2, US-B2-7483185, US7483185 B2, US7483185B2InventorsChih-Fang Huang, Hai-Jui LinOriginal AssigneeAvision Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (12), Non-Patent Citations (3), Classifications (12), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetMethod of calibrating image luminance values
US 7483185 B2Abstract
A method of calibrating image luminance values is provided. Firstly, scan N calibration charts to obtain N corresponding actual luminance values, where N is a positive integer larger than 2. Next, scan a document to obtain a scan luminance value. Then, provide N ideal luminance values corresponding to the N calibration charts. Lastly, determine a calibrated luminance value according to the N actual luminance values, the N ideal luminance values and the scan luminance value.
It is therefore an object of the invention to provide a method of calibrating image luminance values. The method of scanning several calibration charts of various color densities can enable a scanner to effectively calibrate the luminance values of an image signal outputted by each pixel, while avoiding image shading, which occurs when the conventional method is used, and largely improving scanning quality of the scanner.
FIG. 1 (Prior Art) illustrates a flowchart of a method of calibrating image luminance values for a conventional scanner;
Referring to FIG. 2, a flowchart of the method of calibrating image luminance values according to a first embodiment of the invention is shown. The present method is applied to a scanner 30 as shown in FIGS. 3A and 3B. In FIGS. 3A and 3B, the scanner 30 comprises a base 31, a cover 32, a platform 34, a chassis 35 and N calibration charts 37(1)˜37(N) of different color densities. N is a positive integer larger than 2. The cover 32, which is detachably connected to the base 31 through a hinge 33, can be closed and opened atop of the base 31 along the direction of an arrow 39 in FIG. 3A. The platform 34 is disposed on a top plate 31a of the base 31 for accommodating a document 36. The calibration charts 37(1)˜37(N), which are disposed on the inner wall of the top plate 31 a of the base 31, are positioned to one side of the platform 34 or positioned at any position according to prior art. The chassis 35 moves reciprocally inside the base 31 along the direction of an arrow 38 in FIG. 3A for scanning the calibration charts 37(1)˜37(N) and the document 36. Besides, the chassis 35 comprises a light source 35 a, a reflector 35 b, a lens 35 c and a photo-sensing module 35 d. The functions of the elements of the chassis 35 are disclosed below. Besides, the method can also be applied to scanners of other types.
Firstly, in step 21, the N calibration charts 37(1)˜37(N) are scanned to obtain N actual luminance values. N is a positive integer larger than 2. Besides, step 21 further comprises the following sub-steps. Firstly, N calibration charts 37(1)˜37(N) are scanned to obtain N induced voltages. Next, the N induced voltages are converted into N actual luminance values. As shown in FIGS. 3C and 3D, when the chassis 35 scan the calibration chart 37(1), firstly, the light source 35 a emits a light beam to the calibration chart 37(1). Next, the reflector 35 b guides the reflected light beam reflected by the calibration chart 37(1) to the lens 35 c. Then, the lens 35 c receives and focuses the light beam guided by the reflector 35 b to form an image on Q pixels P(1)˜P(Q) of the photo-sensing module 35 d. After that, each of the pixels P(1)˜P(Q) outputs an induced voltage to a control unit of the scanner 30. While the induced voltage can be an induced voltage among a red induced voltage, a green induced voltage and a blue induced voltage outputted by each of the pixels P(1)˜P(Q) when sensing a red light (R), a green light (G) and a blue light (B), the embodiment is exemplified by a red induced voltage. Then, the control unit of the scanner 30 converts the red induced voltage outputted by each of the pixels P(1)˜P(Q) into a corresponding actual luminance value. By the same token, the chassis 35 continues to scan the remaining N-1 calibration charts along the direction of the arrow 38 in FIG. 3C. When the chassis 35 has scanned the calibration chart 37(N), the scanner 35 will obtain N actual luminance values corresponding to each of the pixels P(1)˜P(Q). In other words, each pixel has N actual luminance values corresponding to various calibration charts.
Refer to FIG. 2, after the N actual luminance values are obtained, step 22 is proceeded. In step 22, chassis 35 scans the document 36 to obtain a scan luminance value. Besides, the step 22 can further comprise the following sub-steps. Firstly, the document 36 is scanned to obtain an induced voltage. Next, the induced voltage is converted into a scan luminance value. As shown in FIGS. 3E and 3F, when the chassis 35 scans the document 36, the chassis 35 scan the document 36 in units of scan lines. When the chassis 35 scans one of the scan lines of the document 36, firstly, the light source 35 a emits a light beam to the document 36. Next, the reflector 35 b guides the reflected light beam reflected by the document 36 to the lens 35 c. Then, the lens 35 c receives and focuses the light beam guided by the reflector 35 b to form an image on Q pixels P(1)˜P(Q) of the photo-sensing module 35 d. After that, each of the pixels P(1)˜P(Q) outputs an induced voltage to the control unit of the scanner 30. While the induced voltage can be an induced voltage among a red induced voltage, a green induced voltage and a blue induced voltage outputted by each of the pixels P(1)˜P(Q) when sensing a red light (R), a green light (G) and a blue light (B), the embodiment is exemplified by the red induced voltage. Then, the control unit of the scanner 30 converts the red induced voltage outputted by each of the pixels P(1)˜P(Q) into a corresponding scan luminance value. By the same token, the chassis 35 continues to scan the remaining scan lines of the document 36 which have not been scanned yet along the direction of the arrow 38 in FIG. 3E. When the chassis 35 has finished scanning the document 36, the scanner 35 will obtain a scan luminance value to which each of the pixels P(1)˜P(Q) corresponds at each scan line.
After the scan luminance value is obtained, step 23 is proceeded. In step 23, N ideal luminance values corresponding to the N calibration charts 37(1)˜37(N) are provided. The N ideal luminance values correspond to the N actual luminance values of the N calibration charts. Besides, a colorimeter measures luminance values of the N calibration charts 37(1)˜37(N) and obtains the N ideal luminance values arranged in an ascending order, i.e., the 1st to the Nth ideal luminance values. The (k+1)th ideal luminance value is larger than the kth ideal luminance value, where k ranges from 1 to N-1. Besides, the color densities of the N calibration charts 37(1)˜37(N) are distributed between 0 to 4. The N ideal luminance values can be N mono-color ideal luminance values of the N calibration charts 37(1)˜37(N). The embodiment is exemplified by the N red ideal luminance values.
Referring to FIG. 6, a flowchart of the method of calibrating image luminance values according to a second embodiment of the invention is shown. Firstly, in step 71, a first calibration chart, a second calibration chart and a third calibration chart are scanned to respectively obtain a first actual luminance value, a second actual luminance value and a third actual luminance value. The second actual luminance value ranges between the first actual luminance value and the third actual luminance value. Besides, the step 71 further comprises the following sub-steps. Firstly, the first calibration chart, the second calibration chart and the third calibration chart are scanned to respectively obtain a first induced voltage, a second induced voltage and a third induced voltage. Next, the first induced voltage, the second induced voltage and the third induced voltage are respectively converted into the first actual luminance value, the second actual luminance value and the third actual luminance value.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS5956469 *Jul 18, 1997Sep 21, 1999Eastman Kodak CompanySelecting a calibration function for a digital printer which minimizes an error criterionUS6075888 *Jan 11, 1996Jun 13, 2000Eastman Kodak CompanySystem for creating a device specific color profileUS6404517 *Mar 31, 1998Jun 11, 2002Seiko Epson CorporationColor-patch sheet registrationUS6750993 *Sep 11, 2000Jun 15, 2004Fuji Photo Film Co., Ltd.Density calibration chartUS6809844 *Nov 30, 1999Oct 26, 2004Avision Inc.Scanner which adjusts the image induced voltage by controlling the exposure time of the sensorsUS7164495 *Sep 15, 2000Jan 16, 2007Fuji Photo Film Co., Ltd.Method of converting image signal, method of determining original color of color image, and apparatus for converting image signalUS20020181032 *Dec 28, 2001Dec 5, 2002Nikon CorporationImage reading apparatus, program, and recording medium which can be read by computerUS20030193701 *Mar 18, 2003Oct 16, 2003Brother Kogyo Kabushiki KaishaImage forming apparatus and image capturing apparatusUS20040130739 *Dec 22, 2003Jul 8, 2004Adam George E.Scanner and printer profiling systemUS20050243339 *Apr 30, 2004Nov 3, 2005Mario KuhnMethods and apparatus for calibrating digital imaging devicesUS20060103900 *Nov 16, 2005May 18, 2006Chih-Fang HuangMethod of calibrating image luminance valuesEP0573069A1 *Jun 4, 1993Dec 8, 1993Fuji Photo Film Co., Ltd.Method and apparatus for calibrating a colour scanner* Cited by examinerNon-Patent CitationsReference1 *L.M.Soh, J. Matas, J. Kittler, Robust Recognition of Calibration Charts, 1997, IEEE, pp. 487-491.2 *S. Kang, H. Do, B. Cho, S. Chien, H. Tae, Improvement of Low Gray-Level Linearity Using Perceived Luminance of Human Visual System in PDP-TV, 2005, IEEE, pp. 365-366.3 *Y. Xiaohan, C. Sodergard, J. Yla-Jaaski, On-line Control of the Colour Printing Quality by Image Processing, 1993, IEEE, vol. 2, pp. 1039-1041.* Cited by examinerClassifications U.S. Classification358/504, 358/520, 358/406, 358/474, 358/461International ClassificationH04N1/40, H04N1/04, H04N1/60, H04N1/401, H04N1/46Cooperative ClassificationH04N1/401European ClassificationH04N1/401Legal EventsDateCodeEventDescriptionJun 10, 2005ASAssignmentOwner name: AVISION INC., TAIWANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HUANG, CHIH-FANG;LIN, HAI-JUI;REEL/FRAME:016684/0436Effective date: 20050517Sep 10, 2012REMIMaintenance fee reminder mailedJan 27, 2013LAPSLapse for failure to pay maintenance feesMar 19, 2013FPExpired due to failure to pay maintenance feeEffective date: 20130127RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services