Source: http://www.google.com/patents/US7133154?ie=ISO-8859-1
Timestamp: 2015-03-04 09:29:21
Document Index: 55287529

Matched Legal Cases: ['art 582', 'art 700', 'art 700', 'art 600', 'art 700', 'art 700']

Patent US7133154 - Image forming apparatus and masking coefficient calculation method - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn image forming apparatus for calculating a masking coefficient is provides, in which the masking coefficient is calculated by using RGB input image signals obtained by reading a document of which spectral characteristics are known by an image reading part and CMYK output image signals optimal for reproducing...http://www.google.com/patents/US7133154?utm_source=gb-gplus-sharePatent US7133154 - Image forming apparatus and masking coefficient calculation methodAdvanced Patent SearchPublication numberUS7133154 B2Publication typeGrantApplication numberUS 10/103,758Publication dateNov 7, 2006Filing dateMar 25, 2002Priority dateMar 28, 2001Fee statusPaidAlso published asUS20030002096Publication number10103758, 103758, US 7133154 B2, US 7133154B2, US-B2-7133154, US7133154 B2, US7133154B2InventorsNaoki SugiyamaOriginal AssigneeRicoh Company, Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (16), Referenced by (12), Classifications (10), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetImage forming apparatus and masking coefficient calculation method
US 7133154 B2Abstract
Although this invention mainly relates to correction or calculation of a masking coefficient for color calibration process performed in an after-mentioned color calibration circuit, a configuration and the operation of the copying machine will be described first with reference to FIGS. 2�4, and the color calibration process will be described in detail after that.
In addition, the photoelectric sensor control part has a function for computing an exposure lamp voltage corresponding to it and a function for detecting residual voltage of a photosensitizer and comparing the residual voltage with a reference value, and computing a development bias voltage value corresponding to it. The exposure lamp voltage value and the development bias voltage value detected in this photoelectric sensor control part are applied to an exposure control circuit which controls driving power source voltage of the exposing lamp 119 and a development bias control circuit which applies a voltage to developing devices 105�108 by using development bias.
Non-magnetic cylindrical development sleeves 201B, 201Y, 201M, 201C which are developer containers are provided in the inside of the developing devices 105�108 with a predetermined gap to the photosensitive drum 102 (only 201M is shown in FIG. 3), wherein the gap between the sleeve and the photosensitive drum 102 is 0.60 mm. In each of the development sleeves 201B, 201Y, 201M, 201C, a development magnet formed such that a plurality of different magnetic poles are alternately arranged and a magnetic shield plate formed of a magnetic substance are provided.
When developing, each of the development sleeves 201B, 201Y, 201M, 201C rotates in the direction of the arrow by a yellow development sleeve driving motor, a magenta development sleeve driving motor, a cyan development sleeve driving motor and the like. A case where the development sleeve rotates in this direction is called �forward rotation�.
( a cr a cg a cb a c a mr a mg a mb a m a yr a yg a yb a y a kr a kg a kb a k ) = ( C1 C2 C3 C4 M1 M2 M3 M4 Y1 Y2 Y3 Y4 K1 K2 K3 K4 ) � ( R1 R2 R3 R4 G1 G2 G3 G4 B1 B2 B3 B4 1 1 1 1 ) - 1 ( 2 ) Here, the recording values of C, M, Y and K for each point are equivalent achromatic color density conversion values before performing UCR (under color removing). For the sake of simplicity, two points on the achromatic color axis are a white point and a black point in the following description. In this case, when it is assumed that the maximum value which the equivalent achromatic color density conversion value can take is Xmax, there are following relationships between each value.
When UCR rate is 100%: K=Min(C,M,Y) When UCR rate is 70%: K=Min(C,M,Y)�0.7
( C3 ′ M3 ′ Y3 ′ K3 ′ ) = ( a cr a cg a cb a c a mr a mg a mb a m a yr a yg a yb a y a kr a kg a kb a k ) � ( R3 ′ G3 ′ B3 ′ 1 ) ( 3 ) However, the recording values of the developing parts C, M, Y and K optimal for reproducing the color (R3,G3,B3) should be (C3,M3,Y3,K3). Thus, the difference values shown in the equation (4) become a cause for preventing faithful color reproduction.
( C M Y K ) = ( C1 + C D C2 + C D C3 + C D C4 + C D M1 + M D M2 + M D M3 + M D M4 + M D Y1 + Y D Y2 + Y D Y3 + Y D Y4 + Y D K1 + K D K2 + K D K3 ′ + K D K4 + K D ) � ( R1 R2 R3 R4 G1 G2 G3 G4 B1 B2 B3 B4 1 1 1 1 ) - 1 � ( R3 ′ G3 ′ B3 ′ 1 ) ( 5 ) Assuming ( R ″ G ″ B ″ T ) = ( R1 R2 R3 R4 G1 G2 G3 G4 B1 B2 B3 B4 1 1 1 1 ) - 1 � ( R3 ′ G3 ′ B3 ′ 1 ) , the ( 6 ) the following equation (7) holds true.
( R1 R2 R3 R4 G1 G2 G3 G4 B1 B2 B3 B4 1 1 1 1 ) ( R ″ G ″ B ″ T ) = ( R3 ′ G3 ′ B3 ′ 1 ) ( 7 ) Therefore, R″+G″+B″+T=1 is obtained by comparing fourth row in the vectors. By substituting the equation (6) into the equation (5), a following equation (8) is obtained.
( C M Y K ) = ( C1 + C D C2 + C D C3 + C D C4 + C D M1 + M D M2 + M D M3 + M D M4 + M D Y1 + Y D Y2 + Y D Y3 + Y D Y4 + Y D K1 + K D K2 + K D K3 ′ + K D K4 + K D ) � ( R ″ G ″ B ″ T ) = ( ( C1R ″ + C2G ″ + C3B ″ + C4T ) + C D ( R ″ + G ″ + B ″ + T ) ⋯ ⋯ ⋯ ) ( 8 ) The first term in the first element in the vector is the same as C3′ of the equation (3) according to the definition of the equations (1), (2) and (6). Since R″+G″+B″+T=1, the equation (8) becomes
= ( C3 ′ + D D M3 ′ + M D Y3 ′ + Y D K3 ′ + K D ) by equation ( 4 ) = ( C3 M3 Y3 K3 ) . ( 9 ) That is, the values (C3,M3,Y3,K3) which should be obtained can be obtained by using the difference values of the equation (4).
( C 1 + C D C 2 + C D C 3 + C D C 4 + C D M 1 + M D M 2 + M D M 3 + M D M 4 + M D Y 1 + Y D Y 2 + Y D Y 3 + Y D Y 4 + Y D K 1 + K D K 2 + K D K 3 + K D K 4 + K D ) � ( R1 R2 R3 R4 G1 G2 G3 G4 B1 B2 B3 B4 1 1 1 1 ) - 1 ( 10 ) Accordingly, the variation of the spectral characteristics is calibrated and faithful color reproduction can be realized.
Normally, the processes of steps 1�5 and calculation of masking coefficients are performed in a manufacturing process. However, a serviceman or a user, for example, can calculate the difference values and the masking coefficient, so that calibration of CCD for variation over time can be performed. In addition, by providing a color patch in the copying machine, operability at the time of calibration can be improved.
( a cr a cg a cb a c a mr a mg a mb a m a yr a yg a yb a y a kr a kg a kb a k ) = ( C [ W ] C [ K ] C [ M ] + C D [ M ] C [ R ] + C D [ R ] M [ W ] M [ K ] M [ M ] + M D [ M ] M [ R ] + M D [ R ] Y [ W ] Y [ K ] Y [ M ] + Y D [ M ] Y [ R ] + Y D [ R ] K [ W ] K [ K ] K [ M ] + K D [ M ] K [ R ] + K D [ R ] ) � ( R [ W ] R [ K ] R [ M ] R [ R ] G [ W ] G [ K ] G [ M ] G [ R ] B [ W ] B [ K ] B [ M ] B [ R ] 1 1 1 1 ) - 1 ( 12 ) In an actual image forming process, calculation of the equation (1) is performed on image information read by the scanner by using the color calibration processing circuit 406 by using the masking coefficient calculated by using the equation (12), so that the variation of spectral characteristics of the scanner CCD is calibrated, and continuous and faithful color reproduction can be performed.
( C ′ [ R ] M ′ [ R ] Y ′ [ R ] K ′ [ R ] ) = ( C [ R ] C [ Y ] C [ W ] C [ K ] M [ R ] M [ Y ] M [ W ] M [ K ] Y [ R ] Y [ Y ] Y [ W ] Y [ K ] K [ R ] K [ Y ] K [ W ] K [ K ] ) � ( R [ R ] R [ Y ] R [ W ] R [ K ] G [ R ] G [ Y ] G [ W ] G [ K ] B [ R ] B [ Y ] B [ W ] B [ K ] 1 1 1 1 ) - 1 � ( R ′ [ R ] G ′ [ R ] B ′ [ R ] 1 ) ( 14 ) Therefore, (C[R],M[R],Y[R],K[R]) optimal for color reproducing of the R patch can not be obtained.
( C [ R ] M [ R ] Y [ R ] K [ R ] ) = ( C [ R ] C [ Y ] C [ W ] C [ K ] M [ R ] M [ Y ] M [ W ] M [ K ] Y [ R ] Y [ Y ] Y [ W ] Y [ K ] K [ R ] K [ Y ] K [ W ] K [ K ] ) � ( R ′ [ R ] R ′ [ Y ] R [ W ] R [ K ] G ′ [ R ] G ′ [ Y ] G [ W ] G [ K ] B ′ [ R ] B ′ [ Y ] B [ W ] B [ K ] 1 1 1 1 ) - 1 � ( R ′ [ R ] G ′ [ R ] B ′ [ R ] 1 ) ( 15 ) holds true, so that (C[R],M[R],Y[R],K[R]) optimal for reproducing colors of the R patch of FIG. 7 can be obtained. Accordingly, the masking coefficient is calculated by using scanner reading values (scanner vectors) of the divided points by which the hue is divided and recording values (printer vectors) of the developing parts C, M, Y and K optimal for reproducing color of the divided points. Then, faithful color reproduction can be performed by calibrating variation of spectral characteristics of the scanner CCD by using the masking coefficient.
Each single color image formed on the photosensitive belt 501 which rotates in the direction of the arrow A in the figure is transferred and overlaid successively to the intermediate transfer belt 510 which rotates in the direction of the arrow B for each single color of yellow, cyan, magenta and black. The images of yellow, cyan, magenta and black overlaid on the intermediate transfer belt 510 are transferred on the transfer paper 517 a conveyed to the transferring part via the feeding roller 518, pair of carrying rollers 519 a and 519 b and pair of resist rollers 520 a and 520 b from the sheet feeder 517. After the transfer ends, the transfer paper 517 a is fixed by a fixing device 580, so that the full-color image is completed, and the print image is ejected to the ejection stack part 582 via the pair of ejection rollers 581 a and 581 b. The color calibration process of the present invention is performed in the laser writing system unit 505 which resolves the desired full-color image into color information of yellow, cyan, magenta and black and performs exposure or in the control apparatus (not shown in the figure). That is, input image information is converted by the masking coefficient and exposure is performed on the basis of color information of yellow, cyan, magenta and black obtained by the conversion.
The control apparatus may be provided in the inside of the printer or the outside of the printer. When providing the control apparatus (color calibration part) in the outside, the configuration can be as shown in FIG. 10 for example. In FIG. 10, the image input part 700 is a scanner and the like. However, any apparatus (camera for example) can be used as long as the apparatus outputs an image as R, G, B data. In addition, the image input part 700 may be an apparatus which does not receive an image, instead, stores image data obtained by other apparatus and the like. The color calibrating part 600 performs the process for calculating CMYK necessary for color reproduction by using the masking coefficient described on the embodiments 1�3, the UCR process and other necessary processes. The correction of the masking coefficient can be performed by reading reference colors (color patch and the like) from the image input part 700. Accordingly, variation and time change for each device of the image input part 700 can be calibrated.
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