Patent EP0809207A2 successfully refreshed from Google Patents.
EP0809207A2
Expired / Lapsed
EP
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Electrophotographic printer
Assignee: NEC Corp
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Filing: 1997-05-14
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Granted: —
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Expires: 2017-05-14
Abstract
Abstract An electrophotographic printer including feature extraction means 12 for judging on the basis of pattern matching whether a reference area generated by area generating means 11 is an image which should be subjected to smoothing processing, and detecting the gradient of a contour portion of the image when the image is judged to be subjected to the smoothing processing, resolution enhancing means 13 for subdividing each pixel in the reference area generated by the area generating means 11 into small areas in accordance with the extraction result of the feature extraction means 12 to thereby perform resolution enhancing correction processing, density calculation means 15 for calculating the density of the overall noted pixel on the basis of the respective pixel values of the noted pixel subdivided by the resolution enhancing means 13, center-of-gravity calculation means 16 for calculating the center of gravity of the overall noted pixel on the basis of the respective pixel values of the noted pixel subdivided by the resolution enhancing means 13, and characteristic correction means 17 for correcting the density and the center of gravity calculated by the density calculation means 15 and the center-of-gravity calculation means 16 in accordance with preset input/output characteristic information of the engine.
Inventors
- 👤 Koji Wada
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 10:47
CPC Classifications
G; G06; G06K; G06K15/00; G06K15/02; G06K15/12; G06K15/1204; G06K15/1223; G06K15/128; G06K2215/00; G06K2215/0002; G06K2215/004; G06K2215/006
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
383 words
An electrophotographic printer comprising: a controller for generating image data on the basis of print data received from a host computer; a smoothing circuit for outputting a video signal which is modulated to smooth edge portions in the image data generated by said controller; and an engine for recording the image data on a sheet in accordance with the video signal output from said smoothing circuit, wherein said smoothing circuit comprises: image input means through which the image data generated by said controller are input; area generating means for generating a reference area comprising a noted image located at the center position thereof and reference pixels surrounding the target pixel on the basis of the image data input to said image input means; feature extracting means for judging whether the reference area generated by said area generating means is an image which should be subjected to smoothing processing by a pattern matching, and detecting the gradient of a contour portion of the image if the reference area is judged to be an image to be subjected to the smoothing processing; and resolution-enhancing means for subdividing into small areas each pixel in the reference area generated by said area generating means in accordance with the extraction result of said feature extraction means and then performing resolution-enhancing correction processing, wherein said smoothing circuit further comprises: in juxtaposition with said resolution enhancing means, density calculation means for calculating the density of the overall noted pixel on the basis of respective pixel values of the noted pixel which is subdivided by said resolution enhancing means; center-of-gravity calculation means for calculating the center of gravity of the overall noted pixel on the basis of the respective pixel values of the noted pixel subdivided by resolution enhancing means; characteristic correction means for correcting the density calculated in said density calculation means and the center of gravity calculated in said center-of-gravity calculation means in accordance with preset input/output characteristic information of said engine; variation point calculating means for calculating the variation point of the video signal on the basis of the density and the center of gravity which are corrected by said characteristic correction means; and video output means for outputting the video signal in accordance with the variation point information which is obtained by said variation point calculation means.
Claim 2
Dependent Claim
109 words
The electrophotographic printer as claimed in claim 1, further including, in juxtaposition with said resolution enhancing means, area selection means for dividing the noted pixel subdivided by said resolution enhancing means in accordance with the resolution ratio of said controller and said engine, and selecting from the divided areas an area to be supplied to said density calculation means and said center-of-gravity calculation means, wherein each of said density calculation means and said enter-of-gravity calculation means has an individual selected area calculating function of calculating the density or the center of gravity on the basis of the respective pixel values of the area selected by said area selection means.
Claim 3
Dependent Claim
377 words
The electrophotographic printer as claimed in claim 1 or 2, wherein said video output means includes: first signal delay means for connecting in series at least one kind of delay elements whose number is equal to a to generate delay signals of a from one input signal, and selecting and outputting one of the delay signals of a ; second signal delay means for connecting in series said first signal delay means whose number is equal to m , and receiving a criterion signal having the frequency of n -times of a video signal transmission frequency f which is originally defined by said engine, thereby generating delay signals of m ; phase detection mens for detecting a phase shift from the criterion signal by using the most delayed delay signal of said second signal delay means as a reference signal; and condition determining means for determining an output selection condition of said second signal delay means on the basis of the detection result of said phase detection means, and in juxtaposition with said condition determining means, said video output means includes: signal generating means for generating n x m signals of frequency f which are delayed by 1/( n ̲ x m ̲ x f ̲ ) from the criterion signal and the m delay signals of said second signal delaying means; signal selection means for selecting from the nxm signals of said signal generating means a signal which is most synchronized with a horizontal synchronous signal output from said engine and setting the selected signal as a zero-phase signal, and setting as a s -phase signal a signal which is delayed from the zero-phase signal by s ̲ /( n ̲ x m ̲ x f ̲ ) ; third signal delay means for delaying the horizontal synchronous signal of said engine to avoid the horizontal synchronization during a selection condition transition period of said signal selection means; horizontal synchronizing means for receiving the horizontal synchronous signal delayed by said third signal delay means and performing the horizontal synchronization on the basis of the zero-phase signal selected by said signal selection means; and pulse generating means for generating a video signal specified by the variation point information which is output by said variation point calculating means.
Claim 4
Dependent Claim
288 words
The electrophotographic printer as claimed in claim 1, 2 or 3, wherein said controller comprises: a CPU for fetching a command stored in a code ROM for storing a program to control the operation of said engine, and executing the fetched command to thereby perform the overall management of said electrophotographic printer and the control required for a series of print operations; an engine interface control circuit for performing a handshake of a signal required for communications with said engine, said engine interface control circuit being interposed between said CPU and said engine, and receiving a status of said engine to issue a command to said engine; a host interface control circuit for performing a handshake of a signal required for communications with a host computer, said host interface control circuit being interposed between said CPU and said host computer, and receiving data from said host computer, said host interface control circuit receiving the data from said host computer every predetermined data unit, and said CPU analyzing the received data to generate two-dimensional bit map image signals on the basis of the analysis result; a RAM for storing the bit map image signals; a font ROM for outputting drawing information of a character when the received data contain the drawing data of the character concerned; and an image transmission control circuit for performing synchronization between an auxiliary scanning direction and a main scanning direction of said engine on the basis of a vertical synchronous signal from said engine interface control circuit and a horizontal synchronous signal from said smoothing circuit, and outputting the bit map image stored in said RAM as video signals to said smoothing circuit in accordance with a video clock signal of said smoothing circuit.
Claim 5
Dependent Claim
129 words
The printer as claimed in any one of claims 1 to 4, wherein said engine includes an electrophotographic process unit comprising a photosensitive drum serving as a central part of said electrophotographic printer, a main charger for charging said photosensitive drum with a fixed amount of charge, a laser scan unit for exposing said photosensitive drum to light, a developing roller for supplying and pressing toner, a transfer roller for feeding a toner-transfer sheet, a discharging probe for discharging the charge on the toner-transfer sheet, a cleaning unit for removing toner other than the transferred toner from said photosensitive drum, an erase unit for erasing the residual charge on said photosensitive drum, and a fixing unit for applying heat and pressure to the toner transferred onto the toner-transfer sheet.
Claim 6
Dependent Claim
64 words
The electrophotographic printer as claimed in claim 5, wherein an electrostatic latent image is formed on said photosensitive drum by light irradiation which is modulated in accordance with an image input signal of said laser scan unit, and said electrophotographic process unit further includes means for electrostatically attaching toner comprising colored charged fine particles to the electrostatic latent image to form a visible image.
Claim 7
Dependent Claim
60 words
The electrophotographic printer as claimed in claim 5 or 6, wherein in said electrophotographic process unit, attachment and non-attachment of the toner onto said photosensitive drum are clearly separated in accordance with a light exposure amount on said photosensitive drum by said laser scan unit on a threshold value representing the attachment or non-attachment of the toner as a border.
Claim 8
Dependent Claim
68 words
The printer as claimed in any one of claims 1 to 7, wherein said smoothing circuit includes concave detection means for detecting concave portions of the contour of the input signal, convex detection means for detecting convex portions of the contour of the input signal, and accumulation means for combining with and accumulating a detected signal of the concave portions and a detected signal of the convex portions.
Claim 9
Dependent Claim
43 words
The printer as claimed in any one of claims 1 to 8, wherein the gradient of the input image obtained by said feature extraction means is classified into six values of ±1, ±2, ±(1/2) as detection operators in accordance with the noted pixel.
Claim 10
Dependent Claim
35 words
The printer as claimed in any one of claims 1 to 9, wherein said density calculation means calculates the rate of the occupation area of black pixels to the whole area of the noted pixel.
Claim 11
Dependent Claim
114 words
The printer as claimed in any one of claims 1 to 10, wherein in order to calculate the center of gravity of black pixels in the main scanning direction in a selected area to which the smoothing processing is performed, said density calculation means sets the center axis of each column of the noted pixel as an action point, sets the weighting coefficients of a black pixel and a white pixel to 1 and 0 respectively, sets the left end axis and the right end axis of the selected area t 0 and 1 respectively, and sets the position in the auxiliary scanning direction from the left end axis to the center of gravity.
Claim 12
Dependent Claim
87 words
The printer as claimed in any one of claims 1 to 11, wherein said characteristic correction means corrects the density calculated by said density calculation means in accordance with the input/output characteristic of said engine which is defined by said controller, increases/reduces the pulse width corresponding to the input image to be supplied to said engine in accordance with the corrected density, and corrects the delay time of the pulse width in accordance with the position of the center of gravity calculated by said center-of-gravity calculation means.
Claim 13
Dependent Claim
57 words
The printer as claimed in any one of claims 2 to 12, wherein said smoothing circuit includes concave detection means for detecting concave portions of the contour of the input signal, convex detection means for detecting convex portions of the contour of the input signal, and accumulation means for accumulating the concave portions and the convex portions.
Claim 14
Dependent Claim
51 words
The printer as claimed in any one of claims 1 to 13, wherein said resolution enhancing means subdivides each pixel of a reference area into K rows x L columns which are determined on the basis of the gradient detected by said feature extraction means, and then smooths the contour position.
Claim 15
Dependent Claim
46 words
The printer as claimed in any one of claims 1 to 14, wherein said variation point calculation means calculates the final variation point of the video signal on the basis of the density and the center of gravity which are corrected by the characteristic correction means.
Claim 16
Dependent Claim
41 words
The printer as claimed in any one of claims 1 to 15, wherein said video output means outputs to said engine the video signal having the pulse width which meets the variation point information obtained by the variation point calculation means.
References Cited (Backward Citations)
No citation records indexed.
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