US6172718B1
Expired / Lapsed
US
⏱️ 0.0 years remaining
Adaptive dynamic aperture correction
Assignee: S3 Graphics Co Ltd
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Filing: 1998-04-17
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Granted: 2001-01-09
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Expires: 2018-04-17
Abstract
Abstract Aperture correction or edge detection circuitry filters input data for high-frequency components, and then selects areas most likely to be text based on the contrast of the signal and applying an amount of aperture correction responsive to the signal characteristics. A high pass filter ( 116 ) is employed to filter out low frequency components and separate the signal into positive and negative going transitions. Then, the positive-going signal is coupled to a contrast detector ( 124 ), which produces a control signal that controls the amount of aperture correction added to the signal by an aperture correction circuit 112 . The contrast detector ( 124 ) is designed to generate an amount of aperture correction that is responsive to the high frequency content of the positive-going signal. In one embodiment, a global threshold is used that allows aperture correction to be applied to the input signal only if the amplitude of the high frequency component of the signal is greater than the threshold. This prevents the unnecessary application of aperture correction for lower-contrast signals. In another embodiment, a second contrast detector ( 128 ) is employed to generate inverse aperture correction in response to the negative-going component of the input signal. This inverse aperture correction control signal is transmitted to the aperture correction and is employed in situations when the signal is transitioning from white to black. The present invention is applicable to the luminance or chrominance components of a graphics signal, and may be applied in conjunction with either horizontal or vertical picture detail with equal effectiveness.
Inventors
- 👤 Jos{acute over (e)} R. Alvarez
- 👤 William S. Herz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 18:03
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/14; H04N5/20; H04N5/205; H04N5/208
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
104 words
An apparatus for dynamically applying aperture correction coupled to an aperture correction circuit to enhance an input signal containing graphics data, comprising: a high pass filter, coupled to the input signal for passing only a high frequency component of the signal; and a contrast detector, coupled to the high pass filter and the aperture correction circuit, for producing a control signal controlling the amount of aperture correction to be added to a flicker filtered version of the input signal by the aperture correction circuit, in response to an amount of contrast present in the high frequency component of the signal transmitted by the filter.
Claim 2
Independent Claim
104 words
An apparatus for dynamically applying aperture correction coupled to an aperture correction circuit to enhance an input signal containing graphics data, comprising: a high pass filter, coupled to the input signal for passing only a high frequency component of the signal; and a contrast detector, coupled to the high pass filter and the aperture correction circuit, for producing a control signal controlling the amount of aperture correction to be added to a flicker filtered version of the input signal by the aperture correction circuit, in response to an amount of contrast present in the high frequency component of the signal transmitted by the filter.
Claim 3
Dependent Claim
65 words
The apparatus of claim 1 wherein the high pass filter divides the high frequency component of the signal into a signal containing positive going frequencies and a signal containing negative going frequencies; and the contrast detector is coupled to the signal containing positive going frequencies, and generates a control signal in response to the amount of contrast present in the signal containing positive going frequencies.
Claim 4
Dependent Claim
61 words
The apparatus of claim 1 , further comprising: a second contrast detector, coupled to the negative output of the high pass filter for detecting high contrast picture information in the signal and producing a control signal that determines an amount of inverse aperture correction that will be added by the aperture correction circuit to a flicker filtered version of the signal.
Claim 5
Dependent Claim
36 words
The apparatus of claim 1 , further comprising: a global threshold detector, coupled to the high pass filter, for enabling the aperture correction circuit in response to the amplitude of the input signal exceeding a threshold.
Claim 6
Dependent Claim
17 words
The output of claim 4 wherein the global threshold is set by a user of the system.
Claim 7
Dependent Claim
45 words
The apparatus of claim 1 , wherein a modified input signal is transmitted to the high pass filter comprising only the luminance characteristics of the signal, and wherein the contrast detector determines the amount of luminance to be added or subtracted to the input signal.
Claim 8
Dependent Claim
37 words
The apparatus of claim 6 , wherein the modified input signal comprises only the chrominance characteristics of the signal, and wherein the contrast detector determines the amount of chrominance to be added or subtracted to the signal.
Claim 9
Dependent Claim
40 words
The apparatus of claim 1 wherein there are a plurality of flicker filters coupled to the input signal in parallel with each other and the high pass filter, wherein one of the plurality is selected to perform the flicker filtering.
Claim 10
Dependent Claim
22 words
The apparatus of claim 1 wherein the high pass filter is a vertical high pass filter for processing only vertical picture detail.
Claim 11
Dependent Claim
16 words
The apparatus of claim 9 wherein the vertical high pass filter has characteristics of [½, −½].
Claim 12
Dependent Claim
83 words
The apparatus of claim 1 wherein the high pass filter further comprises: a line buffer, having an input coupled to the input signals for delaying the transmission of a line and an output; and a subtractor, having a first input coupled to the output of the line buffer and a second input coupled to the input signal, and having an output coupled to the contrast detector, for subtracting the output of the line buffer from the input signal to create a filtered signal.
Claim 13
Dependent Claim
17 words
The apparatus of claim 1 wherein the contrast detector is a circuit implementing a non-linear transfer function.
Claim 14
Dependent Claim
46 words
The apparatus of claim 1 wherein the signal received from the high pass filter has an amplitude, and the contrast detector comprises a memory for storing a table indexing output values for a non-linear transfer function generated in response to amplitudes ranging from 0 to 255.
Claim 15
Independent Claim
58 words
The apparatus claim of 12 wherein the control signal is generated in accordance with the function: Aperture Correction=Ydiff′/N+Offset; where Ydiff′ is the absolute value of the input signal, N is a constant chosen to control the rate at which aperture correction is applied, and the offset is chosen to set the minimum amount of aperture correction to apply.
Claim 16
Dependent Claim
13 words
The apparatus of claim 14 wherein the Offset and N values are selectable.
Claim 17
Dependent Claim
22 words
The apparatus of claim 12 , wherein the non-linear transfer function implemented by the circuit detects text information in the input signal.
Claim 18
Dependent Claim
197 words
The apparatus of claim 12 , wherein the circuit implementing the non-linear transfer function comprises: a divider, coupled to the high pass filter and a constant value, for dividing the output of the high pass filter by the constant value, where the constant determines a rate at which aperture correction is applied; an adder, coupled to the divider and an offset value, for adding the offset value to the output of the divider where the offset value sets the minimum amount of aperture correction that can be applied; a clipper, coupled to the adder, for clipping off negative components of the signal transmitted from the adder; a comparator, coupled to a threshold value and the clipper, for generating a control signal in response to the difference between the value of the signal transmitted by the clipper and the value of the threshold, where the threshold value is chosen as the maximum amount of aperture correction to apply; and a multiplexer, coupled to the threshold value, the output of the clipper, and the output of the comparator, for transmitting either the threshold or the output of the clipper in response to the control signal transmitted by the comparator.
Claim 19
Dependent Claim
43 words
The apparatus of claim 17 wherein the input signal is for display on a display in a computer system, and the offset value is selected by a user of the computer system to characterize the types of images generated in the computer system.
Claim 20
Dependent Claim
18 words
The apparatus of claim 1 , wherein the high pass filter is for processing only horizontal picture detail.
Claim 21
Dependent Claim
26 words
The apparatus of claim 1 , wherein the aperture correction circuit is located on the same device as the high pass filter and the contrast detector.
Claim 22
Dependent Claim
45 words
The apparatus of claim 1 further comprising: a multiplexer, coupled to a fixed aperture correction value and the output of the contrast detector, for transmitting either the fixed value of the contrast detector output in response to a selection signal to the aperture correction circuit.
Claim 23
Independent Claim
60 words
A method for dynamically adding aperture correction to a signal containing graphics data, comprising the steps of: filtering out the low frequency component of the signal; detecting areas of high picture detail in the filtered signal; and adding picture detail back to the detected areas of a flicker-filtered version of the signal responsive to the amount of picture detail detected.
Claim 24
Independent Claim
60 words
A method for dynamically adding aperture correction to a signal containing graphics data, comprising the steps of: filtering out the low frequency component of the signal; detecting areas of high picture detail in the filtered signal; and adding picture detail back to the detected areas of a flicker-filtered version of the signal responsive to the amount of picture detail detected.
Claim 25
Independent Claim
138 words
An apparatus for improving an image for display on a computer system comprising: a data source, for producing image data; a high pass filter, coupled to the data source, for filtering out low frequency components of the image data and creating a high-frequency image signal; a flicker filter, coupled to the data source, for removing flicker artifacts from the image data and creating a flicker-filtered version of the image data; a contrast detector, coupled to the high pass filter, for detecting contrast in the high frequency image signal and producing a value of aperture correction to be added to the image data; and an aperture correction circuit, coupled to the flicker filter and the contrast detector, for adding aperture correction to the flicker-filtered version of the image data in response to the value received from the contrast detector.
Claim 26
Independent Claim
138 words
An apparatus for improving an image for display on a computer system comprising: a data source, for producing image data; a high pass filter, coupled to the data source, for filtering out low frequency components of the image data and creating a high-frequency image signal; a flicker filter, coupled to the data source, for removing flicker artifacts from the image data and creating a flicker-filtered version of the image data; a contrast detector, coupled to the high pass filter, for detecting contrast in the high frequency image signal and producing a value of aperture correction to be added to the image data; and an aperture correction circuit, coupled to the flicker filter and the contrast detector, for adding aperture correction to the flicker-filtered version of the image data in response to the value received from the contrast detector.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-01-09 | 2004-07-10 | 2005-01-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-01-09 | 2008-07-10 | 2009-01-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-01-09 | 2012-07-10 | 2013-01-09 | $7700.00 | Window Closed / Lapsed |