US4555701A
Expired / Lapsed
US
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Legibility enhancement for alphanumeric displays
Assignee: International Business Machines Corp
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Filing: 1982-12-27
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Granted: 1985-11-26
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Expires: 2002-12-27
Abstract
Abstract Alphanumeric CRT display has normal/reverse video attribute. In reverse video, the character dots are made wider than in normal video, to equalize the apparent width of the dots in the two modes.
Inventors
- 👤 Richard E. Dahl
- 👤 Daniel P. Faflak
- 👤 Lee A. Sendelbach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:03
CPC Classifications
G; G09; G09G; G09G5/00; G09G5/22; G09G5/24; G09G5/28; G09G1/00; G09G1/002
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
138 words
In a display for alphanumeric character images made up of a matrix of individual dots having a character-generator means for producing a raw video signal having first and second levels, and having attribute means for producing an attribute signal specifying a normal mode in which said first level represents said image dots and specifying a reverse mode in which said second level represents said image dots, said images being substantially the same overall size in both said modes, the improvement comprising: timing means responsive to said raw video signal for producing a modified video signal having first and second dot durations different from each other; and switching means responsive to said attribute signal for selectively enabling said timing means to produce dots of said first and second durations for said normal mode and for said reverse mode respectively.
Claim 2
Dependent Claim
138 words
In a display for alphanumeric character images made up of a matrix of individual dots having a character-generator means for producing a raw video signal having first and second levels, and having attribute means for producing an attribute signal specifying a normal mode in which said first level represents said image dots and specifying a reverse mode in which said second level represents said image dots, said images being substantially the same overall size in both said modes, the improvement comprising: timing means responsive to said raw video signal for producing a modified video signal having first and second dot durations different from each other; and switching means responsive to said attribute signal for selectively enabling said timing means to produce dots of said first and second durations for said normal mode and for said reverse mode respectively.
Claim 3
Dependent Claim
31 words
A display according to claim 1, further comprising a display means responsive to said video signal for producing bright dots for said first level and dark dots for said second level.
Claim 4
Dependent Claim
14 words
A display according to claim 2, wherein said display means is a cathode-ray tube.
Claim 5
Dependent Claim
42 words
A display according to claim 3, wherein said timing means produces said first and second dot durations so as to substantially equalize the perceived lengths of said bright dots and said dark dots on said cathode-ray tube in each of said modes.
Claim 6
Dependent Claim
40 words
A display according to claim 2, wherein said timing means comprises first and second timing circuits for producing said first and second durations respectively, said durations being longer than said first and second levels respectively of said raw video signal.
Claim 7
Independent Claim
92 words
A method for enhancing the legibility of character images on a display means, comprising the steps of: generating each said image as a sequence of dots in a video wave having plural levels; decoding an attibute signal having a normal mode and a reverse mode specifying which of said levels represent said image and which of said levels represent a background of said image; imparting different first and second durations to those dots having levels representing said image, in response to whether said normal mode or said reverse mode has been decoded.
Claim 8
Independent Claim
92 words
A method for enhancing the legibility of character images on a display means, comprising the steps of: generating each said image as a sequence of dots in a video wave having plural levels; decoding an attibute signal having a normal mode and a reverse mode specifying which of said levels represent said image and which of said levels represent a background of said image; imparting different first and second durations to those dots having levels representing said image, in response to whether said normal mode or said reverse mode has been decoded.
Claim 9
Dependent Claim
41 words
A method according to claim 6, wherein said timing means produces said first and second dot durations so as to substantially equalize the apparent size of said bright dots in said normal mode and said dark dots in said reverse mode.
Claim 10
Dependent Claim
34 words
A method according to claim 7, wherein said timing means further produces said first and second dot durations so as to substantially equalize the apparent size of vertical and horizontal strokes in said image.
References Cited (Backward Citations)
US4028695A
Cited
US4298867A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-11-25 | 1989-05-27 | 1989-11-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-11-25 | 1993-05-27 | 1993-11-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-11-25 | 1997-05-27 | 1997-11-26 | $7700.00 | Window Closed / Lapsed |