EP0241284A2
Expired / Lapsed
EP
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Television display system
Assignee: RCA Licensing Corp
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Filing: 1987-04-09
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Granted: —
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Expires: 2007-04-09
Abstract
Abstract The field rate of a video input signal is doubled by storing each field in a memory (40, 202, 204) and recovering each stored field twice so as to repeat each field and thus reduce flicker. To ensure that even fields overlay even fields, odd fields overlay odd fields and that all pairs of even and odd fields are interlaced, a timing unit (70) provides a double field rate read control signal (2V) to the memory having a waveform that repeats ona two-field basis and supplies a double field rate vertical synchronizing signal (2Vʹ) to a display (60) having a waveform that repeats on a four-field basis. Thus not all fields are of the same number of lines, and appropriate patterns of control signal (2V) field rate and vertical synchronising signal (2Vʹ) field rate ensure correct overlay and interlace. Registration of images is enhanced further by means of a vertical scan generator having a constant retrace time, a fixed retrace level and employing DC coupling thereby avoiding raster shift which otherwise could occur as a result of the use of non-equidistant vertical synchronizing pulses.
Inventors
- 👤 Willem Den Hollander
- 👤 Giovanni Michele Leonardi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 23:07
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/01; H04N7/0127; H04N7/0132
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
174 words
A television display system in which an input interlaced video signal is written to a memory means (40, 202, 204), and read from the memory means at a field rate substantially double the field rate of the input signal, so that a written field is read twice, and having a display means (60) on which the double field rate signal is displayed in accordance with a vertical synchronizing signal (2Vʹ), characterised in that the number of lines per field in the double field rate signal varies but averages the number of lines per field of the input signal, and the vertical synchronising signal defines field periods for the display means of varying length but which average half the field period of the input signal, the number of lines in a given field in the double field rate signal and the period for the given field specified by the vertical synchronising signal being arranged such that even fields overlay even fields, odd fields overlay odd fields, and even and odd pairs of fields are interlaced.
Claim 2
Dependent Claim
174 words
A television display system in which an input interlaced video signal is written to a memory means (40, 202, 204), and read from the memory means at a field rate substantially double the field rate of the input signal, so that a written field is read twice, and having a display means (60) on which the double field rate signal is displayed in accordance with a vertical synchronizing signal (2Vʹ), characterised in that the number of lines per field in the double field rate signal varies but averages the number of lines per field of the input signal, and the vertical synchronising signal defines field periods for the display means of varying length but which average half the field period of the input signal, the number of lines in a given field in the double field rate signal and the period for the given field specified by the vertical synchronising signal being arranged such that even fields overlay even fields, odd fields overlay odd fields, and even and odd pairs of fields are interlaced.
Claim 3
Dependent Claim
54 words
A system according to Claim 1 in which the number of lines per field in the double field rate signal varies between two values, one of which is half a line longer than the number of lines per input field and the other of which is half a line shorter than the input field.
Claim 4
Dependent Claim
27 words
A system according to Claim 1 or Claim 2 in which the number of lines per field in the double field rate signal alternates between two values.
Claim 5
Dependent Claim
32 words
A system according to Claim 1 or Claim 2 in which the number of lines per field in the double field rate signal varies between two values on a four field cycle.
Claim 6
Dependent Claim
22 words
A system according to Claim 4 in which the two readings of each written field have different numbers of lines per field.
Claim 7
Independent Claim
26 words
A system according to any one of the preceding claims in which each field in the double field rate signal has a whole number of lines.
Claim 8
Independent Claim
45 words
A system according to any one of the preceding claims in which for the first of the two readings of each written field the field period defined by the vertical synchronising signal (2Vʹ) equals the period of the field in the double field rate signal.
Claim 9
Independent Claim
74 words
A system according to any one of the preceding claims in which for the second reading of each written field the field period defined by the vertical synchronising signal (2Vʹ) differs by half a line period from the period of the field in the double field rate signal, the period defined by the vertical synchronising signal being half a line period short for odd fields and half a line period long for even fields.
Claim 10
Independent Claim
50 words
A system according to any one of the preceding claims in which each field of the double field rate signal contains a given number of active lines read from the memory means, and at least some fields of the double field rate signal also contain at least one blank line.
Claim 11
Dependent Claim
48 words
A television display system according to any one of the preceding claims further comprising scan generator means responsive to the vertical synchronising signal (2Vʹ) for supplying a vertical scan signal to said display means of sawtooth form having a fixed starting point and a constant retrace time interval.
Claim 12
Dependent Claim
144 words
A television display system according to any one of the preceding claims in which a timing means (70) provides the said vertical synchronising signal (2Vʹ) and a read-out field signal (2V) which defines the fields of the double field rate signal, which timing means includes phase lock loop means(306, 308, 310, 312, 314) responsive to a horizontal synchronizing component (HS) of said video input signal for providing a double line-rate output signal (2H), counter means (316) responsive to said double line rate output signal for providing a vertical rate output signal (V), phase detector means (318) coupled to said counter means (316) for synchronizing said vertical rate signal (V) with a vertical synchronizing component (VS) of said video input signal and decoder means (320, 322) coupled to said counter means (316) for producing said vertical synchronising signal (2Vʹ) and said readout field signal (2V).
Claim 13
Dependent Claim
50 words
A television display apparatus according to claim 11 in which said phase lock loop means includes controllable oscillator means (308) having a given frequency control range and frequency multplier means (310) in said phase lock loop means so as to increase the effective control range of said controllable oscillator means.
Claim 14
Dependent Claim
172 words
A television display method in which an input interlaced video signal is written to a memory means (40, 202, 204), and read from the memory means at a field rate substantially double the field rate of the input signal, so that a written field is read twice, and the double field rate signal is displayed on a display means (60) in accordance with a vertical synchronising signal (2Vʹ), characterised in that the number of lines per field in the double field rate signal varies but averages the number of lines per field of the input signal, and the vertical synchronising signal defines field periods for the display means of varying length but which average half the field period of the input signal, the number of lines in a given field in the double field rate signal and the period for the given field specified by the vertical synchronising signal being arranged such that even fields overlay even fields, odd fields overlay odd fields, and even and odd pairs of fields are interlaced.
Claim 15
Dependent Claim
172 words
A television display method in which an input interlaced video signal is written to a memory means (40, 202, 204), and read from the memory means at a field rate substantially double the field rate of the input signal, so that a written field is read twice, and the double field rate signal is displayed on a display means (60) in accordance with a vertical synchronising signal (2Vʹ), characterised in that the number of lines per field in the double field rate signal varies but averages the number of lines per field of the input signal, and the vertical synchronising signal defines field periods for the display means of varying length but which average half the field period of the input signal, the number of lines in a given field in the double field rate signal and the period for the given field specified by the vertical synchronising signal being arranged such that even fields overlay even fields, odd fields overlay odd fields, and even and odd pairs of fields are interlaced.
Claim 16
Dependent Claim
104 words
A television display system in which an input interlaced video signal is displayed on a display means (60) in accordance with a vertical synchronising signal (2Vʹ), the video signal being displayed at an increased rate and fields of the input video signal being repeated on the display means, characterised in that the timing of the vertical synchronising signal (2Vʹ) is varied to vary the field periods of the display means so that although fields of the input video signal are repeated on the display means even fields overlay even fields, odd fields overlay odd fields, and even and odd sets of fields are interlaced.
Claim 17
Dependent Claim
104 words
A television display system in which an input interlaced video signal is displayed on a display means (60) in accordance with a vertical synchronising signal (2Vʹ), the video signal being displayed at an increased rate and fields of the input video signal being repeated on the display means, characterised in that the timing of the vertical synchronising signal (2Vʹ) is varied to vary the field periods of the display means so that although fields of the input video signal are repeated on the display means even fields overlay even fields, odd fields overlay odd fields, and even and odd sets of fields are interlaced.
References Cited (Backward Citations)
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