US3566018A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Color television signal generating system
Assignee: RCA Corp
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Filing: 1969-03-06
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Granted: 1971-02-23
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Expires: 1989-03-06
Abstract
Abstract Light from a colored subject is projected onto the photosensitive electrode of a camera tube through a spatial color encoding filter grating including strips of subtractive color material equally transmissive of white light so that scansion of the electrode by an electron beam produces in the camera tube output color difference signals as amplitude modulations of different phases of a single suppressed carrier wave, the envelopes of which are subject to polarity ambiguities because of the suppression of the wave. A constant intensity light, which is modified by an auxiliary signal encoding filter grating, is projected onto the photosensitive camera tube electrode so that the interaction between the light passing through the two gratings produces a plurality of unmodulated waves of different frequencies in the camera tube output. Selected ones of these unmodulated waves are mixed to produce a reference wave of fixed amplitude and phase at the color carrier frequency and are applied to synchronous detectors in such phases as to recover the color difference signals from the phase modulated color carrier wave with no polarity ambiguities.
Inventors
- 👤 Albert Macovski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 09:51
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/01
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
383 words
In a color television system, an unambiguous color difference signal generating system, comprising: a camera tube having a photosensitive electrode responsive to light projected thereon and to scansion by an electron beam to produce signals at its output terminal representative of said projected light; a spatial color difference signal encoding filter grating in the light path between a colored subject and said photosensitive camera tube electrode, said grating having a plurality of sets of subtractive color selective parallel strips extending perpendicular to the scanning direction of said electron beam, all of said strips being equally transmissive of white light so as to produce in the output of said camera tube a suppressed color carrier wave of a frequency Fc, first and second phases of which are amplitude modulated by respective color difference signals which may have polarity ambiguities because of said color carrier wave suppression; a source of constant intensity light; an auxiliary signal encoding filter grating having a plurality of sets of a parallel strips to modify light projected therethrough at a frequency Fa; optical means for projecting light from said source through said auxiliary signal encoding grating and through said color difference signal encoding grating onto the photosensitive electrode of said camera tube so as to produce in said camera tube output terminal at least two unmodulated waves at respectively different frequencies; reference frequency generating means coupled to said camera tube output terminal for combining said unmodulated waves to produce an a unambiguous reference frequency wave of fixed amplitude and having said color carrier wave frequency Fc; first synchronous detecting means coupled to said camera tube output terminal for response to said color difference signal modulated suppressed carrier wave and coupled to said reference frequency generating means for response to said reference frequency wave in a first phase corresponding to said first color carrier wave phase to produce one of said color difference signals with no polarity ambiguity; and second synchronous detecting means coupled to said camera tube output terminal for response to said color difference signal modulated suppressed carrier wave and coupled to said reference frequency generating means for response to said reference frequency wave in a second phase corresponding to said second color carrier wave phase to produce the other of said color difference signals with no polarity ambiguity.
Claim 2
Dependent Claim
383 words
In a color television system, an unambiguous color difference signal generating system, comprising: a camera tube having a photosensitive electrode responsive to light projected thereon and to scansion by an electron beam to produce signals at its output terminal representative of said projected light; a spatial color difference signal encoding filter grating in the light path between a colored subject and said photosensitive camera tube electrode, said grating having a plurality of sets of subtractive color selective parallel strips extending perpendicular to the scanning direction of said electron beam, all of said strips being equally transmissive of white light so as to produce in the output of said camera tube a suppressed color carrier wave of a frequency Fc, first and second phases of which are amplitude modulated by respective color difference signals which may have polarity ambiguities because of said color carrier wave suppression; a source of constant intensity light; an auxiliary signal encoding filter grating having a plurality of sets of a parallel strips to modify light projected therethrough at a frequency Fa; optical means for projecting light from said source through said auxiliary signal encoding grating and through said color difference signal encoding grating onto the photosensitive electrode of said camera tube so as to produce in said camera tube output terminal at least two unmodulated waves at respectively different frequencies; reference frequency generating means coupled to said camera tube output terminal for combining said unmodulated waves to produce an a unambiguous reference frequency wave of fixed amplitude and having said color carrier wave frequency Fc; first synchronous detecting means coupled to said camera tube output terminal for response to said color difference signal modulated suppressed carrier wave and coupled to said reference frequency generating means for response to said reference frequency wave in a first phase corresponding to said first color carrier wave phase to produce one of said color difference signals with no polarity ambiguity; and second synchronous detecting means coupled to said camera tube output terminal for response to said color difference signal modulated suppressed carrier wave and coupled to said reference frequency generating means for response to said reference frequency wave in a second phase corresponding to said second color carrier wave phase to produce the other of said color difference signals with no polarity ambiguity.
Claim 3
Dependent Claim
97 words
In a color television system, an unambiguous color difference signal generating system as defined in claim 1, wherein: said constant intensity light has such a color that, when modified by said auxiliary signal encoding grating, its interaction with said color difference signal encoding grating produces said different frequency unmodulated waves in said camera tube output in such phases that said reference frequency produced in said reference generating means output has said first phase; and said second synchronous detecting means is coupled to said reference frequency generating means output through a phase shifter to produce said second phase.
Claim 4
Dependent Claim
71 words
In a color television system, an unambiguous color difference signal generating system as defined in claim 2, wherein: said spatial color difference signal encoding filter grating comprises a plurality of regularly repeating sets of three equal width subtractive color selective parallel strips, whereby said first and second phases of said color carrier wave differ by 120* ; and said phase shifter shifts the phase of said reference frequency wave by 120*.
Claim 5
Dependent Claim
99 words
In a color television system, an unambiguous color difference signal generating system as defined in claim 2, wherein: said spatial color difference signal encoding filter grating comprises a plurality of regularly repeating sets of two equal width subtractive Color selective parallel strips and a neutral gray strip having twice the width of each of said color selective strips and having white light transmissivity equal to that of said color selective strips, whereby said first and second phases of said color carrier wave differ by 90*; and said phase shifter shifts the phase of said reference frequency wave by 90*.
Claim 6
Dependent Claim
61 words
In a color television system, an unambiguous color difference signal generating system as defined in claim 1, wherein: said auxiliary signal encoding filter grating comprises a plurality of regularly repeating sets of alternate opaque and transparent strips to modify the light projected therethrough from said source of constant intensity light at least one frequency higher than said color carrier frequency Fc.
Claim 7
Dependent Claim
55 words
In a color television system, an unambiguous color difference signal generating system as defined in claim 5, wherein: the alternate opaque and transparent strips of said auxiliary signal encoding filter grating are of equal widths, whereby said light modification is effected substantially only at a single fundamental frequency higher than said color carrier frequency Fc.
Claim 8
Dependent Claim
60 words
In a color television system, an unambiguous color difference signal generating system as defined in claim 5, wherein: the alternate opaque and transparent strips of said auxiliary signal encoding filter grating have respectively different widths, whereby said light modification is effected at a fundamental and its second harmonic frequencies, both of which are higher than said color carrier frequency Fc.
Claim 9
Dependent Claim
110 words
In a color television system, an unambiguous color difference signal generating system as defined in claim 1, wherein: said constant intensity light is white; and said auxiliary signal encoding filter grating comprises a plurality of regularly repeating sets of alternate additive and subtractive color strips, the colors of said strips being complementary and the strips being equally transmissive of said white light, whereby the light modified by said auxiliary signal encoding grating, when projected through said color difference signal encoding grating onto said camera tube photosensitive electrode, produces in said camera tube output two reference signal frequency components having a 180* mutual phase relationship and no resultant AC luminance signal.
Claim 10
Dependent Claim
103 words
In a color television system, an unambiguous color difference signal generating system as defined in claim 8, wherein: said alternative additive and subtractive color strips have widths such that said white light is modified at a relatively low frequency which is only slightly higher than the desired bandwidth of the color difference signals, said relative strip widths being such that the average of each of said two reference frequency components is the same, whereby no carrier wave at least relatively low frequency is produced, but only sidebands around said suppressed color carrier wave, said sidebands constituting said unmodulated waves at respectively different frequencies.
Claim 11
Dependent Claim
247 words
In a color television system in which is produced, in addition to a band of relatively low frequency luminance signals, a color difference signal which is amplitude modulated on a suppressed carrier wave of a frequency Fc above said luminance signal frequency band by projecting light from a colored subject onto a photosensitive electrode of a camera tube through a color difference signal encoding filter grating, the envelope of said color carrier wave produced in the output of said camera tube by an electron beam scansion of said photosensitive electrode having a polarity ambiguity because of the suppression of said color carrier wave, an unambiguous demodulation system for recovering said color difference signal from said color carrier wave, comprising: means including an auxiliary signal encoding grating through which constant intensity light, modified at a frequency Fa by said auxiliary signal encoding grating, is projected onto said camera tube photosensitive electrode through said color difference signal encoding grating with which it interacts to produce in said camera tube output at least two unmodulated waves at respectively different frequencies; reference frequency generating means for combining said unmodulated waves derived from said camera tube output to produce an unambiguous fixed amplitude wave at said color carrier wave frequency Fc; and synchronous detecting means responsive to said color difference signal modulated suppressed carrier wave derived from said camera tube output and to said unambiguous fixed amplitude wave having such phase as to produce an output color difference signal of unambiguous polarity.
Claim 12
Dependent Claim
247 words
In a color television system in which is produced, in addition to a band of relatively low frequency luminance signals, a color difference signal which is amplitude modulated on a suppressed carrier wave of a frequency Fc above said luminance signal frequency band by projecting light from a colored subject onto a photosensitive electrode of a camera tube through a color difference signal encoding filter grating, the envelope of said color carrier wave produced in the output of said camera tube by an electron beam scansion of said photosensitive electrode having a polarity ambiguity because of the suppression of said color carrier wave, an unambiguous demodulation system for recovering said color difference signal from said color carrier wave, comprising: means including an auxiliary signal encoding grating through which constant intensity light, modified at a frequency Fa by said auxiliary signal encoding grating, is projected onto said camera tube photosensitive electrode through said color difference signal encoding grating with which it interacts to produce in said camera tube output at least two unmodulated waves at respectively different frequencies; reference frequency generating means for combining said unmodulated waves derived from said camera tube output to produce an unambiguous fixed amplitude wave at said color carrier wave frequency Fc; and synchronous detecting means responsive to said color difference signal modulated suppressed carrier wave derived from said camera tube output and to said unambiguous fixed amplitude wave having such phase as to produce an output color difference signal of unambiguous polarity.
Claim 13
Dependent Claim
44 words
In a color television system, an unambiguous demodulation system as defined in claim 10; wherein: said auxiliary signal grating comprises alternate strips of transparent and opaque materials; and said constant intensity light is colored, the particular color determining the phase of said auxiliary signal.
Claim 14
Dependent Claim
104 words
In a color television system, an unambiguous demodulation system as defined in claim 11, wherein: a first one of said unmodulated waves derived from said camera tube output has said frequency Fa which is higher than said color carrier wave frequency Fc, and a second one of said unmodulated waves derived from said camera tube output has a frequency (Fa + Fc) which also is higher than said carrier wave frequency Fc; and said reference frequency generating means includes a frequency mixer responsive to said first and second unmodulated waves to produce said unambiguous fixed amplitude wave having said color carrier wave frequency Fc.
Claim 15
Dependent Claim
147 words
In a color television system, an unambiguous demodulation system as defined in claim 11, wherein: said auxiliary signal grating is of a character to modify said constant intensity light so as to produce in said camera tube output in conjunction with said color difference signal grating a first unmodulated wave having a frequency Fa1 which is higher than said color carrier wave frequency Fc, and a second unmodulated wave having a frequency (2Fa1 - Fc) which also is higher than said color carrier wave frequency Fc; and said reference signal generating means includes frequency multiplying means to double the frequency of said first unmodulated wave to 2Fa1, and a first frequency mixer responsive to said doubled frequency 2Fa1 of said first unmodulated wave and to said second unmodulated wave frequency (2Fa1 - Fc) to produce said unambiguous fixed amplitude wave having said color carrier wave frequency Fc.
Claim 16
Dependent Claim
128 words
In a color television system, an unambiguous demodulation system as defined in claim 13, wherein: the character of said auxiliary signal grating is such that there is produced in said camera tube output an undesired third unmodulated wave having a frequency (Fa1 - Fc) which is lower than said color carrier wave frequency Fc and is within said luminance signal frequency band; and said reference frequency generating means also includes a second frequency mixer responsive to said second unmodulated wave having said frequency (2Fa1 - Fc) and to said unmodulated wave of frequency Fa1 to produce a compensating wave having a frequency (Fa1 - Fc), and means for combining said compensating wave with said luminance signal in such polarity and amplitude to cancel said undesired third unmodulated wave.
Claim 17
Dependent Claim
123 words
In a color television system, an unambiguous demodulation system as defined in claim 11, wherein: the interaction between said constant intensity colored light, modified at said frequency Fa, with said color difference signal encoding grating, in addition to producing said desired unmodulated waves at dIfferent frequencies, produces an average component which forms an undesired uniform additive color difference signal over the entire field of the picture; and said reference frequency generating means also includes envelope detecting means responsive to one of said unmodulated waves at said frequency Fa to produce a pedestal signal, and means for combining said pedestal signal with said unambiguously recovered color difference signal in such polarity and amplitude to subtract said undesired signal from said recovered color difference signal.
Claim 18
Dependent Claim
71 words
In a color television system, an unambiguous demodulation system as defined in claim 10, wherein: said constant intensity light is white; and said auxiliary signal grating comprises alternate strips of complementary color selective materials which are equally transmissive of said white light, whereby said white light is modified at a frequency Fa2 which is lower than said color carrier wave frequency Fc and the wave at said frequency Fa2 is suppressed.
Claim 19
Dependent Claim
150 words
In a color television system, an unambiguous demodulation system as defined in claim 16, wherein: the projection of said modified white light at frequency Fa2 through said color difference signal encoding grating onto said camera tube photosensitive electrode produces in the output of said camera tube, by said electron beam scansion of said electrode, a first unmodulated wave of frequency (Fc + Fa2) and a second unmodulated wave of frequency (Fc + 2Fa2), both of which are higher than said color carrier wave frequency Fc; and said reference frequency generating means includes frequency multiplying means to double the frequency of said first unmodulated wave to a frequency 2(Fc + Fa2), and a frequency mixer responsive to said doubled frequency 2(Fc + Fa2) of said first unmodulated wave and to said second unmodulated wave frequency (Fc + 2Fa2 to produce said fixed amplitude wave having said color carrier wave frequency Fc.
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) | 1974-02-22 | 1974-08-24 | 1975-02-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-02-22 | 1978-08-24 | 1979-02-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-02-22 | 1982-08-24 | 1983-02-23 | $7700.00 | Window Closed / Lapsed |