Patent DE476929C successfully refreshed from Google Patents.
US3798367A
Expired / Lapsed
US
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Apparatus for elimination of interference from video signals
Assignee: Siemens AG
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Filing: 1971-10-14
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Granted: 1974-03-19
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Expires: 1991-10-14
Abstract
Abstract Apparatus is described for eliminating interferences in the video signals in video telephony or in other applications where the image receiving tube at the transmitter has a short storage time. A filter circuit is described for accomplishing the elimination of such interference, and this filter circuit is preferably placed at the transmission end of the video telephone circuit. The filter basically comprises a series arrangement of a logarithmic amplifier, a band elimination filter tuned to double the power frequency, a limiter and a potentiometer. The video signal is clamped to the black level prior to being coupled to the aforementioned filter arrangement. After the signal has been so filtered, the necessary picture gating, line gating and synchronizing signals may be added, as necessary. Other arrangements are described in which the interference frequency is branched off from the main circuit to be mixed with the disturbed video signal. This branching may be accomplished either electrically or optically.
Inventors
- 👤 A Schneider
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:18
CPC Classifications
H; H03; H03D; H03D1/00; H03D1/02; H03D1/04; H04; H04N; H04N23/00; H04N23/80; H04N23/81; H04N3/00; H04N3/10; H04N3/16; H04N7/00; H04N7/14; H04N7/141
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
164 words
Apparatus for use in video signal transmission circuitry for eliminating interference resulting from a frame frequency different from the frequency of the light illuminating the subject photographed comprising: means for clamping the camera output signal to the black signal level, filter means for removing the interference frequency resulting from said illumination frequency and adder means for adding to the filter signal picture gating, line gating, synchronizing and other signals necessary for facilitating the reproduction of a picture at a receiver, said filter means comprising: logarithmic amplifier means for receiving said clamped signal and producing the logarithmic equivalent of said clamp signal, band-elimination filter means tuned to a frequency twice the value of the illuminating light frequency, said logarithmic signal being applied to said filter, limiter means coupled to the output of said band elimination filter and potential adjusting means for receiving the output of said limiter and producing the antilogarithm thereof, the output of said potential adjusting means being coupled to said adder means.
Claim 2
Dependent Claim
164 words
Apparatus for use in video signal transmission circuitry for eliminating interference resulting from a frame frequency different from the frequency of the light illuminating the subject photographed comprising: means for clamping the camera output signal to the black signal level, filter means for removing the interference frequency resulting from said illumination frequency and adder means for adding to the filter signal picture gating, line gating, synchronizing and other signals necessary for facilitating the reproduction of a picture at a receiver, said filter means comprising: logarithmic amplifier means for receiving said clamped signal and producing the logarithmic equivalent of said clamp signal, band-elimination filter means tuned to a frequency twice the value of the illuminating light frequency, said logarithmic signal being applied to said filter, limiter means coupled to the output of said band elimination filter and potential adjusting means for receiving the output of said limiter and producing the antilogarithm thereof, the output of said potential adjusting means being coupled to said adder means.
Claim 3
Dependent Claim
101 words
The apparatus defined in claim 1, further comprising: comparison means for receiving the outputs of said logarithmic amplifier and said band-elimination filter and for producing a signal corresponding to the difference between the values of said logarithmic amplifier output signal and said band-elimination filter output signal, and electronic switch means, which, when rendered operative, renders said band-elimination filter inoperative, said electronic switch means being rendered operative upon receiving a signal of a predetermined amplitude, the output of said comparison means being applied to said electronic switch means, said predetermined amplitude being an amplitude greater than the amplitude of said interference frequency.
Claim 4
Dependent Claim
25 words
The apparatus defined in claim 2, wherein said electronic switch, includes means for short circuiting said band-elimination filter when said electronic switch is rendered operative.
Claim 5
Dependent Claim
53 words
The apparatus defined in claim 1 wherein said limiter includes means for adjusting the threshold of operation of said limiter to a value which is above a signal level corresponding to said black signal level by an amount which is at least equal to the value of the amplitude of a half wave.
Claim 6
Dependent Claim
99 words
The apparatus defined in claim 1, wherein said filter means comprises: band-pass filter means tuned to the interference frequency and connected to receive the camera output signal, phase reversing amplifier means connected to receive the output of said band-pass filter, summing means having two inputs, the first of said inputs being connected to the output of said phase reversing amplifier and the second of said inputs being connected to directly receive the camera output signal, and limiter means connected to receive the output of said summing means, the output of said limiter means being connected to said adder means.
Claim 7
Dependent Claim
83 words
The apparatus defined in claim 5, further comprising: logarithmic amplifier means having an input connected to the output of said clamping means and an output connected to the input of said band pass filter means tuned to the interference frequency, said logarithmic amplifier having an additional output connected to an input of said summing means and, potential adjusting means connected to an output of said limiter means and an input of said adder means for producing the antilogarithm of the signal passing therethrough.
Claim 8
Dependent Claim
27 words
The apparatus defined in claim 5, wherein said means is constructed as a frequency divider for adding the pure interference frequency signal and the camera output signal.
Claim 9
Dependent Claim
46 words
The apparatus defined in claim 7, wherein tHe input of said band pass filter is connected to an output of said limiter means and wherein the output of said band pass filter is connected to an input of said frequency divider means constituting said summing means.
Claim 10
Dependent Claim
94 words
The apparatus defined in claim 5, further comprising: regulating amplifier means for controlling the amplitude of a signal applied thereto, said regulating amplifier being interposed between the output of said band-pass filter means and the first input to said summing means for controlling the amplitude of the interference frequency, means for supplying a potential to said regulating amplifier for controlling the amplification factor thereof, said regulating potential being the output of said band-pass filter and means for connecting a signal of the power line frequency directly to said regulating amplifier to be amplified therein.
Claim 11
Dependent Claim
41 words
The apparatus defined in claim 9, further comprising: phase shifting means interposed in said means for coupling the power line frequency to said regulating amplifier to adjust the phase thereof, relative to the interference frequency contained in the camera output signal.
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) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |