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US3984629A Expired / Lapsed US ⏱️ 0.0 years remaining

Flying spot scanner unaffected by ambient light

Assignee: RCA Corp
•
Filing: 1974-12-23
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Granted: 1976-10-05
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Expires: 1994-12-23
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Abstract

Abstract A flying spot scanner is disclosed for scanning an object document or scene with a spot of light, and producing an electrical video signal representing the object. The scanner can be operated under normal ambient light conditions without a light-shielding enclosure. A light beam is deflected in repetitive scanning fashion over the object. The light beam is modulated in amplitude (intensity) at a radio frequency f c such as 1.2 MHz. A photodetector is positioned to receive light from the object, and it produces an unwanted electrical ambient light noise signal having a maximum frequency f a , and an electrical information signal consisting of a carrier at frequency f c modulated by a video signal having a maximum frequency f m , where f c - f m is larger than f a . The information signal is separated from the ambient light noise signal by a filter, and the information signal is demodulated to produce a facsimile or video information signal free of noise due to ambient light.

Inventors

  • 👤 Istvan Gorog

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-23 15:18
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/222; H04N5/257

Claims Analysis

Total Claims: 8
Claim 1
Independent Claim 172 words
A flying spot scanner for scanning an object document or scene with a spot of light and producing an electrical viedo signal representing the object, comprising a light beam source, means to deflect the light beam in scanning fashion over the object, means to modulate the amplitude of the light beam at a frequency f c , a photodetector positioned to receive light from the object and produce an unwanted electrical ambient light noise signal having a maximum frequency f a , and an electrical information signal consisting of a carrier at frequency f c modulated by a viedo signal having a maximum frequency f m , where f c - f m is larger than f a , a filter coupled to the output of said photodetector for rejecting said noise signals to frequency f a , and a detector having an input coupled to the output of said filter for demodulating a carrier at frequency f c and producing an output video information signal having frequencies to f m .
Claim 2
Dependent Claim 172 words
A flying spot scanner for scanning an object document or scene with a spot of light and producing an electrical viedo signal representing the object, comprising a light beam source, means to deflect the light beam in scanning fashion over the object, means to modulate the amplitude of the light beam at a frequency f c , a photodetector positioned to receive light from the object and produce an unwanted electrical ambient light noise signal having a maximum frequency f a , and an electrical information signal consisting of a carrier at frequency f c modulated by a viedo signal having a maximum frequency f m , where f c - f m is larger than f a , a filter coupled to the output of said photodetector for rejecting said noise signals to frequency f a , and a detector having an input coupled to the output of said filter for demodulating a carrier at frequency f c and producing an output video information signal having frequencies to f m .
Claim 3
Dependent Claim 14 words
A scanner as defined in claim 1 wherein said detector is a synchronous detector.
Claim 4
Dependent Claim 25 words
A scanner as defined in claim 1, and, in addition, a low-pass filter following said detector and providing an output free of ambient light noise.
Claim 5
Dependent Claim 34 words
A scanner as defined in claim 1 wherein said filter is a band pass filter which passes the carrier f c and its sidebands, and attenuates the noise at frequencies to f a .
Claim 6
Dependent Claim 15 words
A scanner as defined in claim 1 wherein said light beam source includes a laser.
Claim 7
Dependent Claim 20 words
A scanner as defined in claim 5 wherein said laser is a semiconductor injection laser supplied with a drive current.
Claim 8
Dependent Claim 26 words
A scanner as defined in claim 6 wherein said means to modulate the amplitude of the light beam consists of means to modulate said drive current.

References Cited (Backward Citations)

US2476698A Cited
US2982816A Cited
US3003026A Cited
US3230292A Cited
US3830972A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1979-10-05 1980-04-05 1980-10-05 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1983-10-05 1984-04-05 1984-10-05 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1987-10-05 1988-04-05 1988-10-05 $7700.00 Window Closed / Lapsed

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