US4255658A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Image forming apparatus
Assignee: EMI Ltd
•
Filing: 1979-02-05
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Granted: 1981-03-10
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Expires: 1999-02-05
Abstract
Abstract The imager comprises an array 4 of detectors, and an array 6 of LEDs each detector being connected to a corresponding LED by a respective signal processing channel 5a. Common to all the channels is a ramp generator 12. Each channel has a comparator 9 which compares the ramp with the signal from its detector to produce a pulse width modulated signal for its LED. Thus the LED is always driven at the same point on its characteristic, variation of brightness being achieved by variation of pulse width. Use of a common ramp generator makes for simple change of ramp shape, temperature window, offset and γ law by simply changing only the ramp generator.
Inventors
- 👤 Ivan R. Hurst
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 13:35
CPC Classifications
H; H04; H04N; H04N23/00; H04N23/20; H04N23/23
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
185 words
An image forming apparatus including a plurality of detectors responsive to thermal radiation from a scene to produce respective electrical signals; a plurality of light emissive diode devices; a plurality of channels coupling the detectors to the light emissive diode devices, each channel including a comparator arranged to compare a repetitive sampling signal, having a waveform in the form of a ramp, with the electrical signal produced by its associated detector to produce for its associated light emissive diode device electrical pulses of widths determined by the electrical signal and the sampling signal, the emissive devices being responsive to the electrical pulses to provide corresponding light pulses; a generator common to all the channels for producing the sampling signal, the generator including means for varying the slope of the ramp and means for applying an adjustable d.c. bias to the ramp whereby contrast and offset are variable; and scanning means arranged to cause the electrical signals to represent portions of the object according to a predetermined scanning pattern and to cause the light pulses to form an image of the scene according to that pattern.
Claim 2
Dependent Claim
185 words
An image forming apparatus including a plurality of detectors responsive to thermal radiation from a scene to produce respective electrical signals; a plurality of light emissive diode devices; a plurality of channels coupling the detectors to the light emissive diode devices, each channel including a comparator arranged to compare a repetitive sampling signal, having a waveform in the form of a ramp, with the electrical signal produced by its associated detector to produce for its associated light emissive diode device electrical pulses of widths determined by the electrical signal and the sampling signal, the emissive devices being responsive to the electrical pulses to provide corresponding light pulses; a generator common to all the channels for producing the sampling signal, the generator including means for varying the slope of the ramp and means for applying an adjustable d.c. bias to the ramp whereby contrast and offset are variable; and scanning means arranged to cause the electrical signals to represent portions of the object according to a predetermined scanning pattern and to cause the light pulses to form an image of the scene according to that pattern.
Claim 3
Dependent Claim
24 words
Apparatus according to claim 1, wherein the comparator of each channel comprises a differential amplifier provided with positive feedback to give a Schmitt action.
Claim 4
Dependent Claim
30 words
Apparatus according to claim 1, wherein the sampling signal generator is mounted on a circuit board alone, and all other circuits are mounted on at least one other circuit board.
Claim 5
Dependent Claim
39 words
Apparatus according to claim 1, wherein a clamp pulse generaor common to all the channels and the sampling signal generator are mounted on the same circuit board, all other circuits being mounted on at least one other circuit board.
Claim 6
Dependent Claim
12 words
Apparatus according to claim 1, wherein said ramp has a linear form.
Claim 7
Dependent Claim
12 words
Apparatus according to claim 1, wherein said ramp has an exponential form.
Claim 8
Dependent Claim
37 words
Apparatus according to claim 1, comprising a clamping pulse generator common to all the channels and wherein the channels comprise respective means for setting the D.C. levels of the channels in response to the clamping pulse generator.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-03-09 | 1984-09-08 | 1985-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-09 | 1988-09-08 | 1989-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-09 | 1992-09-08 | 1993-03-10 | $7700.00 | Window Closed / Lapsed |