Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1984-09-10
1986-10-28
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
340707, G09G 302, G06K 710
Patent
active
046201076
ABSTRACT:
An automatically compensated light pen for use with a video display monitor incorporating a cathode ray tube, including, a detector for detecting light pulses produced by the cathode ray tube when the detector is positioned adjacent the cathode ray tube at a particular desired location and for producing electrical pulses in accordance with the light pulses, a variable attenuator having a first input coupled to the output of the detector and responsive to the electrical pulses from the detector for producing variably attenuated electrical pulses and having a second control input responsive to a control signal for controlling the level of the variably attenuated electrical pulses, a threshold comparator coupled to the output of the variable attenuator and responsive to the variably attenuated electrical pulses for producing output electrical pulses when the level of the variably attenuated electrical pulses are higher than a particular threshold level for the threshold comparator, and a peak detector coupled between the output of the variable comparator and the control input of the variable attenuator and responsive to the variably attenuated electrical pulses for producing a control signal coupled to the control input of the variable attenuator when the level of the variably attenuated electrical pulses are higher than a particular peak level for the peak detector and with the particular threshold level for the threshold comparator less than the particular peak level for the peak detector.
REFERENCES:
patent: 3852721 (1974-12-01), Tucker et al.
patent: 4451895 (1984-05-01), Sliwkowski
Liprad Associates
Nelms David C.
Oen William L.
Roston Ellsworth R.
Schwartz Charles H.
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