| 摘要 |
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. |
