| 摘要 |
<p>An apparatus for providing continuous, automatic background compensation in a scanning optical detection system includes a video camera (1), a signal sampling means (2) controlled by a valid data strobe and comparator means (6) for comparing the signals from the sampling means and the video signal reference. The system is provided with an amplifier (3), an averaging circuit (4), a threshold level adjustment circuit (7) and a threshold summing circuit (5) connected to the outputs of the averaging circuit and the threshold level adjustment circuit, wherein an error signal produced by the amplifier (3) is used to modify the current value of the averaging circuit (4) and the output from the latter is summed in the threshold summing circuit (5) with the output signal from the threshold level adjustment circuit (7). The resultant output signal from the threshold summing circuit is compared in said comparator (6) with the video signal to output a reject signal in the event that the video signal is greater than the output signal from the threshold summing circuit (5).</p> |
