Automatic level control circuit

摘要

A scanning apparatus which periodically sweeps a beam of light across a printed circuit board along a plurality of sweep paths, includes a detector responsive to radiation from the printed circuit board as the board is swept by the beam of light. The detector is also responsive to first and second adjustment signals indicating whether a conductor portion or substrate portion of the board is being swept. An automatic level control is responsive to the first and second signals for providing level adjusted output signals via an adjustor coupled to the detector. The levels of the output signals form a ratio R substantially the same for all boards swept in the scanning apparatus.