Patent ID: 6483091
Filing Date: 2002-11-19
Classification: G02B

Abstract:
Dynamic autofocusing apparatus comprising:a lens system having a focal plane; a scanning surface for receiving light from the lens system; a position sensor for measuring the position of the surface with respect to the focal plane to generate a position signal; a transducer for altering the relative position of the focal plane and the surface; an inner control loop responsive to the position signal and a position setpoint to control the transducer to set the relative position of the focal plane and the scanning surface; an outer control loop responsive to deviation in the relative position of the scanning surface with respect to the focal plane of the lens from the focus setpoint to generate an error signal, the error signal forming the position setpoint to the inner control loop; and a sample-and-hold functional element disposed between the inner and outer control loops, the sample and hold element switched between sample and hold states by an edge or defect detector.