Patent ID: 7400415

Claim:
An apparatus for controlling a surface displacement transducer, wherein the surface displacement transducer comprises: signal generating and processing circuitry including a memory; a light source arranged to direct a beam of light onto a target surface; and a detector configured to obtain an image of a beam spot produced by reflecting the beam of light from the target surface onto the detector, the detector including a number of pixels greater than a subset of pixels which participates in a surface displacement calculation of the surface displacement transducer, and the apparatus comprises: an input device that is configured to allows an operator to select at least one candidate location of the subset of pixels of the detector which participate in the surface displacement calculation of the surface displacement transducer, the input device comprising at least one of a mouse, a pointer, a joystick and a keyboard; a display that displays an image obtained by the surface displacement transducer, and at least one selected candidate location of the subset of pixels; and a first controller which is configured to operate the apparatus to: command the surface displacement transducer to direct the beam of light onto the target surface and obtain an image of the beam spot produced by reflecting the beam of light from the target surface onto the detector; display the obtained image and at least one selected candidate location of the subset of pixels on the display; calculates at least one figure of merit associated with each selected candidate location of the subset of pixels; determine a location for the subset of pixels based at least partially on at least one figure of merit associated with the at least one selected candidate location for the subset of the pixels; and command the signal generating and processing circuitry to store the determined location for the subset of pixels in the memory.