Method and apparatus for determining the position of an object

An apparatus for determining the position of an object, comprising:

• a source of an electromagnetic radiation beam;
• an array of spaced, electromagnetic radiation beam detectors for said beam, each detector including detector signal producing means associated therewith for producing a variable magnitude detector signal in response to the intensity of electromagnetic radiation impinging thereon, said detector signal being subject to a signal bias due to the effects of ambient light, detector bias, or the like;
• means mounting one of said source and array in a fixed relationship relative to said object;
• structure for locating the other of said source and array in a fixedly spaced relationship relative to said object and in an orientation for impingement of said beam on said array;
• altering means for selectively altering the intensity of said source-derived electromagnetic radiation impinging on said array between relatively lower and higher intensities whereby each of said detector signal-producing means associated with said detectors produces respective corresponding first and second detector signals;
• digital converting means coupled with said detector signal producing means for receiving said first and second signals and for converting said signals into respective, corresponding, first and second digital signals;
• and
• digital signal processing means coupled with said converting means and including digital memory means for receiving said first and second digital signals and for storing respective first and second data sets representative thereof in said memory means,
• said processing means including means for retrieving and comparing said data sets to one another for producing an output data set representative of the difference therebetween and thereby representative of respective detector signals without said signal bias and for producing an output signal indicative of the location of said beam relative to said array wherein said location is indicative of the position of said object relative to one of said source and array.