Short range optical rangefinder

A short range optical rangefinder comprising:

• transmitting means for transmitting directional optical energy;
• receiving means closely adjacent to said transmitting means and disposed to provide a directional field of view for receiving directional reflected radiation of said optical energy and for providing an output signal in response thereto;
• said transmitting means being disposed for directing said radiation into the field of view of said receiving means for establishing a signal window region in close proximity to said transmitting and receiving means where the field of view and the transmitted radiation are coincident, said window having a plane therethrough at a predetermined spatial distance from said transmitting means and said receiving means for establishing a desired standoff distance from said transmitting means and said receiving means, said output signal being an output pulse indicative of passage of an object into said window and through said plane;
• and wherein said receiving means comprises a sensor for receiving optical energy and providing a variable electrical signal output responsive to variations in optical signal amplitude, a synchronous detector responsive to said variable electrical signal output for providing a direct current level output indicative of said variations in signal amplitude of said detected optical energy, and first and second signal detection circuits having inputs coupled in parallel to the output of said synchronous detector;
• said first signal detection circuit being a comparator for providing an output signal after a predetermined input signal level is received, and said second signal detection circuit providing an output signal when a peak in input signal level occurs;
• and wherein said transmitting means comprises a clock for providing a high frequency square wave output, light emitting means, and a driving means responsive to the output of said clock for stimulating said light emitting means to emission, said square wave output from said clock being further coupled to said receiving means synchronous detector for generating said detector's direct current output level which follows the amplitude of said reflected radiation.