METHOD AND APPARATUS FOR SELF-CORRECTING, DIRECT SENSING COINCIDENCE SENSOR FOR OPTICAL RANGEFINDERS

A device to precisely determine the angle of parallax formed by a target object of interest and first and second entrances (30, 30') for the purpose of rangefinding for example. The device having photodetectors (46) for sensing the separation of first and second channel target scene images (68, 68') and for sensing the separation of first and second channel reference marker images (66, 66') and having electronic circuitry (76) and processor (78), wherein by comparison of these separations, may calculate an accurate angle of parallax of the target object of interest and provide the resultant information to the user via a display (80). The device includes a spatial referencing system (14) and therein, the device may automatically account for small misalignments of optical elements which may occur during normal use and in certain embodiments of the device may allow the user to isolate the target object of interest from other objects which may appear in the field of view. In certain embodiments, the device also has an optical switchable beamsplitter (70) which permits the user to see single unobstructed images of the target object of interest in a non-beamsplitting observation mode, or dual or split images of the target object of interest in a beamsplitting ranging mode. This optical switchable beamsplitter (70) also permits simultaneous sampling of the separate first and second channel target scene images (68, 68') on separate photodetectors (46) while in a non-beamsplitting mode, and also allows a method for referencing the relative positions of the separate photodetectors (46) while in a beamsplitting mode.