Method and apparatus for measuring distances

Claim 1

In an apparatus having an extended object of a plurality of discrete structures reproduced by a first objective having a first line of sight and a second objective having a second line of sight for the evaluation of stereoscopic images by the determination of the maximum degree of correlation of a first image reproduced by said first objective and a second image identical with the first reproduced by said second objective, the improvement comprising: (a) a first filter (6) positioned in the first line of sight and a second filter (10) positioned in the second line of sight to filter said images for physical characterization; (b) a first and second means for projecting unidirectionally the filtered images into a plane (5) along an image axis; (c) means provided with at least one specific spatial frequency component and located in said plane along said image axis, said means being adapted for comparing areal structures composed of a plurality of points in said images by optical correlation and generating from said comparison optically discernible signals indicative of the position of said object; (d) a beam splitter located along said image axis projecting said first image in a first direction and said second image in a direction at an angle of 90° to said first direction; (e) first and second photoelectrical means receiving said split images and generating first and second output signals, means for differentiating connected in series with said first photoelectrical means and and receiving said first output signals; (f) circuit means for an additional electrical correlation of said output signals connected to said second photoelectrical means and said means for differentiating; (g) means for indicating connecting to said circuit means; and (h) means for controlling the position of said first means for projecting.