Abstract: An auto-focus camera includes a range finder device having no moving parts. First and second stationary lens devices receive radiation from an object along two spatially separate paths. First and second sensing devices, each comprising a plurality of photo-responsive elements, are arranged to receive the radiation passing through the first and second lens devices, respectively. The first and second sensing devices provide electrical signals representative of the relative position of the intensity distribution of the radiation passing through the second lens device and falling on the second sensing device with respect to the position of the intensity distribution of the radiation passing through the first lens device and falling on the first sensing device. A detecting circuit connected to the first and second sensing devices provides an output signal indicative of that of a plurality of predetermined zones in which the object is located.

Abstract: An optical focus detecting apparatus for an optical system includes a focus scanning and spatial frequency filter comprising a rotating chopper disc. The disc is arranged at an angle with respect to the axis thereof whereby the disc focus position is oscillated back and forth through a predetermined plane, which plane may comprise the film plane of a camera. The disc includes a plurality of transparent and opaque radial sector pairs, the widths of the sectors of any pair being the same and randomly different from the widths of the sectors of adjacent pairs. The sector pairs are so relatively arranged that sector pairs of substantially identical widths are repeated at positions displaced 180.degree. on the disc whereby the modulation of the image optical spectrum is random in nature. The distribution of transparent and opaque sectors is such that the average transmission of light by the disc is 50 percent of the incident light.

Abstract: A system for visually determining the distance to an object includes a lens that is adapted to be sighted upon an object, said lens being divided equally in a first direction with each half covered by polarizing masks arranged at right angles to each other, a flat light transmission analyzer positioned in the vicinity of the focal plane of the lens and dividing the field of view thereof in a second direction displaced 90.degree. with respect to said first direction, each half of the analyzer being covered by polarizing elements arranged at right angles to each other, and calibrated means to indicate the relative position of adjustment of the lens and analyzer when the observed images at the opposite sides of the divided field of view are in coincidence.BACKGROUND OF THE INVENTION1. Field Of The InventionThis invention relates to an improvement in an optical apparatus for visually determining the distance of an object.2.