Tracking and/or guidance systems

Claim 1

A tracking and/or guidance system for defining a course to be followed by a vehicle or projectile aimed towards a target, including a tracking device having an acquisition mode, applicable when the vehicle or projectile is relatively close to the device and in which mode the device exhibits a relatively wide field of view but a relatively low discrimination with regard to deviations of said vehicle or projectile from said course, and means for progressively converting said device from operation in said acquistion made to operation in a tracking mode, in which it exhibits a relatively narrow field of view but a relatively high discrimination with regard to said deviations, as the distance between the vehicle or projectile and the device increases, the said device comprising: a. objective lens means adapted to receive radiant energy, from said vehicle or projectile, b. field lens means arranged to receive radiant energy from said objective lens means and being disposed in the focal plane thereof, c. detecting means having a surface sensitive to said radiant energy and adapted to receive radiant energy from said field lens means, the detecting means being arranged to produce electrical output signals indicative of said deviations, and d. drive means operative on said detecting means and effective i. in said acquisition mode to space said detecting means from said field lens means by a predetermined distance so that said radiant energy received by said surface is diffused over a substantial part of said surface, and ii. in response to, and concomitently with, increasing distance of said vehicle or projectile from said device to progressively reduce the spacing between said detecting means and said field lens means so that said radiant energy is focused with increasing sharpness on said surface as the distance between the vehicle or projectile and said device increases.