Laser etching apparatus for forming photographic images on metallic surfaces

Claim 1

Laser image forming apparatus comprising: a. means for supporting an optical object thereon having light and dark resolution elements, b. an optical detector electrically responsive to the brightness of small surface elements imaged thereon, c. means for imaging single resolution elements of said optical object upon said optical detector to produce electrical signals indicative of the brightness of said elements, d. an optical blank of a material suitable for laser etching, e. an electrically controllable laser for producing a short duration optical pulse of high energy content and capable of a periodic control over an appreciable range of repetition intervals, f. means for optically concentrating the energy in the beam of said laser on said blank to form a tiny pit in said blank for each laser pulse, said pits locally altering the reflectivity of said blank in respect to the unpitted surface, g. means for scanning said detector over the image of said optical object simultaneously with scanning said pulsed laser beam over said optical blank at a uniform rate, said scanning means comprising: 1. a mirror scanned through a solid angle, and wherein 2. said optical object and said optical detector are arranged on a first pair of reciprocally reflective paths in respect to said mirror, and 3. said optical blank and said pulsed laser are arranged on a second pair of reciprocally reflective paths in respect to said mirror, and h. control means responsive to the output of said optical detector for causing the pulsing rate of said laser to vary as a function of object element brightness to create an optical image having light and dark resolution elements on said optical blank representing a similarity transformation of the density of said optical object.