PHOTOGRAPHIC DODGING APPARATUS

• US 3,610,724 A
• Filed: 06/19/1969
• Issued: 10/05/1971
• Est. Priority Date: 06/19/1969
• Status: Expired due to Term

• Current Assignee: William F. Frizzell
• Original Assignee: William F. Frizzell
• Inventors: Frizzell, William F.
• Primary Examiner(s): Matthews, Samuel S.
• Assistant Examiner(s): Sheer, Richard M.
• Application Number:
  US04/834,634
• Time in Patent Office: 838 Days
• Field of Search: 355/80,81,67,68
• US Class Current: 355/80
• CPC Class Codes: G03B 27/725 Optical projection devices wherein the contrast is controlled electrically (e.g. cathode ray tube masking)

Abstract

A light beam of constant intensity is directed against a mirror galvanometer and the reflected through a photographic negative or positive against photosensitive printing material to expose the printing material. A photomultiplier is positioned in the path of the light to which the printing material is exposed. In response to the sensed light the galvanometer is actuated to move the mirror at a speed responsive to variation of density in the negative or positive so that the light beam will continuously scan across an elemental area of the negative or positive but at a varying speed. After each scan of the light beam in one direction a mechanical structure moves incrementally the galvanometer and light source in a direction perpendicular to the scanning movement of the light beam so that the next scan will be adjacent the previous scan. In this manner all elemental areas of the negative or positive will be exposed.

Claims

1. In a photographic printing apparatus, the combination of means for producing a constant intensity light beam, means in the optical path of said light beam for supporting a photographic negative or positive and printing material, photoelectric sensing means in the path of the light to which the printing material is exposed, mirror galvanometer means for scanning said light beam across an elemental area of said negative or positive, means responsive to said photoelectric sensing means for varying the speed of said light beam scanning means according to the density of the photographic positive or negative, a movable carriage upon which said mirror galvanometer and light beam producing means are mounted, and means drivingly connected to said carriage to move said carriage incrementally in a direction perpendicular to the scanning movement.

2. In an apparatus as claimed in claim 1 wherein said light beam moves continuously during each scan but at varying speeds.

3. In an apparatus as claimed in claim 1 wherein said means for moving said scanning means is responsive to said photoelectric sensing means.

4. In an apparatus as claimed in claim 1 wherein said negative or positive is a sheet retained on said supporting means.

5. In an apparatus as claimed in claim 1 wherein said negative or positive is a strip moved continuously upon said supporting means in a direction perpendicular to the scanning movement.

6. In an apparatus as claimed in claim 1 wherein said incremental distance is the width of the elemental area exposed to the light beam.

7. In a photographic printing apparatus, the combination of means for producing a constant intensity light beam, means in the optical path of said light beam for supporting a photographic negative or positive and printing material, photoelectric sensing means in the path of the light to which the printing material is exPosed, mirror galvanometer means for scanning said light beam across an elemental area of said negative or positive, means responsive to said photoelectric sensing means for varying the speed of said light beam scanning means a according to the density of the photographic positive or negative, said light beam producing means comprises a constant intensity light source and a fiber optic bundle to direct light onto said mirror galvanometer means whereby a light beam is reflected therefrom.