BANDING CORRECTION SYSTEM FOR FILM RECORDING APPARATUS

• US 3,809,806 A
• Filed: 10/18/1972
• Issued: 05/07/1974
• Est. Priority Date: 10/18/1972
• Status: Expired due to Term

• Current Assignee: Robert Walker, William Harris
• Original Assignee: Robert Walker, William Harris
• Inventors: Walker, Robert, Harris, William
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US05/298,607
• Time in Patent Office: 566 Days
• Field of Search: 178/7.6,6.7R,6.7A,DIG.28 350/7,285 346/108
• US Class Current: 347/260
• CPC Class Codes: G02B 26/122 Control of the scanning speed of the polygonal mirror
• CPC Class Codes: G03B 15/00 Special procedures for taking photographs; Apparatus therefor
• CPC Class Codes: G03B 21/43 Driving mechanisms
• CPC Class Codes: G11B 7/0031 using a rotating head, e.g. helicoidal recording
• CPC Class Codes: H04N 1/0473 in subscanning direction, e.g. picture start or line-to-line synchronisation
• CPC Class Codes: H04N 1/0607 Scanning a concave surface, e.g. with internal drum type scanners H04N1/0657 takes precedence
• CPC Class Codes: H04N 1/0635 using oscillating or rotating mirrors
• CPC Class Codes: H04N 1/0664 with sub-scanning by translational movement of the picture-bearing surface
• CPC Class Codes: H04N 2201/02439 Positioning method
• CPC Class Codes: H04N 2201/0471 using dedicated detectors
• CPC Class Codes: H04N 2201/04734 Detecting at frequent intervals, e.g. once per line for sub-scan control
• CPC Class Codes: H04N 2201/04744 by detecting the scanned beam or a reference beam
• CPC Class Codes: H04N 2201/04749 Detecting position relative to a gradient, e.g. using triangular-shaped masks, marks or gratings
• CPC Class Codes: H04N 2201/0476 using an optical, electro-optical or acousto-optical element
• CPC Class Codes: H04N 2201/04793 using stored control or compensation data, e.g. previously measured data
• CPC Class Codes: H04N 2201/04794 Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line
• CPC Class Codes: H04N 5/843 on film

Abstract

The disclosure pertains to an apparatus for recording an image on a film in a scanned horizontal line pattern with a light beam, the scanned pattern being achieved by reflecting the light beam from a moving surface such as an optical spinner. There is disclosed a subsystem for improving the vertical registration of successive lines in the pattern. Means are provided for sensing the beam position at the beginning of a scanline and for developing a position-indicative signal which varies in accordance with the relative vertical position of the beam. The position-indicative signal is compared to a predetermined reference signal which is a function of the desired position of the beam and there is generated a correction signal which depends on the comparison. Further means are provided for vertically deflecting the beam in accordance with the correction signal.

Claims

1. In an apparatus for recording an image on a film in a scanned horizontal line pattern with a modulated light beam, the scanned pattern being achieved using a multi-faceted optical spinner, each facet of the spinner operating to generate an individual horizontal scanline, the film being advanced in a vertical direction over a film bridge that defines a scanning position, said apparatus including a photodetector for monitoring the beam after its passage through the scanning position;

a system for improving the vertical registration of successive lines in the pattern, comprising;

an optical window in said film bridge at the scanning position, said window receiving the beam at the beginning of each horizontal scanline;

means responsive to the output of said photodetector for measuring the time of traversal of said window by said beam and for generating a position-indicative signal as a function of the measured time;

means for comparing said position-indicative signal to a predetermined reference signal which is a function of the desired position of the beam and for generating a correction signal which depends on the comparisons; and

an electro-optical deflection means for deflecting the beam in accordance with the correction signal.

2. In an apparatus for recording an imaGe on a film in a scanned horizontal line pattern with a modulated light beam, the scanned pattern being achieved using a multi-faceted optical spinner controlled by a spinner drive control, each facet of said spinner operating to generate an individual horizontal scanline, the film being advanced in a vertical direction over a film bridge that defines a scanning position, said apparatus including a photodetector for monitoring the beam after its passage through the scanning position;

a system for improving the vertical registration of successive lines in the pattern, comprising;

an optical window in said film bridge at the scanning position, said window receiving the beam at the beginning of each horizontal scanline;

means responsive to the output of said photodetector for measuring the time of traversal of said window by said beam and for generating a position-indicative signal as a function of the measured time;

means for displaying position-indicative signals for a number of successive horizontal scanlines;

programmable means synchronized with said spinner drive control for establishing a plurality of correction signals in accordance with the displayed signals, one correction signal being associated with each spinner facet; and

electro-optical deflection means for vertically deflecting the beam in response to said correction signals.

3. In an apparatus for recording an image on a film in a scanned horizontal line pattern with a light beam, the scanned pattern being achieved by reflecting a light beam from a moving optical means, a system for improving the vertical registration of successive lines in the pattern comprising:

means for sensing the beam position during a scanline and for developing a position-indicative signal which varies in accordance with the relative vertical position of the beam, the beam position sensing means including an optical window in the path of the beam, said window having a horizontal dimension that varies as a predetermined function of vertical position;

means for comparing said position-indicative signal to a predetermined reference signal which is a function of the desired position of the beam and for generating a correction signal which depends on the comparison; and

means for vertically deflecting the beam in accordance with the correction signal.

4. A system as defined by claim 3 wherein said means for vertically deflecting the beam comprises an electro-optic beam deflector which receives the correction signal.

5. A system as defined by claim 3 further comprising means for enabling said beam position sensing means at the beginning of each horizontal scanline.