Patent GB-1131772-A (GB)
Title: Improvements relating to colour film recording and reproducing apparatus
IPC: H04N5/84
Filed: 1967-01-06
Abstract: 1,131,772. Recording colour television signals. COLUMBIA BROADCASTING SYSTEM Inc. 6 Jan., 1967 [6 Jan., 1966; 5 Dec., 1966], No. 989/67. Heading G5R. [Also in Divisions G2 and H4] A picture record intended for use in colour television transmission is in the form of a monochrome representation of a coloured subject, the representation comprising, in a first frame area or a portion of a frame area of the record, a representation of luminance information derived from the subject, and in a second frame area or a second portion of the frame area a representation of chrominance information derived from the subject and recorded in the form of a carrier wave modulated by the chrominance information. The record is formed on a conventional black-and-white kinematograph film and in one embodiment of the invention is arranged as shown in Fig. 1A with the luminance and chrominance representations in adjacent areas of a film frame. The luminance information 12 is in the form of a conventional picture, whilst the chrominance information 13 is in the form of a signal recording brought about by scanning the film in a television type raster and recording a phase and amplitude modulated carrier signal composed in a manner similar to the chrominance signal in the N.T.S.C. colour television system. For the purpose of facilitating the recovery of the chrominance signal from the record, a pilot carrier having a frequency equal to one half that of the chrominance carrier is added to chrominance carrier and recorded with it. The carrier frequency is chosen to be a multiple of the raster line scanning rate so that the recording appears a pattern of dots in each line with the dots in successive lines in alignment so causing the appearance of a line pattern with the line direction extending transversely of the raster line scanning direction. The luminance information may be recorded directly from the original subject by wholly optical means, or may be recorded in a manner similar to the chrominance information by scanning the film in a television raster and recording a conventional picture in response to a luminance signal. Alternative forms of record are described in which: (1) the luminance and chrominance informations are disposed side-by-side (as in Fig. 1A) but brought about by raster scanning with the line direction in the direction of the film length, Fig. 1B (not shown); (2) the luminance and chrominance informations are disposed one above the other in the same film frame with the line direction of scan transverse the film, Fig. 1C (not shown); (3) the luminance and chrominance informations appear in alternate whole frames with scanning synchronizing signals in the gaps between frames, Fig. 8 (not shown). Reference is also made to a record in which the luminance and chrominance information of a picture are disposed in frame portions which are not adjacent. A number of arrangements are described for producing the record. These are described in general terms only with the aid of block diagrams and use known techniques. In each case the original subject is on coloured kinematograph film from which at least the chrominance information is derived by scanning with a television camera. The record is a positive. Where the original is a negative, provision is made to invert the television signals, Fig. 2D (not shown). The chrominance information is translated into I and Q signals in accordance with the N.T.S.C. standards and then modulated in quadrature phase relationship on a carrier wave obtained from a source which also furnishes the pilot carrier of half frequency. In a first arrangement, Fig. 2 (not shown), the luminance information is also derived from the original film by the television camera and the recording is made by two cathode-ray tubes which expose appropriate areas of the film as determined by the form of record required (see above) and which receive respectively the chrominance carrier signal (plus pilot carrier) and a luminance signal. Reference is made to the use of continuous film movement and also intermittent film movement with recording and film advance effected in alternate television scanning fields. In a second arrangement, Figs 2B and 2C (not shown), the luminance information is recorded by direct optical projection from the original, the television camera being used to furnish only the chrominance information. Optical beam-splitting systems are used to divide the light from a frame of the original film into two parts, one for making the luminance recording and the other for exposure to the television camera. A third arrangement, Fig. 6 (not shown), also uses direct luminance recording, but the optical and television recordings are made from and to film frames which are spaced apart. This arrangement can be used to permit the luminance and chrominance information due to a frame of the original to be recorded in areas which are not adjacent. A fourth arrangement, Fig. 3 (not shown), uses direct electron beam recording with the film enclosed within the evacuated chamber of the cathode-ray tube. A two-gun assembly provides two beams for recording the luminance and chrominance informations simultaneously. A modified arrangement, Fig. 4 (not shown), utilizes only a single gun with the two informations being recorded alternately such that, in a sequence of four television fields, luminance is recorded for two (interlaced) fields, chrominance is recorded for the third field and the film is advanced in the fourth field. The electron beam is shifted in position between the luminance and chrominance fields so that the records are made in the appropriate areas on the film. Spot-wobble transverse the raster lines is applied during the chrominance field to mask the line structure. In a modification the scanning speed is increased during the chrominance recording so that two fields are scanned. A fifth arrangement, Fig. 5 (not shown), records with aid of two light beams which originate from lasers, pass through polarization modulators controlled by the luminance and chrominance signals and are scanned over the film by mirror drum assemblies. The records are played back to obtain the picture information by television scanning methods. In a first arrangement, Fig. 7 (not shown), the film is viewed by two cameras, one for the luminance and the other for the chrominance information. A luminance signal becomes available directly, whilst the chrominance carrier is first demodulated in a conventional manner, in response to signals obtained from the pilot carrier, to produce red and blue colour difference signals. These are matrixed to supply a green colour difference signal, and finally a further matrixing of all the colour difference signal and the luminance signal produces colour component signals. In a second arrangement, Figs. 8 and 9 (not shown), the record is scanned by a cathode-ray tube flying- spot scanner in conjunction with two photoelectric cells. The arrangement is intended for use with a record having luminance and chrominance information in alternate frames. A beam-splitter allows two successive frames to be scanned simultaneously whilst a switch changes over the outputs from the two cells at field rate since they produce luminance and chrominance signals alternately. Reference is made to operation with both continuous and intermittent film movements, using either line or reversed, compressed, raster scans.