Patent GB-1160232-A (GB)
Title: Color Video Signal Generating Device
Inventor: TAKAGI TOSHIHIKO
IPC: H04N9/083
Filed: 1966-07-29
Abstract: 1,160,232. Colour television. NIPPON COLUMBIA K.K. 29 July, 1966, No. 34228/66. Heading H4F. The image of a coloured object 101, Fig. 1, recorded on a monochrome film 105 via striped colour filter 103 is converted into electrical signals by means of a photo-electric converter, e.g. a monochrome pick-up tube 50, Fig. 3, from which are derived colour video signals for transmission. Optical filter 103 comprises filter elements 103a and 103b having strip filter elements W and - R or - B respectively arranged alternately and crossing the horizontal scanning direction h of the photo-electric converter, Fig. 2 (not shown). The strip filter elements W, - R and - B are transparent, intercept red light and intercept blue light respectively and the "pitch" of the filter elements, i.e. the width of adjacent strip filter elements W are - R, and, W and- B are such that the photo-electric converter produces video signals having carrier frequencies f R  and f B  in addition to a non- carrier signal. These signals are separated by means of low pass filter 52, Fig. 3, and band pass filters 53 and 54 having centre frequencies f R  and f B  respectively. The characteristics of which are shown in Fig. 4. The outputs of filters 53 and 54 are demodulated in detectors 56 and 57 and the three primary colour video signals are obtained from matrix 55. Dur to cross modulation a beat frequency component appears in the output of low-pass filter 52 which is cancelled by means of a beat frequency generator 59. To increase the resolution obtained the upper limit frequency of the band of filter 52 may be raised to the centre frequency f R  of filter 53, Fig. 5 (not shown), however as a result of this a component of filter 53 gets mixed in the output of filter 52 and a stripe pattern due to f R  appears in the reproduced picture. The effect of this stripe pattern may be reduced by applying a rectangular current, Fig. 7B (not shown), derived from the vertical synchronizing signal circuit, to the horizontal deflection coil of the pick-up tube, thus causing the picture of one field to shift in a horizontal direction, and the amplitude of this rectangular current is determined so that the stripe patterns in adjacent fields are interleaved. The rectangular current may be derived from the horizontal synchronizing signal circuit and have a period corresponding to the horizontal deflection period, its phase being inverted every vertical deflection period. Instead of applying the rectangular currents to the horizontal deflection coils they may be applied to another coil provided around the pick-up tube or to a reproducing device. Deviations in the frequencies f R  and f B  which would result in distortion of the reproduced picture and deterioration of picture quality are reduced by applying the output of either one of filters 53 and 54 to a frequency discriminator (89), Fig. 9 (not shown), the output of which is fed to the horizontal deflection coil. Alternately the output of discriminator (89) may be fed to filter 53 and/or filter 54 to adjust a variable element, e.g. an inductance or capacitor, therein, to move their centre frequencies, Fig. 10 (not shown). In addition, the band of filter 52 may be made variable. To change the bandwidths and centre frequencies of the carriers the pitch of the optical filters is changed by adjusting the orientation of the optical filters, Fig. 12 (not shown). The low-pass filter 52 in Fig. 3 may be replaced by an adding circuit (52<SP>1</SP>, Fig. 13, not shown), and the outputs of band-pass filters (53) and (54) are applied thereto with the correct polarities so as to cancel these outputs from the output of the pick-up tube. With this arrangement further frequency components exceeding the pass-bands of filters (53) and (54) may be obtained so that the resolution may be enhanced. A colour filter 106<SP>1</SP>, Fig. 1, may be located in the light path between the object and the optical filter. Film 105 may be located in direct contact with optical filter 103, or optical fibres may be used, relay lens 104 being omitted.