GB1333672A - Image pick-up apparatus - Google Patents

Abstract

1333672 Colour television WESTERN ELECTRIC CO Inc 19 April 1971 [2 Feb 1970 (2)] 20722/71 Heading H4F A colour television camera having one pickup tube 30, Fig. 3, has a pair of filters 11, 15, Fig. 1, placed in front of the tube. The filter 11 has alternate transparent stripes 12 and opaque-tored stripes 13 and the filter 15 has alternate transparent stripes 16 and opaque-to-blue stripes 17, the breadth of the stripes 13 and 17 in the direction of the line scan of the tube being equal. The output signal of the pick-up tube comprises a baseband portion and a chrominance band comprising red and blue signals each modulated on a carrier, the two carriers having the same frequency but due to the relative angular displacement of the filters 11, 15, the sidebands being interleaved, those of the red signal occurring at multiples of the carrier frequency, and those of the blue signal at odd multiples of half the carrier frequency. The resulting signals are passed to filters 31, 32, Fig. 3. The chrominance signal is separated by comb filters 33, 34, the resulting red and blue signals being subtracted from the baseband portion to give the green signal. In an alternative embodiment, Fig. 4, a vertically striped transparent/opaque-to-red filter is used having opaque-to-blue filters 44 superimposed over alternate stripes in each line scan, the opaque-to-blue filters 44 being displaced by one stripe width in adjacent line scans. Alternatively two identically-dimensioned striped filters, one transparent/opaqueto-red and the other transparent opaqueto-blue may be used, tilted by equal and opposite angles to the direction at right angles to the direction of line scan. In this case a third striped filter, transparent/opaque-to-green may be included, the stripes being at right angles to the direction of line scan and the stripe width being equal to the width in the direction of line scan of the stripes of the other two filters. The camera may be used for independent black and white scenes, the light from which are passed through separate filters of alternately high and low transmission, the resulting images being superimposed on the pick-up tube target. The comb filters 33, 34 comprise two subtractors, a one-line delay line, and two delay lines each of which delays the signal applied to it for the time taken to scan along a line the distance from a point on stripe 17 of Fig. 1, to the point vertically above the corresponding point on the next line scan. For the case of three filters the signals due to three succeeding lines in the filed may be used to derive the red, green, and blue signals or with interlaced scanning two succeeding lines in one field may be used with the interlaced line of the preceding or succeeding field.