Patent GB-1247063-A (GB)
Title: Colour video signal generating apparatus
IPC: H04N9/083
Filed: 1969-02-05
Abstract: 1,247,063. Colour television. SONY CORP. 5 Feb., 1969 [5 Feb., 1968], No. 6214/69. Heading H4F. In a colour video signal generating apparatus a colour filter 7 having different areas responsive to different colours, e.g. magenta (M), cyan (C) and yellow (Y), is interposed between the subject of transmission and the photoconductive plate 3 of the vidicon pick-up tube 4 such that an image of the subject composed of colour strips is projected on to plate 3 said colour strips being arranged to be at an angle to the direction of scanning, and the horizontal scanning lines being caused to change position in the vertical direction every other horizontal line. This latter aspect is illustrated in Fig. 4 wherein Fig. 4A shows the strip images 10 of the subject being scanned by normal interlaced scanning; first field in solid lines, second field in broken lines. Fig. 4B shows the modified form of scanning according to a first embodiment of the invention in which, the evennumbered scanning lines of each odd, eg. first, field are shifted vertically upwards half a horizontal line pitch and the odd-numbered scanning lines of each even, e.g. the second, field are shifted vertically downwards by the same amount. This vertical deflection is achieved by means of a micro-deflection coil 16 which operates in conjunction with the raster deflecting coils 6, both coils 6 and 16 being fed from a signal generator 13. With such a scanning arrangement each pair of closely spaced scanning lines, e.g. lines 1 and 2 in the first (odd) field, may partially overlap in which case the amplitude of the video output signal during the second line scan will be reduced and this is compensated by applying the first and second line scan video signals to respective parallelconnected gain-controlled amplifiers 22a, 22b via respective gates 21a, 21b controlled by the generator 13. Fig. 7 illustrates the reproduced pattern, using normal interlaced scanning, when the scanning at the camera is normal (Fig. 7A) and when the scanning at the camera is as in Fig. 4B (Fig. 7B) and wherein the circles and crosses represent the bright spots of the first and second fields respectively. Hence, using scanning at the camera according to this invention, the strip image 10, when reproduced, is is displaced laterally on certain lines and hence the strips are not noticeable in the reproduced picture (see Fig. 7B). A second embodiment described with reference to Fig. 8 (not shown) uses interlaced scanning with a four-field cycle in which the even-numbered scanning lines of the first and second fields are displaced upwards half a pitch and the odd-numbered scanning lines of the third and fourth fields are similarly displaced upwards, the resultant semi-random distribution of bright spots or the displayed image being illustrated in Fig. 10 (not shown). In order to derive three separate colour signals from an image of the subject of transmission 1 using a single pick-up tube, the colours are caused to have different repetition frequencies when scanned so that they may be split up using band-pass filters 23G, 23R and 23B to give respective colour signals corresponding to the complements green (G), red (R) and blue (B) of the filter colours M, C, Y. This is achieved by altering the number of strip images of each colour projected on plate 3 by incorporating a lens 8 having, on one face, convex cylindrical portions 8a and flat portions 8b. Hence, if filter 7 is itself in the form of colour strips the number of images of each colour strip projected on to 3 may be altered by changing the spacing of the strips of filter 7 (see Figs. 2 and 3, not shown). As a result of this, the frequency of occurence of the colours when scanned may be arranged to be different for each colour.