Patent GB-1516764-A (GB)
Title: Solid state colour television cameras
IPC: H04N9/04
Filed: 1976-02-09
Abstract: 1516764 Television SONY CORP 9 Feb 1976 [14 Feb 1975] 04971/76 Heading H4F A solid state colour television camera which is designed to provide an output signal free of "folded error" (i.e. disturbance owing to frequency overlapping DC and sideband signal components), comprises a charge-coupled device (CCD) 10, Fig. 5, onto which an image of an object 11 is focused by a lens L and from which image information is adapted to be read out line by line in sequence, and a colour filter 20 disposed between the lens and the CCD, said filter passing such light therethrough that the image information includes a colour coded signal component only at every other line. The CCD consists of a photo-sensitive array 10A, Fig. 2, having a plurality of picture elements 1 l-l ,... 1 m-n  which are aligned in the horizontal and vertical directions, each said element including three photo-sensitive units 2, and a temporary storage array 10B from which charge is transferred line by line into a shift register 10C for subsequent read out of the video signal. The filter, Fig.3, is a type of transverse stripes extending in the horizontal scanning direction. Those stripes at 1F o , 3F o ... of the filter corresponding to the CCD picture elements 1 1-1 , 1 1-2 ,... 1 1-n , 1 3-1 ... 1 3-n ,... aligned on the odd number horizontal scanning lines (or alternatively on the even lines) are divided into two regions with respect to the vertical direction, and the areas of the filter corresponding to the upper parts (or alternatively the lower parts) of the divided regions, are selected to pass therethrough different primary light colours as shown in Fig. 3. The remaining regions of the filter pass therethrough white light W. The filter of Fig. 3 is of a configuration especially adapted for use in interlaced scanning. If an output signal obtained at the odd number scanning line in the odd field is taken at S o . Fig. 6A, and that obtained at the even number horizontal scanning line taken as S E , Fig. 6A', only the signal S O  contains colour coded components owing to the construction of the filter 20. The colour coded components are thus obtained at every other horizontal scanning period while the luminance information is obtained at every horizontal scanning line during the odd field F O , and similarly during the even field F E . The video signal appearing at the output 4, Fig. 5, of the CCD is supplied to a level switching circuit 12 including an amplifier 12A for amplifying the signal obtained during each odd scanning line S O  to correspond to the signal level obtained in even lines S E . The signals S O , S E , which are obtained alternately from circuit 12, are supplied to a low pass filter 13 and thence to a subtracter 14 which is also supplied with the signals S O , S E  which are not limited in band. Subtracted outputs Sa from subtracter 14 consist of only the high band components shown in Figs. 6C, 6C<SP>1</SP>. A compensating delay 15 is provided between circuit 12 and subtracter 14. The pass band of filter 13 is selected that no "folded error" is contained in the signals S LO , S LE , Figs. 6B, 6B', passed therethrough. Signal Sa is supplied to an adder 16, which is also supplied with signals S LO , S LE , via a circuit which prevents that part of signal Sa which contains colour components, i.e. every other line thereof, being supplied to said adder. To this end, signal Sa is delayed through a circuit 17 by 1H to provide a signal Sa<SP>1</SP>, and signal Sa<SP>1</SP> is supplied to adder 16 together with signal Sa, which is not delayed, through a switch SW 2  which is switched at every 1H. Switch SW 2  is changed to contact E when an even line is scanned and to contact O when an odd line is scanned. Therefore, when switch SW 2  contacts the contact O, the signal Sa, shown in Fig. 6C' and the low band component S LO , Fig. 6B are applied to adder 16, and the output from a low pass filter 18 is thus the DC component only. When switch SW 2  contacts the contact E, the DC component consists of components S LE +S HE . Therefore, no "folded" component of the colour component is mixed into the DC components. If the non-delayed signal Sa and the delayed signal Sa<SP>1</SP> are applied to a subtractor 19, the DC components in the same phase are cancelled and only the colour components are derived therefrom. A matrix circuit 23, which is supplied with the DC and the colour components, produces the luminance signal Y and colour difference signals B-Y and R-Y of the NTSC system. In modifications, the CCD may be of the frame transfer type or of the interlaced shift type. Alternative forms of filter are described with reference to Figs. 8 and 10 (not shown).