Patent GB-1357229-A (GB)
Title: Colour television camera
IPC: H04N9/077
Filed: 1971-10-05
Abstract: 1357229 Colour television camera SONY CORP 5 Oct 1971 [6 Oct 1970] 46320/71 Heading H4F [Also in Dvsion H1] The single image pickup tube 11 of the colour television camera has three sets of electrodes 12, 13 and 14 (see Fig. 2) sequentially arranged in a repeating cyclic order on the photoelectric conversion layer 16 (photoconductive), and alternating signals displaced in time from one another and synchronized with the horizontal scanning period H (such as signals A, B and C in Fig. 3) are supplied to these electrodes via terminals 19, 20 and 21, so that when a colour-separated image is projected on to the tube (e.g. red, green and blue striped filters 23R, 23G, 23B may be included as shown in the face plate between glass plates 22 and 24) a composite colour signal including an index signal is derived from the tube when the layer 16 is scanned by the electron beam. The electrodes and colour filter strips are preferably normal to the tube scanning direction. The signals shown in Fig. 3 that are applied to the electrodes are generated in sources 37-39. The composite colour signal is produced on the common terminal of the secondary windings of transformers 44-46 and fed via capacitor 52, preamplifier 51 and processing amplifier 62 to low pass filter 63 that passes the luminance signal component and band (high) pass filter 64 that passes the colour carrier signal and the index signal which is preferably at the colour subcarrier frequency. The colour carrier signal and index signal are separated by means of two oneline period delays 69 and 71, the colour carrier signal being derived at the output of adder 72 (the index signals from adjacent lines being 120 degrees out of phase and are thus cancelled) and the index signal at the output of adder 78, the signals from 64, 69 and 71 being line sequentially (switch 73) shifted in phase 79 and 81 to bring the three phase displaced index signals into phase with consequential cancellation of the colour carrier signals from 64, 69 and 71. Colour demodulator 83 may derive colour difference signals from the colour carrier, and with the luminance signal produce R, G and B colour signals at outputs 84-86. The construction of the pick-up tube face plate may be modified by including a transparent resistance layer between the glass plate 22 and the electrodes 12, 13, 14 which may be reduced in width and made non-transparent. With this arrangement triangular index signals are derived. The transparent resistance layer may alternatively be on the plate 22 between the electrodes, or over the plate 22 and electrodes. In a further embodiment a mesh-like signal electrode 91, Fig. 8 is provided in addition to the index electrodes 12, 13, 14, the electrodes being separated by an insulating layer 89. In a further embodiment, Fig. 9, the filter strips 23R, 23G and 23B are arranged obliquely relative to the electrodes 12, 13 and 14, and transparent shield electrodes 92 are disposed as shown, an insulating layer being formed between the electrodes, and ground potential being supplied to the shield electrodes via terminal 94. The striped colour filter may not be formed in the pickup tube's face plate but may be separate therefrom and used with or without a lenticular lens. The camera may include a separate luminance pickup tube.