METHOD AND APPARATUS FOR REPLACING A PART OF A FIRST TELEVISION IMAGE BY A PART OF A SECOND TELEVISION IMAGE

摘要

1388288 Television OFFICE DE RADIO-DIFFUSION-TELEVISION FRANCAISE 26 June 1972 [25 June 1971] 29816/72 Heading H4F In a superposition television system an object, e.g. a person-to be made to appear in the television display to be aginst a false background scene, is sited against a background having a brightness range of non-zero width. When extended to a red (R), green (V) blue (B) colour television system, the background range of colour is defined as anywhere within a parallelepiped P1, Fig. 2 in a cartesian co-ordinated colorimetric system. The object must necessarily have no colorimetric value within volume P1. The object scene is televised to give a signal, e.g. red signal VR, Fig. 3, which is passed to two level comparators 2, 3, Fig. 4 respectively, detecting the lower level VR1 cross over points and giving a binary signal MR output and the upper level VR2 cross over points and giving a binary signal NR output. NAND logic 4, 5 gives the switching signal M R .# R for combination with further switching signals at logic 6 to give a first control signal for changing from the background signal A to the object signal B.