| 摘要 |
1357048 Television FERRANTI Ltd 27 Feb 1973 [29 Feb 1972] 9420/72 Heading H4F In a system for superimposing the image of a model ship viewed by a television camera on an electronically generated horizon for use for example in a simulator, provision is made for moving the displayed ship image if it is detected as not being in the correct vertical position, e.g. if it is superimposed on the sky. The detection is carried out by determining whether that line of the video signal from the camera viewing the ship model which corresponds to the horizon contains any information, no information in this line being taken as indicating that the ship image is too high, and a counter then being incremented to move the displayed ship image one line width lower, and the process repeated in the following frame. The input to a NOR gate G10 is "0" except during the line period corresponding to the generated horizon when a "1" pulse is generated either directly by the circuitry producing the horizon or by a comparator EG receiving signals from a counter LC counting horizontal pulses LD, and a signal DD representing the position of the horizon. The input pulse to gate G10 is inverted by this gate and passed to NOR gate G11, and is also passed to a one-line delay line D and to a set input of a bi-stable circuit B which produces a "0" output when set. An inverted form of the video signal from the camera viewing the ship model OL is applied to NOR gate G11 and if during the "horizon" line it contains information, signal OL will be "0" for part of this line, thus producing a "1" output from gate G11 to reset bi-stable circuit B to produce a "1" output thus blocking NOR gate G14, and the vertical position of the displayed ship image is unaltered, being determined by a signal AEC1 which is passed via amplifiers A1 and A2. If during the "horizon" line the video signal from the camera viewing the ship model contains no information the signal OL is always "1", gate G11 provides no output and bi-stable circuit B is not reset until the end of the frame when it is reset by the frame synchronizing pulse FD which has been inverted in a NOR gate G12. Thus for the remainder of the frame the output of bi-stable circuit B is "0" and during the line following the "horizon" line the output of delay line D is "1" and thus the output of NOR gate G15 is "0" and the output of NOR gate G14 is "1". This causes the count in a counter CC to be incremented by one, and this count is subtracted from signal AEC1 to produce signal AEC2 and move the ship image vertically downwards by one line width. This process is repeated in the following frames. When the correction provided by counter CC is no longer required this counter is reset by a reset signal R. The correction system may be inhibited by application of a "0" inhibit signal INH to NOR gate G13 to maintain bi-stable circuit B in a permanently reset condition, thus blocking NOR gate G14. The system may be modified to produce upwards correction instead of or as well as downwards correction. |
