(57) This invention relates to the detection of a change in a pattern of radiation and
is concerned especially with the detection of such a change as a result of the movement
of an object and/or its shadow and/or an image of an object, such as, for example,
a television picture thereof. The term «radiation» is used to include ultra-violet
radiation, visible light and infrared radiation.
In more detail there is provided an apparatus for detecting a change in a pattern
of radiation incident on the apparatus, comprising lens means, a first sensing means
sensitive to said incident radiation and adapted to give a first outpout signal characteristic
of said pattern and a second such sensing means, adapted to give a cecond such output
signal, said sensing means having different configurations and/or orientations of
radiation-sensitive areas and said lens means together with said sensing means constituting
an optical system, are arranged for incidence on said sensing means through said lens
means of said radiation, and connected to comparator means in such a way that the
latter receives said output signals, the arrangement being such that any change in
said pattern of radiation causes a first consequent change in said first output signal
and a second consequent change being different from said first consequent change by
virtue of said different configurations and/or orientations of radiation-sensitive
areas, and said comparator means being arranged to supply a signal which is a function
of the said differing output signals and hence indicative of a change in said pattern
of radiation.
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