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Abstract not available
for SE323706 Abstract of correspondent:
GB1156077
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1,156,077. Automatic
light intensity control. PHILIPS ELECTRONIC &
ASSOCIATED INDUSTRIES Ltd. Nov.3, 1967 [Nov. 8,
1966], No.50105/67. Heading G3R. [Also in Division
H1] A multi-colour cathode-ray tube is manufac-
tured by passing light from a source through a
perforated shadow mask to fix luminescent material
of each colour, a photo-cell responsive to light
from the source controlling the energy supplied to
the source to maintain light intensity constant.
The screen of the tube is moved from one to the
other of a number of operating stations. At each
station a layer of luminescent material of a
differ- ent colour is applied together with a
photo-sensitive lacquer which fixes the material
to form dots where it is exposed to light from a
discharge lamp pass- ing through a suitably
perforated shadow mask which may be that finally
used in the tube. The unfixed material is then
washed off before passing the screen to the next
station at which a further pattern of dots,
displaced from the first and corresponding to a
different colour, is produced. In Fig. 2, the
voltage output of a photo-cell 12 responsive to
light from a HPMV discharge lamp 7 at a typical
station is compared with a reference voltage from
a potentiometer 31 so that any dif- ference is
effective through a transistor amplifier 29 to
operate a motor 30 adjusting the tapping 24 of a
lamp supply transformer 23 in the appropriate
direction to maintain constant light output from
lamp 7. The lamp is switched on by a self-holding
manually-operated push button switch 44 which
remains on until a clock 43 releases a pin 40
after a time suited to the colour. When the
reading of a voltmeter 45 exceeds a predetermined
value, lamp 7 needs replacing. Operation of the
lamp above its rating because of its intermittent
use is referred to. |
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