STEREO PROJECTION 1 95
It is often found that a shutter is running backward. That is it is
in synchronism, but the wrong phases are matched. Then there is
the inconvenience of looking through a hand held instrument. All
in all the polarized light technique has been adopted because with
all factors considered it is the easiest, the most comfortable and the
most fool-proof of them all.SS’Fig. 12-10. Double prism viewer with prisms PI and P2 adjustable.It may be added as a matter of interest that this principle of
stereo projection using polarized light for picture extinction was
patented before igoo! It is not quite as modern as many people
think. It was the development of polarizing films in stable quality
and commercial quantity which made this form of projection
really practical. Artificial polarizing films have been known for a
century, but Polaroid was the first which could be produced in
unlimited quantities while maintaining a satisfactory degree of
uniformity.
And now one final word about the projector of the future. Very
often you will hear some remark like this, “Oh, I am going to
wait until they improve stereo projection. It is now in the experi-
mental stage and has a long way to go!” Don’t you believe it. Of
course it would be silly to say that there will be no improvements,
but what kind of improvements will they be?
The automobile to-day is basically like that of ten, 20, 30 years
ago. It has a different body, it has push button windows, over-
drive, automatic transmission and lots of other gadgets, but bas-
ically the working parts are of the original fundamental design.
And it is also more than a possibility that some time in the future
the internal combustion engine will be replaced by an atomic
motor, but that is far in the future.