Polaroid ProCam Repair Manual page 16

ProCam focussing borrows from methods used in earlier Polaroid cameras.
However, it goes well beyond matching lenses and is a unique technological
achievement in camera optics. At the heart of the ProCam focus operation is the
Quintic aspheric lens system. Figure 1-6 shows the difference between spherical
and aspherical lenses.
EXAMPLES OF
SPHERICAL LENSES
Figure 1-6. Comparison of Spherical and Aspherical lenses
To understand how the ProCam lenses work, you should first know about the
characteristics of aspheric lenses. Figure 1-7 shows in simplified form the
relationship between two aspheric lenses. In this representation you can see that
by changing the position of the two lenses relative to each other, this theoretical
lens system could focus on subjects between the extremes of two feet and infinity.
CONCAVE LENS
IN FOCUS AT 2 FEET
Figure 1-7. Interaction of Aspheric Lenses
EXAMPLE OF
ASPHERIC LENS
(UNEVEN SURFACE)
CONVEX LENS
IN FOCUS AT INFINITY
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