16
pair of negatives and the color overlay.
(3) Microdensitometer measurements and comparisons are possible
for the paired photographs.
(4) Precision positioning is possible for the paired photographs in
X, Y, and 9.
DAVID W. MANN COMPANY.
The David W. Mann Company, Burlington, Massachusetts, USA, has
developed several instruments of note since 1964 including the "Semiautomatic
Stellar Comparator, Type 1205" and the "Mann Comparator, Type 1350. "
a. Semiautomatic Stellar Comparator, Type 1205. The Stellar Compara
tor was originally designed for use in carrying out precise measurements of point
images on photographic plates taken of star fields in connection with passive geo
detic satellite operations. Its capabilities have been extended to permit automatic
setting on preselected points in terrain photography; the positional points are
measured semiautomatically. Steps are being taken to program operations to
allow a computer to automatically preposition and record coordinate values.
Coupling circuits, added to the comparator, feed signals to and from the computer
as required. The characteristics of the comparator are:
(1) The X and Y stage plates are lifted by air bearings to insure maxi
mum stability. The X and Y dial readings are optically relayed to the Operator's
position. Lead screws are mounted in precision bearings and equipped with servo-
drive mechanisms.
(2) The comparator has its own built-in environment--temperature is
maintained at 68° F., humidity at 45%, and dust is filtered.
(3) A projection viewing screen receives information from the film
plane through a system of mirrors with a relatively high magnification.
(4) A photoelectric setting system is capable of automatically scanning
a preselected area, measuring the displacement of the image from the optical center
and converting the displacement to a signal which enables the servomotors to drive
the image to the optical center. An 80-column punch card is activated at this point
with the coordinates and constants being recorded. An oscillograph display verifies
to the operator that the image center is being recorded. The automatic centering
device reduces the corresponding reading time of manual operation by a factor of
at least six and provides results within a one-micron tolerance.
b. The Mann, Type 1350, Large Format Comparator was introduced in
March 1968. It is advertised as the largest format comparator--it provides con
tinuous measurement of photographic film and reduces coordinate data to digitized
readout. A joystick control provides for continuously variable slew speeds of the
X and Y motions. Rolls of film can be handled--an air cushion supports the film
within the field of view area. A binocular microscope viewing system and an
