Chapter 2. FUNCTIONING

TM 11-6720-242-35

CHAPTER 2

FUNCTIONING

2-1. Functioning of Camera

this signal as the cycling rate must be proportion to the

height above the terrain to photograph the entire line of

(fig. 6-10)

flight with a 60-percent overlap. In autocycle mode the

a. General. The function of the camera is to take

cycling rates start above 1 cycle per second and are

panoramic, reconnaissance

photographs from high

continuously variable to 8.5 cycles per second. In the

speed, low flying aircraft. The camera may be mounted

pulse mode the camera operates 1 cycle every 4.5

in an aircraft with the lens positioned to face either

seconds up to 1 cycle per second above which it

vertically downward or in a forward oblique direction at a

automatically switches into the autocycle mode.

20-degree angle of depression. In either mounting, the

d. Photography (fig. 2-14). Pictures are taken by

ground beneath the aircraft is photographed sequentially

rotating the double-dove prism in front of the lens and

from horizon to horizon, with a 60-percent overlap.

by simultaneously advancing the film past the slit

Image motion compensation (imc) is provided to offset

(shutter) in the focal plate. The film advance and the

the blurring effects of the aircraft flight. Correct film

prism rotation are synchronized to paint the image on

exposure is maintained by an automatic exposure

the film as the prism scans a 90-degree angle from

control (aec) circuit.

The operational modes are

horizon to horizon.

autocycle and pulse. The changeover to either mode of

(1) The mirror effect of the prism's

operation is determined by an E V/H voltage (the ratio of

doubledove is an angular displacement which produces

ground speed (V) and altitude (H) to voltage (E))

an optical scan angle of 180 degrees. Before starting a

generated by the aircraft equipment.

90-degree photographic scan the prism rotates through

b. Major Photographic Components (fig. 214).

a 45-degree acceleration angle. Following the 90-

The optical system includes the following components:

degree photographic scan the prism then rotates

(1) A 3 inch, 75mm, f/'2.8 lens assembly.

through a 45-degree deceleration angle. In one cycle

(2) A double-dove prism which rotates in front

the prism and a lift cam both rotate 180 degrees.

of the lens on an axis parallel to the direction of flight.

(2) A continuously rotating rubber covered

(3) A focal plate having an exposure slit

cylinder (puck) advances the film past the slit in the

which is automatically adjusted via the shutter blade, to

focal plate coordinately with the 90-degree scan angle of

vary the slit width.

the prism by the operation of a pressure roller which is

(4) A variable aperture which operates in

actuated by the lift cam which is rotating in synchronism

association with the shutter blade.

with the prism. Immediately following the 45-degree

(5) An automatic exposure control (aec). (A

acceleration rotation of the prism, the pressure roller is

servo system which positions the shutter blade and the

made to press the film into frictional contact with the

aperture.)

puck by the lift cam. Upon completion of the 90-degree

(6) Image motion compensation (imc). (A

scan angle of the prism, the pressure roller is no longer

device which moves the lens back and forth parallel to

actuated by the lift cam and film advance ceases. Film

the exposure slit. The action is limited to vertically

velocity at the focal plate is 19 inches per second at 1

mounted cameras and to the autocycle mode of

cycle per second. The velocity is a product of scan rate

operation).

and focal length. Photography is continuous until the

c. Camera Operation. The autocycle or pulse

end of film is reached, the film breaks, or the equipment

mode of operation is determined by an E V/H signal

is turned off. However, single pictures may be taken

voltage which is generated by the aircraft equipment.

between pulses with the OPERATE switch set to OFF, if

Optical scan rates are derived from

the camera is oper-

2-1