Figure 8-16. Optical diagram and optical elements of periscope.

TM 9-258

b. Solid 90ƒ glass prisms can be used instead of

an angle of 90 twice and to displace the line of vision

vertically.

plane mirrors (fig 8-16 to reflect the light through

Figure 8-16. Optical diagram and optical elements of periscope.

when struck by a projectile and not jam or injure the

8-14.

Periscope (Tank Observation).

periscope body. Spare heads are furnished for a

a. The periscope illustrated in figure 8-15 is

replacement. When the periscope is in place, only the

typical of those designed for use as an observation

head projects through the tank.

instrument, to view outside objects from the inside of a

b. The optical system (fig 8-15) consists of two

tank. It has a rectangular body with a removable top or

plane mirrors, two vertical windows, and two horizontal

head and a removable bottom or elbow. The top surface

windows. The mirrors are mounted at 450ƒ angles,

of the head and the bottom surface of the elbow slant at

the same 45ƒ angle. Clamps attached to the head and

parallel to and facing each other. One mirror is mounted

in the head, the other in the elbow. The vertical windows

elbow engage latches operated by eccentric assemblies

are mounted in the front of the head and in the rear of

in the periscope body. They hold the head and elbow

the elbow. The horizontal windows, of thicker glass, are

firmly on the body yet permit ready removal. Plastic

mounted in the bottom of the head and in the top of the

material is used in the construction of the head to permit

elbow.

Gaskets around the edges of the

shatter

into

small

fragments

8-12