Abstract

This paper explains how the eight lens elements of a 600 mm, f/2.0 ballistic camera are mounted and retained in almost perfect alignment. The total weight of the glass in this lens is 107 kg, the largest element weighing 21.1 kg. The lens is aligned to less than 3 μ of tangential distortion and the elements are supported in the mount in such a way that they are completely free of any strains. The near perfect alignment of the lens is maintained by soldering the lens elements into the supporting cells.

© 1962 Optical Society of America

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Figures (10)

Fig. 1
Fig. 1

Principal features of the Nortronics 600-mm, f/2.0 ballistic camera.

Fig. 2
Fig. 2

Lens system of 600-mm ballistic camera.

Fig. 3
Fig. 3

The optical axis of any lens element is a line in space which connects the two centers of curvature.

Fig. 4
Fig. 4

Faulty mounting results from two common errors, the decentering and/or tilting of one lens with respect to the other.

Fig. 5
Fig. 5

A holding fixture is mounted on the rotary table. Also included is a dial indicator accurate to within 2.5 μ.

Fig. 6
Fig. 6

The lens element is centered and squared on the fixture and the optical axis is coincident with the rotary axis.

Fig. 7
Fig. 7

A double-convex lens, 38 cm in diameter and weighing 14.5 kg, is photographed with plane-polarized light. The large blurred cross through the center of the lens is normal, but the concentrated dark pattern at the bottom is strain which is caused only by the weight of the element resting on edge.

Fig. 8
Fig. 8

The same element is shown in the same position but mounted in a strain-free mount.

Fig. 9
Fig. 9

Cross section of strain-free mount.

Fig. 10
Fig. 10

Elements are assembled into the main lens cell.

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