Abstract

A search for a universal-focus lens has led to a new class of optical elements. These are called axicons. There are many different kinds of axicons but probably the most important one is a glass cone. It may be either transmitting or reflecting. Axicons form a continuous straight line of images from small sources.

One application is in a telescope. The usual spherical objective is replaced by a cone. This axicon telescope is in focus for targets from a foot or so to infinity without the necessity of moving any parts. It can be used to view simultaneously two or more small sources placed along the line of sight.

If a source of light is suitably added to the telescope it becomes an autocollimator. Like ordinary autocollimators it can be used to determine the perpendicularity of a mirror. In addition, it can simultaneously act as a telescope for a point target which may be an illuminated pinhole in the mirror.

The axicon autocollimator is also a projector which projects a straight line of images into space.

© 1954 Optical Society of America

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Figures (12)

F. 1
F. 1

Ray diagram showing formation of images of a point source by diffraction through a narrow circular opening.

F. 2
F. 2

Ray diagram showing formation of images of a point source by refraction through a circular ring or toric lens.

F. 3
F. 3

Ray diagram showing how one element of an axicon produces a strip of light on a screen.

F. 4
F. 4

Upper left— photograph of a screen showing strip of light from one element of an axicon. Upper right— a similar photograph showing crossed strips from four elements. Lower left—showing crossed strips from many elements. Lower right—a photograph of an axicon image using complete axicon.

F. 5
F. 5

Ray diagram showing how a strong toric lens forms a small virtual ring image S′, and a real axicon image at P of a source S.

F. 6
F. 6

Ray diagram showing how a weak toric lens forms a larger virtual ring image S′, and a real image at P of source S.

F. 7
F. 7

Ray diagram showing how a cone forms a virtual ring image S′ in the plane of the source S, and an axicon image at P.

F. 8
F. 8

Various forms of reflecting axicons. Upper left—a hollow reflecting cylinder. Upper right—a hollow reflecting cone. Lower left—a hollow flared reflector. Lower right—a hollow sphere of refracting material.

F. 9
F. 9

(A) Ray diagram of a spherical lens plus positive cone forming a real ring image S′ beyond an image point P. (B) Ray diagram of a spherical lens plus negative cone forming a real ring image S′ in front of an image point P.

F. 10
F. 10

(a) Ray diagram of combination of cone and spherical lens forming an axicon image at an ocular. (b) Ray diagram showing replacement of lens with another cone to form axicon image at ocular.

F. 11
F. 11

Diagram showing two cones of equal angle forming 1–1 image of source.

F. 12
F. 12

Ray diagram of reflecting cone to show how an axicon image is returned to the source wherever the source is located along the axis of the cone out to a maximum distance.