US 4,400,764 A · Low backscatter illumination system

Abstract

Methods and apparatus are disclosed for shaping illuminating beams from continuous duty searchlights or the like so as to minimize the effect of backscattered illumination and, to thereby increase the brightness contrast between illuminated target objects and background so as to improve visibility. More specifically, a continuous duty illumination system comprising an optical system in which the distribution of the light beam entering the entrance pupil of the optical system comprises a collimated beam of high radiant intensity which is thereafter split along an axis bisecting the distributional pattern, or image, with light from the respective halves of the distribution image being directed first in opposite directions and then being redirected in substantially parallel directions; and, wherein light from each half of the split distribution is imaged into respective ones of a pair of collimating lenses with each lens receiving light only from the upper half of its focal plane so that the parallel beams leaving the exit pupils of the optical system contain light only in the space below a generally horizontal plane passing through and containing the optical axes of the system.

Claims39

Dependent claims

(a) forming a collimated light beam;
(b) projecting the collimated light beam through an aperture comprising the entrance pupil of the optical system;
(c) imaging the collimated light beam at the apex of the image splitting reflecting prism with the axis of the beam being coincident with the prism apex so as to split the distribution image of the beam into first and second generally equal halves directed in generally opposite directions by reflection from the prism and with the respective halves of the distribution image being disposed in the upper halves of the focal planes of respective ones of first and second collimating lenses;
(d) collimating and inverting the respective halves of the distribution image by directing the light in the upper halves of the focal planes of the first and second collimating lenses through the lenses and towards respective ones of the first and second exit pupils of the optical system;
and,
(e) directing the collimated beams exiting from the first and second exit pupils along generally parallel optical axes to form an illuminating beam having a broad forward aspect and essentially devoid of light in the space above a generally horizontal plane passing through the optical axes of the system.

3 more elements

The method of forming an illuminating beam characterized by the absence of light in the space above a horizontal plane containing the optical axes of an optical system of the type having first and second entrance pupils, first and second exit pupils generally located on parallel optical axes and operatively associated with the first entrance pupil, third and fourth exit pupils generally located on parallel optical axes and operatively associated with the second entrance pupil, first and second image splitting reflecting prisms, and a series of imaging and collimating lenses, comprising the steps of:

(a) forming first and second collimated light beams;
(b) projecting the first and second collimated light beams through respective different ones of first and second apertures comprising the first and second entrance pupils of the optical system;
(c) imaging the first and second collimated light beams at the respective apexes of the first and second image splitting reflecting prisms with the axis of each beam being coincident with the respective prism apex so as to split the distribution image of each of the first and second beams into first and second generally equal halves directed in generally opposite directions by reflection from the respective ones of the first and second prisms and with the respective halves of the distribution images being disposed in the upper halves of the focal planes of respective ones of first and second collimating lenses associated with the first reflecting prism and in the upper halves of the focal planes of respective ones of the third and fourth collimating lenses associated with the second reflecting prism;
(d) collimating and inverting the respective halves of the distribution image formed by the first prism by directing the light in the upper halves of the focal planes of the first and second collimating lenses through the lenses and towards respective ones of the first and second exit pupils of the optical system;
(e) collimating and inverting the respective halves of the distribution image formed by the second prism by directing the light in the upper halves of the focal planes of the third and fourth collimating lenses through the lenses and towards respective ones of the third and fourth exit pupils of the optical system;
and,
(f) directing the collimated beams exiting from the first, second, third and fourth exit pupils along generally parallel optical axes to form an illuminating beam having a broad forward aspect and essentially devoid of light in the space above a generally horizontal plane passing through the optical axes of the system.

4 more elements

The method of forming an illuminating beam characterized by the absence of light in the space above a horizontal plane containing the optical axes of an optical system of the type having an entrance pupil, first and second exit pupils generally located on parallel optical axes, an image splitting reflecting prism having its apex facing downwardly and oriented in a direction parallel to the optical axes of the illumination system, and a series of imaging and collimating lenses, comprising the steps of:

(a) forming a collimated light beam;
(b) projecting the collimated light beam in a horizontal direction through an aperture comprising the entrance pupil of the optical system;
(c) reflecting the collimated light beam in a vertical direction towards the apex of the image splitting reflecting prism;
(d) imaging the collimated light beam at the downwardly facing apex of the image splitting reflecting prism with the axis of the beam being coincident with the prism apex so as to split the distribution image of the beam into first and second generally equal halves directed in generally opposite horizontal directions by reflection from the prism and with the respective halves of the distribution image being disposed in the upper halves of the focal planes of respective ones of first and second collimating lenses;
(e) collimating and inverting the respective halves of the distribution image by directing the light in the upper halves of the focal planes of the first and second collimating lenses through the lenses and towards respective ones of the first and second exit pupils of the optical system;
and,
(f) directing the collimated beams exiting from the first and second exit pupils along axes generally parallel to one another and to the apex of said image splitting reflective prism to form an illuminating beam having a broad forward aspect and essentially devoid of light in the space above a generally horizontal plane passing through the optical axes of the system.

4 more elements

A continuous duty low backscatter illuminator comprising, in combination:

(a) an optical system having (i) an entrance pupil and (ii), first and second exit pupils disposed on generally parallel optical axes;
(b) means for forming a collimated light beam of relatively high radiant intensity and for directing the collimated beam thus formed through said entrance pupil of said optical system;
(c) an image splitting reflecting prism mounted in said illuminator;
(d) means for imaging the distribution image formed by the collimated light beam at said entrance pupil at the apex of said reflecting prism so as to split the distribution image along a line bisecting the axis thereof to form first and second halves of the distribution image which are respectively reflected in generally opposite directions by said reflecting prism;
(e) first and second means for collimating respective ones of the first and second halves of the distribution image formed at the apex of said prism, said first and second collimating means being mounted in said illuminator relative to said reflecting prism so as to receive light only in the upper halves of their respective focal planes so that upon collimation of the light in the first and second halves of the distribution image output beams are formed at each of said first and second exit pupils characterized by the absence of light in the space above a horizontal plane passing through the optical axes of said optical system;
and,
(f) means for imaging the first and second halves of the distribution image at respective ones of said first and second exit pupils so as to form a pair of generally parallel beams of light which overlap in the far field so as to define an illumination beam having a broad forward aspect and essentially devoid of light in the space above a horizontal plane passing through the generally parallel axes of said optical system.

4 more elements

A continuous duty low backscatter illuminator comprising, in combination:

(a) an optical system having (i) an entrance pupil and (ii), first and second exit pupils disposed on parallel generally horizontal optical axes;
(b) means for forming a collimated light beam of relatively high radiant intensity and for directing the collimated beam thus formed in a horizontal direction through said entrance pupil of said optical system;
(c) an image splitting reflecting prism mounted in said illuminator with its apex facing downwardly and disposed in a vertical plane parallel to the optical axes of said system,
(d) means for reflecting the collimated beam vertically upward towards the downwardly facing apex of said prism and with the axis of the beam intersecting said apex;
(e) means for imaging the distribution image formed by the collimated light beam at said entrance pupil at the downwardly facing apex of said reflecting prism so as to split the distribution image along a line bisecting the axis thereof to form first and second halves of the distribution image which are respectively reflected in generally opposite horizontal directions by said reflecting prism;
(f) first and second means for collimating respective ones of the first and second halves of the distribution image formed at the apex of said prism, said first and second collimating means being mounted in said illuminator relative to said reflecting prism so as to receive light only in the upper halves of their respective focal planes so that upon collimation of the light in the first and second halves of the distribution image output beams are formed at each of said first and second exit pupils characterized by the absence of light in the space above a horizontal plane passing through the optical axes of said optical system;
and,
(g) means for imaging the first and second halves of the distribution image at respective ones of said first and second exit pupils so as to form a pair of generally horizontal beams of light parallel to one another and to a vertical plane passing through the apex of said prism and which overlap in the far field so as to define a composite illumination beam having a broad forward aspect and essentially devoid of light in the space above a horizontal plane passing through the generally parallel axes of said optical system.

5 more elements

A continuous duty low backscatter illuminator comprising, in combination:

(a) an optical system having (i) a first entrance pupil, (ii) first and second exit pupils operatively associated with said first entrance pupil and disposed on generally parallel optical axes, (iii) a second entrance pupil and (iv), third and fourth exit pupils operatively associated with said second entrance pupil and disposed on generally parallel optical axes;
(b) means for forming first and second collimated light beams of relatively high radiant intensity and for directing the first and second collimated beams thus formed through respective different ones of said first and second entrance pupils of said optical system;
(c) first and second image splitting reflecting prisms mounted in said illuminator,
(d) means for imaging the first distribution image formed by the first collimated light beam at said first entrance pupil at the apex of said first reflecting prism so as to split the first distribution image along a line bisecting the axis thereof to form first and second halves of the first distribution image which are respectively reflected in generally opposite directions by said first reflecting prism;
(e) means for imaging the second distribution image formed by the second collimated light beam at said second entrance pupil at the apex of said second reflecting prism so as to split the second distribution image along a line bisecting the axis thereof to form first and second halves of the second distribution image which are respectively reflected in generally opposite directions by said second reflecting prism;
(f) first and second means for collimating respective ones of the first and second halves of the first distribution image formed at the apex of said first reflecting prism and, third and fourth means for collimating respective ones of the first and second halves of the second distribution image formed at the apex of said second reflecting prism, said first and second collimating means being mounted in said illuminator relative to said first prism and said third and fourth collimating means being mounted in said illuminator relative to said second prism so as to receive light only in the upper halves of their respective focal planes so that upon collimation of the light in the first and second halves of each of the first and second distribution images output beams are formed at each of said first, second, third and fourth exit pupils characterized by the absence of light in the space above a horizontal plane pass through the optical axes of said optical system;
(g) means for imaging the first and second halves of the first distribution image at respective ones of said first and second exit pupils so as to form a pair of generally parallel beams of light which overlap in the far field so as to define a first portion of an illumination beam;
and,
(h) means for imaging the first and second halves of the second distribution image at respective ones of said third and fourth exit pupils so as to form a pair of generally parallel beams of light which overlap in the far field so as to define a second portion of the illumination beam with the first and second portions defining an illumination beam having a broad forward aspect and essentially devoid of light in the space above a horizontal plane passing through the generally parallel optical axes of said optical system.

6 more elements

Dependencies are inferred from the claim text.

Low backscatter illumination system

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Low backscatter illumination system

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Abstract

Claims39