Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
1999-12-20
2001-10-16
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S632000, C359S639000
Reexamination Certificate
active
06304386
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
An object of the present invention is a device enabling the manufacture of light-weight, ergonomic helmet-mounted visual display systems, in which a luminous image is seen in a state where it is superimposed on the view of the outside scene.
2. Background of the Invention
This type of helmet-mounted visual system is used in aeronautics, the observer being the pilot of an airline or helicopter.
In particular, warplanes or combat helicopters require the presentation of piloting and firing control information as well as intensified images of the surroundings of the airline or helicopter. All this information may be presented on a head-up visor present in all warplanes and in certain helicopters.
The drawback of this type of display is that it can present an image only in a limited field that is always centered on the axis of the aircraft while the pilot may have to take sightings at a distance from the axis of the aircraft. This is why, at present, display devices are integrated into the pilot's helmet, with the pilot carrying the field of display with him. Integrated devices of this kind enable the pilot to keep autonomous systems, especially intensified image-taking systems, with him. These may comprise in particular an image-taking objective coupled with a light intensifier, a relaying optical system for the projection, on the visor of the helmet, of an image that is sent back towards the pilot's eyes in being superimposed on an ambient scene.
Despite these advantages, the presentation of the image on a visor suffers from defects inherent in its use in projection on a tilted visor.
These defects are in particular of two kinds: the first kind relates to image distortion. Indeed, owing to major variations of incidence on the visor due to its inclination as a function of the field observed, the image projected on a visor is distorted (this is often called the second type of off-center distortion).
The second kind of defect relates to the astigmatism introduced into the image. The tilting of the visor has, for a given field, an influence on the quality of the image within one and the same field: the radius of curvature seen along a given plane differs from that observed along a plane orthogonal to the first plane. The rays, with respect to these two planes, therefore get focused at different places.
To compensate for these optical defects, certain solutions have been considered. In particular, it is possible to use a toroidal visor to compensate for distortion and astigmatism.
However, the designing of a toroidal visor remains difficult to implement.
Another approach consists of the introduction, after the image-taking objective, of an optical aberration correction device using a CCD circuit and then a cathode-ray tube to recreate a corrected image. A device of this kind increases the weight of a pilot's helmet and generally calls for a high voltage supply that is incompatible with an independent system capable of being carried with the pilot when he ejects.
SUMMARY OF THE INVENTION
To overcome these different drawbacks, the invention proposes a display device for a helmet-mounted visual system using at least one optical prism having optical aberrations that are capable of compensating for the distortion and astigmatism type of aberrations created by the visor in the images.
Indeed, in a prism, at refraction during the passage between the air and the middle of the prism, the non-linearity of the variations of incident angles and refracted angles induces an image deformation of the same type as the one shown in FIG.
1
.
FIG. 1
pertains to a matrix of dots of an undistorted image.
FIG. 1
b
pertains to a matrix of image dots distorted by the visor. Furthermore, the optical prism has an invariance by translation along a particular plane. Its properties of refraction therefore differ within one and the same field between this plane and the plane that is orthogonal to it. This phenomenon is similar to astigmatism.
More specifically, an object of the invention is a display device for helmet-mounted visual systems comprising:
an intensified image-taking device delivering a first optical beam;
a visor;
means for the superimposition, before an observer, of an outside scene and the first optical beam delivered by the intensified image-taking device through an relaying optical system;
characterized in that the relaying optical system comprises at least one optical prism to compensate for the distortion and astigmatism introduced by the visor on said first optical beam.
The display device for a helmet-mounted visual system may advantageously furthermore comprise an image generator,emitting a second optical beam that carries information, and a mixer so as to superimpose the first optical beam and the second optical beam, at the relaying optical system.
According to one variant of the invention, the means used to superimpose an outside scene and the intensified images taken are integrated into the visor.
According to another variant of the invention, the means used to superimpose an outside scene and the intensified images taken comprise an independent combiner made of glass.
Indeed, the invention can also be applied in the case of a combiner not integrated into the visor which may have a curved reflecting surface as shown in
FIG. 2
, this reflecting surface creating the same type of distortion is as a visor. This type of combiner comprises a curved reflecting surface Sc with a center of curvature C, coupled with a complementary prism PC to direct the optical beam of intensified images or synthetic images L towards the pilot's eye
11
.
To improve the performance characteristics of the device without encumbering it, the optical prism may comprise means to make the optical beams perform at least one outward journey and one return journey in said optical prism.
The optical prism used in the device according to the invention may advantageously comprise a curved face so as to approach the visor effect for improved compensation of the optical aberrations introduced by the visor.
REFERENCES:
patent: 3870405 (1975-03-01), Hedges
patent: 4468101 (1984-08-01), Ellis
patent: 4761056 (1988-08-01), Evans et al.
patent: 4775217 (1988-10-01), Ellis
patent: 4828378 (1989-05-01), Ellis
patent: 4961626 (1990-10-01), Fournier, Jr. et al.
patent: 5459612 (1995-10-01), INgleton
patent: 5646783 (1997-07-01), Banbury
patent: 5917656 (1999-06-01), Hayakawa et al.
patent: 6195206 (2001-02-01), Yona et al.
Epps Georgia
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sextant Avionique
Seyrafi Saeed
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