Helmet-mounted optical systems

Details Helmet-mounted optical systems Helmet-mounted optical systems

1995-01-26

1997-07-08

Epps, Georgia Y.

Optical: systems and elements

Single channel simultaneously to or from plural channels

By partial reflection at beam splitting or combining surface

359634, G02B 2714

Patent

active

056467834

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to compact optical systems, especially to portable optical systems adapted to project images across the wearer's field of view. The invention has particular, but not exclusive, application to the provision of head-up display images for aircrew, and provides a means by which an optical system may be employed to convert an image provided by a small cathode ray tube (CRT), matrix array or other light source (typically mounted on the flying helmet) into a collimated, head-up form suitable for the display of information. Other possible applications of the invention are in connection with military and high-performance vehicles.
2. Discussion of Prior Art
There is an increasing need for this provision in both fixed and rotary-wing aircraft, the information to be displayed being required to complement the electronic display facilities installed in the aircraft cockpit. Whilst any presentation of information in a head-up format (in accordance with established criteria) will enhance operator performance, a particularly useful facility provided by head-mounted displays would be the display of information superimposed over the viewer's outside view in whatever direction the viewer's head was pointing.
Unfortunately, severe inertia and volume constraints are placed on the provision of equipment supported on the human neck, and in this respect particularly strict limits are imposed for fast-jet applications where a need for greater head freedom compounds difficulties already aggravated by the effects of high-g manoeuvres. Other requirements, essential for fast-jet operation, such as the provision of safe ejection and birdstrike protection, are not needed in rotary wing operations which are restricted to a much smaller flight envelope with no requirement for emergency ejection (in the same sense). For the latter applications it is therefore relatively straightforward to supply more facilities and to achieve a higher technical performance.
Nevertheless for all these applications there is a demand for maximum performance for the minimum size and weight, and this invention is intended to provide apparatus which is physically acceptable and can provide a good optical performance and range of facilities.
Certain proposals have been made for projecting a head-up display from helmet-mounted components, such as those described in EP-A-11,024, and for the design of individual components, such as eye position sensors as described in EP-A-408,344, but hitherto no proposal has been made for a system which effectively integrates the optical components in a way which meets the requirements set out above.


SUMMARY OF THE INVENTION

This invention accordingly consists of an optical system mounted on a helmet for superimposing a collimated image of a display object on the external view of the helmet's wearer characterised by:
display object means mounted on the helmet for generating a display;
a collimator having the function of a concave mirror for collimating light from said display;
an optical relay unit located in the forehead region for generating an intermediate image of said display in the focal plane of the collimator;
a reflecting surface for reflecting display light from the relay unit towards the collimator;
and an inclined combiner, essentially transparent to incoming display light and to the wearer's external view, for reflecting display light reflected from the collimator towards the viewer's eye;
the collimator being located away from the wearer's external view through the combiner and being located on the opposite side of the said external view with respect to the optical relay unit.
The collimator may be used axially but to take advantage of the diffractive properties of the combiner a quasi-axial configuration is preferred.
The system preferably includes at least one additional reflecting surface to enable the display object means, which might for example be the screen of a CRT or an NVG image intensifier, to be mounted in a convenient locati

REFERENCES:
patent: 4028725 (1977-06-01), Lewis
patent: 4361384 (1982-11-01), Bosserman
patent: 5257094 (1993-10-01), LaRussa

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