Computer graphics processing and selective visual display system – Image superposition by optical means – Operator body-mounted heads-up display
Patent
1994-10-31
1998-03-31
Powell, Mark R.
Computer graphics processing and selective visual display system
Image superposition by optical means
Operator body-mounted heads-up display
359630, G02B 2312, G02B 2700
Patent
active
057343594
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a display system intended to be attached to the head or to a helmet, comprising at least an image intensifier unit having an input on which an image can be projected and an output which retransmits the projected image with an enhanced intensity and within at least a predetermined first frequency band, and an eyepiece which is composed of a first and second transparent reflecting element having angle- and frequency-dependent reflectance and transmittance properties, said properties in combination with the said first frequency band resulting in the intensified image emerging via the eyepiece in the direction of the eye.
2. Description of the Prior Art
Such a display system is disclosed by the European Patent Application 0 252 200. These display systems are used, inter alia, for the helmets of pilots especially of military airplanes and helicopters. Herein, a free direct-vision image is blended with a night image, the night image being an intensified image. For the purpose of obtaining a bright image of an environment whose light intensity is low, this known display system provides a user with an excellent bright image having a high resolution. Even if the intensity of the ambient light increases, a bright image is obtained as a user can also perceive the environment directly. A user wearing such a system is therefore able to use it to observe in daylight, dim light or in the dark, without the need of putting the helmet on or taking it off. This means that the ambient light is projected by the display system directly in the direction of the eye. A head attachment system or helmet provided with such a display system has the additional advantage that a centre of gravity which is ideally positioned for the user can be achieved.
The need has now arisen for a display system in which it is possible to blend day image, night image (intensified image) as well as video image with information such as angle data or distance data or other data. At the same time, it is also desirable for the advantages of the display system according to the European Patent Application 0 252 200 to be retained as well.
To this end, the display system according to the invention is characterized in that the display system is further provided with an image display device which transmits a visible video image in the direction of the eyepiece, the said properties of the eyepiece resulting in the video image emerging within a predetermined second frequency band via the eyepiece in the direction of the eye.
A user, such as, for example, a pilot, who is wearing a helmet provided with such a display system thus in principle need not turn his eyes away from the environment in order to observe the required armament system information or other information. The information coming from the image display device can, after all, be displayed in the field of vision of the pilot, while he, for example, is looking outwards straight ahead.
The European Patent Application 0 475 790 discloses a display system in which likewise day image, night image and video image are blended. In this case, however, use is made of only one (holographic) element to blend a video image and a night image. These two blended images are then projected, together with a daylight image, through combination optics in the direction of the eye. A drawback of such a system is that all three images are necessarily always displayed at an identical distance and are always simultaneously in focus for a user. This can have a particularly confusing effect. The European Patent Applications 0 286 496 and 0 288 365, and the U.S. Pat. No. 5,257,094 likewise disclose display systems in which images are blended with one another. In these systems, however, only two instead of a possible three images are blended with one another in each case.
SUMMARY OF THE INVENTION
A particular embodiment of the invention is characterized in that the intensified image is, successively, reflected by the first element and reflected and col
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B.V. Optische Industrie "De Oude Delft"
Marn Louis E.
Powell Mark R.
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