Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2002-01-23
2003-10-28
Dang, Hung Xuan (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S630000, C359S631000, C359S638000, C345S007000, C345S008000
Reexamination Certificate
active
06639706
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of optical devices, in particular, to a method and apparatus for switching an optical path from an enhanced view to a direct view, and having modes where the viewer can see both simultaneously.
BACKGROUND OF THE INVENTION
It is sometimes required to superimpose an optical image derived electronically on to an external scene viewed through an eyepiece by an observer so that the observer can see both the electronic image as well as the external scene together. This requirement has been addressed in the prior art so, as to permit, for example, a pilot to see flight data superimposed on an external scene.
In some applications of sights the need may arise for image enhancement of the observed scenery before displaying it to the observer.
Although in use for years, head mounted display (HMD) systems have been the subject of continual development and improvement. Applications of such systems range from flight and weapons control for military aircraft to display systems for games. Of particular interest are displays which combine multiple images. For example, most modern military aircraft use heads-up display technology to superimpose information for a variety of flight and weapons systems over the pilot's natural view of the outside world. This provides the pilot with additional information without requiring that the pilot look down towards the instrument panes. A second use of head mounted systems is for night vision goggles in which the user is presented with both a natural image of the outside world as well as an artificial image in which the light levels have been intensified. A third use for such systems is to provide a pilot or other user with a low resolution, wide field-of-view image of a particular scene combined with a high resolution image of a small section of the same scene. This allows the user to retain knowledge of the overall surroundings while obtaining detailed information about a particular area of interest.
Currently, there are two basic approaches to providing a user simultaneously with multiple images. The first or binocular approach presents both eyes of the user with both images. For example, a pilot may use a see-through HMD of this type which allows a natural view of the outside world. The desired additional information is provided using a projected image, typically projected on the pilot's visor. The second or monocular approach provides each eye of the user with different image information. For example, a pilot flying at night can be presented with a natural view as well as a light intensified view, each view being provides to a separate eye. One advantage of this system is that the eye which is not viewing the light intensified scene remains dark adapted.
U.S. Pat. No. 5,162,828 to Furness et. al. discloses a display system for conventional spectacles having a transparency that defines a field of view and a frame for supporting the transparency on a user's head. The display system includes a display mounted on the frame of the spectacles and optics for collimating light to project an image of the displayed information at a distance from the user in the periphery of the field of view defined by the transparency. According to one embodiment, the optics includes a single mirror which receives the information directly from the display and projects an enlarged image at an apparent optical distance from the user that is greater then the actual optical path length. Alternatively, a planar mirror and collimating lens may be employed.
Such systems are commonly mounted on, or in conjunction with, a pilot's head up display and typically employ a miniature CDD TV camera mounted either on the head up display or to a visor thereof. For example, U.S. Pat. No. 5,341,242 to Gilboa et. al. discloses an optical projector which projects an image on to the semi-transparent portion for reflection from it. The semi-transparent portion has a relatively higher reflectivity in a central area and a relatively lower reflectivity in an annular area outside the central area. In accordance with one embodiment, the head mounted display included a projector having a display source where an image is formed. An optical system for focusing the image at separate sagittal and tangential foci is provided between the image-forming surface and the semi-transparent portion. Such an arrangement may be employed in a visor attached to a pilot's helmet, such that the visor has a partially reflecting semi-transparent portion in view of the pilot.
U.S. Pat. No. 4,398,799 to Swift discloses a pilot's head-up display wherein an image of selected display information is superimposed by means of a combiner on an external scene and reflected towards the pilot's eyes by means of a mirror disposed on his helmet in such a manner so as to not to interfere with his vision.
U.S. Pat. No. 5,113,177 to Cohen discloses a display system for enabling a pilot in an aircraft to view simultaneously an image of selected display information and a scene external to the aircraft during low visibility conditions, such as night-time. An image intensifier tube is mounted on the side of a pilot's helmet so that the image sensed coincides with the pilot's field of view. The image intensifier tube intensifies the light from the external scene and output voltages representative of the scene to a converter whose output is itself converted to a suitable video signal with video signals from other sources, such as instrumentation panel displays. The combined electrical signals are fed to a display driver so as to allow superimposition of the selected display information on the external scene viewed by the pilot.
In the above systems described by Gilboa et al, Swift and Cohen and in all similar systems, the viewer sees the scene either with light enhancement, as commonly found in Night Vision Goggles, or else with superimposed images of data from other sources.
U.S. Pat. No. 6,088,165 issued to Janeczko et al. discloses an optical assembly for receiving light from a viewed object via folded and a direct path. An objective lens assembly is included to receive and focus visible and infrared light to visible intensified light. A beam combining means directs the combined light to a viewer's eye. U.S. Pat. No. 6,061,182 issued to Carmeli et al. discloses an optical combiner for viewing a first image and injecting a non-collimated light beam from a second image, presenting a combined image to the viewer. Although both these patents disclose an apparatus capable of providing a direct view, and a combined view of a light intensified with the direct view, there is no mention in either patent about a switch to change views from enhanced to direct viewing.
Other patents disclose devices that superimpose displays or data on an image. U.K. Patent No. 2,115,575A discloses an optical viewing device that includes an eyepiece receiving an image of opto-electric elements whose optical transparency can be varied by varying the voltage applied to the elements. A display is thereby generated that is superimposed on the scene viewed through the eyepiece. This device is directed solely towards superimposition of images.
Therefore, there is still a need in the art for a device that will allow both direct view of the scenery and an enhanced view, simultaneously.
SUMMARY OF THE INVENTION
The present invention relates to an optical path switch for creating two optic pathways for input light. The switch is composed of two polarizers that polarize the input light and two polarization rotators each having two positions. The polarization rotators position translates to one of two the optic pathways. Additionally, the optical path switch has an image enhancement device for producing an enhanced image of the light, and a beam splitter that directs the light to two channels. The optical path switch works by polarizing the light by one of the two polarizers, producing an output. Following, the output is directed through the beam splitter towards two channels. Nex
Filipovich Danny
Fiore Jack
Uy Philip
Ziv Ofer R.
Dang Hung Xuan
Kollsman, Inc.
Martinez Joseph
Ritchie William B.
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