Optics: image projectors – Stereoscopic
Patent
1996-02-15
1997-09-30
Dowling, William
Optics: image projectors
Stereoscopic
353 98, 359464, G03B 2114
Patent
active
056719922
DESCRIPTION:
BRIEF SUMMARY
The present invention relates generally to systems for providing a 3 dimensional visual effect in a viewed image, and in particular to a stereoscopic display unit.
A number of systems are known for providing three dimensional visual effects in a viewed image. Many of these systems require the use of polarised glasses to produce the desired "3-D" effect in the viewed image. However, because of the general inconvenience in requiring special glasses to view such images, attempts have been made to develop systems which do not require such glasses.
Such systems have incorporated components such as passive and dynamic grids, lenticular lenses, and mirror arrays to produce the 3-D effect in an image which can be viewed with the naked eye. However, common problems associated with these systems include flickering unclear images, low image brightness, and the need for the viewer to be accurately positioned to receive the image.
For example, in Australian Patent 636228 (Thorn EMI PLC) there is disclosed a 3-D viewing apparatus in which light from a single cathode ray tube, or light reflected from an object, is passed through an arrangement of retroreflectors and a beam splitter to produce a real image suspended in space for viewing as an apparent 3-D image, the 3-D effect being created by reducing the strengths of cues which are responsible for the perception of flat images. It has however been found in practice that the 3-D effect provided by this apparatus is negligible, and that the image is blurred, is low in brightness and is therefore difficult to view.
It is therefore an object of the present invention to provide a stereoscopic unit overcoming at least one of the above noted problems.
With this in mind, there is provided a stereoscopic display unit including at least two projection units for projecting optical signals corresponding to the left and right image fields respectively of a stereoscopic image, and an optical focusing system for focusing the two image fields to at least two focus regions at a viewing position outside the display unit, the left and right image fields each being respectively focused into the respective eyes of at least one viewer when located at said viewing position, wherein the optical focusing system includes at least one retroreflective mirror and a semi-reflective mirror disposed at an angle to the at least one retroreflective mirror, the semi-reflective mirror being partially reflective and partially transmissive, the optical signal being reflected between the at least one retroreflective mirror and the semi-reflective mirror and to said viewing position.
The display unit of the present invention leads to a 3-D image of greater brightness, absence of flicker and tolerance of viewer movement.
At least a portion of the optical signals are preferably reflected from the semi-reflective mirror onto the retroreflective mirror, the optical signals being subsequently reflected from the retroreflective mirror and through the semi-reflective mirror to the viewing position.
The display unit preferably includes a tracking system for determining the spatial position of the head or the eyes of the or each viewer. The projectors are preferably mounted on a carriage for varying the position of the projectors relative to an x-axis of movement. The adjustment of the position of the projectors relative to said x-axis is preferably controlled by said tracking system, the relative position thereof effecting tracking of the movement of the or each viewer in a direction parallel to said x-axis. In a preferred arrangement, the semi-reflective mirror is pivoted about an axis parallel to the said x-axis. This allows control of the angle between the semi-reflective mirror and the retroreflective mirror. This adjustment of the angular position of the semi-reflective mirror is controlled by the tracking system, the relative angular position thereof effecting tracking of the movement the or each viewer in a direction parallel to a y-axis of the movement thereof, said y-axis of movement being normal to said x-a
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Dowling William
Xenotech Research Pty. Ltd.
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