Computer graphics processing and selective visual display system – Image superposition by optical means – Operator body-mounted heads-up display
Reexamination Certificate
1998-04-09
2002-06-18
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Image superposition by optical means
Operator body-mounted heads-up display
C345S007000
Reexamination Certificate
active
06407724
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of and apparatus for viewing an image.
BACKGROUND OF THE INVENTION
In head-mounted optical displays (such as are used in the recreation industry for viewing virtual reality images), it has been the practice to project an image to be viewed into the observer's eyes using conventional refractive and reflective optical elements, i.e. lenses and mirrors. However, in head-mounted displays where weight and size are major considerations it is normally possible to provide only a very small field of view by this means, which is a disadvantage when it is desired to provide the observer with the sensation of being totally immersed in a virtual world. In an attempt to overcome this problem, it has been proposed to use so-called “pancake windows”, i.e. multi-layer devices which use polarisation and reflection techniques to simulate the effect of lenses and mirrors. However, such devices suffer from the problem that they have low transmissivity.
Particularly with the factors of size and weight in mind, wide field optics designs have turned to diffractive optical solutions. It is known that diffractive techniques can be used to simulate the effect of a lens, by reducing the profile to a kinoform (
FIGS. 1 and 2
) or by the use of fixed surface or volume holograms. However diffractive optics have always suffered from extreme chromatic aberration when used in full colour imaging systems. Correction methods which have included multiplexing holograms recorded with different wavelengths in a single emulsion have been suggested. Such schemes still exhibit residual crosstalk between the colour channels which makes them inappropriate for high quality imaging systems.
Additionally, wide fields of view lead to problems in other forms of aberration correction, as well as difficulties in supporting the data bandwidth required to support high resolution across the entire field of view.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of and apparatus for viewing images which improve on the techniques described above.
According to a first aspect of the present invention, there is provided a method of viewing an image, the method comprising transmitting an image into an eye of an observer by means of a dynamic optical device, the dynamic optical device being operative to create a modulation in respect of at least one of phase and amplitude in light transmitted or reflected thereby, said modulation being variable from one point or spatial region in the optical device to another, and wherein the modulation at any point or spatial region can be varied by the application of a stimulus, and altering the characteristics of the dynamic optical device so that the dynamic optical device acts sequentially to direct light of different colours to the observer's eye.
The expression “transmitting an image” is intended to include the formation of a virtual aerial image at some point, or the projection of a real image onto the surface of the observer's retina.
According to a second aspect of the present invention, there is provided apparatus for viewing an image, comprising a dynamic optical device, the dynamic optical device being operative to create a modulation in respect of at least one of phase and amplitude in light transmitted or reflected thereby, said modulation being variable from one point or spatial region in the optical device to another, and control means operative to apply a stimulus to the dynamic optical device, whereby the modulation at any point or spatial region can be varied, the control means being operative to alter periodically the characteristics of the dynamic optical device so that the device acts sequentially to direct light of different colours to the observer's eye.
The dynamic optical device can comprise a succession of layers which are configured to act upon the primary wavelengths, respectively, or the different colour channels may all be embodied in the one layer of the dynamic optical device.
Moreover, the optical power (focal length), size, position and/or shape of the exit pupil and other optical parameters can also be controlled.
The above-described method and apparatus allow the provision not only of a relatively wide field of view, but also a large exit pupil, a movable exit pupil of variable shape, and high resolution.
Conveniently, the dynamic optical device comprises a spatial light modulator containing an array of switchable elements in which the optical state of each element can be altered to create a change in phase and/or amplitude in the light incident thereon. Alternatively, the dynamic optical device can comprise an array of switchable prerecorded holographic elements, wherein more complex phase functions can be encoded within the holograms. In this case, the dynamic optical device can also comprise non-switchable holographic elements.
Advantageously, the dynamic optical device comprises an electrically switchable holographic composite.
Desirably, the dynamic optical device is used in a range in which the phase and/or amplitude modulation varies substantially linearly with applied stimulus.
The dynamic optical device is preferably used in a range in which it does not substantially affect the amplitude and/or wavelength characteristics of the light transmitted or reflected thereby.
The dynamic optical device can be in the form of a screen adapted for mounting close to the observer's eye. The screen can be of generally curved section in at least one plane. Alternatively, for ease of manufacture, the screen may be planar. Conveniently, the apparatus also comprises means for engaging the screen with the observer's head in a position such that the curve thereof is generally centred on the eye point.
In one arrangement, the dynamic optical device acts upon light transmitted therethrough, and the image generator is located on a side of the dynamic optical device remote from the intended position of the observer's eye. In an alternative arrangement, the dynamic optical device acts upon light reflected thereby, and the image generator is at least partially light-transmitting and is located between the dynamic optical device and the intended position of the observer's eye.
The apparatus may include image generation means configured off-axis from the general direction of the observer's eye in use. In that case, the image generation means can be non-light transmitting.
In one arrangement, the dynamic optical device comprises a plurality of discrete optical elements in close juxtaposition to each other, each of which acts as an individual lens or mirror. Conveniently, some of the discrete optical elements act to direct to the observer's eye light of one colour, while others of the discrete optical elements act to direct to the observer's eye light of other colours.
In one preferred embodiment of the invention, the apparatus may comprise left and right image generation means, left and right dynamic optical devices and left and right side portions within which said left and right image generation means are housed, said left and right image generation means being operative to project towards said left and right dynamic optical devices respectively, thereby displaying a binocular image. The apparatus can also be arranged to provide for the full range of accommodation and convergence required to simulate human vision, because the parameters governing the factors can be altered dynamically.
Advantageously, the dynamic optical device functions to correct aberrations and/or distortions in the image produced by the image generator. The dynamic optical device can also function to create a desired position, size and/or shape for the exit pupil.
The method may further comprise the steps of controlling the characteristics of the dynamic optical device to create an area of relatively high resolution in the direction of gaze of the observer's eye, the dynamic optical device providing a lesser degree of resolution of the image elsewhere, and sensin
Popovich Milan Momcilo
Storey John James
Waldern Jonathan David
DigiLens Inc.
Kovalick Vincent E.
Shalwala Bipin
Skjerven Morrill & MacPherson LLP
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