In March of this year we posted a report titled "Microsoft Invents Projector Eyewear for Xbox & Beyond" which excited many in the gaming world. Then in May we posted a report involving Microsoft's invention relating to transparent displays which supported Microsoft's video display eyewear and gaming helmet. Then out of nowhere The Verge revealed a document about Microsoft's forthcoming Kinect Glasses Project which all but confirms that Microsoft will enter the video display eyewear market in the 2013-2014 time frame. In today's report we reveal yet another patent application from Microsoft that details some of the advanced optic technologies going into their future video eyewear. The magic has to be set just right when trying to blend both real and virtual worlds together so as to provide users with a seamless gaming experience. It sure looks like Microsoft is ready to take gaming to a whole new level and it'll be interesting to see how Sony responds to this potential threat in the coming months ahead.
Microsoft's Patent Background
A see-through display merges a display image and an external image, presenting both images in the same physical space. Such a display may be used in a wearable, head-mounted display system; it may be coupled in goggles, a helmet, or other eyewear. The see-through display enables the viewer to view images from a computer, video game, media player, or other electronic device, with privacy and mobility. When configured to present two different display images, one for each eye, this approach may be used for stereoscopic (e.g., virtual-reality) display.
To provide a positive viewing experience, a head-mounted display system may be configured in view of certain ocular relationships. One such relationship is the placement of the focal plane of the display image relative to a background subject in the external scene. If the focal plane of the display image is too far from the background subject, the viewer may have difficulty focusing and may experience eyestrain.
Microsoft's Proposed Solution
To get around the problems related to misalignment of the focal plane, Microsoft's invention provides a method for overlaying first and second images in a common focal plane of a viewer. The method comprises forming the first image and guiding the first and second images along an axis to a pupil of the viewer.
The method further comprises adjustably diverging the first and second images at an adaptive diverging optic to bring the first image into focus at the common focal plane, and, adjustably converging the second image at an adaptive converging optic to bring the second image into focus at the common focal plane.
The Illuminator & Image Former
In Microsoft's patent FIG. 3 shown below we're able to see aspects of an example see-through display device 12 in one embodiment. The display device includes an illuminator (patent point #22) and image former (patent point #24). In one embodiment, the illuminator may comprise a white-light source, such as a white light-emitting diode (LED). The illuminator may further comprise suitable optics for collimating the emission of the white-light source and directing the emission to the image former.
The image former may comprise a rectangular array of light valves, such as a liquid-crystal display (LCD) array. The light valves of the array may be arranged to spatially vary and temporally modulate the amount of collimated light transmitted there through, such as to form pixels of the display image. Further, the image former may comprise suitable light-filtering elements in registry with the light valves, so that a color display image may be formed.
In another embodiment, the illuminator may comprise one or more modulated lasers, and the image former may be configured to raster the emission of the lasers in synchronicity with the modulation to form the display image. In yet another embodiment, the image former may comprise a rectangular array of modulated color LED's arranged to form the display image. As the color LED array emits its own light, illuminator (#16 of the Helmet in FIG. 2) may be omitted from the display device.
The Multipath Optic
Microsoft further describes the image former as being arranged to project the display image into the see-through multipath optic (patent point #26). The multipath optic is configured to reflect the display image to the pupil of a viewer – that is to say, the wearer of the head-mounted display system in which the display device is installed.
The multipath optic is also configured to transmit to the viewer's pupil an external image of a scene arranged external to the display device and opposite the viewer. In this manner, the multipath optic may be configured to guide both the display image and the external image along the same axis A to the pupil.
The Combined Optical Power of the Illuminator, Image Former & Multipath Optic
Microsoft now brings it all together. According to Microsoft documentation, the combined optical power of the illuminator, image former and multipath optic may be such as to project a virtual display image focused "at infinity." This configuration, absent further converging or diverging optics, may provide a positive see-through display experience when the scene viewed through the display device has a relatively large depth of field.
It may provide a less positive experience, however, when the depth of field is shallow. At issue here is the way that the human brain controls the focus of the eye. In sum, the brain is antagonistic to plural background subjects in a scene. Instead of establishing a different focus for background subjects arranged at different depths, the brain will try to use a common focus for all background imagery. Thus, if the wearer of a head-mounted display system is viewing a virtual display image focused at infinity, and facing a wall five meters away, the display image would appear to float in front of the wall; the wall and the display image would both be resolved without a change in focus of the wearer's eye. If the wearer then places a hand in front of his or her face, resolving the hand would induce a change in focus, and when the hand is in focus, the wall and the virtual display image would appear blurred.
However, the brain's attempt to align background imagery is limited by the eye's finite depth of field. If the viewer in the present example moves closer to the wall--e.g., to thirty centimeters--it will be impossible for the same corneal focus to sharply image both the wall and a virtual display image projected at infinity. Continued attempts to do so may cause the viewer to experience eyestrain and headache.
Incorporating Adaptive & Diverging Lenses
In view of the issues noted above, display device 12 noted in FIG. 3 is configured to project a virtual display image at an adjustable (i.e., movable) focal plane. The focal plane is adjusted dynamically in response to the distance to the background subject (patent point #34), and to other factors.
Accordingly, the display device includes adaptive diverging lens (patent point #38) and diverging lens driver 40A. The adaptive diverging lens is one example of an adaptive diverging optic having adjustable optical power. It is arranged between the multipath optic and the viewer's pupil, and is configured to adjustably diverge the display image and the external image such that the display image is brought into focus at a target focal plane.
The diverging lens driver is operatively coupled to the adaptive diverging lens and configured to adjust the optical power of the lens. It is configured to control the focal length of the adaptive diverging lens in response to a control signal from controller 16. In this manner, the focal plane of the virtual display image could be moved back and forth--e.g., from infinity to a finite depth. The controller, meanwhile, receives one or more forms of input that enable it to determine the desired target position of the focal plane
The Adaptive Convergence Lenses
Because the adaptive diverging lens is located directly in front of the viewer's eye, it has optical power, and because its optical power is subject to change, this lens is liable to defocus the external image of scene 30 transmitted there through. Accordingly, the display device also includes adaptive converging lens 42 and converging lens driver 40B. The adaptive converging lens is one example of an adaptive converging optic having adjustable optical power. It is arranged at an opposite side of the multipath optic relative to the adaptive diverging lens, and is configured to adjustably converge the external image to bring the external image into focus at the target focal plane.
In another embodiment, the focal length of adaptive converging lens 42 may be adjusted in concert with that of adaptive diverging lens 38 so that a constant optical power is applied to the external image of the scene. This approach may be used to provide a see-through display experience while also correcting for the viewer's myopia, hyperopia and/or presbyopia.
Display Sensors Control Head Tracking
And lastly, Microsoft's patent FIG. 3 illustrates that their future headsets includes both a linear accelerometer 46 and a gyroscopic sensor 48. Coupled anywhere within the head-mounted display system, the sensors are designed to furnish signals responsive to the viewer's head motion to the controller. For example, the linear accelerometer may detect when the viewer's head has tilted away from the optical axis of the display device indicating that a focal correction of the display image and/or the external image may be desired. Likewise, the gyroscopic sensor may be used to detect a rotation of the viewer's head, suggestive of a change in focus.
Microsoft's patent application was originally filed in Q4 2010 and published by the US Patent and Trademark Office in Q2, 2012.
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