New technology makes VR a less weighty experience

New technology makes VR a less weighty experience

The size and weight of head-mounted displays are a tough challenge for manufacturers that want to bring them to high-volume commercial applications, but new technologies are changing the conventional perception of the devices as bulky headgear.

A promising breakthrough has come from MicroOptical Corp. The 5-year-old company from Westwood, Mass., is building tiny, featherweight displays that will bring a computer image to users in a device the size of conventional eyeglasses.

Developed under a Defense Advanced Research Projects Agency contract for the Army Soldier Systems Command, the lightweight glasses are not expected to provide an immersive VR environment, as high-end HMDs do. But the technology will be immediately applicable for so-called augmented reality applications, in which displays are used to superimpose virtual aspects such as text or graphics over a real image.

MicroOptical's ClipOn display provides a see-around information display at a fixed focus of 1 meter. Users can order the eyepieces with different settings.

An example is a printed circuit board production environment where the addition of text and graphics might help a technician eliminate time-consuming references to a manual.

Divide and conquer

Although conventional HMDs position an LCD in front of each of the user's eyes, MicroOptical engineers have shrunk the size of their device by splitting the problem into image creation and image presentation.

The glasses operate by taking an image generated by a computer, VCR, television or other electronic device and generating an image on a miniature LCD that is placed in the temple portion of a pair of glasses or in an L-shaped optics module that clips onto the temple.

The light rays from the display are relayed to the eye through reflectors within the eyeglass lens. The reflectors fold the optical path and magnify the image so that it can be viewed comfortably.

The user sees an image floating in space at an adjustable focal distance of two feet or more. When the display is turned off, the image disappears, and the user can see normally through the eyeglass lens.

By eliminating external lenses and other optical components and building the electronic circuits into the eyeglass frame, the savings in terms of size and weight are dramatic.

The company's initial clip-on version weighs only 1.05 ounces; the built-in display adds 3.5 ounces to a convention set of eyeglasses.

Each requires 50 to 80 milliwatts of power and offers a diagonal field of view of 12 to 15 degrees.

But the technology is attractive because it offers excellent see-through capability. That lets a user easily focus from the monitor to the real world and back again without feeling disoriented.

It also opens the door to the superimposition of information onto a real scene. Potential applications might include the image of a night-vision camera on a soldier's glasses or the superimposition of information to help a fighter pilot aim a missile.

Back to the future

How far engineers can take this technology and what kind of applications it can support remain to be seen. Although MicroOptical's initial product supports only relatively low 320- by 240-pixel resolution in an 8-bit grayscale image, higher resolution versions capable of supporting 640- by 480-pixel and 800- by 600-pixel levels and color images are under development.

And although the technology has been developed for monocular applications, it can be applied to both lenses in the eyeglasses to form 3-D images.

'John H. Mayer


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