I've always felt that the viewfinder application is a good fit for virtual displays. The large equivalent image will allow "on the spot" assessment of the photo; a real display of the same form factor is too small. Hooking up with a major chipset provider is a good move by Kopin.
IMO, some design factors for which the transmissive approach has advantages over reflective are flexibility, realism and ease of magnification. For the camera viewfinder, two desirable features are realism of the image and instant updating. Fast response time is required for the viewfinder image to update in real time, e.g. using 180 Hz color sequential operation. Displays from Kopin and some others including Displaytech have this capability, which also permits use of red, green and blue LEDs for reduced power consumption versus white backlights. If a high degree of grayscale or brightness control is also possible at each pixel, a precise RGB mixture (~tristimulus values) can be achieved to give any desired composite color. Displaytech uses a ferroelectric LCD for fast switching speed, but since that is a binary system, grayscale control must be done using inferior averaging techniques. Another important consideration is viewability under a range of lighting conditions.
The reflective approach uses a more standard IC fabrication method (no transfer procedure) so cost may ultimately be lower. This also results in a lower barrier to entry for reflective, so that side is getting crowded, whereas Kopin has less competition on the transmissive side. So, if most manufacturers opt for transmissive, after weighing the factors important to them, Kopin will be well positioned. The next hurdle will then be consumer acceptance of virtual displays, whichever approach is used. WT
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