Nice stuff from Microsoft

This has been sitting in my un-done file because I've been slammed lately. Unfortunately has to stay a little less done than I'd like it to be.]

Background info and conclusion, in photographic form at the top.

Have a nice weekend.

Thanks Joe

MSpoweruser Method for getting 4K in near eye 


However, current MEMS technology places an upper limit on mirror scan rates, in turn limiting display resolution. As an example, a 27 kHz horizontal scan rate combined with a 60 Hz vertical scan rate may yield a vertical resolution of 720p. Significantly higher vertical resolutions (e.g., 1440p, 2160p) may be desired, particularly for near-eye display implementations, where 720p and similar vertical resolutions may appear blurry and low-resolution. While an increase in the horizontal and/or vertical scan rate would increase display resolution, the former may be technologically infeasible while the latter increases power consumption. Further, high scan rates may at least partially constrain mirror scan angle and aperture, where larger values are also desired. Additionally, supporting higher resolution also may require a larger mirror size due to the diffraction limit associated with smaller “pixel” sizes. The use of such a larger mirror may further increase the difficulties in achieving higher resolutions with scanning displays, as the larger mirror leads to a lower scanning frequency.

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The technology is applicable to a variety of output methods, including waveguides such as in the HoloLens, but also laser projection TVs and other systems which uses lasers and MEMS.

From the patent
[0051] Another example provides a method of displaying an image comprising directing light from two or more offset lasers toward a scanning mirror system, and scanning light from the two or more offset lasers in a first direction at a higher frequency and in a second direction at a lower frequency to thereby scan the laser light in an interlaced pattern and form the image. In such an example, the method alternatively or additionally may comprise mapping a gaze direction determined via an eye tracking sensor to a region in the image, and adjusting one or more of the scan rate in the second direction and the phase offset based on the region in the image. In such an example, scanning the light from the two or more offset lasers in the first direction alternatively or additionally may comprise scanning the light in the first direction at a frequency of 27 kHz to 35 kHz. In such an example, scanning the light from the two or more offset lasers alternatively or additionally may comprise scanning the light to form the image at a resolution between 1440p and 2160p. 


From Free Patents online
Embodiments of the present technology using the beam scanning assembly 100 described above will now be described with reference to the views of FIGS. 3-15 and the flowchart of FIG. 16. FIGS. 3a, 3b and 3c illustrate a structure and operation of a first embodiment of the MEMS laser scanner 200 according to the present technology. FIG. 3a shows image light incident on the optical element 102 at two different times. This figure illustrates the zero order diffracted light present since the diffraction gratings are not 100% efficient. This light does not contribute to the final image and would appear as a ghost so therefore some mechanism like a blocking aperture would be used to block the light from reaching the subsequent components in the optical system. FIGS. 3b and 3c show image light incident on the optical element 102 at two different times. These figures illustrate the formation of two separate fields of view by diffracting the display light onto the MEMS mirror 168 by two separate Bragg polarization gratings 170 and 171 as explained below. The image light is generated by a display engine 140 which emits image light in a step 300 that is modulated on a pixel-by-pixel basis by the controller 124. In embodiments, the display engine 140 may be a commercially available assembly, such as for example the PicoP™ display engine from Microvision, Inc. of Redmond, Wash.