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It was not exactly a secret, but Osterhout Design Group (ODG) formally announce their new R-8 headset with dual 720p displays (one per eye) and R-9 headset with dual 1080p displays. According to their news release, “R-9 will be priced around $1,799 with initial shipping targeted 2Q17, while R-8 will be less than $1,000 with developer units shipping 2H17.
Both devices use use OLED microdisplays but with different resolutions (the R-9 has twice the pixels). The R-8 has a 40 degree field of view (FOV) which is similar to Microsoft’s Hololens and the R-9 has about a 50 degree FOV.
The R-8 appears to be marketed more toward “consumer” uses with is lower price point and lack of an expansion port, while ODG is targeting the R-9 to more industrial uses with modular expansion. Among the expansion that ODG has discussed are various cameras and better real world tracking modules.
With the announcement comes much better pictures of the headsets and I immediately noticed that their optics were significantly different than I previously thought. Most importantly, I noticed in the an ODG R-8 picture that the beam splitter is angled to kicks the light away from the eye whereas the prior ODG R-7 had a simple beam splitter that kicks the image toward the eye (see below).
The ODG R-8 (and R-9 but it is harder to see on the available R-9 pictures) does not have a simple beam splitter but rather a beam splitter and curve mirror combination. The side view below (with my overlays of the outline of the optics including some that are not visible) that the beam splitter kicks the light away from the eye and toward partial curved mirror that acts as a “combiner.” This curve mirror will magnify and move the virtual focus point and then reflects the light back through the beam splitter to the eye.
On the left I have taken Figure 169 from ODG’s US Patent 9,494,800. Light from the “emissive display” (ala OLED) passes through two lenses before being reflected into the partial mirror. The combination of the lenses and the mirror act to adjust the size and virtual focus point of the displayed image. In the picture of the ODG R-8 above I have taken the optics from Figure 169 and overlaid them (in red).
According to the patent specification, this configuration “form(s) at wide field of view” while “The optics are folded to make the optics assembly more compact.”
At left I have cropped the image and removed the overlay so you can see the details of the beam splitter and curved mirror joint. You hopefully can see the seam where the beam splitter appears to be glued to the curved mirror suggesting the interior between the curved mirror and beam splitter is hollow. Additionally there is a protective cover/light shade over the outside of the curved mirror with a small gap between them.
The combined splitter/mirror is hollow to save weight and cost. It is glued together to keep dust out.
I could not find a picture of the R-8 or R-9 from the inside, but I did find a picture on the “hey Holo” blog that shows the inside of the R-6 that appears to use the same optical configuration as the R-8/R-9. The R-6 introduced in 2014 had dual 720p displays (one per eye) and was priced at $4,946 or about 5X the price of the R-8 with the same resolution and similar optical design. Quite a price drop in just 2 years.
Interestingly, I could not find anywhere were ODG says what display technology they use in the 2014 R-6, but the most likely device is the Sony ECX332A 720p OLED microdisplay that Sony introduced in 2011. Following this trend it is likely that the ODG R-9 uses the newer Sony ECX335 1080p OLED microdisplay and the R-9 uses the ECE332 or a follow-on version. I don’t know any other company that has both a 720p and 1080p OLED microdisplays and the timing of the Sony and ODG products seems to fit. It is also very convenient for ODG that both panels are the same size and could use the same or very similar optics.
Sony had a 9.6 micron pixel on a 1024 by 768 OLED microdisplay back in 2011 so for Sony the pixel pitch has gone from 9.6 in 2011 to 8.2 microns on the 1080p device. This is among the smallest OLED microdisplay pixel pitches I have seen but still is more than 2x linearly and 4x in area bigger than the smallest LCOS (several companies have LCOS pixels pitches in the 4 micron or less range).
It appears that ODG used an OLED microdisplay for the R-6 then switched (likely for cost reasons) to LCOS and a simple beam splitter for the R7 and then back to OLEDs and the splitter/mirror optics for the R-8 and R-9.
This “trick” of mixing lenses with a spherical combiner partial mirror is an old idea/trick. It often turns out that mixing refractive (lenses) with mirror optics can lead to a more compact and less expensive design.
I have seen a beam splitter/mirror used many times. The ODG design is a little different in that the beam splitter is sealed/mated to the curved mirror which with the pictures available earlier make it hard to see. Likely as not this has been done before too.
This configuration of beam splitter and curve mirror even showed up in Magic Leap applications such as Fig. 9 from 2015/0346495 shown at right. I think this is the optical configuration that Magic Leap used with some of their prototypes including the one seen by “The Information.“
The ODG optical design while it may seem a bit more complex than a simple beam splitter, is actually probably simpler/easier to make than doing everything with lenses before the beam splitter. Likely they went to this technique to support a wider FOV.
Based on my experience, I would expect that ODG optical design will be cleaner/better than the waveguide designs of Microsoft’s Hololens. The use of OLED microdisplays should give ODG superior contrast which will further improve the perceived sharpness of the image. While not as apparent to the casual observer, but as I have discussed previously, OLEDs won’t work with diffractive/holographic waveguides such as Hololens and Magic Leap are using.
What is also interesting that in terms of resolution and basic optics, the R-8 with 720p is about 1/5th the price of the military/industrial grade 720p R-6 of about 2 years ago. While the R-9 in addition to having a 1080p display, has some modular expansion capability, one would expect there will be follow-on product with 1080p with a larger FOV and more sensors in a price range of the R-8 in the not too distant future and perhaps with integration of the features from one or more of the R-9’s add-on modules; this as we say in the electronics industry, “is just a matter of turning the crank.”