[info] [Wearables] So, what *is* wrong with HITL/microvision?

[Eugen Leitl]

----- Forwarded message from Adam Oranchak <adam.sys at earthlink.net> -----

From: Adam Oranchak <adam.sys at earthlink.net>
Date: Tue, 08 Jan 2008 20:28:41 -0500
To: wearables-list at media.mit.edu
Subject: Re: [Wearables] So, what *is* wrong with HITL/microvision?
User-Agent: Thunderbird 2.0.0.6 (Windows/20070728)
Reply-To: adam.sys at ieee.org

Hello Robin:

Thanx for getting a little something started. I remember "in the day" 
when this list was the most impressive string of ACII I've ever seen!

Anyway, enough of establishing credentials...

Robin Lee Powell wrote:
> I remember, and I'm sure some of you do to, Back In The Day when
> HITL said they'd have full-resolution 24-bit colour in something the
> size of a grain of rice or whatever for a few hundred dollars.  IIRC
> "the day" was 1995 or so.
Well, you just stepped into a realm that I am intimately aware of. (Yes, 
you cheeky ones, I said "intimately!") It just so happens that all those 
specifications neglected to tell you that the image was crap, that if 
the display moved out of alignment from the wearer's eye by a millimeter 
off you lost half the image, that the corners were dark and 
pin-cushioned and that the 8 bits of red depth of one pixel appeared 
over the 8 bits of green produced by a pixel 10 pixels away. Oh yeah, it 
cost $20K.

Okay, maybe all of those don't apply to individual cases but most of 
them do.

In having said that, I am working closely with an academic institution 
that specializes in optics. My job is to take the optical realities of 
an optical solution for head mounted displays (HMD) and manifest that in 
a form that is "tuned" for the human experience of wearing it. That 
means it must be functional with impressive performance, comfortable, 
and not make you feel like a jerk wearing it. (2 out of 3 ain't bad!?)

Truth be told: I didn't know that much about optics back when I was 
fashioning a wearable computer out of a 386 laptop in a messenger bag  
with an NTSC monitor built into the strap. Now, our cell phones have 
100X the processing power and 25% the volume of the strap TV I used 
alone. I didn't understand what was so hard about getting a "proper" HMD 
to work. But, then again, I wasn't any more versed in optics beyond ray 
diagrams. For those of you who haven't gotten past that, let me tell 
you, the particle/wave paradox has major implications that are not 
easily grasped. I'm clinging by my finger tips.

Those of you who know me know, I'm on my 4th HMD for UCF ODA 
Labboratory. I've presented one of them at ISWC06 in Montreux. I was 
confronted with questions I was barely able to answer (as it should be).

Q:"Why is it so large?"
A: 8 bit color, 800x600, 20 degrees Field of View (FOV), 8mm pupil
BTW: These are not mutually exclusive. You don't know what pupil size 
is? Neither did I: One way, the easy way, to describe it is the opening 
in that the human iris closely approximates pupil size. In an optical 
system, as long as your eye's pupil is within the "exit pupil" of the 
optical system entirely, you see the image of the optic system entirely. 
Of course, ambient light comes into play. The human eye pupil can vary 
from 12 mm in bright conditions to a matter of mm's in dark conditions. 
(Did you notice that that the conditions that favors high contrast for a 
display are the kind disfavor pupil size?)

As I was fact checking, my colleague, Ozan Cakmaci,  wanted me to 
mention "Technically, magnifiers don't form exit pupils. However, when 
we set them up in raytrace codes, we still optimize them across a finite 
pupil size and that size was 8mm."

I think you are starting to get the picture, forgive the pun.  (I'm a 
sucker for a pun.)

Q:"What about holographic displays?"
A: Yes, very small but these are generally monochromic. When "color 
registration" is important these tend to fail to perform. There are 
other very interesting ways to utilize a holographic system in HMD's: 
patent pending... ..so don't ask. (the landlord/bank doesn't!)

Q:"How much does it cost?"
A: The single most expensive item in our BOM is the polynomial mirror. 
If you don't know what I'm talking about just ask on the list and I'll 
clarify. Otherwise, I'll assume you saw my poster in Switzerland. (If 
you weren't there: shame on you! That place was GORGEOUS!) That mirror 
is $1000 alone. It could be injection molded but the features are 
nanometer scale. Very sophisticated optics!

Q: "Why only 20 degrees FOV?"
A: I thought you said it was too large? (Okay, cheeky. But true!)
> Does anyone know what they've been doing all this time?  I've always
> kind of wondered, and thought I'd ask.
>
> -Robin
Robin, I'm glad you asked. I feel your frustration. I found myself in 
this place, designing HMD's, by way of a mysterious process. But, it is, 
as you have implicitly identified, the final barrier to wearable 
computing that most of us here have envisioned (let alone the 
soothsayers of science fiction). As electronics shrink to smaller and 
smaller. dimensions.. ..just as Saturday Night Live spoofed with the 
super-miniature cell phone... ...traditional button/touch screen 
interfaces will eventually fail to deliver a compelling experience... I 
propose, and many of you have heard this from me before, that the cell 
phone will take the form of a head mounted display. The convergence of 
the cell phone and the HMD, to me, is obvious.

Alright. Now. What do we REALLY want? How does one balance the competing 
demands of FOV, Color, Display Volume and Cost? And, I assume nobody 
wants to look like a jerk ;)

ciao,
adam.sys
_______________________________________________
Wearables mailing list
Wearables at mailman.cc.gatech.edu
https://mailman.cc.gatech.edu/mailman/listinfo/wearables

----- End forwarded message -----
-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
______________________________________________________________
ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org
8B29F6BE: 099D 78BA 2FD3 B014 B08A  7779 75B0 2443 8B29 F6BE