[Wear-Hard] On head mounted displays

[tetsu yatsu]

> >* The HeadPlay DOES carry a very decent 1024x768 XGA display. Xrandr
*> >* doesn't show modes for 1280x720 HD720p widescreen, so I haven't been
*> >* able to try it yet.
*> "carry" is an interesting word.  With 800x600 LCoS panels, it is pretty
> much a waste of processing power to send it anything more than that as
> the Liberator (cough, cough) has to down scale it back to 800x600 to
> display it.

I admit I haven't been able to get much technical information out of their
support staff yet, but I'm to the point I'm ready to tear it apart and look
inside. If you have more technical details (or a safer teardown guide) I'm
all ears.

> >* Complaints I've read about the headplay vary from the lame - 'this
*> >* isn't a movie theater on my head', to the mundane but interesting -
*> >* 'when I look to the sides I see dark spots?'.  There is a kind of mild

*> >* fish-eye distortion in the middle of your field of vision that could
*> >* get disorienting after a while, but more importantly the corners are
*> >* usually unreadable - and only readable with some eye strain. Edges are

*> >* not much kinder to the eye muscles.
*> That's the problem with a HMD that is targeted towards the consumer
> market.  Everything is subjective.  It's hard to get constructive
> feedback for further improvement development.

I've read recently reviews of the iGlasses comparing the use of
straight-line optics and prism optics. If it's the straight-line optics in
the Headplay that causes the outer-rim aberrations, I much prefer prism
optics (or larger lenses).
*
*> >* Darting your eyes too fast also shows an afterimage of each pixel's
*> >* color as it refreshes. I'm not sure why it seems to refresh one color
*> >* after another, if my refresh rate is really 1/3 of what they say.
*> You get this color breakup from any field sequential display.  Even
> though the LCoS might be refreshing at 120hz, the part of your eye that
> is sensitive to changes in contrast can easily pick that up.

I'd heard the word before while researching, the Headplay, but most reviews
were non-technical and often outright wrong. Though I've already spent the
money, I'd appreciate your technical critique of the device.

I've also read that it has one display, but I've also read that it has two
separately driven displays. Could you verify either claim, or help me figure
out how to open it to find out?

> >* But none of these things are problems if you are watching the center
*> >* of the screen. In fact, it might be better to focus your vision
*> >* forward, and use some means of moving data in front of your
*> >* accessible. Not just a headtracker to move your head around in a
*> >* fanciful 3d simulation world, but a headtracker to pan around a
*> >* desktop, or another method of bringing data to the front of vision. I
*> >* shouldn't have to reach my eyes to the corners of the screen to see
*> >* something. This will have to be part of my interface.
*> But that's not how we naturally view the environment.  We move our eyes
> first - they are the fastest things to move and they don't weigh much.
> If there is something interesting, we engage our neck muscles to move
> our much heavier head - bringing the scene into our Fovea for further,
> fine detail, processing.  Keeping everything in our fovea all of the
> time is not the way we view things naturally.
We both agree on this, it seems. I'm glad to have the word Fovea now.

Yes, the eye is good at darting back and forth, with relatively strong
muscles to so, but we don't often dart our eyes so far left or right that
our nose obstructs our vision. That issue is the border of the viewports,
and trying to look at the edges of the viewports, the optics get a little
fish-eyed. But, as I recall, the 'fovea' has our primary focus, and other
areas of our field of vision have different traits. The edges of our vision
are somewhat unfocused, unprocessed, used for detecting movement to adjust
our heads and bring the object into the main focus, and progressively worse
as you get further away form the center of vision.

My real goal is a wearable computer, so I'd want contextual information
displayed at the forefront of my vision. If I'm working on a piece of
electronics, or working on an engine, I will staring directly at the part
I'm working on. I don't want the information to be scrolling in a terminal
window or web browser in the far bottom left of my vision - where we tend to
progress information in computer systems. That works if you have a computer
monitor you can turn your head to the corners of. It's very irritating with
this head-mounted display.

I've tried using Compiz's Enhanced Zoomable Desktop plugin, and it fits the
purpose nicely. I can see what's pertinent in full focus in front of me,
eyes relaxed, and I can move the reference point wherever I want to see
other interesting artifacts worth viewing. My eyes can dart leisurely within
the zoomed frame to read blocks of text, or analyze images, but if there are
several thousand pixels in a corner somewhere very difficult to see at
full-range, I can zoom in - making the difference less noticeable. It really
makes all the difference. I only wish I could control it separately by
joystick and use a cursor within the zoomed frame.
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