From: mbernat@gel.ulaval.ca (Marc Bernatchez)
Subject: Re: TECH: HMD'S
Date: Wed, 27 Sep 95 18:30:03 GMT
Organization: dep. de Genie electrique


From: mbernat@gel.ulaval.ca (Marc Bernatchez)

In article <44982i$97g@nntp5.u.washington.edu>,
   jmelzer@aol.com (JMELZER) wrote:
>Excellent comments! You have nailed the problems exactly! HMDs should
>be purchased (or specified, or designed) based upon what you will do
>with them, not simply on the basis FOV and price! (These are the two
>features I hear people asking about routinely.)

Exactly my point. I took angular resolution, FOV and price and tried
to extract some helpful conclusions about it. Taking the angular
resolution, you evaluate the image quality whatever the FOV is. Taking
the FOV, you evaluate the immersion degree. So I tried to take both of
these two important issues plus the price to get an _approximate_
global index of some HMDs. I will never make my self clear enough
saying that it isn't a complete evaluation, I admit.  Neither is it a
highly rigorous scientific one. With time, I hope to change that in
future versions of the article.

>A surgeon may want narrow field of view, but with very high resolution
>and excellent color rendition.
>
>A pilot may want a wider field of view, but with higher resolution,
>but may accept monochrome. [...]
>
>A game player may want a wide field of view, but can get along with
>reduced resolution.

Yes indeed, it always depends on what your application is. For now,
LCD performances limit considerably HMD resolutions. In consequence to
this, we have to make big compromises on image quality (angular
resolution) and FOV.  This will hopefully be less of a concern as LCD
technology or other new technologies let us design HMDs having both
resolution and wide FOV. Then, maybe the calculations I made will have
more significance. With these new high performances HMDs, you will
look for the best value for the money. It will be less a concern of
the application you intend to use your HMD for since they will all be
usable for that application. Then, you will have to compare all these
models based on things such as angular resolution, etc.

>Please, do the entire industry a favor by refraining from just picking 
>an HMD based on field of view.

I recently had good comments and suggestions from Mr. Luis
Ramos-Izquierdo from n-Vision. I'm very pleased that he took time to
share some ideas with me and I thank him for that. I will take his
suggestions into consideration and include more factors such as image
focal plane location, field curvature, distortion, and HMD channel
angular alignment in a future update of my web page article on HMDs. I
will let you all know when it's ready.

Please continue to give me your feedback, thank you.

Regards,

== Marc Bernatchez         =                    E-MAIL                  ==
== C.O.P.L.(GEL plt-00307) =            mbernat@gel.ulaval.ca           ==
== Dep. Genie electrique   =                      or                    ==
== Universite LAVAL        =         marc.bernatchez@gel.ulaval.ca      ==
== Quebec, Canada          ===============================================
== G1K 7P4                 = Virtual Reality is the future of computers ==
== fax: (418) 656-3159     = http://www.gel.ulaval.ca/~mbernat          ==