Subject: ghosting

From: Peter Brooks <[email-masked]>
Date: Wed, 5 May 1993 12:04:46 -0400

>     It seems that the shutters on the glasses are not darkening completely,
>resulting in 'residual imaging' to the left and right of the image being
>viewed.  I assume that others have experienced this as well, and I'm hoping
>that there's an inexpensive fix.
>
>     Any info would be appreciated.
 
Most of the ghosting that I perceive is related to the direction that the
light takes through the glasses.  The portion of the image that you see
when looking through the lenses perpendicularly should not present any
residuals.  But if you look through the lenses obliquely
(non-perpendicularly) you will see ghosting.  This has nothing to do with
timing of the LCD switching mismatching the timing of the display switch.
 
This is the same effect as look at your LCD watch non-perpendicularly and is
a property of LCD optics.
 
Try this experiment:
1. look at the image perpendicularly through the center of the LCD lens
(normal viewing practice): there should be no residuals
2. look at the image non-perpendicularly through the side of the LCD lens
(normal viewing practice): there should be residuals
3. shift the lens so that you look through the side of the LCD lens
perpendicularly (not normal viewing practice): there should be no residuals.
 
            |        |
eye  -----> | -----> |         (perpendicular viewing)
            |        |
           lens     display

eye       |        |
    \     |        |
      \   |        |        (non-perpendicular viewing)
        \ |        |
          |        |
          |  \     |
          |     \  |
         lens     display
 
The angle at which the light passes through the LCD is very important, and
that is why there appears to be ghosting near the edges of the lens.
 
Peter Brooks
MicroMind, Inc.