T3D Re: acuity enhanced with binocular vision

[Jim Crowell <crowell@xxxxxxxxxxxxxxx>]

At 7:23 AM -0800 3/18/98, John W Roberts wrote:
>
>>Binocular Enhancement of Visual Acuity.  Ron Cagenello, Aries Arditi, & D.
>>Lynn Halpern.  Journal of the Optical Society of America A, vol. 10, #8,
>>1993, pp1841-1848.  Using both eyes as compared to one, perception of
>>contrast increases by 40 to 50 percent...
>
>Thanks for bringing this to our attention - I thought it was very
>interesting.
>
>>The published test measured acuity, using block letters on a computer
>>monitor and a Stereographics stereo display program...
>
>It seems a little strange that they would use a sequential frame LCS stereo
>display as the source, as this introduces possible issues of phosphor decay
>rates/flicker, time disparity between peak brightness of left and right
>images, differences in electrical performance of glasses or monitor depending
>on what's shown, spatial separation of red, green, and blue pixels,
>reflections, and the extreme difficulty of *accurately* measuring contrast
>ratio on small features on a CRT. In other words, to the original issue of
>human visual perception, they've added a number of display issues and
>issues relevant to the human perception of CRT displays in particular.
>Visual perception and display characterization are both large, complex
>fields, which makes it doubly difficult to acquire sufficient expertise
>in both fields. Did the paper discuss any methods used to allow for
>display-related issues?

Yes, basically one would want to know the frame rate and the viewing
distance, which presumably are given in the article.  Ideally, you'd want
the frame rate to be above 60 hz or so & the smallest features to cover
several pixels (i.e. you'd want the viewing distance to be sufficiently
large)...

>Note: There's no doubt that a test of this kind can measure with complete
>accuracy the visual response to a Stereographics display system. The question
>is how closely that will correlate to visual response for other display
>systems, paper cards, real-world situations, etc.

My guess is that these effects would be quite small compared to the range
of inter-individual variability & the variations caused by the experimental
manipulations.  The thing you'd really want to worry about would be that
the display effects be equivalent between monocular & binocular conditions,
i.e. what exactly did they do to create the monocular images (replace the
target in one eye--e.g. on alternate frames--with a uniform background,
maybe?), & could it have affected the display quality in those conditions
relative to the binocular conditions...

-Jim C.



----------------------
Jim Crowell
Caltech Division of Biology
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