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Basic Physiological aspects — objective and measurable properties.
Blue is a cool colour - here it represents the measurable properties,
the more or less objective characteristics of the eyes, in short, the
physiological aspects.
Physiological
UON Aspects
narrow bases.
The ANATOMY of the Eye signifies itself most clearly
for photo-interpretation in the Interpupillary
Distance (ToD.); the eye-base. This straight forward
anatomical property is well known, but do designers of
stereoscopes know the average value and the spread
among a population? It is 64 * 9 mm, which requires an
adjustment range of 55 —- 75 mm on the instrument, as
large values are more likely to be found than the very
And what is the significance for instruments that white military truck-
drivers on the average have a 3mm smaller eyebase than their black
colleagues? (Damon 1966).
Other ergonomic points are the natural line of sight, and the normal
viewing distance,
[some relevant properties in this group:
Position of the eye's entrance pupil (12 to 15 mm inwards)
Natural line of Sight (horizontally to 45° downwards)
Field of view for easy viewing (0.7 rad, somewhat smaller for colour)
Distribution of Rods and Cones on retina (Rods along the outer edges,
cones at the central fovea)
Normal viewing distance (250 to 350 mm, depending on age)
7.
- uv.
Physiological
Aspects
The card "INVOLUNTARY EYE MOVEMENTS" emphasizes the perpetual state
of unrest, which is basic to any feedback system: small
oscillations around the wanted position, for example
directional vibrations as Tremor, Drift, Flicks and
Saccadic eyemovements which occur in connection with
convergence and fixation. In a similar manner,
accomodation is maintained continuously, with a
continual fine adjustment of the eyelens' curvature.
With the introduction of stereo colour photographs, the old solution
of flickering lights and a rotating disk in front of the eyes is applied
again on projection plotters. Now, is it sure that in this case stereos-
copie measurements are not impaired by ihe involuntary eye movements?
Signals from both eyes do not arrive simultaneously at the brain, there
can be à disturbed fusion,
