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C
r C
θ C
B
D
r A
θ B
θ D
A
θ A
r B
r C
r A
w L
w R
L
b 0
R
Figure 3.17 Diagram to calculate r stereoscopic acuity
want to increase this field while maintaining a sufficient screen resolution, we will have
to display a huge number of pixels which is not compatible with current technology.
The average value (1 minute of angle) of visual acuity must be referred to in order to
judge the resolution quality of a screen used in a VR device.
Human vision has the capacity to detect a difference in depth between two planes
(order of magnitude: at one meter, we can perceive a difference in depth of even one
millimetre). This stereoscopic acuity is expressed in angles. Stereoscopic acuity has
been defined in Figure 3.17.
The eyes, separated by IPD
b 0 and at L and R positions, converge to point B.
How will point A and C, which are in front of and behind point B, be perceived and
what will the minimum detectable difference r A and r C be? We assume that the
view is direct and that the object is far enough. We put W L
=
=
W R
=
w . This means that
angle LBR
=
θ B
=
angle LDR
=
θ D
=
θ . Considering triangles LAR and LDR, we can
say that:
θ A
=
θ
+
w and θ C
=
θ
w . Angle w is small, thus tg ( w )
=
w
=
BD/ r B and consid-
ering triangles LAR and BAD, with distance BD
=
l we have:
b 0
l =
r A
r A =⇒
r A = l r B r A
b 0
(3.1)
r B w
r A =
(3.2)
b 0
+
r B w
 
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