Comparison of Simultaneous Measurement While Viewing Real
Objects and 3D Video Clips
Tomoki Shiomi
1
, Keita Uemoto
1
, Takehito Kojima
1
, Satoshi Hasegawa
2
, Masako Omori
3
,
Hiromu Ishio
4
, Hiroki Takada
5
and Masaru Miyao
1
1
Nagoya Univ., Graduate Sch. of Inf. Sci., Chikusa-ku, Nagoya, Japan
2
Nagoya Bunri Univ. Inazawa, Aichi, Japan
3
Kobe Women's Univ., Suma-ku, Kobe, Japan
4
Fukuyama City Univ., Fukuyama, Hiroshima, Japan
5
Univ. of Fukui, Fukui, Japan
Keywords: Accommodation and Convergence, Simultaneous Measurement, Real Object, 3D Video Clips.
Abstract: The use of 3-dimensional images has been spreading rapidly in recent years such as in 3D films and 3D
televisions. However, the influence of stereoscopic vision on human visual function remains insufficiently
understood. The public has come to understand that lens accommodation and convergence are mismatched
while viewing 3D video clips, and this is the main reason for the visual fatigue caused by 3D. The aim in
this study is to compare the fixation distance of accommodation and convergence in viewing real objects
and 3D video clips. Real objects and 3D video clips perform the same movements. We measured
accommodation and convergence in viewing real objects and 3D video clips. From the result of this
experiment, we found that no discrepancy exists in viewing 3D video clips like real object. Therefore, we
argue that the symptoms in viewing stereoscopic vision may not be due to the discrepancy between lens
accommodation and convergence.
1 INTRODUCTION
Recently stereoscopic images have been used in
various ways. In spite of this increase in 3D products,
and the many studies that have been done on
stereoscopic vision, the influence of stereoscopic
vision on human visual function remains
insufficiently understood. Investigations of the
influence of stereoscopic vision on the human body
are essential in order to ensure the safety of viewing
virtual 3-dimensional objects People often report
symptoms such as eye fatigue and 3D sickness when
continuously viewing 3-dimensional images.
However, such problems are unreported with so-
called natural vision. One of the reasons often given
for these symptoms is that lens accommodation and
convergence (Fig.1) are inconsistent during the
viewing of 3D images (Fig.2) (Lambooij, 2009).
Accommodation is a reaction that occurs due to
the differences of refractive power by changing the
curvature of the lens with the action of the musculus
ciliaris of the eye along with the elasticity of the lens.
The result is that the retina focuses on an image of
the external world.
Figure 1: Lens accommodation and convergence.
Convergence is a movement where both eyes
rotate internally, functioning to concentrate the eyes
on one point in the front. The main method of
presenting 3-dimensional images is through the use
of the mechanism of this binocular vision.
We would like to argue that a discrepancy
between accommodation and convergence does not
542
Shiomi T., Uemoto K., Kojima T., Hasegawa S., Omori M., Ishio H., Takada H. and Miyao M..
Comparison of Simultaneous Measurement While Viewing Real Objects and 3D Video Clips.
DOI: 10.5220/0004278405420545
In Proceedings of the International Conference on Computer Graphics Theory and Applications and International Conference on Information
Visualization Theory and Applications (IVAPP-2013), pages 542-545
ISBN: 978-989-8565-46-4
Copyright
c
2013 SCITEPRESS (Science and Technology Publications, Lda.)
exist, and we have already obtained results that
indicate the inconsistency between accommodation
and convergence does not occur in our previous
study (Miyao, 1996). In this present study, we
performed a more detailed investigations about
nonexistance of this discrepancy.
Figure 2: Discrepancy between accommodation and
convergence.
2 METHOD
We used an original machine developed by
combining WAM-5500
®
and EMR-9
®
to perform
the simultaneous measurements of accommodation
and convergence.
Subjects gazed in binocular vision at a real object
in natural vision (a Rubik’s cube) and then at a
virtual object of 3D video clips presented in front of
them. We measured their lens accommodation and
convergence (Fig.3). The objects viewed by the
subjects in natural and stereoscopic vision showed
exactly the same motion, and there were three kinds
of movements of these objects (Fig.4).
(1) The objects of natural and stereoscopic vision
moved forward and backward at a range from 0.5 to
1m with a cycle of 10 seconds. It was repeated four
cycles per single measurement.
(2) The second movement was the same motion as in
movement one, but the time of a single cycle of
movement was 2.5 seconds.
(3) The object in this movement approached the
subject. Initially, the position of the object was 1m
from the subject. The object moved forward to the
subject and stopped at the position of 1D, 1.5D, 2D
for each 10 seconds (D represents diopter).
A“diopter” is the refractive index of the eye lens,
which is an index of accommodation power. It
would be as follows 0D stands for infinity, 1D
stands for 1 m, and 2D stands for 0.5m.
Figure 3: The overview of this experiment process.
Figure 4: The movement of the object in natural and
stereoscopic vision. (1) First was a cycle of 10 seconds.
(2) Second was a cycle of 2.5 seconds. (3) Third was step
motion, the object stopped at 1D, 1.5D, and 2D for each
10seconds.
The measurements of the objects in both natural
and stereoscopic vision were taken three times per
one movement. The illuminance in this experiment
was 103 lx.
3 RESULT
The measurements for all subjects showed roughly
similar tendencies. Figures 5-8 shows the results of
movement 1 and 2, which is the moving object in
both natural and stereoscopic vision with a cycle of
10 seconds or 2.5 seconds.
In all figures, “accommodation” stands for the
focal length of lens accommodation, while
ComparisonofSimultaneousMeasurementWhileViewingRealObjectsand3DVideoClips
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“convergence” stands for the convergent focal
length, and “object” stands for the location of the
real object in natural vision or the position of virtual
image in stereoscopic vision.
In Fig.5 and 6, these figures showed that the
accommodation and convergence of subjects
changed in agreement. The change in the diopter
value occurred within a cycle of about ten seconds.
The values of accommodation in both figures were
1.6D when object at the point of 2D and these values
were 1D when object at the point of 1D. The value
of convergence almost agreed with the position of
the object.
Figure 5: The result of natural vision (a cycle of 10
seconds).
Figure 6: The result of stereoscopic vision (a cycle of 10
seconds).
Figure 7: The result of natural vision (a cycle of 2.5
seconds).
In the case of movement 2 and 3, lens
accommodation and convergence almost agreed with
the position of the virtual images though the focal
point of accommodation often shifted to the far point
slightly.
Figure 8: The result of stereoscopic vision (a cycle of 2.5
seconds).
4 DISCUSSION
According to Hoffman et al. and Ukai and Howarth
(Ukai and Howarth, 2008), lens accommodation in
viewing 3D images would be fixed at the position of
the display. They have reported that an
accommodation-vergence mismatch can create
problems such as eyestrain and visual discomfort
due to the synergy between accommodation and
convergence. However, our experiment found no
mismatch between accommodation and convergence.
In our previous study, we also reported the results of
simultaneous measurement of lens accommodation
and convergence while subjects viewed objects in
stereoscopic vision, and the inconsistency between
accommodation and convergence did not occur
(Hori et al., 2011). This study simultaneously
measured accommodation and convergence in
viewing 3D video clips of three movements, and the
discrepancy was unconfirmed as in viewing real
object. Therefore, we found that subjects watching
3D so not show any discrepancy between
accommodation and convergence.
Subjects should be seeing blurred images if lens
accommodation focuses on the virtual image
position while a stereoscopic image project outwards.
Subjects focusing on a nearer position rather than
the display may be experiencing the condition in
which humans look at a position beyond the farthest
point of the object as in myopia.
Smith showed that the relationship between the
refractive error and visual acuity is linear (Smith,
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1991). The visual acuity of subjects in Smith’s
experiment did not decrease much. Therefore, the
distance from an emerging object in our experiment
may not have been a problem and was correctly
viewed by subjects.
Meanwhile, Patterson reported that there should
be a problem in only a near-eye display and that the
accommodation-vergence mismatch likely would
not occur under most stereoscopic display viewing
conditions because of the depth of field (Patterson,
2009). Patterson (2009) and Wang and Ciuffreda
(2006) found that the depth of field was large, and
they stated that the average total depth of focus was
on the order of 1.0 diopter (Wang anda Ciuffreda,
2006). Based on this value, the range of total depth
of field would be from a distance of about 0.1m in
front of a fixed point to about 0.17m behind the
fixed point of 0.5m. For a fixed distance of 1 m, the
total depth of field would be from a distance of
about 0.33m in front of the point to about 1.0 m
behind the point. For a fixed distance of 2 m, the
total depth of field would be from about 1m in front
of the point to an infinite distance behind the fixed
point.
They also reported that the depth of field was
affected in various ways by the pupil diameter and
resolution.
Some researchers found that pupil diameter will
be slightly over 6 mm for a luminance level of
0.03cd/m2 and near to 2 mm for a luminance level
of 300cd/m2. For each millimeter of decrease in
pupil size, the depth of field increases by about 0.12
diopters (Patterson, 2009).
Therefore, the value of accommodation can be in
the range of the depth of field in our experiment.
In the future research, we plan further
investigations concerning the influence of age, pupil
diameter, the illuminance of the experimental
environment, and the luminance of visual targets.
5 CONCLUSIONS
In this experiment, we simultaneously measured
accommodation and convergence of subjects
viewing real object and 3D video clips that showed
exactly the same motion as in real objects. We did
not confirm the existence of discrepancy between
lens accommodation and convergence. Therefore,
we believe it is inconclusive that symptoms such as
eye fatigue and 3D sickness are not caused by this
discrepancy but other factors. We plan to perform
further investigations and studies of other variables.
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