Super stereoscopy 3D glasses for more realistic 3D vision

Abstract

This paper introduces a new major twist on stereoscopic displays, where users suffer less from the accommodation-vergence con-flict with the help of improved monocular parallax. Our method provides two different views to each eye by using special aper-tures equipped with color filters. The design can be embedded into conventional stereoscopic glasses or special contact lenses. Subjective tests verified that the accommodation-vergence conflict is avoided to a large degree. The technique is also applicable to multi-view 3DTV displays in general.

Full text

SUPER STEREOSCOPY 3D GLASSES FOR MORE REALISTIC 3D VISION
Kaan Aks¸it, Amir Hossein Ghanbari Niaki, Osman Eldes, Hakan Urey
Koc¸ University, Department of Electrical Engineering, Istanbul, 34450, Turkey
ABSTRACT
This paper introduces a new major twist on stereoscopic displays,
where users suffer less from the accommodation-vergence con-
flict with the help of improved monocular parallax. Our method
provides two different views to each eye by using special aper-
tures equipped with color filters. The design can be embedded
into conventional stereoscopic glasses or special contact lenses.
Subjective tests verified that the accommodation-vergence conflict
is avoided to a large degree. The technique is also applicable to
multi-view 3DTV displays in general.
Index Terms —Super Stereoscopy, Accommodation-vergence
conflict, Monocular parallax, Rotating Screen, Pinhole Glasses
1. INTRODUCTION
The main drawback of conventional stereoscopic and autostereo-
scopic displays is absence of monocular parallax. Next gener-
ation autostereoscopic displays [1] can be expected to solve the
accommodation-vergence conflict [2] where the viewer’s focus is
at the screen instead of the spatial position of three-dimensional
(3D) content in the real world. Autostereoscopic displays with a
solution to the both problems are classified as Super Multi View
(SMV) displays [3], [4]. SMV display provides high number of
images with narrow interval of parallax to overcome the men-
tioned problems [2], [3], [5]. Therefore, such designs require high
density of views and pixels with great level of optical complexity.
This paper introduces a new technique for glasses type stereo-
scopic displays, where users’ accommodation vergence conflict
problem can be reduced. Our solution proposes using special aper-
tures in front of the user’s eye. Unlike conventional stereoscopy,
our initial implementation provides four different perspectives by
employing pinhole size Anaglyph type wavelength bandpass fil-
ters to satisfies the SMV region criterion [3] providing monocular
parallax. This new method is named as Super Stereoscopy 3D
(SS3D). Through subjective tests, we have shown depth percep-
tion and eyes vergence can be enhanced with our method. Due to
the nature of apertures, the visible disadvantage of our method is
a decrease in intensity perceived by the viewers.
2. SUPER STEREOSCOPY TECHNIQUE
Conventional SMV displays produce narrow viewing slits by hav-
ing a narrower angular spread than a single eye [3], [5]. SMV
region criterion is met when at least more than one perspective is
fed to a single eye which is known as monocular parallax. Same
assumption is valid for the case of stereoscopic displays. SMV re-
gion criterion can be expressed as a mathematical formula through
equation 1 representing angular parallax interval, in which deye is
the eye pupil size varying between 2-8 mm [6] and dvrepresents
the distance between the viewer and the three dimensional (3D)
object. Assuming a 5 mm eye pupil with an 3D object at 570 mm
Figure 1. Sketch showing how a voxel is perceived with (a) a conventional
stereoscopic glass (b) our proposed SS3D design
from the viewer, an angler parallax interval of ∆θ≤0.5degree
is required using equation 1.
∆θ≤deye
dv
(1)
Figure 1 provides a comparison in between our method and
the conventional stereoscopy, in which dIP D represents interpupil-
lary distance (60-70 mm). A careful reader can easily notice the
dramatic decrease in perceived voxel volume with the help of
SS3D glasses. There are three different common types of stereo-
scopic glasses to separate left and right eye, which are passive
polarization glasses, anaglyph glasses, and shutter glasses. One
can use one of these techniques as a basis to separate the eyes
from each other, but combination of these methods with the pro-
posed technique can provide number of views per eye. Remaining
accommodation-vergence conflict problem in conventional stereo-
scopic glasses can be easily enhanced by embedding an aperture
in front of the wavelength band-pass filters. Thus, a reader eas-
ily realizes other combinations can also be beneficial to provide
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natural 3D perception through monocular parallax.
The voxel shapes and sizes differ from each other when con-
ventional system is compared with our proposal. Using ray-optics,
a conventional stereoscopic display’s voxel size can be formalized
in terms of width wcand height hcshown in Figure 1. As an
examplary, deye = 6 mm,dI P D = 65 mm,ds= 500 mm,
dv= 500 mm,doff = 65 mm will lead to wc= 3 mm, and
hc= 42 mm. On the other hand for this example the values
are wb≈0.3mm and hb≈0.3mm which shows a substantial
decrease in voxel dimensions.
3. ROTATING AUTOSTEREOSCOPIC DISPLAY
We tested the SS3D concept using autostereoscopic display sys-
tem developed in our lab. As illustrated in Figure 2, the system
contains a transfer screen which is composed of a retro-reflective
surface and a 1D light diffuser, two pico-projectors, a camera for
head-tracker, and a servo motor to rotate the transfer screen. The
transfer screen is a retro-reflective linear light diffusing screen.
Each of two pico-projectors projects one perspective of stereo im-
age onto the transfer screen. The projected images from the pico-
projectors are retro-reflected back to the projectors and create two
viewing zones which overlap with MEMS scanner of picoprojec-
tors, as seen in Figure 2. 1D light diffuser in the transfer screen
diffuses retro-reflected light with a larger diffusing angle in verti-
cal direction than in horizontal direction. Due to the vertical dif-
fusion of light, viewing zones are vertical slits centered with the
MEMS scanner of pico-projectors. If two projectors are placed
horizontally apart from each other by interpupillary distance, then
viewing slits are also apart from each other by the same distance.
By looking through these viewing slits, a viewer sees the left im-
age by his left eye and the right image by his right eye, and per-
ceives 3D image. The 1D Light diffuser allows viewer to move in
vertical direction without losing 3D image perception. However,
if the viewer moves in horizontal direction, he loses 3D percep-
tion. In order to overcome this problem, we added pupil tracker
to change the slits’ angle in order to preserve the viewer’s 3D vi-
sion using OpenCV through python coding language. Detailed
information about the screen can be found in our group’s related
journal article [7].
Figure 2. The rotating screen used during the test, which shows (a) a
user wearing the special glasses, (b) pico-projectors (c) in-house built au-
tostereoscopic display [7] with the 1D diffuser attached on it, and (d) the
user-screen distance
Figure 3. Photograph of the SS glasses used in autostereoscopic displays
with (A) slit and (B) pinhole apertures.
4. EXPERIMENTAL TESTS
The proposed method was tested with our in-house made aper-
ture equipped glasses, with color filters detached from conven-
tional anaglyph type glasses. Instead of using regular stereoscopic
glasses to separate the left and right eye’s content, we used our in-
house built screen [7] which has the capability of separating left
and right image information with no difficulty. Figure 3 shows
the image of glasses built in-house for the setup in which the slit
version has 10 slits per eye with a slit width of 1 mm and center to
center distance of 1.8 mm, and the pinhole version has 6×10 pin
holes with a diameter of 0.8 mm and a center to center distance of
1 mm.
Subjective test was conducted to investigate the proposed tech-
nique. A photograph of the test bench is showed in Figure 2 which
the distance between the user and the screen is fixed at 100 cm
through the tests. The subjects where chosen randomly among
the university students and staffs. All the participants were young
and were not using correction for their vision. In each case the
users were first shown same standard images in order to see if the
subject were experienced enough to distinguish a 3D image, to
calibrate the white balance, and to apply the required alignment
due to differences in their IPDs. All the images shown in the test
were static 3D images.
Viewers were asked to estimate the distance of 3D objects in
the shown content. All images contained a reference point at in-
finite distance, which is used to register stereo pair correctly. Ad-
ditionally, each image contained three different objects at differ-
ent distances which two of them (the right pumpkin and the car-
toon character) were fixed and one of them (the big pumpkin) was
shown in different distances. Note that all of the images were cre-
ated in-house using open-source 3D models in Blender rendering
software. Figure 4 shows the estimated distances by testers with
different contents. Only 13% of subjects could perceive the most
extreme content as 3D before using SS3D glasses, but with the

Figure 4. (a) Estimated distance by testers with different contents. (b)
Right eye content of the object (pumpkin) at 36 cm (c) Right eye content
of the object (pumpkin) at 48 cm. The image of the cartoon character
appears on the screen at 1 m from the user
help of our purposed 3D glasses this number increased to 100%.
Major observed drawback of SS3D glasses during the test was
found to be a decrease in brightness of the screen by testers. An-
other possible problem was resolution due to pinhole diffraction
nature. As the distance between the viewer and the display in-
creases, the pinhole or the alternative slit structure limits the small-
est resolvable spot size to about 0.3 mm (at 500 mm subject dis-
tance). This is consistent with the geometrical calculations given
in section 2.
5. CONCLUSION
A new method entitled as Super Stereoscopy Technique was pro-
posed to enhance the capabilities of stereoscopic displays, and
multi-view autostereoscopic displays. The method provides a so-
lution via improved monocular parallax to a common problem in
stereoscopy domain, accommodation-vergence conflict, and shrinks
dramatically the voxel dimensions via changing its shape. The
method was demonstrated by using an in-house built multi-view
autostereoscopic display.
Our implementation provides two different perspectives to each
eye by employing wavelength band-pass filters used in Anaglyph
type glasses. Through subjective tests, the method was found
to improve the depth perception, and to solve accommodation-
vergence problem. By means of our SS3D glasses, 100% of sub-
jects who were not able to perceive the most extreme contents
were seeing 3D easily. Major drawback of the method is a de-
crease in perceived light intensity by users. This technique is gen-
eral and can be used in 3D cinemas and 3DTV glasses as well as
wearable displays.
6. ACKNOWLEDGEMENT
Financial support from ERC Wear3D Project No: EC.00062 and
T¨
UB˙
ITAK Project No: 111E183 are gratefully acknowledged.
7. REFERENCES
[1] E. Erden H. Urey, K. V. Chellappan and P. Surman, “State of
the art in stereoscopic and autostereoscopic displays,” Pro-
ceedings of the IEEE, vol. 99, pp. 540–555, 2011.
[2] Y. Takaki and N. Nago, “Multi-projection of lenticular dis-
plays to construct a 256-view super multi-view display,” Op-
tics Express, vol. 18, pp. 8824–8835, 2010.
[3] H. Yoshikawa Y. Kajiki and T. Honda, “Hologram-like video
images by 45-view stereoscopic display,” in in Proc. SPIE,
1997, pp. 154–166.
[4] K. Tanaka Y. Takaki and J. Nakamura, “Super multi-view
display with a lower resolution flat-panel display,” Optics Ex-
press, vol. 19, pp. 4129–4139, 2011.
[5] J Nakamura, K Tanaka, and Y Takaki, “Accommodation re-
sponses to horizontal-parallax-only super-multiview display,”
in IS&T/SPIE Electronic Imaging. International Society for
Optics and Photonics, 2013, pp. 864818–864818.
[6] SG De Groot and JW Gebhard, “Pupil size as determined
by adapting luminance,” JOSA, vol. 42, no. 7, pp. 492–495,
1952.
[7] Osman Eldes, Kaan Aks¸it, and Hakan Urey, “Multi-view au-
tostereoscopic projection display using rotating screen,” Op-
tics Express, vol. 21, no. 23, pp. 29043–29054, 2013.