Crossed half-silvered Mirror Array: Fabrication and Evaluation ofa See-Through Capable DIY Crossed Mirror Array
Kensuke Katori

University of Tsukuba, Japan
kenkenissocool@digitalnature.slis.tsukuba.ac.jp

Kenta Yamamoto

University of Tsukuba, Japankenta.yam@digitalnature.slis.tsukuba.ac.jp

Tatsuki Fushimi

Ippei Suzuki

University of Tsukuba, Japan
1heisuzuki@digitalnature.slis.tsukuba.ac.jp

Yoichi Ochiai

R&D Center for Digital Nature
University of Tsukuba, Japan
tfushimi@digitalnature.slis.tsukuba.ac.jp

R&D Center for Digital Nature
University of Tsukuba, Japanwizard@slis.tsukuba.ac.jp

Figure 1: (a) Retinal projection displayed on ChMA, with a physical object behind it. (b) Retinal projection displayed on CMA,
with a physical object behind it. (c) Optical setup for retinal projection. (d) Light path in CMA. (e)-(i) ChMA fabrication process.

ABSTRACTCCS CONCEPTS

Crossed mirror arrays (CMAs) have recently been employed insimple retinal projection augmented reality (AR) devices owing totheir wide field of view and nonfocal nature. However, they remain
inadequate for AR devices for everyday use owing to the limitedvisibility of the physical environment. This study aims to enhance
the transmittance of the CMA by fabricating it with half-silvered
acrylic mirrors. Further, we evaluated the transmittance and qualityof the retinal display. The proposed CMA successfully achieved sufficient retinal projection and higher see-through capability, making
it more suitable for use in AR devices than conventional CMAs.

• Hardware → Emerging optical and photonic technologies; Displays and imagers.

SIGGRAPH ’23 Posters, August 06-10, 2023, Los Angeles, CA, USA© 2023 Copyright held by the owner/author(s).
This is the author’s version of the work. It is posted here for your personal use. Notfor redistribution. The definitive Version of Record was published in Special Interest
Group on Computer Graphics and Interactive Techniques Conference Posters (SIGGRAPH’23 Posters), August 06-10, 2023, https://doi.org/10.1145/3588028.3603644.

KEYWORDS
augmented reality, retinal projection, fabrication process
ACM Reference Format:
Kensuke Katori, Kenta Yamamoto, Ippei Suzuki, Tatsuki Fushimi, and YoichiOchiai. 2023. Crossed half-silvered Mirror Array: Fabrication and Evaluationof a See-Through Capable DIY Crossed Mirror Array. In Special Interest
Group on Computer Graphics and Interactive Techniques Conference Posters(SIGGRAPH ’23 Posters), August 06-10, 2023. ACM, New York, NY, USA,2 pages. https://doi.org/10.1145/3588028.3603644

1

INTRODUCTION

Augmented reality (AR) devices can potentially replace smartphones
as it can offer a rich and immersive experience. However, AR devices
have challenges, such as field of view, eye box size, device weight,

SIGGRAPH ’23 Posters, August 06-10, 2023, Los Angeles, CA, USA

Katori et al.

Figure 2: (a) Transmittance experiment device setup. (b) The average luminance of transmittance experiment. (c) Retinal
projection result (1 mm pitch). (d, e) Retinal projection comparison between 1 mm pitch ChMA (d) and 2 mm pitch ChMA (e)display quality, and visibility of the physical environment. To address these challenges, studies have explored various approaches
including crossed mirror array (CMA). The CMA consists of micromirror array (MMA) grids [Yamane et al. 2015], which transfer theprojected image to a plane-symmetrical position as a distortion-freereal image (Fig. 1(d)). In 2018, Ochiai et al. utilized this property forretinal projection, which outperformed conventional AR devices[Ochiai et al. 2018]. However, CMA had insufficient visibility of thephysical environment owing to its low transmittance of the MMAs
(Fig. 1(b)).
This study aims to improve the visibility of the physical environment of a CMA by fabricating a crossed half-silvered mirror
array (ChMA) using half-silvered mirrors and optical adhesives.
The evaluation included a comparison of ChMA’s transmittancewith an off-the-shelf CMA and the assessment of the retinal display
quality using two ChMAs with different pitch sizes. The results
showed that the ChMA achieved higher transmittance and retinal
projection capabilities, improving the CMA’s drawbacks for AR
devices (Fig. 1(a)).

2 CROSSED HALF-SILVERED MIRROR ARRAY
2.1 Fabrication Process
Factors such as the mirror-coating ratio, pitch size, and plate thickness were considered during the ChMA design, along with processing capabilities and availability of adhesives with identical refractive
indices (RI) to pass light through the ChMA without refraction. For
this fabrication, half-silver mirrored acrylic plates (RI=1.49) andNorland’s NOA78 UV-curable optical adhesive (RI=1.50) were used(Fig. 1(e)). The acrylic was 5 mm × 80 mm (W × L) in size and 2 mm
thick and one side was half-silver coated. By stacking the plates together (Fig. 1(f)) and curing them using a 60 W UV lamp (Fig. 1(g)),
we fabricated an MMA (Fig. 1(h)). After two MMAs were fabricated,
the surfaces were polished (Fig. 1(i)) and positioned orthogonal toeach other to form one ChMA. The final ChMA was 9 mm thickwith a 2 mm pitch (Fig. 1(d)). The ChMA thickness was set to matchan off-the-shelf CMA (ASKA 3D plate; Asukanet Co., Ltd.), which
was 2 mm thick, with a 0.5 mm pitch and 100% silver mirrored glass.

2.2Transmittance Evaluation

We compared its transmittance with that of an off-the-shelf CMA.
The experimental setup is shown in Fig. 2(a), with d being set
such that the measuring range did not exceed the CMA at every

𝜃 , and the aperture of the luminance meter (SR-LEDW; TOPCONTECHNOHOUSE CORPORATION) was 2.0°. We then changed theangle 𝜃 from 0–65° and measured the luminance at every 5° change.
The experiment was repeated three times, and the average andthe standard deviation of the results is presented in Fig. 2(b). The
difference between the proposed CMA and the conventional CMA
is particularly evident between 30° and 45°. The proposed ChMA
remains transmissive, whereas the CMA has an almost negligibletransmittance. This is relevant as the CMA is typically set in therange of 30–50° for effective retinal projection (Fig. 1(c)).

2.3

Display Results

In addition, we examined the retinal projection capability of thefabricated ChMA. Because the retinal projection display quality
depends on the pitch size of the CMA, we fabricated another ChMA,
which was 5 mm thick, with a 1 mm pitch using acrylic half-silvered
mirrors. This ChMA performed better display quality than that of
the 2 mm pitch ChMA (Fig. 2(d), (e)), thereby indicating that thefabricated ChMA with an acrylic mirror performs adequately as aCMA.

3DISCUSSION AND CONCLUSION

This study aimed to enhance the visibility of CMAs by fabricatingthem using half-silvered mirrors as the MMA. The display qualityof the ChMA was limited due to processing difficulties, resulting
in black lines from air bubbles (Fig. 2(c)), indicating a need for improvement in future research. Despite this, the ChMA demonstrated
higher transmittance and retinal projection capability, making it
more suitable for AR devices. This study provides a solution to thechallenges faced in developing wearable AR devices and opens up
possibilities for everyday use.

REFERENCES
Yoichi Ochiai, Kazuki Otao, Yuta Itoh, Shouki Imai, Kazuki Takazawa, Hiroyuki
Osone, Atsushi Mori, and Ippei Suzuki. 2018. Make Your Own Retinal Projector: Retinal near-Eye Displays via Metamaterials. In ACM SIGGRAPH 2018
Emerging Technologies (Vancouver, British Columbia, Canada) (SIGGRAPH ’18).
Association for Computing Machinery, New York, NY, USA, Article 13, 2 pages.
https://doi.org/10.1145/3214907.3214910
T. Yamane, S. Maekawa, Y. Utsumi, I. Okada, and A. Yamaguchi. 2015. Fabrication andevaluation of Dihedral Corner Reflector Array for floating image manufactured bysynchrotron radiation. In 2015 International Conference on Electronics Packaging andiMAPS All Asia Conference (ICEP-IAAC). 436–439. https://doi.org/10.1109/ICEPIAAC.2015.7111052