2D1-12
This article is a technical report without peer review, and its polished and/or extended version may be published elsewhere.

第 28 回日本バーチャルリアリティ学会大会論文集（2023 年 9 月）

Development of a Waterproof Virtual Reality
Head-Mounted Display: An Iterative Design Approach
Hiromu Otsubo1) , Johannes Schirm1) , Daniel Bachmann2) , Alexander Marquardt2) , Felix Dollack1) ,Monica Perusquı́a-Hernández1) , Hideaki Uchiyama1) , Ernst Kruijﬀ2) , and Kiyoshi Kiyokawa1)1) 奈良先端科学技術大学院大学 （〒 630-0192 奈良県生駒市高山町 8916 番地-5,{otsubo.hiromu.oj1, schirm.johannes.sh6, felix.d, m.perusquia, hideaki.uchiyama, kiyo}@is.naist.jp）
2) University of Applied Sciences Bonn-Rhein-Sieg (Grantham-Allee 20, 53757 Sankt Augustin, Germany,{daniel.bachmann, alexander.marquardt, ernst.kruijﬀ}@h-brs.de）
概要:

In an iterative design process, we developed a waterproof virtual reality (VR) head-mounted display(HMD) for underwater use. In an underwater environment, we can modulate proprioception toenhance immersion and engagement in VR. We target eliciting complex emotions, such as awe,during VR experiences. We detail the iterative development phases of a low-cost, underwater VR
HMD prototype, showing how each development cycle introduces, tests, and reﬁnes diﬀerent aspectsof the system. The ﬁnal prototype increased comfort and image quality. Future work should seek
to add a mechanism to adjust Interpupillary Distance.
キーワード： Virtual reality, Head-mounted display, Awe, Underwater, Overview eﬀect

1.

Introduction

tive change experienced by astronauts when viewing theVirtual Reality (VR) oﬀers immersive experiences thatEarth from space – is a compelling example for feelings ofcan evoke strong emotions [1]. Multisensory cues such asawe, connectedness, and a sense of vastness [7]. Previous

visual, auditory, and haptic feedback are commonly used

VR research has successfully simulated the overview ef-

to enhance user experience. However, the role of pro-

fect to induce awe, resulting in shifts in perception [8, 1].

prioceptive cues, related to the perception of body po-

However, most previous work focused on delivering au-sition and movement are less explored [2]. We propose

diovisual stimuli without other modalities.

manipulating proprioceptive cues to match the speciﬁc

2.2

Underwater VR Head-Mounted Displays

VR scenarios by immersing users in a pool while experi-HMDs that enable underwater VR experiences are help-encing VR. We present an underwater VR head-mounted

ful for underwater training and entertainment. Zhang etdisplay (HMD) prototype developed through an iterative

al. developed a low-cost, safe, underwater HMD [9]. Os-

design process. We aim to create immersive underwater

one et al. developed an underwater HMD that couldexperiences that can evoke feelings of awe. The uniquebe ﬁlled with water to reduce buoyancy. They adjusted

sensory stimuli of the underwater environmentcan poten-

the distance and angle between the lens and display totially enhance the emotional impact of VR and support

ensure a wide viewing angle even when water penetrates

the elicitation of emotional responses [3].

the HMD’s internal structure [10]. Building on this, Hatsushika et al. designed a wired underwater VR system

2.

Related Workfor scuba training to simulate various underwater condi-

2.1

Emotional Evocation and Awe in VRtions and scenarios [11]. Nagata et al. proposed a virtualEmotion is an essential factor in VR experiences. Awe

scuba diving system that leverages the sense of weight-

stands out as an emotion that evokes wonder and amaze-lessness underwater. Their system allows users to swim

ment, often triggered by encounters with the grand or

freely in a virtual undersea world, using a head tracking

sublime [4]. Typically, awe has two main components:

sensor and controller [12]. Finally, Sinnott et al. createdperceived vastness and the need for adaptation [5, 6].

an HMD incorporating a smartphone and lenses into a

In the context of VR, the “overview eﬀect” – a cogni-

full-face scuba mask. This design considered the ﬁt andⒸ 2023 日本バーチャルリアリティ学会-2D1-12-

2D1-12User(a)Smartphone inwaterproof caseVR headset frame(water inside)
VR headset frame(air inside)(b)

Swimming
goggles
Divinggoggles
Planar-convex
lens

(c)

Bi-convex lens

図 1: Comparison of underwater VR HMD prototypes: (a) Prototype 1, (b) Prototype 2, and (c) Prototype 3, showcasingwater-permeable and waterproof design ideas. Note: Prototype 3, initially designed as waterproof, experienced minor
leakage with a small amount of water entering the HMD, but without impacting the visual quality of the VR experience.

buoyancy of the mask and face, enabling users to experi-smartphone, and a custom 3D-printed holder for secureence VR in a state of neutral buoyancy underwater [13].

attachment, see Figure 1a. The VR experiencewas de-Although their study observed increased symptoms re-livered via a Unity application on the smartphone andlated to nausea, it was unclear whether this was due tobone-conducting headphones. A snorkel was used to let

the use of VR or the unique sensory environment under-the user breathe.

water.

3.

User Evaluation Three participants (one female, aged
33 to 37 years old) tested our HMD prototype and a com-System Design
We developed and tested an underwater VR HMD pro-totype iteratively. The tests were done in a pool with asimulated space scene.
3.1

Our HMD prototype presented the custom overview effect scene, while the commercial HMD oﬀered three experiences, “Space Odyssey”, “Deep Sea Dive”, and “At-Simulating the Overview Eﬀect

The VR environment was created using Unity 2021.3.6f1.
A 360° video of a space ﬂight was used for the visual
representation, giving users an unobstructed view of theearth and solar system. Users can freely explore the scene
by turning their heads underwater. For auditory stimuli,
we incorporated sound waves of the sun, obtained from
NASA1 to create a natural soundscape that supports thevisual experience of the space scene.
3.2

mercial underwater HMD2 in a public swimming pool3 .

lantis Exploration”, designed by the commercial HMD
vendor. The order of headset use was counterbalanced
among participants. Users were equipped with a ﬂoating
belt to keep their position ﬁxed in the water while stillallowing free movement. Additionally, a nose clip wasused during the testing of prototype 1. Each experience
lasted between three and ﬁve minutes.
Feedback and Discussion. Feedback indicated thatthe commercial HMD had a clear image and no need toPrototype 1

Our ﬁrst prototype was based on the work of Osone etal. [10]. Their approach assumes that the space between
the display and the lenses is ﬁlled with water. Regularswimming goggles with attached lenses facilitated underwater viewing. The image distortion caused by the waterlayers was corrected using plano-convex lenses with a diameter of 25 mm and a focal length of 25 mm. Our
prototype utilized a plastic VR headset frame for smartphones, a waterproof case to hold a Xiaomi 11T Pro

wear headphones (P1, P2), but its weight was noticeable,and using the snorkel was tiring for those unaccustomed
to it (P2). One participant anticipated motion sickness,but the ﬂoating sensation in the water helped to mitigate the eﬀect and improved the match between physicalsensations and the VR experience (P3).
For Prototype 1, all the participants found the visuals
clear but with a slight blurriness in the periphery. They
also expressed discomfort with the goggles and the nec-

1 https://www.nasa.gov/feature/goddard/2018/sounds-of-

2 https://www.ballastvr.com/divr

the-sun

3 https://www.stadtwerke-osnabrueck.de/nettebadⒸ 2023 日本バーチャルリアリティ学会-2D1-12-

2D1-12essary nose clip. This combination was less preferredthan the commercial HMD, whose goggles included anose cover. Overall, the quality of stimuli and usability
aspects of the ﬁrst prototype did not match the standards
set by the commercial system, indicating potential areas
for improvement. Furthermore, the Interpupillary Distance (IPD) was ﬁxed at about 6.5 cm because the lenses
were glued to the swimming goggles. The reported blurriness may be attributed to diﬀerences in participants’
individual IPD. Based on the discomfort reported withthe goggles, we decided to explore a diﬀerent type of gog-

図 2: Immersive view of earth from space in Prototype 2,gles for the next prototype.

showcasing the overview eﬀect on the integrated smartphone.

3.3

Prototype 2

Prototype 2 improved usability by utilizing diving goggles with an integrated nose cover (Figure 1b).

The

same lenses as in Prototype 1 were used to address image distortion caused by water. The headset remainedUser Evaluation Four participants (one female, aged
23 to 53 years old), including one who had tested theﬁrst prototype, tested the improved HMD in a researchpool. Participants wore a ﬂoating belt to maintain theirposition on the water surface while experiencing the same

standard biconvex VR lenses (42 mm diameter) were usedmal IPD was determined based on a collective assessment
from a group of experts (n = 4), using the HMD’s built-in
IPD adjustment. The waterproof isolation of the headset was achieved by attaching a 2 mm thick acrylic glass
to the headset frame and taping the connection to thediving goggles. While the remaining air inside the de-simulated overview eﬀect scene as in Prototype 1.
Feedback and Discussion. Participants were more
optimistic about the visual quality. Although not quiteachieving the clarity of the commercial underwater VR
device, Prototype 2 performed adequately for underwateruse (P1, P2). Users with corrected vision reported seeing
ﬁne details in the simulated space scene even though they
had to remove their glasses to put on the headset (P3).
While some participants experienced suﬃcient stereo perception despite incorrect IPD settings (P3, P4), this was
not the case for others (P1). The headset’s form factor was rated more comfortable than the ﬁrst prototype(P1, P4), which was improved by the nose cover (P2).
Finally, concerns were expressed about the need for interactive navigation (P3), and the fear of colliding with thepool walls or panicking because of losing contact with theground (P2, P4). Similar to its predecessor, Prototype
2 used plano-convex lenses with a short focal length anda ﬁxed IPD, causing geometric distortions and aﬀecting
the stereo eﬀect (Figure 3 - left). Chromatic aberrations
from the lenses slightly blurred the view. These issues

vice could aﬀect buoyancy, full underwater dive was not
required.
User evaluation Two participants (one female, aged
23 to 37 years old), including one who had tested the second but not the ﬁrst prototype, tested Prototype 3 in a
research pool.Participants were equipped with a ﬂoating
belt with two elastic ropes at the back, preventing themfrom drifting toward the sides of the pool. They experienced various custom-made awe-inspiring virtual scenarios (high mountain, waterfall, polar lights) as well as thespace scene with an overview eﬀect. Scene switching wasenabled by touching the smartphone in the HMD framewith an NFC tag.
Feedback and Discussion. Despite waterprooﬁng
eﬀorts, participants reported minor water leaks in theheadset frame. However, image quality remained unaffected, ensuring a mostly clear visual experience. The device also felt lighter due to higher buoyancy (P2). Users
noticed a mismatch between body posture and the virtual scene orientation, particularly noticeable in camera
motion scenarios. While one participant found the ﬂoat-

were noted for future improvements.

ing belt uncomfortable to wear (P1), the other partici-

Prototype 3

This iteration addressed visual artifacts caused by theplano-convex lenses when water ﬁlled the space between
the lenses and the display.

of particular lenses, as shown in Figure 1c. As a result,in this version. Instead of using average IPDs, an opti-unchanged.

3.4

ter from entering this space, which allowed the omission

To mitigate these issues,

the headset frame was made waterproof to prevent wa-

pant did not pay attention the traction force of the elastic ropes (P2). Among the virtual scenes, the mountainscene received positive feedback due to its animated locomotion path (P1), and the space scene harmonized wellwith the sensation of ﬂoating in the water.

Ⓒ 2023 日本バーチャルリアリティ学会-2D1-12-

2D1-12

The third prototype introduced improvements to mit-

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図 3: Comparing underwater image quality between Pro-totype 2 (left) and Prototype 3 (right) using a checkerboard pattern to evaluate sharpness, chromatic aberration, and optical distortion eﬀects. Note: The headset inPrototype 3 was ﬁlled with air.

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ings. Second, we could not address the issue of water
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Optimized hmd system for un-derwater vr experience.

5.

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14 International Conference, Tsukuba City, Japan,

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[13] C. Sinnott et al. Underwater virtual reality system

6.

for neutral buoyancy training: Development andAcknowledgements
This project was supported by the 2023 JSPS-DAAD

bilateral research program (JSPS #2023A023, DAAD
#57663726). We thank the Nettebad of the Stadtwerke
Osnabrück, Germany, for letting us use their facilities forour ﬁrst user evaluation.

Ⓒ 2023 日本バーチャルリアリティ学会-2D1-12-evaluation. Association for Computing Machinery,
2019.