Leaked Light Field:
The Design Method for Natural Material to Display Surface
Kazuki Takazawa∗
Digital Nature Group
University of Tsukuba
Ibaraki, Japan.

Kenta Suzuki†
Digital Nature Group
University of Tsukuba
Ibaraki, Japan.

Yoichi Ochiai‡
Digital Nature Group
University of Tsukuba
Ibaraki, Japan.

Figure 1: Left: Our novel method make the everyday materials such as wood or stone to display surface. Center: Mirror based pinholedisplay that is indicating the time. Right: Example of replacing wearable device with wood grain display.

Abstract
In this paper, we will take a section on the design method for blending the display into everyday materials that could not be realizedwith conventional displays. Due to popularization of IoT in recentyears, the use scene of display has been greatly expanded. Meanwhile, as for the material of the surface of the display, transparency
and smooth things such as glass and plastic have been limited fora long time. In this paper, we aimed to improve weak points in thedesign aspect of display.

1

Introduction

Most of everyday materials around us such as wooden plates andmirrors have not been used as displays. Until now, most displays
including liquid crystal displays had to transmit the light of the lightsource on the back through color filters and liquid crystals, so thesurface material was limited to transparent and smooth materials
like glass and plastic it has been. However, since such materials do
not have the ability to express the texture of the surface, if embedded in everyday materials existing around ourselves, it damages thesurrounding atmosphere. In order to overcome the disadvantages ofthis display, we propose a design method to display almost all materials normally existed in our surroundings such as wood, stone,mirror etc. as well as glass and plastics.
With the new display design method we propose, we can display
anything that can be processed into thin plate like wooden plate,stone material, leather. The surface material molded into a plateis subjected to minute hole processing by machining or laser processing to create a gap for allowing light rays to pass through. By
observing the light from the light source placed behind the material,
it becomes a display. It is very difficult to visually recognize minuteholes that have been opened in this plate material, so when the lightsource is off, it does not damage the texture of the original material
at all. Since it functions as a display only when the light source
switch is turned on, the living space can be further expanded. We∗ e-mail:1220kazu1412@gmail.com† e-mail:Ikuzus.atnek.0626@gmail.com‡ e-mail:wizard@slis.tsukuba.ac.jp

believe that if we can integrate displays naturally into parts of human life we can extend the possibilities of design. By adding thisfunction to the display, we can blend the display on the floorboards,furniture, walls etc. that exist around ourselves.
In this display, since the light source is observed through the pinhole, it is possible to present the light field according to the positionof the observer. Due to this, it is possible to project different images to two or more observers. Furthermore, if parallax images arepresented for the position of the right eye and the position of theleft eye, autostereoscopic vision in the parallax barrier system canalso be realized. By adding these functions to everyday materials, it
becomes feasible to realize interactions in which images are ejectedfrom furniture that could not be realized in the living space so far.
Various application examples were presented utilizing this property.

2Related Works

Conventional studies on light field display methods such as parallax
barriers have tried to establish stereoscopic 3D on opaque materials. For a more complete overview of state-of-the-art 3D display
technology, see [Masia et al. 2013].

2.1

Light Field Display

Although more than 100 years have passed since the developmentof a parallax barrier type display in 1903, this technique is still frequently used even now [Ives 1903] . Most of recent researches onparallax barrier method aim at improving display quality. Many of
those studies are considering changing the content to be displayedand designing the barrier. Isono et al . are studying expansion ofstereoscopic display range by parallax barrier by using liquid crystal display as parallax barrier in 1993 [Haruo et al. 1993].The ideaof light field starting from Integral Photography advocated by Lippmann in 1908 also caused a big change in display research [Lippmann 1908].

Kazuki Takazawa:Leaked Light Field

(a)

(b)

2(c)

(d)

Figure 2: (a) and (b) show the profile of the femtosecond laser used for processing. The circularity is 87%, and the wavelength at thefocal point after passing through the lens is 1044 nm. 68 µmin the lateral direction and 59 µmin the longitudinal direction. Since energy
is concentrated in a very narrow range, thermal denaturation to the surroundings can be minimized. (c) Laser processing by CO2 laser
processing machine. Processing with CO2 laser causes strong heat denaturation, so it is not suitable for processing to materials like mirrors.
(d) State of the surface of leather material after pinhole processing. Even after applying pinhole processing, texture of the material can be
expressed without discomfort.

2.2

Display Fabrication Method

Various methods have been proposed for methods of fabricating displays, such as making them with multiple layers and processing thedisplay surface. Bell et al . are making displays that actually overlay two LCDs and create front and back relationships on the display and perform 3D display [Bell et al. 2008] . The method ofreproducing the actual light field with multiple layers to create astereoscopic display of still images was developed by Wetztein etal . In 2011 [Wetzstein et al. 2011] . In this study, we reinvent theparallax barrier method using a pinhole array on a non-transparent
material, such as wood or stone. We are able to make this function
as a three-dimensional display that does not destroy the feel of thesurface material.

2.3

Pinhole and Picture

There are many researches using pinholes for displays and cameras. Text describing the optical behavior of the pinhole is written
by Ian Stephenson [Stephenson 2005] . Coded lens using pinhole
instead of lens array to reconstruct the light field mentioned above
was proposed by Seikikawa et al [Sekikawa et al. 2014] .

2.4

Purpose of This StudyIn the past, displays have evolved in fields such as resolution,stereoscopic effect, and entertainment. However, in either case, discussion on the material of the surface of the display has not beenproactively carried out. In a patent filed in 2012 by Apple Inc., using a pinhole to make a display that does not affect the surface, thishas not yet been applied to products [Pance and Tice 2014]. Therefore, in this research, we will describe in the present study how todisplay materials by holding the texture of the surface material, andwhat kind of interaction can be obtained thereby.

3Implementation

3.1

Material Properties

Pinhole is a clamp hole opened in an object, starting with a camera brass and used as a method of shooting and projecting images
such as cameras and displays from long ago. In this study, we use
the property that pinhole is extremely difficult to observe with thenaked eye with the naked eye.It is almost impossible to observe a
perfect hole of about 100 µmto 250 µmwith the naked eye of a hu-Table 1: Material Properties
Material
Wood (B)
Stone (A)Genuine leather (D)Synthetic leather (E)Mirror (C)Number of pinhole
520(26 × 20)
520
19,200(160 × 120)
520
19,200

Diameter
200µm
200µm
200µm
200µm
100µm

Processing method
DrilledDrilled
CO2 Laser
CO2 Laser
Femtosecond Laserman being, but when the ray passes We think that we can propose anew display which was not so far by utilizing the pinhole as a newprotein of the display with this property having sufficient size to do.
We fabricated four kinds of pinhole displays as wood grain material,stone eye material, mirror, leather material as the surface materialof the display. Both laser and machining were used for processing
the display. By changing the processing method according to thematerial, simpler processing can be performed at lower cost. The
pinhole of the mirror and the pinhole of the leather material weremade by laser processing. Wood grain material and stone eye material were manufactured by machining with a drill. The size ofthe pinhole varies depending on the processing method. Machining
can be done with a size of 200 µmor more, and in laser processing it is possible to drill holes as small as 100 m at minimum. For
wood grain materials and stone eye materials which are thick inmaterial, machining is used because processing with laser is difficult. A thin and soft leather material and a thin film mirror weredrilled by laser processing. We used two types of processing using
CO2 laser for laser processing with leather material and processing
with femtosecond laser for mirror[?]. We chose machining with afemtosecond laser which is expensive but does not cause heat denaturation because it affects the surroundings of the processed partby heat if normal laser processing is done on a mirror-like material.
When comparing the results of each processing with enlargement,
there was a difference in processing accuracy. The shape of the machined pinhole is slightly irregular and the edge of the hole is notsmooth. Even with laser processing, it can be seen that the shape isdistorted although not as much as machining. For wood grain materials and stone eye materials which are thick in material, machining
is used because processing with laser is difficult. Processing by
femtosecond laser is a beautiful perfect circle and the edge of thehole is finished smoothly. The profile of the femtosecond laser usedis shown in Figure 2 . It may be considered that there is a problem
in optical design that the edge of the pinhole is not smooth. However, since the diameter of the pinhole due to machining by pinhole
and CO2 laser processing is 200 µmor more which is sufficiently
longer than the wavelength of light, it can be considered that thereKazuki Takazawa:Leaked Light Field(a) Mirror pinhole display

3Laptop PC(b)(c)

Target object
kinectmeasurement(d)Figure 3: A more interactive application can be realized by configuring the system using the depth camera. (a)(b)(c) By connecting the depth
camera, the laptop PC, and the mirror pinhole display as shown in the figure, it is possible to change the display by detecting in real time
what appears on the mirror. (d) By doing this, you can realize an augmented reality display that can follow not only the observer but also themovement of the target object (Infinite AR).

is almost no influence due to rough edge.

3.2

Display Configuration

The display we propose consists of two layers, LCD which is alight source of pinhole and pinhole array processed by the above
process. The LCD serving as the light source uses a normal tablet
terminal or a high brightness LCD for digital signage. The pinhole
arrays are placed in front of the LCD with appropriate clearance.
The basic display configuration is so simple that it is very simple.
By inputting the display pattern calculated by the computer on thisLCD, it becomes possible to display it when viewed through thepinhole. The display pattern is determined from three factors of thenumber of pinholes, the arrangement of pinholes, and the light field
to be displayed. An example of a display pattern to be created isshown in Figure 3 (c) . Depending on the LCD used for the lightsource, color display is possible.

4Application

We will show examples of application of the pinhole display as described above. The display we propose can be adapted to our lives
in a natural state blending into the surrounding environment unlike conventional displays. A display made with pinhole array ofwood grain material can be embedded in furniture such as bed andtable without damaging the texture of the material which it originally had. For example, you can display a watch or weather forecast blended into the bedside pillow of a tree without discomfort.
(Figure 4 ) In addition, if you use marble-like pinhole arrays, information can be displayed not only on furniture but also on the floorand walls. This makes it possible to present information such as
advertisements and directions, while leaving marble texture even inscenes where luxury like the hotel entrance is required.
Many of our daily lives have been made with importance on texture.
Interior of luxury car is composed of materials like wood grain andleather. It is also possible to blend the display on the dashboard ofa leather-covered luxury car if it is a display we propose. If youembed a conventional display in a leather-decorated interior, theluxurious feeling of the material will be partially impaired. If weembedded the display created by the method proposed by us insteadof the conventional display, we will be able to display directions andspeed display with natural appearance. In addition, it is possible tothink of interaction which had never existed due to the stereoscopic
view of the parallax barrier method making use of the property ofpinhole.
Even in the case of ordinary mirrors, it is possible to highlight theimage to be reflected on the mirror, but it is difficult to continue
displaying when the observer moves. The mirror image also moves
according to the movement of the observer. In the Infinite AR application we propose, we propose a system that can emphasize theimage reflected in the mirror for all viewers, assuming that multiple
viewers simultaneously see the same mirror. In the case of ordinary mirrors, the position of the mirror image reflected when one
observer A sees the mirror appears to be shifted from the positionof the mirror image when another observer B saw. In such a case,
it is impossible to highlight the mirror image by projection to themirror. In the display proposed by us, this problem can be avoided
since it is possible to separate rays according to the position of theobserver. This makes it possible to share emphasis display withmultiple observers.
As an example of using this function, I thought of an applicationthat assumed scenes like makeup while watching the mirror. Upto now, the function of presenting a guide by screen display to auser who is making makeup has been proposed. However, withthis function, guides are displayed shifted and displayed in addition
to the person who is making makeup. Therefore, if you use thedisplay made by the method proposed by us, it becomes easier toadvise, except for the user who is making makeup, it becomes easy
to advise.In addition, by tracking the face of the user, It is also
possible to display guides overlapping with each other.

5DISCUSSION

We have described the new pinhole display proposed so far. In thisdisplay, we were able to propose interactive applications using mirrors, as well as being able to embed them in personal belongings

Kazuki Takazawa:Leaked Light Field

(a)

4(b)

(c)

1/15s,f/5.6,ISO 3200

1/4s,f/4.5,ISO 3200

0.3s,f/4.0,ISO 3200

(d)

10s,f/4.0,ISO 100

21s,f/10,ISO 100

10s,f/4.0,ISO 100

21s,f/10,ISO 100

Figure 4: An example of creating a display using various everyday materials is shown. (a) It is possible to display a watch or a visualizer
without deteriorating the texture of the surface of the wood. (b) Information on logo, speed, etc. can be displayed on display on dashboard
using leather material. (c) The function whose display changes according to the viewpoint can also be added to displays other than mirrors.
(d) It also makes it easy to design displays that display time in multiple time zones.

without losing texture. However, this display has the problem ofbrightness as described in the experiment section. In addition, therelationship between the direct axis of the pinhole and the pixel
size of the liquid crystal display is also a problem.In the display wepropose, the brightness decreases because it works by observing thelight rays coming out through a small pinhole. According to our experiments, we found that the light intensity of the pinhole display
drops to one hundredth of the light intensity of the backlight. Therefore, the environment in which this display can be used is limited toenvironments where there is no intense light such as shadows inside
the room or outdoors. Since the LCD currently used is 450cd/m2 ,we believe that brightness can be improved by using brighter LCD
as the light source. There is also a problem of pinhole diameter andbacklight LCD pixel size. When the pixel size of the LCD is larger
than the diameter of the pinhole, the RGB of the pixel may be displayed separately. Therefore, it is necessary to adjust not only thepinholes of 100 µmbut also the arrangement of pinholes and pinholes of larger sizes. When pinhole processing is not applied withthe optimum setting, moir may appear on the display, or the viewpoint split display may not be accurately performed in some cases.

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6Conclusion and Future work

In this research, we have proposed a processing method fordisplaying non-transparent and non-smooth material such as woodgrain material, marble like material, leather material, mirror etc. asa display. It is difficult to observe a minute pinhole with the naked
eye, and when the switch of the display is off it can be blended into
the surrounding texture and the function to become a display only
when the switch is turned on can be added to the daily material .
By doing this, it was found that we can eliminate constraints on
display design, expand the range of display utilization, and apply
our application to further augment our lives. We believe that thisnew display will become indispensable for the future era to enablepresentation of information to our closer familiar places.

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