Automatic Display Zoom for People Suffering from Presbyopia
Fang Huiyi
Nagoya Institute of Technology, Japan30414108@stn.nitech.ac.jp

Kenji Funahashi
Nagoya Institute of Technology, Japankenji@nitech.ac.jp

Figure 1: Explanation of automatic zoom and its example: (1) Material is displayed as original size when startup,(2) It is zoomed in when moving tablet close to face, (3) It is zoomed out when moving tablet away from face.

CCS CONCEPTS• Human-centerd computing →Human computer interaction(HCI)

KEYWORDS
Display zoom, Presbyopia
ACM Reference format:
Huiyi Fang and Kenji Funahashi. 2018. Automatic Display Zoom for People
Suffering from Presbyopia. In Proceedings of SIGGRAPH '18 Posters. August 12-16,
2018, Vancouver, BC, Canada, 2 pages.
https://doi.org/10.1145/3230744.3230754

1 INTRODUCTION1
Human eyes have an adjustment function to adjust for different
distances of seeing. However, it becomes weaker as you get older.
When you move paper closer to read small letters, it is not infocus. When you move it away to bring it into focus, it is toosmall to read. This condition is called Presbyopia. People
suffering from presbyopia also suffer from this condition when
they use a smartphone or tablet. Although they can magnify thedisplay using the pinch operation, it is a bother. A method forautomatic display zoom, to see detail and an overview, wasproposed in [Satake et al. 2016]. This method measures thedistance between a face and a screen to judge whether you want
to see detail or an overview. When you move it close to yourPermission to make digital or hard copies of part or all of this work for personal orclassroom use is granted without fee provided that copies are not made or
distributed for profit or commercial advantage and that copies bear this notice andthe full citation on the first page. Copyrights for third-party components of thiswork must be honored. For all other uses, contact the Owner/Author.
SIGGRAPH '18 Posters, August 12-16, 2018, Vancouver, BC, Canada© 2018 Copyright is held by the owner/author(s).
ACM ISBN 978-1-4503-5817-0/18/08.
https://doi.org/10.1145/3230744.3230754

face, it judges you want to see detail and zooms in. When you
move it away from your face, it judges that you want to see
overview and zooms out. In this paper, we improve and apply
this method for presbyopia. First we observe and analyze thebehavior of presbyopic people when trying to read small letters.
Then we propose a suitable zooming function, for example, ascreen is zoomed in also when it is moved away if the person
suffers from presbyopia.

2 CONVENTIONAL AUTOMATIC DISPLAYZOOM BASED ON DISTANCE
We have used the front camera of a tablet to measure thedistance between a face and a display in our conventional
experimental system, instead of a depth sensor. We paid
attention to the relation that binocular distance on a screen
image captured by a camera (onscreen binocular distance, 𝑑(𝑡)at time 𝑡) is inversely proportional to the distance between acamera and a face. When onscreen binocular distance increases,
it is judged that the screen is moving closer to a face. When it
decreases, the screen is moving away. In addition, the change
rate of onscreen binocular distance is related to the moving
speed of the screen. It is calculated as 𝑣𝑇 (𝑡) = 𝑑(𝑡) / 𝑑(𝑡 − 𝑇)at time 𝑡 with interval time 𝑇. When a user moves a tablet
slowly, 𝑣𝑇 (𝑡) become close to 1. The scale ratio to zoom in/out is
proportional to this change rate 𝑣𝑇 (𝑡). When you move it close
to your face to see detail, it is zoomed in. When you move itaway from your face to see an overview, it is zoomed out (Fig. 1).

3 OBSERVATION EXPERIMENT
We investigated how people move a tablet when they read small
letters. Participants read small letters and also several other sizesof letters. Then we analyzed how presbyopic participants andother people move the tablet. As a result, presbyopic participants

SIGGRAPH’18 Posters, August 12 - 16, 2018, Vancouver, BC, CanadaH. Fang et al.

Figure 2: Explanation of presbyopia zoom and its example: (1) Material is displayed as original size when startup,(2) It is zoomed in when moving tablet close to face, (3) It is also zoomed in when moving tablet away from face.
moved the tablet and changed the distance between their face
and the screen frequently when it is difficult to see because ofpresbyopia. In addition, they moved it slowly compared to others.
On the other hand, presbyopic participants rarely moved it when
there is no presbyopia problem for reading large size letters, andthe moving speed is not always the same. We thought that
others can focus on it even if they move it quickly.

4 AUTOMATIC DISPLAY ZOOMCORRESPOND TO PRESBYOPIC PEOPLE
We propose an improved automatic display zoom method basedon the experimental results. Here, we call the zoom mentioned
above as normal zoom, and an additional function of an
improved method as presbyopia zoom. This presbyopia zoom
works only when you hardly see due to presbyopia. A point
system is introduced to judge which type zoom should work, inother words, whether there is a presbyopia symptom, according
to a tablet motion. Added and subtracted points are defined as
Fig. 3 for each tablet moving speed (not absolute speed),according to the experimental results. Presbyopic people usually
moved a tablet at the speed range where a point is added. A total
point is added and subtracted at every interval time, thenpresbyopia zoom works when the point is greater than thepredefined threshold. It is subtracted, for example, when a tablet
is moved closer and away faster than the presbyopia speed range,
and when a tablet has not moved for a while. Fig. 4 shows theFigure 3: Point addition and subtraction condition for 𝑣1.0 (𝑡)zoom mode (in/out) related to zoom type (normal/presbyopia)
and tablet moving speed. The scale ratio to zoom in/out is
proportional to this point only for presbyopia zoom. We applied
this idea to develop an experimental system, and a presbyopic
people and an emmetropia people tried to use it to check how itworks (Fig. 5). First, the emmetropia people moved the tablet
without presbyopia symptom (Fig. 1), zoom type was notchanged from normal zoom to presbyopia one. It was zoomed inwhen a tablet was moved close to a face (Fig. 1(2)). After that, it
was zoomed out when it was moved away (Fig. 1(3)). Next, thepresbyopic people moved the tablet with presbyopia symptoms(Fig. 2), and zoom type was changed to presbyopia zoom. It waszoomed in with the scale ratio for presbyopia when it wasmoved closer (Fig. 2(2)). After that, it was zoomed in again evenwhen it was moved away (Fig. 2(3)).

Figure 5: Trial scene

5 CONCLUSION
In this paper, we proposed automatic display zoom
corresponding to presbyopic people. It recognizes a user'ssituation and provides a suitable zoom function. Although anexperimental system worked as we expected, it did not work
well when a user did not move the tablet at a supposed speed. In
the future, we would like to conduct further experiments to findadditional differences between presbyopic people and others. We
should develop practical and useful automatic zoom forpresbyopic people.

REFERENCES
Figure 4: Zoom mode, type, and moving speed 𝑣1.0 (𝑡)Satake, Y., Funahashi, K., 2016, Automatic Display Zoom Using Face Size Of
Camera Image, Proc. ICAT-EGVE 2016 (poster & demo), pp.1-2