A RECEIVER UNIT OF PHOTODETECTORS FOR A LASER

POINTER AS A WIRELESS CONTROLLER

Jaemyoung Lee

Korea Polytechnic University, 2121, Jungwang, Shihung, Kyunggi, Republic of Korea

Keywords:

Wireless controller, Laser pointer, Receiver.

Abstract:

We propose a wireless receiver unit of photodetectors for a commercially available laser pointer. A controller

in the receiver unit drives a multimedia player in accordance with the scanning direction of the laser pointer

over photodetectors. A control algorithm is proposed for control of the multimedia player. We believe that the

proposed receiver unit and the control algorithm for a laser pointer can be applied to other systems.

1 INTRODUCTION

A laser pointer has mostly been used in presentations,

and has extended its application areas due to its porta-

bility, low cost, and visibility of the laser beam spot.

Lots of papers have used it as an input device (Kelvin

and Kelvin, 2003; Olsen and Nielsen, 2001; L. Zhang

and Chen, 2008; X. Bi and Chen, 2006), and some

papers have modiﬁed the laser pointer to afford other

functions as such the functions of a mouse (Oh and

Stuerzlinger, 2002; X. Bi and Chen, 2006).

In this paper, we use a commercially available

laser pointer as a wireless controller to activate and

control a multimedia player in a classroom. Multime-

dia players in classrooms are controlled by manual

buttons or RF remote controllers. In case of man-

ual operation, a lecturer should access to the con-

trol panel of a multimedia player each time he/she

wants some operation. For an RF controller, a lec-

turer should carry it and not misplace it to control the

player during his/her lecture. We propose a remote

control system for multimedia players in classrooms

using a laser pointer which most lecturers carry. To

use a laser pointer as a wireless controller, we build

a wireless receiver unit of photodetectors arranged in

a rectangular shape. A controller in the receiver unit

perceives the scanning direction of the laser pointer

and determines a control mode in accordance with the

proposed algorithm. The control algorithm and the

proposed system scheme take into account problems

due to hand jitter, and laser pointer’s misdirection.

2 LASER POINTER AS A

WIRELESS CONTROLLER

We propose a wireless receiver unit using a com-

mercially available laser pointer in a classroom with-

out any alteration to itself, which has only one on-

off switch. Figure 1 shows a multimedia player in

which the proposed receiver unit of photodetectors is

attached to the multimedia player in a classroom.

Figure 1: Multimedia player using the proposed receiver

unit of photodetectors for a commercially available laser

point.

Even though this paper takes an example of a multi-

media player to apply the proposed scheme using a

laser pointer, the proposed scheme can be applied to

other systems.

2.1 Receiver Unit of Photodetectors

In the proposed scheme, the receiver unit of the multi-

media player has a group of photodetectors which are

arranged in a rectangular shape. A controller in the

175

Lee J. (2009).

A RECEIVER UNIT OF PHOTODETECTORS FOR A LASER POINTER AS A WIRELESS CONTROLLER.

In Proceedings of the 11th International Conference on Enterprise Information Systems - Human-Computer Interaction, pages 175-177

DOI: 10.5220/0001989901750177

 SciTePress

receiver unit monitors the resistance of each photode-

tector to determine the laser pointer’s scanning direc-

tion over the photodetectors. The controller activates

an action on the multimedia player based on the scan-

ning direction of the laser pointer over the photode-

tectors, such as scanning to left, right, up, or down.

The proposed scheme could also activate certain ac-

tion by tying each photodetector for an action of the

multimedia player. However, the tying of each pho-

todetector for an action could cause unexpected ac-

tions due to laser pointer’s misdirecting. Since it is

hard to project a laser pointer’s beam on a speciﬁc

photodetector at a distance without any hand jitter, ty-

ing an action with a scanning direction on a group of

photodetectors is less vulnerable to misdirection and

to hand jitter, compared with tying an action with on-

or off- status of a photodetector.

Scanning to right and scanning down in oblique

directions are shown in Fig. 2 (a) and (b), respec-

tively.

Figure 2: Scanning (a) to right (b) down (c) in diagonal di-

rections in 3 × 3 photodetectors and (d) in a diagonal direc-

tion in 3 × 5 photodetectors (e) ID numbers of phtodetecors

in 3 × 3 photodetectors.

Even though the scanning directions are oblique in

Fig. 2(a) and (b), both cases are judged as scanning

to right and down by the controller. In case of Fig. 2

(a), photodetectors of 11, 12, and 23 can be regarded

as being scanned by a laser pointer (ID numbers of

photodetectors are listed in Fig. 2(e)). In Fig. 2(b),

the laser pointer projects a beam on the photodetec-

tors of 11, 21 and 22, 32. Since the spot size of the

laser point is comparable to the size of photodetector,

the spot of a laser pointer can spread over two pho-

todetecors along its scanning such as photodetectors

of 12 and 22, and photodetectors of 21 and 22 in Fig.

2 (a) and Fig. 2 (b), respectively. The problem of

laser pointer spot’s spreading over photodetectors can

be solved by the algorithm of controller’s.

The square shape of the group of photodetectors

may cause unexpected results, because the diagonal

scanning in Fig. 2 (c) can be perceived as scanning

to right , down. In the proposed scheme, we elimi-

nate this situation by arranging the photodetectors as

a rectangular shape. The scanning direction shown

in Fig. 2 (d) is rightward, because the laser pointer

beam scans photodetectors at both left and right sides.

The vertical length of the rectangular can also be ar-

ranged longer than the horizontal length in the pro-

posed scheme.

2.2 Control Algorithm for the Proposed

Scheme

To control a multimedia player using a laser pointer,

we propose a simple control algorithm, (Fig.3).

Figure 3: A proposed control algorithm to control a multi-

media player using a laser pointer.

Scanning of a laser pointer to either right or left

through a receiver unit in which a group of photode-

tectors are arranged in a rectangular shape activates

the multimedia player, leading to a ﬁle search mode.

Forward and backward ﬁle searches can be made by

laser pointer’sscanning the receiver unit up and down,

respectively. Another scanning to right changes the

mode into a volume control mode, in which scanning

up and down turn the volume up and down, respec-

tively. Scanning to right at the volume mode leads

to a channel search mode in which scanning up and

down tune to the next adjacent channel forward and

backward, respectively. Further scanning to right at

the channel search mode deactivates the player. Scan-

ning to left at any mode returns the mode back to the

previous mode in the proposed algorithm. Various al-

gorithms can be suggested and realized for control-

ICEIS 2009 - International Conference on Enterprise Information Systems

176

ling the multimedia player using a laser pointer as a

wireless controller.

3 EXPERIMENT

We investigated the feasibility of the proposed

scheme by measuring the resistances of photodetec-

tors being projected by a laser pointer, (Fig. 4). Mea-

sured resistances in Fig. 4 show a linear increase as

the laser pointer moves away from the photodetector.

Because of the laser pointer’s electrical jitter, we ob-

served variations in resistances, which are shown as

error bars in Fig. 4. However, we could drive the

multimedia player with a laser pointer at the distance

of more than 20 m away from the receiver unit.

Ω

Figure 4: Measurements of resistance for different dis-

tances.

4 CONCLUSIONS

In this paper, we propose a wireless receiver unit of

photodetectors using a commercially available laser

pointer. To use a laser pointer as a wireless con-

troller without any alteration to itself, we build a re-

ceiver unit of photodetectors. Experiment shows that

resistances of photodetectors linearly increase as the

laser pointer moves away, and that the laser pointer

can send enough power to activate the multimedia

player at the distance of more than 20 m from the laser

pointer. The controller in the receiver unit acts on the

scanning direction of a laser pointer in the proposed

scheme. We believe that the proposed control algo-

rithm can further afford other control modes and be

applied to other systems.

ACKNOWLEDGEMENTS

This work is ﬁnancially supported by the Min-

istry of Education and Human Resources Devel-

opment(MOE), the Ministry of Commerce, Indus-

try and Energy(MOCIE) and the Ministry of La-

bor(MOLAB) through the fostering project of the

Industrial-Academic Cooperation Centered Univer-

sity.

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L. Zhang, Y. S. and Chen, B. (2008). Nalp: Navi-

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Oh, J.-Y. and Stuerzlinger, W. (2002). Laser pointers as col-

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Olsen, D. and Nielsen, T. (2001). Laser pointer interaction.

In ACM CHI’2001 Conference Proceedings: Human

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X. Bi, Y. S. and Chen, X. (2006). Paper templates. In uPen:

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