Degree project
The design of the optical touch
pointer system for brain tumor
resections
The electrical system design
Author: Zhiyuan Xie
Supervisor: Stefan Andersson Engels, Johan Axelsson
Examiner: Sven-Erik Sandström Date: HT13
Course Code: 5ED05E
Subject: Electrical Engineering Level: Secondary
635nm
i
V (0,0) i-V charactor of p-n junction
⁄
⁄
V
i-V charactor of p-n junction photodiode
F1-f5:narrow band filters S2 S3 S4 f1 f2 f3 f4 f5 l1 l2 l3 l4 S1 f0 L1-l5:focus lens l5
Long pass filter S1-S4:beam spillter
Ray tracing sketch of the optical system
DAQ 405nm diode laser Clock output 0-5V
Cd RL Id Id iNs iNth RL Cd Vo Vo
Front end: a resistor
Protel real circular design Protel PCB design
0 10 20 30 40 50 60 0 1 2 3 4 time(ms) v o l t a g e ( V ) input signal ambient light raw signal 22.8 23 23.2 23.4 23.6 23.8 24 24.2 24.4 2.5 3 3.5 time(ms) v o l t a g e ( V ) input signal ambient light raw signal 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 1.5 2 2.5 time(ms) v o l t a g e ( V ) output signal
Averaged dark signal Averaged light signal Difference between light
and dark signal
0 10 20 30 40 50 60 1 2 3 time(ms) v o l t a g e ( V )
ambient light signal+
Fast modulation and signal processing
1.Average over every half cycle
2.Calculate the different in
between averged light and dark signal in each cycle
Real time signal graph: all channels plotting and individule channel plotting
Intergrated average singal strength results for each channel
Data can be saved when signal get stable
Modulation frequency can be tuned here
Faculty of Technology
SE-391 82 Kalmar | SE-351 95 Växjö Phone +46 (0)772-28 80 00
teknik@lnu.se
