Development of Experimental SetUp for CDROM Drive Demonstration

1
Development of Experimental Set-Up for CD-ROM
Drive Demonstration

• by
• Yonas Tegegn
• (03310201)
• Guide
• Prof. P. S. Gandhi

August 2004
2
Content

• Problems,objective and importance of the project
• Fundamentals of optics
• CD-ROM fundamentals
• Signal processing
• OSLO software
• Conclusions and future work

3
Crux of the problem of CD-ROM drive demonstration

• Small beam size
• Invisible light detection

Objective of the project

• To develop an experimental set up of CD-ROM drive
  with big size components and red laser light

Importance of the project

• Assist engineering teaching
• Gives pragmatic test of Mechatronic system
• Motivate research activities
• large data storage device

4
Fundamentals of optics

• Electromagnetic nature of light
• EyEysin(kx-wt) and BxBxsin (kx-wt)
• Abberation

Electromagnetic wave 1
Astigmatism2
5
...

• Diffraction
• Characteristics of laser Light

Diffraction in a single slit 14
Focusing a Gaussian beam Laser beam2
6
CD-ROM Drive Fundamentals

• Operation and system description

9
7
Three beam pick-up

• Optical system
• Mechanical
• electrical

Two axis pick-up 3
Hinged arm pick-up 3
8
Reading a disc

• Pits and lands
• Reflection and scattering

Cross section of CD 5
Beam reading a disc 5
9
Detail of each components

• Disc
• Laser source
• Diffraction grating
• Beam splitter and quarter plate
• Objective lens
• Photodiodes
• Tracking and focusing actuators

10
Tracking system

• Error signal (E-F)
• Photodiode
• Voice coil

On Track 1
Off track 1
11
Focusing system

• Astigmatic property
• Closeness or farness of disc
• Error signal (AC)-(BD)
• Photodiode array
• Voice coil

Focusing system 16
12
Previous attempt

• MEOS company
• Based on Displaying signal
• Open mounted CD drive , controller(MEOS01),
  Oscilloscope.

5
Controller
5
CD drive
13
Signal processing

• Noise in the photodiode
• Johnson and shot
• Filters
• Low and High pass
• ADC and DAC
• For interfacing

14
Optical System layout design software (OSLO)

• Why OSLO?
• Construction of optical system
• OSLO analysis
• Optimization
• Cylindrical Lens in OSLO

15
Graphic window (OSLO)
16
Summary and Conclusions

• Interference polarization and diffraction
  understanding
• Characteristics of CD-ROM components
• Infrared and 1.7micron diameter laser detection
• Use of OSLO in CD-ROM for the setup
• Need of Experimental set up for Mechatronic
  education

17
Future works

• 1.Several experiments with each component with
  red laser light.
• 2.Real system delineation on optical table
• 3.OSLO software
• 4.Experiment on the actual CD-ROM head
• 5.Interfacing signals from photodiode to PC

18
THANK YOU

• For attention

19
(No Transcript)