Coating Thickness Monitoring by Optical Density Measurements

1
Coating Thickness Monitoring by Optical Density
Measurements

• Group Sean Broderick
• Jeremy Ingle
• Advisor Dr. Richard Gale

2
What is a Photomultiplier?
Jeremy
3
What are they used for?

• Scanning Electron Microscopes
• Telescopic Amplification
• Particle Counting in Dust-Free Environments
• Pollution Monitoring
• Radioactive Measurement
• And more

Jeremy
4
PMT Assembly Process

• Currently a technician monitors the brightness
  and color of an aluminum filament when current is
  applied.
• When the brightness diminishes sufficiently due
  to aluminum deposition a relay is switched
  cutting off current
• This is highly subjective and prone to
  inaccuracies

Jeremy
5
Objectives

• To determine the feasibility of and design a
  system to determine the thickness of metal plated
  onto a glass surface by examining changes in the
  intensity of light passing through the metal

Sean
6
Objectives - Translation

• Machine Vision system using a color camera,
  computer, IMAQ board, and LabVIEW to examine the
  light

Sean
7
System Intended

• Using an actual deposition system
• The computer would break the circuit with the
  filament.
• Our viewing window would be where the camera
  could view the filament through the slide.

Sean
8
Model System

• Low-cost experiment to determine the feasibility
  of a machine vision system for examining and
  controlling the deposition process of a PMT.

9
Model Design
Jeremy
10
Model Description

• Mounted on black painted 1x4
• ¼ wooden dowels for support
• Zip-ties to hold lenses and filter to dowel

Jeremy
11
Lens

• 2 glass plano-convex lenses
• Diameter 50 mm
• Focal length 205mm
• f/ 4

Jeremy
12
Variable neutral density filter
Increases optical density with the angle while
not affecting color
Jeremy
13
Transmittance vs. Angle
Jeremy
14
Optical Density vs. Angle
Jeremy
15
Other Aspects

• Polarizing lens was not used
• Even at full density the max value was 254
• Color Temperature not implemented
• Didnt suit immediate goals of optical grade
  evaluation
• Foundations in place for color temperature goals
  simple code to implement

Jeremy
16
IMAQ PCI-1411

• IMAQ Board
• Single channel, analog, color
• Capabilities is better than 1407
• All of the needed functions still present
• Should be a straight forward matter to implement
  with existing system and code.

Sean
17
IMAQ Board

• Need color IMAQ board for color temperature
  readings
• All boards are capable of allowing intensity
  (brightness) examination
• For time reasons, an NI-IMAQ board was chosen for
  its ease of use in the LabVIEW environment

Sean
18
LabVIEW Program - Overview

• Capture color image from camera
• Use thresholds to make a mask image
• Convert mask to a Region of Interest (ROI)
  automatically and manually
• Examine the grayscale value of the pixels in the
  ROI
• Determine optical grade for a given theta

Sean
19
LabVIEW GUI
Sean
20
Main Source
Sean
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Image Acquisition Block
Sean
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Auto ROI Block
Sean
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Snap Processing Block
Sean
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Grab Processing Block
Sean
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Results - Uninhibited
Jeremy
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0 degrees
Jeremy
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90 Degrees
Jeremy
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180 degrees
Jeremy
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225 degrees
Jeremy
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270 degrees
Jeremy
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300 degrees
Jeremy
32
Summary of Results

• 0 deg 11000 (frequency) 0 (OD)
• 90 deg 9500 0.06
• 180 deg 5000 0.34
• 225 deg 3000 0.56
• 270 deg 1700 0.81
• 300 deg 1100 1

Optical Density log(11000/value)
Jeremy
33
Graph of Filter Wheel
Jeremy
34
100 Angstroms
Jeremy
35
200 Angstroms
Jeremy
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300 Angstroms
Jeremy
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Results

• 100 A - 3300 (frequency) 0.52 (OD)
• 200 A - 520 1.32
• 300 A - 20 2.74
• 400 A - 0

Jeremy
38
Graph of Al Thickness
Jeremy
39
Conclusions

• Optical density graph seems linear
• Needed more samples, 50 and 150 angstroms

Jeremy
40
Budget
Lab Member Hours/Sem /hour Total Jeremy
Ingle 144 20 2880 Sean Broderick 144 20
2880 Equipment Computer with
LabView 1000 IMAQ board 895 Color CCD
Camera 800 ND Filter 600
Materials for model 10 Lenses
2 Glass Slide 5 _at_ 6.15 ea
31 Chamber Sub-Total 9098
75 Overhead 6824 Grand
Total 15922
Jeremy
41
Gantt Chart
Sean
42
References

• Interview with Dr. Gale 9/3/2004
• http//laxmi.nuc.ucla.edu8248/M248_99/autorad/Sci
  nt/pmt.html
• IMAQ Board image http//www.ni.com
• Kodak.com
• Torrscientific.co.uk

43
Questions