1. Plastic Optical Materials
Sheng-Huei Derek Lu
College of Optical Sciences
University of Arizona

2. Apple iPhone 4 Camera Lens
Apple iPhone 4 Camera Specs:
5.0 Mpixels (2592 x 1936)
3.85 mm lens focal length
f/2.8 lens aperture
Equivalent 35mm film camera
30 mm f/22
Sample image is 2592x1936 pixels
(5.0 MP, 4.02:3)
Don't throw away your FourThird, APS-C or full frame SLR 
Cost is Everything!!

3. iPhone 4 Camera Module
Glass cell phone lenses cost $20-$40 in the market.
Plastic cost: $3.55 only
Manufacturer: Largan Precision Co., LTD, Taiwan
Product#: 9457F
Composition：4 Plastic Elements
Very high production volumes
Injection Molding: 8-Holes Method
8 cavities at the same time
Monthly volume = 207,306 parts

4. Outlines Plastic optical material application Advantages Disadvantages
Issues:
Structural Stability
Thermal Stability
Moisture Absorption
Injection Molding
Wavefont error budget
Reference

5. What are optical elements made of plastic?
Cellphone/ NB/ Car/ Camera Lens
Bar code scanners in CD players
Prisms
LED collimator
Diffractive Optical Elements

6. Main Advantages Cost Production volume Weight reduction
Aspheric and diffractive surfaces
Integral features – can have mounting features or multifunction parts

7. Disadvantages Lower service temperature than glass
- max service ºC
Low structural stability
- soft, larger deflection while applying force, lower resonant frequency than glass
Poor thermal properties
– high dn/dT, high CTE
Moisture Absorption
Limited material selection

8. Material Properties of Plastic Optical Element

9. Plastic Element Structural Stability
ρ = 1 g/cm3, E = 3 Gpa (glass: ρ=2.5 g/cm3, E=80 Gpa)
Resonant frequency
Plastic with 1/3 resonant frequency than glass
Deflection per thickness
Plastic with 10 times deflection than glass

10. Plastic Element Thermal Stability
dn/dT = -8.5 ppm/ºC, CTE = 72 ppm/ºC, λ = 0.21 W/mK
(glass: dn/dT = 1.86 ppm/ºC, CTE = 7 ppm/ºC, λ = 1 W/mK)
Defocus due to one degree change
β = 89 ppm/ºC for plastic, β = 3.28 ppm/ºC for glass
Linear thermal distortion of a constant heat flux Φ
Plastic with 50 times thermal deflection than glass

11. Moisture Absorption
Water absorption: change of volume, change of refractive index
The coefficient of moisture expansion (CME) for PMMA is about 0.5%
The change of refractive index for PMMA is about 900 ppm
Cycloolefin Polymer (COP) and Cycloolefin Copolymer (COC) are known as low moisture absorption.

12. Injection Molding Surface Imperfections Shrinkage
- Melt temperature is too high to cause gas evolution: bubbles
- Pressure is too low to cause incomplete filling of mold.
Shrinkage
- If the part thickness is too thin, part will
shrink while cooling.
- Applying holding pressure is maintained
to compensate for material shrinkage

13. Tolerance Analysis: wavefont error budget for the plastic optical component
1 mold costs $200,000!

14. Reference
Selected plastic optical material characteristics are listed in my tutorial: “Tutorial for Plastic Optical Materials”
Great reference book: Stefan Bȁumer etc. “Hand Book of Plastic Optics”, 2005 WILEY
Formulas: Prof. Burge, Opti 521/421 class note