光學元件精密製造與檢測 Precision Manufacturing & Inspection of Optical Components --- Ch.12 組件品質檢測 Speaker: Bo-Wen Xiao (蕭博文) Advisor: Prof. Yi-Pai Huang (黃乙白教授) Prof. Chung-Hao Tien(田仲豪教授) Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan Apr. 17 2008

Outline Effective focal length (EFL) Diffusion characteristics - Direct measurement method - Magnification method Diffusion characteristics - Bidirectional scattering distribution function (BSDF) - Scatterometer Polarization - Polarization & Polarizer - Birefringence crystal & Phase retarder - Inspection of polarizer Conclusions

If n=n'', N and N' coincide with P,P' Cardinal point n n' n'' F, F' : front and rear focal points P, P' : front and rear principal points V, V' : front and rear surface vertices N, N' : front and rear nodal points If n=n'', N and N' coincide with P,P'

Direct Measurement Method nodal slide (光具座) ： measuring the distance between N’ and F’ directly EFL

Magnification Method More easy and convenient to measure. focimeter (焦距儀) ： measuring the EFL by calculating magnification EFL More easy and convenient to measure. Suitable to utilize in production line. 

Outline Effective focal length (EFL) Diffusion characteristics - Direct measurement method - Magnification method Diffusion characteristics - Bidirectional scattering distribution function (BSDF) - Scatterometer Polarization - Polarization & Polarizer - Birefringence crystal & Phase retarder - Inspection of polarizer Conclusions

Diffusion Characteristics Refraction Reflection Absorption Diffuse/Scattering Volume scattering Material Surface Different !! Different !! Diffusion characteristic of diffuser : Diffuser - refractive index of material - dimension and geometry of particle

Description of Diffusion Characteristic Bidirectional scattering distribution function (BSDF) - Bidirectional transmission scattering distribution function (BTDF) - Bidirectional reflection scattering distribution function (BRDF) - Bidirectional volume scattering distribution function (BVDF)

Reflection-type could be a good choice. Scatterometer Degrees of mechanical freedom : - 3 translational degrees of freedom  adjust position - 3 rotational degrees of freedom adjust azimuth angle θ 　 zenith angle Φ Dynamic range : >60dB Design of self-component : - Transmission-type  eliminate off-axis aberration (number of lens ↑) cause noise & ghost path (scattering and volume scattering) Reflection-type could be a good choice. - Reflection-type no volume scattering no chromatic aberration (number of lens ↓)

Outline Effective focal length (EFL) Diffusion characteristics - Direct measurement method - Magnification method Diffusion characteristics - Bidirectional scattering distribution function (BSDF) - Scatterometer Polarization - Polarization & Polarizer - Birefringence crystal & Phase retarder - Inspection of polarizer Conclusions

Circular polarization Elliptical polarization Linear polarization Circular polarization Elliptical polarization Linear polarization Circular polarization Elliptical polarization

Polarizer Absorptive polarizer (Dichroic polarizer) - Wire-grid (金屬網狀) Larger volume , higher cost - Sheet (片狀) J-sheet polarizer (by Edwin H. Land ,1928) nitrocellulose(硝棉) polymer + iodoquinine sulfate (硫酸鹽碘化物) EM field H-sheet polarizer (by Edwin H. Land ,1938) Easier to fabricate polyvinvl alcohol (PVA, 聚乙烯醇) + iodine (碘) Influence by humidity and heat (high vapor pressure of iodone) external force K-sheet polarizer Higher stability and polarization efficiency heat & catalyst  evaporate water

Polarizer (ii) Reflective polarizer s+p - Brewster plate Brewster angle s - Polarization beam splitter (PBS) MacNeille polarizing prism p MacNeille 麥尼利 s

Birefringence Crystal & Phase Retarder Phase difference Polarization conversion system (PCS) Phase retarder - Half-wave plate X-LP  Y- LP - Quarter-wave plate LP  Circular Polarization

Inspection of Polarizer Direction of polarization find out θ Extinction ratio (消除比) ∞ (ideal) > 10000 (real) Polarization efficiency (偏極效率) 1 (ideal) > 99%(real)

Outline Effective focal length (EFL) Diffusion characteristics - Direct measurement method - Magnification method Diffusion characteristics - Bidirectional scattering distribution function (BSDF) - Scatterometer Polarization - Polarization & Polarizer - Birefringence crystal & Phase retarder - Inspection of polarizer Conclusions

Conclusions Effective focal length Diffusion characteristics - EFL can be measured by two methods. (Direct measurement method & Magnification method) Diffusion characteristics - Diffusion characteristics can be described by BSDF. (BTDF, BRDF, BVDF) - BSDF can be measured by scatterometer. Polarization - Polarizer & phase retarder can be utilized in LCD system.

Thank you for your kind attention !!

Reticle

PBS Wollaston prism Commercial prisms are available with divergence angles from 15° to about 45°