Optical System Design Optical system analysis on CCD

Optical System Design Optical system analysis on CCD imager Optical System Analysis on CCD Imager of the ISUAL Project Chern-Fang Ho and A- Chuan Hsu ISUAL project Lab. of RF-MW Photonics, Department of Physics, National Cheng-Kung University, Tainan, Taiwan NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU

Optical System Design Optical system analysis on CCD imager NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 2

Optical System Design Optical system analysis on CCD imager Outline • Review on Instrument Requirements – CCD imager – Spectral filter – Mechanical layout • Optical System analysis – Performance of CCD imager – Tolerance analysis • Stray Light Analysis – performance of CCD imager • Conclusions NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 3

Optical System Design Optical system analysis on CCD imager Review on requirement of CCD imager NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 4

Optical System Design Optical system analysis on CCD imager Review on spectral band of filters NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation • 1. 660 -900 nm – Noth @756 -790 nm • 2. 762 nm • 3. 427. 8 nm • 4. 630 nm • 5. 557. 7 nm • 6. 400 -900 nm – IR/thermal block RF-MW Photonics Laboratory, NCKU 5

Optical System Design Optical system analysis on CCD imager Mechanical layout NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 6

Optical system analysis on CCD imager Optical System Design Optical analysis results- Verification of Basic Requirements • Encircled energy of spot – 80% encircled energy in 40 m diameter (Pixel Size) – See Spot diagram • Spatial Resolution – Nyquist Frequency(12. 5 cysles/mm) the max. spatial frequency of imager can be resolved by pixilated sensor NCKU – See MTF output Optical Simulation Tohoku CDR 9 July, 2001 UCB RF-MW Photonics Laboratory, NCKU 7

Optical System Design Optical system analysis on CCD imager Spot Diagram ON AXIAL 0. 7 field angle Geometrical Spot size 0. 007562 mm Geometrical Spot size 0. 009436 mm Full field angle Geometrical Spot size 0. 01353 mm • Smaller than Specification limitation 0. 02 mm(rad) Scalar equal to Pixel Size(40*40 m 2) NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 8

Optical System Design Optical system analysis on CCD imager Encircled Energy Encircled energy must be 80% in 40 m diameter (Pixel ON AXIALSize) 0. 7 field angle Full field angle • 80% encircled energy : 0. 009149 mm(rad) 0. 011016 mm(rad) 0. 013974 mm(rad) • Smaller than Specification limitation 0. 02 mm(rad) NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 9

Optical System Design Optical system analysis on CCD imager MTF output ON AXIAL 0. 7 field angle Full field angle Geometric MTF at Nyquist Frequency Tan: 93. 5% Tan: 90. 09% Tan: 86. 8% Sag: 93. 5% Sag: 90. 01% Sag: 79. 6% Good output NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 10

Optical System Design Optical system analysis on CCD imager Optical analysis results. Verification of Paraxial parameters Verification of the Basic Requirement NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 11

Optical System Design Optical system analysis on CCD imager Real Condition Simulation • The imager will be working with different Spectral Filters – The Chromatic Focal shift will cause performance variation. • Defcous / Bluer in imager plane – We simulate the real condition and check the performance variation. NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 12

Optical System Design Optical system analysis on CCD imager Chromatic Focal shift of Imager Lens System #2 defocus 0. 03 mm #3 defocus 0. 01 mm #4 defocus -0. 07 mm #5 defocus -0. 1 mm NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 13

Optical System Design Optical system analysis on CCD imager Defocus and Bluer on Image Plane NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 14

Optical System Design Optical system analysis on CCD imager Performance Variation in Different Spectral filter • Specification limitation of spots 20 um(rad) NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 15

Optical System Design Optical system analysis on CCD imager Image Diagram at Nyquist Frequency #2 Spectral filter NCKU UCB Tohoku #5 Spectral filter CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 16

Optical System Design Optical system analysis on CCD imager Optical analysis results- Tolerance Analysis Tolerance – Fabrication • Surface / Thickness / Index / Vnumber… – Component assembly error • Decenteration / Title / Air space… – Tolerance V. S. performance • Suitable tolerance • Performance variation NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 17

Optical System Design Optical system analysis on CCD imager Optical analysis results- Component Tolerances of CCD imager • Imager lens system • 4 configuations for 4 different spectral filters • Consider component error – – – Air-space Component decentation Component center of curvature • Sensitivity analysis – Spot diagram / MTF tolerancing UCB Tohokusensitivity CDR 9 July, 2001 • Inverse NCKU Optical Simulation RF-MW Photonics Laboratory, NCKU 18

Optical System Design Optical system analysis on CCD imager Tolerance Guide of Imager lens system • High level precision in need NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 19

Optical System Design Optical system analysis on CCD imager Stray light analysis Reflective rays of barrel Splits & Total internal reflections Ray Optical System NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation Defocused GHOST IMAGES on image plane RF-MW Photonics Laboratory, NCKU 20

Optical System Design Optical system analysis on CCD imager CCD Imager Lens System Layout in ASAP Lens without barrel NCKU UCB Tohoku CDR 9 July, 2001 Lens with barrel Optical Simulation RF-MW Photonics Laboratory, NCKU 21

Optical System Design Optical system analysis on CCD imager Investigation of Ghost Images • Raytracing - consider all split 2 rays • Most significant ghost paths For suitable simulation: • The ray split 2 times ( This is custom of ghost image analysis) • Consider the most significant ghost paths: depending on the energy or flux contributions on the image plane NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 22

Optical System Design Optical system analysis on CCD imager Stray light tracing Ghost image spots Ghost image energy distribution On -axis 0. 7 field angle Full field angle NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 23

Optical System Design Optical system analysis on CCD imager MTF output • The ghost image will degenerate the MTF output is selected at Nyquest frequency 12. 5 cycles/ mm • The MTF still can keep a good output n(n-1)/2 ghosts for glass-air surface R is the loss for surfaces NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 24

Optical system analysis on CCD imager Optical System Design Conclusion 1 - Optical System Analysis of CCD imager • We follow the setup of the “COATSAL OPTICAL SYSTEM, INC. ” and simulate the imager lens system. We find: – The paraxial parameters are fit in with the specification of imager. – Good output performance (spot, encircled energy, MTF ) for postposition system. • But, if in real condition, the simulation shows that the performance of imager lens system will be degraded due to the Chromatic focal shift. NCKU – The imager works well for the #2 and #3 spectral filter. – But for the #4 and #5 spectral filer, the performance is UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU poor, especially for the #5 filter, the imager only indicate 25

Optical System Design Optical system analysis on CCD imager Conclusion 2 - Tolerance of Imager Lens System – Assembly Error • Based on the ISO 10110 standard of tolerance and the Inverse sensitivity analysis we find: – the Imager needs high level precision in assembly. – if the assembly error occurs, the imager still work in #2 and #3 spectral filter, but the performance will degraded. For the cases of #4 and #5, the results becomes worse. – The imager need strong constructions (holder / spacer) to keep the lens system stable away from environmental variation. NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 26

Optical System Design Optical system analysis on CCD imager Conclusion 3 - Stray light & Ghost image analysis • In current design, the signification ghost image should come from the split rays, i. e. , from total internal reflection of lens media. • Contribution of the Ghost image are very small on image plane – about 0. 1%~0. 3% – the original MTF output performance remains NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 27

Optical System Design Optical system analysis on CCD imager THE END NCKU UCB Tohoku CDR 9 July, 2001 Optical Simulation RF-MW Photonics Laboratory, NCKU 28