“Stopping Down” Annular Apertures UCSD Photonics
Refractive lens 70% obscured 90% obscured (35mm, F/1.4) (D = 60mm, F = 35 mm) (D = 60mm, F = 35 mm)
Arc-section angle
Off-axis aperture mask On-axisUnobscured aperture mask (same diffraction results) “Arc-section” aperture mask MTF MTF MTF
Full-aperture Full-aperture Full-aperture (F/1.4) (F/1.3) (F/.8) 0.63*D ()(F/2.2) 50° arc-section (F/2.2) 0.39*D (F/3.6) 50° arc-section (F/3.6)
Arc-Sectioning: increased depth of field, reduced volume - 1D loss of resolution w/ very large obscuration 1 Arc-Sectioned Eight-Reflection Lens UCSD Photonics
Geometrical Depth of Field Modeled performance: - 38 mm focal length, F/#eff = 3.76 40 mm, F/1.9 lens Blur at - asymmetrical PSF and MTF due to diffraction (for reference) Spot at 4% defocus - Trade light collection and 1D resolution Best focus @ 2.5 m for depth of field and compactness
PSF NA=0.26 5μm
RRMS 1.5 μm RRMS 7.5 μm
3 μm Phase 1 8-Reflection Lens
NA=0.7
R 0.5 μm RRMS 20.7 μm RMS (unacceptable) MTF
Arc-Section 8-Reflection Lens Horizontal Vertical
RRMS 0.5 μm RRMS 5.2 μm
2 Prototype Arc-Sectioned Camera UCSD Photonics
Fabrication: - Diamond section 50° from round diamond-machined lens Aperture is 7.2x smaller than full ring -Replace metal mirrors w/ dielectric stacks Transmission increases from 12% to ~50% (4.2x)
Angular sensitivity to light Forza ~85% Image sensor: - Forza/Sunplus 2.1Mpix sensor with 3 μm pixels OV3610 - IBM Copper-CMOS process: Thinner ~50% interconnects & larger sensor area → 70% greater energy collection at edge
Illuminated bands (8-fold imager)
Optomechanics & package: - USB interface on sensor PCB - On-board focus adjustments
3 Camera Performance Comparison UCSD Photonics
Conventional Lens Conventional Mini-Cam 8-Refl. Camera Arc-Sectioned 8-Refl. F43F = 43 mm, F/1 F/1950d.9: >50mm deep 1. 3 Mpix, f=3 . 9mm lens: ~ 5mm deep F=38mmF = 38 mm, 5mm deep F = 38 mm , 5mm deep
Full 1024x1024fieldElectronic zoom (~80x80 pixels) Full 1024x1024 field Full 1024x1024 field
8% Defocus @ 2.5 m
Best Focus
4 Resolution Over a 30% deep field: Images UCSD Photonics
Conventional Lens Tokina F/1.9 f = 40 mm
In focus (2.6 m) -15% +15%
Full Aperture 8-Reflection Lens
-3.8% In focus (2.72 m) +5.5% -15% +15%
Arc-Sectioned 8-Reflection Lens
In focus (2.6 m) -15% +15%
5 Resolution over a 30% deep field UCSD Photonics
USAF reso lu tion targe t: Measure object space resolution (lp/mm) Resolved Measured both horizontal and vertical resolution Not resolved Imagers: - Tokina F/1.9, f = 40 mm - Full 8-Refl. Al-CMOS sensor - Arc-sectioned 8-Refl. Cu-CMOS sensor
Horizontal Resolution Vertical Resolution tion on uu
Tokina Tokina m) tical Resoluti zontal Resol mm) mm m r r (LP/ (LP/
Arc-Sec. Arc-Sec. Full 8-Refl. Full 8-Refl. ect Space Ve ct Space Hori jj ee Camera Camera Ob Obj
6 Comparison: Canon SD-30 to the Arc-Sectioned Prototype UCSD Photonics
Canon SD-30 (jpeg!) Arc-Sectioned Camera (raw)
1
0.9 Canon SD30 Arc-Sectioned Montage Eight-Reflection camera 0.8
Optical track ~30mm 5mm 0.7 Light 0.6 < 20mm2 80mm2 Canon SD30 Compact Camera collection 0.5 Montage Nano Phase 1 Montage 8-Fold Resolution ~30 lp/mm 100 lp/mm 0.4 (2.2m range) Horizontal MTF 0.3 Canon SD30 Focal length 636.3 – 14.9mm 38mm 0.2 Multi-element Single element 0.1 Lens design refractor folded reflector 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Spatial Frequency in object space (cycles/mm) 7