The Michelson interferometer Best known and historically most important Best known and historically most important Utilizes arrangement of mirrors (M) and beam splitters (O) Utilizes arrangement of mirrors (M) and beam splitters (O) Compensator plate (C): each beam passes through equal thicknesses of glass  actual path difference Compensator plate (C): each beam passes through equal thicknesses of glass  actual path difference M2M2 O C M1M1 Source Detector

Conceptual rearrangement S 1 and S 2 = images of source S 1 and S 2 = images of source s o = s i, s o ’ = s i ’, s o ’ = s o + d s o = s i, s o ’ = s i ’, s o ’ = s o + d M2M2 M1’M1’S2S2 S1S1 Source so’so’ si’si’ soso sisi d 2d   Path difference

Optical path difference If beamsplitter is uncoated glass plate, phase shift from two reflections =  radians. If beamsplitter is uncoated glass plate, phase shift from two reflections =  radians. Destructive interference when 2dcos  = m Destructive interference when 2dcos  = m Extremely accurate length measurements:  d = N( /2) Extremely accurate length measurements:  d = N( /2) N = number of fringes that have moved past a reference point N = number of fringes that have moved past a reference point

Cameras Pinhole camera Pinhole camera Well-defined, practically undistorted image Well-defined, practically undistorted image Wide angular field, great depth of field Wide angular field, great depth of field No image results if entrance pupil is very large No image results if entrance pupil is very large Image forms and grows sharper with decrease in diameter 0.5 mm diameter hole at 0.25 m from film is convenient 0.5 mm diameter hole at 0.25 m from film is convenient Slow speed (f/500) Slow speed (f/500) skullsinthestars.com

Field of view To focus the camera, the entire lens is moved toward or away from the film plane. To focus the camera, the entire lens is moved toward or away from the film plane. Angular field of view  = angle subtended at lens by a circle encompassing the sensor area Angular field of view  = angle subtended at lens by a circle encompassing the sensor area Fraction of scene included in photograph Fraction of scene included in photograph blenderartists.org

Viewing area Standard SLR lens has focal length f in the range 50 to 58 mm, field of view = 40 o to 50 o Standard SLR lens has focal length f in the range 50 to 58 mm, field of view = 40 o to 50 o Wide-angle SLR lenses f = 40 to 6 mm,  = 50 o to 220 o Wide-angle SLR lenses f = 40 to 6 mm,  = 50 o to 220 o ezwatch-security-cameras.com

Depth of field Standard photographic objective must have a large relative aperture 1/(f/#) to keep exposure times short. Standard photographic objective must have a large relative aperture 1/(f/#) to keep exposure times short. Lens should have a wide angular field of view. Lens should have a wide angular field of view. abc.net.au

Apertures enchantingkerala.org photography-tips-guide.com

Single Lens Reflex cameras When shutter release is pressed, diaphragm closes down to a preset value. When shutter release is pressed, diaphragm closes down to a preset value. Built-in light-meter arrangement coupled to the diaphragm and shutter Built-in light-meter arrangement coupled to the diaphragm and shutter conversationswithfriends.com

Focal lengths 50mm is the "normal" focal length, neither wide angle nor telephoto. 50mm is the "normal" focal length, neither wide angle nor telephoto. Any focal length shorter than 50mm is wide angle Any focal length shorter than 50mm is wide angle Any focal length shorter than about 25mm is ultra wide angle; Any focal length shorter than about 25mm is ultra wide angle; Any focal length longer than 50mm is technically telephoto; Any focal length longer than 50mm is technically telephoto; 85mm to 135mm is considered a portrait lens; 85mm to 135mm is considered a portrait lens;(daystarvisions.com) Compact digitals have a "normal" focal length about 1/5th or 1/6th that of 35mm. Compact digitals have a "normal" focal length about 1/5th or 1/6th that of 35mm. Lens barrel of a Canon A720 says Lens barrel of a Canon A720 says mm x 6 = 35mm and 34.8 x 6 = 210mm. 5.8mm x 6 = 35mm and 34.8 x 6 = 210mm. 1derful.info

Camera sensor blog.megapixel.net dummies.com

Charge-coupled device (CCD) arrays Most common sensor type currently used in machine vision Most common sensor type currently used in machine vision Basic building block: metal-oxide- semiconductor (MOS) capacitor Basic building block: metal-oxide- semiconductor (MOS) capacitor olympusmicro.com

Interline transfer CCD Each row in the array represents a single line in the resulting image. Each row in the array represents a single line in the resulting image. Charge accumulated by each element is proportional to light intensity and exposure time. Charge accumulated by each element is proportional to light intensity and exposure time. looptechnology.com

Holography Developed prior to the laser Developed prior to the laser Requirement for light with a high degree of spatial and temporal coherence Requirement for light with a high degree of spatial and temporal coherence Method of recording information from a 3D object such that a 3D image may be reconstructed (wavefront reconstruction) Method of recording information from a 3D object such that a 3D image may be reconstructed (wavefront reconstruction) Hologram = recorded interference pattern Hologram = recorded interference pattern scienceclarified.com

Holographic recording Exact shape and distribution of interference fringes based on shape of the object and reflected wavefronts Exact shape and distribution of interference fringes based on shape of the object and reflected wavefronts Wavefront reflected from the object E ob Wavefront reflected from the object E ob U o (x,y) = complex amplitude U o (x,y) = complex amplitude U r (x,y) = reference beam U r (x,y) = reference beam Irradiance I(x,y) Irradiance I(x,y) Constant transmission T Constant transmission T Transmitted light U T when hologram is illuminated by U r Transmitted light U T when hologram is illuminated by U r science.howstuffworks.com

Holography 101 Object wavefront Reference wavefront Holographic medium Hologram Reference wavefront Reconstructed object

Photorefractive volume holography 5 Fundamental Processes: 1) Photoionization of impurities & generation of charge carriers 2) Charge carrier transport 3) Trapping of charge carriers leading to formation of space-charge density 4) Formation of photo- induced space charge field 5) Formation of index grating Beam 1 Beam 2 I x x  x E SC Intensity Charge Density Space Charge Field Index Variation  n x x The Photorefractive Effect

Optical set-up

Optical data storage 543 nm Laser Polarizer M1 L1 L2 BS3 M2 T L3 Fe:LiNbO 3 L4 CCD Block Object Reference BS2 BS1 594 nm Laser nm Laser Iris

Wavelength multiplexing

High resolution data

Holographic animation 2.51  Fe:LiNbO 3 He-Ne Laser M1 Target Object beam Reference Beam ID M2 CCD BS L1 L2 L3 BX block Filter L4

Phase multiplexing

Recorded images

Cyclic video

Special beams 0 cm5 cm10 cm15 cm20 cm25 cm30 cm35 cm

Applications Determination of surface contours for complicated shapes with diffusely reflecting surfaces Determination of surface contours for complicated shapes with diffusely reflecting surfaces Double exposure holographic interferometry: very small distortions can be measured by counting interference fringes Double exposure holographic interferometry: very small distortions can be measured by counting interference fringes Holographic computer memories Holographic computer memories Theoretically up to bits/mm 3 Theoretically up to bits/mm 3 Information is distributed across the entire hologram, not sensitive to scratches or dust Information is distributed across the entire hologram, not sensitive to scratches or dust Very high readout rate: information is recovered in parallel Very high readout rate: information is recovered in parallel Easier to align and less subject to vibration problems Easier to align and less subject to vibration problems Possible to record several holograms in different planes of a thick material Possible to record several holograms in different planes of a thick material ndt.net

Future computer memories

Optical modulators Electro-optic effect Electro-optic effect Introduces new optic axes into birefringent materials or to make naturally istropic crystals birefringent Introduces new optic axes into birefringent materials or to make naturally istropic crystals birefringent Pockels effect: linear variation in refractive index, depends on crystal structure and symmetry Pockels effect: linear variation in refractive index, depends on crystal structure and symmetry Kerr effect: quadratic dependence Kerr effect: quadratic dependence