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Sensory Information Processing (2)

Sensory Information Processing (2). Introduction of image sensors. Topics. Outline of image sensors History of image sensors Cameras and photography Broadcasting, movie and video Electronic / digital imaging Components of image sensors Optics, imaging device, signal line, capture

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Sensory Information Processing (2)

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  1. Sensory Information Processing (2) Introduction of image sensors

  2. Topics • Outline of image sensors • History of image sensors • Cameras and photography • Broadcasting, movie and video • Electronic / digital imaging • Components of image sensors • Optics, imaging device, signal line, capture • Approximation of image sensor • Geometry of the camera

  3. History of photography • １８３９ daguerreotype (silver plate) • １９００ roll film • １９３５ color film • １９３２ 35mm film still camera(Leica) • １９３０-５０ rangefinder cameras • １９５０-６０ SLR (Single lens reflex) camera • １９６０-７０ auto exposure • １９７７ autofocus • １９９５ digital camera (casio QV-10) ..mainly not for image quality improvement, but just for convenience

  4. finder baseline Double image Rangefinder camera（1940-1960) • Rangefinder camera (1958, 2000)

  5. Focusing screen(ground glass) SLR(1959) • What you see is what you get!

  6. Electronic / Digital imaging • Difference between film and digital camear is only at imaging device • Ex. Digital SLR / film SLR

  7. What matters for image quality? • For convenience • cost • Small / light • Do up-to-date cameras have high performance in image quality? • 8bit quantization • Number of Pixels • Cheap, small lens • Imaging sensor vs. film • Compression (JPEG) Lens for aerial survey : Aviogon (1952, design by L. Bertele) Field of view : 96 deg Distortion : under 0.008%

  8. Broadcasting / video NHK • １８８４ mechanical scan TV • １８９７ Braun tube • １９２５ Invent of TV broadcast • １９３０ Invent of imaging tube • １９５１ Development of VTR • １９５３ NHK started TV broadcast • １９６０ Color TV broadcast in Japan • １９８５ CCD Video camera for consumer • ２０１１ Analog broadcast discontinue 歴史

  9. I/O of image(side talk) Braun tube 1843 : prototype of facsimile Both transmitter / receiver have synchronized pendulum with needle for readout / recording Imaging tube

  10. Condenser lens Light source Projectors and cameras CCD lens LCD panel lens Very similar construction

  11. What is the key for image quality? • Camera is generally just a box • There is no much variation for CCD or film  Lens is the key for photograph • You are already satisfied by the number of pixels, but not for image • For the geometric measurement, the lens is the key for preciseness • Most lens has the distortion around 1-2%

  12. Camera How the image is recorded electrically? What is the artifact of CCD? How to select the CCD? CCD CCD driver / Signal processing Digital Capture lens What is principal parameter of the lens? What is aberration? What is the image degradation by lenses? How to select the lenses?

  13. Camera How the Synchronize and Sampling is performed? CCD CCD driver / Signal processing Digital Capture lens How to drive the CCD? How the color value is recovered?

  14. What is the ideal image sensor? • Similar image should be captured for the plane perpendicular to the optical axis • No distortion • No defocus (blurring)

  15. Pinhole camera • Image is formed through small “pinhole” • Pro : There is rigid Geometric relationship between the subject and image • Con : image is too dark (to slow)

  16. What is the lens? • Collect enough light on the image sensor • For measurement, image should be similar to the pinhole camera as possible • No distortion, sharp picture It is impossible by simple single lens • No defocus (trade-off with the speed) lens Image sensor / film

  17. Ideal lens h • The image is similar to the subject • Geometric condition • No distortion • No image unsharpness • Photometric condition • The lightness is uniform aberration

  18. Components of imaging optics • Lens system • Mostly ３～１０ elements • >20 elements for zoom lens • Aperture • deal the trade-off between light and defocus Nikkor

  19. Example of the lens Combination of varied type and shape of the lenses

  20. Why we need many elements? • For correcting monochromatic aberration • Thin lens with high index glass • Thick lens with low index glass • For correcting chromatic aberration There are some differences for aberration even if the focal length is same White light Longitudinal chromatic aberration of single lens F spectrum(blue) C spectrum(red) d spectrum(green)

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