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Imaging (now digital)

Imaging (now digital)

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Imaging (now digital)

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  1. Imaging (now digital)

  2. The stately history of analog photography • Leonardo da Vinci – cameras obscura – 1519 • Photosensitive materials explored – 16xx – 1830 (and beyond) • Daguerrotype – 1839 • Wet Plate processes – 1860 • First impact on public awareness of the wider world • Color photography – 1868 (first plausible process) • Small cameras (Leica, Ermanox, Rolleiflex) 1914 – 1920s • Japanese entry into camera business – 1950s • Automation • Auto exposure – 1960-64 • Auto focus – 1980 • Film phaseout in favor of digital – 1990 to 2010

  3. The Pixel Race • The roots of digital imaging – 1960s and 1970s • CCD and CMOS photosensors first developed (1969 CCD patent) • Cold War spy satellites needed to eliminate dropping film by parachute! • CMOS – cheaper to manufacture, lower basic quality, able to add image processing on the same chip to compensate • CCD – nonstandard process, more expensive (and often uses outdated facilities) higher quality, but unable to integrate • Quickly dominated optical astronomy • The transition in cameras for terrestrial use • 1985 introduced digital camera backs ($100K) • Mid 1990’s – professional and consumer cameras • Present status (e.g. Olympus) • Since 1950s still supports 22 film cameras, sells about 8 more • Since 1996 still supports 46 digital cameras, selling 40 more

  4. What’s inside a digital camera • Simplest case: tethered camera • Fixed focus (simple lens in a threaded mount) • Two chips

  5. How to capture colors

  6. Standard (Bayer) imager layout

  7. Nonstandard Imagers • Novel layouts (Fuji) • Conventional array has greatest resolution along the 45 degree axis. Why not tilt the array to maximize x and y resolution instead…? • Fuji is also exploring split cells to enhance dynamic range • Novel 3-color single cells (Foveon)

  8. We’re not done yet – other tasks • Automatic exposure • Automatic focus • Active – passive • Passive is dominant for digital • Most common scheme is contrast enhancement, based on the actual image • Better is phase sensitive detection, since it gives direction in which to correct

  9. How big is digital film? • Digital backs support astronomical pixel arrays ($20-50K) • 20 - 25 Mpixels and 60 x 45 mm substrate • Highest quality digital SLRs (Nikon, Canon at $8-10K) • 8, 12, 16 Mpixels and 24 x 35 mm substrate • “full frame” 35 mm • New “low end” DSLRs (Nikon D70, Canon 20D, Olympus E-1) • 5-8 Mpixels, “magnification factor of 1.5 (APS) to 2 (4/3) • Consumer digicams (use 2/3, 1/1.8, … tiny chips) • “prosumer” 5-8 Mpixels, non-interchangeable lens < $1000 • “consumer” 3-5 Mpixels, point and shoot <$400 • Lenses must shrink to match imager sizes

  10. Side Effects in the MPixel Race • Using whole cell for imaging gives best dynamic range, lowest noise, greatest sensitivity • This sacrifices video output (used in LCD viewers) • Drawbacks of fractional cells compensated by microlenses • Lens design for smaller image areas is different • Short back focus • Need to restrict angle of light • Wide angles become normal

  11. Where is(was?) the quality crossover? • Goto Norm Koren’s discussion • www.normankoren.com • www.imatest.com

  12. Where can we go with this? • What type of image taking is a digital camera not good for? Why? • The relationship between image resolution and information • Face recognition • Text recognition • Object recognition • Develop a rough spec for a camera that does one of the following ON-BOARD • Text translation (OCR) • Continuous wireless upload • Wireless printing • Gesture learning and recognition (for shoot still, shoot video, stop video, etc) • Motion detection and alarm • Face learning and recognition • Object learning and recognition • Visual temperature detection and alarm NOW let’s make the camera we need for our application: • Given a power supply, an imaging chip, and flash memory, what would you need to do to make your own digital camera? What additional parts will you need?