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CCD Devices Contents: Capacitance How they work Resolution Magnification

CCD Devices Contents: Capacitance How they work Resolution Magnification. Concept 0 - Capacitance. C = q V C = capacitance (Farads) q = Charge on the capacitor (C) V = voltage across the capacitor (V). demo big cap.

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CCD Devices Contents: Capacitance How they work Resolution Magnification

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  1. CCD Devices • Contents: • Capacitance • How they work • Resolution • Magnification

  2. Concept 0 - Capacitance • C = q • V • C = capacitance (Farads) • q = Charge on the capacitor (C) • V = voltage across the capacitor (V) demo big cap + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - A CCD pixel has a capacitance of 1.7x10-12 F. What is the voltage across it if it has been charged 6.0x104 electron charges? (1 e = 1.602E-19) V = q/C = (6.0E11*1.602E-19/1.7E-16) = 5.7 mV TOC

  3. Whiteboards: Capacitance 1 | 2 | 3 TOC

  4. What is the charge on a 250 microfarad capacitor if it has been charged to 12 V? q = CV = (250E-6 F)(12 V) = 3E-3 Coulombs W .0030 C

  5. What is the capacitance of a CCD pixel if it has .014 V across it when it has a charge of 2.13x10-15 C? C = q/V = (2.13E-15 C)/(.014 V) = 1.52x10-13 F W 1.52x10-13 F

  6. Example: A 3.1x10-10 m2 CCD pixel has a capacitance of 2.3 pF (x10-12) If after being exposed to light, it has picked up a charge of 3.45x10-14 C, what is the voltage across it? How many electrons were displaced from the pixel? If photons displaced these electrons, then what is the photon flux in photons/m2 incident on the CCD? (e = 1.602E-19 C/electron) V = q/C = (3.45E-14C )/(2.3E-12 F) = .015 V # electrons = (3.45E-14C )/(1.602E-19 C/electron) = 2.154E5 electrons photons/m2 = (2.154E5 electrons)/(3.1E-10 m2) = 6.95E14 photons/m2 A sunny day = about 1000 W/m2≈ 3x1021 photons/sec (550 nm) (a force of 3.3x10-6 N/m2 W 0.015 V 2.2E5 electrons 6.9E14 photons/m2

  7. How a CCD Works (Charge-Coupled Device) • Photons charge electrodes • Voltages from pixels is shifted off the chip • The voltage is converted to digital TOC www.microscopy.fsu.edu/primer/digitalimaging/concepts/ccdanatomy.html

  8. How a CCD Works CCDs only register light, color is achieved using filters TOC www.microscopy.fsu.edu/primer/digitalimaging/concepts/ccdanatomy.html

  9. jpeg compression photon memory card

  10. Resolution, sensor size and magnification Nikon D3x: (CMOS) Sensor size = 35.9x24.0 mm = 861.6 mm2 6048x4032 resolution = 24 Mega pixels Human eye: (rods and cones) Sensor size = 1100 mm2 11,000x11,000 = 121 Mega Pixels Magnification: image/object ratio Nikon D3x TOC

  11. Resolution, sensor size and magnification Nikon D3x: (CMOS) Sensor size = 35.9x24.0 mm = 861.6 mm2 6048x4032 resolution = 24 Mega pixels (Let’s assume a quantum efficiency of 70%) A) What is the area of each pixel? B) If light with a photon flux of 4.5x1019 photons/m2/s is incident on the sensor for 1/250th of a second, what is the resulting charge on the pixel? C) If the voltage across the pixel is 2.4 mV, what is the capacitance of the pixel? D) If I am 183 cm tall, and my image on the sensor is 19.2 mm tall, what is the “magnification” in this case? TOC

  12. Nikon D3x: (CMOS) • Sensor size = 35.9x24.0 mm = 861.6 mm2 • 6048x4032 resolution = 24 Mega pixels • (Let’s assume a quantum efficiency of 70%) • A) What is the area of each pixel? • total area = (35.9E-3m)x(24.0E-3) = 0.0008616 m2 • #pixels = 6048x4032 = 24,385,536 pixels • area/pixels = (0.0008616 m2)/(24,385,536 pixels) = 3.53324E-11 m2/pixel • B) If light with a photon flux of 4.5x1019 photons/m2/s is incident on the sensor for 1/250th of a second, what is the resulting charge on the pixel? • Photons per pixel resulting in charge = • (0.70)(4.5x1019 photons/m2/s)(1 s/250)(3.53324E-11 m2/pixel) = 4451884.921 • e charges per pixel • So this is (4451884.921)(1.602E-19) =7.13192E-13 C • C) If the voltage across the pixel is 2.4 mV, what is the capacitance of the pixel? • C = q/V = (7.13192E-13 C)/(2.4E-3 V) = 2.97163E-10 F = 297 pF • D) If I am 183 cm tall, and my image on the sensor is 19.2 mm tall, what is the “magnification” in this case? • image/object = (1.92 cm)/(183 cm) = .0105x (it’s a smallifier) TOC

  13. Whiteboards: Random CCD Crap 1 | 2 | 3 | 4 TOC

  14. My camera has a 25.4 mm x 58.4 mm CCD sensor with 4.0 Mega pixels. What is the area of each pixel in square meters? Area per pixel = (25.4E-3 m)(58.4E-3 m)/(4.0E6) = 3.7084E-10 m2 W 3.7084E-10 m2

  15. A pixel builds up a potential of 5.2 mV. How many photons hit it if it has a capacitance of 13 pF, and a quantum efficiency of 75%? q = CV = (13E-12F)(5.2E-3) = 6.76E-14 C # electrons = 421,972 #electrons/#photons = .75, #photons = (421,972)/.75 = 562,630 W 560,000 photons

  16. A single pixel with an area of 3.7x10-10 m2 is hit with 562,630 photons. What is the light intensity in photons/m2? photons/m2 = (562,630)/(3.7x10-10 m2) = 1.5E+15 W 1.5x1015 photons/m2

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