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CCD Sensor Technology: Capacitance, Charge, Voltage, Photons

Explore the characteristics of CCD sensor technology including capacitance, charge, voltage, and photons. Learn about pixel area, resulting charge, capacitance, and photon intensity.

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CCD Sensor Technology: Capacitance, Charge, Voltage, Photons

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  1. 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? 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 0.015 V 2.2E5 electrons 6.9E14 photons/m2

  2. 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? 3.533E-11 m2/pixel

  3. 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%) 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? 3.533E-11 m2/pixel, 7.131E-13 C

  4. 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%) C) If the voltage across the pixel is 2.4 mV, what is the capacitance of the pixel? 3.533E-11 m2/pixel, 7.131E-13 C, 2.972E-10 F,

  5. 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%) 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? 3.533E-11 m2/pixel, 7.131E-13 C, 2.972E-10 F, 0.0105x

  6. 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)

  7. 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 3.7084E-10 m2

  8. 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 = 562,630 560,000 photons

  9. 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 1.5x1015 photons/m2

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