Elektroniska sensorer Ljusregistrering
Fotoner Energikvantum E=hv Våg och partikel egenskaper
Fotoelektrisk effekt
Fotoelektrisk omvandling
Specifications: CCD type: Sony ICX249AK EXview CCD with ultra low dark current and vertical anti-blooming. CCD pixel data: Pixel size: 8.6 x 8.3uM with 64% fill factor, image format 752 x 580 pixels CCD size: Imaging area: 6.47mm (horizontal) x 4.83mm (vertical). Spectral response: Peak response at 590nM, 30% at 400nM (Violet) and 70% at 670nM (Near infra-red). Quantum efficiency: Approx. 65% peak at 590nM. Readout noise: Less than12 electrons RMS - Parallel Port, Less than 8 electrons RMS - USB Port Full-well capacity: Greater than 70,000 e- Anti-blooming: Overload margin greater than 800x Dark current: Dark frame saturation time greater than 100 hours. Less than 0.1 electrons/ second at +10C ambient. Data format: 16 bits interline imager. Computer interface: 8 bit unidirectional parallel port with bi-directional status lines (Standard Centronics interface). 25 pin 'D' style plug for LPT1, 2 or 3, via a 5 metre x 6mm diameter cable, OR USB port design Image download time: Typically 12 seconds with a 200MHz PC and 'Fast Interface' module. USB version approximately 3.5 seconds. Power requirements: 115VAC / 240VAC @ 12VA, or 12VDC @ 750 milliamps max. Cooling system: Regulated constant-current cooling supply built-in. Single-stage thermoelectric cooler to give a CCD temperature of approximately -30C below ambient. Size: 50 x 100mm black anodised aluminium barrel with M42 thread at CCD window end and 15 pin 'D' style input plug at rear. Weight: 200g.
CCD sensorn
Photogate
Blooming
Lateral Overflow Drain
Effekter av blooming (Smear) CMOS smear CCD smear
Transport av fotoelektroner
4 phase clocking
2 phase clocking
Full frame transfer
Frame transfer
Interline transfer
Mikrolinser
CCD / CMOS
Färgregistrering
Mosaik mönster
3 pass exponering
3 chip CCD
Jämförelse
Absorption
3 Lagerteknik
Jämförelse
CCD scanning format
Framerate Approximate Frame Rate (fps) = 1 / [(Npixel / tread) + Texp] Npixel är antalet pixlar som läses ur sensorn Tread är tiden det tar att läsa av en pixel Texp är exponeringstiden
True framerate Frame Rate (fps) = 1 / (Frame Acquisition Time + Frame Read Time) Frame acquisition time components: * Time required to clear charge from the parallel register prior to beginning integration. * Shutter opening delay in CCDs employing mechanical shutters. *Exposure time. *Shutter closing delay, if any. Frame read time components: *Time required to clear charge from the serial register prior to beginning readout. *Time required for a parallel row shift times the number of rows in the array. *Serial discard time multiplied by the number of pixels not intended to be read. *Serial conversion (digitization) time per pixel times the number of pixels to be read.
Clear time Parallell clear time Seriell clear time
Utläsning och shifttime
Discard times Parallell discard time Seriell discard time
Pixel binning
Sammanfattning Frame Acquisition Time = (TPR Nclear) + Topen + Texp + Tclose T(PR) =Parallell clear time Nclear = antalet clear cykler Topen = slutarens fördröjning vid öppning Texp = exponeringstiden Tclose = slutarens fördröjning vid stängning Frame Read Time = TSR + (Trow Nrow) + (TSD Ndiscard) + (tread Nread) TSR = Serial clear time Trow = parallell row shift time Nrow = antalet rader TSD = Serial discard time Ndiscard = Antalet ej lästa pixlar Tread = den seriella omvandlingstiden per pixel Nread = antalet pixlar som ska läsas ut
Sekventiell utläsning
Simultan utläsning
Dubbla seriella register
Frågeställningar Vilka parametrar styr bildhastigheten? Vilka möjligheter finns att öka bildhastigheten
Brus Read noise (elektroniska komponenter) Dark noise (termiskt) Photon noise (fluktuationer)
Dynamic range Dynamic Range = 20 x Log(Nsat/Nnoise) Nsat = maxsignal; FWC Nnoise = min signal; Dark noise + read noise (utan exponering)
SNR SNR = Utsignal / brusnivå i utsignal
Verkningsgrad Quantum efficiency
Öka våglängdsomfånget
Bildsensorstorlek Brännvidd Faktorförlängning Bildvinkel
Övningsexempel Redogör för parametrarna i den tekniska specifikationen för Kodaks CCD
Länkar och litteratur http://www.microscopyu.com/articles/digitalimaging/ccdintro.html http://micro.magnet.fsu.edu/primer/digitalimaging/concepts/ concepts.html Teknisk Fotografi Kjell Carlsson, kap 29