Spectroscopic equipment. Multispectral Imaging

Transcription

1 Spectroscopic equipment Multispectral Imaging

2 Basic spectroscopic arrangement Source Sample Analyzer Detector Sun Lamps Lasers LEDs Synchrotron Plants Forests Tissue Cells Flames Chemical compounds etc. etc. Filters Spectrometers Monochromators Photodiodes Photomultiplier tubes CCD cameras Image intensifiers

3 Light sources: Sun Planck radiator Spectral distribution of the sun

4 Light sources: Sun

5 Light sources: Sun Atmospheric vertical absorption and its origin

6 Light sources: Incandescent lamps

7 Light sources: High pressure lamps

8 Light sources: Line light source

9 Light sources: Line light source Energy Atom or Ion Natural line width

10 Light sources: Line light source Doppler broadening

11 Light sources: LED

12 Light sources: Laser Light Amplification by Stimulated Emission of Radiation Excited state λ λ Ground state λ Monochromatic High intensity Mirror Gain medium Mirror Directional

13 Light sources: Laser

14 Light sources: Laser diode

15 Light sources: Synchrotron Electrons accelerated give rise to electromagnetic radiation compare an antenna or Bremsstrahlung in nuclear physics Storage ring with user beam lines

16 Light sources: Synchrotron For a dipole For relativistic electrons

17 Light sources: Synchrotron

18 Light sources: Synchrotron Max IV, Lund - 3GeV Ring

19 Basic spectroscopic arrangement Source Sample Analyzer Detector Sun Lamps Lasers LEDs Synchrotron Plants Forests Tissue Cells Flames Chemical compounds etc. etc. Filters Spectrometers Monochromators Photodiodes Photomultiplier tubes CCD cameras Image intensifiers

20 Analyzers: Spectral filters Interference filters

21 Analyzers: Dispersive elements

22 Analyzers: Prism spectrometer

23 Analyzers: Grating spectrometer

24 Analyzers: Grating monochromator

25 Analyzers: Fourier transform spectrometer

26 Analyzers: Fourier transform spectrometer

27 Basic spectroscopic arrangement Source Sample Analyzer Detector Sun Lamps Lasers LEDs Synchrotron Plants Forests Tissue Cells Flames Chemical compounds etc. etc. Filters Spectrometers Monochromators Photodiodes Photomultiplier tubes CCD cameras Image intensifiers

28 Multispectral in every day life Eye sensitivity

29 Visual appearance Color schemes

30 Color vision test

31 Detectors: Photodiode Front contact (Anode) Insulation p+ active area - + n- region Depletion region n+ back diffusion Back contact (Cathode)

32 Detectors: Photomultiplier tube Photocathode Na 2 KSbCs AgOCs Dynode For electron multiplications CsSb Cathode Slats Grid Cathode Grid Anode Anode Cathode a) b) Anode Cathode Anode c) d)

33 Detectors: CCD camera Light focused onto CCD chip Each capacitor results in one pixel a pixel is a picture element with no internal detail Number of pixels on the chip determines resolution of camera Commonly 3-5 Megapixels

34 Detectors: CCD camera

35 Detectors: CCD camera

36 Detectors: CCD camera Charge moved though chip by bucket brigade transfer charge on final capacitor is read off

37 Detectors: CCD camera Schematic potential well diagram for transport of photo-charges along one direction in the CCD-chip

38 Detectors: CCD camera Color CCD?

39 Basic spectroscopic arrangement Source Sample Analyzer Detector Sun Lamps Lasers LEDs Synchrotron Filters Spectrometers Monochromators Photodiodes Photomultiplier tubes CCD cameras Image intensifiers

40 Detectors: CMOS camera Recently, CMOS s have become more used in cheap cameras instead of CCD s CMOS stands for Complementary Metal Oxide Semiconductor. Each pixel has a circuit on the chip to convert the charge to a voltage. The camera often also include an analogue-to-digital converter.

41 Detectors: CMOS camera Advantages Compact Cheap Low power Fast readout Plug & Play Disadvantages Nonuniform Dark areas

42 Detectors: Infrared array detector InGaAs arrays are required for spectral analysis in the near to middle infrared ( µ m). High performance multichannel detectors for this spectral region are a recent development. The vast majority of detectors sold today are based on silicon technology which only operates on the shorter wavelength side of the NIR region (< 1.1 µ m).

43 Detectors: Micro-channel plate image intensifier

44 Detectors: Micro-channel plate image intensifier

45 Detectors: Image intensified CCD cameras The features of the new ICCD range include: Single photon sensitivity 15 bit dynamic range in a single scan Gating withs in the order of ns (ps with special image intensifiers) Compact head and controller A wide selection of photocathode options Easy interfacing to delay generators and lasers Modern sealed design - no nitrogen flush Thermoelectric air-cooled convenience

46 Detectors: Detector parameters Sensitivity = signal/optical power [V/W or A/W] Spectral response/spectral sensitivity/quantum eff. Signal-to-noise = S/N = Vsignal/Vnoise Noise Equivalent Power = NEP If P=NEP then SNR=1

47 Detectors: Spectral response

48 Detectors: Spectral response CCDs ICCDs

49 Detectors: Spectral response Spectral response if ICCDs

50 Basic spectroscopic arrangement Source Sample Analyzer Detector Sun Lamps Lasers LEDs Synchrotron Filters Spectrometers Monochromators Photodiodes Photomultiplier tubes CCD cameras Image intensifiers

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