Einleitung. BildVERarbeitung. BildBEarbeitung. Astrofotografie Farbkanäle gezielt manipulieren

Transkript

1 Einleitung BildVERarbeitung Bildanalyse Bildrestauration Photometrische Auswertung Objektdetektion Kompression BildBEarbeitung Astrofotografie Farbkanäle gezielt manipulieren Folie 1

2 Einleitung Astronomische Bildverarbeitung Filterung - Image Denoising (Entfernen von Bildrauschen, Photometrie) - Kontrastverbesserung - Deconvolution ( Bildschärfung ) - Inverse Filterung - Regularisierung - Statistische Methoden (Bayes, Entropie, ) - Super-Resolution - Bildkomprimierung - Übermitteln von Daten (Sonden), Bilddatenbanken Compressed Sensing USW. Folie 2

3 CCD-Kamera Charakterisierung Noise characteristics of CCD camera Total standard deviation <n camera > of camera noise: < n >= < n shot > + < n read > + < n pattern Camera > Pattern noise (fixed pattern noise and photoresponse non-uniformities) manifests as a spatial non-uniformity Poisson-noise (quantum nature of light) P( X = x) = x m m - -l e x! E(X) = l, Var(X) = l Gaussian read-out-noise (camera electronics) Var(X) = const. where l is the average number of occurrences (e.g. number of generated photoelectrons on the CCD) Folie 3

4 CCD-Kamera Charakterisierung Noise characteristics of CCD camera Photon transfer technique Conversion of photon numbers to CCD gray levels Plot of random noise as a function of mean signal. It gives the conversion constant used to convert relative digital units generated by the camera into absolute physical units of electrons/photons. As the illumination onto the CCD is increased, the noise becomes dominated by the shot noise/photon noise associated with the random arrival of photons Camera holder Polarisation filter pair Stepper motor Diffuser Halogen light (stabilised) Electronics Fig.2: Measurement device for PTC Folie 4

5 CCD-Kamera Korrekturen Flatfield-Korrektur Folie 5

6 Bildvorverarbeitung Image Stacking Verbesserung des SNR! Folie 6

7 Bildvorverarbeitung Drizzle Superresolution / dithering Folie 7

8 Image Denoising Folie 8

9 Image Denoising Linear Filtering Degree of smoothing depends on size of filter kernel 3x3, 5x5 and 7x7 filter kernel Folie 9

10 Image Denoising Image transform FOURIER transform x x 2D-FFT y y Ortsraum (Orts-)Frequenzraum Folie 10

11 Image Denoising Image transform FOURIER transform Folie 11

12 Image Denoising Image transform WAVELET transform Folie 12

13 Image Denoising MULTIRESOLUTION Scale 5 Scale 4 Scale 3 Scale 2 Scale 1 Folie 13

14 Image Denoising density/intensity estimate photon limited imaging Folie 14

15 Image Denoising density/intensity estimate photon limited imaging Folie 15

16 Image Denoising density/intensity estimate photon limited imaging Folie 16

17 Image Denoising Dictionary Learning Folie 17

18 Image Denoising Dictionary Learning Folie 18

19 Deconvolution Folie 19

20 Deconvolution ( Bildschärfung ) OBJEKTRAUM BILDRAUM perfektes Bild PSF (Punktverschmierungsfunktion) unscharfes Bild Ein Punkt im Objektraum wird nicht auf einen Punkt im Bildraum abgebildet, sondern auf eine mehr oder weniger ausgedehnte Fläche variierender Intensität. Folie 20

21 Deconvolution ( Bildschärfung ) Point Spread Function (PSF) in Astronomy I observed = I real PSF Easy to measure and model from several stars usually present in astro-images Determines the spatial resolution of an image Commonly used for image matching and deconvolution Ideal PSF if no atmosphere FWHM ~ 1.22 x l/d < 0.1" (8m telescope) Atmospheric turbulence broadens the PSF Gaussian PSF with FWHM ~ 1" Folie 21

22 Deconvolution ( Bildschärfung ) Point Spread Function (PSF) in Astronomy Observed PSF Inverse filter Richardson-Lucy Problem: not constant over time! 4 th object! Folie 22

23 Deconvolution Image Restoration Folie 23

24 Deconvolution Image Restoration MATLAB image processing toolbox! PSF original deblurred Folie 24

25 Deconvolution Image Restoration Wavelet based results Folie 25

26 Deconvolution Image Restoration Folie 26

27 Deconvolution Image Restoration Folie 27

28 Deconvolution Image Restoration Folie 28

29 Detection Folie 29

30 Detection Folie 30

31 Detection Folie 31

32 Detection Folie 32

33 Detection Folie 33

34 Detection Folie 34

35 Detection Object Identification Folie 35

36 Detection Object Identification Folie 36

37 Detection wavelets on the sphere Folie 37

38 Compression Folie 38

39 Compression Folie 39

40 Compression Bildkompression Folie 40

41 Compression Information - Entropie Folie 41

42 Compression Information - Entropie Background Fluctuation Analysis Folie 42

43 Compressed Sensing Folie 43

44 Compressed Sensing Folie 44

45 Compressed Sensing Jedes Pixel entspricht einer Messung Anstatt alle Pixel eines Bildes aufzunehmen, werden nur Linearkombinationen dieser Pixel aufgezeichnet (Messung) Folie 45

46 Compressed Sensing > Anstatt alle Pixel eines Bildes aufzunehmen, werden nur Linearkombinationen dieser Pixel aufgezeichnet (Messung) Folie 46

47 Compressed Sensing Folie 47

48 Compressed Sensing Single Pixel Camera (RICE University) Folie 48

49 Compressed Sensing Inpainting Folie 49

50 Compressed Sensing Folie 50