generation of multispectral filter array
DESCRIPTION
Generation of Multispectral Filter Array. Lidan Miao 01/22/04. Motivation. Color image (Color filter array). Sensing the wavelengths in the visible spectrum (400~700nm). Multispectral image (Multispectral filter array). - PowerPoint PPT PresentationTRANSCRIPT
Generation of Multispectral Filter Array
Lidan Miao01/22/04
Motivation Color image (Color filter array).
Sensing the wavelengths in the visible spectrum (400~700nm).
Multispectral image (Multispectral filter array).
CCD sensors can detect light (NIR:700~1100nm) outside the sensitivity of HVS. Additional information can be obtained from these spectral bands.
Objective CFA and MSFA
Each sensor sense one spectral band and the unmeasured spectral bands can be interpolated.
Rectangular array and Hexagonal arrayThe hexagonal grid can model the human visual system more precisely.
Design criteria of CFA
Uniform distribution Equal sample frequency. Color consistency. Spectral sensitivity.
Bayer color filter array
MSFA in the rectangle domain
Breakup algorithm Checkboard pattern
Breakup algorithm Binary tree and MSFA
Characteristics
Symmetrical and uniform distribution. Each band has the same number of
neighbors of certain spectrum and the relative position of different spectra is fixed.
The percentage of each spectrum is determined by the separation process.
(a)Equal Probability
(b)Unequal Probability
MSFA in the hexagon domain(3 methods)
Method 1 Directly apply the algorithm in the rectangle array.
“Checkboard” pattern
Method 2 Apply a new coordinate system.
(a) Coordinate system
Method 2
“Checkboard” pattern
Method 3
Based on the distance between the adjacent pixels.
Each pixel has 4 immediate neighbors (distance =1) and 4 secondary neighbors (distance = sqrt(2)).
For each pixel, half of its neighbors are chosen.
As we increase the distance, the percentage decreases.
Method 3
Limitation Cannot generate all the filter arrays with equal probability.
Rectangular array: 3, 5, 7 bands…
Hexagonal array (method 3): 4, 5, 6, 7 bands… The probability is restrict to 1/2, 1/4, 1/8,…… or 1/3, 2/3,
2/9, 1/9……
Comparison
(a) has all the characteristics in the rectangle domain.
(b) is sensitive to cross talk. (c) has the property of equal distance.
(a) Method 1
(b) Method 2
(c) Method 3
Which one do you like?