Download - Multi spectral imaging
05/03/2023 2
Introduction. Electromagnetic Spectrum. Multi-Spectral Imaging. How multi-Spectral Imaging can be used. Multi-Spectral Cameras. Applications. Compression.
Content
05/03/2023 4
Blue: 450-515..520 nm. Used for atmospheric and deep water imaging.
Green: 515..520-590..600 nm. Used for imaging of vegetation and deep water structures.
Red: 600..630-680..690 nm. Used for imaging of man-made objects.
Visible Light
05/03/2023 5
RGB which lie in the visible range can be
combined to produce a full color image for viewing on a display.
But, RGB are not sufficient to specify the appearance of an object under varying illuminants and viewing conditions.
Visible Light
05/03/2023 6
Near infrared: 750-900 nm, is used primarily
for imaging of vegetation. Mid-infrared: 1550-1750 nm, is used for
imaging vegetation, soil moisture content, and some forest fires.
Far-infrared: 2080-2350 nm, is used for imaging soil, moisture, geological features, silicates, clays, and fires.
Infrared
05/03/2023 8
A multispectral image is one that captures
image data from two or more ranges of frequencies along the spectrum, such as visible light and infrared energy.
In multispectral images, the same spatial region is captured multiple times using different imaging modalities.
Multi-Spectral Imaging
05/03/2023 9
Recording data from the visible spectrum
showing an object as it is seen by the eye.
Take images in area of spectrum infrared region (invisible).
How can be used
05/03/2023 11
Multi- spectral sys tems make it pos si ble to look
beyond those bound aries. Quest inno va tions is lead ing in multi- spectral cam era tech nol ogy.
Multispectral Cameras
05/03/2023 12
Higher res o lu tion pic tures due to larger
sensors
Able to see in Wave lengths from 250 – 2200 nm
Cam eras rang ing from 1 to 5 chan nels (a reg u lar cam era is 1 channel)
Multispectral Cameras
05/03/2023 13
More chan nels show sev eral diff er ent infor ma
tion layers
Cus tomized soft ware to ana lyze every chan nel sep a rately and combined
Com pact and light sys tems (cam era, infor ma tion stor age, GPS/ IMU integration)
Multispectral Cameras
05/03/2023 14
Remote Sensing:• The sensing platform is usually an aircraft
or satellite.• The scene being imaged is usually the
earth's surface.• The sensor and the target are so far apart, so
each pixel in the image can correspond to tens or even hundreds of square meters on the ground.
Applications
05/03/2023 15
Applications
Athens as seen by the SPOT 5 satellite in 2002Spot-5 Satellite
French Spot
05/03/2023 16
American Thematic mapper sensors feature
seven bands of image data (three in visible wavelengths, four in infrared)
Applications
05/03/2023 17
VASARI SYSTEM:
• VASARI imaging system developed at the National Gallery in London.
• we are investigating the use of seven filters spanning the visible spectrum. These seven channels can be combined to give accurate measurements.
Applications
05/03/2023 19
Interpretation of ancient papyri, such as those
found at Herculaneum, by imaging the fragments in the infrared range (1000 nm).
Used for document inspection and restoration as hidden markings can be become visible in infrared.
Applications
05/03/2023 22
Medical:• Multispectral medical images can be formed
from different medical imaging modalities such as MRI, CT, and X-ray. These multimodal images are useful for identifying and diagnosing medical disorders.
Applications
05/03/2023 23
For example ,The French SPOT and American
thematic mapper are older systems, use only a handful of spectral bands.
More modern systems, however, can incorporate hundreds of spectral bands into a single image.
Compression
05/03/2023 24
It is used to minimize transmission bandwidth
from the sensing platform to a ground station and to archive the captured image.
Steps:• Transformation.
› Karhunen-Loeve (KL).› Frequency transform.
• Encoding
Compression
05/03/2023 26
The optimal linear transformation for de-
correlating the data is the well-known Karhunen-Loeve (KL) transform.
Frequency transform such as the discrete cosine (DCT) and wavelet transforms approach the optimal KL transform point much more quickly than many other transforms, so they are preferred in actual compression systems.
Transformation
05/03/2023 27
Multispectral data can be represented as a 2D
image with vector-valued pixels. Each pixel consists of one sample from each
image plane All spectral band:• sampled at the same resolution.• sampled over the same spatial extent.• are perfectly registered, so each pixel
component corresponds to the same exact location in the scene.
Transformation
05/03/2023 28
Transform-based multispectral coders is
categorized into three classes:
• Spectral-spatial transform.• Spatial-spectral transform.• Complex spatial-spectral transform.
Transformation
05/03/2023 30
Infrared band may have lower spatial
resolution than a visible band. All images:• Not the same spatial resolution.• Registered.
Spatial-spectral transform:
05/03/2023 31
A spatial shift in one image plane relative to
another. All images:• Not the same spatial resolution.• Not registered.
Complex spatial-spectral transform:
05/03/2023 32
Multispectral image compression algorithms
fall into two general categories:
• Lossy.• Lossless.
Compression
05/03/2023 33
Lossy algorithms typically obtain much
higher compression ratios but introduce distortions in the decompressed image.
• Ex.:› RGB color images.› Remote sensed data.
Lossy Compression
05/03/2023 34
The decoded image is identical to the original.
This gives perfect fidelity but limits the achievable compression ratio.
• Ex.:› Medical images.› Photographic images.
Lossless Compression