Multispectral Camera
Simon Belkin, Audrey Finken, Grant George, & Matthew Walczak
Final Project Review
Team Parente
Problem & Solution• Problem - Scientists desire the
ability to capture measurements based on reflected energy (radiance)
• Common camera technology only captures light in three primary wavelengths: Red, Green, and Blue (RGB) in the visible spectrum
Solution – Multispectral camera captures wavelengths throughout the entire spectrum (including near-infrared/infrared)
System Design
Final Design Review Deliverables
Filter wheel turning and stopping at each filter for period of time, capturing image, and rotating to the next filter
Aberration mitigation for all filters Transmitting captured image data from camera to
Raspberry Pi Identifying geological markers present in rocks and
soil
Filter Wheel Mechanics
Filter Wheel Mechanics FDR Solution
Program the filter wheel location in Python Replace Hall Effect Sensor and add to Python program to
identify start location Accomplished
A program turns the filter wheel. Hall Effect sensor used to recognizes start point location. With the start point location the program can turn to
specific filter and run through the filters pausing for outside response.
Filter SelectionSelected• 436nm• 670nm• 750nm• 860nm• 990nmOther• 425nm• 450nm• 510nm
Optical System
Optical System Out of focus condition due to the addition of filter wheel
required compensation. 3.75” (95.3mm) of extension tubing. A +33mm convex relay lens. Thin lens equation, 1/di = 1/f – 1/do, determines the
distance to the object, do, and to the image, di.
Required Focal Length Adjustment Cameras are calibrated to focus on the visible
portion of the light spectrum. As you travel further away from the visible spectrum and into the infrared spectrum, a slight shift in focus is necessary for camera to obtain sharpness of image.
Filter Position at Light PathCurrent Arrangement of Filter Wavelength
(nm)Dimension Needed for Focus Correction
(mm)1 Blank 9.02 425 8.53 436 8.54 450 NA5 510 9.66 will be 670nm NA7 750 10.98 860 11.09 990 11.5
10 Blank 9.0
Adjusted Lens Position (between item #2 & #3)
Pi to Camera Interface
Pi to Camera InterfaceProblem – Driver Installation Drivers provided, not officially “supported” “Fedora 5” build conversion to Raspbian “wheezy” Attempt to Cross-compile module Module compiled, but unrecognizable by OS.
Cannot start via terminal command Pi integration determined to be low priority, efforts
focused on ensuring quality image capture
Image Processing
Solution – Image Registration
Problem - aberration An optical aberration is a deviation from the optical
predictionsSolution- Image registration Image Registration is the process of estimating an optimal
transformation between two images for all filters Use of checkerboard test in Matlab to calibrate camera
Images Focused Through all Filters
Filter 2 (425nm – Visible Spectrum) Filter 3 (436nm – Visible Spectrum)
Filter 5 (510nm – Visible Spectrum) Filter 7 (750nm – Infrared Spectrum)
Filter 8 (860nm – Infrared Spectrum) Filter 9 (990nm – Infrared Spectrum)
Sift matching points on images Points from image matching points from two
images
Images after image registration
Questions