Multispectral Camera

Simon Belkin, Audrey Finken, Grant George, & Matthew Walczak

Comprehensive Design Review

Team Parente

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) from the visible spectrum of light

Solution

Red = Bowline type rocksGreen = Whittaker/Hillary (Jibsheet class) Blue = bright drift soilRGB = 450nm – 650nm

System Design

Deliverables Set at CDR Build optical system

Camera can focus Capture images at different distances

Aberration solution Algorithm selected Code in progress

Stepper motor control Raspberry Pi control the stepper motor Can turn clockwise and counterclockwise

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.

Ray Tracing

Optical Distortions Aberrations due to lens occur when the light

reflected off one point of an object does not converge, (or diverge), to where it is expected to go.

Filter Wheel Mechanics

Filter Wheel Mechanics Problem

Hall Effect sensor provided in the filter wheel burned out Filter wheel doesn’t have a stable starting position

Current Solution Have a static number of rotation done through the stepper

motor to rotate from one filter location to the next Using Raspberry Pi Shell Script to turn the Filter wheel

FDR Solution Program the filter wheel location in Python Replace Hall Effect Sensor and add to Python program to

identify start location

Stepper Motor Control#!/bin/sh

gpio -g mode 23 outgpio -g mode 24 out

echo Turn Counter Clock Wise:

sleep 1

gpio -g write 24 1for i in $(seq 400); do echo $i gpio -g write 23 1 gpio -g write 23 0done

Setting gpio pin # 24 to 1 turns Counter Clock Wise and 0 Clock Wise.

Pi to Camera Interface

Pi to Camera Interface Problem

Mightex Camera Driver Installation “Fedora 5” to Raspbian “wheezy” supported by the Raspberry Pi

Current Solution Use Windows operating system to test Camera Write existing code in python which can be ported to Pi when

ready FDR Solution

Mightex Camera integrated to Raspberry Pi GPIO pins if necessary

Capture image command Store image Analyze data

Image Processing

Image Processing - Problem

An optical aberration is a deviation from the optical predictions

Optical aberration occurs when monochrome image captured with and without filter

It occurs because the optical path and focal length is modified by putting the filter wheel between the lens and the camera

Types of optical aberrations Spherical aberration Chromatic aberration

Spherical Aberrations The aberration arises because the parallel light rays of

incoming light do not converge at the same point after passing through the lens, resulting in a blurred image

Cause - filters

Lens without Spherical Aberration

Chromatic Aberrations The aberration arises because the index of refraction of

the lens material varies with wavelength, therefore the colors of the light passing through the lens refract by different amounts and produce a blurred image

Although we are using a monochromatic camera, chromatic aberration will still occur and blur the image

Solution – Image Registration

Image Registration is the process of estimating an optimal transformation between two images

SIFT (Scale Invariant Feature Transform) is used to generate a set of ‘interest’ points which can be used for tracking an image

Use the corresponding points, to calculate a homography matrix A homography matrix is a 3×3 matrix which decides the transformation

between two sets of coordinate systems RANSAC(Radom Sample Consensus) algorithm picks a minimum

number of points from a given set and estimates the model. It takes points from the set which closely fit the model and calculates

the error in the estimated model. This model ensures that only inliers are included and outliers are not

taken into account.

Image Processing - FDR Solutions

Use image registration to remove blur caused by aberrations

Use SIFT implementation and calculation of homography matrix in python, and apply a RANSAC algorithm to find the homography matrix and change the first image accordingly so that it matches the orientation of the second image

New Team-Member Roles Simon Belkin – Hall effect sensor, integration of sensor and

stepper motor code into Python

Audrey Finken – Image processing & spherical aberration mitigation

Grant George – Pi to camera interface, image storing & transferring

Matthew Walczak – Ray tracing adjustments & chromatic aberration mitigation

Final Design Review 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 Chromatic Spherical

Transmitting captured image data from camera to Raspberry Pi

Identifying geological markers present in rocks and soil

Demo

Questions

Further Reading http://

mars.jpl.nasa.gov/mgs/sci/fifthconf99/6071.pdf http://

naca.larc.nasa.gov/search.jsp?R=20030066682&qs=N%3D4294950110%2B4294726774%26No%3D10

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=04664619