ColourIt

ColourIt

Team Members: Julie Chao [email protected]

Linda Ni [email protected]

Bill Yang [email protected]

• Members of CoulorSense Inc.– Julie Chao, CEO– Linda Ni, Project Manager– Bill Yang, CTO

Reveals True Colours

Introduction of ColourSense Inc.

• ColourIt

– Background and Advantages

– System Overview

– Functionality

– Design and Reasoning

• Final Stage Prototype

– Usability and Reproducibility

– Different Applications

– Difficulties Encountered

• Future Work and Conclusion


Overview


Vision Background • Visual System in Human Eye

–Retina: contains light receptors

–Rods–Cones that absorbs red light (long-wavelength)

–Cones that absorb green light

–Cones that absorb blue light (short-wavelength)

Colour Model and Colour Space• A colour model is an abstract mathematical model describing the way colours

can be represented typically as three or four values or colour components. • RGB (addictive colour mixing) and CMYK (subtractive colour mixing) are

colour models. • sRGB, Adobe RGB, HSV (hue, saturation, intensity) are colour spaces.

addictive subtractive


Colour Background

http://en.wikipedia.org/wiki/Image:AdditiveColorMixing.png

http://en.wikipedia.org/wiki/Image:SubtractiveColorMixing.png


Introduction of ColourIt

Area of Interest

Colour Sensing Unit

Central Control Unit

UserInterface Unit

White LEDs

Colour Sensor

Micro-controller

Reflected light LCD

Screen

RGB values 255,

0, 255

Block Diagram of Overall System


Power Specifications

• System Requirement:– Input 5.0V, load current 60mA

• Solution:– Input 9.0V, output 5.0V– +5V voltage regulator: LM341 (needs min 7.2V)– Battery: 9V, 625mAh (25X16X44mm)– Advantage: easy to implement, easily accessible battery– Cost: $4 battery, $1.50 chip


Sensor Unit Specifications

• White light must be evenly distributed• 4 LEDs centred around sensor• Dimensions: 20-25mm in diameter

13 mm height


Operation Flow ChartInitialization

N

Y

Sample and display RGB values of colour

on LCD

N

Y

N

Power on

Sample? Hold more than 2 seconds?

Toggle?

White calibration

Enable or disable illuminating LEDs

Black calibration

Y

Y

N

Hold more than 2 seconds?


Purpose of White & Black Calibration

Wavelength

Ou

tpu

t F

req

ue

ncy

Fwhite

Fblack

Colour Seen by Sensor =

Colour of Target Surface

Inner Wall Colour of

Tube+

Ideal Fwhite

Ideal Fblack


Coversion to RGB

Wavelength

Ou

tpu

t F

req

uen

cy

Fwhite

Fblack

Fsample

Range

Delta

B = Range

DeltaX 255

Same Calculation for R and G

Uncertainty = +_ 1


Correction MatrixX = M · T

X = The corrected RGB values

M = 3X3 correction matrix

T = RGB values measured by ColourIt

M can be approximated by using fminserch() function in Matlab to find the optimum correction matrix that minimize the sum of the root mean square errors of each RGB pairs in the X and T matrix

Colour Checker


Colour Standards

• Book: Color Harmony by Cailin Boyle– Problems: Inconsistency, inaccuracy– Printing always effects actual colour

• Better: ColorChecker checkerboard– 24 scientifically prepared colors– Objects of special interest (skin, foliage, sky)– Reflect light same way

– Colours match natural objects under any illumination and with any color reproduction process


Desired Packaging

• Original vision• Desired dimensions: less than 120X40X30 mm (body)• Light, portable, compact• Make use of existing parts

– Pipes, flashlights, tubes, switchboxes, conduit bodies


Final Packaging

• Used conduit body: E986D• Features:

– Plastic– 20 mm entry hole– Removable lid– Body dimensions: 77X27X26

• Problems: – Barely enough space– Next size, E986E, triple of E986D– Solution: milled out interior


Demonstration

Pink255,192,203

Blue0,0,255

Violet238,130,238

Navy0,0,128

Magenta255,0,255

Cyan0,255,255

Purple128,0,128

Lime0,255,0

Yellow255,255,0

Maroon128,0,0

Orange255,165,0

White255,255,255

Red255,0,0

Gray128,128,128

Brown165,42,42

Black0,0,0

Documents

ColourIt