DEVELOPMENT OF A COLOR IDENTIFICATION DEVICE FOR THE pages.hmc.edu/harris/research/ آ  SEVEN LED...

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Transcript of DEVELOPMENT OF A COLOR IDENTIFICATION DEVICE FOR THE pages.hmc.edu/harris/research/ آ  SEVEN LED...

  • DEVELOPMENT OF A COLOR IDENTIFICATION DEVICE FOR THE BLIND

    Project Teams:

    Fall 2000 Spring 2000 Fall 2001 Christine Paulson Christine Paulson Nils Kapp

    Martin Weiner Martin Weiner Dmitriy Kogan Christine Paulson

    Aaron Stratton

    Advisor: Dr. David Harris

    December 21, 2001

    i

  • ABSTRACT

    Currently, the blind depend on various methods for matching clothing. These include memorizing placement in a closet, reading Braille tags, and relying on friends and family for help. For the purpose of alleviating these dependencies, the goal of this project is to engineer a speaking device that identifies the color of a piece of material placed in front of it. This project involves two components. The first is the development and calibration of a sensor to obtain a well-defined output for each color. The second is the development of a system that takes data from the sensor, determines the color from the calibration, and announces the color to the user. A functional prototype was developed during the second semester of the project that correctly identifies greater than 90% of the colors used for calibration. The prototype is significantly less accurate on new fabrics and colors. The speech playback capabilities are effective.

    ii

  • TABLE OF CONTENTS

    ABSTRACT .......................................................................................................................................................II

    1. INTRODUCTION ....................................................................................................................................1

    2. BACKGROUND INFORMATION ........................................................................................................1 2.1. HUMAN PERCEPTION OF COLOR..........................................................................................................1

    3. FIRST SEMESTER DEVELOPMENT..................................................................................................2 3.1. FIRST SEMESTER CONCEPTUAL DESIGNS .........................................................................................2 3.2. FIRST SEMESTER RESULTS.................................................................................................................3

    4. SECOND SEMESTER DEVELOPMENT.............................................................................................5 4.1. SECOND SEMESTER GOAL ..................................................................................................................5 4.2. SEVEN LED PROTOTYPE – “BLINKY” ................................................................................................5 4.3. EFFECTIVENESS OF “BLINKY” PROTOTYPE ........................................................................................6 4.4. SPEECH PLAYBACK.............................................................................................................................6 4.5. COLOR IDENTIFICATION METHOD ......................................................................................................7

    4.5.1. MC8HC908KX8 microcontroller .................................................................................................7 4.5.2. Assembly Code and Color Identification Algorithm.....................................................................8

    5. THIRD SEMESTER DEVELOPMENT ................................................................................................8 5.1. THIRD SEMESTER GOAL .....................................................................................................................8 5.2. SPECTROPHOTOMETER PROTOTYPE – “PINKY” ..................................................................................8 5.3. FILTERED PHOTODIODE PROTOTYPE – “INKY”...............................................................................10

    5.3.1. Preliminary Amplifier Circuit.....................................................................................................11 5.3.2. Data Interpretation.....................................................................................................................12 5.3.3. Reproducibility ...........................................................................................................................12 5.3.4. Signal Noise................................................................................................................................13 5.3.5. Top Compression Logarithmic Amplifier ...................................................................................14 5.3.6. Dmitriy’s Amplifier.....................................................................................................................16

    5.4. COLOR RECOGNITION IMPROVEMENT IDEAS....................................................................................17 5.4.1. Data Interpretation.....................................................................................................................17 5.4.2. Tuning the logarithmic amplifier through simulation ................................................................17 5.4.3. Packaging revisions....................................................................................................................18 5.4.4. Usage of 2 LUT’s and 2 Light Intensities...................................................................................18

    A. BLINKY’S ASSEMBLY CODE............................................................................................................20

    B. INKY’S ASSEMBLY CODE.................................................................................................................31

    C. COMPONENT DATA SHEETS ...........................................................................................................43

    iii

  • LIST OF FIGURES FIGURE 1: WAVELENGTH SENSITIVITY OF THE THREE TYPES OF CONE CELLS IN A HUMAN EYE.........................2

    FIGURE 2: A FIRST SEMESTER PROTOTYPE THAT FILTERS REFLECTED LIGHT AT DETECTION .............................3

    FIGURE 3: A FIRST SEMESTER PROTOTYPE THAT FILTERS LIGHT BEFORE REFLECTION ......................................3

    FIGURE 4: FINAL FIRST SEMESTER PROTOTYPE ...................................................................................................4

    FIGURE 5: OVERLAPPING LED EMISSION SPECTRA (APPROXIMATE)...................................................................6

    FIGURE 6: CHIPCORDER SCHEMATIC ...................................................................................................................7

    FIGURE 7: DIAGRAM OF THE “PINKY” SPECTROPHOTOMETER PROTOTYPE ..........................................................9

    FIGURE 8: HAMAMATSU PHOTODIODES .............................................................................................................10

    FIGURE 9: WAVELENGTH SENSITIVITY OF THE HAMAMATSU PHOTODIODES .....................................................10

    FIGURE 10: FILTERED PHOTODIODE PROTOTYPE – “INKY" ................................................................................11

    FIGURE 11: PRELIMINARY AMPLIFIER CIRCUIT..................................................................................................11

    FIGURE 12: INKY’S DARK BLUE AND BLACK DATA CLUSTERS..........................................................................12

    FIGURE 13: TWO STAGE “TOP-COMPRESSING” OP AMP SCHEMATIC.................................................................15

    FIGURE 14: CONFIGURATION OF DMITRIY’S AMPLIFIER.....................................................................................16

    iv

  • LIST OF TABLES TABLE 1: SEVEN LEDS SELECTED FOR “BLINKY” .................................................................................................5

    v

  • 1. INTRODUCTION

    Currently, the blind depend heavily on their friends, family, and their memory to match clothing. During the summer of 2000, Sheena Iyengar, a blind professor at Columbia University, suggested that a talking color identification device would be extremely helpful to her and other people who are visually impaired. The goal of the project is to develop a handheld device to detect the color of a piece of fabric and announce the color to the user. The project is divided into two parts: color detection, and color readout. After two semesters of working on the project, both the color detection and the voice readout portions were functional, though further developments and refinement were necessary. The goal of the third semester was to explore new approaches that would result in higher color recognition accuracy. The purpose of this report is to document the design, calibration, and effectiveness of the devices made. It is organized to demonstrate the design process, development, calibration and evaluation of the prototypes.

    2. BACKGROUND INFORMATION

    2.1. HUMAN PERCEPTION OF COLOR The perception of color depends on the physical characterization of light entering the eye, as well as physiological processes after light enters the eye. Within the human eye, the retina contains cone cells, which are sensitive to a specific range of light wavelength, and rod cells, which are sensitive to the intensity of light. The rod cells allow sight in very low intensity light conditions. Since only the rod cells function during very low light conditions, no differ