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DISTANCE DETECTION

DISTANCE DETECTION. EE 594 - Consumer Optoelectronics Dave Vu March 17, 1999. MOTIVATION. My Motives Concept is simple Why others may be interested Distance/Velocity measurement is an essential tool in many commercial and military applications

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DISTANCE DETECTION

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  1. DISTANCE DETECTION EE 594 - Consumer Optoelectronics Dave Vu March 17, 1999

  2. MOTIVATION • My Motives • Concept is simple • Why others may be interested • Distance/Velocity measurement is an essential tool in many commercial and military applications • Endless possibilities for future development and research

  3. OVERVIEW • Many ways to detect distances using wave propagation properties • visible light ( 380 - 770 nm) • infrared ( > 800 nm) • microwaves ( > 4000nm) • Best Detection Method depends on Level of Detection desired • Application Specific: Range of distance desired? Error allowed? Coherent Signals? Pros/Cons? Laser Sources

  4. BASIC CONCEPT • Emitter: Direct a beam at approaching or receding object • Receiver: Portion of beam is reflected and received by Detection Unit • Translation of Signal • Point Light Source: Flux Dens  1/distance2 • Lasers: Time dependent using ‘c’ as reference; Distance = RT / 2 • Interferometry: Phase Difference  Distance • Microwaves:  Frequency  velocity

  5. POINT SOURCE Flux Density = I / d2

  6. POINT SOURCE ERROR

  7. INTERFEROMETRY • Used for very • small distances • Coherency: • same wavelength • and phase • Phase Difference • and Position • Other Applications: • Stress/Stain Analysis

  8. MOIRE EFFECT • Mechanical Interference of light by superimposed network of lines Incident Light Specimen Grating (object) Master Grating (reference) N=0 N=1 Actual Transmitted Light N=1/2 X = N * p ; where N = Order p = pitch of master

  9. Radar Microwaves Supported by the Doppler Effect:  Frequency  velocity beam of microwave energy (~9000-28000nm) hits target and a portion of it is reflected reflected beam is shifted in frequency proportional to velocity of target => Signal Processing Scatterability Lasers Similar concept as radar except: Coherent light source sample of change in distance over a period of time Accuracy of reading are affected by: halogen lamps,weather,reflection and refraction of beam SPEED DETECTION

  10. APPLICATIONS • Commercial • Vehicles, Speed Regulation • Personal use: Room Dimensions • Maufacturing, Robotics • Military • Positioning / Locating applications • Education/Research • NASA/NSF: Shuttle missions, measurement of distance in other mediums (ie. atmospheres, space)

  11. SUMMARY • General concept with lots of potential • Many ways of interpreting and manipulating signals • The method we use to analyze it relies heavily on the requirements of the application

  12. REFERENCES • General Laser Reference Sites • http://www.fastguy.com/ • http://www.intl-light.com/handbook • Laser measurement • http://www.renishaw.com/laserscale/ • Position Determination Using Lasers • http://on-trak.com/psd • Laser Range Finders (LIDAR) • http://www.meos.com/_Pages/EXP15-ENG-NAV.htm • http://ranier.oact.hq.nasa.gov/Sensors_page/Laser/LaserOV.html • http://www.ksc.nasa.gov/shuttle/missions/sts-64/mission-sts-64.html • Distance Detection Using Interferometric Techniques • http://web.wse.nadn.navy.mil/wse/academic/courses/es300/supplem/interfer.htm

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