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Title:

Laser Range Finder

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A device which uses a laser beam to determine the distance to an object ... includes the phrase 'to avoid injuring others, their property, reputation, or ... – PowerPoint PPT presentation

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Title: Laser Range Finder


1
Laser Range Finder
  • Group 3
  • Dhruv Aggarwal and Saad Raja
  • ECE 445 Senior Design
  • July 31, 2007

2
Introduction
  • A device which uses a laser beam to determine the
    distance to an object
  • Common methods of range finding include
    triangulation, multiple frequency phase shifting,
    and time of flight.

3
Features
  • USB wireless interface
  • Modular design for extension options
  • Generates a unique ID for each measurement which
    can be labeled at the base station.
  • Quick and accurate measurements can be taken off
    nearly all surfaces.

4
Laser Rangefinder Overview
  • User can work Independently
  • All the data is saved on computer which can be
    reviewed later

5
Output Source
  • Initial Plan was to use a VCSEL but due to very
    low output power the idea was dropped
  • Two Semiconductor Laser diodes were used
  • Steady output power 0.003 microW
  • Pulsed output power 3.002 microW
  • Wavelength Chosen 850nm

6
Detecting the Input
  • IR Photosensor was used to detect the reflected
    beam
  • Max sensitivity at 850nm
  • Output signal was amplified
  • using non-inverting amplifier
  • with a gain of 10

7
The Mechanics of Reflection.
  • Photosensor was placed right on top of the laser
    diode so it could detect the maximum reflected
    beam
  • Output from the sensor was amplified using a
    differential amplifier with a gain of 10
  • Output voltage from sensor was seen on the
    oscilloscope when laser beam was reflected by
    different materials

8
Oscilloscope Plots
  • Reflection off White paper
  • 10 cm 100cm

9
  • Reflection off Cardboard
  • 10cm 100cm

10
Voltage due to Reflection Vs Target distance
11
The Need for Speed
  • Time Distance/Speed? Sounds simple
  • Speed of light is 2.99792108 m/s
  • In only one microsecond the passes 300 meters.
  • A high resolution in place therefore demands
    highest resolution in time.

12
Time to Distance Conversion
  • TDC-GP2
  • If the resolution has to be 1cm we already need a
    time resolution of 67ps
  • 50ps resolution

13
Overcoming the timing limits
  • Triggersignal from laser is connected to the
    stop1 input
  • Detector signal connected to the stop2 input
  • Any further loss in signal is compensated by
    sampling

14
Wireless Data Transmission
  • Xbee radios received the UART commands from
    the PIC successfully
  • Enabled A/D conversion on one of the pins to
    do distance measurement using the voltage method

15
User Interface
16
User Interface
  • Coded using the Processing 1.0 programming
    language.
  • Reads the data from the specified USB port and
    extracts useful information from the data.
  • Gives a realtime distance output.

17
Ethical Considerations
  • The IEEE code of ethics includes the phrase to
    avoid injuring others, their property,
    reputation, or employment by false or malicious
    action , and we abide that
  • Need to be careful while working with the laser,
    it shouldnt be pointed directly into the eyes
  • Our laser is a class 3B laser which will not
    cause permanent eye damage unless there is direct
    exposure for a long duration

18
Future Hardware Development
  • Addition of a beamsplitter for more exact time
    measurements
  • Use of the TDC-GPX for a resolution of 10ps
  • Obtaining a good quality pulsed VCSEL for longer
    distance measurements.

19
Future Software Development
  • Obtaining a 2-D scan of the image by just
    sweeping the laser over the object.
  • Uploading all data to a central server for
    automated distance measurements.

20
Credits
  • Professor Gary Swenson
  • Professor Kent Choquette
  • Tony Mangognia
  • Dwayne Hagerman
  • The folks at the part shop

21
Thank You
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