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Cheap, portable, optical scanner

Discussion in 'Electronic Design' started by Tom Potter, Mar 19, 2005.

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  1. Tom Potter

    Tom Potter Guest

    I am interested in analyzing surfaces of objects
    to detect natural and man-made shaping of the object surface,
    and I have been experimenting,
    using a MP3 player/recorder to record the sound,
    as I drag various fabrics attached to the player across the objects.

    Fingerprint scanners operated about 500 DPI,
    and the "ridges" that I want to "transducer"
    are a little coarser than that.

    I have experimented with various "transducer interface materials"
    glued onto the MP3 player, and I have not found a
    suitable material, as all materials have many
    resonances, and those, combined with the
    resonances of the MP3 players I have used,
    tend to obscure the data associated with the surfaces,
    that I want to analyze.

    I would appreciate any input and ideas about
    producing an audio signal that models a surface,
    in a small portable, inexpensive package.

    A small, low-power, laser probe would probably do a better job,
    and I am hopeful of using an MP3 player/recorder for this,
    as the cost, size, power consumption and frequency response
    seems to be ideal.

    Does anyone have any input on how
    an optical mouse might work as a surface scanner,
    and how it can be interfaced to an MP3 player?

    The data from the MP3 player would be downloaded into
    a PC and analyzed. I have experimented with a number of
    time series analyzer programs such as SigView,
    and would also appreciate any suggestions on how to best present the data,
    so it could be interpreted by a layman.

    Thanks in advance for any help you can provide.
  2. I read in that Tom Potter <>
    A pickup cartridge for vinyl records is made for this job. You would
    need an amplifier to connect it to the MP3 player.

    There are two sorts of cartridge - piezo electric and magnetic. The
    piezo type has an output proportional to stylus displacement, but the
    sensitivity steps down from the low-frequency value at 500 Hz and below
    to half that value at 2 kHz and above (roughly). The piezo type is a
    capacitive source and requires an amplifier with a high resistive input

    The magnetic type has an output proportional to stylus speed, with the
    above stepped response superimposed on that. It has an inductive and
    resistive source impedance and requires a specific resistive load,
    normally 47 kohms.
  3. Guest

    Are you actually MP3-compressing the received data? I would be very
    concerned that you're losing important information there. MP3 was
    designed to reproduce audio, it wasn't designed as a general-purpose
    compression algorithm for analog data capture sessions.

    It sounds like each of these samples is probably not very large, can
    you capture them without compression, i.e. as raw PCM data?
  4. Yukio YANO

    Yukio YANO Guest

    Use a Webcam, and if necessary put a magnifying lens in front !
    Why are you trying to build an ACOUSTIC Force Microscope to examine
    Macroscopic Objects !

    Yukio YANO

    a retired Scanning Electron Microscope person.
  5. Wim Ton

    Wim Ton Guest


    Maybe the reading head of a CD-player?

  6. Tom Potter

    Tom Potter Guest

    Thanks for the input.

    I will try this,
    if I can't come up with a suitable optical device.
  7. Tom Potter

    Tom Potter Guest

    I am experimenting using the wave recording feature
    of MP3 players, and this works okay,
    except for the resonances in my MP3 player cases,
    and in my "transducer interfaces".

    As far as I know,
    no MP3 player compresses the audio input.

    In other words, they have an MP3 decoder,
    but not an MP3 encoder on the chip.

    But that said, it really doesn't matter if it
    compressed to MP3 or not,
    as lossy encoding won't affect my analysis much.
  8. Tom Potter

    Tom Potter Guest

    A webcam would generate too much data.

    I need a small, cheap, low power, portable device
    that can be plugged into a computer USB port.

    ( This is for a possible consumer product.)
  9. Tom Potter

    Tom Potter Guest

    Sounds like a good idea!
    Maybe I'll try this.
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