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Overview Example Data Calibration

HydroBeta is calibrated using a method similar to that for our single-angle backscattering sensor (details), and described in a paper published in Applied Optics.



    HydroBeta with illuminated calibration target.  During calibration the target is moved along the path of the laser beam.

    Calibration Photo
  • Calibration is referred to a Spectralon? reflectance standard, not to fluids or microspheres.
    • The irradiance reflectance of the standard is known to be 99%.
    • The radiance reflectance as a function of angle, in water, is measured by HOBI Labs.
    • A second translucent standard (used for forward angles) is calibrated with reference to the solid standard.
  • The response of each receiver to scattering throughout the laser beam is directly measured?not computed from optical approximations.
    • The target is placed in the path of the beam, and moved parallel to it.
    • The output of each receiver is measured as a function of the target's distance along the beam.
    • The resulting curves provide a complete and accurate description of the sensing geometry, which differs slightly for every channel.


Typical Response Curves (normalized)

Response Curves
Setup and Procedure


  • The target is mounted on a rail such that it intersects the beam.
  • A threaded rod allows the target position to be varied in precise increments.
  • The angle of the target is adjusted on successive runs so that it can be viewed by the various receivers.
  • For receivers at greater than 90 to the beam, a translucent target is used, and the beam scatters forward through it.


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All specifications subject to change without notice.