Helmholtz tuning Forks

Outline


Speckle pattern with reduced contrast (Shown at gain 0dB)


Speckle reduction device two years ago using tuning forks driven by the I shaped electro magnet.


Up to date speckle reduction device using tuning forks driven by the U shaped electro magnet.

Tuning forks:Wittner 440Hz

tine dim. 3mm(w) 80mm(l) 10mm(spacing)

U shaped electromagnet: coil 8mm(core dia) 25mm(l) 400 turns

  Voltage amplitude sensitivity:600μm 100Hz/10Vp-p 50Hz, where the auto correlation length of the surface roughness on the diffuser is 20μm.

  • Very high Q~10^7 sinusoidal wave driven diffuser yields extremely high temporal diversity (Moving swing analogy)
  • ·Resulting speckle contrast reduction down to1/33, where K is nearly 1000.
  • ·S. Kubota and Joseph W. Goodman, “Very efficient speckle contrast reduction realized by a moving diffuser device,”published in Applied Optics vol.19 no.25, 4385-4391, 2010.

Instantaneous speckle contrast


stdv=479,while I mean=15873 resulting speckle contrast of 0.03.

Oxide Corporation

Speckle contrast Measurement System