We demonstrate a technique to measure the reflectance of colored objects, including blue, green, and yellow, hidden behind an opaque slab based on acoustically modulated laser speckle. One colored paper at a time was placed behind a 1 cm thick opaque slab with an air gap of 5 mm. Small periodic movements (nanometer scale) at 200 Hz were induced in the colored paper. A coherent red He–Ne laser illuminated the front of the slab, producing acoustically modulated speckle patterns, which were captured by a CCD camera. The magnitude of the time-varying speckle intensity is indicative of the hidden colored paper’s reflectance.
© 2012 Optical Society of America
Original Manuscript: July 18, 2012
Revised Manuscript: August 13, 2012
Manuscript Accepted: August 27, 2012
Published: September 26, 2012
Terence S. Leung and Shihong Jiang, "Measuring the reflectance of hidden color objects with acoustically modulated laser speckle," Opt. Lett. 37, 4092-4094 (2012)