Skin roughness is an important parameter in the characterization of skin and skin lesions, particularly for the purposes of
skin cancer detection. Our group had previously constructed a laser speckle device that can detect the roughness in
microrelief of the skin. This paper reports on findings made for the further miniaturization of our existing portably-sized
device. These findings include the feasibility of adopting a laser diode without temperature control, and the use of a single
CCD camera for detection. The coherence length of a laser is a crucial criterion for speckle measurements as it must be
within a specific range. The coherence length of a commercial grade 405 nm laser diode was found to be of an appropriate
length. Also, after a short warm-up period the coherence length of the laser was found to remain relatively stable, even
without temperature control. Although the laser’s temperature change during operation may affect its power output and
the shape of its spectrum, these are only minor factors in speckle contrast measurements. Our second finding covers a
calibration curve to relate speckle measurements to roughness using only parallel polarization from one CCD camera. This
was created using experimental data from skin phantoms and tested on in-vivo skin. These improvements are important
steps forward in the ongoing development of the laser speckle device, especially towards a clinical device to measure skin
roughness and evaluate skin lesions.
Daniel C. Louie, Lioudmilla Tchvialeva, Haishan Zeng, and Tim K. Lee, "Findings toward the miniaturization of a laser speckle contrast device for skin roughness measurements," Proc. SPIE 10037, Photonics in Dermatology and Plastic Surgery, 100370J (Presented at SPIE BiOS: January 29, 2017; Published: 6 February 2017); https://doi.org/10.1117/12.2253227.
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