Photothermal camera port accessory for microscopic thermal diffusivity imaging

F. ZALDIVAR ESCOLA; DARÍO KUNIK; N. MINGOLO; MARTINEZ, OSCAR EDUARDO

OPTICAL ENGINEERING

SPIE-SOC PHOTOPTICAL INSTRUMENTATION ENGINEERS

Año: 2016 vol. 55

0091-3286

The design of a scanning photothermal accessory that can be attached to the camera port of commercial microscopes to measure thermal diffusivity maps with micrometer resolution is presented. The device is based in the thermal expansion recovery technique, which measures the defocusing of a probe beam due to the curvature induced by the local heat delivered by a focused pump beam. The beam delivery and collecting optics is build using optical fiber technology, resulting in a robust optical system that provides collinear pump and probe beams without any alignment adjustment necessary. The quasi-confocal configuration for the signal collection using the same optical fiber sets very restrictive conditions on the positioning and alignment of the optical components of the scanning unit, and a detailed discussion of the design equations is presented. The alignment procedure is carefully described, resulting in a system so robust and stable that no further alignment is necessary for the day to day use, becoming a tool that can be used for routine quality control, operated by a trained technician.