Inner structure detection by optical tomography technology based on feedback of microchip Nd:YAG lasers

Abstract

We describe a new optical tomography technology based on feedback of microchip Nd:YAG lasers. In the case of feedback light frequency-shifted, light can be magnified by a fact of 10(6) in the Nd:YAG microchip lasers, which makes it possible to realize optical tomography with a greater depth than current optical tomography. The results of the measuring and imaging of kinds of samples are presented, which demonstrate the feasibility and potential of this approach in the inner structure detection. The system has a lateral resolution of ~1 μm, a vertical resolution of 15 μm and a longitudinal scanning range of over 10mm.

Frequency-Shifted Optical Feedback Measurement Technologies Using a Solid-State Microchip Laser

“…The laser confocal feedback tomography is proposed to reach a greater imaging depth compared with the confocal microscopy or optical coherence tomography [38,39]. It also shows great performance in the structure measurement of the micro-electro-mechanical system [80][81][82]. However, the system is also challenged to realize both high resolution and large penetration depth the same as the other optical methods.…”

“…The vertical resolution is evaluated via scanning the defocus curve and measuring the full width at half maximum (FWHM), which is about 15-20 µm. The system can be applied in the imaging of the structure of the micro-electro-mechanical system [80,81]. For example, the sandwich type sample with the patterned layer etched in a silicon film of 1 mm and two pieces of 0.5 mm thick glass is measured.…”

Precision Dimensional Measurements

“…The vertical resolution is evaluated via scanning the defocus curve and measuring the full width at half maximum (FWHM), which is about 15-20 μm. The system can be applied in the imaging of the structure of the micro-electro-mechanical system [80,81]. For example, the sandwich type sample with the patterned layer etched in a silicon film of 1 mm and two pieces of 0.5 mm thick glass is measured.…”

Laser feedback interferometry and applications: a review

“…A pin tip is inserted inside the onion to show the significant improvement in detection depth; from the results, the penetration depth inside the onion can reach 2.5 mm. 133 Wang et al 134 proposed a method for microstructure measurement based on the laser confocal feedback system. The linear relationship between the optical feedback light amplitude and the defocusing amount is calibrated.…”