Applying the self-mixing effect of a microchip laser to optical CT

Takashi Sekine; Kouki Shimizu; Kenju Otsuka

doi:10.1117/12.459007

13 March 2002 Applying the self-mixing effect of a microchip laser to optical CT

Takashi Sekine, Kouki Shimizu, Kenju Otsuka

Proceedings Volume 4630, Solid State Lasers XI; (2002) https://doi.org/10.1117/12.459007
Event: High-Power Lasers and Applications, 2002, San Jose, California, United States

Abstract

The self-mixing effect of a microchip laser is applicable to optical CT (Computed Tomography) because of high sensitivity to weak light of the effect. Two acousto-optic modulators were used to frequency-shift the output beam from a microchip laser by several megahertz. The beam was attenuated by passing it through a scattering object and then re-injected into the microchip laser's cavity. The self-mixing effect modulated the output intensity of the laser at a frequency of several megahertz, and the intensity of modulation was measured by a spectrum analyzer. With a ring-type optical path, which is considered to be adequate for optical CT because the light only passes through the object once, it was possible to detect a beam attenuated by more than -90 dB by neutral density filters (ND filters), and to detect a beam attenuated by INTRALIPID-10 percent solution with a concentration of 28 percent, which has the same scattering-absorption characteristic as biological tissue. By Adjusting the frequency-shift towards the relaxation-oscillation frequency of the microchip laser increased the thickness of INTRALIPID-10 percent through which transmission was possible by a factor of two. Imaging through a scattering object by using this method was demonstrated.

Citation Download Citation

Takashi Sekine, Kouki Shimizu, and Kenju Otsuka "Applying the self-mixing effect of a microchip laser to optical CT", Proc. SPIE 4630, Solid State Lasers XI, (13 March 2002); https://doi.org/10.1117/12.459007

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