Spatial frequency domain imaging (SFDI), a novel non-contact optical imaging technology, is applied to the detection of
bruising on Golden Delicious apples. Quantitative absorption and scattering image maps from 650 to 980 nm are
obtained for two levels of bruising severity. While not obviously distinguishable by eye, using SFDI the severity of
these bruises, which have been created using a controlled impact device, are distinguishable from each other and from
the surrounding non-bruised region. The average scattering and absorption spectra is calculated for the two levels of
bruising and compared to the adjacent non-bruised regions. There is a considerable difference in the average reduced
scattering coefficients between the bruise and non-bruised regions for the two levels of bruising from 650 to 980 nm.
We have developed a high-bandwidth frequency-domain photon migration (FDPM) instrument which capable of noninvasively determining the optical properties of biological tissues in near- real-time. This portable, inexpensive, diode-based instrument is unique in the sense that we employ direct diode laser modulation avalanche photodiode detection. Diffusion models were used to extract the optical properties (absorption and transport scattering coefficients) of tissue-simulating solution from the 300 kHz to 1 GHz photon density wave data.
Diffraction-limited beam operation at high output power levels (0.5 W cw and 1.5 W pulsed) has been demonstrated from resonant-optical-waveguide (ROW) array structures. Uniphase mode operation is achieved without the need for active phase control. As a result, a reliable monolithic device capable of watt-range coherent output power is obtained.
Diffraction-limited beam operation at high output power levels (0.36 W cw and 1.5 W pulsed) have been demonstrated from resonant-optical-waveguide array structures. Uniphase mode operation is achieved without the need for active phase control. As a result, a reliable monolithic device capable of watt-range coherent output power is obtained.
The small signal modulation characteristics, large signal modulation characteristics and dc noise spectra on 70 micron-wide 20-element high-power phase-locked arrays of antiguides are reported. The relaxation resonance frequency at 1.5 times threshold is found to be 1.65 GHz. Large-signal pulse modulation produced no distortion to the far-field characteristics. The dc noise spectra showed a damped shot noise resonance at 1.32 GHz for a dc bias level of 1.18 times threshold.
Experimental results on the frequency modulation (FM) and linewidth characteristics of laser diodes in external cavities are presented. The laser is an uncoated 825 nm AlGaAs semiconductor laser diode. The external cavities consist of a 10X, 0.3 NA microscope objective and a diffraction grating. Measurements were made of the FM coefficient and spectral linewidth as a function of external cavity length.
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