Polarization phase stepping with a savart element.

The imaging properties of a real-time shearing interferometer are presented. The use of Savart elements, both as a beam displacer and an analyzer in a polarization phase-stepping scheme, is demonstrated in a real-time, two-camera, four-bucket shearing interferometer. A simple calculation scheme for ray propagation through uniaxial, birefringent elements is presented, and the effects on the image formation through 6-cm-long Savart elements is discussed.

Fiber-coupled self-mixing diode-laser Doppler velocimeter: technical aspects and flow velocity profile disturbances in water and blood flows.

The effects of disturbances of the flow pattern in front of the fiber facet of a fiber-coupled self-mixing diode-laser Doppler velocimeter system are investigated. This was done by comparing measurements and calculations of the Doppler frequency spectrum with the expected values. The calculated Doppler spectrum was obtained from the calculation of light scattered (with or without Doppler shift) by the moving particles in front of the fiber facet. The velocity profile of the particles was calculated with a finite-element method. Measurements were done with water (with polystyrene spheres) and whole blood as the samples. Good agreement between measurements and calculations were obtained. The velocimeter was modeled as a five-mirror setup. The reflectivity of the fiber facet closest to the laser turns out to have the most influence on the sensitivity and stability of the laser. Direct reflection of unwanted light back into the laser cavity was avoided by placing a glass plate in front of the fiber. Design consi ations are presented.

A semiconductor laser used for direct measurement of the blood perfusion of tissue.

An instrument consisting merely of a semiconductor laser in its own housing was used to measure the blood perfusion in tissue. Use is made of the feedback of Doppler-scattered light to the photodiode in the laser housing. A recording perfusion of a finger under occlusion of blood flow in the arm is shown.

Self-mixing laser-Doppler velocimetry of liquid flow and of blood perfusion in tissue.

The velocimetry method of self-mixing, i.e., the feedback of Doppler-scattered light into the laser cavity, is used for the measurement of liquid flow and of blood perfusion in human tissue. The method is elucidated by the registration of the blood perfusion of a finger under repeated occlusion of the veins in the upper arm and with the velocity measurement of a liquid flow containing scattering particles.