Multipoint photonic doppler velocimetry using optical lens elements

Abstract

A probe including a fisheye lens is disclosed to measure the velocity distribution of a moving surface along many lines of sight. Laser light, directed to the surface and then reflected back from the surface, is Doppler shifted by the moving surface, collected into fisheye lens, and then directed to detection equipment through optic fibers. The received light is mixed with reference laser light and using photonic Doppler velocimetry, a continuous time record of the surface movement is obtained. An array of single-mode optical fibers provides an optic signal to an index-matching lens and eventually to a fisheye lens. The fiber array flat polished and coupled to the index-matching lens using index-matching gel. Numerous fibers in a fiber array project numerous rays through the fisheye lens which in turn project many measurement points at numerous different locations to establish surface coverage over a hemispherical shape with very little crosstalk.

Description

STATEMENT REGARDING FEDERAL RIGHTS[0001]This invention was made with government support under Contract No. DE-AC52-06NA25946 and was awarded by the U.S. Department of Energy, National Nuclear Security Administration. The government has certain rights in the invention.FIELD OF THE INVENTION[0002]This invention relates to photonic Doppler velocimetry and in particular to a method and apparatus for multipoint photonic Doppler velocimetry using optical lens elements.RELATED ART[0003]Photonic Doppler velocimetry (PDV) can be used to monitor movement of a curved surface that is moving along multiple points, such as during an experiment. The movement of the curved surface may occur due to an implosion, explosion, or any other force or factor that causes movement of the surface. Such movement often occurs during dynamic material experiments. These dynamic material experiments frequently involve complicated geometries and therefore large numbers of data points are a distinct advantage. Vario...

AI Technical Summary

Benefits of technology

The patent describes a probe that uses a special lens to collect laser light from a large area of surface. The lens is designed to minimize beam diameters and back reflections. The probe has a fiber array that sends laser light through the lens to create a wide-angle beam. The fiber array is coupled to the lens using index-matching gel, which simplifies assembly and focusing. The probe can be flat polished and used in areas where increased measurement point density is needed. It can also use smaller diameter optical fibers to increase surface density coverage. Overall, the probe provides excellent signal collection with minimal interference.

Problems solved by technology

Various solutions have been proposed to record the movement of the surface, but each of these various solutions suffer from various drawbacks.

However, longer pins can interfere with the surface movement and interfere with the shorter pins.

As a result, data may be corrupted by the interference.

In addition, data is only collected by a pin when that pin contacts the moving surface.

Moreover, a dense array of pins at many lengths is needed and this density may not be possible to achieve while also achieving desired data recordation.

This solution provided optic monitoring but it suffered from being size limited.

As the number of optic fiber points is increased, this probe eventually comes to its limit in how small the entire group can be made, while still having reasonable optical fiber bending radii.

Images