An illuminator (e.g., laser) produces a light beam that partially passes through, and is partially blocked by, a mask contrastingly patterned via non-transparent and transparent portions. The mask-conformed light passes through a lens so that the mask's pattern is projected into fluid seeded with a luminescent substance, which illuminatively reveals an image of the mask's pattern. The light beam can also be expanded and/or diffused prior to reaching the mask. Instead of or in addition to transmi...

A holographic optical element transforms a spectral distribution of light to image points. The element comprises areas, each of which acts as a separate lens to image the light incident in its area to an image point. Each area contains the recorded hologram of a point source object. The image points can be made to lie in a line in the same focal plane so as to align with a linear array detector. A version of the element has been developed that has concentric equal areas to match the circular fri...

A laser Doppler velocimeter which can measure fluid flow in three dimensions, employing a laser beam projected through a rotating diffraction grating and spaced lenses, with a beam splitter in the major optical path between two lenses ahead of the flow channel through which the fluid passes. Selected pairs of laser-derived beams are directed through the fluid and intersect at a predetermined point in the fluid. The movement of the particles through interference patterns formed by the intersectin...

A method for identifying and determining the frequency of scattered radiation fringe patterns for applications such as particle or droplet sizing and laser Doppler velocimetery. The method utilizes a series of windowed Fourier transforms performed on an intensity profile of the scattered radiation to locate a segment where a fringe pattern is located on the intensity profile. A standard Fourier transform is then performed on the segment to determine a dominant frequency of the fringe pattern, fr...

A novel technique using an acousto-optic modulator (AOM) as part of a heterodyne interferometer which measures optical path differences between a test signal and a reference signal is disclosed. An array of distinct frequencies are used to drive the AOM, yielding a spatially dispersed array of frequency-shifted subaperture beams of the test signal which are interfered with the wavefront to be measured and then combined with the dispersed reference signal. The frequency shifting of the AOM allows...

In the case of a method of detecting wind velocities by means of a Doppler-lidar system (10), a laser beam of a defined frequency generated by means of a laser (11) is emitted by a transmitting device (12) toward a space area and the light backscattered from the space area is received by means of a receiving telescope (13). For determining a Doppler shift, an interferogram is generated by means of an interferometer (16), the intensity distribution of the interferogram being directly measured by ...

A method is provided for adjusting a laser doppler anemometer (1-5) having an emitting optic (3) which emits at least two laser beams (7, 8), and a receiving optic (4) for gathering light scattered by dispersed particles. The method comprises the steps of coupling a laser light (17) into an output of the receiving optic to make a focal point (12) of the receiving optic visible on a spaced reference surface (13); adjusting the receiving optic with respect to the surface so that the focal point of...

An optical velocimeter probe a device to illuminate a volume of measurement in which there may pass particles, and an optical detector to produce an electrical signal x(t) in response to the passage of a particle in the illuminated volume. It also includes a device to extract information representing the velocity v of particles from the electrical signal, including, in particular, a device to convert the electrical signal x(t) into a complex signal .sub.x (t), an apparatus to set up a self-corre...

The present invention applies to the art of wind sensing using lidar, and in particular to the art of detecting the speed of objects such as air-borne particles and molecules in the atmosphere in order to determine the speed and direction of the wind which is carrying them. The present invention is a beam director for directing a beam transmitted from a lidar at objects to produce backscattered light and for directing the backscattered light into a lidar receiver. The preferred embodiment of the...

The present invention relates to a laser anemometer making it possible to determine the relative velocity between the anemometer and an ambient medium. The architecture of the anemometer includes a laser source, emission and reception optics for focusing a laser beam onto a measurement zone containing particles in suspension in the ambient medium and for receiving the radiation back-scattered by the particles. It also includes an optical mixer for mixing the received radiation and reference radi...