Abstract: Method and apparatus for measuring fluid motion with micron scale spatial resolution, in which fluorescent particles are injected into a fluid body in a test device, the test device is broadly illuminated with pulses of light at the excitation frequency of the fluorescent particles, the fluorescent light is collected by a microscope objective lens, and the light thus collected is relayed through a fluorescent filter to an image recording device, the depth of field of the objective lens defining the thickness of a two-dimensional measurement plane.

Abstract: A method and apparatus for measuring fluid motion with micron scale spatial resolution has been developed. Here, micron or submicron solid fluorescent particles are injected into the fluid body. The particles are chosen to closely follow the motion of the fluid. Pulses of light, at the excitation wavelength, broadly illuminate the test device and the fluorescent particles, The flourescent particles absorb the excitation light and emit pulses of fluorescent light, at the emission wavelength. The fluorescent light is collected by a microscope objective lens, and relayed through a fluorescent filter to an image recording device, such as a CCD camera. Subsequently, discrete images of discrete particles at two or more instances in time are recorded. These images can then be analyzed using correlation analysis to obtain velocity measurements.

Abstract: A holographic particle image velocimeter employs stereoscopic recording of particle images, taken from two different perspectives and at two distinct points in time for each perspective, on a single holographic film plate. The different perspectives are provided by two optical assemblies, each including a collecting lens, a prism and a focusing lens. Collimated laser energy is pulsed through a fluid stream, with elements carried in the stream scattering light, some of which is collected by each collecting lens. The respective focusing lenses are configured to form images of the scattered light near the holographic plate. The particle images stored on the plate are reconstructed using the same optical assemblies employed in recording, by transferring the film plate and optical assemblies as a single integral unit to a reconstruction site.

Abstract: A system of double-pulse particle velocimetry, according to which small scattering particles are illuminated by two short pulses of laser light and then images are recorded photographically to produce a record from which the particle velocity can be determined by measuring the displacement of the particle images. Particle images is understood to mean both the non-overlapping individual particles and overlapping, coherently interfering images commonly referred to as "speckle". In order to resolve the directional ambiguity inherent in the system, artificial shifting is effected in the image field between exposures by an amount that is greater than any negative displacement occurring in the field, such shifting being performed here by means of an electro-optical device in place of the shifting previously produced by rotating mirrors and the like.

Abstract: The present invention is in the context of the measurement of velocity fields of fluid flows containing many small scattering sites, which exist either in the form of particles or optically activated, discrete fluid volumes. The invention is directed to a method and apparatus for resolving ambiguity with respect to the direction of displacement of particle images recorded by multiple exposures on film or videographic media. The invention enables the elimination of directional ambiguity by means of shifting the image field between exposures by an amount that is greater than any negative displacement occurring in the image field. In this way, all recorded displacements are positive, and negative displacements are obtained from the measurements by mathematically subtracting the artificial shift after the measurements.

Abstract: A hybrid optical/digital method for measuring the displacements of compact images, in particular, particle images recorded on photographic or other recording media in multiple exposure photography. The method compresses the two-dimensional image field of the particles into two one-dimensional line images that are perpendicular to each other. The mean particle displacement between multiple exposures is determined by digitizing the one dimensional images, computing their autocorrelations, and locating the peaks of those autocorrelations. This method is particularly adapted to measure the velocity fields in fluids containing many small particles. Alternatively, when the first and second images of a single particle are the only images in the image field, the displacement is found by locating the peak of each image.

Abstract: A method and apparatus for measuring the velocity of moving particles such as red blood cells in a tissue sample is disclosed, characterized by digital processing techniques and autocorrelation. The moving particles are illuminated to produce a spread spectrum optical signal resulting from the Doppler shift occurring when photons are scattered by the moving particles. A spread spectrum electrical signal corresponding with the optical signal and containing spectral and noise components is generated from the optical signal. The electrical signal is filtered to produce the bandpass and DC signals which are subsequently converted to digital form. A first autocorrelation function is calculated from the bandpass signal and a noise autocorrelation function is determined in accordance with the DC signal level. The first and noise autocorrelation functions are compared to produce an autocorrelation function free of a noise component.

Abstract: A particle size measuring apparatus and method has a laser unit and optics that provide a central focused light area surrounded by an annular focused light area. Particles moving with fluid through the center of central focus light area cause the light to scatter. The scattered light is sensed and converted to readable signals indicative of particle size.