Optical flow monitor
First Claim
1. A device for measuring flow of a fluid comprising:
- A) a laser and laser optics configured to direct laser beams produced by said laser through a flowing fluid to produce a flow perturbed laser beam, B) an interference producing means for producing interference patterns in said flow perturbed laser beam, C) two optical detectors defining a first detector configured to monitor at least one interference fringe defining a first interference fringe and a second detector configured to monitor at least one interference fringe other than said first interference fringe, D) a correlation means for correlating data from said first and second detectors to determine flow rate of said fluid.
1 Assignment
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Accused Products
Abstract
An optical flow monitor. Fluid flow is determined by correlating two interference signals produced by coherent laser beams passing through a flowing fluid at two spaced-apart paths. The distance between the two paths is known and the correlation of the two signals is used to determine the time required for the fluid to flow between the two paths. In a preferred embodiment actually built and tested by Applicant the correlation is made by having an operator monitor on an oscilloscope the intensities of interference fringes corresponding to each of the two beam paths. Intensity variations in the interference fringes are caused by the same turbulent eddies passing each of the two paths. These turbulent eddies cause fluctuations in the index of refraction of the fluid which produce similar patterns on the oscilloscope which are separated on the oscilloscope time scale by an amount corresponding to the distance between the two beam paths and the flow rate of the fluid. The operator can determine the time difference between the similar patterns in the two beams and knowing the actual distance between the beams the operator can calculate the flow rate. In preferred embodiments the interference signals are produced using shear plates. In one preferred embodiment useful for monitoring the flow rate of a respirator, the correlation of the fringe intensity values corresponding to the two beam paths is made by a digital computer programmed with an algorithm for making cross correlation analyses that utilizes a fast Fourier transform.
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Citations
13 Claims
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1. A device for measuring flow of a fluid comprising:
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A) a laser and laser optics configured to direct laser beams produced by said laser through a flowing fluid to produce a flow perturbed laser beam, B) an interference producing means for producing interference patterns in said flow perturbed laser beam, C) two optical detectors defining a first detector configured to monitor at least one interference fringe defining a first interference fringe and a second detector configured to monitor at least one interference fringe other than said first interference fringe, D) a correlation means for correlating data from said first and second detectors to determine flow rate of said fluid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of monitoring flow of a fluid comprising the following steps:
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A) producing optical perturbations in said flow at a first location, B) transmitting a laser beam through said flow downstream of said first location to produce a perturbed laser beam, C) measuring perturbations in at least two separate portions of said perturbed laser with at least two detectors, and D) comparing information from said at least two detectors to determine said flow.
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Specification