Measurement of small movements
First Claim
1. A method of measuring the out of plane movement of an oscillating irregular surface, comprising the steps of:
- illuminating the surface with coherent light, the reflexions and scattering of the coherent light from the surface forming a speckle pattern,detecting with a spatially integrating photodetector, variations caused by the out-of-plane movement in the speckle pattern and generating a photodetector signal indicative thereof andcontinuously detecting, from the photodetector signal, amplitude variations thereof at the frequency of the out-of-plane movement to represent such movement.
1 Assignment
0 Petitions
Accused Products
Abstract
Measurement of small oscillatory movements of an irregular surface involves the production of a speckle pattern therefrom by coherent light illumination, and the arrangement of a photodetector for direct response to such pattern, variations in photodetector output component at the frequency of the surface movement representing that movement. Another, stationary, illuminated irregular surface can be involved to produce a speckle interference pattern for response of the photodectector thereto and, in the case where the two surfaces are closely adjacent, a single beam can be used to illuminate the first and other surfaces predominantly and by stray light, respectively. This common beam illumination can be used in prior speckle interferometry. The first surface can be an eardrum oscillated by a sound wave, suitably of swept frequency or impulse form, with detection of the photodetector variations respectively being in synchronous manner or by Fourier analysis, respectively.
104 Citations
14 Claims
-
1. A method of measuring the out of plane movement of an oscillating irregular surface, comprising the steps of:
-
illuminating the surface with coherent light, the reflexions and scattering of the coherent light from the surface forming a speckle pattern, detecting with a spatially integrating photodetector, variations caused by the out-of-plane movement in the speckle pattern and generating a photodetector signal indicative thereof and continuously detecting, from the photodetector signal, amplitude variations thereof at the frequency of the out-of-plane movement to represent such movement. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. A method of measuring the movement of an oscillating surface, comprising the steps of:
-
illuminating the oscillating surface with a beam of coherent light, illuminating a second, stationary, irregular surface, by stray coherent light from both of said beam directed predominantly at said oscillating surface, the scattering and reflexions of coherent light from said surfaces forming a speckle interference pattern, and detecting using a photodetector variations in the speckle interference pattern.
-
-
8. Apparatus for measuring the movement of an oscillating irregular surface comprising:
-
a coherent light source for illuminating the oscillating surface, and means for detecting variations caused by said movement in a speckle pattern produced by scattering and reflexions of light from said surface, said detecting means including a spatially integrating photodetector arranged for direct response to said pattern, and a detector continuously responsive to amplitude variations in an output signal of said photodetector at the frequency of said movement. - View Dependent Claims (9, 10, 11, 12, 13, 14)
-
Specification