MULTIPOINT LASER DOPPLER VIBROMETER
2 Assignments
0 Petitions
Accused Products
Abstract
A multipoint laser Doppler vibrometer system (1) comprises a laser diode (2), beam expanding lens (3), a holographic optical element (HOE, 4) and a CMOS camera (5) receiving reflected light via optics (6). The HOE (4) is a hologram of a flat diffusely reflecting surface. Some light (8) is diffracted by the recorded hologram in the HOE (4) to provide a reference beam of light that is directed back towards the camera (5). Apart from some absorption the remaining light (9) continues onwards to illuminate the object The light that is reflected and scattered from the object (10) passes efficiently through the HOE (4) and interferes with the reference light (8) that is holographically reconstructed by the HOE (4) and subsequently detected by the camera (5). The beam from the laser diode (2) is divergent, which means that the sensitivity vector varies across the field of view. Thus the system is sensitive to both in-plane and out-of-plane motion of the object to an extent that depends on position of the object points. An alternative system (20) has two emission lenses (22, 23). The HOE (21) either redirects light already collimated by the lens combination (22, 23) or both redirects and collimates uncollimated light in such a way as to illuminate the object along the normal to its surface.
20 Citations
44 Claims
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1-23. -23. (canceled)
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24. A vibration measurement system comprising:
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a laser light source having means for generating a laser beam and for modulating its wavelength according to a laser Doppler vibrometer scheme; a camera for receiving scattered light from an object, an image processor for demodulating light detected by the camera according to the laser Doppler vibrometer scheme to determine vibration of the object; and optics to direct light from the light source to illuminate the object, and to provide a reference beam for the camera, in which a holographic optical element is used in providing the reference beam. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44)
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Specification