White light velocity interferometer
AssigneeThe Regents of the University of California
InventorDavid J. Erskine
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Abstract
The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s.
Claims87
A method of imprinting at least one coherent echo on a beam, comprising:
- directing a beam onto a mirror;
- creating an apparent mirror by imaging said mirror, wherein the imaged surface of said mirror defines the location of said apparent mirror, wherein the imaged center of curvature of said mirror defines the center of curvature of said apparent mirror;
- providing a second mirror having about the same curvature as said apparent mirror;
- and
- superimposing the location of said second mirror with the location of said apparent mirror.
A method of imprinting an infinite series of diminishing amplitude coherent echoes on a beam, comprising:
- directing a beam of light onto a mirror;
- creating an apparent mirror by imaging said mirror, which may be partially transmitting;
- providing a second mirror having about the same curvature and curvature polarity as said apparent mirror, wherein said second mirror may be partially transparent;
- superimposing said second mirror with said apparent mirror so that a recirculating path is created having a magnification of positive unity for a roundtrip along the optic axis, wherein said roundtrip is from said first mirror to said second mirror then back to said first mirror;
- introducing said beam to said recirculating path by partial transmission through a partially reflecting surface;
- and
- extracting a portion of said beam from said recirculating path through a partially transmitting surface, wherein the roundtrip travel time along said recirculating path determines an interferometer delay time, wherein said portion comprises an infinite series of diminishing amplitude coherent echoes.
A method of coherently delaying a beam, comprising;
- directing a beam of light onto a mirror;
- creating an apparent mirror by imaging said mirror, wherein the imaged surface of said mirror defines the location of said apparent mirror, wherein the imaged center of curvature of said mirror defines the center of curvature of said apparent mirror;
- and
- reflecting said beam off said apparent mirror, wherein said beam is delayed by the interval of round trip travel between said apparent mirror and said mirror and back to said apparent mirror, wherein said beam can be any wave kind which travels in 2 or 3 dimensions.
The method of claim Wherein the wavelength dependence of said effective reflective surface depth compensates for chromatic dispersion of other elements forming said apparent mirror so that the net chromatic aberrations of said apparent mirror is reduced.
An apparatus for imprinting at least one coherent echo on a beam, comprising:
- directing a beam onto a mirror;
- means for creating an apparent mirror by imaging said mirror, wherein the imaged surface of said mirror defines the location of said apparent mirror, wherein the imaged center of curvature of said mirror defines the center of curvature of said apparent mirror;
- providing a second mirror having about the same curvature as said apparent mirror;
- and
- superimposing the location of said second mirror with the location of said apparent mirror.
The apparatus of 43, wherein said apparent mirror is formed with achromatic optics.
The apparatus of 43, wherein said apparent mirror is formed with a plurality of optical elements, wherein at least one optical element of said plurality of optical elements comprises a distributed mirror whose effective reflective surface depth is a function of wavelength.
The apparatus of 56, wherein the wavelength dependence of said effective reflective surface depth compensates for chromatic dispersion of said plurality of optical elements forming said apparent mirror so that the net chromatic aberrations of said apparent mirror are reduced.
An apparatus for imprinting an infinite series of diminishing amplitude coherent echoes on a beam, comprising:
- directing a beam onto a mirror;
- means for creating an apparent mirror by imaging said mirror, which may be partially transmitting;
- a second mirror having the same curvature and curvature polarity as said apparent mirror, wherein said second mirror may be partially transparent, wherein said second mirror is superimposed with said apparent mirror so that a recirculating path is created having a magnification of positive unity for a roundtrip along the optic axis, wherein said roundtrip is from said first mirror to said second mirror then back to said first said mirror;
- a partially reflecting/transmitting surface through which said beam can be introduced into said recirculating path;
- a partially reflecting/transmitting surface through which a portion of said beam from said recirculating path can be extracted, wherein an interferometer delay time is determined by the roundtrip travel time along said recirculating path.
An apparatus for coherently delaying a beam, comprising;
- a mirror;
- means for directing a beam onto said mirror;
- and
- means for creating an apparent mirror by imaging said mirror, wherein the imaged surface of said mirror defines the location of said apparent mirror, wherein the imaged center of curvature of said mirror defines the center of curvature of said apparent mirror, wherein said beam is reflected off said apparent mirror, wherein the beam is delayed by the interval of round trip travel between said apparent mirror and said mirror and back to said apparent mirror, wherein the beam can be any wave kind which travels in 2 or 3 dimensions.
The apparatus of 68, wherein said apparent mirror is formed with achromatic optics.
The apparatus of 68, wherein said apparent mirror is formed with a plurality of optical elements, wherein at least one optical element of said plurality of optical elements comprises a distributed mirror whose effective reflective surface depth is a function of wavelength.
The apparatus of 82, wherein the wavelength dependence of said effective reflective surface depth compensates for chromatic dispersion of said plurality of optical elements so that the net chromatic aberrations of said apparent mirror is reduced.
Dependencies are inferred from the claim text.