US4468136A — Optical beam deflection thermal imaging

Claim 1

Independent Claim 142 words

An apparatus for the nondestructive testing of material, comprising: a narrow beam excitation means for generating a spatially localized area on the sample surface having a radial surface temperature gradient; a narrow optical probe beam directed through at least one of a plurality of positions, each position having a different transverse offset value (Δ) measured from the point of intersection with said narrow beam excitation means, and passing through a thermal lens produced adjacent to said sample by said radial surface temperature gradient; and, an optical detecting means for measuring the transverse deflection (ψ t ) of said narrow optical probe beam for said at least one of a plurality of transverse offset valves (Δ) thereby providing information as to the shape of said thermal lens which in turn indicates properties and features at the surface and subsurface layers of said sample.

Claim 2

Independent Claim 142 words

An apparatus for the nondestructive testing of material, comprising: a narrow beam excitation means for generating a spatially localized area on the sample surface having a radial surface temperature gradient; a narrow optical probe beam directed through at least one of a plurality of positions, each position having a different transverse offset value (Δ) measured from the point of intersection with said narrow beam excitation means, and passing through a thermal lens produced adjacent to said sample by said radial surface temperature gradient; and, an optical detecting means for measuring the transverse deflection (ψ t ) of said narrow optical probe beam for said at least one of a plurality of transverse offset valves (Δ) thereby providing information as to the shape of said thermal lens which in turn indicates properties and features at the surface and subsurface layers of said sample.

Claim 3

Dependent Claim 78 words

The apparatus of claim 1 wherein said excitation beam means is modulated to produce a dynamic temperature change on said sample surface causing said thermal lens generated from said radial surface temperature gradient to alternate in size, and wherein said optical detecting means measures the amplitude and phase of the normal and transverse components of said optical probe beam deflection vector as function of time for said at least one of a plurality of transverse offset values (Δ).

Claim 4

Dependent Claim 31 words

The apparatus of claim 2 wherein said optical detecting means measures normal and transverse components of said optical probe beam deflection vector at a particular modulation phase of said excitation beam.

Claim 5

Dependent Claim 41 words

The apparatus of claim 2 or 3 wherein the frequence of said excitation beam means modulation (f m ) is decreased to increase the thermal diffusion length into said sample and therefore to increase the depth of analysis into said sample.

Claim 6

Dependent Claim 40 words

The apparatus of claim 2 or 3 wherein the frequency of said excitation beam means modulation (f m ) is increased to decrease the thermal diffusion length into said sample and therefore decrease the depth of analysis into said sample.

Claim 7

Dependent Claim 26 words

The apparatus of claim 2 or 3 wherein the frequency of said excitation beam means modulation (f m ) varies from 1 Hz to 1 KHz.

Claim 8

Dependent Claim 15 words

The apparatus of claim 2 or 3 wherein said excitation beam means is amplitude modulated.

Claim 9

Dependent Claim 18 words

The apparatus of claim 2 or 3 wherein said excitation beam means is modulated in a pulsing manner.

Claim 10

Dependent Claim 19 words

The apparatus of claim 2 or 3 wherein said excitation beam means is modulated by spatially varying its position.

Claim 11

Dependent Claim 18 words

The apparatus of claim 1, 2 or 3 wherein said optical detecting means is a knife edge detector.

Claim 12

Dependent Claim 69 words

The apparatus of claim 1, 2 or 3 wherein said optical detecting means is an array of detectors comprising: an array of resolution elements, each of said resolution elements being separated by a blank zone and each being small in size compared to said optical probe beam; and, detection circuitry for processing signals from each of said resolution elements to determine the vectorial displacement of said optical probe beam.

Claim 13

Dependent Claim 28 words

The apparatus of claim 1, 2 or 3 wherein said optical probe beam skims said sample surface at a normal offset distance (Z o ) from said surface.

Claim 14

Dependent Claim 38 words

The apparatus at claim 12 wherein said optical probe beam scans in a transverse manner across said thermal lens and wherein said optical detecting means measures said optical probe beam vectorial deflection for discrete transverse displacement (Δ) values.

Claim 15

Dependent Claim 71 words

The apparatus of claim 13 wherein said excitation beam means is pointed to a plurality of positions (X o , Y o ) on said sample surface and wherein said optical probe beams transversely scans said thermal lens generated from each of said excitation beam means positions, and wherein said optical detecting means measures said optical probe beam vectorial deflection for each (X o , Y o , Δ) input parameters.

Claim 16

Dependent Claim 71 words

The apparatus of claim 12 wherein said optical probe beam is held stationary and said excitation beam means is pointed to a plurality of (X o , Y o ) positions on said sample surface generating said thermal lens which is intersected by said stationary optical probe beam, and wherein said optical detecting means measures said optical beam vectorial deflection for each (X o , Y o , Δ) input parameter.

Claim 17

Dependent Claim 39 words

The apparatus of claim 12 wherein said optical probe beam intersects said excitation beam means, said transverse offset value (Δ) equaling zero, and wherein said optical detecting means measures the transverse deflection (ψ t ) of said probe beam.

Claim 18

Dependent Claim 57 words

The apparatus of claim 16 wherein said excitation beam means is pointed to a plurality of positions (X o , Y o ) on said sample surface and wherein said optical detecting means measures said transverse deflection (ψ t ) of said optical probe beam for each excitation beam means position (X o , Y o ).

Claim 19

Dependent Claim 65 words

The apparatus of claim 1, 2 or 3 wherein said optical probe beam enters said thermal lens at an incident angle (θ,φ) and is reflected from a location (X 1 , Y 1 ) on said sample surface, back out through said thermal lens, and wherein said optical detecting means measures said optical probe beam vectorial deflection for (θ,φ, X 1 Y 1 ) parameters.

Claim 20

Dependent Claim 51 words

The apparatus of claim 18 wherein said optical probe beam scans said thermal lens producing a plurality of different (θ,φ, X 1 , Y 1 ) parameters and wherein said optical detecting means measures said optical probe beam vectorial deflection for each (θ,φ, X 1 , Y 1 ) input parameter.

Claim 21

Dependent Claim 73 words

The apparatus of claim 19 wherein said excitation beam means is pointed to a plurality of positions (X o , Y o ) on said sample surface, said optical probe beam scanning said thermal lens produced by each of said excitation beam positions, and wherein said optical detecting means measures said optical probe beam vectorial deflection for each (θ,φ, X 1 , Y 1 , X o , Y o ) input parameter.

Claim 22

Dependent Claim 46 words

The apparatus of claim 1, 2 or 3 wherein said optical detecting means is a silicon wafer position detector having output voltage dependent on the location said optical probe beam strikes said wafer surface and wherein the time varying amplitude of the output voltage is recorded.

Claim 23

Dependent Claim 93 words

The apparatus of claim 21 wherein said silicon wafer position detector further comprises: an amplifier connected to said silicon waver position detector; an excitation beam modulator for modulating said excitation beam means; an oscillator which provides a reference signal to control an excitation beam modulator; a lock-in amplifier connected to said amplifier, synchronized by reference signals from said oscillator, to detect the deflection signal generated by said silicon wafer position detector at a particular phase of the excitation beam modulation cycle; and, a recorder connected to said lock-in amplifier for recording deflection amplitude.

Claim 24

Dependent Claim 28 words

The apparatus of claim 21 wherein said silicon wafer position detector will record said amplitude of output voltage at the same modulation phase of said excitation beam means.

Claim 25

Dependent Claim 82 words

The apparatus of claim 2 in which said optical detecting means includes a detector array, and in which said apparatus further comprises a beam splitter to split said optical probe beam into a reference beam and a signal beam, said reference beam being directed to said detector array, said signal beam being directed through said thermal lens to said detector array such that an interference pattern between said reference beam and said signal beam is produced and detected by said detector array.

Claim 26

Dependent Claim 18 words

The apparatus of claim 1 wherein said thermal lens is generated in a fluid which is a gas.

Claim 27

Dependent Claim 12 words

The apparatus of claim 25 wherein said gas is at atmospheric pressure.

Claim 28

Dependent Claim 13 words

The apparatus of claim 25 wherein said gas is at below atmospheric pressure.

Claim 29

Dependent Claim 17 words

The apparatus of claim 1 wherein said excitation beam means is projected normal to said sample surface.

Claim 30

Dependent Claim 20 words

The apparatus of claim 1 wherein said excitation beam means is projected at an angle relative to said sample surface.

Claim 31

Dependent Claim 26 words

The apparatus of claim 1 wherein said excitation beam means is produced by a laser source producing a circular beam of light having a gaussian distribution.

Claim 32

Dependent Claim 13 words

The apparatus of claim 1 wherein said optical probe beam is coherent light.

Claim 33

Dependent Claim 13 words

The apparatus of claim 1 wherein said optical probe beam is incoherent light.

Claim 34

Dependent Claim 19 words

The apparatus of claim 1 wherein said optical probe beam is small in diameter compared to said thermal lens.

Claim 35

Dependent Claim 29 words

The apparatus of claim 1 wherein said excitation beam means is electromagnetic energy varying from the microwave frequency (10 9 Hz) to the ultraviolet light frequency (10 15 Hz).

Claim 36

Dependent Claim 14 words

The apparatus of claim 1 wherein said excitation beam means is a particle beam.

Claim 37

Dependent Claim 15 words

The apparatus of claim 1 wherein said optical probe beam is 1 mm in diameter.

Claim 38

Dependent Claim 18 words

The apparatus of claim 1 wherein said thermal lens is generated in a fluid which is a liquid.

Claim 39

Independent Claim 147 words

A method of thermal imaging comprising the steps of: applying energy to a sample to produce a spatially localized area on the sample surface having a radial surface temperature gradient, said radial surface temperature gradient produces in a fluid adjacent to said sample surface, a localized volume having an alternating refractive index; directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (Δ) measured from the point of intersection with said narrow beam excitation means and passing through said volume of alternating refractive index which causes said optical probe bean to be deflected; and, measuring the transverse deflection (ψ t ) of said optical probe beam for said at least one of a plurality of transverse offset values (Δ) to provide information on properties and features at the surface and subsurface layers of said sample.

Claim 40

Independent Claim 147 words

A method of thermal imaging comprising the steps of: applying energy to a sample to produce a spatially localized area on the sample surface having a radial surface temperature gradient, said radial surface temperature gradient produces in a fluid adjacent to said sample surface, a localized volume having an alternating refractive index; directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (Δ) measured from the point of intersection with said narrow beam excitation means and passing through said volume of alternating refractive index which causes said optical probe bean to be deflected; and, measuring the transverse deflection (ψ t ) of said optical probe beam for said at least one of a plurality of transverse offset values (Δ) to provide information on properties and features at the surface and subsurface layers of said sample.

Claim 41

Independent Claim 121 words

A method of thermal imaging to detect localized thermal hot spots on a sample surface, comprising the steps of: directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (Δ) measured from the center point of said hot spot and passing through a thermal lens produced by a radial surface temperature gradient in a fluid adjacent to said localized thermal hot spot; and, measuring the transverse deflection (ψ t ) of said optical probe beam caused by said thermal lens for said at least one of a plurality of transverse offset values (Δ) to provide information on properties and features at the surface and subsurface layers of said sample.

Claim 42

Independent Claim 121 words

A method of thermal imaging to detect localized thermal hot spots on a sample surface, comprising the steps of: directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (Δ) measured from the center point of said hot spot and passing through a thermal lens produced by a radial surface temperature gradient in a fluid adjacent to said localized thermal hot spot; and, measuring the transverse deflection (ψ t ) of said optical probe beam caused by said thermal lens for said at least one of a plurality of transverse offset values (Δ) to provide information on properties and features at the surface and subsurface layers of said sample.

Claim 43

Independent Claim 129 words

A method of thermal imaging comprising the steps of: directing an excitation beam to the surface of a sample for generating a spatially localized area on the sample surface having a radial surface temperature gradient; directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (Δ) measured from the point of intersection with said narrow beam excitation means, and passing through a thermal lens produced adjacent to said sample by said radial surface temperature gradient; and, measuring the transvere deflection (ψ t ) of said optical probe beam for said at least one of a plurality of transverse offset values (Δ) to provide information on properties and features at the surface and subsurface layers of said sample.

Claim 44

Independent Claim 129 words

A method of thermal imaging comprising the steps of: directing an excitation beam to the surface of a sample for generating a spatially localized area on the sample surface having a radial surface temperature gradient; directing an optical probe beam through at least one of a plurality of positions, each position having a different transverse offset value (Δ) measured from the point of intersection with said narrow beam excitation means, and passing through a thermal lens produced adjacent to said sample by said radial surface temperature gradient; and, measuring the transvere deflection (ψ t ) of said optical probe beam for said at least one of a plurality of transverse offset values (Δ) to provide information on properties and features at the surface and subsurface layers of said sample.

Claim 45

Dependent Claim 41 words

The method of claim 40 wherein said excitation beam is modulated and the normal and transverse deflection components of said optical probe beam are measured as well as the phase difference between said excitation beam and said optical probe beam's deflection.

Claim 46

Dependent Claim 27 words

The method of claim 41 wherein said optical probe beam is directed to skim the sample surface at an offset distance (Z o ) above the surface.

Claim 47

Dependent Claim 41 words

The method of claim 42 including the steps of: scanning the optical probe beam in a transverse manner across said thermal lens; and measuring the transverse deflection (ψ t ) of said optical probe beam for discrete transverse offset values (Δ).

Claim 48

Dependent Claim 36 words

The method of claim 43 including the steps of: directing the excitation beam to a plurality of positions on said sample surface; scanning each of said thermal lens generated by each of said excitation beam positions.

Claim 49

Dependent Claim 37 words

The method of claim 44 wherein the optical probe beam is directed to intersect the excitation beam, said transverse offset value (Δ) equaling zero; and wherein the transverse deflection (ψ t ) optical probe beam is measured.

Claim 50

Dependent Claim 42 words

The method of claim 40 wherein said optical probe beam is directed to enter said thermal lens at an incident angle and is reflected from a location on the sample surface; and, measuring the vectorial deflection of the reflected optical probe beam.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1987-08-28	1988-02-27	1988-08-28	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1991-08-28	1992-02-27	1992-08-28	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1995-08-28	1996-02-27	1996-08-28	$7700.00	Window Closed / Lapsed

Optical beam deflection thermal imaging

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