Granted Patent B2

US 9,791,419 · App. 14/623,181 · Granted Oct 17, 2017

Abstract

Claims (39)

1. A measuring device for non-mechanical-contact measurement of a layer, the measuring device comprising:

a light source operative to generate a pulse adapted to interact with the layer so as to generate a thermal wave in a gas medium present adjacent the layer, said thermal wave causing an acoustic signal to be generated; and

a detector adapted to detect a first signal responsive to the acoustic signal, said detector not being in mechanical contact with the layer, wherein said first signal is representative of the measured layer;

wherein the pulse is associated with an absorption of the pulse within the layer, the absorption being substantially greater than an absorption of the pulse within a substrate in mechanical contact with the layer, wherein the layer is disposed between the substrate and the gas medium.

2. The measuring device of claim 1 , wherein the pulse is adapted to interact with the layer without permanently altering the layer.

3. The measuring device of claim 1 , wherein a wavelength of the pulse is associated with a penetration depth of the pulse in the layer, the penetration depth being greater than a thickness of the layer.

4. The measuring device of claim 1 , wherein a temporal width of the pulse is associated with a thermal diffusion length of the layer, the thermal diffusion length being substantially equal to a thickness of the layer.

5. The measuring device of claim 1 , wherein the detector comprises:

a transducer adapted to have a frequency response greater than a frequency range of a noise ambient in the vicinity of the detector and to generate the first signal.

6. The measuring device of claim 1 , wherein the detector comprises:

a sound coupler adapted to direct a portion of the acoustic signal to the detector.

7. The measuring device of claim 1 , wherein the light source is further operative to generate a plurality of pulses each having different associated characteristics selected to interact with a plurality of different associated constituents of the layer, said measuring device including a plurality of different detectors each associated with a different one of the plurality of pulses.

8. The measuring device of claim 1 further comprising a signal processor adapted to:

improve a signal to noise ratio of the first signal to form a second signal;

calculate a distance between the detector and a region of the gas medium generating the thermal wave;

compensate the second signal in accordance with the distance to produce a third signal that is substantially independent of a fluctuation of the distance; and

determine a measurement responsive to a composition and thickness of the film in accordance with an amplitude of the third signal and a predetermined look-up table.

9. The measuring device of claim 8 , wherein the signal processor is further adapted to calculate the distance in accordance with a speed of the acoustic signal in the gas medium multiplied by a time of flight of the acoustic signal.

10. A method for non-mechanical-contact measurement of a layer, the method comprising:

generating a pulse adapted to interact with the layer to generate a thermal wave in a gas medium present adjacent the layer, thereby causing an acoustic signal to be generated; and

detecting a first signal responsive to the acoustic signal without mechanically contacting the layer, wherein said first signal is representative of the measured layer;

wherein the pulse is associated with an absorption of the pulse within the layer, the absorption being substantially greater than an absorption of the pulse within a substrate in mechanical contact with the layer, wherein the layer is disposed between the substrate and the gas medium.

11. The method of claim 10 , wherein the pulse interacts with the layer without permanently altering the layer.

12. The measuring device of claim 10 , wherein a wavelength of the pulse is associated with a penetration depth of the pulse in the layer, the penetration depth being greater than a thickness of the layer.

13. The measuring device of claim 10 , wherein a temporal width of the pulse is associated with a thermal diffusion length of the layer, the thermal diffusion length being substantially equal to a thickness of the layer.

14. The method of claim 10 further comprising:

generating the first signal using a transducer having a frequency response greater than a frequency range of a noise ambient in the vicinity of the detector.

15. The method of claim 10 further comprising:

directing a portion of the acoustic signal to a detector.

16. The method of claim 10 further comprising:

generating a plurality of pulses each having different associated characteristics selected to interact with a plurality of different associated constituents of the layer; and

using a plurality of different detectors each associated with a different one of the plurality of pulses.

17. The method of claim 10 further comprising:

improving a signal to noise ratio of the first signal to form a second signal;

calculating a distance between a detector and a region of the gas medium generating the thermal wave;

compensating the second signal in accordance with the distance to produce a third signal that is substantially independent of a fluctuation of the distance; and

determining a measurement responsive to a composition and thickness of the film in accordance with an amplitude of the third signal and a predetermined look-up table.

18. The method of claim 17 further comprising:

calculating the distance in accordance with a speed of the acoustic signal in the gas medium multiplied by a time of flight of the acoustic signal.

Assignments (10)