US 6,128,081 A · Method and system for measuring a physical parameter of at least one layer of a multilayer article without damaging the article and sensor head for use therein

Abstract

A method and system are provided to measure a physical parameter of a film such as film thickness or build, in both the wet and dry states of the film, on an article in a production environment without any contact or damage to the film or the rest of the article. The system includes two laser light sources, one pulsed and the other substantially continuous (i.e. long pulses), an interferometer, fiber optic cables, and appropriate optics including multiplexers and demultiplexers to: 1) image and transmit light from both sources to the film on the article; and 2) transmit the light from the continuous source reflected off the film surface back to the interferometer, and a computer containing a data acquisition card to record the data after signal processing and appropriate software to process the data. Light from both light sources are imaged on and over the same spot on the surface of the film. The pulsed light source is used to generate ultrasound in the film. The reflected light from the continuous source is detected by the interferometer to probe the ultrasonic vibrations of the film. The motion of the surface of the film at ultrasonic frequencies generates a Doppler shift in the frequency of the continuous light source. This modulation of the continuous light source frequency is monitored by the interferometer and is converted to a signal which is recorded and processed by the computer. Signal processing involves performing a Z-transform of the data to identify the resonance frequencies of ultrasonic motion in the film. These resonant frequencies, in conjunction with some physical properties of the material of the film are used to determine the film build of the layer.

Claims48

Dependent claims

A method for measuring a physical parameter of at least one layer of a multilayer article without damaging the article, the method comprising the steps of:

generating a first pulse of electromagnetic energy;
transmitting the first pulse to a sensing station;
generating a second pulse of electromagnetic energy;
transmitting the second pulse to the sensing station;
directing the first pulse at the sensing station toward a first spot on a surface of the article to generate an ultrasonic wave in the article which, in turn, causes ultrasonic motion of the surface of the article without damaging the article;
directing the second pulse at the sensing station toward a second spot on the surface of the article which substantially overlaps the first spot to obtain a reflected pulse of electromagnetic energy which is modulated based on the ultrasonic motion of the surface;
transmitting the reflected pulse from the sensing station;
detecting the reflected pulse after the step of transmitting the reflected pulse to obtain a corresponding ultrasonic electrical signal;
and
processing the ultrasonic electrical signal to obtain a physical parameter signal which represents the physical parameter of the at least one layer at the first and second substantially overlapping spots.

7 more elements

A system for measuring a physical parameter of at least one layer of a multilayer article without damaging the article, the system comprising:

a generation laser for generating a first pulse of electromagnetic energy;
a first optical fiber for transmitting the first pulse therethrough to a sensing station;
a detection laser for generating a second pulse of electromagnetic energy;
a second optical fiber for transmitting the second pulse therethrough to the sensing station;
a sensor head coupled to the first and second optical fibers at the sensing station and having at least one optical component for directing the first pulse transmitted through the first optical fiber toward a first spot on a surface of the article to generate an ultrasonic wave in the article which, in turn, causes ultrasonic motion of the surface of the article without damaging the article, the sensor head also having at least one optical component for directing the second pulse toward a second spot on the surface of the article which substantially overlaps the first spot to obtain a reflected pulse of electromagnetic energy which is modulated based on the ultrasonic motion of the surface, the sensor head receiving the reflected pulse;
an optical detector coupled to the sensor head for detecting the reflected pulse to obtain a corresponding ultrasonic electrical signal;
and
a signal processor for processing the ultrasonic electrical signal to obtain a physical parameter signal which represents the physical parameter of the at least one layer at the first and second overlapping spots.

5 more elements

A method for measuring a physical parameter of at least one layer over an extended area of a multilayer article without damaging the article, the method comprising the steps of:

generating a first pulse of electromagnetic energy;
directing the first pulse into a first plurality of beams;
transmitting the first plurality of beams to a plurality of separate locations at a sensing station;
generating a second pulse of electromagnetic energy;
directing the second pulse into a second plurality of beams;
transmitting the second plurality of beams to the plurality of locations at the sensing station;
directing the first plurality of beams at the locations at the sensing station toward a first plurality of spots on a surface of the article to generate ultrasonic waves in the article which, in turn, causes ultrasonic motion of the surface of the article without damaging the article;
directing the second plurality of beams at the locations at the sensing station toward a second plurality of spots on the surface the article, each of the second plurality of spots substantially overlapping one of the first plurality of spots to obtain a reflected pulse of electromagnetic energy which is modulated based on the ultrasonic motion of the surface at its respective first and second overlapping spots;
transmitting the reflected pulses from the sensing station;
collecting the transmitted reflected pulses to obtain collected pulses;
detecting the collected pulses to obtain a plurality of corresponding ultrasonic electrical signals;
and
processing the plurality of ultrasonic electrical signals to obtain a plurality of physical parameter signals which represents the physical parameter of the at least one layer over the extended area of the article.

10 more elements

A system for measuring a physical parameter of at least one layer over an extended area of a multilayer article without damaging the article, the system comprising:

a generation laser for generating a first pulse of electromagnetic energy;
a first device for directing the first pulse into a first plurality of beams;
a first plurality of optical fibers for transmitting the first plurality of beams therethrough to a corresponding plurality of locations at a sensing station;
a detection laser for generating a second pulse of electromagnetic energy;
a second device for directing the second pulse into a second plurality of beams;
a second plurality of optical fibers for transmitting the second plurality of beams therethrough to the corresponding plurality of locations at the sensing station;
a plurality of sensor heads, each of the sensor heads positioned at one of the locations at the sensing station and coupled to one of each of the first and second pluralities of optical fibers, each of the sensor heads having at least one optical component for directing one of the first plurality of beams toward one of a first plurality of spots on a surface of the article to generate an ultrasonic wave in the article which, in turn, causes ultrasonic motion of the surface of the article without damaging the article, each of the sensor heads also having at least one optical component for directing one of the second plurality of beams toward one of a second plurality of spots on the surface of the article which substantially overlaps its corresponding spot of the first plurality of spots to obtain a reflected pulse of electromagnetic energy which is modulated based on the ultrasonic motion of the surface at its respective first and second overlapping spots, each of the sensor heads also receiving its reflected pulse;
a third device coupled to each of the sensor heads for collecting the reflected pulses to obtain collected pulses;
an optical detector coupled to the third device for detecting the collected pulses to obtain a plurality of corresponding ultrasonic electrical signals;
and
a signal processor for processing the plurality of ultrasonic electrical signals to obtain physical parameter signals which represents the physical parameter of the at least one layer over the extended area on the article.

8 more elements

Dependencies are inferred from the claim text.

Method and system for measuring a physical parameter of at least one layer of a multilayer article without damaging the article and sensor head for use therein

Life of this patent

Method and system for measuring a physical parameter of at least one layer of a multilayer article without damaging the article and sensor head for use therein

Life of this patent

Abstract

Claims48