Internal temperature monitor for work pieces
First Claim
1. A method of measuring the internal temperature of a work piece in a furnace, the workpiece having a first surface, an opposite second surface and a predetermined thickness between the first and second surfaces, comprising the steps of:
- generating an excitation light pulse with a laser at a spaced location from the work piece;
conveying the laser light pulse with an optical fiber extending in a cooled probe in the furnace up to a vicinity of the first surface of the work piece;
striking the first surface with the pulse of excitation laser light to generate a first displacement at the first surface and form an ultrasonic pulse in the work piece which propagates to the second surface, the ultrasonic pulse being reflected at the second surface and returning to the first surface to produce a second displacement at the first surface;
measuring the time between the first and second displacements which is proportional to a time-of-flight of the ultrasonic pulse in the work piece; and
calculating the internal temperature of the work piece as a function of the predetermined work piece thickness and the time-of-flight.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and apparatus for measuring the internal temperature of a work piece comprises an excitation laser for generating laser pulses which are directed through a water cooled probe, and in an optical fiber, to a first surface of the work piece. The laser is of sufficient intensity to ablate the surface of the work piece, producing a displacement and a resulting ultrasonic pulse which propagates within the thickness of the work piece to an opposite surface. The ultrasonic pulse is reflected from the opposite surface and returns to the first surface to create a second displacement. A second continuous laser also shines its light through an optical fiber in the probe into the first surface and is used in conjunction with signal processing equipment to measure the time between the first and second displacements. This time is proportional to the time-of-flight of the ultrasonic pulse in the work piece which, with a known or detected thickness of the work piece, can be used to calculate the internal temperature of the work piece.
21 Citations
12 Claims
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1. A method of measuring the internal temperature of a work piece in a furnace, the workpiece having a first surface, an opposite second surface and a predetermined thickness between the first and second surfaces, comprising the steps of:
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generating an excitation light pulse with a laser at a spaced location from the work piece; conveying the laser light pulse with an optical fiber extending in a cooled probe in the furnace up to a vicinity of the first surface of the work piece; striking the first surface with the pulse of excitation laser light to generate a first displacement at the first surface and form an ultrasonic pulse in the work piece which propagates to the second surface, the ultrasonic pulse being reflected at the second surface and returning to the first surface to produce a second displacement at the first surface; measuring the time between the first and second displacements which is proportional to a time-of-flight of the ultrasonic pulse in the work piece; and calculating the internal temperature of the work piece as a function of the predetermined work piece thickness and the time-of-flight. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for measuring the internal temperature of a work piece in a furnace, the work piece having a first surface, an opposite second surface and a predetermined thickness between the first and second surfaces, comprising:
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an excitation laser for generating laser pulses which are sufficiently intense to produce a displacement of a surface of the work piece; an optical fiber extending in a cooled probe in the furnace for conveying the excitation laser pulses to an immediate vicinity of the first surface, said cooled probe being positioned in the furnace near the work piece; lens means near the end of the optical fiber in the cooled probe in the vicinity of the first surface of the work piece for focusing the excitation laser pulses on the first surface to produce first displacements at the first surface, the first displacements each generating an ultrasonic pulse in the work piece which propagates to and reflects from the second surface, the ultrasonic pulses returning to the first surface to produce a second displacement at the first surface; time measuring means operatively engaged to the first surface of the work piece for measuring a time between the first and second displacements at the first surface which time is proportional to the time-of-flight of the ultrasonic pulse in a work piece; and calculation means connected to the time measuring means for calculating the internal temperature of the work piece as a function of the work piece thickness and the time of flight. - View Dependent Claims (9, 10, 11, 12)
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Specification