Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Patent
1982-07-08
1984-09-11
Frankfort, Charles
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
374123, G01J 500
Patent
active
044707100
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to an I.R. two wavelength radiation pyrometer and relates particularly but not exclusively to an I.R. radiation pyrometer which has a fast response time and a wide dynamic range. A particular embodiment of the invention has application in the measurement of the rapid temperature rises caused by the irradiation of a surface with a laser beam.
DESCRIPTION OF PRIOR ART
Hitherto in the art of the measurement of surface temperatures of bodies irradiated by lasers or by other energy sources such as electron beams, it has been a problem to provide an instrument which has a sufficiently fast response time to follow the temperature changes, as well as a sufficiently wide dynamic range to cover the temperatures envisaged--from in the order of 600.degree. K. to 3000.degree. K. in a time period of 100 ms. It is also a problem to measure this temperature rise over a small area, as for example in the order of 1 millimeter.
STATEMENT OF THE INVENTION
An embodiment of the present invention will operate to cover the aforementioned temperature ranges and in the required time period and will also detect this change over an area of approximately 1 mm.
The aforementioned characteristics of a desired pyrometer have been achieved by an embodiment which obtains a ratio between signals derived from the radiated I.R. from the body at two slightly different wavelengths.
One of the signal values is maintained approximately constant and the other signal value is influenced by substantially the same value of the control for maintaining the said one signal value approximately constant. The two signals values are then fed to a ratio providing means where preferably one of the signals values is divided into the other signal value whereby to obtain a signal value representative of the temperature.
The required area of view can be controlled by known optical means.
Therefore, according to a preferred aspect of the present invention, there is provided a pyrometer which uses an I.R. radiation two wavelength measurement technique, said pyrometer having means for measuring the I.R. radiated from a surface of a body at two I.R. wavelengths and for providing respective signal values derived therefrom, electronic circuit means for maintaining the value of one of the signals approximately constant by a feedback control which monitors one of said signals to ascertain a required feedback control, said circuit means also influencing the value of the other signal by substantially the same feedback control and a means for determining a ratio between the two signals whereby to represent the temperature of the surface of the body.
It is particularly preferred that the means for measuring I.R. radiated from the surface of a body at the two wavelengths be a single detector.
Most preferably, the I.R. radiated from the surface of the body is directed onto a chopper wheel which comprises a series of optical filters which successively are for one wavelength of the I.R. radiated and for the other wavelength of I.R. radiated, and wherein a signal circuit is activated as each of the respective filters on the chopper wheel is placed in the path of the I.R. beam, whereby to activate circuitry to pass the I.R. signals from one wavelength to one filter circuit and the I.R. signals of the other wavelength to another filter circuit, prior to being further processed by said ratio determining means.
A chopper wheel is also included within the scope of the invention, and in its broadest aspect it may comprise a chopper wheel body with a plurality of circumferentially extending filters therein, said filters alternating sequentially for one wavelength of I.R. and for another wavelength of I.R., said filters being formed by a vacuum deposition.
BRIEF DESCRIPTION OF DRAWINGS
In order that the invention may be more clearly understood, several embodiments will now be described with reference to the accompanying drawings wherein:
FIG. 1 is a basic schematic diagram of the preferred pyrometer.
FIG. 2 is a view of the fac
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patent: 3715922 (1973-02-01), Menge
patent: 3806249 (1974-04-01), Lesinski
patent: 4342912 (1982-08-01), Adamson
Beckwith Peter J.
Crane Kenneth
Commonwealth of Australia
Frankfort Charles
Schuster David R.
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