Blackbody cavity for calibration of infrared thermometers

a technology of infrared thermometers and blackbody cavities, which is applied in the field of blackbody cavities for calibration of infrared thermometers, can solve the problems of not being able to achieve uniform walls, not being able to consider painted surfaces in the same way, and being difficult to ensure uniform walls. , to achieve the effect of minimizing escape, high emissivity and low emissivity

Inactive Publication Date: 2002-02-21
ADVANCED MONITORS
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Benefits of technology

0008] A blackbody cavity is disclosed having two types of wall surfaces wherein a first type has high emissivity and a second type has low emissivity. The low emissivity wall surface has an aperture from where the infrared radiation escapes the cavity, and is preferably shaped to minim

Problems solved by technology

This is not nearly enough to consider a painted surface as a blackbody.
A challenge to a blackbody designer is to provide a cavity having uniform wall temperatures with as many internal reflections as possible.
In many instances, this is not easy to accomplish, because any increase in cavity dimensions makes it much more difficult to assure the uniform wall temperatures, which for high precision blackbo

Method used

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  • Blackbody cavity for calibration of infrared thermometers

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Embodiment Construction

[0014] Any surface is an emitter of thermal radiation. The properties of a surface are a key factor in determining how well the surface can emit such radiation. According to Kirchhoff's Law, a good emitter must be a poor reflector and vice versa:

.epsilon.+.rho.=1 (1)

[0015] where .epsilon. is emissivity and .rho. is reflectivity of an object. Both factors vary on a scale from 0 to 1, with one factor changing at the expense of the other. Thus, a mirror is very poor emitter and a black surface is a very good emitter. FIG. 1 is a generalized or schematic representation of a two-surface blackbody cavity according to the present invention. The blackbody is an enclosure 3 consisting of two types of the inner surfaces, which may be termed first surface 1 and second surface 2. It should be understood that the type of the outside surface of enclosure 3 has no effect whatsoever on it's performance as a blackbody. The best performance, by definition, is when a blackbody doesn't reflect anything...

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Abstract

A blackbody cavity having two types of wall surfaces wherein a first type has high emissivity and a second type has low emissivity. The low emissivity wall surface has an aperture from where the infrared radiation escapes the cavity, and is preferably shaped to minimize the escape through the aperture of radiation emanated directly from the low emissivity wall itself. The combination of high and low emissivity wall surfaces allows the blackbody to reduce the influence of the environmental temperature while maintaining emissivity approaching unity.

Description

[0001] This application is a continuation of application Ser. No. 09 / 432,861 filed on Nov. 2, 1999 (pending), the disclosure of which is hereby fully incorporated by reference herein.[0002] The present invention relates generally to test equipment for measuring electromagnetic emission in mid- and far-infrared spectral ranges and relates more specifically to a blackbody cavity for calibration of infrared thermometers.DESCRIPTION OF PRIOR ART[0003] Temperature of an object can be measured by means of thermal radiation when naturally emanated electromagnetic (thermal) radiation in the mid- and far-infrared (IR) spectral ranges is detected by an appropriate sensor. The IR sensor output signal is indicative of the surface temperature of an object. A sensor is an integral part of a measurement and / or data acquisition system. As a rule, a sensor is combined with some kind of an optical system which may include refractive and reflective components, such as lenses, mirrors, wave guides, win...

Claims

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Application Information

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IPC IPC(8): G01J5/52
CPCG01J5/522G01J5/53
Inventor FRADEN, JACOB
Owner ADVANCED MONITORS
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