Non-contact techniques for measuring temperature or radiation-heated objects

In a process of heating an object by directing electromagnetic radiation within a defined bandwidth against at least one surface of the object from lamps energized by alternating current, wherein an intensity of the lamp radiation includes a time varying component, a method of determining a thermal characteristic of said object surface, comprising the steps of:

• detecting as a first signal a combined level of radiation emitted from said object surface within a predetermined bandwidth and a portion of said lamp radiation within said predetermined bandwidth that is reflected from said object surface, said predetermined bandwidth overlapping said defined source bandwidth,
• detecting as a second signal a level of lamp radiation that is being directed within said defined bandwidth against said object surface,
• determining a magnitude of a time varying component in each of said first and second signals that is the result of said source time varying component, and
• combining at least the time varying component magnitudes of said first and second signals in a manner to obtain said object surface thermal characteristic.

In a system for heating an article within a chamber having a substantially electromagnetic radiation of a given wall thereof by directing electromagnetic radiation of a given bandwidth through said window from outside of said chamber and against the object from a radiation source that also has a time varying intensity component, an improvement adapted to measure the temperature and/or emissivity of said article, comprising:

• first and second photodetectors, each of said photodetectors being characterized by generating an electrical signal proportional to a level of electromagnetic radiation incident thereon that includes said time varying intensity radiation component,
• means positioned with respect to the article for carrying to the first photodetector both a portion of source electromagnetic radiation reflected from said article surface area and electromagnetic radiation emitted by said article surface area within the bandwidth of the source electromagnetic radiation, thereby to generate a first electrical signal that contains a first time varying component,
• means positioned with respect to the source for carrying to the second photodetector a portion of source electromagnetic radiation substantially without any radiation reflected or emitted from said article surface, thereby to generate a second electrical signal that contains a second time varying component, and
• means receiving said first and second electrical signals for determining the temperature and/or emissivity of the object surface by at least combining magnitudes of the first and second electrical signal time varying components.

A non-contact method of measuring the temperature of an object being heated by a plurality of lamps energized by an alternating current power source and having radiation therefrom directed against a surface of the object and having a wavelength range within a visible of near visible portion of the electromagnetic radiation spectrum, comprising the steps of:

• detecting a combined level of electromagnetic radiation emitted from said object surface within a defined radiation bandwidth that lies within said source radiation wavelength range and a portion of said source radiation that is reflected from said object surface, thereby to obtain a first signal proportional to a sum of a level of source radiation reflected from the object and a level of radiation emitted from the object,
• detecting a level of electromagnetic radiation within said defined bandwidth that is being directed against said object surface, thereby to obtain a second signal proportion to the level of source radiation being directed against the object surface wherein said first and second signals each have a varying component, and
• combining said first and second signals by executing the following steps:
• taking a ratio of an amplitude of the varying components of each of the first and second signals,
• multiplying that ratio by a value of the second signal, thereby to determine an amount of the first signal that is due to reflected light, and
• subtracting said amount from said first signal, thereby determining a temperature dependent electromagnetic emission level from the object within said defined radiation bandwidth.

A non-contact method of measuring the temperature of a surface of an object, comprising the steps of:

• illuminating said object surface with optical radiation having a magnitude I.sub.L and a ripple component having a magnitude .DELTA.I.sub.L, thereby to cause optical radiation to be reflected from the surface and combined with temperature dependent optical radiation emitted therefrom, said combined optical radiation having a magnitude I.sub.W and a ripple component having a magnitude .DELTA.I.sub.W,
• detecting the magnitude and ripple component of the optical radiation being directed at said object surface,
• detecting the magnitude and ripple component of said combined optical radiation coming from the object surface, and
• combining said magnitude and ripple components substantially according to the following relationship:
• ##EQU4## thereby to measure the temperature of the object surface.

A non-contact method of measuring the emissivity of a surface of an object, comprising the steps of:

• illuminating said object surface with optical radiation having a ripple component with a magnitude .DELTA.I.sub.L, thereby to cause optical radiation to be reflected from the surface and combined with optical radiation emitted therefrom, said combined optical radiation having a ripple component with a magnitude .DELTA.I.sub.W,
• detecting the ripple component of the optical radiation being directed at said object surface,
• detecting the ripple component of said combined optical radiation coming from the object surface, and
• combining said ripple component substantially according to the following relationship:
• ##EQU5## thereby to measure the emissivity of the object surface.