Laser radiometer

A combined reflectometer and radiometer for accurate temperature measurement of a remote radiant source, comprising;

• a source of a laser light signal;
• lens means for intercepting an amount of thermal radiation emitted by said radiant source;
• means for alternately superimposing said thermal radiation with said laser signal and directing said signal to illuminate at least a predetermined portion of said radiant source;
• photodetector means positioned to receive said superimposed thermal radiation and laser signal said photodetector being responsive to produce a subject beat signal which is proportional to a value of thermal radiance for said remote source;
• discriminator means being operative to distinguish said subject signal from unwanted noise signals;
• means for detecting at least a portion of diffusely reflected laser light signal over a predetermined solid angle, said detecting means being responsive to provide a photoelectric signal which is a known function of emissivity for said illuminated surface whereupon compensating said value for thermal radiance for said emissivity an accurate measurement of the temperature of the remote radiant source is provided, said detecting means collecting a plurality of speckle lobes of varying brightness of said reflected laser signal of sufficient number so as to obtain a spatial average over the intensity of said reflected laser signal.

A combined reflectometer and radiometer for accurately measuring a temperature for a remote radiant source through an interfering medium comprising;

• a laser source having an output signal of about wavelength .lambda.;
• said interfering medium being substantially transparent to light energy of wavelength .lambda.;
• lens means for intercepting an amount of thermal energy radiated by said remote source;
• means for optically combining said thermal radiation with said laser signal;
• photodetector means, positioned to receive said comixed signal said photodetector being responsive to said signal to produce a beat signal which is proportional to a value for the thermal radiance of said remote source;
• means for illuminating at least a portion of a surface region of said remote source with a predetermined laser signal having a wavelength equal to about .lambda., said signal being substantially diffusely reflected from said surface;
• means for detecting a portion of said reflected signal over a predetermined solid angle said detecting means including a photodetector being responsive to said detected signal to provide an electrical signal which is a known function of the emissivity for said surface whereupon adjusting said value for the thermal radiance by said emissivity obtained for the surface of the radiant source, an accurate temperature measurement of the radiant source is provided, said detecting means collecting a plurality of speckle lobes of varying brightness of said reflected laser signal of sufficient number so as to obtain a spatial average over the intensity of said reflected laser signal.

A method for accurately measuring a temperature of a remote radiant source, said method comprising;

• intercepting an amount of thermal radiation emitted from said source;
• superimposing said intercepted radiation with a laser signal;
• detecting said superimposed signals with a photodetector to provide a subject electrical beat signal, a value of power for said signal being a known function of the thermal radiance of said source;
• discriminating said subject signal from unwanted noise signals;
• illuminating a surface region of said remote source with a laser signal, said signal being diffusely refelcted from said surface region;
• detecting a plurality of speckle lobes of varying brightness of said reflected signal over a predetermined solid angle of sufficient number so as to obtain a spatial average over the intensity of said reflected signal, said reflected signal providing a signal which is a known function of emissivity for said surface region;
• compensating said value for thermal radiance for said emissivity to provide an accurate measurement of the temperature of the remote radiant source.

A laser temperature measuring device for temperature measurement of a remote radiant source, said device comprising;

• a. means for intercepting an amount of thermal radiation emitted from said radiant source;
• b. a photodetector positioned to receive said radiation, said photodetector responding thereto to provide a subject electrical signal, a value of electrical current for said signal being a known function of thermal radiance of the remote source, thereby providing a value for said thermal radiation;
• c. discriminator means being operative to distinguish a subject signal from unwanted noise signals;
• d. a laser having a principal output at wavelength .lambda.;
• e. means for illuminating at least a portion of said radiant source with said laser signal, whereupon an amount of said illuminating laser signal is diffusely reflected from a surface region of said radiant source;
• f. means for detecting at least a portion of said diffusely reflected laser signal over a predetermined solid angle, said detecting means being responsive to provide a phtotelectric signal which is a determinable function of the emissivity for a surface region of said radiant source whereupon compensating said value of thermal radiance for said emissivity an accurate measurement of the temperature of the remote radiant source is provided, said detecting means collecting a plurality of speckle lobes of varying brightness of said reflected laser signal of sufficient number so as to obtain a spatial average over the intensity of said reflected laser signal.