Optical apparatus and method for measuring temperature of a substrate material with a temperature dependent band gap
First Claim
1. An apparatus for measuring the temperature of a substrate material by inference from its band gap measured by diffuse reflectivity comprising:
- (a) white light lamp means for emitting broad spectrum white light;
(b) focusing means for focusing the white light emitted from the lamp means upon a front surface of a substrate material which is polished on the front surface and is polished or textured on a back surface, said white light being specularly reflected from the front surface of the substrate material and non-specularly reflected from the back surface of the substrate material;
(c) a diffuser means located adjacent the back surface of the substrate material for non-specularly reflecting the white light emitted from the lamp means;
(d) detector means positioned at a non-specular position on the front side of the substrate material for detecting non-specularly reflected white light from the back surface of the substrate material;
(e) optical fibre bundle means for collecting non-specularly reflected light detected by the detector means; and
(f) computing means for determining a temperature dependent band gap from onset wavelength of non-specular reflection from the back surface of the substrate material transmitted through the optical fibre bundle means.
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Abstract
An optical method and apparatus for measuring the temperature of a substrate material with a temperature dependent bandgap. The substrate is illuminated with a broad spectrum lamp and the bandgap is determined from the spectrum of the diffusely scattered light. The spectrum of the light from the lamp is sufficiently broad that it covers the spectral range above and below the bandgap of the substrate. Wavelengths corresponding to photon energies less than the bandgap of the substrate are transmitted through the substrate and are reflected from the back surface of the substrate as well as from the front surface while the wavelengths corresponding to photon energies larger than the bandgap are reflected only from the front surface. If the front surface is polished the front surface reflection will be specular while if the back surface is rough the reflection from the back surface will be non-specular. The back surface reflection is detected with a detector in a non-specular location. From the wavelength of the onset of the non-specular reflection the bandgap can be determined which gives the temperature. The temperature is determined from the knee in the diffuse reflectance spectrum near the bandgap.
109 Citations
17 Claims
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1. An apparatus for measuring the temperature of a substrate material by inference from its band gap measured by diffuse reflectivity comprising:
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(a) white light lamp means for emitting broad spectrum white light; (b) focusing means for focusing the white light emitted from the lamp means upon a front surface of a substrate material which is polished on the front surface and is polished or textured on a back surface, said white light being specularly reflected from the front surface of the substrate material and non-specularly reflected from the back surface of the substrate material; (c) a diffuser means located adjacent the back surface of the substrate material for non-specularly reflecting the white light emitted from the lamp means; (d) detector means positioned at a non-specular position on the front side of the substrate material for detecting non-specularly reflected white light from the back surface of the substrate material; (e) optical fibre bundle means for collecting non-specularly reflected light detected by the detector means; and (f) computing means for determining a temperature dependent band gap from onset wavelength of non-specular reflection from the back surface of the substrate material transmitted through the optical fibre bundle means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification