Self-calibrating photoacoustic apparatus for measuring light intensity and light absorption
US4184768A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 4, 1977 |
| Grant date | Jan 22, 1980 |
| Priority date | — |
| Expiry date | Nov 4, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/1702
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Pulsed light and readily measurable pulsed electrical energy are independently applied to a solid black, conductive sample in a gas-filled photoacoustic cell, each causing the black sample to heat. The heating of the black sample causes a pressure wave in the cell, which can be detected and measured. By adjusting the pulsed electrical energy, the pressure wave resulting from the pulsed electrical energy can be made to relate to the pressure wave resulting from the pulsed light in a predetermined manner. The pulsed light input intensity can then be measured in electrical units based on the measurable input of the electrical energy pulses. In this manner, the invention can be used as a radiometer. A second application for the present apparatus is in calibrating photoacoustic spectroscopy (PAS) cells. The PAS cell can be self-calibrated by discontinuing the light pulses and relating the pressure wave output to the electrical energy pulse input. The measurement then of light absorption in a test sample, which need be neither black nor conductive, can be made in absolute energy units based on the self-calibration relationship.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.