| 摘要 |
Measurement equipment based on the measurement of light transmission are plagued by changing characteristics of protective glass surfaces due to contamination or other factors. In a method, light transmission is measured by sending light from a transmitter (1) and recording the received light intensity at a receiver (2), after which the light intensity is obtained by computation means. Light from light sources (5, 6) travels into protective glasses (3, 4) of the transmitter and the receiver so that the light rays are subjected to total internal reflection within the glasses, after which the intensities of the totally reflected light rays are measured by a detector (7, 8), and the obtained intensity values are used for correcting the intensity attenuation, effected by the protective glasses and their contamination onto the path from the transmitter to the receiver. The apparatus comprises light sources (5, 6) integral with the transmitter (1) and the receiver (2), with the light rays from the light sources adapted to enter the protective glasses in such a manner as to be subjected to a total internal reflection, and detectors (7, 8) for intensity measurement of the totally reflected light rays. |
