Method and apparatus for determining radiation wavelengths and wavelength-corrected radiation power of monochromatic light sources

In a method of determining radiation wavelengths of substantially monochromatic optical radiation comprising the steps of

• transmitting monochromatic optical radiation to at least two photodetectors having different spectral sensitivity variations,
• supplying electrical output signals from said photodetectors to an electronic circuit for acquisitioning and processing measurement values, and
• supplying output signals depending on said optical radiation from said electronic circuit to an indicating circuit, said indicating circuit being calibrated to directly indicate radiation wavelengths,
• wherein the improvement comprises for a calibration technique the steps of obtaining said optical radiation from a calibrated monochromatic light source having a variable wavelength, obtaining said electrical output signals of said photodetectors at different wavelengths of said light source, distributing said different wavelengths substantially uniformly over a relevant measuring range, and storing said relevant measuring range in a digital memory circuit in association with said different wavelengths;
• wherein the improvement comprises for a subsequent measuring technique the step of comparing said electrical output signals of said photodetectors with sets of signals stored in said digital memory circuit for associated wavelengths, and providing an indication of conformity between wavelengths of said electrical output signals of said photodetectors and said associated wavelengths by said indicating circuit, and
• wherein in said calibration technique said light source includes an isoenergetic monochromatic light source of known power, said electrical output signals of said photodetectors obtained at different wavelengths, said wavelength being stored in said memory circuit in association with both wavelength and a respective radiation power where power correction factors are L(g);
• and wherein for measuring said radiation power, absolute values and wavelengths of respective electrical output signals of said photodetector are compared to combinations of values stored in said memory circuit, conformity between stored values and measured values being indicated by said indicating circuit.