Methods for wavelength discrimination of monochromatic light beams

A method for detection and wavelength discrimination of a monochromatic light beam comprising;

• installing at least one detector pair consisting of a first photo detector with progressively increasing active area per unit distance in one direction and a second photo detector aligned with the first, with progressively decreasing active area per unit distance in said direction,
• installing at least one variable filter on top of said detector pair, the maximum transmission wavelength of said variable filter varying with distance in said direction,
• measuring a first photo current generated in said first photo detector due to illumination of said monochromatic light beam through said variable filter,
• measuring a second photo current generated in said second photo detector due to illumination of said monochromatic light beam through said variable filter,
• comparing value of said first photo current and value of said second photo current,
• determining wavelength of said light beam from variation of maximum transmission wavelength of said variable filter in said direction.