Patent ID: 7943895

Claim:
A wavelength splitting element for splitting a multiplexed light beam in wavelength bands λ 1 , λ 2 and λ 3 into light beams in separate wavelength bands and emitting the split light beams from separate emission ports, comprising: a first filter for splitting the multiplexed light beam in the wavelength bands λ 1 , λ 2 and λ 3 into a light beam in the wavelength band λ 1 that the first filter passes in a first direction and into a light beam in the wavelength bands λ 2 and λ 3 that the first filter reflects; a second filter, which is provided in the direction of the light beam in the wavelength bands λ 2 and λ 3 that has been reflected by the first filter, for splitting the light beam in the wavelength bands λ 2 and λ 3 that has been reflected by the first filter into a light beam in the wavelength band λ 3 that the second filter passes in a second direction and into a light beam in the wavelength band λ 2 that the second filter reflects in a third direction; and a third filter, which is provided in the direction of the light beam that has been reflected by the second filter, for passing the light beam in the wavelength band λ 2 that has been reflected by the second filter, wherein the first filter has characteristics to pass the light beam in the wavelength band λ 2 that has been reflected by the second filter and incident to the first filter again in the third direction depending on an incident angle, and the third filter has characteristics to pass only the light beam in the wavelength band λ 2 out of the light beams that the first filter passes in the third direction.