Patent ID: 8279439

Claim:
A birefringence measuring device for measuring a size of birefringence less than ¼ wavelength existing in an object to be measured and an azimuth thereof, comprising: a light source configured to emit a light flux having a specific polarization state towards said object to be measured; an optical system configured to extract each light flux in predetermined three polarization directions from the light flux having passed said object to be measured; a detector configured to detect a light amount of each of the light fluxes in the predetermined three polarization directions extracted by the optical system; and a processor configured to calculate a size of birefringence of said object to be measured and an azimuth thereof by assigning each light amount of said detected light fluxes detected by the detector to a predetermined function expression, wherein axes of 45°, 0°, and 90°, respectively, are set as the predetermined three polarization directions, and when i 1 , i 2 , i 3 are obtained as the light amounts in each of the predetermined three polarization directions, the processor is configured to calculate the size and the azimuth of the birefringence of said object to be measured by at least one of the following expressions: ϕ = 1 2 ⁢ tan - 1 ⁡ ( i 2 - i 3 - 2 ⁢ ⁢ i 1 + i 2 + i 3 ) ⁢ ⁢ γ = sin - 1 ⁡ ( - 2 ⁢ ⁢ i 1 + i 2 + i 3 ( i 2 + i 3 ) ⁢ cos ⁢ ⁢ 2 ⁢ ⁢ ϕ ) ⁢ ⁢ and [ Expression ⁢ ⁢ B1 ] ϕ = 1 2 ⁢ tan - 1 ⁡ ( i 2 - i 3 - 2 ⁢ ⁢ i 1 + i 2 + i 3 ) ⁢ ⁢ γ = sin - 1 ⁡ ( i 2 - i 3 ( i 2 + i 3 ) ⁢ sin ⁢ ⁢ 2 ⁢ ⁢ ϕ ) . [ Expression ⁢ ⁢ B2 ]