| 摘要 |
<p>PROBLEM TO BE SOLVED: To measure a birefringence value of a material showing a tendency of low birefringence with high accuracy.SOLUTION: A method for measuring birefringence is provided, which includes a step of acquiring a first correspondence relation between a rotation angle of a half-wave plate and a luminous energy ratio through: steps of transmitting an inspection beam, which is emitted from a light source unit 101 and transmitted through a light-transmitting article 10, through a half-wave plate 104, then separating the inspection beam by an optical separator 108 into two linearly polarized beams orthogonal to each other, measuring luminous energy of the beams with respective two luminous energy measurement devices 106a, 106b, and calculating a luminous energy ratio by dividing one of the two measurement values by the sum of the two measurement values; and a step of repeating several times the above described steps by rotating the half-wave plate to change angles of the polarization planes. The method further includes: a step of acquiring a reference correspondence relation under the same conditions in the above step of acquiring the first correspondence relation without disposing the light-transmitting article; a step of calculating a relative luminous quantity ratio in the first correspondence relation and the reference correspondence relation at the same rotation angle of the half-wave plate; and a step of acquiring a birefringent value at the measurement position by using the relative luminous quantity ratio of the first correspondence relation, based on a preliminarily acquired correspondence relation between a relative luminous quantity ratio and a birefringent value.</p> |
