Optical measurement apparatus and optical measurement method

An optical measurement method performed by using an optical measurement apparatus that includes an irradiation optical system and a reception optical system, the optical measurement method comprising:

• a step of irradiating a measurement subject with irradiation light that includes a plurality of wavelengths, by using the irradiation optical system;
• a step of receiving measurement light that is transmission light or reflection light travelling from the measurement subject with birefringence as a result of the measurement subject being irradiated with the irradiation light, by using the reception optical system;
• and
• a step of adjusting, by using an adjustment unit, a direction in which an absorption axis of a polarizing plate extends in a plane that intersects a light path of the irradiation light or a light path of the measurement light,
• wherein
• the adjustment unit adjusts the direction in which the absorption axis of the polarizing plate extends so that (a) an angle formed by the absorption axis of the polarizing plate and a slow axis of the measurement subject is within a range of −10 degrees to 10 degrees and an angle formed by the absorption axis of the polarizing plate and a fast axis of the measurement subject is within a range of 80 degrees to 100 degrees or (b) an angle formed by the absorption axis of the polarizing plate and a slow axis of the measurement subject is within a range of 80 degrees to 100 degrees and an angle formed by the absorption axis of the polarizing plate and a fast axis of the measurement subject is within a range of −10 degrees to 10 degrees, and
• in the step of irradiating the measurement subject with the irradiation light or the step of receiving the measurement light, the measurement subject is irradiated with the irradiation light passing through the polarizing plate, or the measurement light passing through the polarizing plate is received.

An optical measurement apparatus comprising:

• an irradiation optical system configured to irradiate a measurement subject with irradiation light that includes a plurality of wavelengths;
• a reception optical system configured to receive measurement light that is transmission light or reflection light travelling from the measurement subject with birefringence as a result of the measurement subject being irradiated with the irradiation light;
• a first polarizing plate;
• a second polarizing plate;
• and
• a mechanism configured to change a position of the first polarizing plate and a position of the second polarizing plate,
• wherein the first polarizing plate is configured to be moved between a position on a first light path in the irradiation optical system and a position outside the first light path by the mechanism, wherein the mechanism is configured to adjust a direction in which an absorption axis of the first polarizing plate extends in a plane that intersects the first light path of the irradiation light,
• the second polarizing plate is configured to be moved between a position on a second light path in the reception optical system and a position outside the second light path by the mechanism, wherein the mechanism is configured to adjust a direction in which an absorption axis of the second polarizing plate extends in a plane that intersects the second light path of the measurement light,
• when starting a measurement by using the optical measurement apparatus, (a) the first polarizing plate is moved to the position on the first light path by the mechanism, and the second polarizing plate is moved to the position outside the second light path by the mechanism, or (b) the first polarizing plate is moved to the position outside the first light path by the mechanism, and the second polarizing plate is moved to the position on the second light path by the mechanism,
• the mechanism adjusts the direction in which the absorption axis of the first polarizing plate extends, so that (a) an angle formed by the absorption axis of the first polarizing plate and a slow axis of the measurement subject is within a range of −10 degrees to 10 degrees and an angle formed by the absorption axis of the first polarizing plate and a fast axis of the measurement subject is within a range of 80 degrees to 100 degrees or (b) an angle formed by the absorption axis of the first polarizing plate and a slow axis of the measurement subject is within a range of 80 degrees to 100 degrees and an angle formed by the absorption axis of the first polarizing plate and a fast axis of the measurement subject is within a range of −10 degrees to 10 degrees,
• the mechanism adjusts the direction in which the absorption axis of the second polarizing plate extends, so that (c) an angle formed by the absorption axis of the second polarizing plate and a slow axis of the measurement subject is within a range of −10 degrees to 10 degrees and an angle formed by the absorption axis of the second polarizing plate and a fast axis of the measurement subject is within a range of 80 degrees to 100 degrees or (d) an angle formed by the absorption axis of the second polarizing plate and a slow axis of the measurement subject is within a range of 80 degrees to 100 degrees and an angle formed by the absorption axis of the second polarizing plate and a fast axis of the measurement subject is within a range of −10 degrees to 10 degrees.

An optical measurement apparatus comprising:

• an irradiation optical system configured to irradiate a measurement subject with irradiation light that includes a plurality of wavelengths;
• a reception optical system configured to receive measurement light that is transmission light or reflection light travelling from the measurement subject with birefringence as a result of the measurement subject being irradiated with the irradiation light;
• a polarizing plate;
• and
• a mechanism configured to change a position of the polarizing plate, wherein the mechanism is configured to adjust a direction in which an absorption axis of the polarizing plate extends in a plane that intersects a light path of the irradiation light or a light path of the measurement light,
• wherein the polarizing plate is configured to be moved between at least two of (a) a position on a first light path in the irradiation optical system, (b) a position on a second light path in the reception optical system, and (c) a position outside the first and second light path, by the mechanism,
• when starting a measurement by using the optical measurement apparatus, the polarizing plate is moved to the position on the first light path or the position on the second light path by the mechanism,
• the mechanism adjusts the direction in which the absorption axis of the polarizing plate extends, so that (a) an angle formed by the absorption axis of the polarizing plate and a slow axis of the measurement subject is within a range of −10 degrees to 10 degrees and an angle formed by the absorption axis of the polarizing plate and a fast axis of the measurement subject is within a range of 80 degrees to 100 degrees or (b) an angle formed by the absorption axis of the polarizing plate and a slow axis of the measurement subject is within a range of 80 degrees to 100 degrees and an angle formed by the absorption axis of the polarizing plate and a fast axis of the measurement subject is within a range of −10 degrees to 10 degrees.