| 摘要 |
PROBLEM TO BE SOLVED: To provide an instrument to be installed in a polarizing plate production line so as to accurately measure a phase difference without depending on a value of the phase difference R, and obtain a wavelength dispersion characteristic R (λ) of the exact phase difference.SOLUTION: A phase difference measuring section contains three sets of polarizers 4a to 4c, analyzers 5a to 5c, and spectrometers 10a to 10c disposed along a moving direction of a measurement object 7. The polarizers 4a to 4c and the analyzers 5a to 5c in each set are disposed in a parallel Nicol state and have a polarization azimuth θ set to 0°, 45° and 90° against a reference azimuth, respectively. A retardation plate 6 is disposed in an azimuth orthogonally overlapping the measurement object 7. A phase difference value of this retardation plate 6 has been set so that the phase difference value in a state of orthogonally overlapping the measurement object 7, is λ/2 or less in a range of a wavelength λ of measuring light. An arithmetic processing section 11 calculates a phase difference R in a plurality of wavelengths from a detection light intensity Ii(θ) for each wavelength λ to the three polarization azimuths θ, based on a principle of a parallel Nicol rotation method, thereby obtaining the wavelength dispersion characteristic R(λ) of the phase difference. |
