Method of measuring optical characteristics of thin film and apparatus therefor

An apparatus for measuring optical characteristics of a thin film, comprising:

• a light source for radiating light on a transparent substrate and on the transparent substrate having a thin film formed thereon, in a predetermined order;
• a detector for detecting polarized states of lights which are generated by the light source and has passed through the transparent substrate, and through the thin film and the transparent substrate formed thereon, in said predetermined order;
• a measuring circuit, connected to the detector, for measuring a retardation and a direction of an optical axis of a transparent substrate, and a synthetic retardation and a direction of a synthetic optical axis of said transparent substrate and said thin film formed thereon in said predetermined order, based on the polarized states detected by said detector;
• a holding circuit, connected to the measuring circuit, for holding one of first data including the retardation and the direction of the optical axis of only said transparent substrate, which are measured by said measuring circuit, and second data including the synthetic retardation and the direction of the synthetic optical axis of said transparent substrate and said thin film formed thereon which are measured by said measuring circuit;
• and
• retardation arithmetic operation means, connected to the holding circuit, for calculating a value of a retardation and a direction of an optical axis of only said thin film on the basis of said one data from said holding circuit and the other of said first and second data from said measuring circuit.

A method of measuring optical characteristics of a thin film formed on a transparent substrate, comprising:

• a first preparing step of locating a thin film whose optical characteristics are to be measured and which is formed on a transparent substrate between a polarizer and an analyzer;
• a second preparing step of locating said transparent substrate without the film being formed thereon between the polarizer and the analyzer;
• a first radiating step of radiating light through the polarizer onto the thin film formed on the transparent substrate prepared in the first preparing step;
• a first detecting step of detecting a polarized state of light passed through the polarizer, the thin film, the transparent substrate and the analyzer;
• a synthetic retardation measuring step of measuring a value of a synthetic retardation and a direction of a synthetic optical axis of the transparent substrate and the thin film formed thereon, on the basis of the polarized state detected in the first detecting step;
• a second radiating step of radiating light through the polarizer onto the transparent substrate prepared in the second preparing step;
• a second detecting step of detecting a polarized state of light passed through the polarizer, the transparent substrate, and the analyzer,
• a substrate retardation measuring step of measuring a value of a synthetic retardation and a direction of a synthetic optical axis of only said transparent substrate on the basis of the polarized state detected in the second detecting step;
• and
• a retardation arithmetic operation step for calculating a value of a retardation and a direction of an optical axis of only said thin film in accordance with the value of the synthetic retardation and the direction of the synthetic optical axis which are measured in the synthetic retardation measuring step and the value of the retardation and the direction of the optical axis of only said transparent substrate, which are measured in the substrate retardation measuring step.

An apparatus for measuring optical characteristics of a thin film, comprising:

• a polarizer and an analyzer between which a sample, whose optical characteristics are to be measured, is located;
• a photoelastic modulator, located between said polarizer and analyzer, for changing a polarized state of light transmitted through said polarizer;
• a light source for radiating light on a transparent substrate, and on the transparent substrate on which a thin film is formed, through the polarizer and the photoelastic modulator, in a predetermined order;
• detector means for detecting a polarized state of light which is generated by the light source and has passed through the polarizer, the photoelastic modulator, the transparent substrate, and the analyzer, and a polarized state of light which is generated by the light source and has passed through the polarizer, photoelastic modulator, the thin film and the transparent substrate, and the analyzer, in said predetermined order;
• a measuring means, connected to the detector means, for measuring a retardation and a direction of an optical axis of the transparent substrate and a synthetic retardation and a direction of a synthetic optical axis of said transparent substrate having the thin film formed thereon, in a predetermined order, based on the polarized states detected by said detector means;
• a holding means, connected to the measuring means, for holding one of the first data including the retardation and the direction of the optical axis of only said transparent substrate, which are measured by said measuring means, and second data including the synthetic retardation and the direction of the synthetic optical axis of said transparent substrate and said thin film, which are measured by said measuring means;
• and
• retardation arithmetic operation means, connected to the holding means, for calculating a value of a retardation and a direction of an optical axis of only said thin film on the basis of said one data from said holding means and the other data of said first and second data from said measuring means.