Simple birefringence measurement method for coated optical disks with a fixed incident angle ellipsometer

Area of Science:

• Materials Science
• Optics
• Polymer Science

Background:

• Optical disks rely on polycarbonate substrates with specific birefringence properties.
• Current oblique incidence retardation measurements for coated disks are limited to reflectance methods.
• Evaluating both lateral and vertical birefringence is crucial for optical disk performance.

Purpose of the Study:

• To propose a novel, simple measurement method for simultaneously evaluating lateral and vertical birefringence in coated optical disk substrates.
• To offer an alternative to existing, potentially complex, birefringence measurement techniques.
• To facilitate routine quality inspection in optical disk manufacturing.

Main Methods:

• A reflectance method using oblique incidence retardation measurements.
• Measurement of two retardation values at a fixed incident angle from radial and circumferential directions.
• Calculation of lateral and vertical birefringence using the sum and difference of measured retardation values.

Main Results:

• Simultaneous measurement of lateral and vertical birefringence is achieved.
• The method eliminates the need for complex curve-fitting procedures.
• The proposed technique is straightforward and applicable to coated substrates.

Conclusions:

• The developed method provides a simple and effective way to measure birefringence in coated optical disks.
• This technique can be readily integrated into standard optical disk manufacturing processes.
• Accurate birefringence assessment enhances optical disk quality and reliability.