Polarization Separation for Stable Light Intensity Control
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Solution Overview
Problem
The existing optical pickup apparatuses struggle to stably control light intensity for optical disc mediums like CD-R and CD-RW discs due to varying substrate birefringence and temperature-induced changes in the ratio of P-wave and S-wave components, especially when using a single light source for multiple wavelengths.
Innovation Solution
A light intensity control device that includes a light source outputting multiple wavelengths, a polarization separation section guiding both P-wave and S-wave components for one wavelength to a light receiving section, and suppressing the perpendicular components, allowing for stable light intensity control by using both P-wave and S-wave components for CDs and only P-wave for DVDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light source is used to output multiple wavelengths (DVD and CD), then device complexity is reduced, but light intensity control stability deteriorates due to varying substrate birefringence and temperature-induced polarization changes
Solution Approach 1:
The patent segments the light detection function into two separate light receiving sections: one dedicated to detecting P-wave components and another to detecting S-wave components. This segmentation allows independent monitoring of polarization components, enabling stable light intensity control for both DVD and CD wavelengths even when substrate birefringence or temperature causes polarization ratio variations.
Solution Approach 2:
The patent introduces a polarization separation section as an intermediary component between the light source and light receiving sections. This section separates the light beam into P-wave and S-wave components using a polarizing beam splitter, allowing each component to be detected independently. This intermediary structure enables accurate light intensity control without being affected by polarization ratio changes.
2Device complexity
If only P-wave component is used for light intensity control, then device complexity is reduced, but measurement precision deteriorates when substrate birefringence varies or temperature changes affect polarization ratio
Solution Approach 1:
The detection structure is segmented into two independent light receiving sections: one for P-wave components and another for S-wave components. This segmentation enables simultaneous monitoring of both polarization components, providing comprehensive light intensity measurement that remains accurate even when substrate birefringence or temperature causes polarization ratio variations.
Solution Approach 2:
The patent changes the detection parameter from monitoring only P-wave component to monitoring both P-wave and S-wave components separately. By detecting both polarization components and using their combined information for light intensity control, the system maintains measurement precision under varying substrate birefringence and temperature conditions.
3Measurement precision
If polarization separation section guides both P-wave and S-wave components to light receiving section, then light intensity control precision is improved, but device complexity increases
Solution Approach 1:
The polarization separation section using a polarizing beam splitter serves multiple functions simultaneously: it separates P-wave and S-wave components for independent detection, enables accurate light intensity control for both DVD and CD wavelengths, and maintains a relatively compact optical system structure. This multi-functional design achieves high measurement precision without excessive complexity increase.
Solution Approach 2:
The patent combines the polarization separation function with the existing optical path using a polarizing beam splitter that integrates into the current system architecture. By merging the polarization separation capability with the light detection system, the patent achieves improved light intensity control precision while minimizing the increase in overall device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise control of light intensity even with changes in polarization angle or ratio due to temperature characteristics, improving the stability and precision of light beam control across different optical disc types.
Implementation Method 1
a polarization separation section (2, 7) provided between the light source (1) and the light receiving section (8). The plurality of types of light beams include a first light beam and a second light beam having a longer wavelength than that of the first light beam; the polarization separation section (2, 7) guides both a light component in a first polarization direction of the second light beam and a light component in a second polarization direction, which is perpendicular to the first polarization direction, of the second light beam to the light receiving section (8)
Data Source
AI summary
A light intensity control device of the present invention includes a light source for outputting a plurality of types of light beams having different wavelengths; a light receiving section for receiving and converting the light beams into an electric signal in accordance with the intensity of the respective light beam; and a polarization separation section provided between the light source and the light receiving section. The plurality of types of light beams include a first light beam and a second light beam having a longer wavelength than that of the first light beam. The polarization separation section guides both a first polarization direction light component of the second light beam and a second polarization direction light component, perpendicular to the first polarization direction, of the second light beam to the light receiving section. The polarization separation section guides a first polarization direction light component of the first light beam to the light receiving section, and suppresses a second polarization direction component, perpendicular to the first polarization direction, of the first light beam from advancing to the light receiving section.