Asymmetric Aperture Optical Shield for Stray Light Suppression
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Solution Overview
Problem
Conventional optical pickups face challenges in suppressing stray light without increasing production costs, as existing light-shielding masks require antireflection coatings to prevent reflection, which is costly and inefficient.
Innovation Solution
An optical pickup design featuring a light-shielding plate with an aperture positioned asymmetrically above the hologram element, blocking unnecessary light while allowing necessary light to pass through, reducing reflection and noise without the need for antireflection coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light-shielding mask is used to block stray light, then stray light suppression is improved, but production cost increases due to required antireflection coatings
Solution Approach 1:
The patent applies asymmetry by positioning the aperture of the light-shielding mask at an offset location rather than at the center of the hologram element. This asymmetric positioning allows the mask to block stray light paths while avoiding the need for antireflection coatings on the mask surface, thereby reducing manufacturing complexity and cost while maintaining effective stray light suppression
Solution Approach 2:
The invention extracts and removes the requirement for antireflection coatings from the light-shielding mask design. By carefully designing the aperture position and shape, the patent achieves stray light suppression without needing to apply additional reflective coatings, thus eliminating this costly manufacturing step while maintaining optical performance
2Use of energy by moving object
If an aperture is positioned centrally over the hologram region, then light transmission is maximized, but stray light reflection increases
Solution Approach 1:
The patent positions the aperture asymmetrically relative to the hologram region center. This asymmetric positioning strategically allows maximum necessary light transmission through the hologram element while simultaneously blocking reflected stray light paths from reaching the photodetector, achieving both objectives without requiring antireflection coatings
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
Effectively prevents unnecessary light from returning to the photodetector, improving signal quality and reducing production costs by eliminating the need for expensive antireflection coatings.
Implementation Method 1
a hologram element having a hologram region for guiding light having been reflected from the optical disk into a photodetector
Implementation Method 2
an optical shield for blocking at least a portion of light transmitted through a region of the hologram element other than the hologram region
Data Source
AI summary
An optical pickup according to the present invention includes: a light source 1d for irradiating an optical disk 4 with light; a lens 3 for converging the light onto the optical disk 4; a photodetector 1c having a plurality of detection regions 1cf, 1ct for detecting light which is reflected from a signal surface of the optical disk 4 and converting the light into an electrical signal; a hologram element 1a having a hologram region 1b for guiding the reflected light to the photodetector 1c; and a light-shielding plate 2 for blocking at least a portion of light transmitted through a region of the hologram element 1a other than the hologram region 1b. The light-shielding plate 2 includes a light shielding portion 2b for blocking light, and an aperture 2a for allowing the light to be transmitted therethrough. The aperture 2b is present, above an upper face of the hologram element 1a, in a region including the hologram region 1b, and a center position of the aperture 2b is shifted from a center position of the hologram region 1b.