VCSEL Optical Scanning Device with Neutral Density and Antireflection Coatings
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Solution Overview
Problem
Conventional optical scanning devices using vertical-cavity surface-emitting lasers (VCSELs) face challenges in maintaining consistent light output due to variations in optical energy efficiency and shading characteristics, which are exacerbated by the use of neutral density filters that cause multiple interference and wavelength changes, leading to instability in light intensity.
Innovation Solution
The implementation of an optical scanning device with a VCSEL light source, a first optical system, a deflecting unit, a second optical system, and a light-quantity adjusting element with a substrate having a neutral density coating on one surface and an antireflection coating on the other, positioned between the light source and the deflecting unit, to control light use efficiency and prevent multiple interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a neutral density filter is used to adjust light quantity, then light use efficiency can be controlled, but multiple interference occurs causing light intensity instability
Solution Approach 1:
The patent extracts the harmful reflective surfaces from the neutral density filter by applying antireflection coatings to both surfaces, removing the source of multiple interference while preserving the light attenuation function
Solution Approach 2:
The patent converts the harmful effect of reflections into a beneficial outcome by using antireflection coatings to eliminate interference patterns, thereby stabilizing light intensity while maintaining the neutral density filter's light quantity control capability
2Speed
If the VCSEL operates at higher speeds, then scanning speed increases, but longitudinal mode hopping occurs causing wavelength changes
Solution Approach 1:
The patent introduces the neutral density filter with antireflection coatings as an intermediary element that stabilizes the optical path, preventing feedback into the VCSEL that could cause mode hopping, thereby enabling high-speed operation with wavelength stability
3Productivity
If multiple beams are used for high-speed scanning, then productivity increases, but variations in light use efficiency and shading characteristics worsen
Solution Approach 1:
The patent applies different coatings to different surfaces of the neutral density filter (antireflection coating on both surfaces) to address local optical quality issues, ensuring consistent light output across multiple beams by eliminating surface-specific reflections and interference patterns
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 configuration stabilizes light output, reduces variations in light use efficiency, and prevents longitudinal mode hopping, enabling high-speed and high-density optical scanning with consistent image formation and communication.
Implementation Method 1
The first surface of the light-quantity adjusting element is coated with neutral density coating
Implementation Method 2
the second surface of the light-quantity adjusting element is coated with antireflection coating so that reflectance of the second surface is made smaller than reflectance of the first surface
Implementation Method 3
a vertical-cavity surface-emitting laser light source that emits laser beams perpendicular to a top surface thereof
Data Source
AI summary
An optical scanning device includes a vertical-cavity surface-emitting laser light source that emits laser beams perpendicular to a top surface thereof; a first optical system that couples the beams from the light source; a deflecting unit that deflects the beams; a second optical system that guides the beams from the first optical system to the deflecting unit; a third optical system that focuses the beams deflected by the deflecting unit into an optical spot on a scanned surface; and a light-quantity adjusting element disposed between the light source and the deflecting unit and having a substrate formed of a first and second surfaces. The first surface of the light-quantity adjusting element is coated with neutral density coating and the second surface is coated with antireflection coating so that reflectance of the second surface is made smaller than reflectance of the first surface.