Laser Scanning Optical System With Polarization-Stable Reflector
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Solution Overview
Problem
Conventional laser scanning optical systems struggle to suppress shading on imaging surfaces due to unpredictable changes in polarization states caused by optically-anisotropic materials, leading to uneven intensity distribution, especially when scanning optical elements with high birefringence are used.
Innovation Solution
A laser scanning optical system incorporating scanning optical elements made of materials with a photoelastic coefficient of 20×10−12 [Pa−1] or greater, combined with reflectors featuring a basal plate, a metal film, and a single-layer optical thin film with specific thickness and angle of incidence conditions to minimize reflectance unevenness across different polarization states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scanning optical elements made of materials with high birefringence (photoelastic coefficient ≥ 20×10−12 [Pa−1]) are used, then the polarization state of light changes significantly, but this leads to uneven intensity distribution and shading on the imaging surface
Solution Approach 1:
The patent changes the physical parameters of the reflector by specifying a single-layer optical thin film with thickness in the range of 0.15λ to 0.40λ (where λ is the wavelength of light). This parameter optimization ensures that reflectance differences between different polarization states are minimized, allowing the system to maintain uniform intensity distribution even when scanning optical elements with high birefringence cause polarization state changes.
2Manufacturing precision
If the polarization state of light is optimized for a specific scanning optical element configuration, then shading can be suppressed under expected conditions, but any deviation in polarization state causes uneven intensity distribution
Solution Approach 1:
The patent optimizes the thickness parameter of the optical thin film on the reflector to a specific range (0.15λ to 0.40λ) that minimizes the difference in reflectance between p-polarized and s-polarized light. This makes the system robust against polarization state variations, as the reflector maintains relatively uniform reflectance characteristics regardless of the incident light's polarization state, thereby suppressing shading even when polarization changes occur due to birefringence in scanning optical elements.
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
The system effectively suppresses reflectance and intensity unevenness on imaging surfaces, maintaining low reflectance differences across varying polarization states, even when scanning optical elements cause significant polarization changes, thereby ensuring consistent image quality.
Implementation Method 1
at least one of the one or more reflectors comprises a basal plate, and a metal film and a single-layer optical thin film evaporated on the basal plate
Implementation Method 2
one or more reflectors for receiving the light beam that passed through the one or more scanning optical elements and for reflecting the light beam toward the imaging surface
Implementation Method 3
one or more scanning optical elements for focusing the light beam deflected by the deflector on an imaging surface
Implementation Method 4
one or more scanning optical elements for focusing the light beam deflected by the deflector on an imaging surface
Implementation Method 5
a deflector for deflecting the light beam emitted from the light source
Implementation Method 6
the polarization state of the light entering the scanning optical element is mostly different from the polarization state of the light emitted from the light source, due to the birefringence effect of the optically-anisotropic matter
Data Source
AI summary
In a laser scanning optical system, at least one of one or more scanning optical elements is made of a material having a photoelastic coefficient equal to or greater than 20×10−12 [Pa−1]; wherein at least one of one or more reflectors comprises a basal plate, and a metal film and a single-layer optical thin film evaporated on the basal plate; wherein the single-layer optical thin film has a thickness greater than 0.15λ and less than 0.40λ, wherein λ is a wavelength of the light beam; and wherein the light beams heading to both ends of an effective scanning range of the imaging surface, of which image heights are maximum, enter the one or more reflectors at angles of incidence equal to or greater than 10 degrees and less than 55 degrees.