Optical Mask Spatial Intensity Modulation for Laser Spot Control
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Solution Overview
Problem
LG mode light suffers from low resolution and low energy concentration due to its ring-shaped side lobe, and existing techniques for radially polarized laser beams are ineffective for linearly polarized beams and have low light use efficiency, especially at low NA.
Innovation Solution
An optical mask with spatial intensity modulation and an optical phase modulation element that applies phase modulation to coherent light, using regions defined by circumferences with specific radii proportional to the square roots of Laguerre polynomial roots, to selectively transmit light through specific regions, reducing central spot diameter and increasing energy concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LG mode light is used to concentrate energy at a minute region, then energy concentration is improved, but resolution deteriorates due to ring-shaped side lobe
Solution Approach 1:
The invention divides the light beam into multiple high-order mode components (LG modes with different radial indices) and processes them separately through the optical mask. Each mode contributes to different aspects of the focal spot, allowing the central spot to be minimized while side lobes are suppressed through constructive and destructive interference patterns.
Solution Approach 2:
The invention changes the spatial distribution parameters of the light beam by using an optical mask with specific transmission regions defined by Laguerre polynomial roots. This transforms the input light intensity profile into a modified profile that produces a tighter central spot with reduced side lobes after focal condensation.
2Length of moving object
If radially polarized laser beam is condensed by high-NA lens, then central spot diameter is reduced, but light use efficiency deteriorates because only outer periphery light is condensed
Solution Approach 1:
The invention creates a universal optical mask design that works with both linearly polarized and radially polarized light, as well as with both low-NA and high-NA lenses. The mask structure based on Laguerre polynomial roots provides a general solution that adapts to different polarization states and numerical apertures, making the system versatile and efficient.
3Use of energy by moving object
If three-ring filter is used to form minute spot, then energy concentration is improved, but resolution deteriorates and side lobe problems persist
Solution Approach 1:
The invention generalizes the three-ring filter concept by using an optical mask with transmission regions defined by the roots of Laguerre polynomials of arbitrary order. This allows optimization of the light intensity distribution parameters to achieve both tight central spots and suppressed side lobes, overcoming the limitations of fixed three-ring designs.
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 solution effectively reduces the central spot diameter and enhances energy concentration at the central spot, improving light use efficiency and resolution, regardless of the NA of the lens, and is applicable to both linearly and radially polarized light.
Implementation Method 1
an optical mask which applies spatial intensity modulation to input light in a beam cross-section and outputs light after being subjected to the modulation
Implementation Method 2
an optical phase modulation element which applies phase modulation to light according to positions on a beam cross-section of the light and outputs light after being subjected to the phase modulation
Implementation Method 3
a beam waist diameter as a standard of the size of a condensed light diameter can be reduced only to approximately half of the light wavelength. This is called the diffraction limit.
Implementation Method 4
a condensing optical system which condenses light output from the light source to a focal point
Data Source
AI summary
This optical mask is an optical mask which applies spatial intensity modulation to input light in a beam cross-section and outputs a light after being subjected to the modulation, and when regions A0 to Ap defined by circumferences with p radiuses r1 to rp (p is an even number, rp>rp−1> . . . >r2>r1, and rp−rp−1>rp−1−rp−2> . . . >r3−r2>r2−r1>r1) around a predetermined position are set in order from an inner side, a region Am (m is an even number not less than 0 and not more than p) is a light transmission region, and a region An (n is an odd number not less than 0 and not more than p) is a light shielding region.