Laser Spot Elongation for SPM Photodetector Alignment
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Solution Overview
Problem
The existing scanning probe microscopes require a lengthy adjustment process for the photodetector position due to the inability to determine the direction for aligning the reflected laser beam when it is outside the detection area, leading to increased setup time.
Innovation Solution
The scanning probe microscope incorporates a laser beam adjustment unit that adjusts the laser beam to make the spot longer in one direction during adjustment, allowing for quicker alignment of the photodetector by increasing the likelihood of the beam entering the detection area, thereby reducing the time required for position adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the photodetector position is adjusted by randomly moving the photodetector when the reflected beam is outside the detection area, then the photodetector can eventually be aligned with the beam, but the adjustment time becomes excessively long
Solution Approach 1:
The patent changes the shape parameter of the laser spot from a standard circular/compact shape to an elongated shape. This parameter change allows the spot to cover a larger area in the direction perpendicular to the cantilever displacement direction, enabling the photodetector to detect the beam more easily during adjustment and significantly reducing the random search time while maintaining measurement accuracy.
Solution Approach 2:
The patent performs preliminary shaping of the laser spot before the photodetector alignment process begins. By pre-elongating the spot in the direction perpendicular to the cantilever displacement direction, the system prepares the optimal detection condition in advance, allowing the photodetector to quickly acquire the beam signal during adjustment without requiring extensive random positioning.
2Productivity
If the laser spot is made larger in the direction perpendicular to cantilever displacement to facilitate photodetector alignment, then the alignment speed increases, but the spot size in the measurement direction may be affected
Solution Approach 1:
The patent applies local quality by creating an anisotropic spot shape where the spot has different dimensions in different directions. The spot is elongated specifically in the direction perpendicular to the cantilever displacement direction (y-direction) while maintaining its original size in the measurement direction (x-direction). This allows the spot to cover a larger area for easier alignment detection without affecting the measurement precision in the critical direction.
Solution Approach 2:
The patent introduces asymmetry in the spot shape by making it elongated in one direction (perpendicular to cantilever displacement) rather than maintaining a symmetric circular shape. This asymmetric elongation creates a spot that is wider in the alignment-critical direction while preserving the original dimensions in the measurement direction, thereby decoupling the alignment performance from measurement precision requirements.
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 approach significantly reduces the time needed for photodetector position adjustment while maintaining measurement accuracy, eliminating the need for additional spot adjustments before sample analysis.
Implementation Method 1
an irradiation unit that irradiates the cantilever with a laser beam
Implementation Method 2
a change in a reflected beam of a laser beam applied to a rear surface of the cantilever
Implementation Method 3
The photodetector detects a change in position, intensity, phase and the like of the reflected beam, and converts the change into various pieces of physical information
Data Source
AI summary
A laser beam adjustment unit adjusts a laser beam applied to a cantilever. Assuming that a direction of displacement of a spot of the laser beam on a light receiving surface when the cantilever is displaced during measurement of properties of a sample is defined as a first direction, and a direction orthogonal to the first direction on the light receiving surface is defined as a second direction, the laser beam adjustment unit adjusts the laser beam such that a length of the spot of the laser beam in the second direction during adjustment of a position of a detection unit is longer than a length of the spot of the laser beam in the first direction during measurement of the properties of the sample.