Lens Array for Uniform Laser Spot in Metal Property Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The laser ultrasonic wave method for measuring metal material properties faces reduced measurement accuracy due to pulse ultrasonic wave attenuation and diffusion, leading to a deteriorated signal-to-noise ratio, which is not adequately addressed by simply amplifying the pulse laser beam with a non-uniform beam profile.
Innovation Solution
A property measurement system utilizing a laser oscillator, a lens array with small lenses arranged in a matrix, and a condensing lens to create a uniform light distribution on the metal material surface, enhancing the signal-to-noise ratio by suppressing ultrasonic wave diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spot size of the pulse laser beam is increased to suppress diffusion of the pulse ultrasonic wave, then the diffusion is reduced, but the light quantity distribution becomes non-uniform with larger amplitude difference between center and periphery
Solution Approach 1:
The patent divides the single large lens into an array of multiple small lenses arranged in a matrix. Each small lens focuses light onto a corresponding region of the metal material surface, creating multiple localized high-intensity spots. This segmentation approach allows the overall spot size to be large (suppressing diffusion) while maintaining uniform light distribution across the entire irradiated area, as each small lens contributes equally to the overall pattern.
Solution Approach 2:
The patent applies different optical characteristics to different regions of the irradiated area by using an array of small lenses. Each small lens creates a localized focus with high light intensity, ensuring that all regions of the metal material surface receive approximately equal energy density. This local quality control prevents the amplitude difference problem that occurs with a single large lens, where the center would have higher intensity than the periphery.
2Reliability
If a single large lens is used to increase spot size, then diffusion is suppressed, but the beam profile remains non-uniform with larger amplitude difference between center and periphery
Solution Approach 1:
The patent replaces a single large lens with an array of multiple small lenses. This segmentation allows the system to achieve a large overall spot size (suppressing diffusion) while each small lens contributes to creating a uniform amplitude distribution across the entire irradiated area. The multiple small lenses collectively provide the same diffusion suppression as a single large lens, but with superior amplitude uniformity.
3Area of stationary object
If the pulse laser beam is simply amplified to increase spot size, then the spot size increases, but the light quantity distribution remains non-uniform causing remarkable amplitude reduction of pulse ultrasonic wave
Solution Approach 1:
The patent uses an array of small lenses to create a uniform light distribution pattern across a large spot size. Each small lens focuses light onto its corresponding region, ensuring that all areas receive equal energy density. This segmentation approach prevents the non-uniform light distribution that would otherwise cause remarkable amplitude reduction of the pulse ultrasonic wave, thereby maintaining high signal-to-noise ratio while achieving large spot size.
Solution Approach 2:
The patent changes the optical parameters by replacing a single lens with an array of small lenses, fundamentally altering how light is distributed across the target area. This parameter change enables simultaneous achievement of large spot size and uniform light distribution, preventing the amplitude reduction problem that occurs with simple amplification of a single beam.
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 achieves improved measurement accuracy by maintaining a consistent ultrasonic wave amplitude and reducing diffusion, thereby enhancing the signal-to-noise ratio and preventing the degradation of measurement quality.
Implementation Method 1
a laser oscillator (10) that emits a pulse laser beam (Lp)
Implementation Method 2
irradiating a pulse laser beam onto a surface of the metal material and analyzing the propagation behavior of a pulse-like ultrasonic wave (hereinafter, referred to as a 'pulse ultrasonic wave') in the metal material, the ultrasonic wave having a high frequency generated at the time when the pulse laser beam is irradiated
Implementation Method 3
a lens array (20) that has a plurality of small lenses (Ls) with the same shape, the small lenses being laid in a matrix on a plane perpendicular to the optical axis of the pulse laser beam (Lp)
Implementation Method 4
a condensing lens (30) that overlaps and condenses emitted beams (Ld) coming from the plurality of small lenses (Ls) of the lens array (20) on the same region of a surface (101) of a metal material (100) as a measurement target
Implementation Method 5
a laser interferometer (41) that detects, as an electric signal, a pulse ultrasonic wave (SW) that is excited by the pulse laser beam (Lp) condensed by the condensing lens (30) and propagates through the inside of the metal material (100)
Implementation Method 6
a laser interferometer (41) that detects, as an electric signal
Data Source
AI summary
A property measurement system for a metal material includes: a laser oscillator that emits a pulse laser beam; a lens array that has small lenses with a same shape, the small lenses being laid in a matrix on a plane perpendicular to an optical axis of the pulse laser beam, and arranged so that a part of a cross section of the pulse laser beam can be made incident onto each of small lenses; a condensing lens that overlaps and condenses emitted beams coming from the small lenses on a same region of a surface of a metal material as a measurement target; a laser interferometer that detects, as an electric signal, a pulse ultrasonic wave that is excited by the pulse laser beam condensed and propagates through an inside of the metal material; and a signal processing device that processes the electric signal.