Laser Spot Shape Detection Using Luminescent Substrate
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Solution Overview
Problem
The existing methods for detecting the spot shape and focal position of a laser beam in laser processing apparatuses are inaccurate due to scattered light from obscure glass substrates, which affects the quality of laser processing.
Innovation Solution
A method involving a detection substrate with a luminescent substance that emits light when exposed to the laser beam, using a photodetector to map light intensity across the substrate, and forming spot shape images by positioning the focusing means at various Z-coordinates to accurately determine the spot shape and focal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an obscure glass substrate is used for spot shape detection, then the detection process can be performed, but scattered light from the substrate reduces measurement precision
Solution Approach 1:
A translucent substrate is introduced as an intermediary medium between the laser beam and the detection system. The substrate allows the laser beam to pass through while enabling optical imaging from the back side, mediating between the need for physical support and the requirement for clear optical detection without scattered light interference
Solution Approach 2:
The spot shape on the translucent substrate is optically imaged and copied onto a detection surface or sensor. This creates a replica of the spot pattern that can be analyzed without directly observing the original spot, thereby avoiding scattered light from the substrate and enabling precise measurement of spot shape and focal position
2Power
If a combination lens is used for focusing the laser beam, then the laser beam can be focused, but optical distortion prevents the focused spot from achieving the intended circular shape
Solution Approach 1:
The method utilizes the luminescent properties and optical absorption characteristics of the translucent substrate at specific wavelengths. By selecting a substrate with appropriate optical properties for the laser wavelength, the system can detect the spot shape through luminescence or absorption patterns that reveal the true spot geometry despite optical distortions from the combination lens
Solution Approach 2:
The detection method measures the actual spot shape parameters (size, ellipticity, position) formed by the combination lens and uses this information to compensate for or correct the optical distortions. By characterizing the distortion at different positions and adjusting processing parameters accordingly, the system achieves accurate spot shape control despite using a combination lens configuration
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 method allows for precise detection of the laser beam spot shape and focal position, enabling improved laser processing quality by identifying the focused spot and determining the optimal focal length.
Implementation Method 1
the detection substrate having a luminescent substance formed from a minute particle capable of emitting light by the application of the laser beam thereto
Implementation Method 2
detecting the intensity of light emitted from the luminescent substance by using a photodetector
Data Source
AI summary
The spot shape of a laser beam is detected by moving a table holding a detection substrate having a luminescent substance in an X direction and a Y direction with a laser beam focused by a lens applied to an area of the detection substrate where the luminescent substance is located. The intensity of light emitted from the luminescent substance is detected during the movement of the table, and a light intensity map is prepared indicating the light intensities detected in the light intensity detecting step at all of the X and Y coordinates of the luminescent substance. Spot shape images of the laser beam are formed according to a plurality of light intensity maps obtained by positioning the focusing lens at a plurality of detection positions changed in a Z direction perpendicular to a holding surface of the table.