Laser Beam Spot Shape Detection with Concave Mirror and Beam Splitter
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Solution Overview
Problem
Condensers with large numerical apertures (NA) such as 0.4 to 0.9 face difficulties in capturing reflected light, making it challenging to detect the spot shape of a laser beam accurately in laser machining processes, which affects the desired machining outcomes due to potential distortions in the laser beam focus.
Innovation Solution
A laser beam spot shape detection method involving a concave mirror, beam splitting means, and imaging steps to position the focal point of the condenser near the concave mirror's reflecting face, allowing for the capture and analysis of reflected light images to determine the spot shape accurately, even with high NA condensers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a condenser with large numerical aperture (NA) is used to collect the laser beam, then the laser beam can be effectively focused, but the condenser cannot capture reflected light from the light emitter, making spot shape detection impossible
Solution Approach 1:
A beam splitting means is introduced as an intermediary component between the condenser and the imaging means. This beam splitter separates the incident laser beam path from the reflected light detection path, allowing the condenser to both focus the laser beam effectively and enable detection of the reflected light for spot shape measurement, thus resolving the contradiction between focusing accuracy and detection capability
Solution Approach 2:
The optical path is segmented into separate functional paths: one for laser beam delivery and focusing through the condenser, and another for reflected light detection through the beam splitter and imaging means. This segmentation allows each component to optimize its function without interference, enabling both high NA focusing and spot shape detection
2Productivity
If the focal point is positioned deep inside the wafer, then continuous modified layers can be formed along division lines, but the laser beam requires precise spot shape control which is compromised by optical distortion
Solution Approach 1:
The imaging means captures images of the reflected light to detect the actual spot shape of the focused laser beam. This detection information provides feedback about the spot shape accuracy, allowing for adjustments to be made to the laser beam oscillation or optical system to correct distortions, thereby maintaining manufacturing precision while enabling continuous modified layer formation
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
Enables precise detection of the laser beam spot shape, allowing for adjustments in the laser beam oscillation and optical system to achieve desired machining results, ensuring reliable detection even with condensers having large numerical apertures.
Implementation Method 1
a concave mirror holding step of holding a concave mirror having a spherical face forming a reflecting face with the chuck table; a beam splitting means positioning step of positioning beam splitting means at an acting position between the laser beam oscillation means and the condenser, the beam splitting means passing a laser beam from the laser beam oscillation means to the condenser and guiding reflected light, which is collected by the condenser and reflected by the reflecting face of the concave mirror
Implementation Method 2
a focal point positioning step of positioning a focal point of the condenser in a proximity including a center of the spherical face forming the reflecting face of the concave mirror held by the chuck table
Data Source
AI summary
Disclosed herein is a laser beam spot shape detection method for detecting a spot shape of a laser beam oscillated by laser beam oscillator and collected by a condenser in a laser machining apparatus, the laser beam spot shape detection method including: a concave mirror holding step of holding a concave mirror having a spherical face forming a reflecting face with a chuck table; a focal point positioning step of positioning the focal point of the condenser in a proximity including the center of the spherical face forming the reflecting face of the concave mirror held by the chuck table; a laser beam irradiation step of irradiating a laser beam onto the held concave mirror, and an imaging step of capturing images of reflected light with a camera.