Laser Processing Device with Shack-Hartmann Sensor Height Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Shack-Hartmann sensors are limited in measuring changes in overall thickness or height of objects, particularly when objects of varying thickness are stacked, as they require a large probe light size and a height difference within a specific measurement limit, making it difficult to accurately measure thickness differences.
Innovation Solution
A laser processing device that includes a measuring device with a Shack-Hartmann sensor to detect changes in reflected light, a calculation unit to calculate height changes using Zernike polynomials, and a focus adjusting mechanism to automatically adjust the focus of laser light based on measured height changes, enabling real-time accurate processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Shack-Hartmann sensor is used to measure surface shape by detecting wavefront distortions, then the surface shape measurement is achieved, but the measurement is limited to height differences within a specific range (about 30 times the wavelength) and cannot measure overall thickness changes
Solution Approach 1:
The measurement function is divided into two independent parts: a Shack-Hartmann sensor for high-precision surface shape measurement and a separate height measurement device for overall thickness measurement. This segmentation allows each device to specialize in its respective measurement range without mutual interference, resolving the contradiction between precision and versatility.
Solution Approach 2:
A height measurement device acts as an intermediary to measure the overall thickness or height of the object, which then provides this information to the laser processing system. This intermediary measurement enables the system to handle objects with varying overall dimensions while the Shack-Hartmann sensor continues to provide precise surface shape data.
2Area of stationary object
If the probe light size is increased to include both stacked wafers and reference surface, then the measurement coverage is improved, but the height difference between reference surface and measurement surface must not exceed the measurement limit
Solution Approach 1:
The measurement system is segmented into two independent measurement functions: one for overall height/thickness using a height measurement device, and another for surface shape using the Shack-Hartmann sensor. This allows the probe light to cover the entire area without being constrained by height difference limitations, as each measurement type uses its own dedicated device.
3Device complexity
If manual focus adjustment is used during laser processing, then the setup is simpler, but the processing efficiency decreases and focus cannot be automatically adjusted during operation
Solution Approach 1:
The system implements a feedback loop where the height measurement device continuously monitors the height of the object being processed, and this information is fed back to automatically adjust the focus of the laser beam. This ensures the laser remains focused on the processing surface even as the object height changes, maintaining high processing efficiency without manual intervention.
Solution Approach 2:
The laser processing system performs self-adjustment of focus by using its own integrated height measurement device to detect height changes and automatically correcting the beam focus accordingly. This self-service capability eliminates the need for external manual adjustment while maintaining optimal processing conditions.
4Adaptability or versatility
If the height of the object changes during laser processing, then the object can accommodate varying thickness, but the focus of the laser light becomes misaligned with the processing target point
Solution Approach 1:
The height measurement device provides real-time feedback on object height changes during laser processing, and this information is used to dynamically adjust the laser beam focus position. This feedback mechanism ensures that even when processing objects with varying thickness or height, the laser focus remains precisely aligned with the target processing point.
Solution Approach 2:
The system transitions from static focus adjustment to dynamic focus adjustment, where the focus position changes in real-time based on measured object height variations. This dynamic adaptation allows the system to maintain manufacturing precision while processing objects with varying dimensions.
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 real-time measurement and adjustment of focus during laser processing, allowing for precise operation even with objects of varying heights, overcoming the limitations of traditional Shack-Hartmann sensors.
Implementation Method 1
a light sensing unit configured to detect a change in reflected light that is the probe light reflected from a reflective surface of the object to be processed and including a Shack-Hartmann sensor
Implementation Method 2
a first light focusing unit configured to focus the probe light and emit the focused probe light to the object to be processed
Implementation Method 3
a focus adjusting device configured to adjust a focus of the laser light emitted to the object to be processed by using the change in the height of the object to be processed measured by the measuring device
Data Source
AI summary
The laser processing device includes: a measuring device configured to measure a change in a height of an object and including a first light source configured to emit probe light, a first light focusing unit configured to focus the probe light on the object, a light sensing unit configured to detect a change in the probe light reflected from a reflective surface of the object and including a Shack-Hartmann sensor, and a calculation unit configured to calculate the change in the height of the object by using the change in the reflected light detected by the light sensing unit; a second light source configured to emit laser light for processing to the object; and a focus adjusting device configured to adjust a focus of the laser light emitted to the object by using the change in the height of the object to be processed measured by the measuring device.