Shack-Hartmann Sensor Pupil Scanning for Wide-Angle Lens Aberration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The objective lens in optical inspection apparatuses and fθ lenses in laser machining apparatuses, being infinite systems, cannot form images and require alternative wavefront aberration measurement methods, as existing Shack-Hartmann sensor techniques are limited by incident angle constraints and fail to measure rotationally symmetric aberrations effectively.
Innovation Solution
The Shack-Hartmann sensor is positioned directly at the pupil of the objective lens, reducing incident angles and allowing full pupil coverage through scanning, and aberration correction is achieved by compensating for pitching and yawing errors using laser measuring apparatuses or auto-collimators, enabling accurate measurement of wavefront aberration without relay lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Shack-Hartmann sensor is positioned directly at the pupil of the objective lens, then measurement precision is improved, but device complexity increases due to the need for scanning mechanisms and error compensation systems
Solution Approach 1:
The patent introduces a scanning mechanism as an intermediary component that enables the Shack-Hartmann sensor to scan across the pupil plane. This scanning mechanism, combined with error compensation using laser measuring apparatuses or auto-collimators, allows precise wavefront aberration measurement by systematically mapping the pupil region while compensating for mechanical errors introduced during scanning.
Solution Approach 2:
The patent employs dynamic scanning of the Shack-Hartmann sensor across the pupil plane rather than requiring a static, complex multi-sensor array. The scanning mechanism dynamically positions the sensor at different locations, and the error compensation system dynamically adjusts for positioning errors, achieving comprehensive pupil coverage with a single sensor.
2Ease of operation
If relay lenses are used in the measurement system, then ease of operation is improved, but manufacturing precision requirements increase due to additional optical components
Solution Approach 1:
The patent extracts and eliminates the relay lenses from the measurement system. By positioning the Shack-Hartmann sensor directly at the pupil plane and using a scanning mechanism, the system removes the intermediate relay lens components that would otherwise be required to image the pupil, thereby reducing manufacturing precision requirements while maintaining operational capability.
3Measurement precision
If the incident angle on the Shack-Hartmann sensor is reduced, then measurement precision is improved, but the scanning range and time increase
Solution Approach 1:
The patent applies partial scanning action by focusing the Shack-Hartmann sensor measurement on the critical pupil region with reduced incident angles, rather than uniformly scanning the entire possible field. The error compensation system enables this selective partial scanning approach, measuring only where precision is most critical while compensating for positions where full scanning would be required, thereby reducing overall scanning time.
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 wavefront aberration measurement of infinite system lenses, improving sensitivity and uniformity in optical inspection and machining processes, enhancing operational efficiency and quality in semiconductor manufacturing and laser machining.
Implementation Method 1
The Shack-Hartmann sensor is a sensor for photographing the wavefront (i.e., phase distribution) of lights entering upon the sensor, dividing and condensing that by means of an array lens, in the form of an image of alignment of plural numbers of spots, on a 2-dimensional sensor
Implementation Method 2
dividing and condensing that by means of an array lens, in the form of an image of alignment of plural numbers of spots
Implementation Method 3
aberration correction is achieved by compensating for pitching and yawing errors using laser measuring apparatuses or auto-collimators
Data Source
AI summary
Measurement cannot be made when trying to measure a wavefront aberration of a wide-angle lens, being wide in a field of view, comparing to a focus distance, by a Shack-Hartmann sensor, since an inclination of the wavefront exceeds an allowable value of inclination of the Shack-Hartmann sensor. The Shack-Hartmann sensor is inclined at a position of a pupil of a lens, and is controlled so that it lies within the allowable value mentioned above. Photographing is made through step & repeat while overlapping at the same position, to compose in such a manner that overlapping spots are piled up, and thereby measuring the wavefront aberration of the lens having a large pupil diameter.