Aspheric Lens Shape Measurement Error Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current shape measurement techniques for aspheric optical elements with wide angles require significant time for alignment, reducing measurement accuracy due to changes in optical path and aberration, especially when introducing stitching measurement techniques into Shack-Hartmann sensor systems.
Innovation Solution
A shape measuring method that controls a rotary stage to specific measurement positions to estimate and correct placement errors, allowing for efficient alignment of partial regions without repeated measurements, using a Shack-Hartmann sensor and a system that includes a light source, lenses, and a stage apparatus to drive the object lens in six axial directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If stitching measurement technique is introduced to measure wide-angle aspheric optical elements, then the measurable field of view is improved, but the alignment time and complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between rotary stage positions and placement errors in a lookup table before actual measurement. This allows the system to quickly retrieve and correct placement errors during stitching measurement without performing real-time complex calculations or repeated alignment operations, thus reducing alignment time while maintaining the ability to measure wide-angle optical elements.
Solution Approach 2:
The patent establishes the placement error characteristics and creates correction data in advance through preliminary measurements and calculations. By pre-processing the error information and storing it for quick access, the system eliminates the need for time-consuming repeated alignment operations during actual stitching measurement, resolving the contradiction between expanded measurement area and increased alignment time.
2Measurement precision
If repeated measurements are performed to ensure alignment accuracy, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent creates a copied model of the placement error characteristics through preliminary measurements and stores this error information in a lookup table. During actual measurement, the system retrieves the pre-copied error data corresponding to each rotary stage position and applies correction, eliminating the need for repeated measurements while maintaining high alignment accuracy. This copying approach resolves the contradiction between precision and time by using pre-acquired error information instead of repeated verification measurements.
3Productivity
If placement errors are not corrected in stitching measurement, then measurement speed is improved, but measurement precision deteriorates
Solution Approach 1:
The patent implements feedback by measuring placement errors at different rotary stage positions, storing this error information in a lookup table, and then retrieving and applying the corresponding error corrections during stitching measurement. This feedback mechanism ensures that placement errors are compensated without requiring repeated measurements or slowing down the measurement process, thus maintaining both high measurement speed and high shape measurement accuracy.
Solution Approach 2:
The patent performs preliminary measurement and characterization of placement errors, storing the results in advance for quick retrieval. This preliminary action creates a correction database that enables fast error compensation during actual stitching measurement, resolving the contradiction between measurement speed and precision by preparing correction data beforehand rather than performing real-time error analysis that would slow down the process.
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 reduces the time required for alignment while maintaining accuracy by estimating placement errors at key positions and correcting them, enabling faster and precise shape measurement of aspheric optical elements.
Implementation Method 1
light of spherical waves is irradiated onto a reference surface of a reference lens... Reflected light from the reference surface is imaged with an imaging lens
Implementation Method 2
A wavefront of the reflected light that is imaged is measured by the Shack-Hartmann sensor. As is known, a Shack-Hartmann sensor is a wavefront sensor that includes an imaging device and a microlens array
Implementation Method 3
a Shack-Hartmann sensor is a wavefront sensor that includes an imaging device and a microlens array
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
A rotary stage is controlled to two measurement positions along a rotational direction in which an object surface is moved when detecting a wavefront of reflected light from partial regions by a detecting unit, to move the object surface. Respective placement errors in a trajectory of the object surface at the two measurement positions are measured based on wavefronts detected by the detecting unit in states in which the rotary stage is controlled to each of the two measurement positions. For the remaining measurement positions among the measurement positions, respective placement errors with respect to the trajectory of the object surface are estimated based on the placement errors measured. Before measurement of each item of partial shape data, the rotary stage is controlled to a measurement position and stages are controlled to a position that cancels a placement error at the measurement position to align the object surface.