Optical Measurement Device Calibration via Reflected Pattern Analysis
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Solution Overview
Problem
Conventional methods for calibrating optical measurement devices do not ensure that the optical axis of the imaging lens group is parallel to the normal direction of the stage, leading to measurement errors, especially at the micron level where high accuracy is required.
Innovation Solution
A calibration method and device that use an object with opposing patterns to reflect light, calculating the tilted angle between the optical axis and the stage's normal direction based on the separation of reflected patterns on an image sensor, and adjusting the stage to align the optical axis with the normal direction, considering factors like object thickness and refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional stage leveling method is used, then stage can be made parallel to ground, but optical axis of imaging lens group cannot be ensured to be parallel to normal direction of stage
Solution Approach 1:
The patent introduces a calibration object with specific patterns as an intermediary element between the stage and imaging lens group. This calibration object serves as a mediator to establish the spatial relationship and alignment between the stage normal direction and the optical axis, enabling precise calibration without direct measurement of the optical axis itself.
Solution Approach 2:
The patent replaces the conventional mechanical leveling method (using level and adjustment screws) with an optical-based calibration method. Instead of relying on gravitational reference and mechanical adjustment, the system uses light reflection patterns and image processing to determine and correct the alignment between the stage and imaging lens group.
2Measurement precision
If high measurement accuracy is required for micron-level measurements, then position calibration is necessary, but conventional methods do not provide sufficient precision
Solution Approach 1:
The patent creates optical copies (reflected light patterns) of the calibration object's surface patterns and observes them through the imaging lens group. By analyzing the positions and orientations of these reflected pattern copies on the image sensor, the system can indirectly measure the alignment between the stage normal direction and the optical axis with high precision.
Solution Approach 2:
The patent changes the observation parameters by measuring the positions of reflected light patterns on the image sensor rather than directly measuring the optical axis or stage orientation. This parameter transformation converts a difficult-to-measure geometric relationship into easily measurable image coordinates, enabling precise calibration.
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 approach improves measurement accuracy by ensuring the optical axis is parallel to the stage's normal direction, enhancing precision in micron-level measurements.
Implementation Method 1
reflecting the incident light to the object on the stage by the beam splitter
Implementation Method 2
receiving the first light and the second light by an imaging lens group to obtain a third pattern corresponding to the first pattern and a fourth pattern corresponding to the second pattern
Data Source
AI summary
A method includes: transmitting an incident light to an object located on a stage, in which a first light and a second light are reflected; receiving the first light and the second light by an imaging lens group to obtain a third pattern corresponding to the first pattern and a fourth pattern corresponding to the second pattern; transmitting the third pattern and the fourth pattern to an image sensor, in which a center point of the third pattern and a center point of the fourth pattern are separated by a first distance on the image sensor; calculating a tilted angle between an optical axis of the imaging lens group and a normal direction of the stage according to the first distance; and adjusting the stage according to the tilted angle such that the normal direction is parallel to the optical axis.