Optical Height Measurement Device with Variable Incidence Angles
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Solution Overview
Problem
Existing height measurement devices face challenges in accurately measuring sample height variations, particularly when large differences exist between the reference height and the sample surface, due to limited detection surface sizes and inclined light radiation, which can result in inaccurate focus adjustments and measurement errors.
Innovation Solution
An optical height measurement device is designed with a stage, stage driving unit, projection optical system, detection optical system, and processing unit, featuring an optical path dividing element and adjusting element to ensure accurate height measurement across varying sample heights by branching and adjusting the optical path to accommodate different incidence angles, allowing for high-accuracy measurements even with significant height variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If light is radiated from an inclined direction to measure sample height, then height measurement capability is provided, but measurement accuracy deteriorates when large height differences exist between reference height and sample surface
Solution Approach 1:
The projection optical system is divided into multiple independent illumination units, each capable of projecting light at different incidence angles onto the sample surface. This segmentation allows the system to handle different height ranges effectively, as each unit can be optimized for specific measurement conditions without being constrained by a single fixed angle.
Solution Approach 2:
The system dynamically selects and switches between different illumination units based on the detected height range. By making the illumination configuration changeable rather than fixed, the system adapts to varying sample heights, maintaining measurement accuracy across different conditions while preserving the capability to measure diverse height variations.
2Device complexity
If a fixed detection surface size is used, then device complexity is reduced, but the measurable height range is limited
Solution Approach 1:
Instead of increasing the detection surface area in two dimensions, the system extends the measurable height range by utilizing the third dimension - the incidence angle. By projecting light at different angles through multiple illumination units, the system effectively expands its measurement capability without requiring a larger detection surface, thus maintaining simple device structure while achieving broader adaptability.
Solution Approach 2:
The system changes the illumination parameter (incidence angle) to expand the measurable height range. By varying this parameter across multiple illumination units rather than changing the detection surface size, the system achieves extended measurement capability while keeping the detection surface compact and the overall device complexity low.
3Adaptability or versatility
If inclined light projection is used for height measurement, then height detection is enabled, but focus adjustment accuracy deteriorates due to position deviation
Solution Approach 1:
The projection optical system is segmented into multiple illumination units with different incidence angles. This segmentation allows the system to select the most appropriate illumination angle for the current measurement condition, ensuring that the light spot remains accurately positioned on the sample surface even when height variations occur, thereby maintaining focus adjustment accuracy.
Solution Approach 2:
The system dynamically adjusts which illumination unit is active based on the detected height, ensuring optimal positioning of the light spot. This dynamic adaptation prevents position deviation and maintains accurate focus adjustment across different height conditions while preserving height detection capability.
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
The device enables precise height measurement at each height with high accuracy, broadening the measurable range while maintaining high imaging magnification, effectively addressing the limitations of existing technologies by ensuring accurate focus adjustments and improved detection accuracy.
Implementation Method 1
a detection optical system for receiving reflected light from the sample
Implementation Method 2
an optical path dividing element for branching the optical path of the light emitted from the light source
Data Source
AI summary
The purpose of the present invention is to provide a height measurement device with which, even when the height of a sample surface varies considerably, it is possible, with a relatively simple configuration, to perform height measurement with high accuracy at various heights. In order to achieve the abovementioned purpose, proposed is an optical height measurement device characterized by being provided with: a stage for retaining a sample; a stage driving unit for adjusting the stage at different heights; a projection optical system for projecting light onto the sample; a detection optical system for receiving light reflected from the sample; and a processing unit for measuring the height of the sample on the basis of a signal outputted from the detection optical system, wherein the projection optical system is provided with a light source that emits light, and an optical path dividing element for branching the optical path of the light emitted from the light source, and the detection optical system is provided with a sensor for receiving light reflected from the sample, and an element for adjusting the light path of the light reflected from the sample in the direction of the sensor prior to reception of the light by the sensor.