Rectangular Slit Level Detection for Optical Precision
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Solution Overview
Problem
Conventional level detection methods using circular pin holes are prone to errors due to insufficient light, reflectance distribution, and diffracted light issues, especially when pin hole positions are misaligned, leading to inaccurate light detection and level measurement.
Innovation Solution
A level detection apparatus employing rectangular illumination and detection slits, where the short side of the slit openings is shorter than the illumination slit image and the long side is longer, to ensure equal light passage in front of and behind the focal point, reducing errors caused by reflectance and diffracted light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If circular pin holes are used for light regulation, then light amounts can be detected, but detection precision deteriorates due to reflectance distribution and diffracted light errors when pin hole positions are misaligned
Solution Approach 1:
The patent divides the light regulation function into multiple independent rectangular slits (first detection slit and second detection slit) positioned at different locations, replacing the single circular pin hole system. Each slit independently regulates light from specific regions, allowing the system to maintain accurate light amount detection even when individual slit positions vary, thereby resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The patent applies different rectangular slit configurations to different detection regions (front of focal point and back of focal point), with each slit having specific dimensional characteristics optimized for its location. The first detection slit has dimensions adapted for front focal point detection while the second detection slit is optimized for back focal point detection, enabling accurate local light measurement despite position variations.
2Measurement precision
If circular pin holes are positioned to completely coincide optically, then detection accuracy improves, but device complexity increases due to difficult alignment
Solution Approach 1:
The patent separates the optical path into distinct front and back focal point regions with independent rectangular slits. This segmentation allows each slit to be independently positioned and optimized for its specific region, eliminating the need for precise coincidence alignment between two circular pin holes while maintaining accurate light amount detection through the sum of light from both slits.
3Measurement precision
If rectangular slits with specific dimensions are used, then light amount consistency improves regardless of position, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise dimensional parameters for the rectangular slits (first detection slit: 1.0-3.0 μm × 10.0-30.0 μm, second detection slit: 1.0-3.0 μm × 10.0-30.0 μm) to optimize light regulation. These parameter specifications ensure that the slits maintain consistent light transmission characteristics across different positions while providing sufficient manufacturing tolerance, balancing measurement precision with manufacturing feasibility.
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 configuration ensures accurate and linear level detection by maintaining consistent light amounts regardless of slit position misalignment, thereby reducing errors and improving detection precision.
Implementation Method 1
focuses reflected light from the target object surface
Implementation Method 2
optical system configured to illuminate a target object surface by illumination light passing through the illumination slit and focuses reflected light from the target object surface
Implementation Method 3
first and second light amount sensors configured to detect amounts of light of the reflected lights passing through the first and second detection slits
Data Source
AI summary
A level detection apparatus includes an illumination slit in which a rectangular first opening which causes illumination light to pass is formed, an optical system configured to illuminate a target object surface by illumination light passing through the illumination slit and focuses reflected light from the target object surface, first and second detection slits which are arranged in front of and in back of a focal point and in each of which a second opening is formed such that a short side of a rectangle is shorter than a short side of a illumination slit image formed by the illumination slit and a long side of the rectangle is larger than a long side of the illumination slit image, first and second light amount sensors configured to detect amounts of light of the reflected lights passing through the first and second detection slits, and a calculating unit configured to calculate a level of the target object surface based on outputs from the first and second light amount sensors.