Single Crystal Melt Level Measurement Using Oblique Camera Reflection
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Solution Overview
Problem
Existing single crystal manufacturing methods, particularly the Czochralski method, face challenges in stably measuring the liquid surface level of the melt due to obstruction by furnace interior structures such as the purge tube and water cooling body, which block the view of cameras used for measurement.
Innovation Solution
A manufacturing method that involves positioning a heat shielding body above the crucible, capturing real and mirror images of the heat shielding body using a camera with an oblique optical axis, and calculating the gap value between the heat shielding body and the melt surface using a detection line that intersects both image edges, allowing for accurate measurement of the liquid surface level regardless of internal furnace structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera is positioned to capture the entire single crystal in the diameter direction with the optical axis in the same plane as the pulling-up axis, then the crystal diameter can be measured, but the view is blocked by furnace interior structures such as the purge tube and water cooling body, preventing measurement of the liquid surface level
Solution Approach 1:
The patent introduces a new spatial dimension by positioning the camera's optical axis at an angle (e.g., 45 degrees) relative to the pulling-up axis, rather than in the same plane. This dimensional change allows the camera to capture both the heat shielding body and its mirror image reflected on the melt surface simultaneously, enabling liquid surface level measurement without interference from furnace interior structures that block the conventional measurement path
2Reliability
If furnace interior structures such as the purge tube and water cooling body are installed above the heat shielding body to control the crystal growth environment, then crystal quality is improved, but these structures block the camera view and prevent accurate measurement of the liquid surface level
Solution Approach 1:
By changing the camera's viewing angle to an oblique orientation relative to the pulling-up axis, the measurement path is shifted to a different spatial dimension that bypasses the blocking furnace interior structures. This allows simultaneous capture of the heat shielding body and its mirror image on the melt surface, enabling precise liquid surface level measurement while maintaining the necessary furnace interior structures for crystal quality control
Solution Approach 2:
The patent uses the mirror image of the heat shielding body reflected on the melt surface as an intermediary measurement target. Instead of directly measuring the distance to the melt surface, the system measures the distance to the mirror image, which provides indirect but accurate information about the liquid surface level without requiring direct line of sight to the melt surface itself
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 enables stable measurement of the liquid surface level, improving the precision and reliability of single crystal growth by overcoming obstructions caused by furnace interior structures.
Implementation Method 1
capturing with a first camera a real image of the heat shielding body and a mirror image of the heat shielding body reflected on a melt surface
Data Source
AI summary
A manufacturing method of a single crystal includes providing a heat shield to cover an area above a crucible except for a pulling-up path of the single crystal; capturing with a first camera a real image of the heat shield and a mirror image of the heat shield reflected on a melt surface; setting a detection line extending in an oblique direction that is neither parallel nor perpendicular to a pulling-up axis of the single crystal and intersects both a real image edge and a mirror image edge of the heat shield; and finding a gap value, which is a distance between a lower end of the heat shield and the melt surface based on a distance on the detection line, between the real image and the mirror image.