Endoscope Imaging Device Thermal Expansion Mismatch
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Solution Overview
Problem
The existing endoscope imaging devices suffer from distortion in the optical element due to a difference in thermal expansion coefficients between the airtight packaging and the optical element, leading to compromised image quality during high-temperature sterilization processes.
Innovation Solution
The imaging device incorporates a first frame body with a metal part brazed on both inner and outer peripheral surfaces, and a second frame body with a metal part brazed on its inner surface, where the coefficient of thermal expansion of the first frame body is closer to that of the optical element than the second frame body, reducing distortion by minimizing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brazing is performed to seal the optical element to the airtight packaging, then airtight sealing is achieved, but distortion is caused in the optical element due to difference in thermal expansion coefficients
Solution Approach 1:
A first frame body made of metal with a coefficient of thermal expansion closer to that of the optical element is introduced as an intermediary component between the optical element and the airtight packaging. This intermediary frame body absorbs thermal expansion differences during brazing, reducing distortion of the optical element while maintaining airtight sealing.
Solution Approach 2:
The structure is segmented into three distinct components: the airtight packaging, the first frame body (intermediary), and the optical element. This segmentation allows each component to have optimized material properties, particularly the first frame body whose thermal expansion coefficient is specifically selected to match the optical element, thereby isolating the optical element from thermal stress.
2Device complexity
If a single frame body is used to hold the optical element, then device complexity is reduced, but insufficient distortion reduction occurs during high-temperature sterilization
Solution Approach 1:
The frame body is divided into two separate components: a first frame body that directly contacts and holds the optical element, and a second frame body that provides structural support and connects to the airtight packaging. The first frame body is specifically designed with material properties matching the optical element to minimize thermal expansion mismatch, while the second frame body provides mechanical strength.
Solution Approach 2:
Different parts of the frame structure have different material properties optimized for their specific functions. The first frame body uses a material with thermal expansion coefficient matched to the optical element for thermal compatibility, while the second frame body uses a material optimized for mechanical strength and structural support.
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 effectively reduces distortion in the optical element, maintaining image quality even after high-temperature sterilization, particularly when the number of effective pixels reaches 4K resolution or higher.
Implementation Method 1
an opening at one end of the airtight packaging 101 is sealed by the optical element 102... fixed to the recessed part 1011 by brazing (soldering) using solder SD... outer peripheral surface of the optical element, and the inner peripheral surface of the first frame body are brazed together; and the outer peripheral surface of the first frame body and the inner peripheral surface of the second frame body are brazed together
Implementation Method 2
there is a difference in a coefficient of thermal expansion between the airtight packaging 101 and the optical element 102. Thus, when brazing is performed (FIG. 9A) in a high temperature environment of approximately 300° C. and the temperature is returned to the ordinary temperature, distortion is caused in the optical element 102 due to the difference in the coefficient of thermal expansion between the members 101 and 102
Data Source
AI summary
An imaging device includes: an optical element including a metal layer adapted to be brazed and arranged on an outer peripheral surface of the optical element; a first frame body including a metal part adapted to be brazed and arranged at least on an inner peripheral surface and an outer peripheral surface of the first frame body, the inner peripheral surface being brazed onto the outer peripheral surface of the optical element; and a second frame body including a metal part adapted to be brazed and arranged at least on an inner peripheral surface of the second frame body, the inner peripheral surface being brazed onto the outer peripheral surface of the first frame body. A coefficient of thermal expansion of the first frame body is closer to a coefficient of thermal expansion of the optical element than a coefficient of thermal expansion of the second frame body.