Single Mode Fiber Coupler for Optical Interference Measurement
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Solution Overview
Problem
Existing optical interference measurement apparatuses face challenges in incorporating a guide light irradiation function without increasing the size of the apparatus, as separate optical systems for measurement and guide light are difficult to align and use expensive WDM couplers, and methods like dichroic mirrors complicate the design.
Innovation Solution
An optical interference measurement apparatus that combines measurement and guide light using a single mode fiber coupler with a cutoff wavelength shorter than the measurement light and longer than the guide light, allowing for low-cost synthesis and alignment of both lights, enabling visual confirmation of the measurement position and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate irradiation optical systems are provided for measurement light and guide light, then the measurement position can be visually confirmed, but alignment of optical axes becomes difficult and the measurement head size increases
Solution Approach 1:
The patent combines the measurement light optical system and guide light optical system into a single shared irradiation optical system. The light synthesizing unit merges both light beams before they pass through the objective lens, allowing both measurement and guidance functions to be performed through the same optical path, thereby avoiding alignment issues and reducing measurement head size.
Solution Approach 2:
The light synthesizing unit acts as an intermediary device that combines measurement light and guide light. This mediator component enables both light types to be transmitted through a common optical path without requiring separate optical systems, thus resolving the contradiction between visual confirmation and compact size.
2Adaptability or versatility
If a WDM coupler is used to combine measurement light and guide light, then both lights can be multiplexed, but the cost increases and it becomes difficult to adopt
Solution Approach 1:
The patent exploits the wavelength parameter difference between measurement light (infrared) and guide light (visible) to achieve light separation and combination. By using optical filters that transmit specific wavelength ranges, the system combines both lights without requiring expensive WDM couplers, thus reducing manufacturing cost while maintaining multiplexing capability.
Solution Approach 2:
The patent replaces expensive WDM couplers with more economical optical filtering components. The light synthesizing unit uses cost-effective filters to achieve wavelength-based light combination, making the system more manufacturable and commercially viable.
3Adaptability or versatility
If a dichroic mirror is used to combine measurement light and guide light, then both lights can be synthesized, but the number of components increases and the apparatus body size increases
Solution Approach 1:
The patent merges the light synthesis function into an integrated unit that combines filtering and beam combination in a compact structure. This light synthesizing unit reduces the number of discrete components compared to traditional dichroic mirror-based systems, thereby simplifying the overall device structure while maintaining the capability to synthesize both light types.
4Ease of manufacture
If a single mode fiber coupler with appropriate cutoff wavelength is used, then measurement light and guide light can be combined at low cost, but the fiber must have specific wavelength characteristics
Solution Approach 1:
The patent specifies particular wavelength parameters for the single mode fiber coupler, selecting a cutoff wavelength that allows guide light (visible range) to pass while blocking measurement light (infrared range). This parameter-based approach enables low-cost light combination using standard single mode fibers with appropriate wavelength characteristics.
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 allows for a guide light irradiation function at a lower cost without increasing the apparatus size, enhancing measurement accuracy and robustness against temperature changes and oscillations, while minimizing chromatic aberration effects.
Implementation Method 1
a fiber coupler that includes at least a first port into which the measurement light is input, a second port into which the guide light is input, and a third port that outputs combined light formed by combining the measurement light and the guide light with each other, wherein the fiber coupler is formed by a single mode fiber that has a cutoff wavelength that is shorter than the wavelength of the measurement light and longer than the wavelength of the guide light
Implementation Method 2
a measurement unit that emits the combined light to a measurement object and receives return light that is reflected from the measurement object
Implementation Method 3
a processing unit that obtains information relating to a distance, a speed, or an oscillation the measurement object, based on an interference signal of the return light and the reference light
Data Source
AI summary
A first light source outputs measurement light having a wavelength in infrared range. A second light source outputs guide light having a wavelength in visible range. A fiber coupler includes a first port into which the measurement light is input, a second port into which the guide light is input, and a third port outputting combined light formed by combining the measurement light and the guide light with each other. A measurement unit emits the combined light to a measurement object and receives return light reflected therefrom. A processing unit obtains information relating to a distance, a speed, or an oscillation of the measurement object, based on an interference signal of the return light and the reference light. The fiber coupler is formed by a single mode fiber that has a cutoff wavelength that is shorter than that of the measurement light and longer than that of the guide light.