Optical Path Length Control for Flowing Sample Measurement
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Solution Overview
Problem
Existing optical property measurement apparatuses using optical interference face challenges in maintaining constant measurement sensitivity due to variations in optical path lengths caused by environmental changes and the movement of sample particles in a flow passage, leading to noise and deteriorated measurement sensitivity.
Innovation Solution
An optical property measurement apparatus that includes a light source, optical couplers, a phase modulation unit, and an optical path length difference adjustment unit, which uses synchronization detection to control the optical path length difference and maintain constant sensitivity by adjusting the optical path lengths using a control unit, ensuring consistent measurement even when sample particles move one by one.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If optical fiber is used in branched light paths, then the apparatus can be compact and flexible, but the optical path length varies due to thermal expansion causing measurement noise
Solution Approach 1:
The patent introduces a feedback control system where the optical path length difference is continuously monitored and adjusted. A control unit receives signals about the optical path length difference and automatically adjusts the optical paths to maintain a constant difference, thereby compensating for thermal expansion effects in real-time and maintaining measurement precision.
Solution Approach 2:
The patent actively changes the optical path length parameters to compensate for environmental variations. By adjusting the optical path lengths dynamically in response to temperature changes, the system maintains a constant optical path length difference, thereby resolving the contradiction between using flexible optical fibers and maintaining measurement precision.
2Measurement precision
If optical path length difference is maintained constant, then measurement sensitivity is maximized, but the system requires complex control mechanisms
Solution Approach 1:
The control mechanism uses a feedback loop where the optical path length difference is continuously monitored and automatically adjusted. This feedback-based approach simplifies the control strategy by using automatic regulation rather than complex manual control, maintaining measurement sensitivity while managing system complexity through intelligent control.
Solution Approach 2:
The system performs self-adjustment of the optical path lengths through automatic control. The control unit autonomously monitors and corrects optical path length variations without requiring external intervention, thereby maintaining measurement sensitivity while minimizing the need for complex external control mechanisms.
3Quantity of substance
If sample particles move one by one through the flow passage, then individual particle measurement is enabled, but optical path length difference varies causing sensitivity fluctuations
Solution Approach 1:
The feedback control system continuously monitors the optical path length difference and automatically adjusts the optical paths to maintain constant difference, even when sample particles are moving through the flow passage. This real-time compensation ensures measurement sensitivity remains constant during individual particle measurements.
Solution Approach 2:
The system performs preliminary adjustment of the optical path lengths to establish a constant optical path length difference before measurements begin. This pre-adjustment ensures that the measurement system is optimized and ready to maintain constant sensitivity throughout the measurement process, even as particles move through the system.
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 apparatus effectively measures optical properties with constant sensitivity by controlling the optical path length difference, reducing noise and maintaining high measurement sensitivity despite environmental changes and particle movement.
Implementation Method 1
measuring an optical property of a sample flowing in a flow passage by use of optical interference
Implementation Method 2
causing the first branched light and the second branched light thus input to interfere by a second optical coupler to detect intensity of the interfering light
Implementation Method 3
a phase modulation unit provided on the first branched light path or the second branched light path between the first optical coupler and the second optical coupler for carrying out phase modulation of the light, which is propagated on the light path, with a frequency f
Data Source
AI summary
An optical property measurement apparatus includes a light source unit, a first optical coupler, a second optical coupler, a lens, a lens, a phase modulation unit, a drive unit, an optical path length difference adjustment unit, a control unit, a light receiving unit, a synchronization detection unit, and a measurement unit. The phase modulation unit carries out phase modulation with a frequency f. The synchronization detection unit outputs a first signal having a value corresponding to a magnitude of a component of the frequency f included in an electrical signal output from the light receiving unit, and also outputs a second signal having a value corresponding to a magnitude of a component of the frequency 2f included in the electrical signal. The control unit controls the optical path length difference adjusted by the optical path length difference adjustment unit to be a predetermined value based on the first signal or the second signal output from the synchronization detection unit.