Optical Measurement System Calibration With Temperature-Power Feedback
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Solution Overview
Problem
The relationship between input current and output optical power level in optical measurement devices is affected by light source characteristics such as temperature, leading to inconsistent measurements.
Innovation Solution
An optical measurement system that includes a driver circuit to adjust input current based on temperature and optical power level measurements, using a temperature sensor and optical sensor to maintain consistent output power, thereby stabilizing measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the input current to the light source is increased to improve measurement signal strength, then the optical power level increases, but the temperature of the light source increases causing measurement inconsistency
Solution Approach 1:
The patent implements a feedback mechanism where a temperature sensor continuously monitors the light source temperature and an optical sensor monitors the optical power level. The driver circuit receives both temperature and power signals, and dynamically adjusts the input current to maintain consistent optical power output despite temperature variations. This closed-loop feedback system resolves the contradiction by automatically compensating for thermal effects that would otherwise cause measurement inconsistency.
Solution Approach 2:
The patent changes the operating parameters of the light source by adjusting the input current based on real-time temperature and power measurements. The driver circuit modifies the electrical parameters (current level) in response to temperature changes, thereby maintaining stable optical output parameters. This dynamic parameter adjustment allows the system to operate at higher power levels without suffering from temperature-induced inconsistency.
2Measurement precision
If temperature compensation is implemented to improve measurement consistency, then measurement precision improves, but device complexity increases due to additional sensors and control circuits
Solution Approach 1:
The patent achieves measurement consistency by making the driver circuit multi-functional: it not only drives the light source but also receives and processes temperature and power feedback signals. The temperature sensor and optical sensor are integrated into the existing measurement system architecture, allowing them to serve dual purposes - monitoring system state and enabling compensation. This multi-functionality approach improves measurement precision while minimizing the increase in device complexity.
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 approach ensures consistent and accurate optical measurement metrics, allowing for more precise determination of mental states and physiological parameters by compensating for thermal variance.
Implementation Method 1
a temperature sensor configured to output a temperature signal representative of a temperature of the light source
Implementation Method 2
an optical sensor configured to output a power signal representative of an optical power level of the light emitted by the light source
Implementation Method 3
An optical measurement device may detect blood oxygenation levels and/or blood volume levels by measuring the change in shape of laser pulses after they have passed through target tissue
Data Source
AI summary
An illustrative optical measurement system includes a light source configured to emit light directed at a target. The system further includes a detector configured to detect arrival times for photons of the light after the light is scattered by the target. The system further includes a temperature sensor configured to output a temperature signal representative of a temperature of the light source. The system further includes an optical sensor configured to output a power signal representative of an optical power level of the light emitted by the light source. The system further includes a driver circuit configured to output, based on the temperature signal and the power signal, an input current for the light source.