Optical Measurement Linearity Correction via Exposure Time
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Solution Overview
Problem
Existing optical measurement systems face challenges in maintaining output linearity due to fluctuations in detector elements, requiring complex calibration processes and multiple detector types, which increases time and effort while compromising measurement accuracy.
Innovation Solution
An optical measurement method that corrects output values by determining a set of coefficients through regression analysis, using a product of a coefficient and the square of exposure time to adjust for deviations from linearity, specifically applicable to detectors with sensitivity in the near-infrared region, such as InGaAs linear image sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple detector types are used to maintain sensitivity across different wavelength regions, then measurement accuracy is improved, but device complexity and preparation time increase
Solution Approach 1:
The patent applies universality by enabling a single detector to perform multiple functions across different wavelength regions (ultraviolet, visible, and near-infrared) through wavelength-selective optical elements, eliminating the need for multiple specialized detectors while maintaining measurement accuracy across the entire spectrum
Solution Approach 2:
The patent uses wavelength-selective optical elements (such as dichroic mirrors or beam splitters) as intermediaries to direct different wavelength regions to the same detector, allowing one detector to effectively serve multiple wavelength-specific measurement functions
2Measurement precision
If linearization correction is performed using preliminarily prepared linearization data from multiple reference plates, then output linearity is improved, but the calibration process becomes complicated and time-consuming
Solution Approach 1:
The patent performs preliminary calibration by obtaining actual measurement values from a reference plate with known reflectance before measuring the target object, and uses these preliminary values to calculate correction coefficients that are then applied during actual measurement, eliminating the need for time-consuming multi-reference-plate calibration
Solution Approach 2:
The patent changes the calibration approach from using multiple reference plates with different reflectances to using a single reference plate and adjusting measurement parameters (exposure time, gain) to establish correction coefficients, thereby simplifying the calibration process while maintaining output linearity
3Measurement precision
If exposure time is increased to improve sensitivity in the near-infrared region, then detection capability is improved, but output linearity deteriorates due to detector saturation
Solution Approach 1:
The patent applies dynamics by automatically adjusting exposure time based on the measured light intensity and calculated correction coefficients, allowing the system to dynamically optimize between sensitivity and linearity for each measurement condition rather than using a fixed exposure time
Solution Approach 2:
The patent uses feedback by measuring a reference plate with known reflectance, calculating correction coefficients based on the actual measured values versus expected values, and then applying these coefficients to correct subsequent measurements, thereby maintaining output linearity even when exposure time is increased for near-infrared detection
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 simplifies the calibration process, reduces time and effort, and maintains high accuracy by ensuring output linearity across varying exposure times and light intensities, enhancing the measurement precision without the need for multiple detectors or complex reference data.
Implementation Method 1
A configuration of receiving light from a sample at a detector is used in a general optical characteristic measurement system
Data Source
AI summary
There is provided an optical measurement method using a detector having a detection sensitivity to at least a near-infrared region. The optical measurement method including: obtaining an output value by measuring a light sample at any exposure time with the detector; and correcting the output value with an amount of correction corresponding to the output value, when the exposure time at which the output value is obtained is within a second range. The amount of correction includes a product of a coefficient and a square of the exposure time, the coefficient indicating a degree to which an output value obtained when the light sample is measured with the detector at an exposure time within the second range deviates from output linearity obtained when the light sample is measured with the detector at an exposure time within a first range.