Sensor Circuit Illuminance Measurement Spectral Switching
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Solution Overview
Problem
Conventional illuminance sensors experience uneven light irradiation of photodiodes due to fixed positions and potential lens misalignment, leading to uneven outputs and variations in sensitivity, which affect accurate measurement of visible light illuminance.
Innovation Solution
A sensor circuit with multiple light receiving elements, each set to different spectral characteristics, which are sequentially switched during measurement to ensure even irradiation and consistent results, regardless of light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple photodiodes with different spectral characteristics are used to achieve visual sensitivity, then spectral characteristic accuracy is improved, but device complexity increases due to current mirror circuits and multiple photodiodes
Solution Approach 1:
The patent combines multiple photodiodes with different spectral characteristics into a single integrated light receiving element. This light receiving element includes a first photodiode and a second photodiode with different spectral characteristics, merging their functions into one component. The combining reduces device complexity by eliminating the need for separate current mirror circuits while maintaining the capability to achieve visual sensitivity through spectral subtraction.
Solution Approach 2:
The integrated light receiving element serves multiple functions: it detects both visible light and infrared light simultaneously using its multiple photodiodes, and performs spectral subtraction internally to achieve visual sensitivity. This multi-functional design eliminates the need for separate detection and processing circuits, reducing overall device complexity while maintaining measurement precision.
2Ease of manufacture
If photodiodes are positioned at fixed locations to simplify device structure, then ease of manufacture is improved, but measurement precision deteriorates due to uneven light irradiation and lens misalignment
Solution Approach 1:
The patent introduces a light distribution control unit that dynamically adjusts the light distribution to each photodiode based on detection conditions. Instead of relying on fixed photodiode positions, the system dynamically compensates for uneven light irradiation by controlling the light distribution, thereby maintaining measurement precision while allowing for simpler fixed positioning of photodiodes.
Solution Approach 2:
The light distribution control unit operates based on feedback from the detection unit, which monitors the actual light reception status of each photodiode. This feedback mechanism allows the system to detect and correct uneven light irradiation caused by lens misalignment or positioning variations, maintaining measurement accuracy without requiring complex precision positioning mechanisms.
3Measurement precision
If light receiving elements are sequentially switched among different spectral characteristics, then measurement precision is improved by ensuring even irradiation, but measurement time increases due to sequential switching
Solution Approach 1:
The patent enables simultaneous operation of multiple photodiodes with different spectral characteristics within the integrated light receiving element. Both the first photodiode and second photodiode detect light concurrently, and the spectral subtraction is performed simultaneously, eliminating the need for sequential switching. This continuous simultaneous operation maintains measurement precision while significantly reducing measurement time.
Solution Approach 2:
The integrated light receiving element is pre-configured with multiple photodiodes having different spectral characteristics, and the light distribution control unit is pre-programmed with the optimal light distribution pattern. This preliminary configuration allows the system to perform spectral subtraction immediately upon light reception without requiring sequential switching or time-consuming adjustments, thereby reducing measurement time while maintaining precision.
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 allows for accurate measurement of illuminance without unevenness in spectral characteristics and sensitivity variations, even when light receiving elements are unevenly irradiated, ensuring reliable detection of visible light illuminance.
Implementation Method 1
a first photodiode PD1 having a first spectral characteristic and a second photodiode PD2 having a second spectral characteristic different from the first spectral characteristic
Data Source
AI summary
A sensor circuit which is capable of measuring illuminance without causing unevenness in results detected with spectral characteristics and a variation in sensitivity regardless of whether or not light receiving elements are evenly irradiated with light includes a plurality of light receiving elements, the light receiving elements each being set to a single spectral characteristic selected from spectral characteristics that are different from each other, and the single spectral characteristic set in each of the light receiving elements being sequentially switched among the spectral characteristics that are different from each other so that the light receiving elements are set to different spectral characteristics during measurement of the illuminance.