Optical Sensor Calibration Current for Precise Light Sensing
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Solution Overview
Problem
Existing optical sensors consume a large area and high power due to the use of band-gap voltage references for accurate brightness measurement.
Innovation Solution
An optical sensor arrangement that includes a light sensor, a current source, and an analog-to-digital converter (AD converter) with a switch to selectively couple either the light sensor or the current source to the AD converter, eliminating the need for a band-gap voltage reference by using a calibration current for precise measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a band-gap voltage reference is used for accurate brightness measurement, then measurement precision is improved, but area consumption and power consumption increase
Solution Approach 1:
The patent extracts and removes the band-gap voltage reference from the optical sensor system. Instead of using a traditional voltage reference, the invention uses a current source that can be calibrated to provide reference current, thereby eliminating the area-consuming band-gap circuit while maintaining measurement accuracy through alternative calibration methods
Solution Approach 2:
The patent changes the reference parameter from voltage (band-gap voltage reference) to current (calibrated current source). This parameter transformation allows the system to maintain precision while reducing area consumption, as the current source can be implemented more compactly and calibrated through software or lookup tables stored in memory
2Measurement precision
If a band-gap voltage reference is used for accurate brightness measurement, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent removes the power-hungry band-gap voltage reference circuit and replaces it with a more energy-efficient current source implementation. The current source can be calibrated using stored reference values in memory, eliminating the need for continuous operation of complex voltage reference circuits while maintaining measurement precision
Solution Approach 2:
The patent performs calibration in advance and stores reference current values in memory. During normal operation, the system retrieves pre-calibrated values rather than continuously maintaining a complex voltage reference, thereby reducing power consumption while preserving measurement accuracy through previously established calibration data
3Area of stationary object
If a calibration current source is used instead of band-gap voltage reference, then area consumption is reduced, but measurement precision may be affected
Solution Approach 1:
The patent implements calibration mechanisms where the current source is adjusted based on feedback from measured values. By comparing actual measurements against stored reference data and adjusting the current source accordingly, the system compensates for variations and maintains precision despite the simplified hardware architecture
Solution Approach 2:
The patent uses stored reference current values in memory as copies of ideal calibration data. These stored values represent pre-characterized reference points that allow the system to maintain accuracy without requiring the physical presence of complex voltage reference circuits during normal operation
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 solution reduces power consumption and area on the integrated circuit while maintaining precise brightness measurement, enabling efficient ambient light sensing and dynamic display management.
Implementation Method 1
a light sensor (11)
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An optical sensor arrangement (10) comprises a light sensor (11), a current source (41), an analog-to-digital converter (12) and a switch (44) which selectively couples the light sensor (11) or the current source (41) to an input (14) of the analog-to-digital converter (12).