Optical Sensor Exposure Normalization for Signal Linearity
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Solution Overview
Problem
Signal nonlinearity in optical sensor devices due to varying bit resolutions and exposure levels affects device performance, leading to circuit cost inefficiencies and signal saturation.
Innovation Solution
Implement a processing circuit with a digital-to-analog converter (DAC) and programmable gain amplifier (PGA) to adjust driving currents and gain values dynamically, coupled with exposure adjustments to normalize digital signals, mitigating signal nonlinearity and preventing saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If different bit resolutions are used to reduce circuit costs, then circuit cost is reduced, but signal nonlinearity is introduced affecting device performance
Solution Approach 1:
The system performs a preliminary exposure adjustment operation before the actual imaging to determine the appropriate driving current level. This preliminary action allows the system to pre-calculate compensation factors that will be applied during normal operation, thereby maintaining signal linearity without requiring complex high-bit-resolution circuits throughout the entire imaging pipeline.
Solution Approach 2:
The system dynamically changes the driving current parameter based on exposure requirements and uses compensation factors to adjust the digital signals accordingly. By varying the driving current and applying corresponding normalization, the system maintains linear signal relationships across different exposure levels while using cost-effective lower-bit-resolution circuitry.
2Adaptability or versatility
If exposure adjustment operation is performed to adapt to different lighting conditions, then adaptability is improved, but signal nonlinearity and saturation occur affecting measurement precision
Solution Approach 1:
The system implements a feedback mechanism where the compensation factor calculated from the preliminary exposure adjustment operation is fed back into the signal processing pipeline. This feedback allows the system to continuously adjust and normalize signals during actual imaging, maintaining measurement precision across varying lighting conditions while preserving adaptability through exposure adjustment.
Solution Approach 2:
The exposure adjustment operation serves as a preliminary calibration step that determines the appropriate compensation factor before actual imaging. This preliminary action establishes the correct signal normalization parameters, ensuring that subsequent measurements remain accurate even as lighting conditions change and exposure adjustments are made.
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 solution effectively reduces signal nonlinearity and saturation, ensuring accurate digital signal generation by normalizing image data through compensation factors, thereby enhancing the optical sensor's performance and reducing circuit costs.
Implementation Method 1
a driver circuit generate a driving current to drive a light emission unit
Implementation Method 2
the optical sensor is coupled to the processing circuit and is arranged for receiving reflected light associated with the light emission unit to generate at least one sensed image
Data Source
AI summary
A method of an optical sensor device includes: providing an optical sensor for receiving reflected light associated with a light emission unit to generate at least one sensed image; using a first exposure setting to make the optical sensor generate a first frame data during a first frame time period of a frame; when performing an exposure adjustment operation, using a second exposure setting to make the optical sensor generate a second frame data during a second time period of the frame neighbor to the first frame time period of the frame; and, generating a normalized digital signal corresponding to the first frame data based on the relation between the first frame data and the second frame data.