Optical Sensor Dual-Shutter Pixels for Low-Power Motion Detection
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Solution Overview
Problem
Conventional optical sensor devices suffer from degraded performance due to varying shot noise levels under different light conditions, leading to false motion detection and high power consumption.
Innovation Solution
An optical sensor device with BJT sensing pixels that captures and stores image signals during alternating shutter exposure time intervals, using integration capacitors and control circuits to determine motion based on signal differences, and dynamically adjusts shutter exposure times to enhance sensitivity and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical sensor devices are used, then motion detection can be performed, but false motion detection occurs due to shot noise and power consumption is high
Solution Approach 1:
The patent implements periodic dual-mode shutter exposure cycles that alternate between first and second shutter exposure time intervals. This periodic action allows the sensor to capture images at different exposure times sequentially, enabling motion detection while reducing the impact of shot noise. The cyclic switching between exposure modes optimizes both detection accuracy and power consumption by not requiring continuous operation at maximum exposure.
Solution Approach 2:
The patent dynamically changes the shutter exposure time parameter by switching between a first shutter exposure time interval and a second shutter exposure time interval. This parameter variation allows the system to adapt to different lighting conditions and reduce shot noise impact. By adjusting the exposure time parameter periodically, the system improves motion detection reliability while managing power consumption effectively.
2Measurement precision
If conventional optical sensor devices are used, then motion detection can be performed, but detection precision is degraded due to varying shot noise levels under different light conditions
Solution Approach 1:
The patent employs periodic dual-mode shutter exposure that alternates between different exposure time intervals. This periodic action captures images under varying exposure conditions, allowing the system to distinguish between actual motion and shot noise artifacts. By periodically switching exposure modes, the system improves measurement precision while mitigating the harmful effects of shot noise.
Solution Approach 2:
The patent changes the shutter exposure time parameter between two distinct values (first and second shutter exposure time intervals). This parameter change strategy enables the system to capture images with different noise characteristics, improving motion detection precision by allowing comparison and differentiation between real motion signals and shot noise variations.
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
Accurately detects motion while consuming lower power by dynamically adjusting shutter exposure times and threshold voltages to mitigate shot noise, improving signal sensitivity and reducing false motion detection.
Implementation Method 1
The photo transistor is configured to capture and generate a first image signal during a first shutter exposure time interval of a first time and to capture and generate a second image signal during a second shutter exposure time interval of a second time
Data Source
AI summary
An optical sensor device includes a pixel array and a control circuit. The pixel array has pixel units arranged in N rows and M columns, and a pixel unit comprises: a photo transistor, configured to capture and generate a first image signal during a first shutter exposure time interval of a first time and to capture and generate a second image signal during a second shutter exposure time interval of a second time, the first time and the second time being consecutive; a first integration capacitor, coupled to the photo transistor, for storing the first image signal; and a second integration capacitor, coupled to the photo transistor, for storing the second image signal. The control circuit performs a motion detection to determine whether a motion occurs according to a difference between the two image signals.