Optical Sensor Dual Photodiode Dynamic Range
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Solution Overview
Problem
Current optical sensors and solid-state imaging devices have a limited dynamic range, particularly on the low illumination side, which hinders their effectiveness in various applications requiring broad optical wavelength compatibility and high sensitivity across different light intensity ranges.
Innovation Solution
The development of an optical sensor incorporating a light-receiving element, storage capacitors, and a transfer switch, featuring a floating diffusion capacitor and a lateral overflow integration capacitor, along with a non-LDD/MOS transistor with reduced impurity concentration in the drain region, enables wide dynamic range performance from single-photon to high illumination levels, combined with high sensitivity and broad optical wavelength compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional optical sensors are used, then manufacturing simplicity is maintained, but the dynamic range on the low illumination side remains limited
Solution Approach 1:
The optical sensor divides the dynamic range into two segments: a first dynamic range handled by a first photodiode and a second dynamic range handled by a second photodiode. This segmentation allows each photodiode to be optimized for specific illumination levels, thereby expanding the overall dynamic range without significantly increasing device complexity
Solution Approach 2:
The patent implements dynamic switching between different photodiodes based on illumination conditions. A switching mechanism dynamically selects which photodiode to use, allowing the sensor to adapt to varying light levels and maintain optimal performance across the extended dynamic range
2Illumination intensity
If the dynamic range is widened to high illumination levels, then high light detection capability is improved, but sensitivity in the low light intensity range deteriorates
Solution Approach 1:
Each photodiode is designed with different characteristics optimized for its specific operating range. The first photodiode has characteristics optimized for low light sensitivity, while the second photodiode is optimized for high illumination handling. This local quality optimization ensures that each component performs excellently in its designated range without compromising the other
Solution Approach 2:
The switching mechanism dynamically selects the appropriate photodiode based on current illumination conditions, ensuring that the sensor always uses the photodiode with optimal characteristics for the current light level, thereby maintaining both high light detection capability and low light sensitivity
3Measurement precision
If single-photon detection capability is achieved, then sensitivity is improved, but saturation performance at high illumination levels deteriorates
Solution Approach 1:
The sensor segments the detection task between two photodiodes: the first photodiode is designed with high sensitivity for single-photon detection, while the second photodiode is designed with higher saturation capacity for high illumination levels. This segmentation allows each component to excel at its specific task without compromise
Solution Approach 2:
The dynamic switching mechanism directs single-photon signals to the first photodiode for high-sensitivity detection, while directing high illumination signals to the second photodiode for saturation-resistant handling, thereby achieving both single-photon sensitivity and high saturation performance simultaneously
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 provides an optical sensor with enhanced sensitivity, speed, and wide dynamic range, enabling effective detection from single-photon to high illumination levels, thus contributing to the development of safer and more secure societal applications.
Implementation Method 1
a light-receiving element, storage capacitors that store a charge, and a transfer switch for transferring to the storage capacitors a charge generated by light input to the light-receiving element
Data Source
AI summary
One problem addressed by the present invention is to provide an optical sensor, a solid-state imaging device, and methods for reading the signals therefrom, which contribute greatly to the development of industry and the realization of a safer and more secure society. One solution according to the present invention is an optical sensor having a light-receiving element, storage capacitors that store a charge, and a transfer switch for transferring to the storage capacitors a charge generated by light input to the light-receiving element, wherein the storage capacitors are a floating diffusion capacitor and a lateral overflow integration capacitor, and the transfer switch is a non-LDD/MOS transistor, that is, a non-LDD/MOS transistor for which the impurity concentration of the drain region is reduced by 50%.