Photodiode Pixel Sensitivity Layout for Overexposure-Free Ranging
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Solution Overview
Problem
Conventional optical sensors and photodiodes suffer from uniform pixel light sensitivity leading to overexposure issues and low photon detection efficiency, particularly when close to objects, and require coupling the p-type substrate to a negative voltage level, complicating IC design.
Innovation Solution
An optical sensor with pixels of varying light sensitivities and a photodiode structure that includes a p-type substrate with specific doping regions and voltage configurations to enhance photon detection without requiring a negative voltage coupling, utilizing avalanche regions and positive electric fields to attract electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If all pixels have the same light sensitivity, then the device structure is simple, but overexposure occurs when close to objects causing inaccurate distance computation
Solution Approach 1:
The patent applies local quality by differentiating pixel light sensitivities into high sensitivity pixels and low sensitivity pixels. Low sensitivity pixels are specifically designed to prevent overexposure when the device is close to objects, while high sensitivity pixels are used when objects are farther away. This local differentiation resolves the contradiction by allowing the system to maintain measurement precision across varying distances without requiring completely different device structures.
2Reliability
If the p type substrate is coupled to a negative voltage level to attract electrons, then photon detection efficiency improves, but IC design complexity increases due to voltage level coupling requirements
Solution Approach 1:
The patent inverts the conventional approach by coupling the p type substrate to a positive voltage level instead of a negative voltage level. The positive voltage level creates a positive electric field that attracts electrons from the p type substrate to the n type substrate, achieving the same electron attraction effect without requiring negative voltage coupling. This inversion simplifies IC design while maintaining high photon detection efficiency.
3Ease of operation
If the p type substrate is coupled to a negative voltage level, then electrons are attracted effectively, but the structure causes difficulty in designing integrated circuits
Solution Approach 1:
The patent inverts the conventional voltage coupling approach by using a positive voltage level instead of a negative voltage level. This inversion maintains effective electron attraction through the creation of a positive electric field while significantly simplifying IC design and manufacturing processes, as positive voltage coupling is more compatible with standard IC fabrication techniques.
4Measurement precision
If high sensitivity pixels are used for close objects, then detection accuracy improves, but overexposure occurs; if low sensitivity pixels are used, then overexposure is prevented, but detection accuracy decreases
Solution Approach 1:
The patent applies dynamics by enabling the optical sensor to dynamically select between high sensitivity pixels and low sensitivity pixels based on the distance to the object. When the object is close, low sensitivity pixels are selected to prevent overexposure; when the object is farther away, high sensitivity pixels are selected to maintain detection accuracy. This dynamic selection resolves the contradiction by adapting the system's sensitivity to the operating conditions.
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 enables accurate distance computation by selectively using high and low sensitivity pixels and improves photon detection efficiency, ensuring normal operation even when close to objects, while avoiding the need for negative voltage coupling.
Implementation Method 1
a positive electric field providing structure, provided in the P type substrate, configured to receive a positive voltage to provide a positive electric field according to the positive voltage to attract electrons in the P type substrate
Implementation Method 2
an avalanche region is formed when the positive voltage is larger than a threshold voltage, thereby a current path is formed between the signal output region and the positive electric field providing structure
Implementation Method 3
an optical sensor which has pixels with different light sensitivities, and relates to a photodiode which can improve photon detection efficiencies
Data Source
AI summary
A photodiode, comprising: a first photodiode, comprising a p type substrate and a signal output region; a positive electric field providing structure, provided in the P type substrate, configured to receive a positive voltage to provide a positive electric field according to the positive voltage to attract electrons in the P type substrate; wherein an avalanche region is formed when the positive voltage is larger than a threshold voltage, thereby a current path is formed between the signal output region and the positive electric field providing structure. The present invention also discloses an optical sensor comprising pixels with different light sensitivities.