Image Sensor Having Pixels In LInear Mode and Photovoltaic Mode
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Solution Overview
Problem
Image sensors face challenges in achieving a wide dynamic range and are prone to flicker due to LED light emission control, which mixes on and off states, affecting image quality.
Innovation Solution
The image sensor pixels operate in both linear and photovoltaic modes, incorporating a peak hold circuit with a knee pulse supplying unit to transition the photodiode from a saturated state and suppress flicker, using multiple knee pulses during a frame period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the photodiode operates in linear mode for wide dynamic range, then the dynamic range is improved, but the photodiode enters saturated state under strong light causing loss of signal information
Solution Approach 1:
The patent applies parameter changes by switching the photodiode operating mode between linear mode and photovoltaic mode based on light intensity conditions. When saturation is detected, the system transitions to photovoltaic mode which provides logarithmic response characteristics, allowing the photodiode to continue capturing signal information without saturation while maintaining wide dynamic range capability.
Solution Approach 2:
The patent implements dynamics by making the photodiode operating mode adjustable rather than fixed. The system dynamically switches between linear and photovoltaic modes based on real-time signal conditions, enabling the photodiode to adapt its response characteristics to avoid saturation while maintaining optimal performance across varying light conditions.
2Ease of operation
If PWM control is used to control LED light amount, then the light emission is controlled precisely, but the repeated on/off causes flicker in the acquired image
Solution Approach 1:
The patent converts the harmful flicker effect into a beneficial feature by utilizing the repeated on/off cycles of PWM-controlled LED light. The peak hold circuit captures the peak signal during the light-on periods, and the knee pulse circuit compensates for the light-off periods, transforming the flicker artifact into an opportunity to enhance signal accuracy and suppress visible flicker in the final image.
Solution Approach 2:
The patent implements feedback mechanisms through the peak hold circuit that continuously monitors and holds the peak signal value, and the knee pulse supplying unit that provides corrective pulses based on the signal state. This feedback system ensures that the photodiode output remains stable and free from flicker artifacts despite the PWM control of the LED.
3Object-affected harmful factors
If a peak hold circuit is added to suppress flicker, then the flicker is reduced, but the device complexity increases
Solution Approach 1:
The patent merges the peak hold circuit and knee pulse supplying unit into an integrated circuit structure that works together as a unified system. Rather than adding completely separate complex circuits, the design combines these functions into a coordinated assembly that shares common components and control logic, thereby suppressing flicker while minimizing the increase in overall device complexity.
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 approach widens the dynamic range and effectively suppresses flicker, maintaining signal quality by temporarily canceling saturation and utilizing a peak hold circuit to maintain signal levels.
Implementation Method 1
a photodiode configured to operate in a linear mode in which the photodiode shows a linear response to incident light and also in a photovoltaic mode in which the photodiode shows a logarithmic response to the incident light
Data Source
AI summary
In a case where a photodiode is in a saturated state, the photodiode can be transited from the saturated state to an unsaturated state during a period when a knee pulse is supplied from a knee pulse supplying unit. The knee pulse supplying unit preferably supplies the knee pulse a plurality of times during one frame period.