Reset Transistor Voltage Sequencing for Blooming Suppression
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Solution Overview
Problem
The existing photoelectric conversion apparatuses face challenges in effectively suppressing blooming, where charges from a saturated pixel overflow to adjacent pixels, degrading image quality, especially when the potential of the floating diffusion portion is not sufficiently high due to low voltage supply to the reset transistor.
Innovation Solution
A photoelectric conversion apparatus and driving method that include a sequence of voltage supply to the reset transistor, with a first voltage falling between the ON-state and OFF-state voltages, ensuring the potential of the floating diffusion portion is adequately high, comprising a first period with the first voltage, a second period with a higher voltage to set the reset transistor to the ON state, and a third period to set it to the OFF state, with the second voltage supplied before signal output and for a longer duration than the third voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low voltage is supplied to the reset transistor during charge accumulation, then power consumption is reduced, but blooming suppression becomes insufficient because the floating diffusion portion potential is not sufficiently high
Solution Approach 1:
The patent applies periodic action by dividing the charge accumulation period into multiple phases with different voltage levels supplied to the reset transistor gate. Instead of maintaining a constant low voltage, the system periodically switches between a first voltage (lower, for power saving) and a second voltage (higher, for blooming suppression) based on the accumulation timing, thereby achieving both power efficiency and effective blooming suppression at different time points.
Solution Approach 2:
The patent implements dynamics by making the reset transistor gate voltage adjustable and time-dependent. The voltage supplied to the reset transistor is dynamically changed from a first voltage during initial accumulation to a second voltage during later accumulation phases, allowing the system to adapt the blooming suppression strength according to the accumulation progress while managing power consumption effectively.
2Object-affected harmful factors
If a high voltage is supplied to the reset transistor to suppress blooming, then blooming is effectively suppressed, but power consumption increases
Solution Approach 1:
The patent applies periodic action by dividing the charge accumulation period into multiple phases with different voltage levels supplied to the reset transistor gate. Instead of maintaining a constant low voltage, the system periodically switches between a first voltage (lower, for power saving) and a second voltage (higher, for blooming suppression) based on the accumulation timing, thereby achieving both power efficiency and effective blooming suppression at different time points.
Solution Approach 2:
The patent implements dynamics by making the reset transistor gate voltage adjustable and time-dependent. The voltage supplied to the reset transistor is dynamically changed from a first voltage during initial accumulation to a second voltage during later accumulation phases, allowing the system to adapt the blooming suppression strength according to the accumulation progress while managing power consumption effectively.
3Loss of time
If the second voltage is supplied for a short duration, then the accumulation period is shortened, but blooming suppression effectiveness is reduced
Solution Approach 1:
The patent implements dynamics by making the reset transistor gate voltage adjustable and time-dependent. The voltage supplied to the reset transistor is dynamically changed from a first voltage during initial accumulation to a second voltage during later accumulation phases, allowing the system to adapt the blooming suppression strength according to the accumulation progress while managing power consumption effectively.
Solution Approach 2:
The patent applies preliminary action by supplying the second voltage (higher voltage for blooming suppression) before the signal is output from the amplification transistor. This timing ensures that the floating diffusion portion is properly prepared and the blooming suppression is most effective during the critical readout phase, preventing any potential blooming issues before they can manifest in the output signal.
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 enhances blooming suppression by maintaining a higher potential of the floating diffusion portion, thereby reducing image quality degradation and improving the dynamic range of the image obtained.
Implementation Method 1
a photoelectric converter, a floating diffusion portion, a transfer transistor configured to transfer charges generated in the photoelectric converter
Data Source
AI summary
A photoelectric conversion apparatus including pixels is provided. Each pixels comprises a photoelectric converter, a floating diffusion, a transfer transistor between the photoelectric converter and the floating diffusion, a reset transistor resetting the floating diffusion, and an amplification transistor outputting a signal from the pixel to a signal line. An accumulation period includes, sequentially, a first period supplying a first voltage to a gate of the reset transistor, a second period supplying a second voltage to the gate, and a third period supplying a third voltage to set the reset transistor to the OFF to the gate. The first voltage is a voltage that falls between the second voltage and the third voltage, the second period is started before the signal is output, and the second period is longer than the third period.