Pixel Cell Voltage Resetting for CMOS Image Sensor Signal Precision
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Solution Overview
Problem
Current image processing technologies face challenges in efficiently recording and processing image information, particularly in areas like white light interferometry, where rapid and efficient data processing of large sensor-generated data is desirable.
Innovation Solution
A charge-based analog/digital signal processing method is implemented using a CMOS image sensor with integrated preprocessing, featuring pixel cells that generate measurement currents independently of radiation, store currents, and form differences for efficient readout, along with methods for determining charge amounts on capacitive elements and setting circuit nodes to predetermined voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photosensor generates measurement currents in each measurement cycle, then measurement precision is improved, but device complexity increases due to the need for current storage and differential processing circuits
Solution Approach 1:
The patent introduces a current storage device as an intermediary component between the photosensor and the output. This storage device holds the measurement current from one measurement cycle while a new measurement current is generated in the next cycle, enabling differential processing without requiring complex simultaneous processing circuits. The storage device acts as a buffer that simplifies the overall circuit architecture while maintaining high measurement precision through correlated double sampling.
2Productivity
If rapid data processing is implemented for large sensor data volumes, then productivity is improved, but loss of time occurs during voltage resetting operations
Solution Approach 1:
The patent implements periodic alternating operation between two measurement cycles: in the first cycle, voltage is applied to the gate capacitance and measurement current is generated; in the second cycle, the voltage is reset and a new measurement is performed. This periodic alternation allows the system to maintain continuous productivity by overlapping measurement, storage, and resetting operations across different pixel cells, rather than performing sequential operations that would cause time loss.
3Measurement precision
If voltage is continuously applied to gate capacitance for signal accumulation, then measurement precision is improved, but object-generated harmful factors increase due to pixel saturation and blooming effects
Solution Approach 1:
The patent employs periodic application and resetting of voltage to the gate capacitance. During the first measurement cycle, voltage is applied to accumulate signal charge on the gate capacitance, improving measurement precision. During the second measurement cycle, the voltage is reset, which clears the gate capacitance and prevents pixel saturation and blooming effects. This periodic on-off cycling of voltage allows the pixel to handle high light intensities without permanent saturation while still achieving accurate signal accumulation during the active measurement phase.
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 enables more efficient data recording and processing, allowing for improved signal processing and determination of charge amounts, enhancing the accuracy and speed of image data handling in applications like white light interferometry.
Implementation Method 1
a photosensor (110) designed in order to generate a voltage VPh over the photosensor (110) as a function of a radiation
Data Source
AI summary
A pixel cell, and a method of use thereof, the pixel cell including: an output, a photosensor configured to generate a first measuring current in a first measurement cycle and a second measuring current in a second measurement cycle as a function of radiation, an output node, a power storage device configured so that in a first operating mode a current can be injected by the power storage device as a function of the first measuring current, and so that in a second operating mode the power storage device is configured to hold the injected current so that the injected current can be detected at the output node, and a switching unit configured to form a difference between the injected current and the second measuring current at the output node in a reading cycle and to couple the output node to the output.