Offset-Canceling Sampling Circuit for Accurate Image Sensor Readout
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Sensor devices with unit cell arrays face accuracy deterioration due to offsets caused by environmental variations, such as process and temperature differences, leading to inaccurate physical quantity measurements.
Innovation Solution
An offset canceling circuit comprising a decoupling capacitor, a buffer, and a feedback circuit that receives a reference voltage to store charge corresponding to a voltage difference between the reset and data voltages, allowing for the generation of a second voltage that cancels out the offset, thereby improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If unit cell arrays are used to sense physical quantities, then sensing capability is provided, but offset errors occur due to environmental variations causing accuracy deterioration
Solution Approach 1:
The patent applies preliminary action by performing offset cancellation before the actual measurement process. The circuit stores the offset voltage in a capacitor during a reset phase, then subtracts this stored offset from the subsequent data voltage to eliminate measurement errors caused by environmental variations.
Solution Approach 2:
The patent implements feedback by using the stored offset voltage to correct the data voltage. The circuit feeds back the offset information from the reset phase to the data phase through a capacitor, automatically compensating for environmental variations without external intervention.
2Measurement precision
If offset cancellation circuitry is added to improve accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges the offset cancellation function with the existing sensor readout circuitry. By integrating the capacitor and switch elements into the standard pixel array architecture, the patent achieves offset compensation without adding separate complex cancellation circuits for each pixel.
Solution Approach 2:
The patent creates a universal offset cancellation mechanism that can be applied to all unit cells in the array through shared circuit elements. The capacitor and control logic serve multiple pixels simultaneously, providing offset compensation across the entire sensor array rather than requiring individual circuits for each pixel.
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 proposed solution effectively cancels out offsets in unit cell voltages, enhancing the accuracy of sensor devices by ensuring that only the desired signal is output, independent of environmental variations.
Implementation Method 1
a decoupling capacitor having a first electrode coupled to a unit cell and a second electrode
Data Source
AI summary
An offset canceling circuit stores charge corresponding to a voltage difference between a reset voltage received from a unit pixel and a reference voltage, thereby canceling an offset of the unit pixel.