Imaging Device CDS Circuit for High-Speed Touch Sensing
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Solution Overview
Problem
Imaging devices used in electronic devices for touch sensing and biometric authentication face challenges in achieving high frame frequency and accuracy for image capturing and biometric authentication, which affects the precision of motion sensing and authentication processes.
Innovation Solution
The implementation of an imaging device with a pixel and a Correlated Double Sampling (CDS) circuit, including specific transistors and capacitors, allows for high-speed image capturing by controlling current flow and charge storage, enabling high-frame frequency operation and improved signal-to-noise ratio for accurate image sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-frame frequency image capturing is implemented for touch sensing, then motion sensing accuracy is improved, but image capturing accuracy for biometric authentication deteriorates
Solution Approach 1:
The imaging device dynamically adjusts its operating mode between high-frame frequency operation for touch sensing and high-accuracy operation for biometric authentication. The system can switch between different readout speeds and exposure settings based on the detected application scenario, allowing optimal performance for each specific function without being constrained by a fixed operating mode.
2Measurement precision
If high-accuracy image capturing is performed for biometric authentication, then authentication accuracy is improved, but frame frequency for motion sensing deteriorates
Solution Approach 1:
The imaging device segments its operation into distinct functional modes: one optimized for high-speed touch sensing with reduced readout time, and another optimized for high-precision biometric authentication with extended exposure and processing time. This segmentation allows each function to operate at its optimal performance level without compromising the other.
3Device complexity
If the imaging device structure is simplified, then device complexity is reduced, but image capturing accuracy and reliability deteriorate
Solution Approach 1:
The imaging device employs a universal pixel structure and signal processing circuitry that can serve multiple functions: high-speed readout for touch sensing and high-precision readout for biometric authentication. By designing the circuit to handle both operational modes with a single structure, the patent avoids the need for separate dedicated circuits for each function, thereby maintaining reliability while controlling 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 solution enables imaging devices to perform high-frame frequency image capturing and biometric authentication with enhanced accuracy, effectively sensing the position of targets with high precision, thus improving the reliability and accuracy of touch sensing and authentication functions.
Implementation Method 1
imaging device including a pixel and a CDS circuit
Data Source
AI summary
To provide an imaging device having a function of biometric authentication and a function of a touch sensor or a near touch sensor. The imaging device includes pixels, current mirror circuits, and CDS circuits. The pixels, the current mirror circuits, and the CDS circuits are electrically connected to read lines. The current mirror circuit includes a first and a second transistor. One of a source and a drain of the first transistor is electrically connected to the read line, and a power supply potential is supplied to the other of a source and a drain of the second transistor. The imaging device outputs imaging data written to the pixel, as a first signal, to the read line in a first period, and then, resets the imaging data and outputs a second signal from the pixel to the read line in a second period. In the first period, a first potential is supplied to terminals, and in the second period, a second potential is supplied to terminals. A difference between the second potential and the power supply potential is greater than a difference between the first potential and the power supply potential.