Adjustable Amplifier Circuitry for Image Sensor Readout
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Solution Overview
Problem
Existing image sensor readout circuitry struggles to optimize signal reading in varying light conditions, leading to suboptimal performance in low light scenarios with high read noise and power consumption issues in high light scenarios.
Innovation Solution
The implementation of adjustable readout circuitry with separate amplifier configurations for low light and high light signals, utilizing distinct control signals and amplifier settings to minimize noise and optimize settling accuracy and power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single readout circuitry configuration is used for both low light and high light signals, then the device complexity is reduced, but the measurement precision deteriorates in low light conditions due to high read noise
Solution Approach 1:
The readout circuitry is designed with dynamically switchable configurations that can adapt between low light mode and high light mode. The circuit includes switchable capacitor connections and adjustable amplifier gain settings that change based on the input signal conditions, allowing the same physical circuit to optimize its parameters for different operating conditions without requiring completely separate circuit paths.
Solution Approach 2:
The invention changes key circuit parameters such as amplifier gain, capacitor connections, and reference voltage levels based on the detected light conditions. By adjusting these parameters dynamically, the circuit achieves low noise performance for low light signals while maintaining functionality for high light signals, resolving the contradiction between measurement precision and device complexity.
2Measurement precision
If readout circuitry is optimized for low light signals with high settling accuracy, then the measurement precision improves, but the productivity decreases due to slower signal processing
Solution Approach 1:
The readout circuitry dynamically adjusts its operating parameters based on the input signal level. For low light signals requiring high precision, the circuit switches to a high-gain amplifier configuration with longer settling time. For high light signals where speed is more critical, the circuit switches to a lower-gain configuration with faster processing, thus achieving both high precision when needed and high productivity when possible.
Solution Approach 2:
The system periodically evaluates the input signal characteristics and switches between different operational modes accordingly. This periodic assessment and switching allows the circuit to spend most time in the faster, lower-precision mode for typical high light conditions while briefly entering the high-precision mode when low light signals are detected, balancing overall productivity with measurement precision.
3Productivity
If readout circuitry is optimized for fast high light signal processing, then the productivity improves, but the use of energy increases due to higher power consumption
Solution Approach 1:
The readout circuitry dynamically adjusts its power consumption based on the input signal conditions. By switching between different amplifier gain stages and capacitor configurations, the circuit consumes higher power only when fast processing of high light signals is required, and reduces power consumption during low light conditions where slower, lower-power operation is acceptable. This dynamic power management resolves the contradiction between productivity and energy usage.
4Measurement precision
If separate amplifier circuitry is used for low light and high light signals, then the measurement precision improves for each signal type, but the device complexity increases
Solution Approach 1:
The invention designs a universal readout circuit that can perform multiple functions by switching between different configurations. A single amplifier circuit is designed to handle both low light and high light signals by adjusting its gain and connection topology, rather than requiring completely separate amplifier paths. This multi-functional approach achieves signal-type-specific optimization while avoiding the full complexity of completely separate circuits.
Solution Approach 2:
The invention merges the low light signal path and high light signal path into a single integrated readout circuit with switchable configurations. By combining shared components (amplifier, capacitors, switches) that can be dynamically reconfigured, the design achieves the precision benefits of separate circuits while reducing overall device complexity through component sharing and integration.
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 improved low light signal quality with reduced noise and faster high light signal processing while lowering power consumption, enhancing overall imaging performance.
Implementation Method 1
Each image pixel contains a photodiode for generating charge in response to incident light
Data Source
AI summary
An image sensor may include an array of image pixels. The array of image pixel may be coupled to column readout circuitry. A given image pixel may generate a low light signal and a high light signal for a given exposure. A column line may couple the given image pixel to readout circuitry having amplifier circuitry. The column line may be coupled to an autozeroing transistor for reading out the high light signal and a source follower stage for readout out the low light signal. The amplifier circuitry may receive different common mode voltage depending on whether it is amplifying the low or high light signal. The gain and other operating parameters of the amplifier circuitry may be adjusted based on whether it is amplifying the low or high signal. If desired, separate amplifier circuitry may be implemented for the low and high light signals.