Image Sensor Circuit Power Noise Filtering via Differential Amplification
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Solution Overview
Problem
Existing CMOS image sensor circuits face limitations in resolution and image quality due to power noise and dark current cancellation processes that degrade digital image signals after analog-to-digital conversion.
Innovation Solution
An image sensor circuit with a power noise filtering function using differential amplification between the image sensed signal and power noise signal, implemented with a differential amplifier circuit and an analog-to-digital converter, which generates a digital image signal by filtering out power noise before conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If power noise and dark current cancellation are performed on digital image signal after ADC conversion, then the processing can be done digitally, but the image quality and resolution are degraded
Solution Approach 1:
The patent applies preliminary action by performing power noise filtering through differential amplification before the ADC conversion. The circuit subtracts the power noise signal from the image sensed signal in the analog domain, generating a cleaned analog signal that is then converted to digital. This preliminary noise removal prevents degradation of signal quality that would occur if noise cancellation were performed after digital conversion.
2Ease of operation
If analog image signal is converted to digital signal first, then noise filtering can be applied, but the resolution is limited
Solution Approach 1:
The patent performs the noise filtering action before the ADC conversion by using a differential amplifier circuit that subtracts the power noise signal from the image sensed signal in the analog domain. This preliminary filtering ensures that only the cleaned analog signal undergoes quantization, thereby preserving maximum resolution while still providing effective noise cancellation.
Solution Approach 2:
The patent introduces an intermediary differential amplifier circuit between the image sensing unit and the ADC. This intermediary performs the noise subtraction operation in the analog domain, acting as a mediator that cleans the signal before digital conversion without losing the benefits of digital processing that follows.
3Measurement precision
If differential amplification is performed before ADC conversion, then power noise is filtered effectively, but the circuit complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing the differential amplifier circuit to simultaneously perform multiple functions: it acts as a noise subtraction device, a signal amplifier, and a buffer for the ADC input. By combining these functions in a single circuit stage, the patent reduces overall circuit complexity while maintaining effective power noise filtering accuracy.
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 the accuracy and resolution of digital image signals, simplifies the back-end circuit design, and reduces manufacturing costs by filtering power noise and dark current before digital signal generation.
Implementation Method 1
a differential amplifier circuit, which is coupled to the image sensing unit and the power noise sensing unit, for receiving the image sensed signal and the power noise signal, and generating a differential filtered signal by a differential amplification operation between the image sensed signal and the power noise signal
Implementation Method 2
a comparator, which is coupled to the differential amplifier circuit, for receiving the differential filtered signal to generate a for-count signal
Implementation Method 3
a counter circuit, which is coupled to the comparator, for converting the for-count signal to the digital image signal
Implementation Method 4
an image sensing unit, for sensing an image to generate an image sensed signal
Implementation Method 5
a power noise sensing unit, for sensing a power noise to generate a power noise signal
Data Source
AI summary
The present invention provides an image sensor circuit with a power noise filtering function and a control method thereof. The image sensor circuit includes: an image sensing unit, for sensing an image, to generate an image sensed signal; a power noise sensing unit, for sensing a power noise, to generate a power noise signal; a differential amplifier circuit, which is coupled to the image sensing unit and the power noise sensing unit, for receiving the image sensed signal and the power noise signal, to generate a differential filtered signal by a differential amplification operation between the image sensed signal and the power noise signal; and an analog-to-digital converter (ADC) circuit, which is coupled to the differential amplifier circuit, for receiving the differential filtered signal, to generate a digital image signal.