Image Sensor Reference Signal Circuit for Noise Reduction
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Solution Overview
Problem
Conventional image sensors face challenges in reducing fixed pattern noise and power supply ripple noise, which degrades image quality and affects the yield ratio of image sensors during signal transmission.
Innovation Solution
The image sensor incorporates a reference signal generating unit with a circuit structure equivalent to the imaging signal generating unit, which generates a reference signal with the same phase fluctuation component as the imaging signal, allowing for effective noise elimination using a correlated double sampling circuit, and includes a buffer to alternately output imaging and reference signals, thereby reducing noise and improving power supply rejection ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional image sensors use standard signal transmission without reference signals, then device complexity is low, but noise components (fixed pattern noise and power supply ripple noise) degrade image quality
Solution Approach 1:
The patent creates a reference signal by copying the imaging signal through an equivalent circuit path. The reference signal generating unit includes photoelectric conversion elements, conversion circuits, noise eliminating circuits, and output circuits that mirror the imaging signal path, producing a reference signal with the same phase fluctuation components. This copied reference signal is then used to eliminate noise through correlated double sampling, resolving the contradiction by using a simplified copying approach rather than complex noise filtering
Solution Approach 2:
The patent introduces a reference signal as an intermediary element that mediates between the noisy imaging signal and the noise elimination process. The reference signal acts as a mediator carrying the same power supply ripple and phase fluctuations, enabling the correlated double sampling circuit to identify and remove noise components. This intermediary approach allows noise elimination without requiring complex direct filtering of the imaging signal
2Measurement precision
If image sensors implement noise elimination circuits, then image quality improves, but power consumption increases
Solution Approach 1:
The patent implements periodic action by alternately outputting the imaging signal and the reference signal through a switching mechanism. The buffer unit switches between storing the imaging signal and the reference signal, and the correlated double sampling circuit periodically processes these alternating signals. This periodic operation allows noise elimination to occur in discrete phases rather than continuously, reducing overall power consumption while maintaining image quality through the periodic noise cancellation process
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 effectively eliminates noise components during signal transmission, enhances image quality, and improves the yield ratio of image sensors by alternately outputting imaging and reference signals with synchronized phase fluctuations, preventing image degradation and optimizing power supply rejection.
Implementation Method 1
a plurality of photoelectric conversion elements arranged in a two-dimensional matrix form, each of the plurality of photoelectric conversion elements being configured to receive light from outside and accumulate a charge corresponding to an amount of received light
Data Source
AI summary
An image sensor includes: photoelectric conversion elements configured to receive light and accumulate a charge corresponding to an amount of received light; an imaging signal generating unit that converts the charge accumulated in each photoelectric conversion element into a voltage to generate an imaging signal; and a reference signal generating unit that generates a reference signal having a fluctuation component with a same phase as the imaging signal. The imaging signal generating unit includes: a conversion circuit that converts the charge accumulated in each photoelectric conversion element into the imaging signal; a noise eliminating circuit that eliminates a noise component included in the imaging signal; and an output circuit that outputs the imaging signal from the conversion circuit. The reference signal generating unit includes a circuit having a same structure as that of at least one of the conversion circuit, the noise eliminating circuit, and the output circuit.