Delta Image Sensor Digital Pixel Storage
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Solution Overview
Problem
Existing image sensors face challenges in efficiently storing and processing illumination level data within pixels, leading to issues such as gradual storage degradation, sensitivity to mismatch, and reduced flexibility in light-to-electric conversion, particularly in dynamic vision sensors.
Innovation Solution
A delta image sensor with digital storage of prior illumination intensity in each pixel, combined with local evaluation of differences over time and location, enabling efficient digital conversion, storage, and event generation within the pixel circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If analogue storage is used in dynamic vision sensors, then compact realisation is achieved, but gradual storage degradation and hot-pixel issues occur
Solution Approach 1:
The patent replaces the analogue storage mechanism (capacitor) with a digital storage mechanism (flip-flop circuit). This substitution eliminates the gradual degradation inherent in analogue capacitive storage while maintaining compact pixel circuit area. The digital flip-flop provides stable, non-degrading storage of illumination level data.
2Reliability
If digital storage is used in pixels, then storage fidelity is improved, but pixel circuit area increases
Solution Approach 1:
The patent combines the digital storage function (flip-flop) with the existing pixel circuit architecture, integrating it alongside the photodetector and readout circuitry. This merging approach allows digital storage to be implemented without proportionally increasing overall pixel area, as the storage element shares space with other pixel components.
Solution Approach 2:
The patent changes the storage mechanism from analogue to digital, fundamentally altering how illumination levels are retained. This parameter change enables high-fidelity storage while allowing for area optimization through shared circuitry and efficient layout of the flip-flop circuit within the pixel structure.
3Ease of operation
If processing is carried out outside the pixel array, then filtering can be performed, but data transmission requirements and processing cost increase
Solution Approach 1:
The patent segments the processing function by implementing event detection and filtering logic directly within each pixel circuit. This segmentation allows local processing of illumination data, generating and transmitting only relevant change events rather than all pixel data, thereby reducing data transmission volume while maintaining filtering capability.
Solution Approach 2:
The pixel circuit performs self-service by autonomously detecting illumination changes and generating events locally. The flip-flop circuit automatically compares current illumination levels with stored previous levels and generates events only when changes occur, eliminating the need for external processing of unchanged pixels and reducing overall data transmission requirements.
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 solution provides high-resolution, cost-optimized sensors with improved fidelity and reduced power consumption by leveraging digital storage and local processing, allowing efficient event generation and background subtraction within the pixel array.
Implementation Method 1
at least one sensor circuit (11) comprising a photodetector, which generates a sensor signal (VSIG) dependent on a light signal illuminating the photosensor of the at least one pixel
Data Source
Figure 1
Figure 2(a)~2(d)
Figure 3
AI summary
The present invention relates to a delta image sensor comprising an arrangement of pixels and a plurality of acquisition circuits corresponding to at least one pixel and formed as part of an integrated circuit. Each acquisition circuit includes at least one sensor circuit comprising a photosensor configured to generate a sensor signal, VSIG, depending on a light signal illuminating the photosensor of the at least one pixel; at least one analogue to digital conversion, A/D, circuit configured to convert a current VSIG to a digital signal; at least one digital storage circuit configured to store a representation of at least one digital signal corresponding to a previous VSIG; at least one digital comparison circuit configured to compare the level of the stored representation with the current VSIG to detect whether a changed level is present; and at least one digital output circuit configured to generate an event output under the condition of the changed level. A digital representation may be externally written to the digital storage circuit of the at least one pixel.