Delta Image Sensor Pixel Storage for Local Change Detection
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Solution Overview
Problem
Existing image sensors lack an efficient mechanism for storing and comparing previous illumination levels within pixels to detect changes, which limits their ability to optimize pixel structure for high resolution and cost-effectiveness.
Innovation Solution
A delta image sensor with a pixel circuit that includes a photosensor, an analogue to digital conversion circuit, digital storage for previous illumination levels, and a digital comparison circuit to detect changes, enabling local evaluation and event generation within the pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital storage and comparison circuits are integrated into each pixel, then change detection capability is improved, but pixel area increases
Solution Approach 1:
The pixel array is divided into multiple blocks, with each block containing multiple pixels that share common digital storage and comparison circuits. This segmentation allows change detection functionality to be distributed across blocks rather than requiring full dedicated circuits in each pixel, thereby reducing individual pixel area while maintaining detection capability.
Solution Approach 2:
The digital storage and comparison circuits are designed as shared resources that serve multiple pixels within a block. These circuits perform multiple functions: storing illumination levels for multiple pixels, comparing current readings against stored values, and generating change detection outputs for the entire block, thereby reducing the area required per pixel.
2Measurement precision
If dedicated ADC circuits are provided for each pixel, then conversion precision is improved, but device complexity increases
Solution Approach 1:
Multiple pixels within a block share a common ADC circuit. The ADC is time-multiplexed across the pixels in the block, converting analogue signals from multiple pixels sequentially. This merging of ADC resources reduces the total number of ADC circuits required, thereby reducing device complexity and area while maintaining conversion precision through proper timing and buffering.
3Adaptability or versatility
If digital storage is implemented in each pixel, then flexibility of light to electric conversion is improved, but power consumption increases
Solution Approach 1:
The digital storage and comparison operations are performed periodically at specific sampling intervals rather than continuously. Pixels accumulate analogue charge during integration periods, then transfer to digital storage and perform comparisons at discrete time points. This periodic operation reduces power consumption compared to continuous processing while maintaining the flexibility to adapt conversion parameters at each sampling period.
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 allows for efficient detection of illumination changes, enabling high-resolution, cost-optimized image sensors with reduced power consumption and improved processing efficiency.
Implementation Method 1
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
Data Source
AI summary
A delta image sensor comprising an arrangement of pixels and a plurality of acquisition circuits corresponding to at least one pixel. Each acquisition circuit includes at least one sensor circuit comprising a photosensor configured to generate a sensor signal, VSIG, depending on a light signal; 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 a changed level; and at least one digital output circuit configured to generate an event output under the condition of the changed level. The sensor circuit is configured to change an analogue function of its read-out characteristics to generate a respective changed VSIG.