Image Sensor Corner Cuts Analog Circuit Layout
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Solution Overview
Problem
CMOS image sensors with cut corners face challenges in ergonomics and comfort due to fixed pattern noise (FPN) and capacitive effects from non-uniform positioning of analog circuits, which are difficult to correct in oblique corner configurations.
Innovation Solution
The solution involves placing current or voltage read blocks along a horizontal edge of the matrix within a vertical strip, with a width substantially less than the maximum width, and using a column select circuit between read block rows to minimize capacitive interference and FPN, allowing for efficient image signal processing without compromising image area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the chip is cut at the corners to improve ergonomics and reduce package volume, then the package shape becomes more ergonomic and volume is reduced, but fixed pattern noise increases due to non-uniform positioning of analog circuits
Solution Approach 1:
The patent applies local quality by creating a concentrated region for analog circuits (read blocks and column select circuits) within a vertical strip along one edge of the matrix. This localized arrangement ensures uniform positioning and spacing of analog circuits within their dedicated region, while the rest of the matrix maintains its regular structure. This resolves the FPN issue by ensuring analog circuits have consistent local environments despite the overall corner-cut shape.
Solution Approach 2:
The patent employs asymmetry by concentrating all analog circuits along one vertical edge of the matrix rather than distributing them symmetrically around the perimeter. This asymmetric arrangement accommodates the corner-cut shape while maintaining proper spacing and positioning of analog circuits. The read blocks and column select circuits are housed within a vertical strip of width L1 less than the maximum matrix width L, creating an asymmetric but controlled layout that prevents FPN.
2Ease of manufacture
If read blocks are distributed along the periphery of the matrix to maintain uniform spacing, then manufacturing is easier, but capacitive effects from digital line select circuits increase when corners are cut
Solution Approach 1:
The patent extracts the analog circuits (read blocks and column select circuits) from the general periphery distribution and concentrates them within a specific vertical strip along one edge of the matrix. This separation isolates analog circuits from the digital line select circuits that run along the edges, reducing capacitive coupling. The analog circuits are housed in a dedicated region of width L1, physically separated from the digital signaling paths.
Solution Approach 2:
The patent introduces a vertical strip region as an intermediary zone that houses analog circuits away from the edge where digital line select circuits are positioned. This intermediate region acts as a buffer zone that reduces direct capacitive coupling between digital and analog circuits. The separation allows digital signals to be transmitted along the edges while analog circuits remain in a protected intermediate region.
Data Source
AI summary
The invention relates to image sensors using a chip with cut corners. The sensor comprises a chip with cut corners comprising a matrix (10) of horizontal lines and vertical columns of photosensitive members, the matrix having a generally rectangular shape of horizontal width W and having four bevels, the sensor comprising as many current or voltage read blocks as there are matrix columns, in order to read the image signals detected by the photosensitive members, characterized in that the current or voltage read blocks are placed in a row (30, 30′) along a horizontal edge of the matrix of width W′ and are all housed within a vertical strip, the width W1 of which is substantially less than the maximum width W of the matrix. There are two superposed rows of current read blocks with blocks distributed at the same pitch as the pixel columns, or there is a single row with read blocks distributed with a pitch less than that of the pixel columns. The invention can be applied to CMOS technology intraoral radiological sensors.