Solid-State Imaging Device Pixel Readout Circuit Layout
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Solution Overview
Problem
The miniaturization and cost reduction of solid-state imaging devices, such as CMOS image sensors, are hindered by the need for multiple selection transistors and non-symmetrical wiring layouts, which affect optical and electrical characteristics.
Innovation Solution
A configuration where pixels are grouped into larger units with shared readout lines and a scanning unit extending in the column direction, eliminating the need for horizontal scanning units and ensuring uniform characteristics by using a common vertical signal line for all pixels in a block.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multiple selection transistors are used for each pixel to enable row and column scanning, then pixel readout capability is improved, but device area and complexity increase
Solution Approach 1:
The invention extracts the horizontal scanning function from individual pixel circuits and relocates it to a column-level selection circuit. Each pixel only retains the necessary vertical selection transistor, while the horizontal scanning is performed by selecting specific columns through external control signals, thereby reducing the transistor count per pixel while maintaining full readout capability
Solution Approach 2:
The scanning function is segmented into two independent levels: row selection is handled by individual pixel transistors, while column selection is handled by a separate column selection circuit that controls signal transmission to multiple pixels simultaneously. This segmentation allows the system to achieve comprehensive scanning capability with reduced per-pixel complexity
2Ease of manufacture
If non-symmetrical wiring layouts are used to connect pixels to readout lines, then routing flexibility is improved, but optical and electrical characteristic uniformity deteriorates
Solution Approach 1:
The invention intentionally introduces asymmetry in the form of dummy wiring structures that are electrically inactive but geometrically present. These dummy wires are added to pixels with shorter signal paths to match the length and layout of pixels with longer paths, creating a uniform symmetrical appearance that ensures consistent optical and electrical characteristics across all pixels while maintaining the underlying routing flexibility
3Area of moving object
If pixels are miniaturized to increase pixel density, then device area is reduced, but wiring layout complexity and cost increase
Solution Approach 1:
The invention merges the horizontal scanning function into the column selection mechanism, eliminating the need for separate horizontal wiring and selection transistors at each pixel. By combining multiple pixel readout paths into shared column lines and using a unified selection approach, the wiring layout is simplified and regularized, enabling easier miniaturization while reducing overall device complexity
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 enables miniaturization, reduces costs, and achieves uniformity in pixel characteristics by simplifying the layout and eliminating the need for multiple selection transistors, while maintaining efficient readout capabilities.
Implementation Method 1
a pixel region that includes a plurality of pixels arranged in a matrix form
Data Source
AI summary
An imaging device includes a pixel region in which light sensing pixels are grouped into pixel-units that each include multiple pixels, each column including pixels from at least two of the pixel-units. Each of the pixel-units is connected, via a corresponding readout line, to a corresponding readout unit configured to perform analog-to-digital conversion on pixel signals output thereto. A scanning unit that extends in a column direction is configured to select pixels for readout by applying row scanning pulses to scan lines connected to rows. A scanning unit that extends in a row direction for applying readout-enabling scan pulses to lines connected to columns is omitted. Those pixels that are selected for readout by one of the row scanning pulses are read out independently of any enabling pulses applied to lines connected to columns.