Stacked Image Sensor ADC Layout for Faster Pixel Readout
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In layered imaging devices, the size reduction of pixels leads to challenges in miniaturizing AD converter circuits, resulting in increased time lags and potential image distortion when capturing moving objects, as shared AD converter circuits struggle to handle a large number of pixels efficiently.
Innovation Solution
The implementation of a stacked substrate structure where pixels and a comparing unit on the upper substrate compare signal voltages with ramp voltages, while a storage unit on the lower substrate stores code values, allowing for optimized power supply voltages and separate circuit designs for analog and digital components, reducing the size of the imaging device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If one AD converter circuit is shared by more than one pixel, then the number of AD converter circuits is reduced and device size is decreased, but the time lags among pixels increase and image distortion occurs
Solution Approach 1:
The imaging device is divided into multiple independent imaging units, each containing its own AD converter circuit. This segmentation allows each pixel to have a dedicated converter, eliminating time lags while maintaining compact device size through the stacked substrate architecture.
Solution Approach 2:
The patent transitions from a planar layout to a three-dimensional stacked substrate structure. By placing pixel circuits on one substrate and AD converter circuits on another substrate in the vertical dimension, the device achieves higher integration density without increasing lateral footprint, resolving the contradiction between device size and processing speed.
2Quantity of substance
If pixels are made smaller, then the number of pixels increases and image quality improves, but the AD converter circuits become difficult to miniaturize
Solution Approach 1:
The patent uses stacked substrates to separate pixel circuits from AD converter circuits vertically. This allows pixels to be miniaturized on the first substrate while AD converter circuits are placed on a second substrate, avoiding the need to miniaturize both together and enabling higher pixel density without proportionally increasing converter circuit complexity.
Solution Approach 2:
The AD converter circuit is designed with a universal structure that can handle multiple pixels' signals through time-division multiplexing. This universal design reduces the total number of converter circuits needed while maintaining performance, as each converter can sequentially process signals from multiple pixels without requiring individual dedicated converters for each pixel.
3Productivity
If the number of pixels handled by one AD converter circuit is reduced, then time lags decrease and processing speed improves, but more AD converter circuits are needed increasing device size
Solution Approach 1:
By stacking substrates vertically, the patent accommodates multiple AD converter circuits in the vertical dimension rather than spreading them horizontally. This allows more converter circuits to be integrated without increasing the lateral device footprint, enabling faster parallel processing while maintaining compact size.
Data Source
AI summary
The present technology relates to an imaging device that can reduce the size thereof, and to an electronic apparatus.An upper substrate and a lower substrate are stacked. A pixel and a comparing unit that compares the voltage of a signal from the pixel with the ramp voltage are provided on the upper substrate, the ramp voltage varying with time. A storage unit that stores a code value obtained at a time when a comparison result from the comparing unit is inverted is provided on the lower substrate. The comparing unit is formed with a transistor that receives the voltage of the signal from the pixel at the gate, receives the ramp voltage at the source, and outputs a drain voltage. Accordingly, the imaging device can be made smaller in size. The present technology can be applied to image sensors.