Pixel Group Isolation Layout for Autofocus Image Sensors
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Solution Overview
Problem
The performance of image sensors is reduced due to signal interference between photodiodes of adjacent pixels, particularly affecting autofocusing and image quality.
Innovation Solution
An image sensor design that includes a 2×2 matrix of pixel groups with device isolation patterns to electrically separate the pixels, reducing signal interference and enhancing autofocusing and image generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Deep Trench Isolation (DTI) is formed between photodiodes to prevent crosstalk, then signal interference is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the isolation function from the traditional DTI structure and implements it through software-based pixel grouping and selective readout. Pixels are virtually separated into first pixel groups (for phase detection) and second pixel groups (for color detection) through control signals, eliminating the need for physical isolation structures between all pixels.
Solution Approach 2:
The patent replaces the mechanical/physical isolation structure (DTI) with an electronic/control-based isolation method. The control circuit selectively activates and reads out specific pixel groups based on the desired function (AF or image capture), achieving signal separation through electronic control rather than physical barriers.
2Device complexity
If DTI is not formed between unit pixels to reduce manufacturing complexity, then signal interference occurs between photodiodes, but manufacturing is simpler
Solution Approach 1:
The patent changes the operational parameters of pixels through control signals, dynamically switching pixels between different functional states (phase detection mode or color detection mode). This temporal and functional parameter change allows pixels to be effectively isolated for signal processing purposes without physical isolation structures.
Solution Approach 2:
The patent segments the pixel array into functionally distinct groups (first pixel groups for phase detection, second pixel groups for color detection) that can be independently controlled and read out. This logical segmentation achieves signal separation without requiring physical segmentation through DTI structures.
3Area of stationary object
If pixels are closely arranged to increase pixel density, then sensor area is reduced, but signal interference between adjacent pixels increases
Solution Approach 1:
The patent introduces dynamic control of pixel functionality through control signals that can switch pixels between different operational modes. This dynamic approach allows closely spaced pixels to function independently for different purposes (phase or color detection) at different times, preventing signal interference while maintaining high density.
Solution Approach 2:
The patent makes pixels multi-functional by enabling them to serve either as phase detection pixels or color detection pixels based on control signals. This universality allows the same physical pixel structure to perform multiple functions without requiring additional physical separation or isolation structures.
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
Significantly reduces signal interference between phase and color signals, improving the performance of autofocusing and the quality of generated images.
Implementation Method 1
The plurality of unit pixels may include photodiodes which generate charges in response to external light
Data Source
AI summary
An image sensor is provided. The image sensor image sensor includes: a first pixel group including a first pixel, a second pixel, a third pixel and a fourth pixel; a second pixel group including a fifth pixel, a sixth pixel, a seventh pixel and an eighth pixel, wherein the second pixel group is provided adjacent to the first pixel in a first direction; a first lens corresponding to the first pixel and the second pixel; a second lens corresponding to the third pixel and the fourth pixel; a device isolation pattern electrically isolating the first pixel group from the second pixel group; and a readout circuit configured to: output phase data based on at least a portion of phase signals received from the first pixel group; and output image data based on at least a portion of color signals received from the second pixel group.