Image Sensor Bad Pixel Memory Segmentation Across Test Phases
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Solution Overview
Problem
Conventional image sensors fail to record additional bad pixel information generated after initial testing, leading to decreased production yield due to environmental factors like cosmic rays, and existing test devices cannot effectively manage changing pixel characteristics.
Innovation Solution
An image sensor and test device that includes a memory area for storing bad pixel information, allowing additional bad pixel data to be recorded and utilized for correction, improving yield by separately storing information in multiple memory areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bad pixel information is stored only during initial EDS test, then test process is simple, but additional bad pixels generated after testing cannot be recorded leading to decreased yield
Solution Approach 1:
The memory device is divided into a first memory area for storing initial bad pixel information and a second memory area for storing additional bad pixel information generated after testing. This segmentation allows the system to track bad pixels across multiple test phases without requiring a complete redesign of the memory structure, thereby improving yield while managing complexity.
Solution Approach 2:
The patent adds a temporal dimension to bad pixel storage by creating separate memory areas for different test phases (initial EDS test vs. subsequent tests). This dimensional approach allows the system to preserve and distinguish bad pixel information across time, enabling comprehensive yield improvement without overwhelming complexity.
2Reliability
If multiple memory areas are used to store bad pixel information from different test phases, then comprehensive bad pixel tracking is achieved, but memory structure becomes more complex
Solution Approach 1:
The memory device is segmented into distinct first and second memory areas, each dedicated to specific test phases. This segmentation ensures that bad pixel information from different phases is stored separately and accurately, improving reliability while keeping each memory area's structure manageable and well-defined.
Solution Approach 2:
The memory structure is preliminarily configured with designated first and second memory areas before testing begins. This preliminary arrangement ensures that when bad pixels are detected at different stages, the information can be immediately stored in the appropriate area without requiring complex real-time memory management decisions, thus improving reliability without excessive complexity.
3Manufacturing precision
If bad pixels are not corrected based on comprehensive information, then processing is faster, but image quality degrades due to uncorrected bad pixels
Solution Approach 1:
The bad pixel correcting circuit receives feedback from both the first and second memory areas containing comprehensive bad pixel information from all test phases. This feedback mechanism enables the circuit to make accurate correction decisions based on complete information, improving image quality while the automated feedback process prevents excessive complexity in the correction logic.
Solution Approach 2:
The bad pixel correcting circuit merges information from the first memory area (initial test) and the second memory area (subsequent tests) to create a comprehensive bad pixel map. This merging of information sources allows for more accurate image quality improvement while the unified correction approach prevents the circuit complexity from multiplying proportionally to the information sources.
Data Source
AI summary
An image sensor test device includes: an interface configured to transmit a control signal to an image sensor to be tested; and a host device configured to transmit, to the image sensor, a storage control signal instructing to store information about a bad pixel which is determined based on an output signal of the image sensor, wherein the output signal corresponds to the control signal, and wherein the storage control signal includes a signal of instructing to store the information about the bad pixel in a memory area of a plurality of memory areas.