Optically Black Pixels Light-Blocking Structures
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Solution Overview
Problem
Image sensors with optically black pixels face inaccuracies in dark current measurements and noise compensation due to light redirection from dummy pixels, leading to improper calibration.
Innovation Solution
Incorporating light-blocking structures, such as metal light-blocking layers and black light shields, in both dummy and optically black pixels to prevent light from reaching the optically black pixels, ensuring accurate dark current measurements and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dummy pixels are provided between the array of image pixels and the optically black pixels, then manufacturing tolerances are accommodated, but light is redirected to the optically black pixels causing inaccurate dark current measurements
Solution Approach 1:
A light-blocking structure is introduced as an intermediary element between the dummy pixels and the optically black pixels. This structure blocks light that would otherwise be redirected from the dummy pixels to the optically black pixels, thereby preventing inaccurate dark current measurements while preserving the dummy pixels' function for manufacturing tolerances
Solution Approach 2:
The region between the image pixel array and optically black pixels is segmented into dummy pixels and a light-blocking structure. This segmentation allows the dummy pixels to serve their manufacturing tolerance function while the light-blocking structure prevents light redirection, resolving the contradiction between accommodating manufacturing variations and maintaining measurement accuracy
2Measurement precision
If light-blocking structures are provided over optically black pixels, then accurate dark current measurements are enabled, but device complexity increases
Solution Approach 1:
The light-blocking structure is merged with existing structures in the image sensor, such as being integrated into the dummy pixel region or combined with other light-blocking elements. This merging approach enables accurate dark current measurements while minimizing the increase in device complexity by reusing existing structural elements rather than adding completely separate components
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
The implementation of light-blocking structures effectively prevents light from reaching optically black pixels, enhancing the accuracy of dark current measurements and noise compensation, thereby improving image sensor calibration and performance.
Implementation Method 1
light-blocking structures, such as metal light-blocking layers and black light shields, in both dummy and optically black pixels to prevent light from reaching the optically black pixels
Implementation Method 2
light that enters the image sensor through the dummy pixels may be redirected to the optically black pixels
Data Source
AI summary
An image sensor may include optically black pixels for obtaining dark current measurements. The image sensor may include dummy pixels between the active pixel array and the optically black pixels. Light incident upon the dummy pixels may be redirected to the optically black pixels, causing inaccurate dark current measurements. Light-blocking structures may be provided in the dummy pixels to prevent light from reaching the optically black pixels. A grid of openings may be formed in the active pixel array and the dummy pixel area. The grid may be filled with color filters in the active area and light-blocking elements in the dummy pixel area. The dummy pixel area may include a single opening in the grid in which a single light-blocking element that covers multiple dummy pixel photodiodes is formed. Light-blocking structures in the dummy pixel area may extend over the optically black pixels.