Rectilinear Pixel Grid with Radially Scaled Photosensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS imaging devices suffer from lens shading, where pixels farther from the optical axis receive less light, leading to darker corners in images, and existing solutions require post-readout processing or special acquisition techniques to correct this issue.
Innovation Solution
Modifying the size of pixel photosensors according to their spatial location in the array, with pixels farther from the optical axis having larger photosensors, thus adjusting pixel size and shape to compensate for varying light intensity, maintaining a rectilinear or curved grid layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pixels are identically sized and spaced in a conventional grid, then manufacturing is simple and consistent, but lens shading occurs causing darker corners and reduced image quality
Solution Approach 1:
The patent applies local quality by making pixel photosensors have different sizes based on their spatial location in the array. Pixels farther from the optical axis have larger photosensor areas to compensate for reduced light intensity, while central pixels maintain smaller sizes. This localized variation in photosensor area corrects lens shading effects and achieves uniform image brightness across the field of view.
2Manufacturing precision
If post-readout processing is used to correct lens shading, then image brightness uniformity can be improved, but processing time and complexity increase
Solution Approach 1:
The patent implements preliminary action by correcting lens shading at the hardware level through non-uniform photosensor sizing before image acquisition. The varying photosensor areas are designed into the pixel array structure itself, enabling optical compensation to occur during the exposure process rather than requiring subsequent digital post-processing. This eliminates time-consuming post-readout operations while achieving uniform image brightness.
3Manufacturing precision
If pixel photosensor sizes are varied by spatial location, then lens shading is corrected and image quality improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies parameter changes by systematically varying the photosensor area parameter as a function of spatial position in the pixel array. Specifically, photosensor area increases with distance from the optical axis according to a defined relationship that compensates for cosine roll-off and lens shading. This controlled parameter variation achieves brightness uniformity while maintaining a regular rectilinear grid layout, balancing performance improvement with manufacturing feasibility.
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 effectively corrects lens shading and other spatial optical effects without the need for post-processing, ensuring consistent brightness across the image array by proportionally increasing photosensor size with distance from the optical axis, thereby reducing spatial distortion and enhancing image quality.
Implementation Method 1
each one of the pixels including a photosensor, for example, a photogate, photoconductor or a photodiode overlying a substrate for accumulating photo-generated charge
Data Source
AI summary
Pixels in an imaging device pixel array are sized according to their geographic location in the pixel array to compensate for various optical characteristics/issues. In one example, pixel size is increased according to the distance of the pixel from the x-axis and/or the y-axis of the pixel array to correct for lens shading.