Image Sensor Pixels with Tuned Microlenses to Reduce Color Aliasing
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Solution Overview
Problem
Conventional CMOS image sensors with RGBC patterns suffer from color aliasing due to the alignment of clear filters, which leads to incorrect color representation in images, as clear pixels do not produce color information and are prone to optical crosstalk.
Innovation Solution
Increasing optical crosstalk between pixels by adjusting the height, effective focal depth, and curvature of microlenses, as well as varying the junction depth of photodiodes, to intentionally direct light from one pixel to its neighbors, thereby blending colors and reducing color aliasing effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If clear pixels are included in the color filter array to increase sensitivity, then the sensitivity of the image sensor is improved, but color aliasing occurs due to the alignment of clear filters
Solution Approach 1:
The patent converts the harmful optical crosstalk between pixels into a beneficial effect by intentionally designing microlenses with specific curvatures and focal depths that direct light from clear pixels to adjacent color pixels. This intentional crosstalk allows clear pixels to contribute their intensity information to neighboring color pixels, enabling color reconstruction while maintaining the sensitivity benefits of clear pixels without suffering from color aliasing
2Loss of information
If microlenses are designed with specific curvature and focal depth to increase optical crosstalk, then color aliasing is reduced by blending colors, but the device complexity increases
Solution Approach 1:
The patent applies local quality by designing different microlens curvatures and focal depths for different pixel locations within the array. Specifically, microlenses corresponding to clear pixels are designed with different optical properties than those for color pixels, allowing precise control of light distribution patterns. This localized differentiation enables the complex crosstalk management to be implemented in a targeted manner, improving color accuracy while managing overall device complexity
Solution Approach 2:
The patent utilizes parameter changes by systematically varying microlens curvature radii and focal depths across the pixel array. By adjusting these optical parameters, the design optimizes the balance between achieving sufficient optical crosstalk for color blending and maintaining manufacturability. The specific parameter values are chosen to achieve the desired light distribution while avoiding excessive complexity
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 intentional increase in optical crosstalk between pixels effectively reduces color aliasing by blending colors, improving the accuracy of color representation in images without excessive distortion.
Implementation Method 1
adjusting the height, effective focal depth, and curvature of microlenses, as well as varying the junction depth of photodiodes, to intentionally direct light from one pixel to its neighbors
Data Source
AI summary
An image sensor includes a first pixel and a second pixel. The first pixel includes a first light sensitive element, a first light filter, and a first microlens. The second pixel is disposed adjacent to the first pixel and includes a second light sensitive element, a second light filter, and a second microlens. The first pixel is configured to direct at least some of the light received at the first microlens to the second light sensitive element of the second pixel to increase optical crosstalk so as to reduce color aliasing.