Image Sensor Dishing Structure for Lens Shading Compensation
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Solution Overview
Problem
Conventional digital imaging apparatuses suffer from a lens shading effect, where the peripheral image is significantly darker than the central image due to non-uniform photo-response caused by increased chief-ray angles, which is exacerbated by demands for lighter, thinner, and smaller devices.
Innovation Solution
An image sensor structure with a substrate, sensor array, dielectric layer, under layer with a higher refractive index than the dielectric layer, filter array, and microlens array, where the under layer fills a dishing structure in the dielectric layer to act as a convex lens and compensate for focal length differences, ensuring uniform photo-response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the focal length is shortened to make devices lighter and thinner, then the device size and weight are reduced, but the chief-ray angle increases causing significant lens shading effect
Solution Approach 1:
The patent applies local quality by creating a dishing structure in the dielectric layer with varying depth across the sensor surface. The dishing depth increases from the center toward the periphery, allowing different regions to compensate for their specific chief-ray angle conditions. This localized structural modification enables uniform photo-response across the entire sensor array while maintaining the shortened focal length required for compact device design.
Solution Approach 2:
The patent introduces a new dimensional feature by forming a dishing structure that adds vertical depth variation to the otherwise planar dielectric layer. This third-dimensional modification (creating a concave surface profile) allows the system to compensate for optical path differences caused by oblique light rays, effectively addressing the shading effect without increasing device thickness in the primary direction.
2Illumination intensity
If microlenses or color filters are shifted to compensate for shading effect, then peripheral brightness is improved, but the compensation is spatially limited and insufficient at greater chief-ray angles
Solution Approach 1:
The patent changes the geometric parameter of the dielectric layer by forming a dishing structure with controlled depth variation. This parameter modification (creating a concave profile with specific depth gradients) fundamentally alters the optical path lengths for light rays across the sensor surface, providing continuous compensation for chief-ray angle effects rather than discrete positional shifts.
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 solution achieves uniform brightness across the image by compensating for focal length differences, reducing the lens shading effect and ensuring consistent photo-response across the image sensor, even at increased chief-ray angles.
Implementation Method 1
an under layer filled into the dishing structure and having a refraction index greater than that of the dielectric layer
Data Source
AI summary
A method for making the image sensor structure, for avoiding or mitigating lens shading effect. The image sensor structure includes a substrate, a sensor array disposed at the surface of the substrate, a dielectric layer covering the sensor array, wherein the dielectric layer includes a top surface having a dishing structure, an under layer filled into the dishing structure and having a refraction index greater than that of the dielectric layer, a filter array disposed on the under layer corresponding to the sensor array, and a microlens array disposed above the filter array. A top layer may be additionally disposed to cover the filter array and the microlens array is disposed on the top layer.