Scaled Metal Reflectors for Image Sensor Light Collection
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Solution Overview
Problem
Conventional image sensors experience light loss and increased crosstalk at large chief ray angles, leading to decreased pixel response and noise due to inefficient light focusing onto photosensitive elements.
Innovation Solution
The implementation of metal reflectors with scaled widths, where the widths gradually decrease from the center to the edges of the image sensor array, allowing for improved light reflection and reduced crosstalk by optimizing the position and width of metal reflectors based on the chief ray angle and pixel coordinates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metal reflectors with uniform width are used across the image sensor array, then the manufacturing process is simple, but pixel response decreases and crosstalk increases at large chief ray angles
Solution Approach 1:
The patent applies local quality by varying the width of metal reflectors based on their position in the pixel array. Center pixels have wider metal reflectors while edge pixels have narrower metal reflectors. This localized adaptation optimizes light reflection for each region's specific chief ray angle requirements, improving pixel response and reducing crosstalk at large angles without compromising manufacturing feasibility
Solution Approach 2:
The patent changes the geometric parameter (width) of the metal reflectors based on their position in the array. By scaling the width parameter from center to edge, the system adapts the optical properties of the reflectors to compensate for varying chief ray angles, thereby maintaining consistent pixel response across the entire sensor array
2Device complexity
If metal reflectors with uniform width are used across the image sensor array, then the device structure is simple, but crosstalk increases at large chief ray angles
Solution Approach 1:
The patent implements local quality by making the metal reflector width a function of position. Edge pixels with larger chief ray angles receive narrower reflectors that prevent excessive light reflection and crosstalk, while center pixels receive wider reflectors for optimal light collection. This localized differentiation reduces crosstalk without significantly increasing overall device complexity
Solution Approach 2:
The patent introduces asymmetry by breaking the uniform width design. Instead of symmetric equal-width reflectors, the design uses asymmetric widths tailored to each pixel's position and angular characteristics. This asymmetric configuration optimizes light reflection patterns to minimize crosstalk at large chief ray angles
3Device complexity
If standard micro-lens focusing is used, then the optical system is simple, but light loss occurs at large chief ray angles
Solution Approach 1:
The patent introduces metal reflectors as intermediary elements between the micro-lens and photosensitive element. These reflectors intercept and redirect light that would otherwise be lost at large chief ray angles, funneling it back onto the photosensitive element. This intermediary structure reduces light loss without requiring complex optical system redesign
Solution Approach 2:
The patent replaces the need for complex adaptive optical systems with a static geometric solution. Instead of using movable or adjustable optical elements to track chief ray angles, the system uses fixed metal reflectors with optimized widths that passively redirect light based on their geometric configuration, reducing mechanical complexity while minimizing light loss
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 solution enhances the sensitivity of edge pixels, reduces crosstalk, and maintains high sensitivity at the center pixels, thereby improving the overall image sensor performance by ensuring more light is focused onto the photosensitive elements, even at larger angles.
Implementation Method 1
Metal reflectors are disposed on the substrate... light is reflected by the metal reflectors back onto the photosensitive elements
Data Source
AI summary
An image sensor in accordance with embodiments disclosed herein includes an array of imaging pixels, an insulator layer, and a plurality of metal reflectors. The array of imaging pixels are disposed within a semiconductor layer, where each imaging pixel in the array of imaging pixels includes a photosensitive element configured to receive light from a backside of the image sensor. The insulator layer is disposed on a frontside of the semiconductor layer and the plurality of metal reflectors are disposed within the insulator layer to reflect the light to a respective photosensitive element. A width of each of the plurality of metal reflectors is equal to a width of a metal reflector at the center of the array multiplied by a scaling factor, where the scaling factor is dependent on a distance of the metal reflector from the center of the array.