Light Guide Members in Image Sensors
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Solution Overview
Problem
Image sensors used in cameras and camcorders face light loss due to absorption and reflection at the interfaces of stacked thin films, which reduces the amount of light reaching the photodiode, especially in low environmental brightness conditions.
Innovation Solution
Incorporating a light guide member made of transparent materials with a refractive index of 1.8 to 2.3, such as ITO, IZO, silicon oxide, or titanium oxide, between color filters and photodiodes to minimize light loss by guiding incident light through total reflection, and using a silicon substrate with overlapping photodiodes and organic semiconductor layers for enhanced light sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If various thin films are stacked in an image sensor, then the image sensor can perform color separation and photoelectric conversion, but light is absorbed by the thin films and reflected at the interface between the thin films, causing light loss before reaching the photodiode
Solution Approach 1:
A light guide member made of transparent material (such as silicon oxide, titanium oxide, ITO, or IZO) with appropriate refractive index is introduced as an intermediary component between the color filter and the photodiode. This light guide member guides the light that has passed through the color filter to the photodiode while minimizing absorption and reflection losses, thereby resolving the contradiction between achieving color separation through multiple thin films and reducing light loss.
2Loss of energy
If a light guide member is introduced to reduce light loss, then light transmission efficiency improves, but the device structure becomes more complex
Solution Approach 1:
The light guide member is formed by changing the refractive index parameter of the material layer. By selecting transparent materials with specific refractive indices (such as silicon oxide, titanium oxide, ITO, or IZO) and controlling their thickness and optical properties, the light guide member can effectively guide light with minimal loss. This approach achieves improved light transmission efficiency while keeping the structural complexity manageable through material parameter optimization rather than adding complex mechanical structures.
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 effectively reduces light loss and improves the sensitivity of image sensors by ensuring that red and blue light is guided to the photodiodes without deviation, enhancing the ability to capture images in low-light environments.
Implementation Method 1
incorporating a light guide member made of transparent materials with a refractive index of 1.8 to 2.3, such as ITO, IZO, silicon oxide, or titanium oxide, between color filters and photodiodes to minimize light loss by guiding incident light through total reflection
Implementation Method 2
the image sensor separates incident light into three primary colors of red, green, and blue and converts each of them into an electrical signal... senses the light by using a photodiode reacting to one color of the three primary colors
Data Source
AI summary
Image sensors include a color photo-sensing photoelectric conversion device, a first color filter and a second color filter disposed under the color photo-sensing photoelectric conversion device, a first photodiode and a second photodiode disposed under the first color filter and the second color filter, respectively, a first light guide member disposed between the first color filter and the first photodiode, and a second light guide member disposed between the second color filter and the second photodiode.