Hybrid Image Sensor Filter Array for ToF and RGB Wavelength Separation
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Solution Overview
Problem
There is a lack of suitable optical filters that can effectively separate visible light for RGB pixels and infrared light for Time-of-Flight (ToF) pixels in integrated image sensors, leading to interference and noise in color image sensors and ToF cameras.
Innovation Solution
An optical filter array comprising a two-band passing filter and an infrared filter is used, allowing only infrared light to pass to the ToF pixel array, while the RGB pixel array is filtered for visible light, reducing interference and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single optical filter is used for both RGB and ToF pixels, then the device complexity is reduced, but the measurement precision and signal quality deteriorate due to wavelength interference and noise
Solution Approach 1:
The optical filter system is segmented into two distinct filters: a first optical filter for RGB pixels and a second optical filter for ToF pixels. This segmentation allows each filter to be optimized for its specific wavelength range, with the first filter transmitting visible light (400-700nm) and the second filter transmitting infrared light (700nm-1mm), thereby resolving the wavelength interference problem while maintaining manageable device complexity
Solution Approach 2:
Different optical filter properties are applied to different regions of the sensor array. The first optical filter is positioned over RGB pixels with characteristics optimized for visible light transmission, while the second optical filter is positioned over ToF pixels with characteristics optimized for infrared light transmission. This local differentiation ensures each pixel type receives appropriately filtered light without requiring a completely separate filtering system for each
2Ease of manufacture
If no optical filter is used, then the ease of manufacture is improved, but the reliability and signal quality worsen due to interference and noise from unwanted wavelengths
Solution Approach 1:
Optical filtering is performed preliminarily at the optical front end, before light reaches the photodetectors. The first and second optical filters are positioned in the light path to preemptively block unwanted wavelengths, preventing interference and noise from reaching the sensors in the first place. This preliminary action ensures high signal quality without requiring complex post-processing or additional manufacturing steps for the sensor elements themselves
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 enables the fabrication of a two-band pass filter array that minimizes interference and noise, allowing for effective separation of light wavelengths, enhancing the performance of integrated image sensors.
Implementation Method 1
an optical filter array including a two-band passing filter and an infrared filter; an RGB pixel array placed below the two-band passing filter; and a TOF pixel array adjacent to the RGB pixel array and placed below the two-band passing filter and the infrared filter
Implementation Method 2
Each of the unit pixels may include a photodiode and/or a plurality of transistors. The photodiode may detect external light and/or may generate and store charges
Data Source
AI summary
An image-sensing apparatus is provided. The image-sensing apparatus includes: an optical filter array including a two-band passing filter and an infrared filter; an RGB pixel array placed below the two-band passing filter; and a TOF pixel array adjacent to the RGB pixel array and placed below the two-band passing filter and the infrared filter, wherein a combination of the two-band passing filter and the infrared passing filter permits only the incident light in the infrared region to pass to the ToF pixel array.