Stacked Multispectral Image Sensor for Visible-IR Registration
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Solution Overview
Problem
Conventional silicon image sensors are ineffective beyond 1100 nm, as they become transparent, limiting their use in multispectral imaging applications that require simultaneous capture of visible and infrared data.
Innovation Solution
A stacked multispectral sensing device is developed, where a silicon die with sensor elements for wavelengths less than 1000 nm is bonded to a second die with IR-sensitive materials, allowing simultaneous capture of both spectral bands with shared optical aperture and readout circuitry for enhanced image registration and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional silicon image sensor is used, then visible light imaging is effective, but infrared imaging beyond 1100 nm is ineffective due to transparency
Solution Approach 1:
The sensor is divided into two separate silicon dies: the first die captures visible light (wavelengths less than 1000 nm) and the second die captures infrared light (wavelengths greater than 1000 nm). Each die is optimized for its specific spectral range, with the first die having high quantum efficiency for visible wavelengths and the second die being at least partially transmissive to infrared wavelengths while having high quantum efficiency for infrared detection.
Solution Approach 2:
The patent transitions from a single-plane sensor architecture to a stacked three-dimensional architecture. The second die is positioned behind the first die in the optical path, allowing both sensors to share the same optical aperture while capturing different spectral bands simultaneously. This vertical stacking enables multispectral imaging without requiring multiple separate sensors.
2Adaptability or versatility
If multiple separate image sensors are used for visible and infrared imaging, then spectral coverage is improved, but device complexity and alignment difficulty increase
Solution Approach 1:
The patent combines multiple imaging functions into a single integrated sensor stack. Both the visible light sensor (first die) and infrared sensor (second die) are bonded together in a fixed spatial relationship, sharing common optical aperture, focus, and readout circuitry. This merging eliminates the need for separate sensor housings, alignment mechanisms, and independent processing systems that would be required if multiple separate sensors were used.
Solution Approach 2:
The stacked sensor design creates a universal imaging device that can simultaneously perform visible light imaging, infrared imaging, and depth mapping functions. The shared optical aperture and coordinated readout system enable the device to capture multiple types of data (color images, depth maps, thermal information) in a single operation, making it applicable to diverse imaging scenarios including 3D reconstruction, augmented reality, and surveillance.
3Adaptability or versatility
If separate sensors capture visible and infrared images, then spectral data is obtained, but image registration accuracy deteriorates
Solution Approach 1:
By stacking the sensors in the vertical dimension rather than placing them side-by-side in the horizontal plane, the patent ensures that both sensors view the scene from exactly the same optical perspective. The second die is positioned directly behind the first die, sharing the same optical aperture and focal plane, which eliminates parallax errors and enables pixel-perfect alignment between visible and infrared images without requiring complex software registration algorithms.
4Measurement precision
If a stacked sensor design is used, then image registration is improved, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates alignment marks and registration features directly into the sensor die structure during the semiconductor fabrication process, before the dies are bonded together. These pre-formed alignment structures enable precise registration of the stacked dies during assembly, reducing the complexity of the bonding process. The alignment marks are automatically detected and used to guide the bonding process, ensuring accurate spatial registration without requiring complex external alignment equipment or manual adjustment.
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
Enables compact, high-quality 3D color imaging by effectively capturing visible and infrared data simultaneously, improving image registration and sensitivity across the spectral range.
Implementation Method 1
a first array of first sensor elements configured to output first electrical signals in response to optical radiation that is incident on the device in a first band of wavelengths less than 1000 nm
Implementation Method 2
a second array of second sensor elements configured to output second electrical signals in response to the optical radiation that is incident on the device in a second band of wavelengths greater than 1000 nm that passes through the first die
Data Source
AI summary
A multispectral sensing device includes a first die, including silicon, which is patterned to define a first array of sensor elements, which output first electrical signals in response to optical radiation that is incident on the device in a band of wavelengths less than 1000 nm that is incident on the front side of the first die. A second die has its first side bonded to the back side of the first die and includes a photosensitive material and is patterned to define a second array of sensor elements, which output second electrical signals in response to the optical radiation that is incident on the device in a second band of wavelengths greater than 1000 nm that passes through the first die and is incident on the first side of the second die. Readout circuitry reads the first electrical signals and the second electrical signals serially out of the device.