Multispectral HDR Imaging With Per-Channel Exposure Equalization
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Solution Overview
Problem
Existing imaging technologies face challenges in achieving high dynamic range imaging (HDR) due to varying transmission efficiency and quantum efficiency across different wavelength channels, leading to saturation issues and difficulty in capturing a wide range of lighting conditions, especially with multispectral imaging (MSI) sensors.
Innovation Solution
An image acquisition apparatus with a multispectral imaging sensor that sets exposure times for each channel based on transmission efficiency and quantum efficiency, generating HDR images by adjusting exposure times and quantum efficiency values to equalize signal magnitudes across channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single exposure time is used for all wavelength channels in multispectral imaging, then the device complexity is reduced, but some channels become saturated while others are underexposed due to varying transmission efficiency and quantum efficiency
Solution Approach 1:
The patent divides the imaging system into multiple wavelength channels (e.g., 4×4 array with 16 channels), and assigns a dedicated exposure time to each channel based on its specific transmission efficiency and quantum efficiency characteristics. This segmentation allows each channel to be optimized independently, preventing saturation in high-efficiency channels while ensuring sufficient exposure in low-efficiency channels.
Solution Approach 2:
The patent applies different exposure time parameters to different wavelength channels according to their local efficiency characteristics. By calculating QE×TE values for each channel and setting exposure times proportionally, the system achieves uniform signal magnitudes across all channels, optimizing image quality locally for each channel rather than using a uniform global parameter.
2Illumination intensity
If multiple images with different exposure times are captured sequentially for HDR imaging, then the dynamic range is improved, but the imaging speed decreases and dynamic objects cannot be captured effectively
Solution Approach 1:
The patent pre-calculates the optimal exposure time for each wavelength channel based on the known QE×TE characteristics before actual imaging. This preliminary configuration of per-channel exposure times allows the system to capture all necessary exposure variations in a single simultaneous shot across all channels, eliminating the need for sequential multi-shot HDR capture and enabling effective imaging of dynamic objects.
3Illumination intensity
If the exposure time is increased to capture dark objects, then the signal from dark regions is improved, but bright objects become saturated
Solution Approach 1:
The patent segments the imaging task by wavelength channel, recognizing that different channels have different efficiency characteristics. By assigning longer exposure times specifically to channels with lower QE×TE values (which correspond to wavelengths where the sensor is less efficient), the system can capture dark regions in those channels without needing to increase the exposure time for all channels, thus preventing saturation in high-efficiency channels.
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 generation of stable HDR images, even with dynamic objects, by equalizing QE×TE values across channels, thereby improving image capture in varied lighting conditions.
Implementation Method 1
A spectral filter including an multispectral imaging (MSI) sensor has a Fabry-Perot cavity structure that uses resonance caused by a specific wavelength of light between two reflectors to generate an image composed of only a specific wavelength band.
Implementation Method 2
A spectral filter including an multispectral imaging (MSI) sensor has a Fabry-Perot cavity structure
Implementation Method 3
An imaging sensor is an apparatus that receives light incident from an object and photoelectrically converts the received light to generate electrical signals.
Data Source
AI summary
An image acquisition apparatus includes a multispectral imaging sensor for acquiring images of at least four channels based on a wavelength band of about 10 nm to about 1000 nm and a processor for setting an exposure time for each of the four channels based on transmission efficiency and quantum efficiency for each wavelength of each of the four channels and generating an HDR image using image signals corresponding to the four channels and obtained according to the set exposure time.