Image Pickup Apparatus Polarization Capture with Constant F-Number
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Solution Overview
Problem
Conventional image pickup apparatuses sacrifice resolution or chromatic information to obtain polarization information, and struggle with overexposure and underexposure issues, especially in scenes with backlight and low light conditions, leading to poor image quality.
Innovation Solution
An image pickup apparatus that captures multiple images in different polarization directions with varying exposure conditions while maintaining a constant F-number, using a polarization obtainer with a quarter waveplate, variable retardation plate, and polarizer to control polarization components, allowing for precise adjustment of exposure and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If multiple pixels are used to obtain polarization information, then polarization information can be extracted, but resolution and chromatic information are sacrificed
Solution Approach 1:
The patent divides the light into multiple polarization components using a polarization beam splitter, directing different polarization states to different imaging paths. This allows polarization information to be separated and captured without compromising the spatial resolution of the original image, as each polarization component is imaged separately rather than mixing multiple pixels for a single measurement point.
Solution Approach 2:
The patent adds a polarization dimension to the imaging system by capturing images with different polarization states (e.g., s-polarized and p-polarized light) separately. This dimensional separation allows the system to obtain polarization information as an additional parameter without reducing the spatial resolution in the original image plane, effectively adding information rather than trading it.
2Loss of information
If a wire grid polarizer is used to capture polarized light, then polarization information can be obtained, but exposure amount scatters and overexposure and underexposure occur
Solution Approach 1:
The patent segments the light path using a polarization beam splitter to separate s-polarized and p-polarized components into different imaging paths. Each path can then be independently exposed and controlled, allowing the system to capture polarization information without the exposure scattering problems that occur when using wire grid polarizers that affect all pixels simultaneously.
Solution Approach 2:
The patent employs dynamic control of exposure parameters for each polarization component separately. By adjusting exposure settings independently for different polarization paths, the system can optimize exposure quality for each component, preventing overexposure and underexposure issues that arise from fixed exposure settings in conventional polarized imaging.
3Measurement precision
If polarization filtering is applied to emphasize object features, then image quality is improved, but light quantity is reduced causing underexposure and noise
Solution Approach 1:
The patent segments the imaging process into multiple polarization channels, where each channel captures light with specific polarization characteristics. This segmentation allows the system to maintain higher light quantity in each channel compared to using strong polarization filters, while still obtaining polarization information through the combination of multiple channels.
Solution Approach 2:
The patent merges multiple polarization images captured with different polarization states to reconstruct the final image with enhanced quality. By combining information from multiple polarization channels rather than using aggressive polarization filtering, the system preserves more light quantity while still achieving the desired emphasis on specific object features through polarization-based image processing.
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 approach enables the acquisition of high-quality polarization information and images with reduced noise and exposure issues, allowing for accurate calculation of specular and diffuse reflection components, resulting in improved image quality across varying light conditions.
Implementation Method 1
a polarization obtainer 7 including a quarter waveplate 3, a variable retardation plate 4, and a polarizer 5
Implementation Method 2
a polarization obtainer 7 including a quarter waveplate 3, a variable retardation plate 4, and a polarizer 5
Implementation Method 3
a polarization obtainer 7 including a quarter waveplate 3, a variable retardation plate 4, and a polarizer 5
Data Source
AI summary
A control apparatus includes a controller configured to instruct an image pickup apparatus that includes an image pickup element configured to capture an image formed by an optical system to capture a plurality of images in different polarization directions, and to obtain polarization information based on the plurality of images. The controller instructs the image pickup apparatus to capture the plurality of images on exposure conditions different from one another while setting constant an F-number of the optical system.