Image Sensor Luminance Estimation for HDR Exposure Control
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Solution Overview
Problem
Existing image pickup apparatuses face challenges in capturing high-quality images of bright objects due to luminance saturation, where HDR bracket photographing requires multiple exposures and is time-consuming, especially in acquiring appropriate exposure values for bright objects.
Innovation Solution
An image pickup apparatus that estimates the luminance value of saturated pixels based on a single image and sets exposure parameters accordingly, allowing for quick and efficient HDR bracket photography by calculating an appropriate maximum exposure value using methods like differential and Poisson's equations to reconstruct pixel values in luminance-saturated regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If HDR bracket photographing is performed by repeatedly capturing images with different exposure values, then the luminance saturation is reduced and image quality is improved, but the time required for acquisition increases
Solution Approach 1:
The patent applies preliminary action by performing photometry and calculating the appropriate exposure value for bright objects before actually capturing the HDR images. This allows the system to pre-determine the exposure parameters needed, avoiding the need for repeated trial captures and significantly reducing the total acquisition time while maintaining image quality
2Measurement precision
If multiple images are captured with different exposure values to determine appropriate exposure, then the exposure accuracy is improved, but the number of operations and time required increases
Solution Approach 1:
The patent applies self-service by using the image sensor itself to perform photometry and calculate the appropriate exposure value, rather than requiring separate measurement operations. The system automatically processes the captured image data to determine exposure parameters, eliminating the need for manual intervention or additional specialized measurement devices, thus improving both accuracy and efficiency
3Productivity
If a single image is used to determine exposure value based on cumulative pixel value histogram, then the operation speed is improved, but the exposure accuracy for bright objects deteriorates
Solution Approach 1:
The patent applies the taking out principle by extracting and separately processing the luminance-saturated pixel regions from the overall image histogram analysis. Instead of relying solely on the cumulative histogram of all pixels, the system specifically identifies and analyzes saturated regions to determine the appropriate exposure value for bright objects, thereby maintaining both speed and accuracy
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 the generation of high-quality HDR images by quickly determining optimal exposure values, reducing the need for multiple exposures and improving image quality by minimizing luminance saturation and blocked-up shadows.
Implementation Method 1
an image sensor configured to photoelectrically convert an optical image formed via an image pickup optical system to output image data
Data Source
AI summary
An image pickup apparatus (10) includes an image sensor (102) which photoelectrically converts an optical image formed via an image pickup optical system to output image data, an estimator (104a) which estimates a luminance value of a saturated pixel of the image sensor based on a single image corresponding to the image data, a setter (104b) which sets an exposure parameter based on the luminance value, and a controller (107) which performs photography based on the exposure parameter.