Backlight Correction for Imaging Apparatus
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Solution Overview
Problem
Conventional imaging apparatuses fail to capture images of backlit scenes with both the person and sky regions having appropriate luminance levels, often resulting in unnatural luminance changes and overexposure of the sky region due to the lack of interrelated control between optical system and image processing units.
Innovation Solution
An imaging apparatus with an optical system, imaging unit, backlight correction unit, and control unit that performs tone conversion based on spatial position to increase luminance levels of dark regions while adjusting exposure light amounts to prevent sky region saturation, using interrelated control of optical and image processing units to achieve natural luminance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If exposure light amount is increased to brighten dark regions, then luminance level of dark regions is improved, but sky region becomes overexposed and loses tones
Solution Approach 1:
The patent applies local quality by implementing spatially selective tone conversion where different conversion characteristics are applied to different regions of the image. Dark regions use tone curves that increase luminance, while bright regions (sky) use tone curves that maintain or decrease luminance, allowing simultaneous optimization of both regions without uniform processing
Solution Approach 2:
The image is segmented into multiple regions based on luminance characteristics (dark regions, intermediate regions, bright regions). Each segment is processed independently with region-specific tone conversion characteristics, enabling differential control of luminance adjustment to prevent overexposure while brightening dark areas
2Object-affected harmful factors
If exposure light amount is decreased to prevent sky overexposure, then sky region tones are preserved, but dark regions become excessively dark
Solution Approach 1:
Different tone conversion characteristics are applied locally to different luminance regions. Bright regions use conservative tone curves to preserve details, while dark regions use aggressive tone curves to boost luminance, achieving balanced exposure across the entire image without uniform exposure adjustment
3Device complexity
If tone conversion is applied uniformly across the image, then processing simplicity is maintained, but natural luminance changes are lost and contrast is reduced
Solution Approach 1:
The patent implements spatially varying tone conversion where the conversion characteristic changes based on the luminance level and spatial position of each pixel. This local adaptation preserves natural luminance transitions and regional contrast while still using systematic tone curve methods, balancing processing efficiency with image quality
4Illumination intensity
If aperture is adjusted to control exposure, then overall exposure is controlled, but inability to independently control different regions' luminance levels is achieved
Solution Approach 1:
The patent replaces mechanical aperture control with digital tone conversion processing. Instead of using a single mechanical parameter (aperture) to control exposure, the system uses software-based tone curves that can independently adjust luminance for different spatial regions, providing finer granular control over exposure characteristics without physical mechanism limitations
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 effectively prevents sky region overexposure and enhances the luminance of person regions, resulting in images with appropriate luminance levels across all regions, perceived as naturally changing tones.
Implementation Method 1
an imaging unit, which reads an optical image of the subject that is formed with light focused by the optical system, and obtains the read optical image as an image signal
Data Source
AI summary
An imaging apparatus for capturing a moving image performs backlight correction of an image and outputs a natural image. The imaging apparatus electronically captures an image of a subject. An optical system has a light amount adjustment function. An imaging unit reads an optical image of the subject that is formed by the optical system. An A/D converter subjects an output of the imaging unit to A/D conversion. A backlight correction unit converts the tones of an image read by the A/D converter using a conversion characteristic selected differently according to a spatial position and at least increases the luminance level of a dark region of the image. An instruction unit instructs to start backlight correction. A control unit operates the backlight correction unit based on an instruction signal output from the instruction unit, and decreases an exposure light amount of the optical system by a predetermined amount.