Adaptive Tone Curve Synthesis for Vehicle Camera Luminance
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Solution Overview
Problem
Existing image processing systems for vehicle-mounted cameras struggle to maintain accurate gradation conversion across varying lighting conditions throughout the day and different environments, leading to unsettling image distortions, especially during transitions like entering a tunnel or underground parking.
Innovation Solution
An image processing device that selects and synthesizes multiple time-specific and illumination-specific conversion functions based on captured time and environmental conditions to adjust image luminance, using a combination of global and local tone curves to generate a synthesized function for optimal gradation conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single global tone mapping tone curve is used for gradation conversion, then the processing is simple and fast, but the image quality becomes unnatural when illumination conditions change (e.g., entering a tunnel or underground parking)
Solution Approach 1:
The patent applies dynamics by making the tone curve selection adaptive rather than static. The system dynamically switches between different tone curves based on detected illumination conditions (bright, standard, dark environments). This allows the gradation conversion to adapt to changing lighting conditions in real-time, resolving the contradiction between processing simplicity and image quality consistency.
Solution Approach 2:
The patent changes the parameter of tone curve selection based on illumination detection. By detecting the brightness level of the captured image and selecting appropriate tone curves (first for bright, second for standard, third for dark environments), the system optimizes gradation conversion for different lighting conditions without requiring complex processing algorithms.
2Reliability
If multiple tone curves corresponding to different illumination conditions are selected, then the image quality adapts to environment, but unsettling feelings occur during transitions between different time bands or locations
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple tone curves for different illumination conditions (bright, standard, dark) and having the system ready to switch between them based on detected environment. This preparation allows smooth transitions without unsettling visual effects, as the appropriate tone curve is already available when illumination conditions change.
Solution Approach 2:
The system uses feedback by continuously detecting the illumination conditions of captured images and automatically selecting the appropriate tone curve based on the detected brightness level. This closed-loop approach ensures that the gradation conversion always matches the current environmental conditions, providing visual comfort during transitions between different locations or time bands.
3Measurement precision
If tone curve selection is based on illumination detection, then the gradation conversion matches the environment, but mismatches occur during transitions through tunnels or underground parking
Solution Approach 1:
The patent applies segmentation by dividing the tone curve selection into distinct categories based on illumination levels (bright, standard, dark environments). By segmenting the tone curves into three specific types and selecting based on detected conditions, the system provides accurate gradation conversion for each environment type while maintaining reliability during transitions between them.
Data Source
AI summary
An image processing device includes a memory, and a processor coupled to the memory, the processor is configured to: acquire an image aiding a field of view of a driver of a vehicle, and time information of a point in time when the image was captured; select, from a plurality of conversion functions that convert luminance of the image using mutually different characteristics and that include two or more time band specific conversion functions determined specifically for time bands in a one day period, two or more of the conversion functions including at least one of the two or more time band specific conversion functions according to the time information; generate a synthesized function using the two or more conversion functions selected; and convert the luminance of the image using the synthesized function.