High Frame Rate Image Signal Processing for Flicker Detection
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Solution Overview
Problem
High frame rate cameras struggle to accurately check and display flicker in captured images, especially under blinking light sources, as existing methods either lose luminance differences or fail to express flicker correctly, requiring time-consuming recording and reproduction of image signals for flicker correction.
Innovation Solution
An imaging device with an image signal processing unit that generates a display image signal of a standard frame rate by frame thinning from a higher frame rate, determining the frames to be thinned based on the relationship between the frame rate and light source frequency, allowing for real-time flicker checking and correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frame addition method is used to generate monitor output, then high S/N ratio is achieved, but luminance difference is lost and flicker cannot be correctly expressed
Solution Approach 1:
The patent extracts only the necessary frames from the high frame rate sequence to create the monitor output. By selecting specific frames based on the thinning ratio, the luminance differences corresponding to light source blinking cycles are preserved in the down-sampled sequence, enabling flicker detection while reducing frame count.
Solution Approach 2:
The patent applies preliminary frame selection based on the relationship between frame rate and light source frequency before display. By calculating the appropriate thinning ratio and selecting frames in advance, the system ensures that luminance variations due to flicker are captured in the monitor output, allowing real-time flicker checking without post-processing.
2Productivity
If frame thinning is applied to reduce frame rate, then real-time monitoring is enabled, but flicker accuracy deteriorates without proper frame selection
Solution Approach 1:
The patent changes the frame rate parameter by applying a specific thinning ratio derived from the relationship between the second frame rate and light source frequency. This parameter transformation allows the system to operate at a lower effective frame rate for monitoring while preserving flicker information through mathematically determined frame selection.
Solution Approach 2:
The patent utilizes the periodic nature of light source blinking by selecting frames at intervals that correspond to the light source frequency. The thinning ratio is calculated to ensure that frames capturing luminance variations at the blinking period are retained, creating a periodic sampling pattern that preserves flicker characteristics.
3Measurement precision
If recording and reproduction of image signals is performed for flicker checking, then flicker correction can be checked, but time and effort are consumed
Solution Approach 1:
The patent enables the imaging device to perform self-diagnosis of flicker by incorporating the frame thinning function directly into the monitor output generation. The device checks its own captured images for flicker in real-time without requiring external recording and reproduction operations, making the flicker verification process efficient and integrated.
Solution Approach 2:
The patent introduces a frame thinning function as an intermediary process between image capture and display. This intermediary function processes the high frame rate images to create a down-sampled monitor output that preserves flicker information, serving as a mediator that enables real-time flicker checking without requiring full-resolution recording and reproduction.
Data Source
AI summary
This invention enables one to check flicker of a HFR image signal. A display image signal of a first frame rate for flicker check is obtained on the basis of an image signal of a second frame rate. For example, the display image signal of the first frame rate is generated from the image signal of the second frame rate by a frame thinning process. In this case, a frame to be thinned is determined from a relationship between the second frame rate and a light source frequency. For example, the number of frames to be a flicker period is obtained from the second frame rate and the light source frequency, and the frame to be thinned is determined so that continuous frames of the number of frames to be the flicker period are present.