LED Driver Notification Signal for Rolling Shutter Camera Stability
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Solution Overview
Problem
Digital cameras, especially those with rolling shutters, face issues with inconsistent illumination from LED light sources due to modulation, leading to unwanted effects like illumination artefacts in captured images, as the modulation frequency is high and not perceived by humans, affecting optimal iris and focus settings.
Innovation Solution
A method where a user device sends a notification signal to an LED light source to adjust its operating characteristic, allowing the camera to capture images with stable illumination, either by switching to a continuous mode or modifying the modulation pattern to mitigate these effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LED light source operates with modulated current to achieve desired illumination characteristic, then illumination intensity and color can be controlled, but illumination varies over time causing artefacts in captured images
Solution Approach 1:
The camera sends a notification signal to the LED light source before capturing the image, allowing the LED driver to adjust the current modulation in advance. This preliminary action ensures that the illumination remains stable during the actual image capture, preventing artefacts while still allowing modulated operation at other times.
Solution Approach 2:
The LED driver dynamically adjusts its operating mode based on received notification signals. When a notification is received, the driver modifies the current modulation characteristics; when no notification is received, the driver maintains normal modulated operation. This dynamic adaptation resolves the contradiction between needing modulation for illumination control and needing stability during image capture.
2Ease of operation
If LED light source uses high frequency modulation for dimming or VLC, then human observer does not perceive modulation, but rolling shutter camera captures varying illumination causing unwanted effects
Solution Approach 1:
The system performs preliminary detection of camera presence via notification signals before image capture. Upon detecting a camera, the LED driver temporarily adjusts its modulation frequency or duty cycle during the capture window, preventing artefacts while maintaining normal high-frequency modulation operation at other times for efficient dimming and VLC.
Solution Approach 2:
The LED driver changes operational parameters (frequency, duty cycle) based on the presence of a camera. When a camera is detected through notification signals, the driver modifies these parameters to eliminate artefacts; otherwise, it maintains the original parameters for normal dimming and VLC operation.
3Measurement precision
If camera performs measurements prior to capturing image, then optimal iris and focus settings can be derived, but measurements may be taken under different illumination conditions than actual capture
Solution Approach 1:
The camera sends a notification signal to the LED light source before performing measurements and before capturing the image. This ensures that the LED driver maintains consistent illumination characteristics throughout the entire process, from measurements to final capture, eliminating the discrepancy between measurement and capture conditions.
Solution Approach 2:
The system establishes a feedback loop where the camera communicates with the LED driver through notification signals. The LED driver adjusts its operation based on this feedback to maintain consistent illumination during both measurement and capture phases, ensuring that the illumination conditions remain reliable and consistent throughout the imaging process.
Data Source
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AI summary
A method of capturing an image of a scene using a user device having a rolling shutter camera is described, the scene being subjected to an illumination by an LED light source, the method comprising: providing, by the user device, a notification signal to the LED light source, the notification signal being indicative of a capturing or imminent capturing of an image; adjusting, by the LED light source, an operating characteristic of the LED light source, based on the notification signal; capturing, by the rolling shutter camera, the image of the scene, while the LED light source is operating at the adjusted operating characteristic.