Tile-Based Camera Mode Switching for False Trigger Prevention
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Solution Overview
Problem
Security cameras face challenges in reliably switching from Night mode to Day mode due to issues with detecting visible ambient light, leading to oscillations and false triggering by light sources like flashlights or car headlights, resulting in poorly illuminated images.
Innovation Solution
The implementation of a method using a combination of illuminant detection, lux level detection, and tiling to determine when to switch from Night mode to Day mode, involving a color sensor array with specific pixel configurations and a lens assembly to accurately assess ambient light components and adjust switching thresholds based on the type of light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the camera uses a simple light detection method to switch from Night mode to Day mode, then the switching is simple and fast, but it causes false triggering by narrow-beam light sources like flashlights or car headlights
Solution Approach 1:
The camera sensor array is divided into multiple tiles or regions, and the light detection is performed separately for each tile. By analyzing the spatial distribution of light across different tiles, the system can distinguish between broad ambient light (suitable for Day mode) and narrow-beam light sources (like flashlights or car headlights) that only illuminate specific areas. This segmentation prevents false triggering while maintaining relatively simple operation.
2Speed
If the camera switches to Day mode when detecting high IR light levels, then it responds quickly to light sources, but it oscillates between Night and Day modes when the light source provides high proportion of IR light
Solution Approach 1:
The system changes the detection parameters by using a color sensor array with multiple pixel types (first pixels with peak response at first frequency, second pixels with peak response at second frequency) to detect different components of ambient light. By analyzing the ratio or difference between light components at different frequencies, the system can determine whether the light source is suitable for Day mode operation, preventing oscillation while maintaining quick response to appropriate light conditions.
3Device complexity
If the camera uses a single lux threshold for mode switching, then the switching criterion is simple, but it cannot adapt to different illuminant color temperatures
Solution Approach 1:
The system uses a color sensor array with pixels having different peak responses at different visible light frequencies. By detecting and comparing the intensity of different light components (first light component from first pixels, second light component from second pixels), the system can determine the color temperature characteristics of the illuminant. This allows the camera to adapt its mode switching decision to different lighting conditions (e.g., warm incandescent light vs. cool daylight) while maintaining a relatively simple dual-threshold comparison approach.
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
This approach reduces oscillations between Night and Day modes, accurately identifies non-IR light sources, and ensures consistent lux level switching, preventing false Day mode activations and ensuring adequately illuminated images.
Implementation Method 1
a color sensor array comprising a plurality of sensor locations, the sensor locations including first, second and third pixels each having respective peak responses at different respective visible light frequencies
Implementation Method 2
a lens assembly that is configured to focus light on the sensor array
Data Source
AI summary
A method is executed at a camera operating in a night mode in which an IR filter is not interposed between a lens assembly and sensor arrays of the camera. In the night mode, the camera receives ambient light that is not filtered by the IR filter. For each image tile, the camera determines whether the ambient light received at the tile is due to an IR light source or a light source other than an IR light source and generates a respective mode change signal accordingly. A mode change parameter is then determined as a function of a total number of the mode change signals for image tiles of the camera. Based on the mode change parameter, the camera determines whether to continue the operation of the camera in the night mode or switch the operation of the camera from the night mode to a day mode.