IR-cut filter switching control for camera mode transitions
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Solution Overview
Problem
Digital video cameras face issues with flickering images and unnecessary wear due to repeated switching between night mode and day mode, caused by misjudgment of visible light levels, especially when infrared light is present, leading to inefficient switching of the IR-cut filter.
Innovation Solution
A method in a video camera that measures ambient light intensity and color components, determines the set of illuminants, and compares them to characteristic values to accurately assess the proportion of IR light, allowing for informed decisions on switching between night and day modes by differentiating between IR and visible light intensities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the camera uses total ambient light intensity to control IR-cut filter switching, then the switching control is simple, but the visible light assessment is inaccurate leading to repeated switching between night mode and day mode
Solution Approach 1:
The patent segments the ambient light measurement into two distinct components: total light intensity measurement (for determining when switching should be considered) and visible light intensity measurement (for making the final switching decision). This is achieved by using the image sensor to capture total light and a separate auxiliary light sensor with IR-cut filter to measure only visible light, allowing the camera to assess both components independently and make accurate mode switching decisions based on visible light levels alone.
2Measurement precision
If the camera adds an auxiliary light sensor to measure visible light accurately, then the mode switching accuracy is improved, but the device complexity and cost increase
Solution Approach 1:
The patent introduces an auxiliary light sensor as an intermediary device that specifically measures visible light without being affected by infrared radiation. This auxiliary sensor acts as a mediator between the total light measurement and the mode switching decision, providing accurate visible light intensity data that enables precise control of the IR-cut filter while keeping the main image sensor dedicated to image capture.
3Manufacturing precision
If the camera switches to day mode when IR light proportion is high, then the color image quality improves, but the image becomes too dark due to blocking IR light
Solution Approach 1:
The patent replaces the simple mechanical threshold-based switching mechanism with an intelligent control system that calculates the proportion of infrared light in the ambient illumination. By using the auxiliary light sensor to measure visible light and comparing it with total light intensity, the system can determine IR light proportion and make informed decisions about when to activate the IR-cut filter, avoiding situations where switching would result in insufficient image brightness.
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 method reduces back-and-forth switching of the IR filter, improves image quality by ensuring accurate mode transitions, and extends the camera's operational lifespan by minimizing unnecessary mechanical stress.
Implementation Method 1
pixels of the image sensor will be able to detect the incident light as a charge on individual photodetectors
Implementation Method 2
The IR-cut filter stops the infrared portion of the incoming radiation from reaching the sensor
Data Source
AI summary
A method of performing better controlled switching between day mode and night mode imaging in a camera, where those illuminants contributing to the ambient light in day mode are considered when determining the visible light during night mode. Characteristic values of those illuminants are mixed with several levels of IR light to simulate the presence of an IR illuminator, and these characteristic values are compared to corresponding values derived from the color components of the ambient light in night mode in order to determine the IR proportion, and from that the amount of visible light.