Assist Light Periodic Control for Autofocus in Low Light
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Solution Overview
Problem
Existing digital photographing devices face challenges in achieving reliable autofocus in low light conditions due to power and heat constraints, as current solutions like PWM dimming do not provide sufficient brightness for the assist light, impacting autofocus performance.
Innovation Solution
The assist light is controlled to be active only during a specific part of the image frame, known as the window of interest, allowing it to cool down during the rest, thereby optimizing power usage and increasing brightness for autofocus calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the assist light is powered with small amount of power to reduce power consumption and heat generation, then power efficiency is improved, but the light brightness becomes insufficient for reliable autofocus
Solution Approach 1:
The assist light is activated periodically only during the exposure period of the window of interest rather than continuously. The control unit turns on the assist light when the shutter exposes the window of interest and turns it off during other periods, creating a periodic on-off pattern that matches the exposure timing. This periodic operation reduces overall power consumption while ensuring sufficient brightness during critical autofocus exposure moments.
Solution Approach 2:
The system determines the window of interest and its exposure timing in advance before actually exposing the image frame. Based on this preliminary determination, the control unit pre-configures when the assist light should be activated. This preliminary planning ensures the assist light is ready to provide necessary illumination exactly when needed for autofocus calculations, maintaining reliability while optimizing power usage.
2Reliability
If the assist light operates continuously to provide sufficient brightness for autofocus, then autofocus reliability is improved, but heat generation increases
Solution Approach 1:
The assist light operates periodically rather than continuously, being activated only during the exposure period of the window of interest. This periodic operation pattern allows the light-emitting component to cool down during non-exposure periods while maintaining necessary brightness during exposure moments, effectively managing heat generation without compromising autofocus reliability.
3Use of energy by moving object
If PWM dimming is used to reduce power to the assist light, then power consumption is reduced, but light brightness becomes insufficient for reliable autofocus
Solution Approach 1:
Instead of using PWM dimming that reduces overall power, the system uses periodic full-power activation synchronized with exposure timing. The assist light receives full power during the brief exposure period when it is needed, and zero power during non-exposure periods. This approach maintains maximum illumination intensity during critical moments while achieving power reduction through time-based control rather than intensity-based dimming.
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 enhances autofocus reliability in low light conditions while reducing power consumption and heat generation, enabling the use of smaller devices with improved autofocus performance.
Implementation Method 1
an assist light that illuminates the object being photographed in low light conditions
Implementation Method 2
An example of the method comprises exposing an image frame comprising a window of interest
Data Source
AI summary
Digital photographing devices traditionally comprise an assist light that illuminates the object being photographed in low light conditions The solution concerns a method comprising exposing an image frame comprising a window of interest; performing an autofocus for the window of interest; and controlling an assist light for the autofocus according to an exposure of the window of interest. The solutions is also targeted to an apparatus and a computer-readable storage means.