Autoexposure Controller Flash Illumination Estimation

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Solution Overview

Problem

Cell phone cameras with LED flash systems face challenges in autoexposure control and white balance, particularly when switching from low-power to high-power flash modes, leading to potential overexposure and inappropriate white balance settings.

Innovation Solution

The method involves determining ambient and low-illumination exposure parameters to configure an autoexposure controller for high-illumination conditions, using a ratio of illuminance between low-power and high-power flash modes to adjust sensitivity parameters, which are then used for auto white balance prediction and image capture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If LED flash is driven in high-power mode continuously, then illumination intensity is improved, but power consumption increases and LED damage risk increases

Engineering Contradiction:

Improveflash illumination intensityVSAvoidpower consumption

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The LED flash is operated in periodic pulses rather than continuous high-power mode. The system uses short-duration high-power flash pulses combined with ambient light periods, allowing the LED to recover and reducing overall power consumption while maintaining sufficient illumination for image capture

Inventive Principle:

Principle #19Periodic action

2Illumination intensity

If LED flash is driven in high-power mode continuously, then illumination intensity is improved, but LED component damage risk increases

Engineering Contradiction:

Improveflash illumination intensityVSAvoidLED component reliability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The system employs periodic flash pulses with duty cycles that limit continuous high-power operation. By alternating between high-power illumination pulses and lower-power or ambient light periods, the LED experiences reduced thermal stress and extended operational reliability

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system预先 estimates exposure parameters and flash illumination effects before actual image capture. This allows the controller to adjust exposure settings and flash duration in advance, preventing overexposure and reducing the need for repeated high-power flash attempts that could damage the LED

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Use of energy by moving object

If autoexposure controller uses ambient illumination parameters, then power consumption is reduced, but illumination intensity is insufficient for low-light conditions

Engineering Contradiction:

Improvepower consumptionVSAvoidillumination intensity

Core Design Contradiction:

Use of energy by moving objectVSIllumination intensity

Solution Approach 1:

The autoexposure controller dynamically adjusts between ambient light mode and flash-assisted mode based on scene brightness requirements. In low-light conditions, the system activates flash with calculated exposure parameters, while in brighter conditions it relies on ambient light, creating a dynamic adaptation to lighting conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses feedback from scene analysis and preliminary exposure estimates to determine the appropriate balance between ambient light and flash illumination. The controller continuously monitors lighting conditions and adjusts flash activation and exposure settings accordingly

Inventive Principle:

Principle #23Feedback

4Loss of time

If flash illumination is not estimated before image capture, then processing time is reduced, but overexposure occurs

Engineering Contradiction:

Improveprocessing timeVSAvoidexposure accuracy

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

The system performs preliminary estimation of flash illumination effects and exposure parameters before actual image capture. This pre-calculation of exposure settings based on scene analysis allows the system to prevent overexposure while minimizing additional processing time during the actual capture moment

Inventive Principle:

Principle #10Preliminary action

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 prevents overexposure and ensures accurate white balance during high-power flash illumination, effectively estimating the combined illuminance from flash and ambient light for improved image capture.

Implementation Method 1

a second image frame brightness at the image sensor during the ambient illumination

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS8130313B2System and method to estimate autoexposure control and auto white balance

Publication Date: 2012.03.06 QUALCOMM INC

AI summary

In a particular embodiment, a method is disclosed that includes determining at least one ambient exposure parameter using an ambient illumination, the at least one ambient exposure parameter including a first sensitivity parameter of an autoexposure controller using the ambient illumination. The method includes determining at least one low-illumination parameter using a first lamp level, the at least one low-illumination parameter including a second sensitivity parameter of the autoexposure controller using the first lamp level, where the autoexposure controller is configured to operate according to at least one high-illumination parameter based on the at least one ambient exposure parameter and the at least one low-illumination parameter. The method further includes performing an image capture operation using a second lamp level that is brighter than the first lamp level, where the at least one high-illumination parameter includes a third sensitivity parameter.