Automatic Exposure Compensation Using Shutter-Closing Curve
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Solution Overview
Problem
Current automatic exposure methods in digital cameras often result in overexposure when taking photographs in bright environments due to inadequate shutter speed, as they fail to accurately compensate for environmental brightness.
Innovation Solution
An automatic exposure compensation method and system that activates a shutter, detects environmental brightness, calculates an exposure value, and adjusts the exposure time based on a shutter-closing curve to either advance or postpone the exposure signal, ensuring the exposure time is corrected to prevent over or underexposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the shutter speed is set to the maximum speed (1/500 seconds) for bright environments, then the exposure time is reduced, but overexposure still occurs because the shutter closing time is insufficient
Solution Approach 1:
The patent applies preliminary action by pre-calculating the shutter closing time curve and storing it in the system. Before taking a photograph, the controller retrieves the required closing time from this pre-computed curve based on the aperture value and exposure value, rather than calculating it in real-time during exposure. This allows the system to compensate for the mechanical shutter's finite closing time by adjusting the exposure time signal in advance, ensuring accurate exposure even at maximum shutter speeds.
2Manufacturing precision
If the exposure time is extended to compensate for shutter closing time, then exposure accuracy improves, but the original exposure settings (aperture, ISO, scene depth) are altered
Solution Approach 1:
The patent segments the exposure control into two independent parts: the mechanical shutter closing time (determined by aperture and exposure value via the pre-computed curve) and the exposure time signal duration. By separating these functions, the system can adjust the exposure time signal duration to compensate for shutter closing time without changing the aperture setting or ISO value, thus maintaining the original exposure settings while achieving accurate exposure.
3Manufacturing precision
If a pre-computed shutter closing time curve is used for compensation, then exposure compensation accuracy improves, but the system complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing the shutter closing time curve in a lookup table format before operation. The curve, which relates aperture values and exposure values to required shutter closing times, is calculated in advance and stored in memory. During actual photographing, the controller simply retrieves the appropriate closing time from this pre-computed data based on the current aperture and exposure values, avoiding complex real-time calculations and reducing system complexity while maintaining high accuracy.
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 solution ensures accurate exposure by dynamically adjusting exposure time, preventing over or underexposure in varying brightness conditions, thereby maintaining optimal image quality without altering the original scene depth or ISO settings.
Implementation Method 1
A shutter is activated and the environmental brightness is detected using a sensor
Data Source
AI summary
A method for automatic exposure compensation is disclosed. A shutter is activated and the environmental brightness is detected using a sensor. An exposure value is calculated according to the detection result to obtain a default exposure time. It is determined whether the exposure value is equal to a normal value. If not, a compensation value is calculated based on a shutter-closing curve and a compensation operation is thus executed. Thus, an exposure signal is generated by advancing a first predefined time or postponing a second predefined time, enabling the amount of exposure time to be equal to the addition or subtraction of the default exposure time and the first predefined time.