Ambient Brightness Measurement Using Automatic Exposure
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Solution Overview
Problem
Conventional video surveillance equipment using photosensitive devices for measuring ambient brightness often results in high measurement errors and interference from visible light emitted by infrared fill-in devices, leading to low accuracy and uniformity issues.
Innovation Solution
A method and device that utilize the automatic exposure mechanism of a photographing device to calculate ambient brightness by obtaining exposure and image brightness values, with an automatic exposure enhancement coefficient, eliminating the need for photosensitive devices and minimizing visible light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photosensitive devices are used to measure ambient brightness, then the measurement function is achieved, but measurement precision and uniformity deteriorate due to high measurement error and interference from visible light emitted by infrared fill-in devices
Solution Approach 1:
The patent extracts the brightness measurement function from the photosensitive device and relocates it to the image sensor. By using the image sensor's automatic exposure mechanism, the measurement is performed on the actual captured image data rather than through a separate photosensitive component, thereby eliminating interference from infrared fill-in device light that affects the photosensitive device.
Solution Approach 2:
The image sensor is given a dual function: it serves both as the primary imaging component and as the brightness measurement device. The automatic exposure mechanism, originally designed for optimizing image quality, is repurposed to provide accurate ambient brightness measurements by analyzing the exposure parameters and image brightness values from the captured frames.
2Measurement precision
If photosensitive devices are used to measure ambient brightness, then the measurement function is achieved, but device complexity and manufacturing precision requirements worsen due to demanding optical design requirements
Solution Approach 1:
The image sensor performs both imaging and brightness measurement functions, eliminating the need for a separate photosensitive device and its associated complex optical design. The automatic exposure mechanism, already present in the photographing device, is utilized for measurement purposes, thereby simplifying the overall optical system.
Solution Approach 2:
The brightness measurement function is extracted from the optical system and integrated into the image processing domain. Instead of requiring dedicated photosensitive components with precise optical paths, the measurement is performed by analyzing exposure parameters and image brightness values from the captured frames through computational methods.
3Measurement precision
If photosensitive devices are used to measure ambient brightness, then the measurement function is achieved, but reliability worsens due to inconsistent measurement results among same-type equipment
Solution Approach 1:
By using the image sensor's automatic exposure mechanism for brightness measurement, the patent ensures that all equipment of the same type uses identical hardware and algorithms for measurement. This eliminates variations caused by differences in photosensitive device characteristics, optical designs, and manufacturing tolerances, thereby improving measurement uniformity across the product line.
Data Source
AI summary
The present disclosure provides a method for measuring an ambient brightness value, including: obtaining an exposure value of a photographing device during an automatic exposure process and an image brightness value corresponding to the exposure value; and determining an ambient brightness value based on the exposure value, the image brightness value, and an automatic exposure enhancement coefficient of the photographing device.