Optoelectronic Device Brightness Correction via Perspective Transformation
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Solution Overview
Problem
Existing image sensor systems face challenges in achieving homogeneous brightness distribution, leading to binarization problems and unreliable code reading, especially with camera tilts and edge energy decreases, which complicates code verification and reading applications.
Innovation Solution
An optoelectronic device with a brightness correction unit that calculates and applies correction factors based on perspective transformations to normalize brightness values, compensating for geometrical distortions and edge decreases, allowing for robust and independent code verification without the need for specialized calibration targets or known device properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tilted reading angle is used to reduce reflections from integrated illumination, then code reading reliability is improved, but perspective distortions and brightness gradients increase
Solution Approach 1:
The patent applies brightness correction by calculating correction factors based on perspective transformation parameters. The correction factors are derived from the transformation that converts geometries of the object plane into geometries of the image plane, effectively compensating for the brightness gradients caused by tilted reading angles.
Solution Approach 2:
Instead of mechanically adjusting the camera to achieve orthogonal viewing (which would eliminate perspective distortion but cause reflection problems), the patent uses computational image processing to correct the brightness distribution. The brightness correction unit processes the captured image to compensate for the effects of tilted viewing angles.
2Manufacturing precision
If orthogonal viewing is used to eliminate perspective distortions, then brightness distribution uniformity is improved, but direct reflections from integrated illumination increase
Solution Approach 1:
The patent calculates correction factors based on perspective transformation parameters that account for the tilted viewing angle. These correction factors are applied to compensate for both perspective distortions and reflection effects, allowing the system to maintain orthogonal viewing benefits while mitigating reflection problems through parameter-based correction.
3Manufacturing precision
If brightness correction based on mathematical models is used, then brightness normalization is achieved, but device complexity increases due to multiple unknown parameters
Solution Approach 1:
The patent extracts only the essential parameters needed for brightness correction from the complex mathematical model. Instead of accounting for all possible factors (illumination intensity, wavelength, transmission optics, mounting angle), the method focuses on deriving correction factors directly from the perspective transformation that converts object plane geometries to image plane geometries.
Solution Approach 2:
The brightness correction system uses the captured image itself and the known perspective transformation to automatically generate correction factors. The method does not require external calibration targets or manual parameter input - the system self-calibrates by utilizing the geometric relationship between object and image planes.
4Measurement precision
If calibration using special calibration targets is used, then brightness correction accuracy is improved, but additional components and setup steps are required
Solution Approach 1:
The patent makes the code itself serve as the calibration reference. The perspective transformation is determined by detecting the code geometry in the captured image and comparing it to the known code structure. This eliminates the need for separate calibration targets while maintaining high correction accuracy, as the code provides inherent geometric reference information.
Solution Approach 2:
The system performs self-calibration by using the code geometry detected in the captured image to determine the perspective transformation. No external calibration equipment or manual setup is needed - the system automatically derives the necessary correction parameters from the code itself, simplifying the overall process.
Data Source
AI summary
An optoelectronic device (10) is provided having an image sensor (20) for generating pixel images of a detection area (12) and a brightness correction unit (28) configured to modify brightness values of the pixels with a correction factor (Hmul) to obtain a more homogeneously illuminated image. A respective correction factor (Hmul) is calculated for individual pixels or groups of pixels from a perspective transformation (M) which converts geometries of an object plane (34) in the detection area (12) into geometries of the image plane (32).