Dual-Sensitivity Camera Noise Suppression for Code Reading
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Solution Overview
Problem
Conventional color line scan cameras suffer from a poorer signal-to-noise ratio compared to monochrome cameras due to color filters, which affects the quality of image data, especially in applications requiring high resolution like code reading.
Innovation Solution
A camera system with two recording channels of different sensitivities, where a noise suppression filter processes the second image data by weighting pixels based on their similarity to associated pixels in the first image data, effectively transferring the higher sensitivity and better signal-to-noise ratio from the first channel to the second channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If color filters are used in the image sensor to capture color images, then color information can be obtained, but the signal-to-noise ratio deteriorates due to light loss through the color filters
Solution Approach 1:
The image sensor is segmented into multiple recording channels, each with different spectral sensitivities (e.g., one channel sensitive to red light, another to blue light, and another to green light). This segmentation allows each channel to capture specific color information while maintaining higher photon yield compared to conventional single-color-filter approaches, thereby improving the signal-to-noise ratio for color imaging
Solution Approach 2:
Multiple recording channels with different spectral sensitivities are merged to capture color information. By combining the outputs of these channels (e.g., red-sensitive, blue-sensitive, and green-sensitive channels), the system reconstructs color images with improved signal-to-noise ratio, as each channel contributes photons from its optimized spectral range
2Reliability
If monochrome cameras are used to achieve the best signal-to-noise ratio, then high resolution and speed are obtained, but color information is lost
Solution Approach 1:
The imaging system achieves multi-functionality by simultaneously capturing both monochrome and color information using the same sensor platform. The multiple recording channels with different spectral sensitivities enable the system to function as both a high-performance monochrome camera (by combining all channels) and a color camera (by processing individual channels), eliminating the need to choose between signal-to-noise ratio and color information
3Reliability
If illumination intensity is increased to counteract the decreased signal-to-noise ratio in color images, then more photons are detected, but eye safety limits are reached
Solution Approach 1:
The system changes the spectral parameters of light detection by using multiple recording channels with different spectral sensitivities. Instead of increasing illumination intensity across all wavelengths, each channel detects photons in its optimized spectral range, effectively increasing the total photon yield without requiring higher illumination levels, thereby maintaining eye safety
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 improves the signal-to-noise ratio of color image data without losing spatial resolution, allowing for high-quality code reading and additional evaluations, similar to monochrome cameras, while maintaining the quality of grayscale image data.
Implementation Method 1
an image sensor having a first recording channel of a first sensitivity for recording first image data including first pixels and a second recording channel of a second sensitivity lower than the first sensitivity for recording second image data including second pixels
Data Source
AI summary
A camera includes an image sensor having a first recording channel of a first sensitivity for recording first image data including first pixels and a second recording channel of a second sensitivity lower than the first sensitivity for recording second image data including second pixels. The first pixels and second pixels are associated with one another by capturing a same object area. A control and evaluation unit processing the image data is configured to suppress noise effects in the second image data using a noise suppression filter that assigns a new value to a respective considered second pixel based on second pixels in a neighborhood of the considered second pixel. The noise suppression filter takes the second pixels in the neighborhood into account with a weighting that depends on how similar first pixels associated with the second pixels are to the associated first pixel of the respective considered second pixel.