LED Row Illumination for Homogeneous Wide-Product Inspection
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Solution Overview
Problem
Existing inspection systems for analyzing defects in products like printed circuit boards are inefficient for wide products, as they require multiple scans and are prone to errors due to insufficient illuminance and inhomogeneous light distribution, leading to time-consuming and unreliable defect detection.
Innovation Solution
The system employs a projection device with a row of light-emitting diodes and an exit aperture extending along the row, providing a homogenous light distribution and high luminous flux, allowing for a single, reliable scan of wide products by shifting the reflected image based on height variations, which can be detected by a camera to calculate surface height information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple point light sources are used to increase luminous flux, then the illuminance on the product increases, but image defects and diffraction phenomena occur
Solution Approach 1:
The continuous light source is segmented into multiple discrete LED elements arranged in a row, where each LED emits light that is individually controlled and positioned. This segmentation allows high luminous flux to be achieved through multiple sources while avoiding the image defects and diffraction phenomena associated with traditional point light sources, as each LED's light path can be precisely controlled and positioned.
Solution Approach 2:
Traditional mechanical or optical systems for generating light (such as fluorescent tubes or single point sources) are replaced with a solid-state LED array. This substitution enables precise control of light emission, providing high luminous flux without the mechanical limitations and optical defects of previous systems, thereby improving both illumination intensity and image quality.
2Area of stationary object
If the inspection system is widened to inspect wider products, then the inspection width increases, but multiple scans are required making it time-consuming
Solution Approach 1:
Multiple LED light sources are merged into a single continuous row that illuminates the entire inspection width simultaneously. This merging of light sources allows the system to inspect wide products in a single scan without requiring multiple sequential scans, thereby increasing inspection width while reducing scan time.
Solution Approach 2:
The inspection system transitions from a narrow, sequential scanning approach to a wide, parallel illumination approach. By arranging LED sources in a row that spans the entire inspection width, the system illuminates the entire product width simultaneously, enabling single-pass inspection of wide products and eliminating the time loss associated with multiple scans.
3Area of stationary object
If fluorescent tubes are used as illuminants, then the inspection width can be increased, but the luminous flux is insufficient
Solution Approach 1:
The illumination system changes from using fluorescent tubes to using LED sources. This parameter change in the light source type enables simultaneous achievement of high luminous flux and wide inspection width. The LED row can be configured with appropriate spacing and intensity to provide sufficient illuminance across the entire inspection width without the luminous flux deficiencies of fluorescent tubes.
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 enables quick and accurate defect analysis of wide products with a homogenous light distribution, reducing errors and scan time, and allowing for high-quality inspection in a single run.
Implementation Method 1
a spectrometer member (17) configured to split white light into its spectral components and project a multichromatic light beam thus formed from monochromatic light beams
Implementation Method 2
the illuminating unit having at least two light-emitting diodes disposed in a row
Implementation Method 3
at least two light-emitting diodes disposed in a row and an exit aperture extending along the row
Implementation Method 4
the optical detection device having a detection unit comprising a camera and an objective
Implementation Method 5
the camera being configured to detect the multichromatic light beam reflected on the product in a detection plane
Data Source
AI summary
An inspection system and a method for analyzing defects in a product, in particular a printed circuit board product, a semiconductor wafer or the like, the inspection system includes a projection device , an optical detection device , and a processing device, the projection device having an illuminating unit and a spectrometer member configured to split white light into its spectral components and project a multichromatic light beam thus formed from monochromatic light beams onto a product at an angle of incidence β, the optical detection device having a detection unit comprising a camera and an objective , the camera being configured to detect the multichromatic light beam reflected on the product in a detection plane of the detection unit, the detection plane being perpendicular, preferably orthogonal, to a product surface of the product, the illuminating unit having at least two light-emitting diodes disposed in a row and an exit aperture extending along the row.