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Tech Papers

When Machine Vision Inspection Comes Up Short: Is “Almost” Defect- Free Enough for Your Customers?

by Radiant Vision Systems, LLC - Radiant Vision Systems

Traditional machine vision systems are sufficient for many types of inspection tasks, but they aren’t effective for high-precision, low-contrast, and challenging assembly verification tasks. When absolute quality is critical, Radiant’s photometry-based INSPECT.assembly closes the gap.

Machine vision systems are common in many assembly line inspection applications. These systems provide the quantifiable data necessary to automate processes, and offer speed to meet production demands. However, many vision systems today are limited in their ability to detect defects in complex assemblies—especially low-contrast components or those limited to very fine spatial tolerances. While human inspectors excel at identifying anomalies and subtle details, their inspection performance is slower and less consistent, limiting production efficiency and permitting costly escapes.

Advanced Vision. INSPECT.assembly from Radiant overcomes the challenges of both human and traditional machine vision inspection methods. The system is a fully integrated, turnkey inspection station that detects subtle defects in real time on the production line with more accuracy than machine vision and greater repeatability and consistency than human inspectors. Combining a photometry-based, scientific-grade CCD imaging system with bright field lighting, specially configured software, a touchscreen HMI (GUI), and complete fixturing, the station rolls right up to your production line, taking up no more space than a human inspector.

More Discerning than Machine Vision

High Resolution. The performance of a machine vision system relies on high-quality images that enable the system to “see” features and apply meaningful evaluations to these details. Photometric imaging systems acquire more data from a single image than standard machine vision systems, capturing a greater number of pixels and more gray levels to evaluate regions of measurable contrast that may indicate a defect. Most machine vision camera sensors offer 1-5 megapixels (MP) resolution. INSPECT.assembly uses photometry-based Radiant ProMetric® camera systems that are typically applied in light measurement. Our systems offer superior resolution (up to 43 MP) combined with broad dynamic range to achieve unmatched image clarity for high precision inspection.

Low resolution, low dynamic range            High resolution, broad dynamic range

Low resolution, low dynamic range (left) versus high resolution, broad dynamic range (right).

Dynamic Range. Radiant’s ProMetric cameras feature CCD sensors with broad dynamic range (up to 61 dB) to capture the most contrast-level differences in images. The system can visualize the smallest variations on part surfaces caused by reflections of light (such as shadows that indicate a drill hole, or spectral reflections that indicate a metal component). INSPECT.assembly can capture and classify defects with extreme precision, outperforming traditional machine vision systems. It can detect the most subtle defects that are missed by machine vision, such as the absence of tiny black screws on a black surface.

Inspecting for black screws on a black surface

Quantifying Defect Severity. Machine vision systems have a limited ability to discriminate between different defects based on their unique features or to grade their overall impact to device quality. In applications where a defect may be acceptable below a certain tolerance, such as the proximity of components within a margin, Radiant’s advanced vision technology provides not only defect detection, but quantifies defect size, depth, or type, weighted against defined tolerances. This data can be used for production quality control, defect trending, and pareto analysis to reduce the number of rejected parts over time.

The Power of Photometry-Based Advanced Vision

Radiant’s inspection systems include advanced image analysis software based on our leading photometric tools for light measurement. Our systems are able to detect defects in intricate detail because they use techniques for evaluating properties of light, such as software tools for detecting just-noticeable differences (JND) in visible light uniformity. This capability allows INSPECT.assembly to identify unknown defects (unpredictable features) in unknown locations (undefined points of interest), just like a human inspector.

Detection of blemish in an illuminated display            Detection of a dent on a metal surface

Detection of blemish in an illuminated display (left), as compared to detection of a dent on a metal surface (right).

Automating—and Exceeding—Human Visual Acuity

INSPECT.assembly can detect defects that may go unnoticed by human inspectors, including misaligned cables and connectors, and gap variations of less than 1 mm between components. With tolerances so precise, INSPECT.assembly provides a production-level inspection solution with the objectivity, endurance, and repeatability of a machine vision system, while achieving visual inspection capability equal to and even surpassing human perception.

With advanced vision capabilities, INSPECT.assembly addresses manufacturing demands for both operational efficiency and absolute product quality in high-value and high-risk products.

Applications

INSPECT.assembly is ideal for applications requiring inspection of highly complex assemblies during sub- and final assembly. It detects subtle flaws in high-value components that may even pass human inspection and functional test, and which could result in latent failures after shipment. INSPECT.assembly detects:

  • Component presence/absence
  • Component position
  • Connectors and connector pins
  • Cable/wire routing
  • Screws
  • Fasteners
  • Internal components (e.g., batteries)
  • Labels and their location

It inspects for all of these issues simultaneously, at production line speed.

INSPECT.assembly

Recognized for Innovation
Radiant Vision Systems was honored with a Silver-level award at the Vision Systems Design 2017 Innovators Awards for our INSPECT.assembly system (formerly the VIS-I system).

 

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