Machine Vision Explained

Machine Vision Explained

Vision systems are used for manufacturing line inspection and non-inspection tasks, so here’s what you need to know about what’s right for your operation.

By Dave Richardson, Vision Solutions Provider, Teledyne DALSA

Editor’s Note: This article is adapted from a comprehensive white paper, “What You Need to Know Before Implementing a Machine Vision System.” Download the free, full white paper that provides additional information about how to determine which systems align with your application and how to integrate vision inspection into your production line.

Vision systems are a primary consideration for any manufacturer that wants to improve quality or automate production. Think of vision systems as computers with eyes that can identify, inspect and communicate critical information to eliminate costly errors, improve productivity and enhance customer satisfaction through the consistent delivery of quality products.

Primarily used for online inspection, vision systems can perform complex or mundane repetitive tasks at high speed with high accuracy and consistency. Errors or deviations in the manufacturing process are immediately detected and relayed, allowing control modifications to be made on the fly to reduce scrap and minimize downtime.

Vision systems also are used for non-inspection tasks, such as guiding robots to pick parts, place components, dispense liquids or weld seams.

Machine vision systems come in all shapes and sizes, but they all have the same core elements:

  • One or more image sensor that captures pictures for analysis.
  • Application software and processors that execute user-defined inspection programs or recipes.
  • A way of communicating results to complementary equipment for control or operator monitoring.

Significant and important differences exist between vision systems that typically make one more suitable than another for any given application.

It’s equally important to know the importance of choosing the optimal sensor, lighting and optics for the job. Failure to do so might result in unexpected false rejects, or even worse, false positives.

Two Categories of Vision Systems

Many variations of machine vision systems are on the market, but for our purposes here, we’ll classify them all into two categories:

  1. Those with a single embedded sensor (also known as smart cameras), and
  2. Those with one or more sensors attached (multi-camera vision systems).

The decision to use one or the other depends not only on the number of sensors needed, but also on a number of other factors, including performance, ownership cost and the environment where the system needs to operate.

Smart cameras, for example, generally are designed to tolerate harsh operating environments better than multi-camera systems. Similarly, multi-camera systems tend to cost less and deliver higher performance for more complex applications.

The Role of Processing Needs

Another way to differentiate the two classes of systems are processing requirements. For many applications, such as in car manufacturing, it’s desirable to have multiple independent points of inspection along the assembly line. Smart cameras are a good choice, because they’re self-contained and can be easily programmed to perform a specific task and modified if needed without affecting other inspections on the line. In this way processing is “distributed” across a number of cameras.

Similarly, other parts of the production line might be better suited to a centralized processing approach. For example, final inspection of some assemblies commonly requires 16 or 32 sensors. In that case, a multi-camera system may be better suited, because it’s less costly and easier with which the operator to interact.

Software is Key

Perhaps the most important consideration when selecting any vision system is software. Software capabilities must match application, programming and runtime needs. If they don’t, you’ll find yourself investing more time and expense than anticipated in trying to conform the system to your expectation.

If you’re new to machine vision or if your application requirements are straightforward, you should select software that is easy-to-use (i.e., doesn’t require programming), includes core capabilities (i.e., pattern matching, feature finding, barcode/2D, OCR) and can interface with complementary devices using standard factory protocols.

If your needs are more complex and you’re comfortable with programming, you might look for a more advanced software package that offers additional flexibility and control.

In either case, make sure the software you choose is available across vision system platforms in case you need to migrate in the future because of changing inspection requirements.  

Teledyne DALSA, based in Billerica, Massachusetts, is a participating EncompassProduct Partner in the Rockwell Automation PartnerNetwork™ program. The company provides machine vision components and solutions including image sensors, cameras, acquisition boards, sophisticated vision software and intelligent vision systems.

 

The Journal From Rockwell Automation and Our PartnerNetwork™ is published by Putman Media, Inc.

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The JOURNAL from Rockwell Automation and Our PartnerNetwork™ is a bimonthly magazine, published by Putman Media, Inc., designed to educate engineers about leading-edge industrial automation methods, trends and technologies.