Lasers and Machine Vision

Machine Vision for Inspection

When compared to traditional light sources, lasers provide a much higher contrast with the background image providing the computer algorithm with a more precise reference source.   As a result, lasers have been widely deployed as structured lighting in many image processing systems.  Machine vision lasers are typically beam shaped into lines, dots, and other geometric patterns (such as crosses, circles, and grids) and they can come in a wide variety of wavelengths and powers depending on the systems requirements.   Each of these geometries has its own unique advantages, but lines tend to be the most commonly used laser shape in modern machine vision technology.  Lines are the most popular because if the laser is offset at an angle from the camera, a 3-dimensional image of the object can be reconstructed through a process known as triangulation.  As demonstrated in the figure below, when an object passes under the laser line, there is a resultant spatial offset between the laser light on the top of the object and the light on the sides.  By measuring this offset in the image, also shown in the figure below, an algorithm can then calculate the height of the object based on the known angular offset.    While the example below shows a rather simple example, this same process can be applied to highly complex objects as we will discuss below.

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Lasers for Machine Vision: Selection Criteria

Both 2D and 3D imaging have a strong presence in industrial processing applications and have become cost-effective for consumer applications such as gaming or autonomous vehicle guidance. Using multiple lasers with different wavelengths helps to provide enhanced contrast or color data along with the image. Selecting the appropriate laser for your machine vision system depends on what you are trying to accomplish and the overall system architecture. While your system specifications are a good starting point, the system designer must know a little about lasers and how they are specified by their manufacturers in order to ensure they are making the correct purchase. Some specs will be obviously important to you, but others may not be so obvious until you get the laser in your system and wonder why it doesn’t work as intended…

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High Power Laser Line Generators for Rail Inspection

Laser line generators are widely used in machine vision for a broad variety of inspection applications.   When used for the inspection of small parts laser lines and other shapes are typically achieved through the use of diffractive optical elements to create a wide variety of geometric shapes and patterns, but diffractive beam shaping requires the use of single-mode diode lasers.    As the objects under inspection grow in size so do the demands on the size of the laser lines, and there quickly comes a point at which the laser power outpaces what is available from commercial single-mode laser diodes.     As a result, in order to generate large lines from higher powered multi-mode lasers diodes either galvanometric scanning mirrors or micro-optic arrays are required.  While scanning mirrors can be rather effective at producing uniform laser lines, they suffer from reliability issues especially in rugged environments making them a less than ideal solution for field deployable systems.  Micro-lens arrays, on the contrary, are a monolithic solution with can either be placed at the output of a bundle of fiber-optic cables or directly in front of the diode bar exploit inherent astigmatism, to produce flat top laser lines.

These high-power laser lines, produced using micro-optic arrays, can be used at distances up to 3 meters from the source with fan angles as large as 110-degrees, making them ideal for inspecting larger objects and surfaces.  In the figures below, you can see an example of the laser line cross-sections for a FocusFlux EL series line laser system, measured at a distance of 2 meters from the source.

To demonstrate the usefulness of such a laser system, we can take a look at the application of machine vision in the transportation industry for laser rail inspection where high-power laser diodes are widely deployed.  These laser rail inspection systems use high-speed cameras in conjunction with high power laser line projectors mounted on rail vehicles to acquire high-resolution digital images and 3D profiles of the rails and beds.  This data can then be feed into specialized image processing software to automatically detects railway features such as rails, ties, and fasteners as well as defects such as cracking of concrete ties.  Additionally, track geometry, gauge width, alignment, wear and a wide variety of other mechanical parameters can also be measured.  These same principles can also be applied to roads, bridges and other forms of infrastructure to survey cracks and other structural defects.  In the images below (courtesy of Pavemetrics) you can see an example of how such a system could be deployed for both rail (left) and road (right) applications.

How Can We Help?

With many years experience providing machine vision laser sources, and 1000s of units fielded, we have the experience to ensure you get the right product for the application. Working with RPMC ensures you are getting trusted advice from our knowledgeable and technical staff on a wide range of laser products.  RPMC and our manufacturers are willing and able to provide custom solutions for your unique application.

If you have any questions, or if you would like some assistance please Contact Us here. Furthermore, you can email us at info@rpmclasers.com to talk to a knowledgeable Product Manager.

Alternatively, use the filters on this page to assist in narrowing down the selection of machine vision lasers for sale. Finally, head to our Knowledge Center with our Lasers 101 page and Blogs, Whitepapers, and FAQ pages for further, in-depth reading.

Finally, check out our Limited Supply – In Stock – Buy Now page: This page contains an ever-changing assortment of various types of new lasers at marked-down/discount prices.