The Xiris Blog

Using Area of Interest (AOI) to Achieve High Frame Rates with a Weld Camera

Posted by Cameron Serles on Tuesday, March 01, 2016 @ 06:00 AM

 

  All digital cameras, including the Xiris XVC-1000 Weld Camera, have a digital output signal that is limited by the speed at which data can stream out of the camera.  This limits the frame rate of the camera and is a function of the frame size of the camera.  For the XVC-1000, the camera can output 55 frames per second at full resolution of 1280 x 1024 pixels.  However, it is possible to create a faster frame rate by reducing the size of the image, or Area of Interest (AOI).  For example, if the height of the AOI is cut to half the full frame image size, then the frame rate can run twice as fast, e.g. approximately 110 frames per second, or if cut to a quarter its height, the frame rate will be over 200 frames per second.  If a very small window is made that could see a small weld process such as a laser spot and a thin weld, the frame rate could run up to 1000 frames per second.  This can be very useful in certain situations where features of very short duration need to be monitored.

   As an example, many industrial laser welding processes have their laser powered ON for very short durations, usually far less than 2 seconds.  This would require a higher speed imaging capability to see exactly what was happening on the weld.  As the Area of Interest in a laser process is a long thin rectangular area – typically the weld spot, the seam and a narrow weld pool, reducing the AOI can sometimes be done on a laser process to good effect.  The result is a high speed image capture that captures the detail of the laser spot and immediate area around it.

 Mar_2_-_Using_AOA_image.png

Using the AOI to create a Faster Image

 Summary

   A digital Weld Camera with Area of Interest capability can be used to image very small, narrow regions of interest at high speeds by reducing the Area of Interest of the camera.  As such, Weld Cameras can be used as a valuable tool for set up and alignment of high speed laser processes. 

For more information on how Xiris Weld Cameras can help monitor your weld processes, visit Xiris.com 

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Topics: quality control, weld camera, Laser welding, High Dynamic Range, productivity, Laser cutting, AOI

Imaging the Changing Intensity of the Laser Spot

Posted by Cameron Serles on Tuesday, February 16, 2016 @ 06:00 AM

 

  A major challenge that manufacturers face when integrating a weld camera to a laser weld process is the changing amount of reflected light that comes back to the camera.  Huge swings in brightness of reflected light can cause challenges when trying to produce a good image, requiring a high dynamic range camera with the ability to change quickly to rapid brightness variations. 

  To explain this phenomenon, it is useful to look at how the incident laser light hits the substrate during a welding or cutting process and how the reflected light bounces back to the camera.

Stage #1: Once the Laser is Powered ON

  When the laser is first powered on, the substrate is typically flat and perpendicular to the rays of incident light of the laser as the surface has not been melted by the laser radiation at this point.  As a result, a high amount of light from the laser gets reflected right back to the laser beam delivery optics and eventually to the camera, creating a momentary flash of intense brightness.  This bright reflection could saturate and even damage some cameras.

Feb_16_image_1.pngStage #1: Initial Incident Light Reflected

 

Stage #2: The Molten Layer Develops

  After a brief period, the laser starts to melt the surface of the substrate, creating a small concave molten layer.  The reflected light going back into the laser beam delivery system reduces as there is a bit of focusing of the reflected light rays.

 Feb_16_image_2.pngStage #2: Development of Molten Layer

 Stage #3: Vaporization and Cavity Formation

After a little more time, a deeper cavity is formed as the laser vaporizes some of the substrate material.  At this point, the laser light is bouncing around the cavity and even less light makes its way back to the camera.

 Feb_16_image_3.png

Stage #3: Vaporization and Formation of Cavity

 

Stage #4: Keyhole Formation in Substrate

The final stage is once a Keyhole is formed.  This is a deep, narrow cavity in which the metal is melted, some of it vaporized and then it flows around the cavity and solidifies.  At this point, the laser light hits the keyhole, bouncing all around the keyhole and most of it gets absorbed into the substrate, with only a little of the light making its way back to the laser beam optics and camera.

 Feb_16_image_4.png

Stage #4: Keyhole Formation

   The process of moving through the above four stages could take a few hundred milliseconds.  During this process, there is a huge variation of light that bounces back to the camera.  For example, the light bouncing back during the Keyhole Formation stage could be 10-15% of the light received during the initial irradiation of light right after the laser is powered on.  As a result, a weld camera that has been specifically designed for the huge range of light variation such as the Xiris XVC-1000 is necessary to properly image the laser welds through the start up of the laser beam.

Summary

  Cameras have been integrated into laser welding and cutting machines for some time as a valuable tool for set up and alignment of the laser head to the workpiece.  However, traditionally, once the laser power was turned on, the cameras were not able to see the laser light.  To do this, a high dynamic range weld camera such as the Xiris XVC-1000 is required to see the enormous range of light reflected back from the substrate and deal with the huge range of brightness of laser light reflected back to the camera.

For more information on how Xiris Weld Cameras can help monitor your weld processes, visit Xiris.com 

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Topics: quality control, weld camera, Laser welding, High Dynamic Range, productivity, Laser cutting

Off Axis Mounting of a Weld Camera onto Laser Processes

Posted by Cameron Serles on Tuesday, January 19, 2016 @ 02:04 PM

Off Axis Mounting of a Weld Camera onto Laser Processes

A High Dynamic Range Weld Camera can provide great benefit to a laser welding or cutting process by being able to see the melt pool and seam while the laser is on.  In this blog we explore an additional method of mounting cameras to the laser welding or cutting process – Off Axis mounting of the camera.

 Off Axis mounting of Weld Camera

Off Axis mounting of a weld camera is when the camera is mounted separately from the laser beam delivery head in such a way that it is aimed at the work surface where the laser makes contact.  It contains completely separate optics and lighting components with its own mounting mechanism.  Because of the flexibility of location, a camera that is mounted off-axis can be placed at any position around the laser head to get the best image.  These locations can be categorized as:

  1. Forward looking: to see the seam and work environment prior to the weld;
  2. Backward looking: to see the weld pool and weld bead after welding; or
  3. Sideways looking: to gain an overall perspective of the weld environment.

Co-axial_image_1.png

Off Axis Camera Mounting Relative to Laser Beam Delivery System

 In the above image, a simple laser beam delivery system is shown with a camera mounted obliquely to the laser beam optics.  This provides the ultimate in mounting flexibility to get the best possible image desired.  There are a number of advantages and disadvantages of this type of set up:

 Advantages:

  • More mounting options as to where and how to place the camera relative to the laser head, with various optical configurations and fields of view possible;
  • Extra lighting can be added to see additional background detail that is farther away from laser source and not illuminated by the laser itself.

 Disadvantages:

  • A separate, sometimes complex mounting system is required that needs to be mechanically coupled to the laser head so that both units travel in tandem without relative movement.
  • As most laser beam delivery systems are much larger than the beam spot, the camera has restricted access to be able to view the immediate area around laser spot, making obtaining a good image challenging in some situations.

  Summary

Weld Cameras can be integrated into laser welding and cutting machines using an Off Axis mounting technique.  Such a technique provides the ultimate in flexibility to acquire different types of images as required by the machine designer, yet not be constrained by the optics in the laser beam delivery system.

For more information on how Xiris Weld Cameras can help monitor your weld processes, visit Xiris.com 

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Topics: quality control, weld camera, Laser welding, High Dynamic Range, productivity, Laser cutting

Coaxial Mounting of a Weld Camera onto Laser Processes

Posted by Cameron Serles on Tuesday, January 05, 2016 @ 02:30 PM

Coaxial Mounting of a Weld Camera onto Laser Processes

A High Dynamic Range Weld Camera can provide great benefit to a laser welding or cutting process by allowing examination of the melt pool and seam while the laser is on.  In this blog we explore one method of mounting cameras to the laser welding or cutting process:  Coaxial or On-axis mounting of the camera.

In coaxial mounting, the camera is mounted parallel to, and pointing in the same direction, as the laser source.  The image delivery optics for the camera are combined with the laser beam delivery optics via a beam splitter so that the camera shares part of the final optical path through which the laser beam travels.

 A depiction of an On-axis camera mount configuration is presented below.  In this configuration, the camera has the straight through optics while the laser beam is coming in from the side via a beam splitter.

Camera_picture.png

On-axis camera mounted to laser beam delivery system

 There are both advantages and disadvantages to this type of camera set up on the laser process.

 Advantages:

  • Results in a small form factor package that can be tightly integrated into the laser optics head.
  • Operator is able to see the weld in real time because the actual laser optics are used.
  • Camera lighting can be tightly controlled inside the laser optics, minimizing external influences.
  • Operator is able to monitor the work environment pre-weld for alignment; in real time during welding for laser beam monitoring; and post weld to ensure the quality of the weld.

 Disadvantages:

  • Resulting image quality is dependent on the design of the optics contained in the image delivery system. In certain situations, an additional light may be required to illuminate the work piece in such a way as to make it visible through the image delivery optics (see drawing above).
  • There may be coatings or filters on some of the optical components in the laser beam delivery system that inhibit specific wavelengths of light from travelling up the image delivery optics. This may reduce the visibility of some of the darker background areas around the laser.
  • Reflections may appear in the image due to any misalignment in the image delivery system.
  • Because the camera’s optical path is the same as that followed by the laser beam delivery, there is a limited field of view which may not allow the camera to see all of the features of interest.

 Summary

Weld Cameras can be integrated into laser welding and cutting machines using a coaxial or on-axis approach where the camera uses the same optics as used by the laser.  Such an approach provides a physically compact solution but the visible field may be limited by the optics in the beam delivery system.

For more information on how Xiris Weld Cameras can help monitor your weld processes, visit Xiris.com 

Sign up to receive our Weld Video of the Month

Topics: weld camera, Laser welding, High Dynamic Range, productivity, Laser cutting

Integrating a Weld Camera into Laser Welding Processes

Posted by Cameron Serles on Friday, December 04, 2015 @ 01:20 PM

 Integrating a Weld Camera to Laser Welding Processes

 High powered industrial lasers have been incorporated in a variety of metal fabrication processes, most commonly for welding and cutting applications, where the high power of the laser allows for rapid processing speeds.  As fabricators have adopted industrial lasers throughout their shop floor, it has become painfully obvious to the fabricators that the material being processed by lasers had to be prepared and aligned differently than traditional processes.  Because a laser beam is so small, precise fit up and alignment of the material being processed is needed to ensure the laser process is viable.  Careful monitoring of the fit up and alignment is required to ensure a good welding process.  Because of the safety issues of being around a laser light, the only practical way to monitor how the material has been prepared and aligned to the laser head was to use a camera that was integrated to the laser beam delivery system. 

 The laser beam delivery system

The laser beam on most cutting and welding systems is delivered to the work piece using a series of optical components such as lenses, filters and mirrors.  Together the assembly is known as the “laser beam delivery system” and can be complex in shape and size to suit the application, as the laser may have to be bent to be as compact and functional as possible.  Most laser beam delivery systems have a camera port integrated into the assembly to allow a camera to view down the same optical path as that travelled by the laser beam.  By adding a camera to the beam delivery system, the operator can monitor the workpiece material to ensure it was properly prepared and aligned prior to powering up the laser.picture_3.png 

A Simplified Laser Bead Delivery System

 

The Problem

Once the idea of putting a camera on the laser system has been accepted, there is often frustration with the fact that the cameras most commonly used become useless once the laser is turned on.  Because the laser generates enormous amounts of focused light that partially bounces up to the camera or creates very bright keyholes and weld puddles once it hits the work piece, the resulting image is just too bright for standard cameras to see any detail in the brightest sections of the image.  As a standard camera can see about 48-60 dB of range of brightness, it will simply saturate where the image gets too bright, resulting in a white blob on the screen.  The solution implemented by many fabricators and equipment builders?  Turn off the camera when the laser is powered.

 A Better Solution

However, a better solution does exist.  A high dynamic range weld camera can be used in place of a standard camera to adapt to the laser process.  A good weld camera can see more than 140 dB of range of brightness, or a ratio in excess of 10,000,000:1 of the brightest to darkest pixels in an image.  This allows for detail in the brightest area of the image of a laser weld or cut to be seen without saturation while still seeing detail of the background around the weld, including the weld pool or seam.

 By implementing a weld camera to see the laser process, an operator can see what is going on with their laser welding process once the laser power is on, ensuring that the laser beam is functioning correctly: that the beam is focused properly, that the keyhole is of the correct shape (round vs. oval), size and location (relative to the weld seam), and that the weld pool is symmetric on either side of the weld seam and sized correctly.

 Picture_1.png

Image from a High Dynamic Range Camera of a 3000 W Laser

 

For more information on how Xiris Weld Cameras can help monitor your weld processes, visit Xiris.com 

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Topics: remote monitoring, weld camera, Laser welding, High Dynamic Range, productivity

Improved Productivity in Submerged Arc Welding using a XIRIS Weld Camera

Posted by Cameron Serles on Tuesday, October 27, 2015 @ 02:21 PM

The problem

A large fabricator in Mexico employed welding operators high atop their welding manipulators to monitor the process of Submerged Arc Welding (SAW) of large steel pressure vessels.

Each time an operator needed to come down from their monitoring perch (eg: break time, equipment malfunction, end of shift, etc.), approximately 15 minutes of production time was lost.  Not only did the  equipment need to be stopped and the path down secured, auxiliary personnel at the base station were needed to provide safety backup to move the manipulator out of the way and lower the boom for the welding operator to climb off the machine at ground level.  Another 15 minutes were lost while the path was re-secured, the operator returned to the monitoring perch and the manipulator was realigned in order to resume production. Each of these 30 minute cycles represented a significant loss of productivity for the company.

The Solution

The fabricator needed a solution to improve their productivity.  Recognizing that a 30 minute delay, 2-3 times per shift was uneconomical and, in the long run, unsustainable, the fabricator was able to rationalize the purchase of a Xiris XVC-S Sub Arc Camera.  The improvement in productivity alone was sufficient to justify the acquisition.  Once a sub arc weld camera was installed at the weld head and the machine controls, along with a new monitoring screen, were moved to the machine's base platform at ground level, operators were no longer required to be stationed high above the shop floor.

The Result

Now, when an operator needs to leave the machine, it is a simple matter of putting the machine on pause and walking away.  Since the manipulator remains in place and safety backup is no longer required, the time and productivity lost to a production interruption has been dramatically reduced to just a few minutes.

 An additional benefit of this set-up is that operators, monitoring the weld process remotely, at the ground level control station, are far less fatigued during their shift.  They no longer have to climb up and down from their workstations nor must they lean out over the weld head to monitor the proceedings.

For more information on how Xiris Weld Cameras can help monitor your weld processes, visit Xiris.com 

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Topics: remote monitoring, weld camera, productivity, submerged arc welding

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