- Resonator problems
- Beam misalignments
- Aged optics
- Damaged optics
- Gas impurities
- Dross on laser cut
- Decreased cut speeds
- Low or unstable laser power
- Off-balance or unstable beam profile
Many customers involved with laser welding measure the pulse energy output of their lasers, but is this all the data required needed to ensure quality welds? Steve Schellenberg at Spinal Modulation had his doubts. While he found pulse energy measurement using his Ophir equipment useful in qualifying his laser welding process, two of his laser welding stations were producing different quality welds despite producing identical laser pulse energies. One laser welder seemed to be doing an OK job, while the other welder produced significantly lower quality welds. Steve suspected differing laser profiles might be the culprit and invited an Ophir representative in to characterize the profiles of each welding laser.
Anyone who has driven a vehicle has encountered a Light Detection and Ranging (LIDAR) system in action. Some of you have even found out how much it can cost in terms of speeding fines! Let’s take a closer look behind the scenes. How do we know the detector is working?
In this application, the LIDAR device sends out a 130 μW 904 nm beam, the beam is produced by three light emitting diodes (LEDs). Once the light leaves the device and travels down range towards the target the light is scattered.
A manufacturer needed to profile and measure diodes that produce a 1300nm CW source in the 10's of mW's. The inspection needed to be conducted in seconds with full accuracy and repeatability because100% inspection was specified to insure the quality level needed by the customer. As this component was a basic element to the finished product, if any defects could be identified at this stage, a significant savings in scrap product would be realized vs attempting to rework finished product.
People working with lasers are trying to do something with the light beam, either as the raw beam or, more commonly, modified with optics. Whether it is printing a label on a part, welding a precision joint, or repairing a retina, it is important to understand the nature of the laser beam and its performance. Laser beam characterization instruments provide the tools to know precisely what the laser beam is doing at the point of the work and if the optics are having the desired effect.
We started by taking a power reading with the 10kW sensor and a Juno USB Interface to a local PC. This particular sensor had a damaged spot on the thermopile element, so I’m not sure it was giving us an accurate reading. However, here were the recorded power readings:
A manufacturer was asked to produce a high volume of molded devices that have an <100um hole in the center through which in the final assembly a specific amount of material will pass. Since the product cannot be tested until fully assembled, any device found to have the incorrect hole size, must be rejected and reworked, thereby reducing productivity. Being able to inspect and sort out acceptable from unacceptable devices prior to final assembly can represent a significant cost savings.
The 1780 ModeScan determines M2 and other beam propagation parameters of a laser in real time. Traditionally, these laser measurements were performed by directing the laser beam through a lens and measuring the resulting beam waist caustic by moving a beam profiler system or internal mirrors along the beam path. A beam size measurement is acquired at each profiler or mirror location. It normally takes 30 seconds to a few minutes to generate results in this manner. This also requires moving parts within the M2 laser measurement system that will wear down over time.
Upon the installation of new laser processing equipment, it is necessary to test and verify the performance of the laser system to insure it meets specification. Just relying upon the test results of the laser prior to shipment is not sufficient – shipping issues, handling problems, and reinstallation activities can all affect the final performance of the equipment. For these reasons, testing the equipment once set up for manufacturing is essential and critical to have the confidence the intended application will achieve or exceed the specification.
When installing a fiber delivered laser system, checking the quality of the delivered beam is important. The beam quality can be checked at the couplers and verified through the optics. But only when the final beam is delivered to the work surface can the combined effect of these variables be detected and validated.
In this application, our customer manufactures encoders that incorporate LED’s (light emitting diodes) that have a collimating lens attached. The LED’s produce between 850nm and 880nm at 2mW to 15mW, the beam sizes range from ¼” to ½”. Until now, a laser power meter has been used to verify the output wattage. Shining the beam on graph paper has been used to verify the beam size visually.
The application is to design a low cost inspection process that will detail and record data on batches of incoming LED’s for beam quality.
Today’s aircraft are made of materials unknown to early aviation pioneers. These new materials require sophisticated inspection and repair procedures. Older inspection technologies are often incapable of testing and verifying the integrity of some composite structures. So aircraft operators, manufacturers, and government agencies have worked hard to find acceptable technologies to inspect the newer generation aircraft and ensure a level of safely for passengers and cargo flying in countries around the world.
This application note is intended to provide guidance for the measurement of the divergence angles of custom optical fibers. This also applies to other divergent sources such as laser diodes or LEDs. Measurement of the divergence of such sources can be made using either the Goniometric Radiometer or NanoScan family of products. The accuracy and detail of the measurement depends on the divergence and on the instrument used.
In general, Goniometric Radiometers yield the most accurate measures, providing direct angular profiles with effective angular scan at constant radius with range up to ±72° for the LD 8900 and LD 8900R, and up to ±90° for the LD 8900HDR. They also provide a 3D spherical pinhole scan of the irradiance pattern.
The competitive nature of the manufacturing of solar cells is largely influenced by the zero defect approach of high speed automation. To this end, YAG lasers have been called upon to provide the precise laser scribing of the panels. Once the various layers of photovoltaic materials have been laminated to the glass, the laser is needed to scribe a series of channels that eventually become each of the individual voltage producing cells.
The quality, shape, size and intensity of the laser must be closely monitored and controlled for this process to produce a solar cell that meets specification and cost requirements. There are two variables when using a laser for scribing that must be monitored and controlled; the intensity or energy of the beam and the size and shape of the laser beam.
American author, engineer, entrepreneur, and consultant in performance improvement H. James Harrington has been credited as saying, “Measurement is the first step that leads to control and eventually to improvement. If you can't measure something, you can't understand it. If you can't understand it, you can't control it. If you can't control it, you can't improve it.”
Even though Harrington was speaking specifically of improving of the quality in a person’s work performance, the same is true for maintaining a quality laser process.
Measurement of a laser usually consists of quantitative measurement by use of a power or energy measurement system, or qualitative measurement by the use of a beam profiling system. Beam profiling can be described as using a device, such as a camera, scanning slit, or other device to image a laser beam or a sample of the beam, interfacing that imaging device with a PC, and analyzing that image using beam analysis software. The data obtained from a beam profile can be used in several different ways.
High power is a fairly indistinct term that means different things in different contexts. High power laser beams are handled by using reflective materials, and the level of reflectivity is dependent on the wavelength of the laser light.
“High Power” Defined
In general, the long infrared wavelengths, such as that of the carbon dioxide laser at 10.6microns, are highly reflective. These allow for the highest power measurements up to the maximum levels of several kilowatts. When measuring these lasers and power levels, the principle concern is the heat buildup in the scan head. The surfaces of the measurement drum and slits are better than 98% reflective to this wavelength, and thus only 2% of the incident power will be absorbed by the scan head and heat it up. Nonetheless, at 5000W this represents a heat load of 100W that will raise the temperature of the internal components and may cause damage to the detector and encoder electronics.
One of the facilities of a solar panel manufacturer processes approximately 1,000 panels per shift. Each panel is about 1.5ft x 4ft in size and generates 60W. Their production cost of $2.00 per panel is one of the lowest in the industry.
The production process employs both 532nm and 1064nm scribing lasers, mostly 30W systems. Each panel is scribed by both wavelengths through the process. Their design has each panel placed on a horizontal X-Y table, and run back and forth under a fixed steel yoke where there are a minimum of four beams, scribing four lines simultaneously. The panel ends up with a series of voltage stripes, each about 1” wide and the length of the panel.
Laser Welding System
- Nd:YAG Laser
- 1064 nm
- 300 mJ per pulse
- 1.5 ms pulse duration
- Dual pulse laser weld process, 0.2 secs separating each pulse
- Beam size nominally 150-200 microns (2nd moment) at Focus
- Beam focus approximately 45 mm from laser focusing lens
Spiricon Beam Profiler
- BeamGage Professional
- SP620U Camera
- LBS-300-NIR with -50 mm focal length lens on the input
Results The profiling assembly was positioned at the approximate location of the vertical beam with the LBS-300 sliders set to maximum attenuation. Once faint ghost images of the profile were found, the beam attenuation was reduced to use the dynamic range of the SP620 camera.
Included are two screenshots from a recent test using the ModeCheck device from Ophir-Spiricon.
The screens below show a comparison of a II-VI MP5 lens and Ophir Optics Black Magic lens.
Fiber laser source
- 600μm fiber
- 1 KW max average power
Class 1 workstation
125mm focusing lens
Profiling lasers with powers in the 10mW to 1W range is becoming more common. Many of these lasers are in the visible spectrum, allowing them to be measured with CCD and CMOS camera systems. As with any laser that is being measured with a camera array, the beam needs to be attenuated, but there are some cautions to be observed. These beams are not so powerful that they will damage or destroy typical absorptive filters. In fact, it is possible to stack up a sufficient optical density to reduce the power of a 1W laser to the pW levels that will not saturate the detector. Unfortunately doing this will more than likely result in erroneous measurements. This is due to a phenomenon called thermal lensing, or thermal blooming. The laser’s energy heats the local area of the absorptive filter, changing its optical properties. These changes often result in changes to the refractive index of the substrate, forming a lens that may either focus or expand the beam. At lower powers, this phenomenon can be observed over discernable timeframe, hence the term “blooming.” However, it may also occur almost instantly, giving the illusion of stability and accurate measurements.
Aligning the output of laser diode or fiber optic arrays can be quite challenging. One of the lesser known features of the Photon NanoScan slit profilers is the multibeam analysis capability. The NanoScan software allows the characterization of up to 16 simultaneous beams entering the aperture, allowing the user to examine and evaluate various standard beam parameters displayed within the automatically-determined or user-defined regions-of-interest (ROI) on any or all beams captured by NanoScan. This unique control and selection feature gives the user flexibility to single out one beam or to view the entire beam set. Multiple beam data is displayed on the screen and can be isolated in contiguous beam sections as they are collected.
- Fiber Source:
- 400 µm Spot / Fiber
- 4 kW Max Average Power
- Precitech Welding Head
- 5 Degree Angle
- 300mm fl Lens
- X,Y and Z Motion Control
- Open Class 1 Workstation
One of the recent developments in the photonics industry has been the rapid increase in automated solar panel production facilities.1 Many of these end-to-end production lines use laser-based methods to manufacture the thin film silicon photovoltaic modules. The lasers used for this activity are generally diode-pumped solid-state lasers at 1064nm, 532nm and 355nm with beams focused to around 30μm.2 They are run at powers or energies3 that, although not extremely high, have high power or energy densities at these small beam diameters. The techniques used often call for multiple beams, running in parallel, to make precise cuts to electrically isolate the sections of the photovoltaic sheets. To ensure that these cuts are uniform, it is important to measure the beam profiles.
Many forces drive the miniaturization of optical component technology. Integration of optical components into smaller packages is expected to reduce size constraints, insertion loss, and manufacturing costs. Many ambitious business plans are based on this integrated technology, as it seems amiable to high volume manufacturing methods similar to those found in the semiconductor industry. However, there are numerous technical hurdles to overcome before this Holy Grail is attained.
This year we are celebrating the 50-year anniversary of the laser. Lasers have proven one of the most promising technologies, yet there is still farther to go. With the advancements come more complex and “focused” (no pun intended) laser applications. In some cases, especially with industrial laser processes, it’s getting to the point where the end user -- whether it be the process engineer, quality personnel, or maintenance technician -- must dedicate more and more time to studying laser technologies in order to truly understand the way lasers are being applied. Companies who supply laser beam characterization products have also been diligently developing these technologies in order to continue to provide the best real-world solutions possible.
If you have been in the laser cutting business long enough you eventually will have one of those days when, no matter what you do, the laser will not cut your parts cleanly…if at all. The operators and maintenance personnel check and verify all the usual problem areas and finally conclude that everything looks, measures, and appears correct.
What happens when your company's new laser fails to perform according to specifications and your best customers are waiting weeks for delivery? Does the manufacturer send a field service engineer repeatedly to check for problems? What happens when the manufacturer cannot tell you what is wrong after they finally send their corporate, factory-level engineers to investigate? Do you demand a full refund if the laser still won't work properly and weeks are passing by? What if you spent a fortune in acquisition, setup, training and labor costs and you thought that you bought the best product available on the market?
Problem: What happens when your company's new laser fails to perform
according to specifications and your best customers are waiting weeks for
delivery? Does the manufacturer send a field service engineer repeatedly to
check for problems? What happens when the manufacturer cannot tell you what
is wrong after they finally sent their corporate, factory-level engineers to
investigate? Do you demand a full refund if the laser still won't work properly and
weeks are passing by? What if you spent a fortune in acquisition, setup, training
and labor costs and you thought that you bought the best product available on the
The business objectives in the title of this article are standard in all types of manufacturing, and laser-assisted fabrication is no exception. A set of tools has become available in the past few years that allows end users of industrial lasers to optimize the laser process while complying with current ISO and AWS technical standards. This helps manufacturers remain competitive in the US and in the global markets.
The EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) mission is a joint European-Japanese mission addressing the need for a better understanding of the interactions between cloud, radiative and aerosol processes that play a role in climate regulation. Enzo Nava, Head of the Electro-optics Section at CESI, reports. “We had to produce a pre-development model for the Atmospheric LIDAR (ATLID) laser transmitter to operate. In this case, we were developing an end-pumped Nd:YAG MOPA laser system with frequency tripling to operate at 355 nm.