Laser Beam Analyser Laser Diagnos c System If you can measure it, you can control it!
Introduc on to Laser Beam Analysis In industrial -, medical - and laboratory applications using CO 2 and YAG lasers, it is important to know the exact instantaneous distribution of the intensity across the laser beam, i.e. the laser's mode. During time and usage of the intensity. This has a big impact on the correct working of the laser beam. By analysing the laser beam, adjustments can be made to This results in: Less waste Higher production rates Faster set up time More consistency of processes
Our Laser Beam Analyser = your solu on! All beam analysing methods known to date are cumbersome and have one serious drawback: they do not allow measurement and continuous monitoring during an experiment or during material processing. Our offered Laser Beam Analyser (LBA) however, does make it possible to monitor the intensity distribution across the laser beam during an experiment or material processing, without noticeable loss of beam intensity (the intensity is reduced by mere 0.8 %). The compact system can be setup easy and quickly and is easy to operate. Connected to an oscilloscope or with our Laser Diagnostic Software on a pc, you are able to analyze the laser beam of your CO2 or YAG laser in an instant! With our LBA you can easily measure the laser during normal working
LBA Working Principle Driven by a synchronous motor, a needle with a high reflective surface rotates in a plane perpendicular to the beam. While passing across the beam it reflects a tiny fraction of the beam onto two pyroelectric detectors. The needle is moving at constant speed and the power distribution across the beam section, is represented by the amplitude of the amplified signals from the detectors. The LBA is designed for displaying simultaneous the intensity profiles in the x and y axes (see picture) on a dual trace oscilloscope. APPLICATIONS 1. Adjustment of CW-Lasers The LBA is mounted and centred on the beam in a convenient position while the oscilloscope is placed beside the mirror to be adjusted. During adjustment the variation of the intensity profile can be directly observed and the laser can easily be adjusted to get an optimum mode. 2. Intensity Profile Control in Material Processing The LBA is permanently installed in an easy accessible place in the beam path between the laser and the work station, the oscilloscope being installed at the work station. This arrangement allows control of the instantaneous mode and power during the working process. The beam intensity loss due to the LBA is only 0.8%. Permanent installation in the beam path does not impair production quality. When a laser is used in production - e.g. for steel cutting - a "good mode" is a prerequisite for a clean cut. The Laser Beam Analyser offers permanent control of the intensity profile. Further development toward fully automatic operation is feasible. The signal can be processed electronically and be used for automatic production control by comparison of actual to optimum parameters. There are some interesting aspects to lab applications. It is generally known that in metals processing a considerable portion of the radiation is reflected from the metal surface and reenters the laser via the focusing lens in the form of a parallel beam. This retro reflection increases the power density inside the laser and can lead to a substantial variation of the laser's mode. Direct observation of this phenomenon by means of the LBA allows the optimization of the process parameters.
3. Measurement of Beam Divergence As the rotating needle passes across the beam at constant speed there is a fixed relationship between passage time and beam width. Taking model LBA1 for an example, 400µs shown on the CRT screen are equivalent to a beam width of 10mm. By successively installing the Beam Analyser at different distances from the laser, the beam diameter (1/e) can be measured and divergence can easily be calculated from these values. 4. Adjustment of Pulsed-Lasers For pulsed lasers it is suggestible (even not indispensable) to employ a memory oscilloscope. When a laser pulse meets the needle, a very narrow "peak" will appear on the screen in a position corresponding to that of the needle at the pulse instant. As the time goes on, the screen will be filled with many such "peaks", whose enveloping curve represents the laser's mode. To avoid a long waiting time with low repetition rate lasers, a synchronization signal is supplied by the LBA to drive a laser pulse when, after every revolution, the needle is in a slightly different position. A reset signal is also provided to erase the screen after every scanning. Furthermore the facility of locking the needle across the beam, enables the observation of the pulse's time-shape, point-to-point in the beam cross section. 5. Measurements of Focus The needle's high reflective surface and its moving speed make the LBA suitable for measurement of the focus diameter. The unit is displaced along the beam until the minimum beam diameter has been found. This measurement allows to determine the power density at the focus point, as well as the influence of lenses of different focal lengths and shapes. Distorted lenses or mirrors can be spotted by comparative measurement. SPECIFICATIONS The LBA is available in three different sizes: LBA1 for beam diameter till 25mm; 50(60) Hz scanning rate LBA2 for beam diameter till 40mm; 50(60) Hz scanning rate LBA3 for beam diameter till 60mm; 50(60) Hz scanning rate The detectors window is available either for CO2 or YAG laser, as well as for both The detectors amplifier is switchable in 4 gain ranges (0.02-1-3-10). The spatial resolution and the sensitivity depend linearly on the chosen gain. With gain 0.02 the following values are reached: spatial resolution: 4µm sensitivity: 0.3mV/mm 2 increasing the gain increases the sensitivity and reduces the resolution in the same factor. Output noise signal is always less than 5mV (rms) Please specify in your order required version and model, detector's window, supply voltage (220 or 110V) and frequency (50 or 60Hz). Dimension (mm) LBA1 : 187x89x185 / LBA2 293x130x287 / LBA3 360x150x355
LDS - Laser Diagnos c System To be able to influence the beam recursively or to get comparison values of the measurements, an evaluation system is needed which goes beyond the capacity of an oszillograph. The signals of an LBA can be made visible on a monitor with a PC (Windows based), a fast speed ADC-Plug-In board and the appropriate software (Laser Diagnostic System LDS). In this case the computer is able to do several operations as for example monitoring the beam An interesting application can be found for industrial production. The intensity distribution of the laser beam while correct configured will be stored. The actual signal is than during production constantly compared with the stored required information. The tolerance values for exceeding the correct values can be chosen. The deviation of the mode structure or intensity, that adversely affects the quality, is immediately detected and displayed on the computer audibly and visually. Since the signal height is directly proportional to the power, the highest power at optimal mode be adjusted fast and easy again. In addition all important laser beam parameters, like peak values, beam diameter at the point 1/e2 and the maximum value e/2 as well as the power/intensity are constantly displayed. For rapid pulsed lasers, the LDS averages up to 16 measurements. In this way, short -term variations which have in regard to the mode profile no importance, are reduced. A print of the display is possible at any time.
LDS - Laser Diagnos c System With a software extension, the distribution of the laser mode can be represented in 16 colours over the entire sectional view. Especially for long time testing, this view provides an excellent overview providing the user a quick and easy overview of the Mode structure. The 3-D representation of the laser diagnostic system provides beside the user friendliness urements. to also receive in a decreed manner a more in addition to user friendliness on account of the menu-driven functions via the possibility to information from the data supplied by the LBA. tensity with all needed information This so-called mountain view, provides at a glance an overview of the maximum power, the location of it in the beam as well as information about sub-maximums which appear for the first time in this view. From up to 440 measurements, at which the LBA is driven through the beam by means of a stepping-motor, a mountain view is built up with a resolution of 50µm. The built up picture can be viewed from all angles. As additional information is provided by means of so-called silhouettes, representing the course of the intensity maxima separately again. The LDS provides height line cuts which provide information about the beam diameter of a certain intensity. LDS and LBA are universal tools providing excellent laser beam analysis helping to optimise CO2 or YAG high performance laser usage.