Ariel

As described in the general introduction, the thermopile sensor has a series of bimetallic junctions. A temperature difference between any two junctions causes a voltage to be formed between the two junctions. Since the junctions are in series and the «hot» junctions are always on the inner, hotter side, and the «cold» junctions are on the outer, cooler side, radial heat flow on the disc causes a voltage proportional to the power input. Laser power impinges on the center of the thermopile sensor disk (on the reverse side of the thermopile), flows radially and is cooled on the periphery. The array of thermocouples measures the temperature gradient, which is proportional to the incident or absorbed power. In principle, the reading is not dependent on the ambient temperature since only the temperature difference affects the voltage generated and the voltage difference depends only on the heat flow, not on the ambient temperature.

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This document was created to assist our valued customers in the proper care and maintenance of Ophir thermal laser power sensors. The following information is for reference only. If you have any reason to believe that the sensor is no longer performing within the original specifications,we always recommend that you send it in for repair and/or recalibration by our trained technicians to bring the unit back to the proper NIST traceable standards. We believe that Ophir thermal sensors can be used for many years without any repairs when used with the proper laser optical setup. We hope that this document will enable you to also enjoy the long life and reliable results for which Ophir-Spiricon is known.

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The selection of a sensor to accurately measure the power of a laser or energy of a pulsed laser can seem like a simple and easy procedure. However, many times the selection process is limited to choosing a sensor that only meets the range of power or energy to be measured, leaving out several other essential criteria of the laser specifications; that without their consideration, can allow the wrong sensor to be selected, the laser to be measured inaccurately and likely to cause the sensor to fail prematurely.

Watch Our Laser Measurement Video

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An explanation of how we do this is provided below (A). In addition, a recent check of Ophir’s 5000W head by PTB in Germany shows excellent agreement between our calibration and their standards. The details of the correspondence between our sensor and their standard at powers up to 1400W is included here (B).

A. High Power Measurement Calibration Method and Estimated Accuracy of Models 5000W and 10K-W

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The entire aperture senses power, so you can use the whole head. That said, a beam in the inner 50% of the surface area (about 70% of the diameter) is specified by Ophir to be uniform within +/-2%. The sensitivity around the edges might be a little less, but generally the sensitivity doesn’t vary by more than +/-2% over the entire aperture.

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We are often asked about the specified ranges of various ambient conditions (temperature, humidity, etc.) for Ophir instruments. In this article we will clarify the effects of these conditions on laser measurements, so you’ll be able to use your Ophir laser measurement instrument effectively.

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Ophir water cooled sensors are designed to measure high powers in a relatively compact package. In order for the sensor to operate properly, the water flow rate, temperature and temperature stability have to be in the right range. For best performance of the sensor, the water flow rate should be the recommended rate. If the user system is not able to reach the recommended rate, then the minimum rate can be used and the sensor will meet spec but there may be some degradation of response time and linearity... 阅读更多...

This document discusses the interpretation and basis for stated measurement accuracy of Ophir Laser Power/Energy meters.
1. General Discussion
2. Combination of Errors and Total Error
3. Analysis of Power and Energy Calibration Errors
4. Detailed Analysis of Power and Energy Calibration Errors

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19th century British physicist and engineer William Thomson, 1st Baron Kelvin, was the first to say, “If you can’t measure it, you can’t improve it.” When applying this principle to improving laser-based processes, there are a variety of parameters that must be measured. Given the continuously rising power of laser systems in material processing, the requirements for measurement systems are more challenging than ever. Which technologies are available to measure high-power lasers? How often should they be measured? What measurements should be tracked? When this data is collected, what should be done with it? 阅读更多...

Each given range represents one level of gain of an internal amplifier. The electronics, as always, have a limited Dynamic Range. If the measured signal is too low, in other words near the bottom of the range, then it may be lost in the noise and the reading will be inaccurate and noisy. If it’s too high – there may be saturation issues. To give an instrument a usefully wide dynamic range, multiple scales or ranges are used. Switching from range to range can be automatic (“Autorange”), or manual. Autoranging simply starts automatically at the least sensitive range and works its way down the ranges, sampling the signal as it goes, till it finds a range at which the signal is properly detected. Note, by the way, that only in POWER mode is Autoranging available. If we are working in Single Shot Energy mode, there is no Autoranging – simply because when we are measuring a single pulse, the instrument has no opportunity to work its way down the ranges as in Power mode.

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Power and Single Shot Energy Sensors
Ophir provides two types of power sensors: Photodiode sensors and Thermal sensors. Photodiode sensors are used for low powers from picowatts up to hundreds of milliwatts and as high as 3W. Thermal sensors are for use from fractions of a milliwatt up to thousands of watts.
Thermal sensors can also measure single shot energy at pulse rates not exceeding one pulse every ~5s.

Repetitive Pulse Energy Sensors
For higher pulse rates, Ophir has pyroelectric energy sensors able to measure pulse rates up to tens of KHz. These are described in the energy sensor section, section 1.3.

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Measuring the performance of a laser has possible for a number of years and is accomplished with a variety of techniques. These electronic laser measurement solutions give the laser user more relevant, time-based data that shows trends in laser performance rather than single data points. While these solutions have provided laser users with the ability to present data in a simple and easy to understand manner, the application of the data still seems to be unclear to many laser users. 阅读更多...

Laser-based additive manufacturing is transforming industrial processes and opening up new horizons in a variety of application areas. In the aerospace and automotive industries, for example, it makes it efficient to manufacture intricate parts according to lightweight construction principles; in medical technology, it has expanded the range of prostheses and orthoses; and in toolmaking, it shortens the time it takes to implement new requirements. Long since AM applications have attained a level of maturity that allows for series production – but when it comes to checking the laser 阅读更多...

MKS Instruments recognized early on that measuring the laser beam in laser-based AM processes would become the key to efficient production. Four years ago, the company introduced the first measuring device that could assess – without any contact – the caustics of the laser beam on the building plane. This was followed by the launch of Ophir Ariel, an innovative power meter for AM applications. Then at Laser World of Photonics 2022 in Munich, the manufacturer introduced Ophir BeamPeek ™, an integrated measuring system that bundles the various measuring tasks into one robust 阅读更多...