Optical Metrology

21 Mar 2022

To learn more about optical metrology services provided by Shanghai Optics, visit: https://www.shanghai-optics.com/design/metrology.

Optical Metrology Overview

Optical metrology involves using light to set the standards of measurement. More generally, it can be defined as the science of measuring with light. Under this broader definition, it could include measurements that focus on the properties of light itself or measurements that use light to discover the properties (for instance, temperatures, dimensions, or distance) of other objects.

With state-of-the-art optical metrology equipment, Shanghai Optics is capable of producing and also testing precision optical components and systems. We inspect and qualify the produced parts in accordance with our customers’ specific requirements and MIL/SPEC. All the parts are shipped with inspection reports, material certificates and coating curves (if applicable).

Our advanced in-house metrology equipment enables us to test the parts for compliance with various international measurement standards, covering almost all the stages of optical production process.

We are committed to meeting our customers’ requirements starting from the procurement of raw materials. All orders are controlled and monitored in adherence to ISO: 9001 standards – from the incoming inspection of purchased materials to final step in the production process.

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Benefits of Optical Metrology

Optical metrology has the potential to be extremely precise; ultimately, it is only limited by quantum noise or laser noise that might block detection. As a rule, optical measurements can be quickly done, making optical metrology ideal for in-process measurements. Optical measurements do not require touch or contact, making it one of the most non-destructive measuring techniques available. It is suitable even for the most sensitive items or components, and is an integral part of quality control at our factory.

Optical Metrology in Action: Selected Examples

Measuring with Lasers

This subfield of dimensional metrology provides extremely fast, precise measurements of even very large measurement ranges. There are a number of different methods used, depending on the scale and requirements of the measurements. These methods include time of flight measurements, triangulation, phase shift methods and interferometry.

For time-of-flight measurements, a short laser pulse is sent out, and the time elapsed before a portion of it is reflected is measured.  Half of this round trip distance, divided by the velocity of light, is calculated to be the distance. This method is usually used for long distances, and accuracy is restricted by the accuracy in recording time: every 1 ns deviation leads to a spatial inaccuracies of 15 cm.

Optical Clocks

Optical clocks are based on ultra-precise measurements of optical frequencies, and are both more stable and more accurate than the atomic clocks which are widely used as the standard in time measurement. In fact, they are now being used to recalibrate standard atomic clocks against drifting. They are based on multi-TH electromagnetic oscillations, in contrast to cesium atomic clocks which rely on a transition at 9192631770 Hz. This allows optical clocks to outperforms atomic clocks by a very large margin; often by multiple orders of magnitude.

Optical Temperature Sensors

Optical temperature sensors typically use fiber optics to measure the temperature of an object or environment. These sensors are widely used in industry, for routine measurement as well as for disaster prevention. For instance, they may be used to protect against uncontrolled fire. The benefits of these sensors is that they don’t use electrical cables, are insensitive to electromagnetic interference, and are suited to a wide range of temperatures.

Optical Profilometers

An optical profilometer uses light to measure a surface profile. These instruments are non-contact, and provide more accurate profiling than traditional profilers such as an ordinary microscope. High resolution optical profilometers are often used for inspecting the surface of optical components such prisms, glass flats, and laser mirrors, and form an important part of our toolkit for surface analysis and quality control.  They are also used in semiconductor chip inspection, and in the manufacture of certain types of mechanical parts where a high quality surface finish is crucial. Optical profilometers include interferometers, interferometer microscopes, confocal scanning microscopes, focus variation microscopes, digital holographic microscopes, and triangulation sensors.

Optical Metrology at Shanghai Optics

At Shanghai Optics we use cutting-edge optical metrology to ensure that every optical component to leave our factory fully meets all applicable standards and is optimized to the application for which it is designed.  Our equipment includes coordinate measurement machines (CMMs), spectrophotometers, profilometers, and interferometers.

All the raw materials that are used in our production are purchased strictly according to the customer’s original prints or needs, including glass, metal, polishing materials, adhesive etc.

We have created operating procedures to ensure the full traceability of the raw material batches which were or will be used in our optical products.

As a larger manufacturer of custom lenses and high-precision optical assemblies with over 55 years of experience, we fully understand the significance of metrology to optical manufacturing. The pursuit of higher measurement accuracy prompts us to continue investing in optical test equipment and expanding our capabilities in optical metrology.

Surface quality and flatness of each of our optical components is tightly controlled. We also run extensive in-house optical and environmental testing to ensure our components will perform as expected in spite of temperature, shock and vibration, or humidity. Optical measurements allow us to ensure each of our wide range of components meets advertised specifications, and we are able to stand behind our products with complete confidence.

We also provide the optical components needed for your own in-house optical metrology, and our design experts would be happy to work with you to design and implement appropriate metrology for your industry or application.