OPMs typically report the power either on a watts scale covering picowatts to milliwatts, or in decibel-milliwatts (dBm), which is the logarithmic ratio of the measured power to the reference value of one milliwatt.

TPL Vision (Perth, Scotland, UK) Product Manager Jack McKinley says choosing flexible lighting products reduces risks to an application’s feasibility posed by unknown factors in the current or future production environment.

Outside the realm of inspection in manufacturing, lighting challenges abound in machine vision applications in logistics and warehousing. One example involves a portal system, which scans barcodes in automated or smart warehouses.

or light microscope (vs./ an electron microscope). ... Base: The bottom of the microscope, used for support. Illuminator: A steady light source (110 volts) used ...

With so much to consider, missteps abound. To get insights on how to avoid, or solve, common pitfalls in illumination planning and execution, Vision Systems Design asked experts at a handful of lighting companies to share their thoughts. We’ve included their comments here.

Keep your eyes safe with our blue light protection glasses. These UV-blocking glasses are treated with a polymer that acts as a shield against harmful ...

Additionally, engineers must ensure that all these techniques conform to tight power loss budgets and signal-to-noise tolerances using high-precision test and measurement devices like optical power meters, tunable laser sources, polarization synthesizers, and optical time domain reflectometers.

EXFOlight meter

(More information from Vision Systems Design on addressing lighting challenges in medical device and pharmaceutical inspection is available here.)

An example is the company’s Multispectral Exolight v2.0, which is available in versions covering up to six wavelengths including the short-wave infrared (SWIR) spectrum.

An optical power meter (OPM) measures the power levels of light signals in devices that transmit data or power using light.

For the characterization of fiber optic components, an OPM is combined with a light source, typically a laser with a wavelength equivalent to the use case of the component under test.

VIAVIlight meter

Proper lighting is crucial to the success of machine vision applications. Without it, images will not show enough visual information about the important features of an item.

Lindsey Sullivan, technical marketing manager at CCS America (Woburn, MA, USA), agrees, saying, “It is important to test and solve the application at the beginning of the design process. Once the required lighting is understood, the design of the inspection system can account for the positioning of the sample, size, working distance, color (and) geometry of the light.”

Modern data centers and cloud computing services require 400G, 800G, and even 1.6T ethernet to keep up with the bandwidth demands of their exponentially growing customer base.

You typically combine OPMs with other fiber optic test instruments, but they are sometimes used independently as well. We review both types of applications below.

Dynamic range is the ratio of the highest power to the lowest power. A high dynamic range enables many applications. For example, if there is a problem like a connector fault or a break in the cable, it can cause the optical power to drop very low. An OTDR with a high-dynamic range OPM can detect and troubleshoot these problems.

As Brett Thrailkill, application support and inside sales representative at Advanced Illumination (Rochester, VT, USA), explains, “Unfortunately, many users have the misconception that proper machine vision lighting doesn’t need to be considered until the end of the system design process. This often leads to cost overruns, inferior lighting, and delays in production timelines. To prevent this, we encourage all application engineers to consider lighting options early in the development process.”

Thermopile sensors absorb light and heat up to generate a temperature difference between two thermocouple surfaces. This temperature difference between two dissimilar metals generates a proportional voltage.

Fiberoptic PowerMeterandLightsource

A light source is an instrument that emits light signals with different characteristics like wavelengths, power levels, or timings. The light is emitted by light-emitting diodes (LEDs) or lasers. A light source can be of many types depending on the characteristics of its light emissions and testing purpose:

“There are also a variety of other optical accessories that are easy to install on the light. This means you can get a different lighting geometry without needing to purchase a new light,” saving money and time on redesign work that can cause delays in projects, explains Mariann Kiraly, US sales manager for EFFILUX.

Numerous experts agreed on the most common pitfall: Waiting until the tail end of the design process to address lighting for a machine vision application.

Its frequency is able to penetrate the nucleus of an organism, destroying its DNA and effectively killing the germs. As a result, UV lamps are used in areas ...

A detector houses the sensor and its related filtering and processing circuitry. It's typically an internal component of the OPM.

This is why Metaphase developed “light sources where, for example, the end of a linear bar light will be brighter at the ends compared to the middle of the light to compensate for lens image attenuation around the perimeter of the field of view,” he explains.

OPMs come in various form factors. The optical sensor is either part of an internal detector circuit or housed in an external optical head for flexible positioning.

You can use an OPM independently to measure the power level of a fiber optic signal. It essentially measures the instantaneous total energy of all the photons coming out of a fiber optic cable.

At Keysight, we offer you a wide range of standalone as well as modular optical power meters and related test equipment for optical power measurement applications. Let's look at some of our key products.

The company’s Modular Tiny Bar Light (M-TBAR), which is designed specifically for confined spaces such as in robotics applications, offers flexibility, the company says. The product allows users to change the beam angle with the company’s angle changers, which are micro-optic diffusers that can be used to widen the beam angle. The light also offers strobe overdrive illumination.

Avionics and defense systems rely on optical fiber for speed and bandwidth. The high level of reliability and redundancy in these systems requires heavy use of OPMs for testing and maintenance.

2024226 — For transparent samples in light microscopy, dark field illumination ... bright field illumination. For objectives with a Numerical Aperture ≤ ...

Additionally, the total uncertainty is determined by other factors, including sensor uniformity, active area of the sensor, linearity, and temperature. Accounting for them, uncertainty can go as high as 5%-6%.

These lights will illuminate your countertop or bar top, providing plenty of task and accent lighting where you need it most.

An example of this type of lighting solution is the Lightgistics series from Smart Vision Lights. The lights feature Dual OverDrive, which combines SVL’s Deca OverDrive and standard OverDrive engines, allowing end users to attach polarizers while retaining light output to handle any speed.

To solve the problem, he says ProPhotonix sold the company the RGB-White COBRA MultiSpec LED, which has individual color and intensity controls that engineers access through a graphical user interface (GUI). This allows them to “tune the light to optimize contrast across the whole grayscale image resulting in accurate image acquisition regardless of the color of the capsule.”

Hardy at Spectrum says another pitfall is not considering the production environment during the lighting selection process. “We also see many customers choosing the wrong type of light for the environment. For example, using a standard backlight or dome light near a CNC (computer numerical control) machine where coolant splatters on the light and over time will wick inside causing internal corrosion and eventually failure.” When designing a machine vision application for harsh environments, choosing a light with a higher IPrating is a better option, he explains.

To choose from so many options, it is important to consider the characteristics of the object to be imaged, such as size, shape and color; the spatial relationship between the object, light and camera; and how the light is reflected or absorbed by the object and background. (Vision Systems Design offers more explanation here.)

There are thousands of lighting options to choose from including those that are halogen, incandescent, fluorescent, compact-fluorescent, plasma-type, high-intensity discharge (HID), Xenon, light-emitting-diode (LED), fiber optic, and structured light.

Modern high-speed networks run on optical fiber because of its incredible speed and virtually unlimited capacity. Optical power meters are a key element in the optimization and maintenance of such optical networks and of their components.

InLine 2.0 Modular Lighting pairs flawlessly with Robern medicine cabinets and mirrors for exceptional design flexibility and a complete experience.

The Lightwave Solution Platform offers expandable optical mainframes like the 8164B that accept specialized modules like sensors and loss detectors.

David Hardy, vice president and design engineer for Spectrum Illumination (Montague, MI, USA), says that white lights also provide the most flexibility over time if a product’s color changes in a future iteration. “For example, the part under inspection is red or white, and a red light is chosen. But if a part color of green or blue is added later, it can appear quite dark as green and blue colors are somewhat opposite red on the color wheel. In this case, using a white light initially would have been better, or even an infrared light to remove the color.”

LED Linear™ supplies high quality linear LED lighting solutions based on flexible printed circuit boards worldwide. Our offer is a cost effective, ...

CCS America’s PD4 Series lighting controller is designed for these types of situations, allowing engineers to program up to 16 steps of on/off for the lights in an application.

Typical bench-top and handheld optical power meters support one or two detectors or optical heads. High-end multi-port meters support up to eight or more detectors or optical heads. Some rack-mounted meters support hundreds of ports.

Linda Wilson joined the team at Vision Systems Design in 2022. She has more than 25 years of experience in B2B publishing and has written for numerous publications, including Modern Healthcare, InformationWeek, Computerworld, Health Data Management, and many others. Before joining VSD, she was the senior editor at Medical Laboratory Observer, a sister publication to VSD.

In contrast, an optical head is a detector available as a separate external attachment for flexible positioning. You can easily detach an optical head and replace it with another better suited to the light source or fiber being tested.

For simple everyday testing of cables, OTDR is often used along with a Visual Fault Locator (VFL). The OTDR measures the distance to problem points while the VFL enables visual checking and verification.

All these fiber networks use optical power meters and related instruments for their testing. For example, last-mile passive optical networks (PONs) are tested using special handheld optical power meters called PON power meters.

PowerMeter fiberoptic test

How does a linearly polarized wave interact with a linear polarizer? 6. Malus' Law. In general, the intensity of a linearly polarized light passing through ...

An OTDR is an advanced fiber optic tester that can measure optical loss between any two points in a fiber or optical assembly. You can use it to detect fiber breakages, loose connections, faulty or dirty connectors or couplers, and other problems as shown in this OTDR trace of power in decibels (dB) against distance.

Such high-speed connections are needed for a variety of connections, from backplane interconnects to the connections between processors and accelerators like graphical processing units (GPUs) and field-programmable gate arrays (FPGAs). These accelerators are used for a variety of modern tasks like artificial intelligence inference and high-frequency trading.

Closely related are the sensor's and meter's spectral responsivity curve, which shows the responsivity of the sensor at each wavelength. Responsivity is the ratio of the generated current or voltage at the sensor per watt of incident optical power. The spectral responsivity curve tells you the wavelength range where the sensor and meter show linearity, i.e., their reading is linearly proportional to the actual input energy.

The meaning of DOME LIGHT is a light in the ceiling (as of an automobile).

Overlooking the Impact of the Sensor and Lens on Illumination Mark Kolvites, sales manager at Metaphase Lighting Technologies (Bristol, PA, USA), says, “Another pitfall is overlooking the fact that the lens and camera sensor are also part of the optical path for the captured image, which could affect the illumination implemented. For example, the wider the angle of the camera lens, the more optical distortion around the perimeter of the field of view, making the image look non-uniform, even though the light itself might be uniform.” This is why Metaphase developed “light sources where, for example, the end of a linear bar light will be brighter at the ends compared to the middle of the light to compensate for lens image attenuation around the perimeter of the field of view,” he explains. An example is the company’s Multispectral Exolight v2.0, which is available in versions covering up to six wavelengths including the short-wave infrared (SWIR) spectrum.

Mark Kolvites, sales manager at Metaphase Lighting Technologies (Bristol, PA, USA), says, “Another pitfall is overlooking the fact that the lens and camera sensor are also part of the optical path for the captured image, which could affect the illumination implemented. For example, the wider the angle of the camera lens, the more optical distortion around the perimeter of the field of view, making the image look non-uniform, even though the light itself might be uniform.”

An optical loss test set (OLTS) compares power levels with and without a fiber link to determine the link's net power loss. The fiber link may be a simple fiber or an assembly of fibers, splices, fusion splicers, connectors, attenuators, and other optical devices.

Optical power meters can measure the power of both single-mode and multimode fibers. In single-mode fiber, the rays travel down its entire length without any internal reflection at all. In multimode fiber, multiple rays enter at different angles and possibly have different wavelengths as well.

Underestimating the speed necessary for inline inspection in some environments also could lead to illumination challenges. Advanced Illumination updated its BL2 Backlights to increase brightness, allowing for higher throughput. The lights are also designed for scalability, expandable in 1 in increments up to 46 in in length or width. They can be operated in operated in continuous or overdrive strobe modes.

To test its net loss, connect a suitable OLS to one end of the link and the power meter to the other end. Set the meter to the same wavelength as the OLS and measure the power.

The sensor is the most critical component. It converts the incident light energy into an electrical signal. Different types of sensors are available depending on their working principles as described below.

For example, he says TPL Vision’s customers often encounter different application conditions than what was tested in the lab. As a result, “higher brightness may be required (solved by overdrive products), different ambient conditions may need a different lighting setup, or integration may be different than anticipated. This is precisely where flexibility can be beneficial,” he says.

Kinney adds that lighting manufacturers have developed specialized lighting products that feature overdrive, “where the light is operated at multiples of the steady state current for short periods to create a brighter strobe. This allows the use of polarization needed to effectively work in portal systems while still having enough light for the short exposure periods required to image without motion blur at the item passes at high speed through the system.”

FiberOptic PowerMeterprice

Sometimes the best choice is to darken the object—particularly if the goal is to read printed codes or words. By illuminating red print on a white envelope with a green light, you’ll get the clearest image of the print, Advanced Illumination says on its website.

In general, according to Advanced Illumination, a light that is of a similar color as an object will reflect and thus brighten the object while a light on the opposite side of the color wheel will darken the object.

A typical OPM is calibrated to be linear in the 10 dBm (10 milliwatt) to -50 dBm (10 nanowatt) range. In this range, a change in the actual power results in a linearly proportional change in the measured power.

Modern telecommunication core networks, both wired and wireless, are optical fiber networks because of their superb speed and capacity. Even the undersea cables connecting continents are part of the optical network.

This is why engineers choose white lights, which comprise both warm and cool colors, for many applications, and especially those involving a color camera. Colored lights are used with monochrome cameras.

EFFI-FLEX2 from EFFILUX (Les Ulis, France) also offers flexibility, allowing engineers to adjust the emitting angle, uniformity, and operating mode (overdrive, adjustable strobe, and dimmable continuous mode).

In many markets, even the last-mile broadband access networks use technologies like fiber-to-the-home (FTTH) and fiber-to-the-X (FTTX) for high-speed internet. Fiber is even replacing ethernet inside our homes and offices around the world.

Common machine vision applications in which illumination is part of the solution involve inspecting products for defects before they leave the manufacturing plant or reading barcodes or other alphanumeric data on products or packages as they move through the logistics pipeline.

An OTDR contains an optical power meter as an internal component for testing power between two points. A typical OTDR schematic is shown below.

Available in ring and linear formats, the new lights offer direct connection and control through a camera’s trigger output.

(More information from Vision Systems Design on illumination techniques for machine vision applications in logistics is available here.)

The most recent addition, introduced in 2018, is the Washdown Monster Dome Light, which is designed to remove glare from product images without a loss in intensity.

“By using cross-polarization, a technique where a linear polarizer is placed over a light source (transmitter) and another rotating linear polarizer is attached over the camera lens (receiver), the light rays coming from the surface of the item are reduced while the part of the light energy that penetrates the surface is passed through the receiving polarizer. Since the cross-polarization effect reduces the light from the surface, glare and other specular effects from glossy plastic surfaces is reduced,” he says.

High-sensitivity meters may range from as low as -110 dBm to as high as +30 dBm but typically only for single-mode fiber testing.

Simon Stanley, director of technology at ProPhotonix (Salem, NH, USA) also provides an example of how a customer in the medical device industry addressed the issue of color. “The customer was inspecting data matrix codes on different colored capsules. They were limited to using a high-resolution, but monochrome, Cognex In-Sight 9000 camera in line-scan mode; and a white line light and found that for some of the colored capsules, the images did not have adequate contrast.”

In this guide, you got an overview of optical power meters and their internals. Today's fastest petabyte-scale data networks wouldn't be possible without optical fibers. Photonics is revolutionizing other sectors as well, from avionics to health care, from quantum photonics to AI/ML.

A sensor amplifier circuit boosts the electrical signal from the sensor for reliable detection and measurement. Since sensor response is very sensitive to the input signal's wavelength, the amplifier should be carefully calibrated to boost the signal to a level based on the wavelength.

However, brightness would be an advantage if the goal is to brighten or enhance the contrast between an object and its background, such as to detect wrapped candy on a conveyor belt.

However, OPMs may also be displayless, or modular platforms meant for high-throughout measurements of multiple fibers or multiple ports. They just collect and stream the data from all channels to an attached computer.

Reading those barcodes accurately has become increasingly complicated, requiring a creative approach to lighting. As Steve Kinney, director of training, compliance and technical solutions for Smart Vision Lights (Norton Shores, MI, USA), explains, “Today’s scanning portal must read through the clear outer packaging on individual items, through poly bags to see the item inside, through clear films placed over shipping labels for weather resistance, or even through shrink wrap holding a pallet together to read the barcodes of the boxes comprising the pallet. In these demanding instances, not only do the various films and packaging cause problems seeing the barcodes to be read, but they also have uneven glossy surfaces that make the imaging even harder.”

Whether an application involves reading barcodes on packages or inspecting products, these experts say they’ve described some of the most common missteps in designing and implementing illumination solutions for machine vision applications.

Fiber light metervs OTDR

Lighting controllers also allow for flexibility, particularly in situations in which more than one lighting solution is deployed, explains Sullivan at CCS America. Some examples: multiple lights are on at once but at different intensity settings to avoid overexposing an image or multiple lights go on/off in sequence to capture multiple images. “For example, a controller can turn on a flat dome light for a bright field image, then a low-angle light for a dark field image,” she says.

The 8162xCand 8162xB families offer a variety of optical heads for flexible positioning and interchangeable connectivity with the N774xC meters.

Whatever industry you're in, Keysight is your reliable test and measurement vendor. We also provide expert-level, accredited calibration services for your optical power meters of any brand.

If a strongly absorbing crystal, e.g. polaroid or tourmaline, is placed in the light path, the rays are strongly absorbed in all directions except one, and the ...

The term "optical power meter" may sound generic, but in popular usage, it specifically implies a fiber optic power meter. For light power measurements outside the field of fiber optics, alternative terms like light meter, laser power meter, and photometer are more common.

Hardy notes that the company’s IP68 Washdown series of LEDs is designed for these types of environments. The series includes ring lights, dome lights, spotlights and linear lights.

Of these, LEDs are the most common choice for machine vision applications because they have long life spans, can be left on continuously, and come in many sizes, shapes and colors. LED lighting choices also span the visible, ultraviolet (UV), narrow-band and broad-band visible and infrared (IR) spectrum.