Understanding and manipulating the polarization of light is crucial for many optical applications. Optical design frequently focuses on the wavelength and intensity of light, while neglecting its polarization. Polarization, however, is an important property of light that affects even those optical systems that do not explicitly measure it. The polarization of light affects the focus of laser beams, influences the cut-off wavelengths of filters, and can be important to prevent unwanted back reflections. It is essential for many metrology applications such as stress analysis in glass or plastic, pharmaceutical ingredient analysis, and biological microscopy. Different polarizations of light can also be absorbed to different degrees by materials, an essential property for LCD screens, 3D movies, and glare-reducing sunglasses. 

Understanding Polarization

Light is an electromagnetic wave, and the electric field of this wave oscillates perpendicularly to the direction of propagation. Light is called unpolarized if the direction of this electric field fluctuates randomly in time. Many common light sources such as sunlight, halogen lighting, LED spotlights, and incandescent bulbs produce unpolarized light. If the direction of the electric field of light is well defined, it is called polarized light. The most common source of polarized light is a laser.

Depending on how the electric field is oriented, we classify polarized light into three types of polarizations:

• Linear polarization: the electric field of light is confined to a single plane along the direction of propagation (Figure 1). 
• Circular polarization: the electric field of the light consists of two linear components that are perpendicular to each other, equal in amplitude, but have a phase difference of π/2. The resulting electric field rotates in a circle around the direction of propagation and, depending on the rotation direction, is called left- or right-hand circularly polarized light (Figure 2). 
• Elliptical polarization: the electric field of light describes an ellipse. This results from the combination of two linear components with different amplitudes and/or a phase difference that is not π/2. This is the most general description of polarized light, and circular and linear polarized light can be viewed as special cases of elliptically polarized light (Figure 3).  

The two orthogonal linear polarization states that are most important for reflection and transmission are referred to as p- and s-polarization. P-polarized (from the German parallel) light has an electric field polarized parallel to the plane of incidence, while s-polarized (from the German senkrecht) light is perpendicular to this plane.

Manipulating PolarizationPolarizers

In order to select a specific polarization of light, polarizers are used. Polarizers can be broadly divided into reflective, dichroic, and birefringent polarizers. More detailed information on which type of polarizer is right for your application can be found in our Polarizer Selection Guide.

Reflective polarizers transmit the desired polarization while reflecting the rest. Wire grid polarizers are a common example of this, consisting of many thin wires arranged parallel to each other. The light that is polarized along these wires is reflected, while light that is polarized perpendicular to these wires is transmitted. Other reflective polarizers use Brewster’s angle. Brewster’s angle is a specific angle of incidence under which only s-polarized light is reflected. The reflected beam is s-polarized and the transmitted beam becomes partially p-polarized.

Dichroic polarizers absorb a specific polarization of light, transmitting the rest; modern nanoparticle polarizers are dichroic polarizers.

Birefringent polarizers rely on the dependence of the refractive index on the polarization of light. Different polarizations will refract at different angles and this can be used to select certain polarizations of light.

Unpolarized light can be considered a rapidly varying random combination of p- and s-polarized light. An ideal linear polarizer will only transmit one of the two linear polarizations, reducing the initial unpolarized intensity I₀ by half, for linearly polarized light with intensity I₀, the intensity transmitted through an ideal polarizer, I, can be described by Malus’ law.

Where θ is the angle between the incident linear polarization and the polarization axis. We see that for parallel axes, 100% transmission is achieved, while for 90° axes, also known as crossed polarizers, there is 0% transmission. In real-world applications the transmission never reaches exactly 0%, therefore, polarizers are characterized by an extinction ratio, which can be used to determine the actual transmission through two crossed polarizers.

Waveplates

While polarizers select certain polarizations of light, discarding the other polarizations, ideal waveplates modify existing polarizations without attenuating, deviating, or displacing the beam. They do this by retarding (or delaying) one component of polarization with respect to its orthogonal component. To help you determine which waveplate is best for your application, read Understanding Waveplates. Correctly chosen waveplates can convert any polarization state into a new polarization state and are most often used to rotate linear polarization, to convert linearly polarized light to circularly polarized light, or vice versa.

Applications

Implementing polarization control can be useful in a variety of imaging applications. Polarizers are placed over a light source, lens, or both, to eliminate glare from light scattering, increase contrast, and eliminate hot spots from reflective objects. This either brings out more intense color or contrast or helps to better identify surface defects or other otherwise hidden structures.

Reducing Reflective Hot Spots & Glare

In Figure 5, a linear polarizer was placed in front of the lens in a machine vision system to remove obfuscating glare such that an electronic chip could be clearly seen. The left image (without polarizer) shows randomly polarized light scattering off of the many glass surfaces between the object and the camera sensor. Much of the chip is obscured by Fresnel reflection of the unpolarized light. The image on the right (with polarizer) shows the chip without glare obscuring any of the object details, allowing the chip to be viewed, analyzed, and measured without obstruction.

The same phenomenon can be seen in the Figure 6. In the left image (without polarizer), unpolarized light from the sun is interacting with the windows of the Edmund Optics building and most of this light is reflecting off the windows. In the right image, a polarizing filter has been applied such that the reflected light, rich in one polarization type, is being blocked from the camera sensor and the photographer, using the other polarization type, can see into the building more easily.

Another characteristic way to see how polarizers reduce reflective glare is by viewing water surfaces. In Figure 7, the surface of the water appears reflective in the left image, obscuring what is below the surface. On the right, however, the rocky debris on the floor of the body of water is much more clearly visible. 

Hot spots are highly reflective portions of a field within a more diffuse reflecting field. In Figure 8, a polarizer is placed in front of the lens of a camera as well as over the light source illuminating the scene to reduce hot spots.

Read more: https://www.edmundoptics.eu/knowledge-center/application-notes/optics/introduction-to-polarization/?utm_source=press_release&utm_medium=print&utm_campaign=presse_box&utm_content=app_note_2&utm_term=marketplace

EO’s presence at the event, in both exhibiting and speaking capacities, underscored its dual role as a major manufacturer, not just for the region but also for global customers, and an engaged partner within Southern Arizona’s expanding optics and photonics cluster, “Optics Valley”, a committee of the Arizona Technology Council. The award affirms that advanced optics manufacturing is not only thriving in the region but also shaping local industry growth, workforce development, and supply-chain capability.

“Receiving this award from the Arizona Technology Council reinforces the strength and momentum of our Tucson operations,” said Katie Schwertz, a Senior Manager in the Edmund Optics Tucson facility, and chair of the Optics Valley committee. “Our team is committed to advancing precision manufacturing and supporting the continued growth of the optics and photonics community in Southern Arizona and beyond.”

The recognition reflects EO’s contribution to regional job creation, technology capability building, and the elevation of Arizona’s visibility as a hub for advanced manufacturing. For customers, suppliers, and technical talent across optics, photonics, aerospace, defense, and industrial manufacturing, the award further confirms EO’s local-to-global impact.

With this momentum, EO is well-positioned to expand its role in strategic sectors including aerospace, defense, autonomous systems, and advanced imaging. The company anticipates new partnership opportunities within the Arizona innovation ecosystem as demand for precision-manufactured optical systems continues to grow and is well equipped to serve its global customers with an ever-evolving set of capabilities.

Read more from the press release from the Arizona Technology Council here:

https://www.aztechcouncil.org/news/arizona-technology-council-honors-six-southern-arizona-companies-at-tech-and-business-expo/

Focal Length

The focal length of a lens is a fundamental parameter that describes how strongly it focuses or diverges light. A large focal length indicates that light is bent gradually while a short focal length indicates that the light is bent at sharp angles. In general, lenses with positive focal lengths converge light while lenses with negative focal lengths cause light to diverge, although there are some exceptions based on the distance from the lens to the object being imaged.

Field of View

Field of view describes the viewable area that can be imaged by a lens system. This is the portion of the object that fills the camera’s sensor. This can be described by the physical area which can be imaged, such as a horizontal or vertical field of view in mm, or an angular field of view specified in degrees. The relationships between focal length and field of view are shown below.

Fixed Focal Length Lenses

A fixed focal length lens, also known as a conventional or entocentric lens, is a lens with a fixed angular field of view (AFOV). By focusing the lens for different working distances (WDs), differently sized field of view (FOV) can be obtained, though the viewing angle is constant. AFOV is typically specified as the full angle (in degrees) associated with the horizontal dimension (width) of the sensor that the lens is to be used with.

Note: Fixed focal length lenses should not be confused with fixed focus lenses. Fixed focal length lenses can be focused for different distances; fixed focus lenses are intended for use at a single, specific WD. Examples of fixed focus lenses are many telecentric lenses and microscope objectives.

The focal length of a lens defines the AFOV. For a given sensor size, the shorter the focal length, the wider the AFOV. Additionally, the shorter the focal length of the lens, the shorter the distance needed to obtain the same FOV compared to a longer focal length lens. For a simple, thin convex lens, the focal length is the distance from the back surface of the lens to the plane of the image formed of an object placed infinitely far in front of the lens. From this definition, it can be shown that the AFOV of a lens is related to the focal length (Equation 1), where f is the focal length and H is the sensor size (Figure 1).

In general, however, the focal length is measured from the rear principal plane, rarely located at the mechanical back of an imaging lens; this is one of the reasons why WDs calculated using paraxial equations are only approximations and the mechanical design of a system should only be laid out using data produced by computer simulation or data taken from lens specification tables. Paraxial calculations, as from lens calculators, are a good starting point to speed the lens selection process, but the numerical values produced should be used with caution.

When using fixed focal length lenses, there are three ways to change the FOV of the system (camera and lens). The first and often easiest option is to change the WD from the lens to the object; moving the lens farther away from the object plane increases the FOV. The second option is to swap out the lens with one of a different focal length. The third option is to change the size of the sensor; a larger sensor will yield a larger FOV for the same WD, as defined in Equation 1.

While it may be convenient to have a very wide AFOV, there are some negatives to consider. First, the level of distortion that is associated with some short focal length lenses can greatly influence the actual AFOV and can cause variations in the angle with respect to WD due to distortion. Next, short focal length lenses generally struggle to obtain the highest level of performance when compared against longer focal length options (see Best Practice #3 in Best Practices for Better Imaging). Additionally, short focal length lenses can have difficulties covering medium to large sensor sizes, which can limit their usability, as discussed in Relative Illumination, Roll-Off, and Vignetting.

Another way to change the FOV of a system is to use either a varifocal lens or a zoom lens; these types of lenses allow for adjustment of their focal lengths and thus have variable AFOV. Varifocal and zoom lenses often have size and cost drawbacks compared to fixed focal length lenses, and often cannot offer the same level of performance as fixed focal length lenses.

Using WD and FOV to Determine Focal Length

In many applications, the required distance from an object and the desired FOV (typically the size of the object with additional buffer space) are known quantities. This information can be used to directly determine the required AFOV via Equation 2. Equation 2 is the equivalent of finding the vertex angle of a triangle with its height equal to the WD and its base equal to the horizontal FOV, or HFOV, as shown in Figure 2. Note: In practice, the vertex of this triangle is rarely located at the mechanical front of the lens, from which WD is measured, and is only to be used as an approximation unless the entrance pupil location is known.

Once the required AFOV has been determined, the focal length can be approximated using Equation 1 and the proper lens can be chosen from a lens specification table or datasheet by finding the closest available focal length with the necessary AFOV for the sensor being used.

The 14.25° derived in Example 1 (see white box below) can be used to determine the lens that is needed, but the sensor size must also be chosen. As the sensor size is increased or decreased it will change how much of the lens’s image is utilized; this will alter the AFOV of the system and thus the overall FOV. The larger the sensor, the larger the obtainable AFOV for the same focal length. For example, a 25mm lens could be used with a ½” (6.4mm horizontal) sensor or a 35mm lens could be used with a 2/3” (8.8mm horizontal) sensor as they would both approximately produce a 14.5° AFOV on their respective sensors. Alternatively, if the sensor has already been chosen, the focal length can be determined directly from the FOV and WD by substituting Equation 1 in Equation 2, as shown in Equation 3.

As previously stated, some amount of flexibility to the system’s WD should be factored in, as the above examples are only first-order approximations and they also do not take distortion into account.

Calculating FOV Using a Lens with a Fixed Magnification

Generally, lenses that have fixed magnifications have fixed or limited WD ranges. While using a telecentric or other fixed magnification lens can be more constraining, as they do not allow for different FOVs by varying the WD, the calculations for them are very direct, as shown in Equation 4.

Since the desired FOV and sensor are often known, the lens selection process can be simplified by using Equation 5.

If the required magnification is already known and the WD is constrained, Equation 3 can be rearranged (replacing HFOV with magnification) and used to determine an appropriate fixed focal length lens, as shown in Equation 6.

Be aware that Equation 6 is an approximation and will rapidly deteriorate for magnifications greater than 0.1 or for short WDs. For magnifications beyond 0.1, either a fixed magnification lens or computer simulations (e.g. Zemax) with the appropriate lens model should be used. For the same reasons, lens calculators commonly found on the internet should only be used for reference. When in doubt, consult a lens specification table.

Note: Horizontal FOV is typically used in discussions of FOV as a matter of convenience, but the sensor aspect ratio (ratio of a sensor’s width to its height) must be taken into account to ensure that the entire object fits into the image where the aspect ratio is used as a fraction (e.g. 4:3 = 4/3), Equation 7.

While most sensors are 4:3, 5:4 and 1:1 are also quite common. This distinction in aspect ratio also leads to varying dimensions of sensors of the same sensor format. All of the equations used in this section can also be used for vertical FOV as long as the sensor’s vertical dimension is substituted in for the horizontal dimension specified in the equations.

Read more: https://www.edmundoptics.eu/knowledge-center/application-notes/imaging/understanding-focal-length-and-field-of-view/?utm_source=press_release&utm_medium=print&utm_campaign=presse_box&utm_content=app_note_1&utm_term=marketplace

Gebaseerd op de grote vraag op het gebied van biowetenschappen, halfgeleiderindustrie en fabrieksautomatisering, heeft de Summit tot doel industrie-experts, vernieuwers en "thought leaders“ samen te brengen om de nieuwste ontwikkelingen op het gebied van optische oplossingen voor precision manufacturing te verkennen. De Innovation Summit belooft een dynamische dag te worden vol kennisdeling en netwerken. Deelnemers komen in contact met de experts van Edmund Optics en met vooraanstaande gastsprekers van Teledyne Lumenara en Admesy.

De agenda staat vol met inzichtelijke presentaties over een breed scala aan onderwerpen, zoals ontwikkelingen op het gebied van machine vision, ultrafast en nanosecond lasers, laser beam shaping, de fijne kneepjes op het gebied van numerieke aperture, inzicht in de belangrijkste prestatiespecificaties en tot slot metrologie voor optische filters. Er is ook een interactieve labdemonstratie en we sluiten af met een paneel discussie.

Het evenement is gratis en weerspiegelt de toewijding van Edmund Optics aan het stimuleren van ideeënuitwisseling en innovatie in de industrie.

Edmund Optics nodigt professionals uit de optica- en fotonica-gemeenschap evenals geïnteresseerden in precision manufacturing, uit om deel te nemen aan dit bijzondere evenement.

Ga voor meer informatie en om te registreren voor de Innovation Summit naar European Innovation Summit juni 2024 | Edmund Optics.

Based on the high demand in the field of life sciences, semiconductor industry, as well as factory automation, the summit aims to bring together industry experts, innovators, and thought leaders to explore the latest advancements in optical solutions for precision manufacturing. The Innovation Summit, promises to be a dynamic day full of knowledge sharing and networking. Attendees will engage with Edmund Optics’ experts, as well as distinguished guest speakers from Teledyne Lumenara and Admesy.

The agenda is packed with insightful presentations, covering a wide range of topics, such as machine vision advancements, ultrafast and nanosecond lasers, laser beam shaping, numerical aperture intricacies, as well as insights into key performance specifications and metrology for optical filters. There will also be an interactive lab demonstration and a panel discussion.

The event is free of charge, reflecting Edmund Optics’ commitment to fostering idea exchange and innovation in the industry.

Edmund Optics invites professionals from the optics and photonics community, as well as those interested in precision manufacturing, to join this groundbreaking event.

For more information and to register for the Innovation Summit, please visit European Innovation Summit June 2024 | Edmund Optics.

« La demande dans le domaine de la technologie optique nous oblige à investir dans nos activités et à les élargir », déclare Samuel Sadoulet, directeur général d’Edmund Optics. « Comme Edmund Optics continue d’évoluer en réponse à un environnement commercial dynamique, nos structures de gestion doivent s’adapter pour mieux servir nos clients. »

La nouvelle directrice financière, Linda Fonner, arrive chez Edmund Optics avec plus de 30 ans d’expérience en gestion globale dans des entreprises telles que Phillips & Cohen Associates, Atotech (une marque de MKS), Bristol-Myers Squibb, West Pharmaceutical et Vesuvius, une entreprise du groupe Cookson. Au cours de sa carrière, Linda Fonner a travaillé dans les régions Asie-Pacifique, Australie, Moyen-Orient, Europe et Amériques.

Elle a dirigé des transformations financières et opérationnelles dans les secteurs de la fabrication de produits chimiques, de la distribution pharmaceutique, de la fabrication d’appareils médicaux et du moulage de céramiques à haute température pour les industries de l’acier, de la fonderie et du verre. Elle est spécialisée dans la mise en place de stratégies de collaboration, la planification à long terme, les fusions et acquisitions, les opérations financières mondiales et la mise en œuvre de systèmes. Les compétences de Linda Fonner en matière de leadership international s’appuient sur un large éventail de fonctions dans les domaines de la finance, des opérations, de l’informatique et des comptes de résultats pour des entreprises d’une taille allant de 50 millions de dollars à Fortune 500. Elle a acquis de l’expérience en matière d’acquisition, de cession et d’intégration d’entreprises et a su naviguer avec succès dans des environnements réglementaires mondiaux complexes.

« Je suis ravie de rejoindre un leader dans le domaine de la technologie optique et de travailler avec l’équipe de direction pour faire évoluer l’organisation en pleine croissance afin de répondre aux demandes complexes de nos clients », déclare Linda.

“The demand for optical technology requires us to invest in, and scale, our operations,” says Samuel Sadoulet, Chief Executive Officer of Edmund Optics. “As Edmund Optics continues to evolve in response to a dynamic business environment, our management structures must adapt to better serve our customers.”

New CFO, Linda Fonner, comes to Edmund Optics with more than 30 years of global management experience at companies such as Phillips & Cohen Associates, Atotech (an MKS Brand), Bristol-Myers Squibb, West Pharmaceutical, and Vesuvius, a Cookson Group Company. In her career Fonner has worked in the Asia-Pacific, Australia, the Middle East, Europe, and the Americas regions.

She has led financial and operational transformations in chemical manufacturing, pharmaceutical distribution, medical device manufacturing, and high-temperature ceramic castings for the steel, foundry, and glass industries. She has expertise in setting collaborative strategy, long-term planning, mergers and acquisitions (M&A), global financial operations, and system implementations. Linda’s international leadership skills are based broadly across finance, operations, IT, and P&L roles for companies ranging in size from $50M through Fortune 500. She has experience acquiring, divesting, and integrating companies and has successfully navigated complex global regulatory environments.

“I am delighted to join a leader in the optical technology space and work with the management team to evolve the fastgrowing organization in order to meet the complex demands of our customers,” says Linda.

« Nous sommes ravis d’améliorer considérablement nos capacités de fabrication d’optiques laser grâce à cette nouvelle installation en Floride », déclare Marisa Edmund, présidente du conseil d’administration et directrice générale du marketing et des ventes d’Edmund Optics. « Avec plus de 30 ans de présence régionale et une expertise mondiale en matière de conception, de fabrication et d’applications, nous sommes bien équipés pour répondre à la demande des clients en matière d’optiques laser de plus en plus performantes. »

En outre, ce site élargit les capacités de fabrication d’optiques laser d’Edmund Optics dans les domaines de la fabrication de cristaux laser et de verre, du polissage, de la métrologie, de l’inspection et des essais, et accueille environ 50 employés, dont beaucoup sont des experts en optique laser. Nos ingénieurs de conception et de fabrication sont spécialisés dans les traitements complexes à seuil de dommage laser élevé et dans la conception optimisée pour la fabrication.

« Nous attachons une importance primordiale à nos clients, ce que nous faisons chaque jour en fabriquant de manière fiable des optiques laser qui répondent à leurs spécifications et à leurs besoins individuels », a déclaré Stefaan Vandendriessche, directeur de la division optique laser d’Edmund Optics. « Cette nouvelle installation nous permet de mieux soutenir les applications innovantes grâce à l’extension de nos capacités de développement, de fabrication et d’assemblage. »

Pour en savoir plus sur les capacités, la métrologie, les processus, l’expertise et les ressources d’Edmund Optics en matière d’optique laser, veuillez visiter le nouveau site web www.edmundoptics.fr/lo.

“We are excited to significantly enhance our laser optics manufacturing capabilities and capacity with the new Florida facility,” says Marisa Edmund, Chairman and Chief Marketing & Sales Officer for Edmund Optics. “With over 30+ years of regional presence and global design, manufacturing, and applications expertise, we are well-equipped to respond to customer demand for increasingly high-quality laser optics.”

In addition, this facility expands Edmund Optics’ laser optics manufacturing capabilities across laser crystal and glass fabrication, polishing, metrology, inspection, and testing, and is home to approximately 50 employees, many of whom are laser optics experts. Our design and manufacturing engineers specialize in complex, high laser damage threshold coatings and designing for manufacturability.

“We continuously put our customers first, doing this every day by reliably manufacturing laser optics that meet their unique specifications and needs,” says Dr. Stefaan Vandendriessche, Director, Laser Optics Business Line for Edmund Optics. “This new facility enables us to better support innovative applications through our expanded development, manufacturing, and assembly capabilities.”

To learn more about Edmund Optics’ laser optics capabilities, metrology, process, expertise, and resources, please visit the new stand-alone website at www.edmundoptics.eu/lo.