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  | Frequently asked questions about... |
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| How can I model your aspheric lenses in my lens design software? |
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To model our aspheric lenses in lens design software, you are going to need the aspheric coefficients to create the surface(s). The coefficients are downloadable from the links below. Please note that all aspheric coefficients are for reference only, and should not be used as specifications.
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| What kind of polarization effects can be expected from the pellicle beamsplitters? |
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The pellicle beamsplitters will generally reflect 5 to 20% more S polarized light than P polarized light, depending on the coating and wavelength. For a more specific performance estimate, please contact one of our Applications Engineers.
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| What is the index/transmission of a certain optical material at a certain wavelength? |
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Typical index and transmission values for our optical materials can be found in the Optical Materials section of our catalog and website. Each material has performance data for a range of wavelengths. |
| I want to purchase one of your optical products, but the coating I want is not listed on the website as available for that product. Can I still get the coating I want? |
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Most of the time, yes. The optic & coating combinations shown on the Buy-Online section are our most popular ones, and are the most likely to be readily available. Our full selection of antireflection and high-reflection coatings can be applied to our line of optics for an additional fee. For coating recommendations, availability, and pricing please contact one of our Applications Engineers.
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| What is the damage threshold for your anti-reflective and mirror coatings? |
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Melles Griot has tested the majority of our coatings for their damage threshold specifications. We understand that it is important to our customers to know what this limit is in order to preserve the integrity of their optical systems. The link below will open the appropriate Optical Coatings section of our catalog. Below each coating, there is a typical damage threshold listed. When coatings are very similar in composition, there may be a reference to another coating for its damage threshold. Please note that all the values given are for reference only and do not imply a guarantee. There are many different applications for the coatings, so we tried to test them with a common laser for the specified range of the coating. They were typically tested using a pulsed 1064 nm laser and its harmonics. Unfortunately, we could not possibly test them for all different configurations, including continuous (CW) lasers. There are simply too many parameters that affect the damage threshold of a coating. Therefore, we do not have any other data than what is specified in the catalog and there is not a simple formula to determine how a different wavelength might respond. |
| Can Melles Griot modify standard optics to custom sizes? |
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Our optics manufacturing facility in Rochester, NY can offer this service to our commercial and OEM based customers. Our ability to modify includes edging diameters down and cutting to square or rectangular shapes. This includes lenses (both spherical and cylindrical), mirrors, and filters (excluding the interference filters). There are a few rules of thumb to follow when modifying standard pieces: The standard tolerance for modifications is ±0.25 mm (±0.01"). If a customer needs a tighter tolerance, it must be specified. A standard lens can be edged down to a diameter that is no less than twice the center thickness of the lens. For example, we smallest we could edge a 01 LPX 084 (beginning diameter: 30 mm, center thickness: 8.4 mm) down to would be 17 mm. A lens that is larger than 97 mm in diameter cannot be edged down. A mirror can be modified, but the flatness cannot be maintained to the original specification because stress is induced when a piece is modified. |
| What is the difference between the Glan-Taylor and the Glan Thompson Polarizing Prisms? |
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Both of these products take un-polarized input and convert it to linearly polarized output. The main difference is the Taylor is air spaced and the Thompson is cemented. The advantage of the cemented prism (Glan-Thompson) is that it has a greater field of view (as great as 24 degrees depending on length). The air spaced prism (Glan-Taylor) only has around a 10 degree field of view. The advantage of the air spaced is that it has a higher transmission than the cemented Glan-Taylor. |
| I was looking through your concave reflectors and your spherical mirrors but couldn't find the correct radius of curvature that I need. Do you make custom reflectors? |
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Our facility in Rochester, NY can offer custom reflectors to our commercial and OEM based customers, but there is another option that you can consider. We can put a reflective coating on one of our plano-concave (or plano-convex) lenses. Our newest catalog contains the radii of curvature for our lenses. The full catalog in PDF form is available under "Catalog downloads about" in the downloads section of our website. For further assistance, please contact one of our Applications Engineers. |
| Do you coat Customer Furnished Materials? |
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We have recently announced a new service to coat Customer Furnished Materials. Please see the link below for our press release. Any further questions should be directed to the contact information at the bottom of the press release.
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| Can the Collimating and Focusing Lenses be used in conjunction with either the Focusing Beam Expanders or Mounted Anamorphic Prisms? |
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In our Diode Laser Optics section of the catalog there are several products that can be used in conjunction with each other to meet the needs of a wide variety of applications. The Collimating and Focusing Lenses (06 GLC 001-005), Mounted Anamorphic Prisms (06 GPA's), and Focusing Beam Expanders (06 GBF's) are all compatible with each other. The links below are for the three items discussed above. There are four different combinations depending on your individual needs. They are:
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| The calibration date on my filter's spectral curve sheet expired. Do I need to recalibrate the filter? |
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No, the calibration date listed on the filter spectral curve sheets are the next calibration due date for the spectrometer on which the curve was measured. It has no effect on the filter's performance. |
| What is the difference between S- and P-polarization? |
S-polarization (the s stems from the German word senkrecht meaning perpendicular) and P-polarization (the p means parallel) are the two main ways to describe two types of linearly polarized light. A primary misconception when using the terms is assuming that P is always vertical and S is always horizontal. This is not true. P and S are relative to a surface (usually the surface that the light is acting upon and/or reflecting from). To properly define S- and P- polarizations, we first need to define the term plane of incidence. The plane of incidence is the plane that the incident and exiting beams lie in and is perpendicular to the surface that the light is incident upon. P-polarization refers to light that is polarized parallel to the plane of incidence. S-polarization refers to light that is polarized perpendicularly to the plane of incidence. So saying that P-polarization is always up-down and S is always side-to-side is incorrect. One example where this is incorrect is with a common beamsplitter setup. In a beamsplitter being used where the entrance and exit beams are all parallel to the table top, P will parallel to the table (side-to-side) and S will be perpendicular to the table (up-down). The best thing is to keep in mind that S and P are relative to the plane of incidence. |
| What is the optical difference between BK 7 and fused silica? |
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BK7 glass is one of the most common and widely used borosilicate crown glasses available. It performs well against most chemical tests, it is relatively hard, and does not scratch easily. BK7 glass can be handled without the need for special precautions. The bubble and inclusion content is also very low. BK7 has excellent transmission from 350nm to 1.5 µm. It can be a low-cost alternative to fused silica. Fused silica is another common material used for optics. It has greater transmission than BK7 in the UV and IR spectrum. Transmission ranges from 180nm to 2 µm. Fused silica has a low coefficient of thermal expansion, providing stability and resistance to thermal shock over large temperature deviations. Fused silica has increased hardness and resistance to scratching. It can be an excellent alternative to BK7 glass, depending on the application. |
| What types of lenses are best suited to collimate and focus a diode laser? |
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Melles Griot offers collimating and focusing lenses designed specifically for diode laser wavelengths. The 06 GLC series lenses are designed and optimized for 405 nm, 633 nm, 780 nm, and 830 nm. They can also be used at other diode laser wavelengths and still provide excellent performance. Many of these lenses are diffraction limited: Spherical aberration, coma, astigmatism, and sphero-chromatism have been corrected by the design. These lenses are antireflection coated to provide increased performance.
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| What are Diffractive Optical Elements (DOE's) and what are some of the advantages of using them in a lens design? |
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Diffractive Optical Elements (DOE's) can focus light just like conventional refractive elements but do so by diffraction (similar to a grating) instead of by refraction. Compared with conventional optical surfaces, which are flat or spherical in shape, DOE's can be constructed to simulate complex surface shapes to better correct aberrations and improve optical performance. Just like glass optics, DOE's can be antireflection coated with single or multilayer coatings. DOE's are useful for conventional broadband imaging applications as well as for many low- and high- power laser applications. Typical DOE sizes range from approximately 4 mm to 250 mm in diameter. For OEM applications, the principal advantages of using DOE's include: DOE's usually permit a reduction in the number of optical elements in a design, reducing costs and lens weight. DOE's often enable optical performance that would be impossible to achieve using conventional optical elements alone. |
