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FAQ - Enhanced Aluminium Front Surface Mirrors

Frequently asked questions of our SEA-VIS and SEA-NIR mirrors

Data-sheet of our Enhanced Aluminium Front Surface Mirrors


Here you will find our FAQ in regards to our SEA-VIS and SEA-NIR front surface mirrors.
If you can't find an answer to a question you might have, please feel free to contact us with your question. We will be pleased to share all available information with you.

What are the dielectric overcoatings for?

Are there any standard dimensions?

Do the mirrors cause ghost imaging in the optical path?

What is more economical, a round or rectangle mirror shape?

Why is the color of the mirror surface blue?

What is the flatness of the SEA-VIS and SEA-NIR front surface mirrors?

What is the surface quality of the SEA-VIS and SEA-NIR mirrors?

Are the SEA-Mirrors made of solid aluminum?

How scratch resistant are the SEA-VIS / SEA-NIR first surface mirrors?

What is the difference between a front surface mirror and a "normal" mirror?

Can also other glass substrate materials be coated with the SEA mirror coatings?

Do you coat metals or plastics with the SEA mirror coatings?

Do you also coat customer supplied material with the SEA mirror coatings?

Can the mirrors also be used like a backside coated mirror?

How is the reflection of the mirror coatings above and below the specified ranges?

What are the reflection characteristics of the mirrors for polarized light?

What cleaning procedure should I use to clean the mirror coating?

How heat resistant are the mirrors?

Do you offer an Express Service for custom sized front surface mirrors?



All given details and specifications are mean reference values and are not guaranteed.
In addition, please consider our "Notes on technical specifications"














































































































 

Q: What are the dielectric overcoatings for?

A: The overcoatings of our SEA-VIS and SEA-NIR Enhanced Aluminium front surface mirror series are consisting of a very thin dielectric multilayer thin film coating system which is coated on top of the bare aluminium layer. This additional coating system features a considerable increase of visible reflection compared to bare aluminum mirrors. Other advantages of great importance of this only some nanometer thick overcoating are the protection from environmental influences and an increased scratch resistance of the first surface mirror coating.

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Q: Are there any standard dimensions?

A: No, but this is an advantage. It is of great value for our customers, that we are not limited to a few standard sizes as this is common for trading companies or companies who only resell catalog items. Almost any application requires individual dimensions. Therefore in most instances it is very helpful if the exactly matching dimension can be procured. In case you need an individually sizes part, please choose the coating of interest in our RFQ form and let us know the substrate thickness (SEA-VIS typ. 0,55mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm / SEA-NIR typ. 2mm and 3mm). Then please enter individual part dimensions and, if required, choose a dimension tolerance and enter the required quantity. Usually you will receive your quotation the same working day we receive your inquiry. The typical lead time for individually manufactured parts at average production load is only 1-2 working weeks, even for several hundred pieces, provided that there are no special manufacturing setups or very tight tolerances required. In many cases, we can even offer our 48 Hour Express Service for individually sized square and round custom optics. (For details, please follow the link.)


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Q: Do the mirrors cause ghost imaging in the optical path?

A: No! All mirrors we make are technical front surface coated mirrors or as they are also called, first surface mirrors. The reflecting surface is located on the front side of a plane glass substrate. This means, that in contrary to normal backside coated mirrors, the reflected image or light beam does not have to pass through a glass twice to be reflected. Ghost images that occur due to secondary reflection of the top glass surface of a backside coated mirror do not exist when our high quality front surface mirror series are used.


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Q: What is more economical, a round or rectangle mirror shape?

A: Generally said, rectangle shapes are more economical to make than round parts, especially at small quantities. At large and very large quantities, this cost difference gets significantly smaller but will never be on the same level. Of course this depends on the details but a rectangle part with moderate tolerances compared to a round part with same tolerances will typically be more economical.


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Q: Why is the color of the mirror surface blue?

A: In case the color of the optically active surface is blue, it is likely that you have forgotten to remove the protective tape from the mirror surface. This tape is protecting the mirror surface during the manufacturing process, during transport and during the mounting process. The protective tape necessarily must be removed before the mirror can be used. Please consider, that some mirrors depending on how they are processed don't have this protective tape though.


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Q: What is the flatness of the SEA-VIS and SEA-NIR front surface mirrors?

A: We don't further specify the flatness of our standard mirror series. Nevertheless it is sufficient for most technical optical applications. In case you have a special or defined optical flatness requirement, the mirrors will have to be custom manufactured according to your requirements. This is done by polishing the glass substrates to a defined flatness which then can be optically coated in a separate coating run. Please send us your inquiry in case you need a defined flatness and let us know all relevant details.


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Q: What is the surface quality of the SEA-VIS and SEA-NIR mirrors?

A: The standard surface quality is 80-50 scratch & dig according to MIL-0-13830A (Cosmetic Surface Quality) and is a minimum specification. Most of the times the surface quality is even much better than this minimum specification. In case you have a special or defined surface quality requirement, the mirrors will have to be custom manufactured according to your requirements. This is done by special handling procedures and polishing the glass substrates to a defined surface quality which then can be optically coated in a separate coating run. Please send us your inquiry in case you need a defined surface quality and let us know all relevant details.


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Q: Are the SEA-Mirrors made of solid aluminum?

A: No. All of our SEA-mirror series are based on glass substrates and are coated with aluminium plus a dielectric thin film coating.


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Q: How scratch resistant are the SEA-VIS / SEA-NIR first surface mirrors?

A: We do not specify the scratch resistance of our SEA-VIS and our SEA-NIR mirrors separately. However, thanks to the dielectric multilayer overcoating, both of the SEA-VIS and SEA-NIR mirror series offer a relatively high scratch resistance when compared to other first surface mirrors. Nevertheless, as it applies for any other surface coated optic, the surfaces must be handled with care to prevent scratching or other damages of the optical surface.


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Q: What is the difference between a front surface mirror and a "normal" mirror?

A: "Normal" mirrors are so called rear surface mirrors or backside coated mirrors. This means, that the image or light beam to be reflected first has to pass through a glass to reach the reflective coating. After the image has been reflected by the coating, it again has to pass through the glass. So the image has to pass through the mirror's substrate glass twice to be reflected, resulting in a secondary reflection from the top glass surface. Because uncoated glass surfaces show a typical reflection of about 4-5% in the visible, this causes a secondary image (ghost image) that overlays with the image reflected by the coating which results in an blurry image. In addition, rear surface coated mirrors normally have a significantly lower reflection and a poor optical quality. In contrary to that, the optically active coating of a front surface mirror is located on top of the glass substrate and only the first surface is reflecting the image which prevents any secondary reflections and therefore any ghost images. The optical imaging quality of front surface mirrors is substantially better than the one that can be achieved from backside coated mirrors.


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Q: Can also other glass substrate materials be coated with the SEA mirror coatings?

A: Yes, this is possible on a per coating run basis. This means the required quantity must be large enough for at least one coating run because this is the smallest production batch possible. Very small quantities based on custom glass substrates therefore cannot be produced at reasonable pricing.


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Q: Do you coat metals or plastics with the SEA mirror coatings?

A: No. We only coat mirror coatings on glass substrates.


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Q: Do you also coat customer supplied material with the SEA mirror coatings?

A: Yes, provided that the supplied substrates are still uncoated, made of glass and technically suitable to be coated. Because an optical coating can only be deposited on a per coating run basis, this is only a reasonable option if the quantity is large enough.


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Q: Can the mirrors also be used like a backside coated mirror?

A: Yes this absolutely could work. However the mirror will show a lower reflection and most of the technical disadvantages of rear surface mirrors (ghost imaging etc) will be present. Please note that the mirror coating will be located on the unprotected backside when you use it as a rear surface mirror.


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Q: How is the reflection of the mirror coatings above and below the specified ranges?

A: This is generally completely unspecified, because the mirror coatings are optimized for the defined wavelength ranges only and they are solely controlled and tested to meet the defined specifications. Nevertheless, we will be pleased to let you know the typical characteristics outside the specified wavelength ranges. But please consider that this kind of information generally and absolutely is not guaranteed, because the undefined ranges are no process controlled parameters that might change from batch to batch.


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Q: What are the reflection characteristics of the mirrors for polarized light?

A: Unless otherwise specified, all specifications are given for unpolarized light. Also we don't make any calls on a possible change of the plane of polarization. In many cases, a specially designed mirror coating that is defined for polarized light is possible on a per coating run basis though.


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Q: What cleaning procedure should I use to clean the mirror coating?

A: Generally the same rules apply as for all other surface coated optics. Detailed directions are available on request.


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Q: How heat resistant are the mirrors?

A: All SEA front surface mirror series are designed for "normal" operating temperatures. The max. possible operating temperature depends on the thin film coating design and on the glass substrate used. SEA-VIS front surface mirrors based on a selected float glass substrate for example, can be used up to 120°C, provided there are no large temperature gradients and there is no thermal shock. For higher operating temperatures, it is recommended to use a different glass substrate and/or an all dielectric thin film coating construction.


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Q: Do you offer an Express Service for custom sized front surface mirrors?

A: Yes. For a premium charge, we offer our 48h-Express Service (shipping within 2 working days) for most of our standard coatings and standard glass materials. Whether our Express Service is possible, depends on the complexity of your parts, the tolerances, the required quantities, our current production load and on the necessary setups that are required to make your parts. In urgent cases, please send us an inquiry using our inquiry form. We will immediately check whether our Express Service is possible for the product you require.


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