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FAQ - Enhanced Aluminium Front Surface Mirrors

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

View the data-sheet of our enhanced aluminum 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 here, please feel free to contact us with your question. We will be pleased to share all available information with you.

 

What advantage do the dielectric overcoatings offer?

Are there any standard dimensions?

Do the mirrors cause ghost images in the optical path?

What is more economical, 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 as 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.
Also, please consider our "Notes on technical specifications".














































































































 

Q: What advantage do the dielectric overcoatings offer?

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

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Q: Are there any standard dimensions?

A: No, but this is a feature, not a disadvantage: 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 beneficial if the customer can procure the exactly matching mirror size. In case you need an individually sized part please choose the coating of interest in our RFQ form and select the desired glass thickness (SEA-VIS: 0,55, 1,00, 2,00, 3,00, 4,00, 5,00 & 6,00 mm / SEA-NIR: 2,00 & 3,00 mm). Then enter the desired part dimensions and, if required, choose a dimension tolerance and finally enter the required quantity. Usually, you will receive your quotation the same working day we receive your inquiry. The typical delivery time for parts manufactured to custom-size at average production load is only 1-2 working weeks even for several hundred to thousands of pieces, provided that there are no special processing or very tight tolerances are required. In many cases, we can even offer our 48-Hour Express Optics 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 which means that in contrary to usual 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 the secondary reflection of the top glass surface of a backside coated mirror do not exist when you use our high-quality front surface mirror series.


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Q: What is more economical, 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 huge production quantities this cost difference gets significantly more modest but it cost will never meet on the same level. Of course, this depends on the details but a rectangle part with moderate tolerances compared to a round mirror with the 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, transport, and mounting. It necessarily must be removed before the mirror can be used. Please also consider that some mirrors depending on how they are processed don't have this protective tape on the coating 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, the planarity is sufficient for most technical-optical applications. In case you have a increased or defined optical flatness requirement the mirrors will have to be custom manufactured according to your needs. In such cases, the substrates are first brought to size and then polished to a defined flatness. The finished substrates are then 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 very much better than this minimum specification. In case you have a particular or defined surface quality requirement the mirrors will have to be custom manufactured according to your needs. This custom manufacturing is done by special handling procedures and by polishing the glass substrates to defined surface quality. They 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 aluminum plus a dielectric thin film coating. We do not manufacture solid aluminum mirrors.


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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, when compared to front surface mirrors without protection, thanks to the dielectric multilayer-overcoating, both of the SEA-VIS and SEA-NIR mirror series offer a relatively high scratch resistance. Nevertheless, as it applies for all surface coated optics, 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 backside coated mirrors, which means that the image or light beam to be reflected first has to pass through a glass substrate to reach the reflective coating. After the coating layers have reflected the picture, 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 interfering secondary reflection caused by the first glass surface reflection. Because uncoated glass surfaces show a typical reflectivity of about 4-5% in the visible, this produces a secondary image (ghost image) that overlays with the image reflected by the coating resulting in a blurry image. Also, rear surface coated mirrors usually have a significantly lower reflection and a bad optical quality. In contrary to that the optically active coating of a front surface mirror is located on the first surface the glass substrate and only the first surface is reflecting the image which completely prevents any secondary reflections and therefore any ghost images. The optical imaging quality of surface coated mirrors, therefore, 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 per coating batch. This means the required quantity must be large enough for at least one coating run because this is the smallest production quantity possible. Small production quantities based on custom coatings, therefore, cannot be produced at a reasonable cost.


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

A: No. We solely 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! However, the prerequisite is that the supplied substrates are still uncoated, made of glass, and are technically suitable to be coated. Because an optical coating can only be done on a per coating batch basis, this is just a reasonable option if the quantity is large enough for at least one coating run.


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

A: Yes this absolutely can work. However, the mirror will show a lower reflection if used from the backside and most of the technical disadvantages of backside coated mirrors like 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 backside coated 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 without obligation. But please consider that this kind of information is not guaranteed at all because the undefined ranges are no process controlled wavelength ranges and can differ 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. We also do not provide any information on a possible change of the polarization plane. In many cases and at quantities large enough a specially designed mirror coating that is defined for polarized light is possible on a per coating batch 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 cleaning 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 maximum possible operating temperature depends on the thin film coating design and the glass substrate used. SEA-VIS front surface mirrors based on a selected float glass substrate, for example, can be used up to approximately 120 °C, provided there are no large temperature gradients and 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 we do. For an extra charge, we offer our 48h-Express Service (shipping within two 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 needed setups that are necessary 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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