FAQ - Enhanced Aluminium Front Surface Mirrors
Frequently asked questions about our SEA-VIS and SEA-NIR mirrors
View the datasheet of our enhanced aluminum mirrors
Here you 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 are 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 shape is more economical, round, or rectangle?
• 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 you also coat other glass substrate materials 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 I use the mirrors 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 coated on the top side of the bare aluminum layer. This additional coating system offers a considerable increase in visible reflection compared to bare-aluminum mirrors. Other advantages of this only some nanometers thick overcoating are protecting 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 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 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 no special processing or very tight tolerances required. We can even offer our 48-Hour Express Optics Service for individually sized square and round custom optics in many cases.
Q: Do the mirrors cause ghost imaging in the optical path?
A: No! All mirrors we make are technical front surface coated mirrors, or first surface mirrors, as we also call them. The reflecting surface is on the front side of a plane glass substrate. 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 a backside coated mirror's top glass surface do not exist when you use our high-quality front surface mirror series.
Q: What mirror shape is more economical, round, or rectangle?
A: Generally said, rectangle shapes are more economical than round parts, especially in small quantities. This cost difference gets significantly more modest at large production quantities, but its cost never meets on the same level. Of course, this depends on the details, but a rectangle part with moderate tolerances compared to a round mirror with identical tolerances is typically more economical.
Q: Why is the color of the mirror surface blue?
A: If the optically active surface color is blue, you likely forgot to remove the protective tape from the mirror surface. This tape is protecting the mirror surface during manufacturing, transport, and mounting. It necessarily must be removed before you use the mirror. However, not all mirrors have this protective tape. Depending on how they are processed, some mirrors don't have protective tape on the coating.
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 an increased or defined optical flatness requirement, the mirrors must 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 if you need a defined flatness and inform us about all the relevant details.
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 this is a minimum specification. Most of the time, the surface quality is very much better than this minimum specification. In case you have a particular or defined surface quality requirement, the mirrors need to be custom manufactured according to your needs. This custom manufacturing is done by special handling procedures and polishing the glass substrates to a defined surface quality. After that, we optically coat the mirrors are in a separate coating run. Please send us your inquiry if you need a defined surface quality and contact us with all the relevant details.
Q: Are the SEA-Mirrors made of solid aluminum?
A: No. Our SEA-mirror series are based on glass substrates and coated with aluminum plus a dielectric thin film coating. We do not manufacture solid aluminum mirrors.
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, compared to front surface mirrors without protection, thanks to the dielectric multilayer-overcoating, both SEA-VIS and SEA-NIR mirror series offer relatively high scratch resistance. Nevertheless, as it applies to all surface coated optics, the surfaces must be handled with care to prevent scratching or other damages to the optical surface.
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 must pass through a glass substrate to reach the reflective coating. After the mirror coating has reflected the image, it again has to pass through the glass. So, the image has to go through the mirror's substrate glass twice before it is reflected. Uncoated glass surfaces show a typical reflection of about 4-5% in the visible, which produces the secondary images (ghost images) that overlay with the image reflected by the coating, resulting in a blurry image. Besides, rear surface coated mirrors usually have a significantly lower reflection and poor optical quality. On the other hand, a front surface mirror has its optically active coating directly on top of a glass substrate. The image does not have to travel through the glass to reflect. Instead, it reflects directly, which ultimately prevents any secondary reflections and ghost images. Therefore, the optical imaging quality of front surface coated mirrors is substantially better than the one achieved with backside coated mirrors.
Q: Can also other glass substrate materials be coated with the SEA mirror coatings?
A: Yes, this is possible per coating batch. The required quantity must be large enough for at least one coating run because this is the smallest production quantity possible. Therefore, small amounts of parts based on custom coatings cannot be produced at a reasonable cost.
Q: Do you coat metals or plastics with the SEA mirror coatings?
A: No. We solely coat mirror coatings on glass substrates.
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 optical coatings are done on a per batch, this is just a reasonable option if the quantity is large enough for at least one coating run.
Q: Can the mirrors also be used as a backside coated mirror?
A: Yes, this absolutely can work. However, the mirror shows a lower reflection if used from the backside, and most of the technical disadvantages of backside coated mirrors like ghost imaging and blurry effects occur. Please note that the mirror coating is located on the unprotected backside when you use it as a backside coated mirror.
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 are 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 because the undefined areas are no process-controlled wavelength ranges and can differ from batch to batch.
Q: What are the reflection characteristics of the mirrors for polarized light?
A: Unless otherwise specified, all specifications are for unpolarized light. We also do not provide any information on a possible change of the polarization plane. In many cases and large quantities, a specially designed mirror coating defined for polarized light is possible on a per coating batch basis.
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.
Q: How heat resistant are the mirrors?
A: We designed the SEA-front surface mirror series 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. We recommend using a different glass substrate and an all-dielectric thin film coating construction for higher operating temperatures.
Q: Do you offer an Express Service for custom-sized front surface mirrors?
A: Yes, we do. We offer our 48h-Express Service (shipping within two working days) for most of our standard coatings and standard glass materials for an extra charge. Whether our Express Service is possible depends on your parts' complexity, the tolerances, the required quantities, current production load, and the necessary setups needed to make your parts. In urgent cases, please send us an inquiry using our inquiry form. We immediately check whether our Express Service is possible for the product you require.