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The most frequently asked questions from our customers.

For any questions not answered here, please do not hesitate to contact us by phone or email.

Are the dip-coated filters suitable for imaging applications?

As a rule no, because the double-sided interference layer might cause ghosting. Generally, heat-reflective filters, cold light mirrors, conversion filters and color-effect filters are used for illumination.

How durable are the dip-coated filters?

Dip-coated filters have an inorganic hard coating applied at a temperature of 480°C. Accordingly, they can be used at temperatures up to 450°C for short periods of time (taking into account the temperature limits of the substrate) and are UV resistant.
They can also resist water, weak acids and alkalines, alcohol and glass cleaners. Due to the relatively small thickness of the coatings (100nm to 1µm) care should be taken when cleaning the filters.

How do interference coatings work?

The coating is composed of different materials (e.g. silicon dioxide, titanium dioxide) whose combination precisely determines the amount of light passing through the filter.

Which wavelengths can be used with the dip-coated filters?

In principle, dip-coated filters are suitable for the 200-1700nm range. Most filters work in the visible range (380-780nm). However, special filters are available for the UV range (200-380nm) and for the near IR range (780-1700nm). The amount of absorption in the UV range is influenced through the selection of the coating material.

Can interference filters be combined?

Yes, due to the generally very low levels of absorption, interference filters can be combined without difficulty. For example, filter colors may be combined in order to achieve a different color or a non-reflecting protective glass can be used with a heat-reflecting IR filter.

What differentiates dip-coated filters from vacuum-coated filters?

Dip-coating is just one of the many possibilities available for bringing a thin dielectric layer on glass; the functionality is identical to vacuum-coated filters and it is easier to coat larger areas (typically 1080x800mm). However, the dip-coating process is limited to about 20 layers, which obviously restricts the optical specification. Therefore, it is not possible to produce band pass filters because they require somewhat more than 20 layers. Dip-coated filters are normally identically coated on both sides of the glass. However, it is possible to apply different coatings on the same substrate using a special manufacturing process (e.g. masking or etching).