A combination optical filter, also known as a laminated optical filter, is an optical filter component where two or more optical elements of different functions are laminated together with optical adhesive to achieve specific spectral-selection performance. Elements for combination include colored glass, coated filters, anti-reflection (AR) lenses, polarizers and so on.
What is main working principle of combination optical filters?
Combination optical filters operate based on the selective absorption or reflection of light. They are constructed from colored glass, coated filter or polarizer of different materials that absorb light in designated wavelength bands.By combination, colored glass can be combined with coated optical filters to achieve deep blocking and precise control over transmitted spectral bands. Shortpass filters and longpass filters can also be laminated together, and their overlapping region forms the transmission passband.
In short, it acts like a subtractive system that achieves optical filtering by absorbing or reflecting unwanted light layer by layer. Combination optical filters are generally fabricated from existing filter components to meet specific filtering requirements. They can be bandpass filters, longpass filters, polarizers and more.
What are the common types of combination optical filters?
Based on the lens type and structure of laminated optical filters, the common types and examples are as follows:
- Combination absorptive and coated bandpass filter: One of the most typical laminated optical filters. It is laminated with one piece of shortpass filter or IR-cut colored glass and two bandpass filter elements. Only light within the specified passband can transmit. Meanwhile, the selective absorption characteristic of colored glass enhances blocking performance in the stop-band.
Product examples we have ever manufactured:
- Combination coated bandpass filter: For cost-saving in mass coating under moderate spectral accuracy requirements, selected shortpass and longpass coated filters are Laminated to deliver basic bandpass performance. Unlike absorptive laminated bandpass filters, stop-band suppression is achieved by reflection from cut-on or cut-off filter layers.
- Combination absorptive bandpass filter: Similar to laminated coated bandpass filters, it is made by laminated selected shortpass and longpass colored glasses, such as orange glass and blue glass, to achieve the designed basic bandpass filtering function. The bandpass effect is realized through the cut-off and cut-on functions of blocking filters, and stop-band attenuation is achieved via selective absorption.
- Combination polarizer filter: A polarizer is hermetically bonded between two glass substrates with optical adhesive. This protects the thin, easily deformable polarizing film and improves its environmental stability and durability.
Product examples we have manufactured:
- Multi-band spliced assembly: Filter chips of different wavelength bands are cut, spliced and laminated onto a single substrate. This type of laminated filter enables one assembly to process optical signals of multiple wavelength bands simultaneously.
In simple terms, it achieves optical filtering by absorbing unwanted light layer by layer. The above only lists some common types of laminated optical filters. Please contact our sales engineers for further information if you have other requirements for laminated filters.
What are the main application scenarios of Combination optical filters?
Laminated optical filters are widely used in applications that require cost-effectiveness and stability, with relatively loose spectral precision requirements:
- Fluorescence detection and analysis: Used in biomedical instruments such as immunoassay analyzers to accurately extract fluorescence signals while blocking excitation light.
- Laser and optical systems: Applied in dual-path laser and low-light optical systems to separate or combine light beams of different wavelengths.