What are conversion filters?
Conversion filters are optical filters that specifically alter the spectral composition of light, thereby adjusting the color temperature. Unlike traditional color filters, they do not strongly absorb light but rather shift the spectrum, enabling uniform, low-loss transmission.
They are used to correct color temperatures, compensate for color deviations, and create specific desired lighting moods.
Difference from color filters
Traditional color filters selectively absorb specific wavelengths, thereby reducing the light. Conversion filters, on the other hand, shift or convert wavelengths and utilize the existing spectrum more efficiently.
As a result, they have lower light loss, are more flexible, and allow for more precise adjustment of light characteristics.
Thin-Film Coatings for Conversion Filters
Optical thin films provide precise spectral control in conversion filters. As bandpass, long-pass, or short-pass filters, as well as dichroic (interference) filters, they precisely separate and direct wavelengths.
In the process, unwanted spectral components are selectively blocked or redirected, while the desired light is amplified. This ensures efficient and precise color control, particularly in LED systems.
Structure of thin-film conversion filters
Thin-film conversion filters consist of precisely tuned multilayer systems with alternating high and low refractive indices (e.g., TiO₂/SiO₂). The layer thicknesses are within the range of a few wavelength components, enabling sharp spectral transitions and freely definable filter properties.
Advantages of thin-film conversion filters (spectral properties)
Thin-film conversion filters offer maximum precision in light control. They achieve high transmittance, sharp spectral edges, and freely definable wavelength ranges. Low absorption also results in minimal heat generation. Compared to traditional, absorptive filters, they offer higher efficiency and minimal losses. In combination with dichroic coatings, they also enable the targeted use of reflection and transmission. Thus, the filters are ideal for optimizing modern conversion systems.
Applications of Conversion Filters: Process Control via Light
Light-Induced Processes (Chemistry and Biology)
Specific wavelengths of light can be used to specifically trigger or control chemical or biological reactions. Conversion filters help tailor the light spectrum precisely to these processes.
Chemistry
- Photocatalysis: Light activates catalysts and accelerates chemical reactions
- Photopolymerization: Curing of coatings or plastics using UV light/visible light
- Photooxidation: Light specifically initiates oxidation processes
Biology
- Photosynthesis: Plants use specific wavelengths (primarily blue/red) for growth
- Phototherapy: Light influences biological processes in medicine (e.g., skin treatment)Conversion filters allow for precise adjustment of light color and spectrum. Learn more about how they work, the benefits of thin-film technology, and their applications.
- Fluorescence and imaging: Excitation of biomarkers for diagnostics and microscopy
Einsatzbereiche von Konversionsfiltern
| Field of Application | Typical Applications / Benefits |
| LED and Lighting Technology | White light generation, color temperature adjustment (warm white, neutral white, daylight), color correction, improved color rendering, spectral stability, glare and thermal management, targeted lighting |
| Displays and Micro‑LED | RGB conversion (e.g., blue to RGB), high color gamut coverage |
| Sensors, Optics | Spectral adjustment in measuring instruments, microscopy, and camera systems |
| Automotive /Headlights | Precise color control, adaptive lighting systems |
| Product presentation | Optimized lighting for products (e.g., food, textiles) |
| Other applications | Architectural lighting, stage lighting, medical and analytical instruments, plant lighting |
