Cut‑off glass filter

Cut‑off glass filter is a type of glass with special optical properties, selectively transmitting or blocking light within a specific wavelength range. The following is a detailed introduction to cut-off glass:

Definition and Principle
Cut‑off glass filter is a selectively transmissive colored optical glass that strongly absorbs short-wavelength light, such as ultraviolet, blue, and green light, while efficiently transmitting long-wavelength light, such as yellow, orange, red, and near-infrared light. Its "cut-off" characteristic refers to the drastic attenuation of light below a specific wavelength, forming a spectral response curve similar to a "switch." This is mainly achieved by doping the glass substrate with specific metal oxide colorants, such as iron, chromium, nickel, and titanium, to alter the glass's absorption characteristics for different wavelengths of light.

Main Types

Ultraviolet Cut‑off glass filter: The cut-off wavelength of ultraviolet cut-off glass is typically adjustable between 350-500 nm, with a visible light transmittance greater than 80%. It can achieve the purpose of blocking ultraviolet light through doping in the glass body or coating the glass surface.

Visible light Cut‑off glass filter: Such as cutoff-type golden yellow optical glass, the cutoff wavelength is typically in the range of 480-550nm, with a high-transmittance region above 520nm, and an appearance of transparent golden yellow or amber.

Technical parameters: The technical parameters of different types of cutoff glass vary, but generally include the following: refractive index is typically 1.52-1.54; Abbe number is 55-60; density is 2.4-2.6g/cm³; coefficient of thermal expansion is 70-90×10⁻⁷/K; temperature resistance range is generally -40°C to +500°C (short-term); surface quality can reach 60/40 or higher (MIL-C-48497 standard); thickness is selectable from 0.5mm to 10mm, and the thicker the glass, the steeper the cutoff slope and the stronger the low-wavelength blocking.

Application Areas

Optical Instruments and Scientific Equipment: Used in fluorescence microscopes, spectrophotometers, spectrometers, laser systems, etc., as filters or protective windows to improve instrument performance and stability.

Lighting and Display Technology: Applied in projectors, stage lighting, plant growth lights, eye-protection desk lamps, etc., enabling adjustment of spectral output to achieve specific lighting effects or protective functions.

Medical and Health Equipment: Such as dental light curing devices, phototherapy equipment, beauty instruments, etc., cut-off glass can be used for filtering or protection, ensuring the safety and effectiveness of treatment processes.

Photography and Visual Arts: Can be used as film filters, astrophotography filters, etc., to create specific visual styles or reduce light pollution interference.

Automotive and Traffic Engineering: Used in vehicle lighting and signaling systems, cockpit instrument lighting, etc., ensuring that the color and intensity of the light meet relevant regulations and requirements, while improving driving safety and comfort.