Infrared Cut-off Filter (IR-CUT) is a critical optical component designed to selectively transmit visible light (typically 400-700nm) while blocking infrared light (wavelengths above 700nm). It is widely used in optical systems and electronic devices to enhance imaging quality and protect equipment safety. Typically fabricated from ultra-thin optical plastic film or optical glass substrates, this component employs multi-layer coating technology to achieve precise spectral control. With a thickness of only a few micrometers, it significantly optimizes optical signal transmission.

Core Functions of Infrared Cut-off Filters

• Enhancing Imaging Quality: In devices such as digital cameras and smartphone cameras, infrared light can cause color distortion (e.g., graying of green plants, fading of red tones). The filter blocks infrared interference while ensuring high transmission of visible light, resulting in true-to-life colors and clear image details.
• Protecting Equipment and Components: In devices like projectors and incandescent lamps, it prevents heat generated by infrared light from damaging lenses or internal electronic components. When placed in front of CCD/CMOS sensors, it suppresses moiré patterns caused by high-frequency light waves, thereby extending device lifespan.

• The core principle of infrared cut-off filters relies on wavelength-selective absorption and reflection of light, achieved through the following technologies:

  1. Multi-layer Coating Structure: Alternating layers of high and low refractive index films are deposited on optical substrates. The interference effects between these layers ensure high transmission of visible light (400-630nm) while reflecting or absorbing near-infrared light (700-1100nm).
  2. Material and Process Optimization: By combining materials with different infrared absorption characteristics (e.g., high infrared absorption materials with low absorption materials) and adjusting film thickness and layer count, the cut-off wavelength range can be precisely controlled. For instance, increasing the number of layers enhances infrared blocking capability.
  3. Substrate Selection: Common substrates include optical plastic films (with thicknesses of only a few micrometers, suitable for slim devices) and optical glass (heat-resistant and highly stable, ideal for professional equipment).