Dichroic Mirrors and Their Applications

What are Dichroic Mirrors?

Dichroic mirrors, also known as dual-band mirrors or dichroic reflectors, are a type of special mirror. They are typically used behind a light source to reflect visible light while allowing invisible infrared light to pass through. In simple terms, they can separate light beams by wavelength, reflecting wavelengths below a certain cutoff and transmitting at longer wavelengths. Based on this principle, they play an important role in the optical application.

Types and Spectra of Dichroic Mirrors

Dichroic mirrors' angle of incidence (AOI) is usually 45 degrees. Depending on the way they transmit light, dichroic mirrors can be classified into three categories: long-pass dichroic mirrors, short-pass dichroic mirrors, and multi-band dichroic mirrors. These classifications also include hot and cold mirrors used to reflect or otherwise suppress unwanted heat in thermal applications, which are also types of dichroic mirrors.

• Long-pass dichroic mirrors: Short wavelengths have high reflectance, while long wavelengths have high transmittance.

  
  

• Short-pass dichroic mirrors: Short wavelengths have high transmittance, while long wavelengths have high reflectance.

  
  

• Multi-band dichroic mirrors: These are a special type of optical element capable of reflecting and transmitting light within different wavelength ranges simultaneously.

Manufacturing Methods of Dichroic Mirrors

Dichroic mirrors are primarily manufactured on transparent substrates (e.g., glass) using techniques such as electron beam deposition, ion beam sputtering (IBS), and ion-assisted deposition (IAD). These methods enable precise control of each layer's thickness to selectively reflect and transmit light of specific wavelengths.

Ecoptik utilizes hard dielectric coating technology to enhance the high transmittance, high reflectance, and durability of dichroic mirrors. This makes them not only color accurate but also environmentally stable, meeting the requirements of various application settings. Typical features include:

• IAD hard coating: Adoption of ion-assisted deposition technology to achieve durable coatings.

  
  

• Wavelength range: Covers from ultraviolet dichroic filters to infrared filters, adapting to different applications.

  
  

• High reflectance: Ensures optimal reflection of unwanted wavelengths.

  
  

• High transmittance: Ensures good transmission of selected wavelengths.

  
  

• Surface quality: Provides 40/20 and 60/40 standards.

Main Applications of Dichroic Mirrors

Fluorescence Microscopy

In the field of scientific research, particularly in biology and medicine, dichroic mirrors are a component of fluorescence microscopes. They act as beam splitters to efficiently direct specific excitation frequencies of light onto the sample. This allows for the capture of detailed fluorescent images of specimens, enabling researchers to observe cellular structures, proteins, and other biomarkers with high specificity and sensitivity.

LCD Projectors

In the field of digital imaging and display, dichroic mirrors are used in some LCD projectors. The optical filter film is used to split the white light emitted by the lamp into its primary components—red, green, and blue. This separation process enhances the color purity and brightness of the projected image, leading to a more vivid and engaging viewing experience.