Exploring Dichroic Filters: What They Are and How They Work

Dichroic Filters

Do you know about dichroic filters?

Dichroic filters are an interesting type of optical filter that can divide light into two different colors. They are made up of thin layers of materials that selectively reflect certain wavelengths of light while allowing others to pass through. In this blog post, we will explore what dichroic filters are, how they work, and their various applications.

In case you have limited knowledge of what dichroic filters are and their usage, this blog is for you. In this blog, we will discuss intricately about dichroic filters. 

What Are Dichroic Filters?

Professional dichroic filters, also known as thin-film filters or interference filters, are optical components designed to separate white light into its component colors. The filter is coated with a series of ultra-thin layers that are less than the wavelength of light and designed to reflect specific wavelengths while transmitting others.

One benefit of dichroic filters is that they allow for the blocking or reflecting of unwanted light while allowing desired spectral bands to pass through. This makes them useful in many applications where precise color management is necessary.

How Do Dichroic Filters Work?

The main principle behind how a dichroic filter works is the phenomenon called interference. Interference occurs when two waves interact, causing either an increase or decrease in amplitude (the height) depending on how closely the waves line up with each other.

When light travels from one medium to another (such as air to glass), it undergoes a change in speed and direction. This results in some portion of the reflected beam being partially out-of-phase. The remaining out-of-phase part interacts with subsequent reflections inside the thin film material, producing constructive and destructive interference patterns resulting in selective reflection at specific angles and frequencies.

Thin films used for dichroic interferential coatings vary between 1/10th-1/4th thickness compared to conventional silver/gold coatings, which may be 50 times thicker or more. These films can be made by evaporating atoms onto solid substrates such as silicon dioxide/silicon dioxide. Further stacking is done by applying a proprietary multi-coating process under vacuum or deposited on an optical plastic substrate by sophisticated means such as sputtering or organometallic chemical vapor deposition (CVD).

The complexity of the layers plays an important role in emphasizing the color properties of these filters. The thickness and number of films determine what wavelengths are reflected vs. transmitted and can result in several unique colors being created by changing just one layer.

Applications of Dichroic Filters

Dichroic filters have numerous applications across various industries, including photography, lighting design, astronomy, microscopy, spectroscopy, and fluorescence imaging. Some ways that dichroic filters are used include:

Photography: Dichroic filters play a key role in enhancing the color balance in photography- examples could be reducing the blue sky without affecting skin color details and its component colors.

Lighting Design: Dichroic coatings have been incorporated into lighting to alter the tint of the light through absorption/reflection rather than adjusting filament temperature alone, thus preserving output brightness.

Astronomy: These types of filters allow astronomers to isolate specific spectral regions while conducting space studies like sunspot analysis or exoplanet detection.

Microscopy: They filter out unwanted background illumination for documentation clarity from staining/fluorescence techniques used with live cells or tissue samples where there are multiple overlapping color sources present.

Spectroscopy: Engineers use them as wavelength-selective elements at different points during an experimental setup to split white light into its constituent colors, thus giving more precise spectral information for thin-film measurements.

Fluorescence Imaging: Superimposing multiple lasers over distinct emitter wavelengths similar to digital sensitivity tuning diagnostic platforms and camera long-pass band selection according to labeling acceptability requirements such as those needed for retina identification probes testing e-z pass registrations.


In conclusion, we found out how dichroic filters work: thin layers that reflect particular parts inferences principle due to hindering certain range spectrums passing while allowing others through. With their versatility in many industries and applications, these filters are an elegant solution to effective spectral control and are perfect for demanding fine-tuned output needs.