A light source, whether natural or man-made, typically emits a broad spectrum of wavelengths, including ultraviolet and infrared. In some applications, this full spectrum is acceptable or even desired. In others, however, it may be necessary to limit the wavelengths passing from the light source. This is where optical filters come in.
Filters, at their most basic level, are used to control the wavelengths of light that pass through an optical system. They can be used in conjunction with imaging and lighting systems to produce a wide variety of effects. Optical filters are present in many everyday objects such as cameras, architectural light fixtures and automobile headlights. They're also found in applications such as spectroscopy, aerospace engineering and virtual reality devices.
Increasingly efficient LED lights have dramatically impacted not just the lighting industry but also most industries in which light is artificially generated. However, the visible output of an LED light is unique and has created a demand for a unique coating for optical filters. This demand has made providing optical filters for LED lights increasingly important for optical coaters across the industry. This particular filter application offers an excellent example of how an optical filter works.
Making LED Light Resemble Sunlight
A common use of LED optical filters is to make an LED light source look more like the light from the sun. The first image below shows the emission pattern of an LED light bulb. The spike in the blue region of the visible spectrum causes LED light to look harsh to some observers. A cut-on optical filter can remedy this problem, as shown in the second and third images.
Image 1: This is the emission spectrum for a typical LED light bulb. The blue LEDs typically used in these bulbs create an unwanted peak in the blue wavelengths around 450 nm.
Image 2: This cut-on filter that is designed to block unwanted blue light in the LED light bulb’s light emission spectrum.
Image 3: By passing the LED's light through the cut-off filter, the resulting transmission spectrum better matches natural sunlight.
VisiMax has been providing LED optical filters for over a decade. Our in-house optical design team is experienced not only in designing filters for this particular output but also in achieving highly specific color outputs for a wide variety of applications.
This is just one example of how optical filters can be selectively chosen to fit an application. To learn more about the features and specification of basic optical filter types, download our ebook: