Custom Optical Filters: From Specification to Production
A custom optical filter begins with a problem that cannot be solved adequately by selecting an existing component. The required wavelength may fall between standard filter ranges. The passband may need a different width or position. Blocking may be required across a particular detector response range, or the filter may need to operate at an […]
Applications of Optical Filters
Optical filters are used wherever an optical system needs to distinguish useful light from wavelengths that would otherwise interfere with an image, measurement or detection process. The underlying function may appear straightforward: transmit one part of the spectrum while rejecting another. The reason for doing so, however, varies considerably between applications. In machine vision, filtering […]
Optical Filter Materials
The material used to manufacture an optical filter is not simply a mechanical support for the coating. It forms part of the optical path and can influence transmission, absorption, refractive behaviour, thermal stability and the physical durability of the finished component. This becomes particularly important as an optical system moves beyond the visible spectrum. A […]
Optical Filter Performance Characteristics
Two optical filters designed for the same general wavelength region can perform very differently within an optical system. A centre wavelength or filter type alone does not define how effectively a component will transmit the required signal, suppress unwanted radiation or maintain its spectral response under operating conditions. Filter performance is therefore described using a […]
How to Choose an Optical Filter
Choosing an optical filter begins with the optical system, not with the filter itself. A wavelength value may provide the starting point, but it does not define what the finished component needs to achieve. The useful signal has to be identified, unwanted wavelengths need to be understood, and the filter must operate alongside the source, […]
Types of Optical Filters
Optical filters are defined by the way they control light across a specified wavelength range. Some transmit a narrow region of the spectrum and reject wavelengths on either side. Others separate shorter wavelengths from longer ones, reduce optical intensity or divide different spectral regions between separate optical paths. These differences are not simply variations in […]
How Do Optical Filters Work?
Light passing through an optical system can be transmitted, reflected, absorbed or scattered. An optical filter uses these interactions in a controlled way to alter the spectral content of the light reaching a detector, sensor or subsequent optical component. The required behaviour may be relatively simple, such as removing ultraviolet or infrared radiation from an […]
What Is an Optical Filter?
Every optical system relies on light as its source of information. Whether the objective is to capture an image, inspect a manufactured component, identify the chemical composition of a material or detect thermal radiation, the quality of the result depends on the light reaching the detector. If the wrong wavelengths are present, the information being […]
What Are NVIS Filters and How Do They Work?
Cockpit displays used alongside night vision goggles require careful control of their spectral output. A display can appear perfectly acceptable to the unaided eye while emitting sufficient energy within wavelengths detected by night vision equipment to interfere with its operation. NVIS filters are used to control this unwanted output while retaining the visible light required […]