Linear Variable Edge Filters or continuously variable edge filters are a special kind of optical edge filters with their edge wavelengths shifting across the length of the filter. There is a linear relationship between the changing edge wavelengths and the position along the filter. Linear variable Edge Filters contain two subcategories, linear variable longpass filters and linear variable shortpass filters. Linear variable longpass filters transmit light beyond the specific cut-on wavelengths while rejecting the unwanted light, linear variable shortpass filters transmit light below the designated cut-off wavelengths while blocking the remaining. Unlike traditional longpass and short filters that offer fixed cut-on/cutoff wavelengths, linear variable longpass, and shortpass filters provide the flexibility to adjust the cut-on or cutoff wavelength, allowing for precise control over the spectral characteristics of the transmitted light. Linear Variable Edge Filters find versatile utilities in various applications such as spectroscopy, fluorescence microscopy, hyperspectral imaging, and optical instrumentation. 

Shanghai North Optics offers Standard and Custom Longpass and Shortpass Linear Variable Edge Filters. These filters utilize a combination of microfabrication techniques and thin film deposition technologies, allowing for the production of high-performance linear variable edge filters with precise control over their optical properties. As can be witnessed from the transmission curves, these linear variable edge filters boast steep spectral cut-on/cutoff, excellent transmittance within the passband, and high optical density ensuring excellent out-of-band light suppression and minimal spectral leakage. Our filters are in particular useful in situations where precise and tunable manipulation over the transmitted wavelength range is required, such as in spectral analysis, where the filters can be used to isolate specific spectral lines or bands of interest. These linear variable filters provide reliable performance in demanding laboratory and industrial environments.

Through combined usage of one of our linear variable longpass filters with a corresponding linear variable shortpass filters, a tunable Bandpass Filter can be obtained where both center wavelength and bandwidth are tunable.

Figure 1. The transmission curve of our linear variable longpass filters