Overview of Linear Variable Filters (LVFs)

Linear Variable Filters (LVFs) are innovative optical components that feature a continuous change in spectral characteristics along one dimension. These wedge-shaped filters replace multiple fixed-wavelength filters, allowing for dynamic wavelength adjustments by sliding the filter. By combining a Linear Variable Long-Pass Filter and a Linear Variable Short-Pass Filter, a band-pass filter can be created, or two LVFs can be stacked to achieve deep cutoff performance.

The unique optical properties of LVFs are not just a buzzword—they represent a paradigm shift in optical design. These filters exhibit varying spectral properties across different positions, with these properties changing linearly with spatial location. This linear variation offers several advantages, including continuous wavelength transition, customizable channels, and stable performance. Advanced manufacturing techniques, such as ion-assisted deposition or ion beam sputtering, are used to deposit multilayer films with varying thicknesses on the substrate, creating a wedge-shaped film structure that enables linear spectral changes.

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Features of Linear Variable Filters (LVFs)

1. Continuous Wavelength Control:

LVFs allow for precise and continuous adjustment of center or edge wavelengths, making them ideal for applications requiring dynamic spectral control.

2. Compact Design:

Replacing multiple fixed filters with a single LVF simplifies optical systems, reducing complexity and improving reliability.

3. Versatile Spectral Manipulation:

By combining LVFs, users can create custom spectral filters, such as band-pass or deep-cutoff filters, tailored to specific applications.

4. Advanced Manufacturing Techniques:

The use of ion-assisted deposition or ion beam sputtering ensures high-quality film layers with precise thickness control, enabling consistent and reliable spectral performance.

Specifications of Linear Variable Filters (LVFs)

Size (gradient area valid area)	22.5mm*13.7mm	22.5mm*13.7mm
Rangle of Wavelength	380nm-850nm	400-1000nm
Peak transmittance	5%-90%	≥60%
FWHM	2%*中心波长	1.5%*中心波长
Cut-Off	OD3	OD3
Linear rate of change	22.3nm/ mm	50mm/ mm
S/D	60-40	60-40
W avefront distortion	λ/10	λ/10

Applications of Linear Variable Filters (LVFs)

LVFs are not limited to spectral imaging but are also widely used in other fields, including:

1. Portable Spectrometers:

LVFs provide efficient optical separation, enabling compact and high-performance spectroscopic devices for on-the-go applications.

2. Grating Secondary Separation/Cutoff:

LVFs enable precise optical control, enhancing the performance of systems that require accurate wavelength isolation.

3. Laser Mirror Design:

LVFs play a crucial role in laser systems by allowing flexible spectral tuning and control.

4. Multispectral and Hyperspectral Imaging:

LVFs are integral to advanced imaging systems, enabling detailed spectral analysis for applications in aerospace, environmental monitoring, and biochemical research.