What is the difference between short pass and long pass filter?

Difference Between Short Pass and Long Pass Filters

Short pass and long pass filters are types of optical filters that selectively transmit light within a specific wavelength range while blocking others. They are widely used in various applications, including photography, laser systems, and scientific research. The key difference between them lies in their transmission and blocking properties relative to a cutoff wavelength.

Short Pass Filters (SPF)

• Transmission: Short pass filters allow light with wavelengths shorter than the cutoff wavelength to pass through.
• Blocking: They block light with wavelengths longer than the cutoff wavelength.
• Applications: Used in fluorescence microscopy, machine vision systems, and in ensuring the purity of laser beams by blocking unwanted infrared (IR) light.

Long Pass Filters (LPF)

• Transmission: Long pass filters allow light with wavelengths longer than the cutoff wavelength to pass through.
• Blocking: They block light with wavelengths shorter than the cutoff wavelength.
• Applications: Commonly used in spectroscopy, environmental monitoring, and in protecting sensitive sensors from UV damage.

Comparison Table

Both filters are essential in controlling the spectral properties of light in various optical systems, but their selection depends on the specific requirements of the application, such as the desired wavelength range to be transmitted or blocked.