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Optical filter and Technical Specifications

Filter Spectral Types and Technical Specifications

Products

  • Technical Specifications of Interference Edge Filter
  • Cut-on/off wavelength definition: the wavelength at which the transmittance drops to 50% of the peak transmittance, which is the critical value distinguishing the passband from the stopband.
  • Definition of blocking depth (Blocking/Optical Density, OD): the light blocking capability within the stopband, OD = lg(1/T) (T is the transmittance).
  • Peak transmittance / average transmittance: the maximum transmittance within the passband / the average transmittance within the passband.
  • Transition Band / Slope: Describes the steepness of the cutoff edge.
  • Specifications of Edge Filter
  • Edge filter type
  • 1. LongPass: Simply understood, it means that when the wavelength >cut-on wavelength, it transmits; when the wavelength＜cut-on wavelength, it is blocked.
  • 2. Shortwave Pass (ShortPass): Simply put, it blocks when the wavelength > cut-off wavelength and transmits well when the wavelength ＜ cut-off wavelength.
  • The influence of the angle of incidence (oblique incidence, conical incidence)
  • 1. Overall spectrum blue shift (moving toward shorter wavelengths).
  • 2. The shape of the spectral curve deteriorates, and the cutoff band shrinks and narrows.
  • 3. The separation of s- and p-polarized light increases with the increase of the incident angle, causing the transition band to exhibit steps or for the transition band to become gentler.
  • 4. Cone angle incidence effect: Because the most common lens focusing, optical fiber emission, and imaging light paths are not parallel light but cone light with angular distribution, the equivalent "average angle" causes a blue shift, and similarly, there will be a smoothing of the transition band, among other effects.
  • AOI blue shift of optical filter
  • Bandpass filter technical specifications
  • Center Wavelength (CWL): The wavelength corresponding to the center position of the passband.
  • Full width at Half Maximum (FWHM): the wavelength width at 50% of the peak transmittance
  • Peak transmittance / average transmittance: the maximum transmittance / average transmittance within the passband.
  • Transition Band/Slope: Describes the steepness of the edges on both sides of the passband.
  • Specification of Optical Bandpass filter
  • Bandpass filter type
  • 1. Broadband WBP: Full width height max transmittance is relatively wide compared to the central wavelength.
  • 2. Band-pass (BP) and narrow band-pass (NBPF): the full width at half maximum is relatively narrow compared to the central wavelength.
  • The influence of the angle of incidence (oblique incidence, conical incidence)
  • 1. Overall spectrum blue shift (moving toward shorter wavelengths).
  • 2. The shape of the spectral curve deteriorates, and the cutoff band shrinks and narrows.
  • 3. The separation of s- and p-polarized light increases with the increase of the incident angle, causing the transition band to exhibit steps or for the transition band to become gentler.
  • 4. Cone angle incidence effect: Because the most common lens focusing, optical fiber emission, and imaging light paths are not parallel light but cone light with angular distribution, the equivalent "average angle" causes a blue shift, and similarly, there will be a smoothing of the transition band, among other effects.
  • Influence of the angle of incidence for optical filter