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Rejection Band

Overview

Rejection band filters block a narrow and precise spectral band, such as the monochromatic light from a laser, while efficiently transmitting both longer and shorter wavelengths than those in the rejection band.

Products

  • VIS Laser Rejection – 401 - 750nm
  • IR Laser Rejection – 751 - 2500nm
  • For custom rejection band filters, use our Build-a-Filter request form

Filter Description

  • Center Wavelength (CWL)—the wavelength at the center of the rejection band.
  • Bandwidth—the bandwidth at 50% of the maximum rejection measured in OD, typically 10-3 (OD 3).
  • Optical Density (OD)—the degree of attenuation at the CWL of the rejection band.

Filter Types

Rejection Band (RB)

Attenuate a laser line, blocking more than 99.9% (OD 3) of light in a 15–40nm band width. The average transmission outside the stopband is 75%, with the exception of those spectral regions where higher and lower harmonics result in high reflectivity. These rejection regions recur at wavelengths that are approximately 0.8 times (on the short wavelength side) and 1.25 times (on the long wavelength side) the principal rejection wavelength. RB filters can be designed to reflect up to three distinct bands and to operate at non-normal angles of incidence. (See Figure 1)

rb_spectral

Figure 1: RB Filter Spectral Performance
Spectral trace measurement of a 632.8 RB filter. Rejection regions recur at harmonic wavelengths both longer and shorter than the principal rejection band.

Laser Protection (LR)

Produced to meet the special requirements of detector or eye protection. They can be designed for performance at multiple angles of incidence, photopic quality, and resistance to moisture and chemical exposure. They are often used for goggles or windows in applications where scattered laser light poses a potential hazard.

LR filters attenuate the emission of one or more designated lasers up to OD 5, while transmitting more than 50% within the passbands. For eye comfort, these filters feature corrected color balance coatings deposited on optical quality glass. Laser protective filters that provide the proper combination of visibility and protection during beam alignment are also available. (See Figure 2)

lr_spectral

Figure 2: LR Filter Spectral Performance
Spectrograph of light transmitted through the S3A filter which attenuates the NdYag laser lines (532nm and 1064nm) and the Ruby laser line (694nm). Other attenuation levels are available. Note the favorable color balance of high blue, green, and red transmission.

Standard Specifications: Rejection Band Filters

The following specifications apply to all Omega Optical rejection band filters unless other custom specifications are requested.

CWL Tolerance +5%, -1% of nominal CWL
Minimum Peak Attenuation OD 3
Minimum Average Transmission 75%
Angle of Incidence
Temperature of Measured Performance 20°C
Operating Temperature Range -60°C to +80°C
Humidity Resistance Per Mil-STD-810E, Method 507.3 Procedure I
Coating Substrates Optical quality glass
Surface Quality 80/50 scratch/dig per Mil-O-13830A
Outer Dimension Tolerance +0, -0.25mm (+0, -0.01")
Minimum Clear Aperture 4mm less than nominal outside dimension
Construction and Thickness (a) 0.75 ±0.1 thickness, durable front-surface coating on substrate; (b) 1.5 +0, -0.5 thickness, coating protected between substrate and laminated cover glass

 

Documentation.

Spectrophotometric trace of rejection bands with a resolution of 0.1nm. Transmission accuracy on all spectrophotometric traces is ±1%.

Note: All rejection band filters are available with imaging quality; minimum transmitted wavefront error and anti-reflective coating performance are quoted based on individual filtering requirements.