Optical Filter Manufacturing: Products

Also referred to as waveband, passband, or bandwidth, bandpass is the wavelength range used to denote a specific part of the spectrum that passes incident energy through a filter. The first order is always at the design wavelength of the filter.

The blocking amount is the amount of light that is rejected, not passed, by a filter outside the passband. It is expressed as the ratio of total energy transmitted outside the passband to the total energy transmitted within the passband. Blocking values are given over a specified wavelength range.

Also referred to as the stopband, blocking range is a wavelength range used to specify a spectral region of energy that is not transmitted by a filter. It is typically specified in terms of Optical Density (OD).

Used to denote the peak transmitting wavelength of a filter, it is the midpoint determined by the passband wavelengths where the transmittance is 50% of the peak (denoted by the Full-Width at Half Maximum).

Cut-off wavelength is the wavelength at which transmission decreases to 50% in a shortpass filter.

In filter terminology, cut-on is the wavelength at which the transmission increases to 50% throughput in a longpass filter.

Filters are optical components that transmit, reflect, or absorb certain wavelengths or frequencies of light. Filter types include bandpass, longpass, shortpass, interference notch and rugate notch, color, dichroic, and neutral density.

A specific wavelength region of the bandwidth of a filter defined by the two points of the passband where transmittance is 50% of the peak.

A type of filter in which the transmission band is a region of longer wavelengths as compared to the region blocked.

A type of filter that yields a constant value for attenuation, or optical density, over a bandwidth (i.e. spectrally flat). It is useful for attenuating, or reducing, overall light in a system.

A type of filter designed to block a pre-selected bandwidth and transmitt all other wavelengths within the design range of the filter. Notch filters are manufactured using the dielectric stack method which involves using a series of thin layers of dielectric materials, of alternating refractive index.

Optical density is a value that describes the amount of energy that can pass through an optical material. It is directly related to the transmittance of the material. The greater the OD, the more light being blocked.

The highest transmittance value for light being passed by a filter.

The wavelength of light that has the highest transmittance value.

Radiation that changes direction, but not wavelength, after contact with a material surface.

A type of filter where the transmission band is a wavelength range of shorter wavelengths, typically lower than the region blocked.

The amount of radiant energy that passes through an optical medium, not being absorbed, reflected, or scattered.

The peak to peak distance covered by one cycle of an electromagnetic wave. It is inversely related to frequency. The longer the wavelength, the lower the frequency; conversely, the shorter the wavelength, the higher the frequency.