Nomenclature of standard filters

Read the following nomenclature description to know more about of how DELTA specifies filter names.

1- Bandpass filters
2- Edge filters
3- Dichroic / Colour Beamsplitter

Bandpass Filters

Denomination
All types of bandpass filters (Laserline, narrow band, broad band) use the same denomination standard:
BP λc / Δλ

Centre wavelength λC
λC is the arithmetic mean of the two wavelengths where the filter transmits: ½  x Taverage.

λC = (λFWHM2 - λFWHM1) / 2
λFWHM1= λ1 (½ x Taverage)
λFWHM2= λ2 (½ x Taverage)

Where Taverage is the average transmission in the passband.

Bandwidth: FWHM Δλ
The FWHM (Full Width Half Maximum) is described as follows:
FWHM = Δλ = (λFWHM2 - λFWHM1)

Transmission band: T(λ1 - λ2)
T (λ1 - λ2) is the wavelength bandwidth where the transmission is high and T is the associated minimum average transmission in the passband. This may also be divided into several bands, e.g.

λ1 - λ2 with minimum average transmission T1
λ3 - λ4 with minimum average transmission T2
λ5 - λ6 with minimum average transmission T3

Rejection band:  Tb(λ1 - λ2)
Tb (λ1 - λ2) is the wavelength bandwidth where the transmission is low and Tb is the associated average transmission in the band. This may also be divided into several bands, e.g.

λ1 - λ2 with minimum average blocking (OD5 for example) Tb1
λ3 - λ4 with minimum average blocking (OD5 for example) Tb2
λ5 - λ6 with minimum average blocking (OD5 for example) Tb3

Tolerance numbers
Typical tolerance numbers are given on the center wavelength and the bandwidth.

Example:  BP 450/40  with 450 +/- 2nm and 40 +/- 2nm

Edge Filters

Denomination
- Long Wave Pass: LP λC
- Short Wave Pass: SP λC

Edge wavelength λC
λC is the wavelength where the transmission T of the filter has reached 50% of the filter's maximum transmission level.

Example: The nomenclature for an edge filter is e.g. LP 510 where λC = 510 nm.

Rejection band
Tb (λ1 - λ2) is the wavelength bandwidth where the transmission is low and Tb is the associated average transmission in the band. This may also be divided into several bands, e.g.

λ1 - λ2 with minimum average blocking (OD5 for example) Tb1
λ3 - λ4 with minimum average blocking (OD5 for example) Tb2
λ5 - λ6 with minimum average blocking (OD5 for example) Tb3

Transmission band
T(λ1 - λ2) is the wavelength bandwidth where the transmission is high and T is the associated average transmission in the passband. This may also be divided into several bands, e.g.

λ1 - λ2 with minimum average transmission T1
λ3 - λ4 with minimum average transmission T2
λ5 - λ6 with minimum average transmission T3

Tolerance numbers
Typical tolerance numbers are given on the edge wavelength.

Example:  LP 490 +/- 2nm.

Dichroic / Colour beamsplitters

Denomination
- Long Wave Pass Dichroic: DCLP λC
- Short Wave Pass Dichroic: DCSP λC

Edge wavelength λC
λC is the wavelength where the transmission T of the filter has reached 50% of the average transmission level.

Example: The nomenclature for a dichroic is e.g. DCLP 395 where λC = 395 nm.

Reflection band R (λ1 - λ2)
R (λ1 - λ2) is the wavelength bandwidth where the reflection is high and R is the associated average reflection in the band. This may also be divided into several bands, e.g.

λ1 - λ2 with minimum average reflection R1
λ3 - λ4 with minimum average reflection R2
λ5 - λ6 with minimum average reflection R3

Transmission band T (λ1 - λ2)
T (λ1 - λ2) is the wavelength bandwidth where the transmission is high and T is the associated average transmission in the passband. This may also be divided into several bands, e.g.

λ1 - λ2 with minimum average transmission T1
λ3 - λ4 with minimum average transmission T2
λ5 - λ6 with minimum average transmission T3

Tolerance numbers
Typical tolerance numbers are given on the edge wavelength.

Example:  DCLP 490 +/- 2nm.