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Explanation of Related Terms for Filter Parameters (Part 2)

Cut-off range: The cut-off range refers to the wavelength interval that represents the spectral region of energy attenuated by the filter. The degree of blocking is typically specified in terms of optical density.

Optical Density (OD): OD stands for optical density. When light passes through a sample, some of the light is absorbed. OD represents the measure of the energy blocked or rejected by the filter; it is a specialized term used in detection methods. The unit of measurement for OD is expressed as an OD value, calculated as follows: OD = lg(1/trans), where trans refers to the transmittance of the sample being measured. A high OD value indicates low transmittance, while a low OD value indicates high transmittance. An OD of 6.0 or greater is suitable for applications requiring extreme blocking, such as Raman spectroscopy or fluorescence microscopy. An OD between 3.0 and 4.0 is ideal for laser-based separation and purification, machine vision, and chemical detection, whereas an OD of 2.0 or less is optimal for color sorting and spectral order separation.

OD* indicates the cutoff; according to OD1 through OD6, the transmittance of the cutoff band ranges from 0.1 to 0.000001.
OD Number, Cut-off Wavelength Transmittance
OD1 = 0.1, which is 10%.
OD2 = 0.01, or 1%
OD3 = 0.001, which is 0.1%.
OD4 = 0.0001, which is 0.01%.
OD5 = 0.00001, which is 0.001%.
OD6 = 0.000001, which is 0.0001%.

Deadline number Deadline band

A 400~1100nm

B 300~1200nm

C 200~2000 nm

D 400~700nm

E 400~800nm

F 400~1000 nm

G 300~900nm

H 500~1000nm

I 800~1000nm

J 700~1200nm

K 200~1100nm

L 200~1200nm

M 200~1400nm

N 400~1200nm

O 200~1150nm

P 200~800nm

Q 350~700nm

U 200~700 nm

V 300~950nm

W 200~1000nm

X 200~750 nm

For example:

OD3-A: The transmittance of light waves within the wavelength range of 400–1100 nm is 0.001, excluding the spectral bands on either side of the central wavelength, each spanning half of the bandwidth.

OD3-B: The transmittance of light waves within the wavelength range of 300–1200 nm is 0.001, excluding the spectral bands on either side of the center wavelength, each spanning half of the bandwidth.

OD3-C: The transmittance of light waves within the wavelength range of 200–2000 nm is 0.001, excluding the spectral bands on either side of the central wavelength, each spanning half of the bandwidth.

OD3-D: The transmittance of light waves within the wavelength range of 400–700 nm is 0.001, excluding the band spanning half of the bandwidth on either side of the central wavelength.

OD3-K: The transmittance of light waves within the wavelength range of 200–1100 nm is 0.001, excluding the spectral bands on either side of the central wavelength, each spanning half of the bandwidth.

OD4-A: The transmittance of light waves within the wavelength range of 400–1100 nm is 0.0001, excluding the spectral bands on either side of the center wavelength, each spanning half of the bandwidth.

OD4-B: The transmittance within the wavelength range of 300–1200 nm is 0.0001, excluding the band spanning half of the bandwidth on either side of the central wavelength.

OD4-C: The transmittance within the wavelength range of 200–2000 nm is 0.0001, excluding the spectral bands on either side of the center wavelength, each spanning half of the bandwidth.

OD4-D: The transmittance of light waves within the wavelength range of 400–700 nm is 0.0001, excluding the band spanning half of the bandwidth on either side of the central wavelength.

OD4-K: The transmittance within the wavelength range of 200–1100 nm is 0.0001, excluding the spectral bands on either side of the center wavelength, each spanning half of the bandwidth.

The cutoff wavelength is a term used to denote the wavelength at which the transmittance through the filter increases to 50%. The cutoff wavelength is indicated by λcut-on in the figure below.

The cutoff wavelength is a term used to describe the wavelength at which the transmittance of a filter drops to 50%. The cutoff wavelength is denoted by λcut-off in the figure below.

Cut-off Wavelength Illustration

What is a linear gradient filter?

Explanation of Terms Related to Filter Parameters (Part 1)

What is a linear gradient filter?

Explanation of Terms Related to Filter Parameters (Part 1)

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