Center Wavelength is the midpoint of its transmission band. It is calculated by averaging the two wavelengths where the light transmission is at 50% of its peak value. This single number serves as a primary reference point to define the spectral location of the filter's passband.
Example Calculation
Given Parameters
Consider a standard optical bandpass filter with the following specifications measured at 50% transmission:
- Cut-on wavelength (short wavelength side): 510 nm
- Cut-off wavelength (long wavelength side): 530 nm
Calculation
To find the center wavelength, you average the two 50% transmission points using the formula: (Cut-on + Cut-off) / 2.
- Sum the wavelengths: 510 + 530 = 1040
- Divide by two: 1040 / 2 = 520