Instrument Function

The finite Fourier Cosine Transform of an Apodization Function, also known as an Apparatus Function. The instrument function $I(k)$ corresponding to a given Apodization Function $A(x)$ is then given by

$$I(k)=\int_{-a}^a \cos(2\pi kx)A(x)\,dx.$$

See also Apodization Function, Fourier Cosine Transform