SPECTRAL SHIFTS OF PARTIALLY COHERENT-LIGHT PRODUCED BY PASSING THROUGH AN ANNULAR APERTURE

It is shown that, when partially coherent light is incident upon an annular aperture, the maximum of the spectrum of the light at an.on-axis observation point in the far zone of the aperture shifts towards blue side or red side, compared with the spectrum in the aperture. The spectral shifts of light not only depend on the ratio of the outer radius of the aperture to the effective correlation length of the light in the aperture, but also the ratio of central obstruction of the annular aperture.