A Koehler integrator device (10) comprises a collimating lens (11) being arranged for collimating a light field created by an incoherent or partially coherent light source, a pair of planar first and second micro-lens arrays (12, 13) being arranged for relaying portions of the collimated light field along separate imaging channels, wherein all micro-lenses of the first and second micro-lens arrays (12, 13) have an equal micro-lens focal length and pitch and the micro-lens arrays (12, 13) are arranged with a mutual distance equal to the micro-lens focal length, and a collecting Fourier lens (4) having a Fourier lens diameter and a Fourier lens focal length defining a Fourier lens front focal plane and a Fourier lens back focal plane, wherein the Fourier lens (14) is arranged for superimposing light from all imaging channels in the Fourier lens front focal plane and wherein the second micro-lens array (13) is arranged in the Fourier lens back focal plane, wherein a third micro-lens array (15) is arranged in the Fourier lens front focal plane for creating a wavelength independent array of illumination spots. Furthermore, a confocal microscope apparatus, which comprises the Koehler integrator device, and a method of using the confocal microscope apparatus are described..