A method and apparatus for focusing a device for imaging a biologic sample is provided. A method aspect includes the steps of: disposing lenslets within a biologic sample, which lenslets have a height and a refractive index, which refractive index is different from that of the sample, wherein one or both of the imaging device and the sample are relatively locatable so a focal position of the imaging device can be moved along the height of the lenslets; imaging a portion of the sample including lenslets using transmittance at one or more wavelengths; determining an average light transmittance intensity of the sample at the wavelengths; determining an average light transmittance intensity of a region of each lenslet at the wavelengths; and determining the focal position of the imaging device using the average light transmittance intensity of the sample and the average light transmittance intensity of the region of the lenslets.