Apparatus and methods are described for optically analyzing an object having a plurality of layers, without needing to use a reference mirror. Light is generated using an extended broadband light source. The light is directed toward the object, such as to create respective images of the light source on the respective layers of the object. Light that is reflected from a point of the object is gathered into a conjugate point in a detector. The thicknesses of the plurality of layers at the point of the object are determined, by analyzing, within the gathered light, interference between light reflected from the plurality of layers of the object at the point. Other applications are also described.
