A novel interference microscope for three-dimensional (3D) imaging based on a wavelength-to-depth encoding technique is presented. Wavelength-to-depth encoding is realized by use of a diffractive lens and wavelength tuning. A high depth resolution of 0.71 mum is obtained with 0.90-N.A. objective lenses. Experimental measurements of a four-level grating are presented, and the results are found to be comparable with those obtained with a Dektak profilometer and a similar interference microscope that uses mechanical depth scanning. The system is promising for fast, noncontact, high-resolution 3D imaging.