A method of measuring an optical property of a sub micrometer region of a sample by: Interacting a probe tip of the probe microscope with a region of the sample; Illuminating the sample with a beam of light from at least one broadband radiation source, wherein the method includes: a. Interfering a reference beam with at least one of (i) light scattered from the region of tip/sample interaction and (ii) light incident on the tip/sample interaction region; wherein the reference beam has an adjustable phase; b. At least one of selecting or determining a limited number of reference phases of the reference beam that produce substantially different optical responses for at least two different wavelengths, wherein the limited number of reference phases less than 10; c. Measuring a signal indicative of the optical property of the sample at only the limited number of reference phases; d. Constructing at least one image of the optical property of the sample at a plurality of positions on the sample; and Wherein the limited number of reference phases comprise i) a reference phase in which one of the at least two different wavelengths has maximum constructive interference and ii) another reference phase in which another one of the at least two different wavelengths has maximum destructive interference. Interacting a probe tip of the probe microscope with a region of the sample; Illuminating the sample with a beam of light from at least one broadband radiation source, wherein the method includes: a. Interfering a reference beam with at least one of (i) light scattered from the region of tip/sample interaction and (ii) light incident on the tip/sample interaction region; wherein the reference beam has an adjustable phase; b. At least one of selecting or determining a limited number of reference phases of the reference beam that produce substantially different optical responses for at least two different wavelengths, wherein the limited number of reference phases less than 10; c. Measuring a signal indicative of the optical property of the sample at only the limited number of reference phases; d. Constructing at least one image of the optical property of the sample at a plurality of positions on the sample; and Wherein the limited number of reference phases comprise i) a reference phase in which one of the at least two different wavelengths has maximum constructive interference and ii) another reference phase in which another one of the at least two different wavelengths has maximum destructive interference. a. Interfering a reference beam with at least one of (i) light scattered from the region of tip/sample interaction and (ii) light incident on the tip/sample interaction region; wherein the reference beam has an adjustable phase; b. At least one of selecting or determining a limited number of reference phases of the reference beam that produce substantially different optical responses for at least two different wavelengths, wherein the limited number of reference phases less than 10; c. Measuring a signal indicative of the optical property of the sample at only the limited number of reference phases; d. Constructing at least one image of the optical property of the sample at a plurality of positions on the sample; and Wherein the limited number of reference phases comprise i) a reference phase in which one of the at least two different wavelengths has maximum constructive interference and ii) another reference phase in which another one of the at least two different wavelengths has maximum destructive interference. <EOS>