An in-focus image of an information-bearing region within and/or on a substance is discriminated from an out-of-focus image so as to reduce errors in image information of the substance by producing a probe beam and a reference beam from a wideband point source, producing antisymmetric spatial properties in the reference beam, converting the probe beam to a beam focused to a line in the region, producing an in-focus return probe beam, and producing antisymmetric spatial properties in the in-focus return probe beam. Then the in-focus return probe beam is spatially filtered and focused to a line image in a detector plane of a detector system. The reference beam is spatially filtered and focus to a line image in the detector plane. A beam from an out-of focus image point is spatially filtered. The line image of the spatially filtered reference beam is interfered with the spatially filtered beam from the out-of-focus image point and the line image of the spatially filtered in-focus return probe beam. A complex amplitude of the spatially filtered in-focus return probe beam is detected as an interference term between line image of the spatially filtered reference beam and the line image of the spatially filtered in-focus return probe beam by means of the detector system. An amplitude of an interference term between the spatially filtered out-of-focus image beam and the line image of the spatially filtered reference beam is thereby substantially reduced, and reduces statistical and systematic errors in data produced by the detector system to represent the image information of the region. The image information is acquired as either one-dimensional or two-dimensional data arrays wherein the elements of the arrays are obtained substantially simultaneously. The substance is scanned to generate images of dimensionalities greater than the one-dimensional or two-dimensional data arrays.
Multiple layer confocal interference microscopy using wavenumber domain reflectometry and background amplitude reduction and compensation