Measuring method and apparatus using attenuated total reflection

A measuring apparatus using attenuated total reflection comprising:

• a measuring unit comprising a thin film layer formed on one of the surfaces of a dielectric block, and a sample holding structure for holding a sample provided on said thin film layer;
• an illuminating means for entering a light beam containing a plurality of wavelengths, and having a sizable cross sectional area, which is generated, and emitted from a light source, into the interface between said dielectric block, and said thin film layer, through said dielectric block, at an angle that satisfies the conditions of total reflection at said interface;
• a wavelength selecting means disposed in the optical path of the collimated light beam totally reflected from said interface, and adapted to select a collimated light beam having a predetermined wavelength from said collimated light beam containing said plurality of wavelengths;
• and
• a two-dimensional optical detecting means for detecting the distribution of optical intensities on the cross section of said collimated light beam selected by said wavelength selecting means.