Apparatus for interferometrically measuring the physical properties of test object

An apparatus for interferometrically measuring the physical properties of a test object having at least two surfaces including a first surface making a portion of incident light reflected and another portion of the light transmitted and a second surface making at least a portion of incident light reflected, said test object being to permit the propagation of the light between said first and second surfaces, which comprises:

• illumination means for illuminating said test object with broadband light so as to form first and second wave fronts having therebetween an optical path difference corresponding to the optical path length between said first and second surfaces of said test object,
• interference fringe forming means for receiving said first and second wave fronts, splitting said first wave front into third and fourth wave fronts tilted to each other and said second wave front into fifth and sixth wave fronts tilted to each other and making said third wave front intersect said fourth and sixth wave fronts and further said fifth wave front intersect said fourth and sixth wave fronts so as to form a broadband light interference fringe,
• image forming means for forming an image of said test object in the position where said broadband light interference fringe is formed by said interference fringe forming means, and
• viewing means for allowing to view the image of said test object and said broadband light interference fringe simultaneously.