Phase shifting interferometer and method for surface topography measurement

A method of determining a height of a location on a surface, comprising the steps of:

• positioning the surface along an optical axis of a phase shifting interferometer so that said location is optically aligned with an imaging device;
• producing on the imaging device an interference pattern of the surface location using an optically coherent illumination source of wavelength .lambda.;
• operating the interferometer to produce on the imaging device intensity data g.sub.j for the surface location for six frames j each successively shifted from the other by a phase difference of approximately .pi./2, wherein j=0 . . . 5 for said six frames;
• electronically storing the intensity data g.sub.j produced on the imaging device for said six frames;
• calculating a wavefront phase .THETA. for said surface location using the expression ##EQU12## and calculating the height h of the surface location using the expression ##EQU13##

A method of determining a height of a location on a surface, comprising the steps of:

• positioning the surface along an optical axis of a phase shifting interferometer so that said location is optically aligned with an imaging device;
• producing on the imaging device an interference pattern of the surface location using an optically coherent illumination source of wavelength .lambda.;
• operating the interferometer to produce on the imaging device intensity data g.sub.j for the surface location for thirteen flames j each successively shifted from the other by a phase difference of approximately .pi./4, wherein j=0 . . . 12 for said thirteen flames;
• electronically storing the intensity data g.sub.j produced on the imaging device for said thirteen flames;
• calculating a wavefront phase .THETA. for said surface location using the expression ##EQU14## and calculating the height h of the surface location using the expression ##EQU15##