Method and apparatus for surface profilometry

A method for determining the surface profile of an object, comprising the steps of:

• directing at said object an incident beam of light having a sinusoidally varying intensity pattern;
• modulating the phase of the sinusoidal pattern of said incident beam;
• receiving and storing a deformed grating image of the object for a number of different modulated phases of said input beam;
• receiving and storing an image of a reference plane for said number of different modulated phases of said input beam;
• combining image intensity values at each point of the deformed grating image of the object to obtain an object phase at each such point;
• combining image intensity values at each point of the image of the reference plane to obtain a reference plane phase at each such point;
• and
• determining the object height at each point from the object phase and reference plane phase for each such point.

Apparatus for determining the surface profile of an object, comprising:

• means for directing at said object an incident beam of light having a sinusoidally varying intensity pattern;
• means for modulating the phase of the sinusoidal intensity pattern of said incident beam;
• a detector for receiving a deformed grating image of the object for a number of different modulated phases of said incident beam;
• and
• means for determining, for points on the surface of the object, the height at each said point with respect to a reference plane, said means being operative to combine image intensity values, for said different modulated phases of the incident beam, at a detector position corresponding to a respective point of the object.