Light interference measurement method using computer-generated hologram, and interferometer using this method

An interferometer in which light from a coherent light source is split into two light beams, a reference surface is irradiated with a first light beam of these light beams to obtain reflected light from this reference surface as reference light, the sample surface of an object is irradiated with a second light beam via a computer-generated hologram to obtain reflected light from this sample surface as object light, and the surface shape of said sample surface is measured on the basis of interference fringes obtained by light wave interference between said reference light and said object light, the interferometer comprising:

• a retaining member which holds said computer-generated hologram so that this computer-generated hologram has a predetermined inclination with respect to an incident light beam, and so that this computer-generated hologram is disposed in a predetermined position;
• a substrate that holds said object;
• one or more targets formed on both said retaining member and said object so that the positions of respective targets in a plane perpendicular to the optical axis coincide with each other when the adjustment of the alignment of said computer-generated hologram and said object is performed;
• and
• a spacer interposed between said retaining member and said object or said substrate,
• said substrate being held on a position adjustment member that adjusts the relative positions of said retaining member and said object in two perpendicular axial directions in said plane and in the direction of rotation about said optical axis,
• the interferometer further comprising:
• switching apparatus for performing switching so that the light beam used for the adjustment of the alignment is perpendicularly incident on said computer-generated hologram during the adjustment of said alignment, and so that said second light beam is incident on said computer-generated hologram at an inclined angle during the measurement of the surface shape of said sample surface;
• and
• imaging apparatus for obtaining information that is used to judge whether or not the positions of the respective targets of both said retaining member and said object coincide with each other in said plane.

An interferometer in which light from a coherent light source is split into two light beams, a reference surface is irradiated with a first light beam of these light beams to obtain reflected light from this reference surface as reference light, the sample surface of an object is irradiated with a second light beam via a computer-generated hologram to obtain reflected light from this sample surface as object light, and the surface shape of said sample surface is measured on the basis of interference fringes obtained by light wave interference between said reference light and said object light, the interferometer comprising:

• a retaining member which holds said computer-generated hologram so that this computer-generated hologram has a predetermined inclination with respect to an incident light beam, and so that this computer-generated hologram is disposed in a predetermined position;
• a substrate that holds said object;
• and
• a spacer interposed between said retaining member and said object or said substrate,
• wherein said retaining member and said spacer comprise positioning engaging parts that can engage with each other, and the relative positioning of said computer-generated hologram and said sample surface can be performed by causing these positioning engaging parts to engage with each other.