| 摘要 |
<p>A measuring accuracy for interference measuring using a diffractive optical element is enhanced. An interference measuring method comprising converting a light flux to be measured emitted from a light source into an optimum wave-front shape by means of a Null element including a diffractive optical element for projecting onto an object to be inspected, allowing a light flux that has returned to the diffractive optical element after going through the object to be inspected to interfere with a reference light flux, and detecting an interference fringe produced by the interference as the characteristic data of the above object to be inspected. The measuring method involves detecting an interference fringe with a light flux, passing some area of a diffractive optical element and included in a measurement light flux, both restricted and not restricted, and acquiring the above characteristic data free from errors otherwise caused by excessive diffraction light in the above light flux based on each interference fringe thus detected under such conditions.</p> |
