Interferometers with diffraction on dot aperture for testing of shape errors of precise surfaces

Modern approach to the optical investigation of optical systems of the highest precision is considered. Lack of classical interferometers is the necessity of presence for their schematics the reference optical element, so its accuracy is limited always. However for the testing of optical systems and elements of the best class the devices ensuring accuracy at a level 1/100 - 1/200 λ are necessary. It is on the order more exact than the traditional. As the alternative, the concept of the interferometer with diffracted reference wavefront [point diffraction (PDI) --interferometer] is offered. In this research the schematic of PDI-interferometer with basic front, common for working and observant branches, is developed. The errors are reduced. The flexibility and universality of an interferometer are achieved. The accuracy, simplicity and profitability are increased. The adjusting is simplified.