title: Testing of steep convex aspheric surface with a Hartmann sensor by using a CGH.
abstract: Most aspheric surfaces have been tested by interferometer with some null correctors. This approach, however, often fails when there are many aspherical terms or test surface is very steep because it is not easy to design the conventional null lens or CGH (Computer Generated Hologram). On the other hand, 3-D profilometer can measure aspheric surfaces without any null correctors; however, it takes some time to measure, which makes it unsuitable for the production line in the factory. In this paper, we apply the Hartmann test to the measurement of steep convex aspheric surfaces of which diameter is about 16 mm. In order to increase the measurement accuracy, we calibrated the test setup using a CGH that simulates the ideal test surface. We demonstrated that the significant amount of error in the test setup could be removed by this calibration process. The test results showed only 2 nm rms WFE (wave front error) difference even though the WFE of test setup was worsened by more than 0.13 mum rms. Since this method makes it possible to measure highly aspheric surface quickly and accurately, it can be used in the production line.
authors.forename: Ho-Soon
authors.initials: HS
authors.lastname: Yang
authors.forename: Jae-Bong
authors.initials: JB
authors.lastname: Song
authors.forename: In-Won
authors.initials: IW
authors.lastname: Lee
authors.forename: Yun-Woo
authors.initials: YW
authors.lastname: Lee