This paper proposes a method to measure hexahedron vertical error based on wavefront interferometer and
collimator. The setup of the measurement system and measurement steps is described. Comparing the vertical
error of the same hexahedral surface adjacent measured by coordinate measurement machine, the validity of the
measurement method is verified. Then not only the verticality error, but also form and shape error data of the
two measured surface can be derived. The verticality error of adjacent surface is measured by the combination
measurement method. Then surface figure error data for the two surfaces is measured by wavefront
interferometer. The form and shape error data of one surface relative to the other can be obtained by added the
verticality error to the surface figure error. This is very important in the part's error correction machining
process. The effectiveness of the processing method has been verified by experiment. This method can achieve
high measurement accuracy of 0.5″ and can be extended to high-precision shape and position errors
measurement for other polyhedral parts.
The radius of curvature (ROC) is one of the most important parameters of sphere optic components. In optic fine grinding process, radius of curvature accuracy requires up to 0.1%. We propose a method based on high precision CNC grinding machine, develop ROC online measurement method for fine grinding optics. This rapid method only takes few measurement points based on spiral route path, attaining enough accuracy and reduce the time cost, furthermore, can greatly reduce the repeated installation error. Analyzing the uncertainty sources that affect to the ROC measurement results, calculates the combined standard uncertainty 32.8 micron. Completed comparison experiments with CMM, the standard deviation of the experiment result are about 18 micron that approaches to CMM results.
Lithography projection objective is one of the most precise optical systems in optical manufacture field. The required accuracy of the asphere in the objective is down to nanometer and sub-nanometer, which is a great challenge for optical fabrication and testing. In this paper, the theories and technologies of sub-nanometer asphere fabrication and testing are studied and developed. Combined the sub-nanometer interference testing method and atom level polishing technologies, sub-nanometer aspheres are realized. Two kinds of testing methods are used for the measurement of the asphere and the difference of the results is less than 1nm (RMS).
Lithography projection objective is one of the most precise optical systems that people ever produced. The required
accuracy of the optical elements including surface’s form, mid-frequency and high-frequency are down to nanometer and
sub-nanometer, which is a great challenge for optical fabrication and testing. Based on the manufacturing of high NA
optical lithography projection objective, the theories and technologies of sub-nanometer optics fabrication and testing are
studied and developed. The typical and statistic results of high NA optical lithography objective elements are presented
and an optical fabrication and testing line for lithography optics is established.
Radius of curvature (ROC) is one of the key parameters for optical elements and it is especially important for high quality optical system, in which the computer-aided integration is wildly used. ROC is one of the main input parameters and its measurement accuracy is a premise for high quality integration. In this paper, sub-micron ROC measurements are realized in a vertical interference workstation based on Fizeau interferometer. The error sources and uncertainty of the system are analyzed. Experiment results based on samples with difference ROC are presented and in accordance with the analysis. At last, a ROC comparing tests between the system and a three-coordinates measuring machine (CMM) are performed on a SiC ball to certify the workstation’s measurement uncertainty.
Paraboloid is a special asphere and is widely used in optical system. This paper is focused on the Paraboloid testing error analysis and synthesis in practical. A paraboloid from ZYGO is tested using three different methods which are computer generated hologram (CGH), small ball and multi-zone stitching metrology method. The three methods are realized in a fine controlled lab utilizing ZYGO FIZEAU interferometer and the test results are compared and analyzed. Error synthesis is also performed and the uncertainty of the tests is less than 4.5nm.
In high precise surface testing, temperature stability and uniformity are of paramount importance to the high accuracy of
test results. Micro-temperature variation and temperature gradients not only cause the change of the air refractive index
and lead to the optical path variation in interferometer cavity, but also result in deformation of the tested surface itself,
which always brings about errors to the test results. Temperature effects on the interferometer cavity and the tested
surface are analyzed from the axial and radial directions in this letter. Temperature model of the interferometer cavity
and the tested lens are established and quantitative calculations and diagram of test results versus temperature and lens
dimension are provided. It shows that temperature gradients effect increase with the length of the interferometer and the
dimension of the tested lens. The interferometer cavity is mainly affected by radial temperature gradients while the tested
lens is mainly affected by the axial temperature gradients.
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