Large rectangular plane mirrors are widely used in high-power laser systems and synchrotron radiation sources, their surface precision affecting optical system performance. High-precision measurement methods are required to match these mirrors. The oblique incidence absolute measurement technique based on the rotational averaging method is a commonly method for these mirrors. But this method is complex, requires two additional plane mirrors. And it is limited by the angle of incidence, making it impossible to achieve both large aperture and high-resolution measurement simultaneously. Moreover, the method requires disassembling the test mirror during measurement, which significantly complicates the setup and adjustment process. Addressing the aforementioned shortcomings, this paper presents a high-precision measurement method for large rectangular plane mirrors. This method combines subaperture stitching techniques with the absolute measurement approach using the double shear translation method. It divides the test mirror into multiple overlapping subapertures and applies the double shear translation method to conduct absolute measurement on each subaperture region sequentially. Subsequently, employs algorithm to stitch the results together to achieve a complete surface. This method balances large aperture and high-resolution measurement, eliminates the influence of the reference surface. During the measurement process, only translations of the test mirror are required, making setup and adjustment relatively straightforward. Experimental validation of this method has demonstrated its ability to achieve high-precision measurement of rectangular plane mirrors. This paper presents an effective approach for high-precision measurement of large rectangular plane mirrors.
In AR and VR devices, freeform surfaces are widely used to improve system performance. The manufacture of freeform surfaces is limited to the measurement. In order to guide the manufacturing process, we have proposed a real-time interferometric measurement system. In the system, an accurate, automatic and fast description method is needed to describe complex freeform surface. In order to improve this situation, a description method with automatically configurable Gaussian radial basis function (AC-GRBF) has been proposed. The key parameters of AC-GRBF, the number of subapertures N, coefficient A and the base number of GRBFs affect the fitting accuracy and speed, and they are analyzed by numerical simulation in the paper. The analysis in this paper can provide reference for the description method of GRBF, especially AC-GRBF, and the description of complex freeform surfaces in the design.
This paper proposes an interferometry method based on a fixed interferometer structure and locally compensated stitching. The subaperture measurement is completed by applying a double-optical-wedge compensator in the "rugged" area of the surface that cannot be measured. The data of the measured area is stitched to obtain the local surface shape. The calibration of the double-optical-wedge compensator is performed by using a standard mirror. Surface figure error (SFE) of the standard mirror is measured by an interferometer beforehand. Compared with the SFE measured after adding the compensator in the optical path, the phase and aberration of the double-optical-wedge can be obtained. Measured data is processed by the subaperture stitching algorithm. Through the weighted fusion algorithm, the corresponding data values on the overlapping areas are weighted, and different weights are assigned to different areas to make the stitching transition smooth. Based on the principle of interferometry, a double-optical-wedge compensation measurement system is designed and implemented. A simulation model of the measurement experiment is presented, and the validity of the method is verified by simulation.
Computer-generated hologram (CGH) method is a high-precision aspherical surface detection method. CGH produces wavefronts of any shape with extremely high precision and is adopted in null test. Liquid crystal CGH (LC-CGH) is a new type of CGH with short production cycle and low cost. It is a promising alternative to traditional CGH. In this paper, the overall process flow of LC grating preparation is presented. The influences of three process parameters, such as LC solution concentration, spin coating speed and time on the three physical quantities of LC grating diffraction efficiency, LC polymer film thickness and phase delay are studied. Based on the analysis, improvement measures are proposed for the preparation process. The research carried out in this paper has guiding significance for the processing and manufacturing of LC-CGH.
We propose a liquid crystal (LC) hologram fabricated with photoalignment technology, for the measurement of a cylindrical surface. A standard cylindrical surface reflects the incident planar wavefront and generates an interferogram with a planar reference wavefront. Photoalignment azo-dye material is then exposed by the interferogram and aligned with desired orientations, following with depositing LC monomer to generate the designed phase information. After ultra-violet curing, the fabricated LC hologram plate can generate a standard cylindrical wavefront when illuminated with a planar wavefront. The minimal line-width due to the limitation of LC molecules is sub-microns, which is smaller than the limitation in traditional CGH. The systematic design of the measurement is proposed, followed by a demonstration simulation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.