Tolerance analysis of misalignment in an optical system using Shack–Hartmann wavefront sensor: experimental study
01 Jul 2015-Optical Engineering (International Society for Optics and Photonics)-Vol. 54, Iss: 7, pp 075104-075104
TL;DR: In this article, the wavefront aberrations induced by misalignments due to decentration and tilt of an optical component in an optical measurement system are presented and the results are compared with experimental values.
Abstract: The wavefront aberrations induced by misalignments due to decentration and tilt of an optical component in an optical measurement system are presented. A Shack–Hartmann wavefront sensor is used to measure various aberrations caused due to the shifting of the axis and tilt of a lens in the path of an optical wavefront. One of the lenses in an optical system is decentered in the transverse direction and is tilted by using a rotational stage. For each step, wavefront data have been taken and data were analyzed up to the fourth order consisting of 14 Zernike terms along with peak-to-valley and root mean square values. Theoretical simulations using ray tracing have been carried out and compared with experimental values. The results are presented along with the discussion on tolerance limits for both decentration and tilt.
Citations
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TL;DR: An OSA taskforce was formed at the 1999 topical meeting on vision science and its applications and charged with developing consensus recommendations on definitions, conventions, and standards for reporting of optical aberrations of human eyes.
Abstract: In response to a perceived need in the vision community, an OSA taskforce was formed at the 1999 topical meeting on vision science and its applications (VSIA-99) and charged with developing consensus recommendations on definitions, conventions, and standards for reporting of optical aberrations of human eyes. Progress reports were presented at the 1999 OSA annual meeting and at VSIA-2000 by the chairs of three taskforce subcommittees on (1) reference axes, (2) describing functions, and (3) model eyes.
49 citations
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TL;DR: This paper uses a hybrid optical simulation model that comprises virtual and identified component positions that enables prediction of the future wavefront at the detector plane and therefore allows for taking corrective measures accordingly during the assembly process if a user-defined tolerance on the wavefront error is violated.
Abstract: Alignment of optical components is crucial for the assembly of optical systems to ensure their full functionality. In this paper we present a novel predictor-corrector framework for the sequential assembly of serial optical systems. Therein, we use a hybrid optical simulation model that comprises virtual and identified component positions. The hybrid model is constantly adapted throughout the assembly process with the help of nonlinear identification techniques and wavefront measurements. This enables prediction of the future wavefront at the detector plane and therefore allows for taking corrective measures accordingly during the assembly process if a user-defined tolerance on the wavefront error is violated. We present a novel notation for the so-called hybrid model and outline the work flow of the presented predictor-corrector framework. A beam expander is assembled as demonstrator for experimental verification of the framework. The optical setup consists of a laser, two bi-convex spherical lenses each mounted to a five degree-of-freedom stage to misalign and correct components, and a Shack-Hartmann sensor for wavefront measurements.
6 citations
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TL;DR: The proposed sensitivity optimization method can homogenize image performance for the same field under different tolerance values and improves the product yield rate by 15 to 17% compared with a traditional optimization method.
Abstract: During the production of a lens system, the assembling and manufacturing tolerances must be accurately controlled to ensure production efficiency. Thus, it is important to analyze and optimize the tolerance sensitivity of the lens system during the optical design phase to reduce optical performance degradation. We proposed an approach for appropriately controlling the tolerance sensitivity of a lens system. The proposed sensitivity optimization method can homogenize image performance for the same field under different tolerance values. Based on the results, we show that the implementation of the proposed method sharply reduces sensitivity and, consequently, improves the product yield rate by 15 to 17% compared with a traditional optimization method. As a practical example, a 40-megapixel f1.8 mobile phone camera lens design and optimization process was performed in our study. Our preliminary experimental results confirm that the proposed method is effective to reduce the optical sensitivity of the camera lens.
References
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TL;DR: In response to a perceived need in the vision community, an OSA taskforce was formed at the 1999 topical meeting on vision science and its applications (VSIA-99) and charged with developing consensus recommendations on definitions, conventions, and standards for reporting of optical aberrations of human eyes as discussed by the authors.
Abstract: In response to a perceived need in the vision community, an OSA taskforce was formed at the 1999 topical meeting on vision science and its applications (VSIA-99) and charged with developing consensus recommendations on definitions, conventions, and standards for reporting of optical aberrations of human eyes. Progress reports were presented at the 1999 OSA annual meeting and at VSIA-2000 by the chairs of three taskforce subcommittees on (1) reference axes, (2) describing functions, and (3) model eyes.
749 citations
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TL;DR: Enhanced images of satellites are enhanced by inserting a beam splitter in collimated space behind the eyepiece and placing a plate with holes in it at the image of the pupil, which captures a snapshot of the atmospheric aberrations rather than to average over time.
Abstract: developed out of a need to solve a problem. The problem was posed, in the late 1960s, to the Optical Sciences Center (OSC) at the University of Arizona by the US Air Force. They wanted to improve the images of satellites taken from earth. The earth's atmosphere limits the image quality and exposure time of stars and satellites taken with telescopes over 5 inches in diameter at low altitudes and 10 to 12 inches in diameter at high altitudes. Dr. Aden Mienel was director of the OSC at that time. He came up with the idea of enhancing images of satellites by measuring the Optical Transfer Function (OTF) of the atmosphere and dividing the OTF of the image by the OTF of the atmosphere. The trick was to measure the OTF of the atmosphere at the same time the image was taken and to control the exposure time so as to capture a snapshot of the atmospheric aberrations rather than to average over time. The measured wavefront error in the atmosphere should not change more than /10 over the exposure time. The exposure time for a low earth orbit satellite imaged from a mountaintop was determined to be about 1/60 second. Mienel was an astronomer and had used the standard Hartmann test (Fig 1), where large wooden or cardboard panels were placed over the aperture of a large telescope. The panels had an array of holes that would allow pencils of rays from stars to be traced through the telescope system. A photographic plate was placed inside and outside of focus, with a sufficient separation, so the pencil of rays would be separated from each other. Each hole in the panel would produce its own blurry image of the star. By taking two images a known distance apart and measuring the centroid of the images, one can trace the rays through the focal plane. Hartmann used these ray traces to calculate figures of merit for large telescopes. The data can also be used to make ray intercept curves (H'-tan U'). When Mienel could not cover the aperture while taking an image of the satellite, he came up with the idea of inserting a beam splitter in collimated space behind the eyepiece and placing a plate with holes in it at the image of the pupil. Each hole would pass a pencil of rays to a vidicon tube (this was before …
717 citations
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TL;DR: Contrary to the traditional understanding, the classical least-squares method of determining the Zernike coefficients from a sampled wave front with measurement noise has been found numerically stable.
Abstract: Several low-order Zernike modes are photographed for visualization. These polynomials are extended to include both circular and annular pupils through a Gram-Schmidt orthogonalization procedure. Contrary to the traditional understanding, the classical least-squares method of determining the Zernike coefficients from a sampled wave front with measurement noise has been found numerically stable. Furthermore, numerical analysis indicates that the so-called Gram-Schmidt method and the least-squares method give practically identical results. An alternate method using the orthogonal property of the polynomials to determine their coefficients is also discussed.
399 citations
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TL;DR: In this article, the vertical distribution of atmospheric optical turbulence above large telescopes is determined from time-averaged spatial cross-correlations of local wavefront slopes for Shack-Hartmann observations of binary stars.
Abstract: This paper discusses the use of Shack–Hartmann wavefront sensors to determine the vertical distribution of atmospheric optical turbulence above large telescopes. It is demonstrated that the turbulence altitude profile can be recovered reliably from time-averaged spatial cross-correlations of the local wavefront slopes for Shack–Hartmann observations of binary stars. The method, which is referred to as SLODAR, is analogous to the well known SCIDAR scintillation profiling technique, and a calibration against contemporaneous SCIDAR observations is shown. Hardware requirements are simplified relative to the scintillation method, and the number of suitable target objects is larger. The implementation of a Shack–Hartmann based turbulence monitor for use at the William Herschel Telescope is described. The system will be used to optimize adaptive optical observations at the telescope and to characterize anisoplanatic variations of the corrected point spread function.
247 citations
Book•
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01 Jul 1991
TL;DR: In this paper, the authors provide a clear, concise, and consistent exposition of what aberrations are, how they arise in optical imaging systems, and how they affect the quality of images formed by them.
Abstract: This book provides a clear, concise, and consistent exposition of what aberrations are, how they arise in optical imaging systems, and how they affect the quality of images formed by them. The emphasis of the book is on physical insight, problem solving, and numerical results, and the text is intended for engineers and scientists who have a need and a desire for a deeper and better understanding of aberrations and Their role in optical imaging and wave propagation.
178 citations