PPT-SEM Lens Aberration: Astigmatism

Amin Cheraghi Shirazi Jan 2013 CAMTEC Nanofabrication Workshop SEM 2 Lens Aberrations Spherical Aberration Chromatic Aberration Diffraction Astigmatism 3 Spherical Aberration. Aberration: a departure from the paraxial limit.. Paraxial limit: (1) Rays are kept close to the optic axis.. . (2) Small angle approximation (1. st. Order). 5. th. Order. . 3. rd. Order. Alireza Peyman, MD. http://www.drpeyman.ir. One of the troublesome aspects of refractive surgery. What is astigmatism. Regular. Irregular. Regular astigmatism. Presbyopic with the rule in near vision. ‘s law:. n. 1. sin. θ. 1. = n. 2. sin. θ. 2. Refractive index depends on wavelength of light (color). With different refractive indices, colors are . dispersed. Chromatic aberration. To generate a sharp image, light must converge at the same point.. . I don’t get it.. The things we say... OD. - . Oculus Dexter. Right eye. OS. - . Oculus Sinister. Left eye. OU. - . Oculus . Uniter. Both Eyes. The things we say…. Myopia- Nearsighted. Hyperopia - Farsighted. . But not ideal! Maps (and blurs) a very narrow angle range from one object point . Dq. . . . r/L. to one image point. . Depth of field in imaging. . Sometimes a nice effect, sometimes a problem. Additional Professor. Department of Ophthalmology. AIIMS Rishikesh. Acknowledgement. Photographs in this presentation are courtesy of. . . Kanski’s Clinical . Ophthalmology.. 2. Learning Objectives. Inaccurate measurements/data. Dry eyes (as always). Basement membrane dystrophy, …. Irregular astigmatism (. Kconus. and other . ectasia. , . pterygium. , Salzmann, …). Contact lens . warpage. Not taking into account the posterior cornea. . Agrawal. Additional Professor. Department of Ophthalmology. AIIMS, . Rishikesh. Acknowledgement. Photographs in this presentation are courtesy of. . . Kanski’s. . Clinical . Ophthalmology.. The things we say... OD. - . Oculus Dexter. Right eye. OS. - . Oculus Sinister. Left eye. OU. - . Oculus . Uniter. Both Eyes. The things we say…. Myopia- Nearsighted. Hyperopia - Farsighted. Spherical. Fig 1. Fig 2. Fig 3. Fig 4. - Instructions Altomed Limited, 2 Witney Way, Boldon Business Park, Tyne & Wear, England, NE35 9PE. For further assistance or to place orders, please contact customer servi Rodney D. Leavitt, M.D. Mark J. Ma�ett, M.D. Matthew R. Guymon, D.O. 1226 NE 7th Street Grants Pass, OR 97526 Phone: 541-476-6636 Fax: 541-476-6690 Physicians & Surgeons • Ophth 19541 ISSN: 2574 -1241 Comparison of Corneal Topography in Eyes Before and One Month After the Phacoemulsification Procedure Pateras Evangelos 1 * and Armenis J 2 1 Associate Professor, Biomedical Sc GORAKHPUR. . . . Session . : 2020-2021 . . . Presentation on : . Aberrations in image. . . Presented by : Dr. . Prashant. . Shahi. Contents. positions.. Definition:. Diagram:. Diagram:. Diagram:. Diagram:. Ideal situation. Real situation. Diagram:. Photo:. Positive …. aberration. Negative …. aberration. zero …. aberration. Correction:.