Aberration analysis may not be part of the spec, but it will probably be useful in the design process, especially in selecting variables for optimization. Optimization - Once you define a set of variables parameters such as curvature, thickness, index of refraction, etc.
Numerical methods are used to alter the variables in systematic ways that attempt to minimize the error function while honoring all constraints. Sometimes it goes smoothly, more often it doesn't, so changes are necessary, injecting designer guidance to resolve conflicts though some software is pretty smart about many types of optimization problems, no program is yet fully automatic, if only because some requirements and esthetic judgments may remain in the designer's head and not in the error function.
Final analysis - After optimizing the lens, you need to see if it is actually doing what the original spec says it should do optimization error functions may not correlate perfectly with specifications such as MTF or encircled energy. If it's not quite there, you may have to go back for some more optimization perhaps adding variables or changing constraints. You may even have to find a different starting point in some cases. Prepare for Fabrication - If the lens design meets its requirements, you will still have more work to do to prepare for fabrication.
See "The Rest of the Story" below for a bit more on this subject. Model, analyze, optimize, and provide fabrication support for the development of optical systems with CODE V optical design software. What does this leave out? A lot of the "hard parts" of the design process, in fact. Incomplete or changing specifications. Conflicting requirements.
Dead-end solution attempts. Unrealistic schedules. Computer crashes. Nobody said it was easy! The fabrication defect made spherical aberration temporarily famous or perhaps infamous? In geometrical terms, the concept of aberration is pretty simple. Rays from a zero-dimension point object like a distant star imaged through a perfect lens will all focus to a single zero-dimension image point in reality, diffraction effects result in a small but finite size even for aberration-free imaging.
If these rays go anywhere else, that is aberration. Aberration can be expressed in various ways, most of which start out by tracing a number of rays through the lens to see where they go.
The ray distribution can be plotted as a scatter plot we call this a spot diagram , or cross-sections of ray position data can be plotted ray trace or "rim ray" curves. To those trained in the art, the shapes and sizes of the resulting patterns can tell things about the amount and forms of aberrations that are present, and with this information, you can plan to correct or reduce the aberrations in various ways.
Aberration theory breaks down aberration into components terms of polynomials, actually , and can even assign "blame" for aberration to specific surfaces in the lens a strongly curved or badly made surface can contribute major amounts of aberration, but surface contribution information at least gives a clue how to proceed.
Spherical aberration SA is perhaps the simplest to understand, since it depends only on distance from the optical axis. Most optical surfaces are sections of spheres, since these are the easiest surface shapes to make. For a simple spherical-surface lens or mirror, rays at different heights on the surface are not bent to the same degree, so they focus at slightly different distances along the axis; this is SA.
With simple lenses, you can reduce SA by choosing the right lens form " lens bending ", as we say in the trade. With mirrors as in the HST , you can correct it by making the mirror a slightly non-spherical conic section but you have to create the CORRECT conic shape, which was HST's problem -- they built it perfectly against the wrong test standard! Of course there are OTHER aberrations too, and their interactions may prevent you from making a correction you would like the old lump-in-the-rug effect -- correct in one place and it pops up in another.
This can make lens design a bit challenging and leads to the next subject of optimization. The Hubble also illustrates the GOOD thing about aberrations: if you know what they are in detail, you can often correct them especially with a big enough budget! If the optics are bending the light in the wrong way, elements can be reshaped or other elements added to cancel out the aberration, similar to the way that glasses correct myopic vision although myopia is not exactly an aberration -- the myopic eye actually has the wrong focal length, so an additional lens is needed to allow it to focus on the retina.
Optimization is such an important subject in optical design that we need to say more about it, even though it was briefly described under How to Design a Lens. Remember that the goal of optimization is to take a starting lens of some sort and change it to improve its performance the starting lens should have a suitable number of optical surfaces of suitable types, since optimization can change only the values of the parameters, not the number or types of surfaces.
Since optics is very precise distances of micrometers can make a big difference , we need to closely determine the values of all our variables at each step of the optimization.
Let's consider local optimization first. What does "local" mean? If you have a lens model, an error function is something that correlates with its image performance, like spot size or RMS wavefront error -- smaller is better.
Together with electrical and mechanical engineers, they work on the overall design of systems using optical components. In creating a new product using optical technology, optical engineers go through a multistep engineering process. First, they study the application or problem to understand it thoroughly.
Then they brainstorm to come up with possible solutions to the problem. They work out all of the details and create a computer-generated model or test unit. This model or unit is tested, and any required revisions to the design are made and tested again. This process continues until the design proves satisfactory. The design is then sent to production, and a product is manufactured. The process is completed with marketing of the product. For some products, an engineer may perform all of these steps except marketing.
Other products require a team of engineers and may include other professionals such as industrial designers, technologists, and technicians. Some optical engineers specialize in lasers and fiber optics.
These engineers, also known as fiber optics engineers and laser and fiber optics engineers, design, develop, modify, and build equipment and components that utilize laser and fiber optic technology. Lasers are used to produce extremely powerful beams of light that can be transmitted through fiber optics, which are hair-like strands of plastic-coated glass fibers.
Using this technology, lasers can cut through material as hard as a diamond, travel over long distances without any loss of power, and detect extremely small movements. Lasers also can be used to record, store, and transmit information. For example, lasers are used in surgical procedures and medical diagnostic equipment. They are used in manufacturing industries to align, mark, and cut through both metals and plastics.
Military applications such as navigational systems and ballistic and weapon systems use laser technology. Fiber optics engineers may specialize and work within a specific area of fiber optic technology. They may work with fiber optic imaging, which involves using fiber optics to transmit light or images.
These engineers also use fiber optics to rotate, enlarge, shrink, and enhance images. Available technologies and scientific breakthroughs regarding the principles of light advance all of the time. Engineers keep up-to-date on the latest innovations by reading scientific journals and attending seminars on a regular basis. A master's degree is typically the minimum requirement to become an optical engineer at a manufacturing plant or research and development lab.
An advanced degree program in physics, mechanical engineering , or electrical engineering can prepare a person for a career in the field. In order to hold a supervisory position or conduct individual research, an optics PhD and several years of postdoctoral research training may be needed.
Professionals who gain practical experience can obtain certification or licensure by taking official written exams. These devices serve many industries, including the aerospace, medical, energy, and manufacturing sectors. In addition to coursework in engineering and design, degree programs in the field include classes in mathematics, life sciences, and physical sciences.
Physics Physics is a field that keeps changing as discoveries are made. This means that the field asks at least as many questions as it answers. Students of physics degree programs study matter and energy. They learn about the relationships between the measurable quantities in the universe, which include velocity, electric field, and kinetic energy.
Robotics Engineering Robotics engineering is focused on designing robots and robotic systems than can perform duties that humans are either unable or prefer not to perform. Robotics Technology Degree programs in robotics technology prepare students to work with engineers who design robots and robotic systems than can perform duties that humans are either unable or prefer not to perform.
Applying math and science to design devices like telescopes, camera, flat-screen displays, and medical lasers and testing is complex work.
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