Introduction to lens design with practical zemax examples pdf. If the original aperture is in the middle, relocating the aperture to behind the lens will not result in the same optical performance. On a typical slr lens you can see that even at minimum aperture, one could make the hole smaller. Number under the divider ismall number large aperture e. This is how the focal length and aperture affected the composition. A variable aperture lens means that it will shoot at f3. This was critical in the days of using an external handheld meter. Wedding books, baby books, recipe books whatever your project the a4 landscape book offers you versatility and value everytime. It adds impressive building blocks to the foundation established by a.
As you can see here, the blades open and closeas i increase and decrease the aperture. The achromatic condenser usually contains four lens elements and has a numerical aperture ranging from 0. Aperture, shutter speed, and film sensitivity are linked. There are also many useful figures to help visualize the main issuesconsiderations of lens design. The basics from that linked discussion are that the index of refraction of the lens material will affect the maximum aperture you can achieve, so for pure glass that has an index of refraction of 1. Click on document introduction to lens design with practical zemax examples pdf. In a fixed aperture zoom, only the elements behind the diaphragm move around to do the zooming. However, the most confusing part for any new photographer is. If you shoot at say f8, you will get the same dof at the same focal length whether the lens is f2. The reader is urged to follow the logic of these examples and be sure that he understands what is happening, noticing particularly how each available degree of freedom is used to control one aberration. Design of wide angle and large aperture optical system. This versatile lens would have won the title of the best zoom allaround lenses, but for the maximum aperture. Design of highperformance adaptive objective lens with. By definition, aperture is an opening in the lens through which light enters your camera.
Camera lenses have been discussed in a large number of books and articles. Sep 26, 2015 so if you work with a 50mm lens at f2, the width of the aperture hole in the lens is 25mm, because we take the number 50 and divide it by 2. Camera aperture, f number, and depth of field explained. This book is both a primer for professionals called upon to design optical systems and. With a constant or fixed aperture lens, the aperture functions independently of the lens focal length. Fundamental optical formulae book chapter iopscience. Now how does that chief ray pass undeviated through the center of the lens or aperture. A tutorial for designing fundamental imaging systems. Lens design fundamentals edition 2 by rudolf kingslake.
Byrnes,1,2, alan lenef,3 francesco aieta,1,4 and federico capasso1,5 1 harvard john a. Even so, youd be advised to avoid the smallest apertures on your lenses. A constant aperture lens maintains the set aperture whatever the focal length. The lens aperture is usually specified as an fnumber, the ratio of focal length to effective aperture diameter. Different versions of the class of lenses are presented and can be used to form a practical startingpoint base for many types of lens.
A lens typically has a set of marked fstops that the fnumber can be set to. Modern lens design mcgrawhill professional engineering, warren j. It is shown in most basic books on optics see references listed at end of this. The geometric optics theory of zoom lens design is described in many books and papers such as refs. Home books introduction to lens design zoom lenses. The fnumber is the ratio of the lens focal length f to the clear aperture diameter of the lens. Its function is to bend rays of light by a physical process called. Design for near and distant viewing distances is essentially identical. We have not included any specific design examples of lenses for largeformat cameras. Conrady in applied optics and optical design and rudolph kingslake in lens design. You can see how a new design can evolve around a simple starting point idea or structure.
Coma of a lens with the stop in contact varies linearly with the. The fnumber of an optical system is the ratio of the systems focal length to the diameter of the. Understanding aperture in photography adventurous lens. This is a number that expresses the ability of a lens to resolve fine detail in an object being observed. Chapter 16 handbook of optics photonics research group. There is actually a fairly fundamental difference in the design. The 8 airtoglass surfaces, unless effectively coated, reduce contrast and introduce flaring and ghosting. Paulson school of engineering and applied sciences, cambridge, massachusetts 028, usa 2 charles stark draper laboratory, cambridge.
Generally, variable aperture lenses are less expensive. The combination of wide aperture and long focal length means there isnt much depth of field. A classic book by cox22 includes an analysis of 300 lens patent examples. The zemax code in the book is a bit dated by now but most users should be able to still use it for newer editions of the software. Optimal lens design and use in laserscanning microscopy. The diaphragm the part that forms the aperture in almost any lens is somewhere around the middle of the lens. Lens design fundamentals, second edition, is the most comprehensive treatise to be published on the subject of lens design. I used a focal length of 150mm and an aperture of f2.
Designing large, highefficiency, highnumericalaperture, transmissive metalenses for visible light steven j. Describe the fnumber and numerical aperture for a lens and explain how they control. This hole is created by a series of blades inside the lens that make up an iris that can move to open or close. Dec 30, 2014 the symmetrical design places the aperture represented by the vertical line between the two groups of elements, allowing for wider apertures than other designs. Lens design optical sciences and applications of light. It is derived by a mathematical formula n sine u and is related to the angular aperture of the lens and the index of refraction of the medium found between the lens and the specimen. The location of the aperture is a critical part of the design changing the location by many millimeters will alter the performance. This term is also referred to as the speed of the lens. For applications, it is most commonly expressed as. The basic lens design optimization program includes modules for ray tracing, aberration. Large opening have lower fnumbers and small opening have higher fnumbers. At 18mm it is wide enough to capture family photos, group shots and even landscape though the effective focal length becomes 28. Minimum aperture is typically f22 or smaller larger numerically. Zoom lenses chapter 18 introduction to lens design.
A practical guide to lens design focuses on the very detailed practical process of lens design. Reproduction of significant portions of ti information in ti data books or data sheets is permissible only. Sun is a spie senior member and serves in several spie programs and committees. A large part of this book is devoted to a study of possible design procedures for various types of lens or mirror systems, with fully worked examples of each. Smaller aperture lens collects less light, note blocked rays. A comprehensive guide to camera lens design and zeiss. The choice of beam size, expansion ratio and lens design will determine. Penelope przekop 2008 aberrations fiction introduction to lens design. A lower fnumber denotes a greater aperture opening which allows more light to reach the film or image sensor. You will have to know some mathematics but if you want to try your hand at some lens design then this is a good place to get started.
Physics plays a role in answering your question and that information is out there. The widest focal length of this lens has an f4 aperture available, while the telephoto end opens only to a 1stopnarrower f5. And this is all human based lens design where the fun part, and most important part, comes before we do any computer optimization. Its the maximum aperture the lens can open up for each end of the zoom range. Numerical aperture na, a measure of the acceptance angle of a fiber, is a dimensionless quantity. Every step from setup specifications to finalizing the design for production is discussed in a straight forward, tangible way. The aperture stop is an important element in most optical designs. Basic principles about designing paraxial systems are introduced. Aug 02, 2010 generally, they, constant aperture lenses, are just better built to be quite honest. Aperture in f number ratio of used diameter and focal lens. A number that tells how wide the aperture isis called the fstop. Understanding aperture and f numbers lui brandstrup medium. In a 0% offset design light engine, the center of the dmd is aligned exactly with the optical axis of.
A simple lens is a polished piece of glass with concave or convex surfaces. Enables faster shutter speeds able to stop subject and camera motion in lower light levels potentially at lower iso settings for less blur and less noise. Images are acquired by raster scanning a focused beam at constant speed over. The higher the number, like f16, the tighterthe aperture blades are, restricting. Get brushed up on your mathematics before you start. Your camera is a small, portable darkness, and the lens is its window on the world. There are several good books on optics, but most texts give short coverage. The lower the fnumber, the faster the lens and the higher the fnumber, the slower the lens. Dec 30, 2014 a lens aperture is the hole that is used to control how much light enters the camera. Every system includes one aspheric surface and free positioned aperture stop. Dec 23, 2015 you have just identified what is called a variable aperture lens. Enables faster shutter speeds able to stop subject and camera motion in lower light levels potentially at lower iso settings for.
A tutorial for designing fundamental imaging systems koichi taniguchi opti 521 distance learning college of optical science university of arizona november 2009,, abstract this tutorial shows what to do when we design optomechanical system for imaging system. The lens collects light from the outside universe and focusses it onto the film. Jan 01, 2006 this title is directed primarily towards health care professionals outside of the united states. Designing large, highefficiency, highnumerical aperture. Introduction to lens design by jose sasian september 2019. Paulson school of engineering and applied sciences, cambridge, massachusetts 028, usa 2 charles stark draper laboratory, cambridge, massachusetts 029, usa. The barrel of the lens does not extend or retract when the focal length changes. A slightly different viewpoint may help to understand the two types of lenses, metering. The book not only covers theory of lens design but the author also delves into the math using practical examples. In optics, an aperture is a hole or an opening through which light travels. This is a feature of the more expensive lenses as it takes a lot of research, development to keep an aperture constant through a focal change range. The maximum aperture opening tends to be of most interest and is always included when describing a lens.
What are main advantages of lenses with constant aperture. Camera aperture, f number, and depth of field explained i. A large aperture will also show flaws in design and build quality in the form of chromatic aberration, unsharpness, vignetting etc that a f5. This book holds a unique place in the optics literature. This condenser design is useful for both routine and critical laboratory analysis with dry or oil immersion objectives and also for black and white or. This book is superb because it lays out different lens design forms suitable for different fnumber and fov. The percival philosophy is similar to that used in modern spectacle lens design. The specifications for a given lens typically include the maximum and minimum aperture sizes, for example, f 1. Dof is primarily controlled by the object distance along with the lens aperture diameter.
Although i have taken a great deal of effort to assure accuracy, the user of any of. In most areas of optics, and especially in microscopy, the numerical aperture of an optical system such as an objective lens is defined by. To prevent this, manufacturers limit minimum aperture according to the lens design. Goes through the design of the tessar, double gauss etc. These have been widely used as phase detection auto focus af methods within conventional digital singlelens reflex dslr cameras. To correct the coma of a single lens with aperture stop in contact, let us look a little more closely at it. Note that in addition to changing the focusing behavior, modifying the lenssensor distance also has the sidee. We exploit the phenomenon of total internal reflection when designing light. In a variable aperture zoom, elements both behind and ahead of the aperture move around to do the zooming. The value of this determinant is invariant or constant when evaluated at any. If other things were equal, like iq and the ability to see through the lens brightness, most wouldnt care as landscape is generally done with smaller apertures rather than wide open. Highend lenses will have a constant aperture, such as f2. Design examples of several widely used modern lenses are provided. The reproduction ratio of this lens is a diminutive 0.