Introduction To Lens Design With Practical Zemax Examples Pdf Download
The paper presents a mathematical tool based on the requirement of tautochronism in each of the diffraction orders of a harmonic kinoform lens, which was used as the basis to develop a method for calculating the lens microstructure. The method provides a limitation of the relative longitudinal chromatism of the lens to a given level. In addition, it allows obtaining the initial parameters necessary for the ray calculation and optimization of an optical system with a harmonic kinoform lens using well-known commercial optical design computer programs.
Introduction To Lens Design With Practical Zemax Examples Pdf Download
We propose a compact catadioptric imaging system based on even aspheric elements to solve some major limitations of conventional panoramic structure, such as field of view, blind spot, resolution, illumination, and less structure is introduced. The design includes a catadioptric front unit that is capable of providing a compression image of a panoramic scene and of relaying high-performance aspheric lenses to a decompression image. It is arranged to project two uncompressed images from two channels on a single sensor. Their optical paths do not interfere with each other, and there is no blind-spot image.
In the modern era, the computational power of computers has become extremely high, and with that, lens design has changed. It is possible to calculate complex results in a very short amount of time, so the technical aspects have improved tremendously.
Facing this reality, I think there are two things that need to be accomplished so that lens design can become a study worth applying. One, the lens designer must be able to systemize their process on why and how a particular lens was designed that way. And two, since lens design requires many difficult design decisions, there is a great benefit in knowing the theory to the process. There are a lot of documents on lens design but very few with the scope of presenting the theory with the usefulness in mind.
Learning high-end lens design starts with mastering low-end lens design. But applying textbook material without the optical design software is difficult. On the other hand, just diving into learning the software can cause a disconnect in the optics theory and the lens design process. I see it all the time. You get really good at using the software, without learning the underlying theory.
The achromatic doublet is a useful lens system because it corrects chromatic aberrations. Actually, we see the doublet in multi-lens systems if we break them down. The important parameters for an achromatic doublet are chromatic aberration, spherical aberration, and Coma, so we will explore them in detail with real-world examples.
I realize that most of you reading this has a concept of lens power, but I want to take the time here to point out that thinking in terms of curvature is really useful in lens design, especially when dealing with aberrations and tolerances. However, at the same time, in a diagram it is much easier to visualize a lens when it is written in radius rather than curvature, due to its much familiar units. Oh the irony!
The six examples above are single lenses, but we use them throughout our lens design process, deciding which lens to use when, in each situation. The conceptual knowledge of principal planes for each lens type is important when setting up our optical system.
However, the objective (pun intended) for optimizing the telescope objective lens design is not to correct the above three aberrations, but it is to balance them to certain criteria. This is an important concept throughout optical lens design with aberrations, the goal is most often not to completely correct all the aberrations in the system, but to keep certain aberrations at designated values. This technique can be seen in many lens designs, most notably the zoom lens design, where each group is kept at a certain aberration to balance with the rest of the system.
If we use cemented lenses intelligently, we can control the higher order aberrations. This is a common practice in many lens designs. At the same time, using cemented lenses is not trivial to express, and also not quantifiable in an equation or a theorem. This choosing of cemented lenses is the very reason why lens design itself is as difficult as it is, but a good lens design cannot be achieved without proper knowledge of this subject. The irony.
The giants of lens design did extensive research on this topic, but there is still no definitive answer, which makes lens design all that more difficult, and to me, all that more attractive. Testing multiple glass types with each other and comparing our answers with the research of the giants can help us immensely with our craft.
We got deep into the process of lens design with the telescope objective, while looking at the key aberrations. This already gives us a leg up on what to look for in the lens system overall, and the effects of each surface going forward.
Just like that, we can now qualitatively and conceptually dissect the lens and figure out the expected performance without opening any software. This prevents blindly optimizing a non-winning design concept, by tackling lens design without knowledge and just the software.
The triplet at its simplest form does not take thick lenses into account, and can be designed with thin lenses. This allows for lens bending that is sufficiently correct, and the lack of cemented surfaces make the triplet a very good tool for learning lens design.
Looking at the cross sectional diagram and the ray diagram, using our pattern recognition and intuition as human beings can be a very powerful lens design process. Optimization with a computer is also powerful, but in a different way.
Glass. The biggest choice in lens design. Even for a relatively simple lens like the telescope objective, we needed to choose the glass carefully. For a triplet, with just one more lens, it becomes critical.
The Petzval sum:If we can make the Petzval sum small we can design a lens that has a larger field of view, but since each lens power increases, it is difficult to design a large aperture lens. The amount of aperture we can afford depends on the index of refraction of the glass. A high index glass allows for larger aperture, because the spherical aberrations are smaller due to the larger radius of curvature with respect to the lens power. On the other hand, a large aperture lens has shallower depth of field, so the field curvature (and hence the Petzval sum) must be small. If the field of view is small, the Petzval sum can be large, and larger apertures are possible.
From the symmetry of the system, the lateral chromatic aberration, and the distortion (we will assume is good enough for now due to the symmetry, and is corrected enough at this point to be able to go forward with the lens design.
In this case the only thing we can do is to go back to Step 2 and rethink the target aberrations we set earlier, or go back to Step I and perhaps choose better (read: expensive) glass and start over. Some lens designers like to start over often, while others like to iterate with trial and error at an intermediary step, and both approaches are correct and incorrect. Both the skill of being able to leave a lens design behind and the skill of persisting with a lens design are needed.
I want to make two comparisons of our lens design with the classic Taylor triplet from 1893 (GB 22,607). The first is a comparison of the 3rd order aberrations with our spreadsheet, and the second is a comparison with Zemax. 350c69d7ab