Technology & Philosophy

vol.4

The Hidden yet Leading Role of Mechanical Design
(AF-S NIKKOR 24-70mm f/2.8E ED VR)

  • Vol. 1
  • Vol. 2

What is mechanical design?

Optical DesignHiroki Harada

Last time, we talked primarily about the thoughts of optical designers. To turn optical designs into actual products, a project team is created. In fact, as a part of these teams, mechanical designers play a very large role.

Hiroki Harada (Optical Design)

Development Sector, Imaging Business Unit

Hiroki Harada began taking pictures when he joined his high school's art club. The first camera he ever purchased was a bellows camera from the 1950s. The three-dimensional appearance of prints of photos taken with that camera served as the starting point of his own lens rating scale. Though he majored in physics at university, he rarely went to class. Rather, he spent his six there locked in the photo club's darkroom. His first three years at Nikon were spent working on the technical development of steppers. However, upon his request he was transferred to optical design. The AF-S 24-70mm f/2.8G ED was the first lens for which he took charge of optical development. After that, he expanded his knowledge and experience with work on the AF-S 24mm f/1.4G ED, AF-S DX 55-300mm f/4.5-5.6G ED VR, AF-S 35mm f/1.8G ED, and viewfinder systems, and has put all of his effort into the optical design of the new AF-S 24-70mm f/2.8E ED VR. His favorite lenses for his own use are fast (large diameter) lenses from 60 to 90 years ago.

Development LeaderMakoto Fujiwara

As soon as an optical design is proposed, the mechanical design team determines requirements for commercial production. Mechanical design can also be said to be the embodiment of planning department ideas. We unify all aspects of development, including the mechanics, optics, and electronics, and are even involved with production technologies. The mechanical design team also considers ways in which added value might be applied to products. We do not only deal with features such as autofocus speed and the strength and durability of products, but also examine their operational feel, continuously striving for characteristics such as a more comfortable hold and simpler operation. However, to achieve all of these requirements, making products smaller and lighter eventually becomes a major issue.

Makoto Fujiwara (Development Leader)

Development Sector, Imaging Business Unit

Since childhood, Makoto Fujiwara has had a love of cars. In his youth, he was devoted to automobile racing and maintenance. Though he considered a job in the automobile industry, he found the precision processing performed with research interesting. He came to work at Nikon with a desire to design precision instruments. Since starting at Nikon, he has worked on the mechanical design of interchangeable lenses. Though he was initially disappointed to have been assigned to interchangeable-lens design, he now considers it the most appealing job, and one in which he takes great pride, because the "analog" aspects of interchangeable-lens design have such significant influence, even when everything else has become digital. To date, Mr. Fujiwara has been in charge of such lenses as the AF-S NIKKOR 24-70mm f/2.8G ED and the 1 NIKKOR VR 10-30mm f/3.5-5.6. He almost always has a camera with him, even on walks. His primary subjects are plants and flowers, animals, and his children.

This is how the AF-S NIKKOR 24-70mm f/2.8E ED VR was achieved

Optical DesignHiroki Harada

I was also in charge of optical design of the existing AF-S NIKKOR 24–70mm f/2.8G ED, and Mr. Fujiwara assisted with mechanical design. With that lens, we also looked into implementation of a vibration reduction (VR) function. However, we abandoned the idea because the technology available at that time would have made the diameter of the lens too large. Therefore, we consider this new AF-S NIKKOR 24-70mm f/2.8E ED VR a sort of revenge for which we have waited roughly ten years. Mr. Fujiwara and I were examining possible designs on our own well before the product team was established.

Development LeaderMakoto Fujiwara

When I first joined the company, I heard that there were a lot of rather eccentric people in the lens design department. When I was assigned to the department, I worried about whether I would fit in. However, my work on the existing AF-S NIKKOR 24–70mm f/2.8G ED showed me just how interesting and profound mechanical design is. I was hooked!
With initial design, the diameter of the existing AF-S NIKKOR 24–70mm f/2.8G ED was much larger. Along the way, we noticed that if 0.1 mm was shaved off from one component, this could completely change the internal structure, allowing us to reduce the external diameter by approximately 10 mm. With this, we considered a diameter that would make the lens more comfortable when it was held.
With that experience, we began designing this new lens by placing great importance on the user's comfort when they hold and use it, as well as simple operation. As the diameter of the lens would be important, we first decided on the diameter of operational rings as a part of the concept behind lens design.

Primary Mechanical
Design
Makoto Horikoshi

As mechanical design had so rarely begun with size having already been determined, the level of difficulty increased significantly. However, because the team leader was so insistent, we were very eager to succeed.

Makoto Horikoshi (Primary Mechanical Design)

Development Sector, Imaging Business Unit

Makoto Horikoshi has had an interest in mechanical things since he was very young. He spent his entire childhood observing and sketching mechanisms. At university, he majored in mechanical engineering. He spent a lot of time in the darkroom developing photos he took of the huge number of metal test samples used in experiments every day. This led to his interest in photography. After working in the manufacturing industry, Mr. Horikoshi came to work at Nikon in 2008. He is currently assigned to the interchangeable-lens design department, working on mechanical design, primarily of telephoto and super-telephoto lenses. On his days off, he enjoys attending Kawasaki Frontale J-League soccer matches with his family. He also enjoys observing the types of lenses, and their manufacturers, used by the professional photographers at the matches.

Development LeaderMakoto Fujiwara

In pursuit of a comfortable hold and good operational feel, we created various mock-ups, and began with unique trials with which the ideal size was determined before the internal structure.

Challenging limits

Optical DesignHiroki Harada

We adopted an optical design that did away with common knowledge for this product so that we could implement VR and make optical performance better than before. In selecting the type of zoom, we initially looked into adoption of the positive-lead structure for normal to telephoto zoom lenses that is also adopted by other manufacturers. However, while this structure enabled a shorter total length, the overall diameter of the lens became too large, and we could not accept that it did not allow for maximum optical performance. Then, despite the fact that it goes against all common sense with regard to optics and is generally considered useless, we examined the negative-lead structure often used for wide-angle zoom lenses. It seemed that this structure would work! With nothing to lose, I then consulted with Mr. Fujiwara as to whether or not it was mechanically feasible.

Development LeaderMakoto Fujiwara

I was able to tell Mr. Harada that it was mechanically feasible because I came up with the idea of applying the mechanical structure for a product with a different type of optics. With this response, we began work on something no other manufacturer had ever tried. However, development was more difficult than ever before. It took the full effort of every member of the five-person mechanical design team. Each member presented a new proposal every day.

Primary Mechanical
Design
Makoto Horikoshi

While the existing 24-70mm f/2.8G lens is also quite slim, we wanted to add a vibration reduction (VR) function for which there was no room. We spent every day looking for ways to modify the optical design to give us just one more tenth of a millimeter. With these deliberations, we discovered that there was no way the existing Silent Wave Motor (SWM) for autofocus would fit in the new lens. So, we asked for a smaller and more powerful new SWM.

SWM DevelopmentAzusa Muto

The silent wave motor (SWM) converts "traveling waves" measuring approx. 1 µm into rotational energy to drive the optics used for focusing. Though extremely precise processing of components is required, the SWM enables quiet autofocusing.
When we first heard the mechanical design team's request for a new SWM, we were blown away. Not only did they want it to be smaller so that it would fit in a smaller space, but they wanted it to be more powerful as well. This was a very difficult issue. Despite all of this, we were able to make a new SWM several millimeters smaller without sacrificing the strength of its components, and to increase its power by 50%. In boxing terms, it's as if we increased muscle strength while moving down three weight classes.

Azusa Muto (SWM Development)

Development Sector, Imaging Business Unit

Azusa Muto was born in 1981 in Akita Prefecture. He was a member of his high school's photography club. At university he majored in electrical engineering with his research focusing on ultrasonic flaw detection techniques. The combination of his interest in the precision technology he researched at university and his experiences as a member of his high school's photography club led him to employment at Nikon. Since starting at Nikon, he has worked on the design and development of ultrasonic motors. Having worked on the development of various types of ultrasonic motors, including rod-type compact ultrasonic motors and large-caliber ring-type ultrasonic motors, the new motor built into the new AF-S NIKKOR 24-70mm f/2.8E ED VR is the first for which Mr. Muto took charge of development. Fond of exercise and music, he enjoys running with his eccentric coworkers, as well as practicing with his band and performing at music festivals.

Primary Mechanical
Design
Makoto Horikoshi

The key question in realizing this new lens was whether or not we could achieve the requested SWM. Because we were able to make a desired SWM, a mechanical structure that harnessed its size and performance without sacrifice was devised. As a result, though the speed of autofocusing was well received with the existing 24-70mm f/2.8G lens, revision of the control system along with adoption of the new SWM has made autofocusing with the new lens approximately 1.5× faster and more accurate than before. It is one of the fastest F-mount NIKKOR lenses in terms of AF speed. (Comparison video)

SWM DevelopmentAzusa Muto

The SWM is constructed of relatively few components. Therefore, in order to make it more powerful, you need to optimize all of the components to the utmost limit. In our case, we repeated simulations using at least more than 100 possible designs for each component. From these, we chose the best forms depending on engineers’ instinct. In this way, every component of the SWM was optimized to the extreme.

Primary Mechanical
Design
Makoto Horikoshi

After this, designing is like assembling a 3-D puzzle. The elements to be included are focus, zoom, SWM, VR and aperture mechanisms. We used a 3D CAD application over and over to determine in 3D how to arrange them with consideration of component configuration and materials, processing, and assembly. We've become quite used to working in an endless loop (laughs).
We worked with mechanical designers on the VR and aperture mechanisms, achieving a product that offers the highest level of camera shake compensation available with a normal zoom lens and extremely accurate exposure.

Lens design is a team sport

Development LeaderMakoto Fujiwara

With development of this product, communication among team members was especially important. The real thrill of mechanical design is taking the lead with the entire development process, which includes optical design and manufacturing techniques. That said, the atmosphere in which we work is not strict or rigid. Rather, it is an open atmosphere in which everyone is free to state and discuss their ideas and opinions. We all enjoyed ourselves with the repeated exchange of positive ideas every day. As many of our discussions and debates went well into the night, we often went for drinks after leaving work to relax and unwind. At these times, we enjoyed sharing funny stories from our private lives (laughs).

Primary Mechanical
Design
Makoto Horikoshi

We started over from the beginning 6 times (!) with the design and development of this lens. Each time we thought we could see the summit, we would decide that we needed to increase optical performance even further and were forced to take a different route. However, these changes were the link to greater refinement, even in terms of mechanical design. We've also become used to dealing with seemingly unreasonable requests (laughs).

Optical DesignHiroki Harada

As a result, we could achieve the most beautiful arrangement of lens elements on which I have ever worked. You can tell a good lens from its cross-section view. With this lens, the arrangement of the 4th to 12th lens elements from the front side is especially beautiful.

Development LeaderMakoto Fujiwara

We struggled and almost gave up the concept initially determined for this product along the way. However, we were able to proceed by looking for and finding a new route. Often, when we faced a difficult problem, an idea would come to me while I was in the bath. Everyone has their own way of generating ideas. Some do their best thinking at coffee shops. I often think about work when I am not at the office. Considering this, we may need to have some kinds of creativity.

SWM DevelopmentAzusa Muto

I also get ideas while taking a bath. Though the SWM was actually developed before the lens was designed, there was a lot of adjustment along the way, requiring development to start over from the very beginning. In addition to being more powerful, we had to make it smaller. We considered all the ideas for achieving this, and searched for the optimal form. In order to achieve the necessary component precision with processing, I visited the factory and worked closely with them.

Primary Mechanical
Design
Makoto Horikoshi

Once a prospective design had been established, I went to the factory again to discuss mass production. Though I was in charge of structure, open and thorough communication with the factory allowed us to overcome difficult problems one by one so that nothing was impossible.

Development LeaderMakoto Fujiwara

Generally, historic products appear to be unreasonable from the planning stage. I think that the secret to success is finding enjoyment in the task presented, and tackling challenges as a team.

Optical DesignHiroki Harada

If designers and developers are conservative in their work, no noteworthy lens would ever be achieved. With every aspect of this lens, we began by striving to achieve the ultimate. Then, each member of the team voluntarily worked to achieve a higher and higher level of performance than that initially demanded (laughs). I think that we have reached the highest place one can hope for. As with the Nissan GT-R, this lens gives the impression of being an extremely high-performance product, despite the fact that it is mass produced.

Development LeaderMakoto Fujiwara

Yes. We had to rethink every aspect of this lens. Therefore, the fact that the team was able to achieve it, all while having fun, is quite a great thing.

Primary Mechanical
Design
Makoto Horikoshi

By continuing to work with the entire team always in pursuit of possibilities, we have achieved a masterpiece that represents the ideals of the team with this lens. I am sure that you will appreciate it if you take it in your hand.

Development LeaderMakoto Fujiwara

Today's lenses are created by concentrating the strength of a team. I think that all members working toward the same goals and the desire to strive for greater heights is the true essence of NIKKOR.