The Minds Behind the Magic - Production Technologies

What kind of element is the Blue spectrum Refractive (BR) optical element?

The BR lens structure SaitoTerunobu Saito: Natural light, with its wave-like properties, consists of an optical spectrum made up of different wavelengths, each with its own refractive index. Therefore, ordinary lenses are unable to focus light on a single point to produce a clear image. A variety of optical elements have been developed to date for lenses in an attempt to correct the chromatic aberrations that occur as a result. However, especially difficult was the development of lenses that can focus blue light, which is in the short wavelength range.

The BR optical element has the ability to target blue light alone and significantly refract it. As such, lenses incorporating this optical element can correct chromatic aberrations at an incomparably higher level than conventional lenses. So much so, it has become possible to obtain high-quality images with the least amount of blur even in astrophotography - a field where expressing each point has traditionally been extremely difficult.

• The BR lens structure

Reducing chromatic aberration

• Ordinary glass lenses
  A combination of concave and convex lenses is not enough to correct the blue light wavelength, resulting in different focusing positions for each wavelength leading to colors fringing.
• BR lenses
  The BR optical element is capable of significantly refracting blue light (in the short wavelength region). Employing this element in a lens that combines concave and convex lens elements enables it to focus the whole wavelength region of light on one point.

We heard that Canon developed the material used for the BR optical element in-house, is that right?

SaitoWe were searching for a solution to correct chromatic aberrations that the lenses available at the time designed using existing technologies couldn’t. It was then that our Design Division suggested we think about a method that could significantly bend blue light. So we began by looking into whether a material capable of that existed.

Of the many materials available on the market, some were already known to be able to significantly bend blue light. However, we had to give up on them because they were difficult to apply to lenses. Then we made up our mind to develop our own original material from scratch so that we didn’t have to compromise in any respect.

Creating a new material from scratch sounds like an exhaustively long, tough process. Specifically, what did you do?

SaitoSince this was our first attempt at creating an organic material in-house starting with its molecular structure, we began by setting up a lab.

Then we proceeded to material simulations and actually synthesizing candidate materials to evaluate their properties. We repeated this process over and over again. With a material simulation, regardless of whether a material could be actually synthesized or whether a material could be stable as a substance, as long as you input a value it will invariably come out with a result. If you merely fixate on the desired properties, however, a simulation could lead to unthinkable molecular structures that you have no way of producing. Therefore, we gave thought to the development in various ways: whether a material of this molecular structure could be synthesized this way, whether a material of that molecular structure could be stable under various conditions, and so on. In this way, we narrowed down candidate materials by actually synthesizing them for evaluation.

Whenever I reached an impasse, I would go through the catalogues of material and reagent manufacturers page by page while trying to come up with new ideas.

While people are likely to pay attention only to the material’s optical properties like its ability to bend blue light, we actually had to design the material taking into account various other factors as well, such as its manufacturing process, safety for the human body, workability when handling the material, and long-term stability. These were integral to the “unprecedented performance” that we sought in designing the material. In this sense, I can proudly say this material embodies our unparalleled enthusiasm for and commitment to quality and performance.

I imagine you must've been very happy when you finally completed the material after overcoming all these difficulties.

SaitoThe project was actually nothing less than a series of slow and steady efforts, but it was fun as well as challenging and rewarding. When I managed to find the solution to a given problem and achieve sought-after performance, I was practically shouting "eureka!"

The sense of achievement in creating something innovative that nobody had ever made before was the greatest experience I’ve had. Since a considerable part of this development project was personally entrusted to me, I did my best to accomplish what I had really wanted to do as a materials developer, instead of merely doing what I was told. This motivated me very much.

The field of new materials development is one where you can discover and understand things only after you have given it a try. I’m the kind of person who needs to try something and see for myself that it doesn’t work before I can accept it, so I went out of my way to do things with my own two hands and confirm everything with my own two eyes.

Currently, the BR lens has been incorporated into the EF35mm f/1.4L.II USM lens, which has caused a stir among users. Camera magazines have carried articles about delighted users who have said, “It really makes a difference,” and “this lens is amazing!” I'm sure it differs from old models in terms structure and the number of lenses used, but I also assume the greatest difference the adoption of the BR optical element. Is that right?

SaitoそThat’s true. The EF35mm f/1.4L.II USM lens of course incorporates several important improvements, but above all, the BR lens allows it to outperform other lenses in its ability to correct chromatic aberration. Eyeing its expanded application in more products, we have already begun R&D efforts for further sophistication and cost reduction of the BR lens.