Up to Utsunomiya: An extremely rare look at Canon’s primary lens factory

(by William Brawley and Dave Etchells)

It was still nighttime when we awoke in Yokohama, Japan the Monday following the CP+ expo. No time for any breakfast, but the hotel wasn't serving it yet anyway. We had to dash to the lobby to meet the group.

So why wake up before the crack of dawn? IR publisher Dave Etchells and I had the extremely fortunate opportunity to get a very unique and exclusive tour of Canon's Utsunomiya Office, home to one of the company's primary manufacturing plants, and the birthplace of all L-series lenses, Cinema EOS lenses as well as one of the their main R&D facilities. Canon has never before offered the press nor the public a tour of their factory with this much access to behind-the-scenes, proprietary processes. And they even allowed us to take photos! Needless to say, despite the early morning grogginess, we were pumped.

Boarding the bus from our hotel, catching a train, and then yet another -- the final one being a speedy Shinkansen "bullet" train -- we arrived north of Tokyo in the town of Utsunomiya. A short bus ride later, we finally pulled into the Canon campus around 9am.

Greeting and introductions

The Utsunomiya factory is enormous, spanning 160 x 200 meters. That's the size of about seven NFL-regulation football fields (4.7 soccer pitches). Inside, there's enough volume inside to fit four Airbus A380 jetliners. Yet, in the hours-long tour, we probably saw less than 10% of it.

The tour began with a round of introductions with Canon executives and factory staff. Utsunomiya factory manager Kenichi Izuki and his "Takumi" production experts greet us at the factory. Izuki-san is in the foreground, third from the right. (First on the right is Yuriko-san from the ICB Optical Products Planning Department, next to the left is Shogo-san, from the same department.)

Canon's Takumi experts are the extremely highly skilled craftsmen and craftswomen that know and understand the most intimate details of what goes into making a Canon lens. Takumi means "master craftsmen" in Japanese, and to become one takes years of training. One of these lens-assembly "meisters" is capable of assembling any of a number of lenses from raw parts, and it can literally take decades for someone to become a lens-polishing Takumi. According to Canon, one must have at least 25 years of experience learning the craft of lens design and manufacturing processes before becoming a meister.

In typical Japanese fashion, everything was planned to a "T", even down to our shoe sizes. Obviously designed for highly sensitive technology, it's no surprise that the factory has some strict anti-dust and anti-static requirements. All throughout the main facility areas, we were required to wear special anti-static footwear (seen above). In the assembly and testing areas, we had another set of special clean-room slippers for just those areas. We were also required to wear lab coats, hair and face masks as well as walk through an air shower to blow dust and other particles off of us before entering that section of the factory.

Even the delivery trucks in the shipping area have to carefully back up to narrow doors in the loading docks and create a kind of seal with the building so no outside air enters the facility.

Lens grinding/polishing and Canon's lens Takumi

Takumi Toshi Saito demonstrates the process of hand-shaping a master template used to make the diamond-grit grinding tools for lenses. The piece in his hand is a heavy polishing jig, this particular one weighing around 30 pounds (15kg), with diamond grit on the inside. The little plugs on the jig that he's grinding define the surface that the final tool will have. They have to be ground to within a tolerance of 30 nanometers (30 millionths of a millimeter). The tool he's using to do the hand-grinding doesn't exactly match the final target profile; Saito-san tweaks and adjusts the shape of the forming jig by adjusting the pressure as he slides the grinding tool over the jig. Normally, the jig is rotating while he does this, requiring a complex dance of pressure, angle, distance and timing. It was mind-boggling to us that someone could hand-grind something to tolerances in the millionths of millimeters.

This graphic gives you some idea of what 30nm of precision means in more human terms. If the lens were scaled up to the size of a large soccer stadium (300 meters diameter), the maximum surface deviation would be the thickness of a plastic shopping bag, or 0.03mm. Standard 20 lb. copier paper in the US is about 0.09 - 0.1mm thick.

Here's a look at a different set of tooling, this one used to produce a lens that's ultimately concave. On the far left, having the exact opposite curve of the final lens, is a mirrored prototype standard replica, that the tooling will be made to duplicate. The original prototype standards (which have the same shape as the final lens) are carefully stored away for use as master reference standards and not used during the actual production process; the mirrored prototype standard replicas are what's used on a production basis. We expected that the mirrored replica would have initially been machined to an approximate shape before final hand-tuning, but were told that its fabrication is entirely manual.

Saito-san is holding a measuring instrument here that he uses to check the shape of the intermediate jig or diamond plate, with the diamond plate itself in the middle. Only just visible at the far right is the final lens-polishing tool that's created from the intermediate jig. Somehow, the incredible precision of the diamond plate is transferred to the final polishing tool, which is covered in polyurethane. In the polishing operation, a slurry containing polishing compound (an extremely fine abrasive) is pumped over the rotating tool and lens blank. The polyethylene picks up the microscopic abrasive particles -- they're embedded in its softer surface -- and smooth the lens surface. Here, the final polishing tool is convex, which means that the lens surface it creates will be concave.

The factory has an incredible "library" of tooling like this, as each side of every lens element requires the creation of a set of tools like this. (Every lens element except aspheric ones, that is; those are made by an entirely separate process, pressing hot glass into super-precise molds.)

This chart explains the process just described above. In the background, you can see some prototype standards on the shelves. While the tooling we saw was made of steel, these were made of brass. When we asked why the difference, the answer came back "proprietary stuff". :-)

We were a little confused by the illustration here, because the prototype standard and diamond plate shown had the same shape. It turns out that the poster shows the original prototype master and the diamond plate, omitting the mirrored prototype replica that's used in between the two.

This is a row of automated polishing machines, polishing large lens blank. The tool rotates beneath the lens, while the machine's arm moves back and forth, pressing the lens against the tool. We didn't see the full factory floor, but from past experience, we know that a large lens factory can easily have hundreds of machines like this.

Diamond plate and polishing tool match each other from 4K/8K broadcast lens production.

Automated lens grinding and polishing

Canon is working steadily towards increasing the amount of automation of their production process, and have an entire group within the factory that just designs and builds production equipment. The unit above is a fully-automated lens grinding/polishing machine, capable of going from raw lens blanks to final processed lenses in about 30 minutes each. It's a multi-stage production line, though. While it takes 30 minutes from end to end, the machine spits out a new lens every 120 seconds.

Canon emphasized over and over again how important the skills of the lens Takumi were in developing fully-automated machinery like this. Grinding lenses is as much art as science, as the rotation rate, pattern of pressure (press this hard when the lens is at the edge of the tool and this hard when it's in the middle) will all vary according to the size of the lens, the type, and the type of glass being used to make it. When you consider that the Utsunomiya plant uses over a hundred different types of glass, to produce what must be many hundreds of thousands of different lens elements, you can gain some appreciation for the depth of the lens Takumi's knowledge.

This is a view of the full length of the automatic lens machine, courtesy a Canon graphic posted near it. Rightly concerned about showing too much of its detailed workings, they restricted the photos we shot to just one angle, at not too close a distance. We were allowed to take photos of any of the illustration posters we wanted, as those photos had likely been "sanitized" for sharing. The four parts that are labeled in the image here are (from left to right) initial coarse shaping, smoothing, centering (cutting the lens blank to a circular shape, perfectly centered on the lens's optical axis) and polishing.

Here's a raw lens blank that's fed into the machine above to be turned into a finished lens.

This chart shows the parts of the 16-35mm f/2.8 III that are made on this machine. The labels correspond to the lens elements. Judging from the positioning of the dots the lines connect to, it seems that only some of the surfaces of the lenses in question are made on the machine; in most cases, the second surface of the lenses is formed with the conventional process.

One of the most impressive parts of the machine is that it's self-monitoring and self-correcting. The lens elements are measured at two points in the process, and any deviations from the ideal profile are used to tweak parameters so the next one is closer to spec. This chart shows the maximum deviations allowed by the lens specs, as the bold red lines top and bottom. The blue dots show the actual measurements of each lens as it went through the process. The arrow denotes the narrower range at which the machine applied automatic corrections to stay within its very tight tolerance settings. Canon said that this automatic fine-tuning has reduced sample variation compared to the previous manual systems, but by how much, however, Canon didn't specify.

As yet, only a relative handful of the thousands of different lens elements Canon manufactures can be made on machines like this one, but they're expanding its repertoire steadily.

Lens assembly, telephotos (300mm and 400mm f/2.8 lenses in particular)

Next up was lens assembly. Since dust inside a lens would be disastrous (no way to get rid of it short of disassembling the whole thing), the whole lens-assembly area is a cleanroom, with highly filtered air. To avoid introducing dust (including dust from street clothes and human hair dander), we had to wear "bunny suits" before entering. That's not enough, though: After donning the suits, we had to pass through an "air shower", where nozzles blasted filtered air over us, to blow away any stray dust particles that might have lingered. (This is pretty standard in lens production facilities we've seen in the past.)

We toured the L-series telephoto assembly area. It's quite a process, putting together all the elements that make up a modern lens. Special assembly jigs like the one above help with the assembly process, getting all the pieces properly aligned as they go together.

It doesn't just depend on jigs, though; optical tests at various stages of assembly guarantee that elements are properly aligned with each other, above and beyond the basic geometry of the jigs.

Each lens element is inspected carefully under strong illumination, to make sure there are no dust specks on it. (It's amazing how easily the eye can see literally microscopic particles when they're brightly lit against a dark background.)

There are jigs within jigs, special tools, and yet still quite a bit of manual dexterity involved. This worker is adding the front element to an EF 300mm f/2.8L IS II.

After assembly, all lenses go through a rigorous, computer-controlled testing procedure. We weren't allowed to show too much of this (the test target was decidedly off-limits), but this is the head end of the operation. Specially modified full-frame camera bodies are connected to computers that analyze the images captured from the test target, rendering judgment on the lens's performance, in the case of zoom lenses, at a range of focal lengths as well.

This is the older, analog test system, largely unused these days. It works by projecting the image of a high-precision reticle on a screen twenty feet or so away (in the case of longer focal-length lenses). Technicians would inspect the projected image and grade the lens on its performance.

EF 16-35mm f/2.8L III automated assembly

Along with lens grinding and polishing, Canon is also working on automating the assembly process. (Again, thanks to their in-house production-engineering department.) This machine handles a couple of steps in the assembly of the EF 16-35mm f/2.8L III USM.

These parts show the input and output of the assembly machine above. As time goes on, more and more parts of the assembly process will be automated.

Testing for wide-angle lenses like the EF 16-35 f/2.8L III USM are done in a different setup than is used for the telephotos. This setup can manipulate the zoom ring and camera orientation. It goes through a series of steps, changing from horizontal to vertical orientation and adjusting the focal length to several different settings. (We've seen it often enough in our own lens testing that a lens might be fine at one end of its range, but out of kilter at the other end.)

Everyone loves a lens cutaway, so here's one of the 16-35mm f/2.8L III, the subject of the assembly and testing shots above.

Robot "tugs"

A random shot from the end of our tour: Robotic "tugs" (our word for them) pulled racks of materials and sub-assemblies along the factory corridors. They followed yellow lines on the floor, and apparently were aware of each others' presence, as there were places for them to pass each other. This one is just entering one of those areas, where the yellow line splits to provide two paths.

Conclusion

In the end, we were only shown the proverbial tip of the iceberg of Canon's lens factory in Utsunomiya, but the level of technical precision was frankly astounding. The biggest eye-opener for us was the sheer amount of skill and finesse it takes for the Lens Meisters to hand-craft the various shapes and curvature of different lens elements, down to nanometer precision! Seeing the level and depth of the manual skills involved, that took decades to master, it was all the more incredible that they could encapsulate all that into fully-automated lens grinding/polishing machines. And beyond that, the ability of the in-house manufacturing-engineering team to automate complex, formerly-manual assembly processes was extremely impressive. We've always been struck by the level of manual dexterity and large amounts of human labor involved in camera and lens assembly. The human hand and eye still have a decided advantage over robotic systems when it comes to complex assembly tasks. It will be interesting to check back with Canon five or ten years from now, though, to see just how much formerly human-only skill has been transferred to machines.

All in all, Canon's lens manufacturing system is a very impressive blend of time-honored handmade craftsmanship and ever-growing technical advancement.

We greatly appreciate the time and effort devoted by Mr. Masato Okada, Mr. Shingo Hayakawa, Mr. Kenichi Izuki and the rest of the team at Canon, and for giving us this rare peek behind the curtains, and letting us share the experience with our readers!

(Read more in our Canon Factory Tour Interview!)

• Canon Factory Tour Interview •