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Products (Medical Instrument)

Okamoto Glass Co., Ltd.: Dental Light Mirror


A dental chair light primarily must provide sufficient illumination for clear inspection of the narrow oral cavity; however, for the comfort of the patient, the light should not be dazzling, nor should it give off substantial amounts of heat. In addition, it should prevent shadowing which can arise from the position of the dentist’s hands or from dental equipment. For accurate diagnosis of dental and periodontal diseases, the color (or spectral distribution) of the light should be close to that of natural light, rather than possessing a reddish or pale blue hue, as is often the case with manmade light sources.
Okamoto’s light mirror can help to solve these problems, and is used by many dental chair light manufacturers worldwide: in 2014, Okamoto announced that their mirrors commanded 72 % of the global market share.

In dental lights, mirrors surround the main light source to direct the light forward with minimal loss, ultimately improving the illumination of patients’ mouths. These mirrors are called cold mirrors, and they are coated with a functional thin film to reflect visible light but transmit infrared light so that they do not emit heat. In addition to minimizing heat generation, Okamoto’s cold mirrors help to mimic natural light and reduce shadows, all to a high standard. This is accomplished by a thin-film coating that can control light at the nanoscale, developed by Okamoto’s unique technology.

・“Similarity to natural light,” “minimization of heat generation”
The functional thin film consists of many vapor-deposited layers. Each layer has a different refractive index, and the total film has a thickness of less than 1/1,000 of a millimeter. When light strikes each successive layer of the film, a proportion of the light is reflected and the other transmitted depending on the wavelength. The individual layers are carefully tuned such that the spectrum of the reflected light approximates that of natural light.
Furthermore, the film transmits unwanted infrared rays, so the heat is emitted towards the backside of the dental light.
・“Shadow dilution”
Rather than being flat, the glass surface is structured so that the light is reflected in all directions. As a result, shadows are minimized around the dentist’s hands.

Specialized glass products at the forefront
Since its establishment in 1928, Okamoto has designed specialized glass products for a wide variety of applications, adapting to new demands and developments and, in some cases, even cultivating new markets. As the company has committed to complete in-house production, it can combine its own high-quality components, produced by its own unique technology, to provide customized products made to the exact specification of its end-users.

At the beginning, Okamoto manufactured cut glass products for art glass. Around 1940, they started to manufacture glass for lighting and signal lamps aimed at marine applications. At the height of the Japanese shipbuilding industry, Okamoto’s marine light glass components reached 80% of the domestic market share. Responding to Japan’s motoring boom in the 1960s, Okamoto undertook the manufacture of cover glass for highway mercury lamps; also, approximately 60% of their sales at that time was generated from lenses for automobile headlamps. In 1996, they succeeded in developing the world’s first crystallized glass, and acquired patents for the composition and product; this type of glass is used in light sources for projectors. With the recent development of projectors capable of producing larger and higher resolution images, brighter and more powerful light sources are required; however, at the same time, manufacturers are keen to miniaturize their products. Brighter illumination from smaller light sources typically increases their operating temperatures, and thus the glass used in these applications needs to be able to tolerate these more strenuous conditions.

Societal changes often generate changes within industry; successful companies find a way to adapt and flow with these changes or, indeed, create change by themselves. Okamoto has forged its own path with unprecedented innovation. Starting with glass-coloring technology, Okamoto has steadily nurtured various technologies for specialized glass manufacturing. These technologies have led them to develop products with particular properties, such as improved heat tolerance, improved durability, electromagnetic wave transmission, or high uniformity. Such developments are a key part of the company’s legacy, and have made them competitive with other large manufacturers, both in Japan and overseas. 

Recently, glass flits and glass polarizer components have grown into the core parts of the company’s business. Glass flits are essential for the substrates of mobile phones, engine control units (ECUs) for cars, wireless local area networks (WLAN), or “One-seg*” modules, since they are used as conductive materials, insulators, low-temperature co-fired ceramic (LTCC) board materials, or encapsulant and sealing materials. Glass polarizers are used in image sensors, security cameras, optical measurement equipment, optical isolators, and microscopes. As we can see, Okamoto’s glass or thin film technologies enable the production of various products which have become an integral part of our daily lives.

*Japanese terrestrial digital broadcasting service for mobile devices

Thin Films
In the 1970s, Okamoto was commissioned to manufacture display lights for department stores. Although they were sure that a specialized coating on the glass surface would allow the reflector to satisfy the customer’s specification, their contract manufacturer was unable to produce the coatings with the requisite precision. Consequently, Okamoto decided to develop thin-film coatings in-house. One of their most notable innovations was a new technology for the even deposition of multiple layers of thin films, allowing them to carefully control the reflected light from glass surfaces; this technology has become a landmark for the company. Thin films are now one of their core products, and they have enabled the company to become the world’s top manufacturer of dental light mirrors. Additionally, their reflector designed for use in projectors boasts around 51% of the world’s market share (announced by Okamoto in 2014).  

The small unmanned submersible, Edokko-1
In 2001, a small Tokyo-based factory brought a proposal to the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), which would lead to the conception of the Edokko-1 submersible. The project team consisted of six small firms, JAMSTEC, several universities, several Shinkin banks, and supporting organizations (including voluntary bodies). The ambitious goal of the project was to build a submersible capable of recording images from the ocean floor and collecting mud samples at depths of up to 8,000 meters. By encapsulating a commercial camera in a glass sphere, Edokko-1 successfully fulfilled this goal in 2013.
Okamoto took on the challenge of manufacturing the glass spheres, which were one of the main components of the submersible. The spheres were designed to withstand water pressure equivalent to a depth of 12,000 meters. Although the project was dissolved in 2015, the technologies developed for it have since been expanded on a commercial basis. Okamoto has assumed a leading role, including the company’s specialized marine equipment division taking charge of promotion and sales. Product development is still being carried on by the original project participants including Okamoto. Currently, they are looking to design a new submersible which will be able to investigate sites with high levels of hydrogen sulfide, as well as increasing the operational depth from 8,000 meters to 10,000 meters. 

7 November, 2016

About the author
Hiromi Jitsukata is a reporter for Japanest NIPPON
(Okamoto Glass Co., Ltd.)