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National technology lowers production costs of special lenses made with injectable plastics

EDUARDO CESARMold for the aspheric lens: quality, efficiency in glass or in plastic, and at a low costEDUARDO CESAR

Special lenses that make for a better quality of the images in medical magnifying glasses, microscopes, night vision glasses, and even cameras have begun to be produced by Optovac, a small company from Osasco, in Greater São Paulo. These lenses guarantee high quality images, without the small distortions of conventional lenses. They are called non-spheric or aspheric, and they can successfully remain in focus in a more efficient way, bringing down to acceptable levels the so-called spherical aberration, the failure in the formation of the image caused by the refraction of the light on spherical surfaces, a physical phenomenon that manifests itself in conventional lenses. The aspheric ones have a kind of curvature that makes it possible to get sharper images. They can be made with specific curvatures, avoiding focal problems that jeopardize the visual quality of the image observed. Roughly speaking, their appearance is more reminiscent of the format of a cone, with their curves more pronounced.

Faced by the challenge of mastering the sophisticated technology for the production of these lenses with the use of materials like injectable plastic – polycarbonate, polystyrene or acrylic -, that make it possible to cut production costs by half, Optovac is finalizing a project for the development of these products with the financial support of FAPESP, through the Small Business Innovation Research Program (PIPE). Started two years ago, the project has resulted in molds for the production of the plastic lenses, a process that should begin in October this year. For Sérgio Antônio de Almeida Nobre, a director of the company and the coordinator of the project, “the partnership with FAPESP was extremely decisive, because it allowed us to develop a technology that is unprecedented in the country and unique in the Southern Hemisphere”.

Market niches
From the economic point of view, the mastery of this technology takes on greater importance, to the extent that high quality aspheric lenses in transparent and moldable plastics are of interest to a wide range of industrial uses. In the medical area, in the magnifying glasses used in various operations; in the military area, in lenses for night vision; and in laboratories, in optic microscopes. But the ordinary consumer may also benefit from the same optic quality of the aspheric lenses put into glasses, leaving them lighter and with the lenses not as thick.

Another use that is already common is in cameras. The countries that produce this equipment, like Japan and Germany for example, use plastic aspheric lenses in the object glasses in conjunction with lenses of common glass, because they ally focal quality with the material durability. The problem is that, for cameras, aspheric lenses only acquire competitiveness if they are manufactured on a large scale. Other areas where these lenses are increasingly sought after and highly competitive are electronics and telecommunications.

They are products that have had their demand increased with the application of optic components in plastic, sophisticated and of a low cost, such as video cameras, light sensors and optical couplings (connections that join optical fibers together). Another use that is ever more common is in compact disc readers, when the laser beam crosses through the aspheric lens before touching the surface of the CD. “These are very competitive areas. I can only see possibilities for us to work in these areas in the medium term”, Nobre reckons. “Our goal is to work in smaller and more limited niches, which the major manufacturers have no interest in.”

Astronomy and medicine
Optovac wants to grab space in the educational, technical and general consumer areas, with optic kits for physics lessons, stereomicroscopes (binocular devices for teaching, research and industrial use in microassemblies in the electrical area), products for amateur astronomy, lenses for automobile high performance headlights, and components for other companies in the areas of medical instrumentation, clinical analyses, domestic goods and for electrical equipment. These products can reach, in some cases, the market at half the price of the imported ones.

For Sérgio Nobre, the challenge is to have prices that are compatible with the products from Asia and a better quality. “Our labor costs and production expenses are higher than those of the Chinese, for example, but we are going to face up to them with technology”, explains the director, who intends to qualify the company for exporting, in particular with products intended for the educational area. Optovac’s forecast sales for this are between R$ 1 million and R$ 1.5 million, in which the aspheric lenses should have a share of around R$ 100,000 a month, from October onwards. According to him, there is not yet any competition for the production of this equipment in Brazil, because the financial return is slow.

Another limitation is the difficult process for making aspheric lenses, whether in glass or in plastic. The secret, in which time and money has to be invested, lies in the mold for the lens that Optovac is developing. With efficient molding, it is possible to marry the advantages of these lenses with the low cost of injectable plastic. This technique also makes it possible to produce them in glasses with a low fusion point, because they are moldable at lower temperatures than those normally used, and are therefore cheaper than those of ordinary glass.

The production of these lenses starts with the use of software. The data for the manufacture of the molds for aspheric lenses are created and organized on a computer and inserted into an Computerized Numerical Control (CNC) Aspheric Generator, equipment used to repeat the manufacture of a product. It carries out a reading of the information programmed by the software and makes a mold for the lenses, on the basis of a pre-machined piece of glass or ceramic. To forge the mold, a grindstone goes round the piece, touching its side, which is refrigerated by water and a soluble oil that, besides maintaining its temperature, avoids undue abrasion of the pieces.

After this stage, another apparatus, a profilometer, measures the profile of the semi-finished mold. If there are differences between the data originally programmed by the computer and the end result, the software generates a correction file and the Aspheric Generator carries out the finishing touch on the mold. To make these pieces, the equipment has to have extremely critical requirements of control, advance and mechanical stability. This allows the lenses to come out ready to receive a final optical polishing, when their opaque surfaces are made completely transparent.

Developing from scratch
Created in 1986, with the goal of making equipment with technologies involving fine mechanics, Optovac went on to work in the optic segment, with research products for the educational area and for general consumption, such as kits for teaching science, telescopes and microscopes, and they even developed this kind of equipment for research institutes connected with the University of São Paulo (USP) and the State University of Campinas (Unicamp). However, with a limited commercial field and the opening up of the market over the last decade – which brought products with more competitive prices to Brazil -, the company found itself obliged to invest in research and to develop from scratch a technology that already existed abroad.

And why not simply import the technology? According to Sérgio Nobre, the reason is simple: the costs of importing come to US$ 2 million – for a production that caters to the small niches that there are in Brazil – are far higher than the cost of developing it locally, and are unjustifiable in the light of the small demand in the domestic market. With the aim of raising the quality of the products at a lower cost, the PIPE project made the company’s technological triumph possible, developing the first prototypes in two years. Work went on simultaneously on technological development and on possible applications in products.

Optovac nowadays has the capacity to supply the domestic market in a customized fashion, as the consumption of these items is small in Brazil. “We are producing 20,000 spherical lenses for one customer (he cannot mention the name of the company, nor the application for this product); and for the Nuclear and Energy Research Institute (Ipen), we have just produced a single lens (aspheric), specially developed for use in this institute’s research, that is to say, we have a differentiated structure that allows us flexibility in production”, says the company’s director. Optovac is even accredited by the Brazilian Army’s aviation unit for the development (of aspheric lenses) and maintenance of optical equipment, such as the night vision glasses, which are currently imported and depend on maintenance outside the country.

The project
Optic Components in Injected Plastic with Non-Sperical Surfaces (nº 99/11415-8); Modality Small Business Innovation Research Program (PIPE); Coordinator Sérgio Antônio de Almeida Nobre – Optovac; Investment R$ 33,000.00 and US$ 156,236.00

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