There is a great demand today for ever-smaller low-cost zoom lenses for digital cameras. To meet this demand, we have been realizing some compact zoom lenses by using plastic lens elements. Nowadays, plastic lens elements produced by injection molding are widely used in zoom lenses for digital cameras because of their suitability for volume production and ease of forming aspherical surfaces. Although using plastic lens elements in digital camera zoom lenses has its advantages mentioned above, there are some difficulties to be overcome for using plastic lens elements, such as an elevated sensitivity to the temperature change and the non existence of high-refraction materials. In this paper, we show some examples of commercialized digital camera zoom lens optical designs employing plastic lens elements such as a) retractable 3x zoom lens for digital still cameras and, b) 3x zoom lens using a right angle prism for digital still cameras and c) 25x zoom lens for digital camcorders in which benefits of plastic lens elements are effectively exploited and drawbacks of the material are well overcome.
Recently, plastic lenses produced by injection molding are widely used in image taking objectives for digital cameras, camcorders, and mobile phone cameras, because of their suitability for volume production and ease of obtaining an advantage of aspherical surfaces. For digital camera and camcorder objectives, it is desirable that there is no image point variation with the temperature change in spite of employing several plastic lenses. At the same time, due to the shrinking pixel size of solid-state image sensor, there is now a requirement to assemble lenses with high accuracy. In order to satisfy these requirements, we have developed 16 times compact zoom objective for camcorder and 3 times class folded zoom objectives for digital camera, incorporating cemented plastic doublet consisting of a positive lens and a negative lens. Over the last few years, production volumes of camera-equipped mobile phones have increased substantially. Therefore, for mobile phone cameras, the consideration of productivity is more important than ever. For this application, we have developed a 1.3-mega pixels compact camera module with macro function utilizing the advantage of a plastic lens that can be given mechanically functional shape to outer flange part. Its objective consists of three plastic lenses and all critical dimensions related to optical performance can be determined by high precise optical elements. Therefore this camera module is manufactured without optical adjustment in automatic assembling line, and achieves both high productivity and high performance. Reported here are the constructions and the technical topics of image taking objectives described above.