Interferometric measurement of the refractive-index distribution in plastic lens

초록

Plastic materials are widely used as optical components in digital cameras, copiers, mobile phone cameras, and other equipment. The advantages of plastic lenses are lower cost and superior productivity on aspherical surface. But they are subject to refractive-index and birefringence distribution. Therefore, to enhance the optical quality, the uniform refractive-index distribution of plastic lenses is important to manufacture. We propose a measurement method in which refractive-index distribution is determined from the wavefronts gained by Zygo interferometer. The liquid immersion method is applied to measure the wavefronts of optical components. The effects of refraction at the surface of the test lens are therefore removed and laser beam travels in a straight line regardless of the shape of the test lens. It is immersed in a chamber, which is filled with a matching liquid whose refractive index is nearly the same as that of the test lens. When the wavefronts are transmitted, interference fringes are integrated along the optical path and an average refractive-index distribution is calculated.