Ho-Soon YANG, Yong-Geol JO¹, Gyu-Ug KIM¹, and Yun-Woo LEE

Center for Space Optics, Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea
¹Department of physics, Kumoh National Institute of Technology, Gumi, Gyeongbuk 730-701, Republic of Korea

(Received October 11, 2010; Accepted August 10, 2011)

The chief ray angle (CRA) of a mobile phone lens is related to the acceptance angle of the IR cutoff filter and micro lens array. The CRA of a lens need to be within an allowed value, otherwise image blurring or vignetting occurs. However, because of the compact size of mobile phone camera lenses, it is not easy to measure the CRA accurately. In this paper, we suggest a new method to measure the CRA of high-quality mobile phone camera lenses accurately using a laser beam as a light source and a plane mirror to collimate the beam in a double pass configuration. When the plane mirror is tilted to the same angle as the lens CRA, the spot center does not change, irrespective of the longitudinal position of the plane mirror. We manufactured the reference optics, which consisted of four spherical lenses, to verify our method. We found that our new CRA measurement method has 0.65° of measurement uncertainty for 15° CRA, which satisfies phone camera makers' requirements.

Key words: CRA, mobile phone camera, cat's eye retroreflector, reference optics, first momentum