Process And Measurement Of Progressive Addition Lenses

With the arrival of the aging society, people pay more and more attention to the health problem of middle-aged and elderly people, particularly the vision problem. However, in recently years those people are going to young-orientation in terms of health and self-image owing to the improvement of self-quality and the development of economy. Presbyopia which literally means 'middle-aged and elderly eyes', is physiologically inevitable. The oldest solution is the unifocal lenses that allow the wearer to focus on near objects again but not on intermediate or long-distance objects. Presbyopes need to take them on and off frequently. Later bifocal lenses were introduced and are also still in use. They are composed of two parts. Each part corresponds to a specific distance vision, but bifocal lenses give discontinuous vision with steps of power and image displacement between two different parts of the lenses and have visible lines on the lenses. Then the progressive addition lenses (PAL) are emerged as the times require. Through scientific design, PAL permit clear and continuous vision at all distance. There is no substitute for PAL as far as visual function is concerned.There has been nearly 50 years since the first PAL was launched in France in 1958. During this time, designers, who are engaged in continual improvement and uninterrupted innovation to establish process techniques, are gaining high-unity on vision and optics.The study on PAL is at the start in China. Firstly, theoretical analysis of advantages of Interior PAL is put forward by comparing the Exterior PAL and Interior PAL. Then the basic structure, working procedures and processing results of freeform CNC machine of making Interior PAL are introduced. Meanwhile, the experiments are carried out to analyze the factors affecting surface roughness.Finally, several measurements of PAL are discussed concisely, and the Hartmann test is put forward emphatically. The theoretical principles are analyzed, experiment setup is put forward and the measurement results are given here. The Interior PAL have been taken by the market and been accepted by the users. There has been measurement instrument which is adopting Hartmann test on the market. Moreover, the instrument has been applied widely among lens' manufacturing industry.