| 摘要 |
Methods and apparatus for measuring the reflectance in a visible spectral wavelength band by visual comparison of a surface viewed through a filter with a set of reference reflectance areas are described. An appropriate filter and reference reflecting areas are useful for estimating skin pigmentation, corresponding skin sun sensivity and sun exposure time tolerance. Tables are included for the solar erythemal radiation environment in different locations for different times of the year for use in determining sunlight exposure time tolerance. Also methods to use skin reflectance data along with local solar ultraviolet index data to determine sunlight exposure tolerance times are included. In addition, methods to ensure sufficient exposure for previtamin D generation are included along with techniques to reduce the risk of skin cancer. The combination of a filter and gray scale for the reflectance measurement results in a low cost device in comparison with other meters and instruments making the device affordable for many persons.
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