| 摘要 |
PURPOSE:To calculate easily and exactly a visual luminance by deriving a center cavity adaptation luminance corresponding to a luminance variation in a visual field from a visual field average luminance, which has been measured as a time series at a prescribed time interval. CONSTITUTION:An optical image from an object to be viewed reaches a photodetector 11, and a photodetector 12 for luminance L0 of the object to be viewed, through an image forming lens, etc., and diffused light beams which have passed through a photodetecting window 8 reache a photodetector 13 for an equivalent light curtain luminance Lev. A signal of a visual field average luminance which is measured by the photodetector 11 is amplified 14 and A/D-converted 17, and held in latches a1-an of a latch group 20 at a time interval (t). After the time interval (t), signals from the photodetectors 11, 12 and 13 are amplified 14, 15 and 16, A/D-converted 17, 18 and 19, and held in latches 23, 21 and 22, respectively. In this regard, these signals are measured successively, at the same time, or within a time of an extent that is regarded as the same time. In this state, from luminance data which have been held in the latch group 20 and the latch 23, a luminance Lf at the time when luminances Lo, Lev have been measured is calculated by an Lf calculating part 24, and from the luminance data of these Lf, Lo, and Lev, a visual luminance is calculated 25 and displayed 26.
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