| 摘要 |
PROBLEM TO BE SOLVED: To correctly measure light beam shape by making a luminance value obtained by interiorly dividing the maximum value and the minimum value of the luminance distribution of a light beam with a specific ratio a luminance threshold in the luminance distributor and making a light emitting part having luminance of not less than this luminance threshold value a light beam shape. SOLUTION: The light beam emitted from a light emitting element 6 is converged by a lens 7 and the planar image of the converged light beam is picked up by a television camera 8 and is subjected to an A/D conversion and, then, the converted image is fetched into an image memory to be subjected to an image processing. Here, a luminance threshold value Kth is calculated by introducing a ratio TH (0<TH<1) and by an equation Kth =TH×Kmax +(1-TH)×Kmin . This equation means that the value to be obtained by interiorly dividing the liminance maximum value Kmax and the luminance minimum value Kmin with (1-TH): TH is made to be a threshold value Kth . Then, the area of a beam spot and the gravity position of the planar image of the light beam are calculated by detecting an area equivalent to luminance of not less than the luminance threshold value Kth and the gravity position of the area by an image processing device 10.
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