| 摘要 |
PURPOSE:To make a sufficient refractive index distribution at an irradiation range and to enable to control a precision working by irradiating an infrared beam to a material in an atmosphere of a low pressure. CONSTITUTION:The thermal expansion is accelerated in the range 3 of the material 2 in the atmosphere of the low pressure, when the infrared beam 1 is irradiated on the optical material 2 provided on a beam absorption plate 5 put in a vacuum vessel 4. The density distribution due to a residual strain attending to a construction after the irradiation occurs in the range 3, thereby generating the refractive index distribution. As the deformation due to the thermal expansion may be deduced to be a spherical surface, the refractive distribution with the spherical effect has a shape resemble to Gaussian distribu tion. Accordingly the desired refractive index distribution is obtd., thereby enabling to be easy to control the precision working.
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