| 摘要 |
PURPOSE:To improve the chromatic aberration correcting capacity by forming a porous body having a specified concn. gradient with a first dopant, then dipping the body in a soln. contg. a second dopant and thereby imparting the resultant specified concn. gradient to the body. CONSTITUTION:A wet gel is prepared from an alkoxide by the sol-gel method, aged and then treated with an eluent to elute the dopant and dried to form a porous dry gel having the convex concn. gradient of the first dopant metals selected from Ba, La, Sr, Ca, Ge, Zr, Y, Zn, etc., in the skeleton. The porous dry gel is dipped in an appropriate solvent to fill the solvent into the pores. The gel is then dipped in the soln. of the second dopant to impart the concave concn. gradient of the second dopant metals selected from Ta, Nb, Pb, Ti, Zn and Zr to the gel. The gel is then dried, heated and sintered to obtain a distributed refractive index-type optical element having two independent concn. gradients. The porous body having the first concn. gradient is also obtained from the soot synthesized by CVD method.
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