| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical element comprising a lens and a lens holding frame, wherein harmful and unwanted stray light which does not contribute to image formation is reduced without providing a light shielding means and a light absorbing means. SOLUTION: The optical element 1 is constituted by integrating the lens L<SB>11</SB>whose curved surface on an incident surface side is concave and which has a negative refractive index and the lens holding frame K<SB>11</SB>which holds the lens L<SB>11</SB>. When it is assumed that the refractive index of the lens L<SB>11</SB>is n, a maximum incident aperture of a light beam on the incident surface side of the lens L<SB>11</SB>isϕd<SB>1</SB>, the outer circumference diameter of the lens L<SB>11</SB>isϕd<SB>2</SB>, a distance D in an optical axis direction between a position on the maximum incident aperture on the incident surface side and a position on the outer circumference diameter on the emitting surface side in the lens L<SB>11</SB>is; D≤(d<SB>2</SB>-d<SB>1</SB>)/2*tan(arcsin(1/n)). COPYRIGHT: (C)2008,JPO&INPIT
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