| 摘要 |
In the present invention provides, in order to obtain a desired focal depth t in a range a of an acceptable increased amount of beam diameter, an exposure head is designed so that the ratio D/W of an output beam width D to a beam width W at the position where a DMD is placed satisfies the following relational formula. <maths id="MATH-US-00001" num="1"> <MATH OVERFLOW="SCROLL"> <MROW> <MFRAC> <MI>D</MI> <MI>W</MI> </MFRAC> <MO><=</MO> <MFRAC> <MROW> <MFRAC> <MROW> <MI>alpha</MI> <MO>x</MO> <MI>M</MI> </MROW> <MROW> <MN>2</MN> <MO>x</MO> <MI>t</MI> </MROW> </MFRAC> <MO>-</MO> <MFRAC> <MROW> <MI>K</MI> <MO>x</MO> <MI>lambda</MI> </MROW> <MI>a</MI> </MFRAC> </MROW> <MI>theta</MI> </MFRAC> </MROW> </MATH> </MATHS> In the above formula, parameters are defined as follows. lambda: the wavelength of laser light theta: the angle of beam outputted from an illumination light source that is derived by a numerical aperture (NA) of optical fiber according to the following formula theta=sin<SUP>-1 </SUP>(NA) D: the width of beam outputted from the illumination light source W: the beam width at the position where the DMD is placed (at the irradiated surface) a: the size of one pixel on the DMD K: a coefficient determined by beam characteristics, K= 1 M: the magnification of imaging optical system t: required focal depth alpha: acceptable increased amount of beam diameter
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