| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which hardly generates density irregularity of lens diameter/radius pitch by a simple assembling method. <P>SOLUTION: In this optical system, it is understood that the value of the lens diameter pitch exhibits a gently-sloping variation with the de-focus position, but the value of the radius pitch exhibits a sudden variation with an approximately de-focus position-20μm as the minimum value. Namely, at positions shifted far or near out of the de-focus position-20μm, the radius pitch irregularity suddenly becomes conspicuous (even in human being's visual sense). As the sum of the lens diameter/radius pitches also exhibits a similar change, namely, a point where the irregularity of the lens diameter/radius pitch becomes minimum, that is, the best-FOCUS position seen from the smallness of the irregularity of the lens diameter/radius pitch, is a position deviated by approximately -20μm in comparison with the de-focus position (an alternate long and short chain line in the figure) where MTF becomes maximum, and when an LPH 16 is provided at this position, the image forming apparatus with the minimum irregularity of the lens diameter/radius pitch can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
