| 摘要 |
PROBLEM TO BE SOLVED: To obtain a light quantity filter which is good in the accuracy of a transmitted light quantity and phase difference and is decreased in variations by forming a thin-film layer in the recessed part side part of a difference in level formed on a substrate adjacent to an optical element, thereby varying the transmitted light quantity between a projecting part and the recessed part. SOLUTION: This filter has the difference in level on the substrate 1 adhered adjacently to the optical element. The thin-film layer 4 consisting of a metallic thin film is formed on the recessed part 2 of the difference in level and an antireflection film 5 is formed in order to make the transmitted light 100% in the projecting part 3 of the difference in level. The transmitted light 7 past the projecting part 3 of the difference in level of the cast incident light 6 is 100% in transmission efficiency and the transmitted light 8 past the recessed part 2 of the difference in level is attenuated in the transmitted light quantity by the absorption of the thin-film layer 4 and, therefore, the transmitted light quantity of the thin-film layer 4 is varied. The transmitted light 7, 8 vary in the phases by a quantity 9 of the difference in level. Then, the elimination of the phase difference between the transmitted light 7 and 8 by the transmission through the thin-film layer 4 is made possible by adjusting the quantity 9 of the difference in level. The arbitrary setting of the phase difference is possible as well and the correction of the astigmatism difference of lasers is also made possible. |
