1964 年 33 巻 12 号 p. 882-886
With the view to improving the performance of inversion viewer, a method of measuring of the optical transfer function (OTF) of infrared quenching fluorescent screen is described. If the resultant OTF of photographic lens, infrared quenching fluorescent screen and microscope is DR(ω), and that of photographic lens and microscope is DLM(ω), then the OTF of the screen DF(ω) is given by DF(ω)=DR(ω)/DLM(ω). To practice the principle, an apparatus for measuring DR(ω) and DLM(ω) has been constructed and the method of obtaining OTF of the screen is described. The OTF of the infrared quenching fluorescent screen (ZnS:Cu:Co screen) with various thickness of the coated layer is measured. Furthermore, OTF of ZnS:Cu:Co screen is also measured while changing the intensity of the infrared rays used for forming the inversion image of the object slide on the ZnS:Cu:Co screen. The results thus obtained are as follows:
(1) The thickness of the coated layer of ZnS:Cu:Co screen, which makes the value of OTF the highest, is about 4mg/cm2.
(2) The OTF of ZnS:Cu:Co screen varies with the intensity of infrared rays. The value of OTF increases with the increase of intensity of the infrared rays at low spatial frequencies whereas it decreases at high spatial frequencies.