Johansson S, Biedermann K
Appl Opt. 1974 Oct 1;13(10):2280-7. doi: 10.1364/AO.13.002280.
The Multiple-Sine-Slit Microdensitometer (MSSM) measures transmittance modulation by scanning the sample with a sinusoidal irradiance distribution generated by laser two-beam interference. The theory of the instrument is derived both from conventional microdensitometry and from treating the sample as a complex valued grating that diffracts two impinging coherent fields. The instrument has a constant MTF of 0.5; its principle disregards any phase modulations in the sample; and its large measuring area improves signal-to-noise ratio by 1-2 orders of magnitude. These are necessary qualifications for determining the MTF of recording materials of very high resolution. With a He-Ne laser, the range of the MSSM spans from 4 c/mm to 1500 c/mm. The practical implementations of the evaluation of film MTF's with this system are described.
多正弦狭缝显微密度计（MSSM）通过用激光双光束干涉产生的正弦辐照度分布扫描样品来测量透射率调制。该仪器的理论既源于传统的显微密度测量法，也源于将样品视为衍射两个入射相干场的复值光栅。该仪器的调制传递函数（MTF）恒定为0.5；其原理忽略样品中的任何相位调制；其大测量面积将信噪比提高了1 - 2个数量级。这些是确定超高分辨率记录材料MTF的必要条件。使用氦氖激光器时，MSSM的范围从4线/毫米到1500线/毫米。描述了用该系统评估胶片MTF的实际应用。
