照相影像RMS粒度的测试研究

A STUDY ON RMS GRANULARITY MEASUREMENT OF PHOTOGRAPHIC IMAGE

RMS粒度是照相材料成像质量的重要特性。使用显微光密度计-电子计算机系统进行该项测定是目前最为先进的方法。这种方法自动进行数字采样,按编制好的程序计算,具有快速简便的优点。但测试过程中有许多重要环节,如果处理不当,计算出的结果值就完全不能代表样品的粒度水平而只是一个完全错误的结果。本文通过设计的各种实验,研究了仪器系统噪声,样品中宏观密度不均及影像数字化时采样间距对RMS粒度测值的影响。结果表明,必须选取恰当的实验参数和数据处理方法,才能消除上述各种干扰,得到RMS粒度的正确估值,同时,本文还对数字模拟光孔与真实光孔的RMS粒度测值作了比较,得到了有实际应用价值的结果。

RMS-granularity is an important characteristic of photographic image quality.Measuring RMS-granularity by microdensitometer-computer system is the most advanced method nowaday.Auto-sampling and programmed calculation make the measuring to be fast and convenient.However,a completely wrong result may be occured if some points are not properly handled during processing.The relationships between the RMS-granularity and instrumental system noise,the ununi-formity of sample macrodensity,the sampling interval of image digitalization were studied.As a result,it indicates that various disturbances may be removed and a correct estimating value of RMS-granularity can be obtained if the appropriate parameters and program are selected.In the meantime,the RMS results were compared by using digital simulating optical aperture and real optical aperture,and got some results valuable in application.