Patent US 5,400,513

The present invention makes possible the quick, accurate analysis of images, especially medical diagnostic images of unknown magnification, to determine the size of objects visible therein, by reference to an object of known size or to determine the magnification ratio when it is unknown. There is provided a transparent image measuring device having one or more line pairs of varying spacing. Various scale markers are included on lines running substantially at right angles to the line pairs. The device is placed on the image over an object of known size (the reference object). The device is located so that the reference object just bridges between the spaced-apart lines in a particular location which is associated with a scale marker corresponding to the true size of the reference object. Once the line spacing of the reference object and the corresponding scale marker are determined, the device is moved to overlie the object of unknown size such that the object of unknown size just bridges between continuations of the lines having, in general, different spacing than that for the reference object. The size of the unknown object is then immediately read from the orthogonal scale marker associated with the new spacing without the operator performing any mathematical calculations or table look-up. Where the magnification ratio is known, a reference object is not needed and the device may be set to indicate the dimensions of objects of unknown size directly.