1. A differential image analyzer comprising in combination: a. apparatus for producing and storing an image signal related to a model device of the type to be analyzed; b. apparatus for producing an image signal related to the device to be evaluated and for comparing these image signals to produce a digital signal indicative of the difference between said images; c. apparatus for evaluating said digital signal to determine what portions of said digital signal corresponds to significant difference between said model device and said device to be evaluated; and d. apparatus for producing a composite image by combining the portions by said digital signal corresponding to significant differences between said model device and said device to be evaluated and an image related to said device being evaluated such that significant differences between said model device and the device being evaluated are emphasized and related to specific areas of the device.