I.ICIIT (OPTICAL) MICROSCOPY 



Hardness Tests. A special case of surface power of the photographic emulsion instead 

 examination is the determination of the di- of the acuity of the eye. This of course is a 

 ameter of the depression formed in the test special case of photomicrography (q.v.) 

 piece during a hardness test of the Brinell Schmaltz Profile Microscope. It has 

 type. The depression is illuminated by a been shown that in surface examinations the 

 vertical illuminator and the magnified image conventional microscope is not able to make 

 formed in the focal plane of the eyepiece can possible depth measurements. If a normal 

 be measured in two ways. The simplest is by section of the specimen could be cut the 

 comparison with a glass scale mounted in depth could of course be measured directly 

 the focal plane of the eyepiece upon which as a simple lateral measurement. In the Zeiss 

 the image of the indentation is focused and Schmaltz Microscope this section cutting is 

 the diameter measured, as though the scale effected by optical means. A line of light is 

 were an ordinary rule, down to 0.01 mm. focused on to the surface by means of an 

 The magnified image may be measured more illuminating unit inclined at an angle of 45° 

 accurately with a micrometer eyepiece. Two to the surface inspected. This line of inter- 

 wires at right angles are mounted on a slide section is then viewed with a microscope also 

 in the focal plane of the eyepiece, and the inclined 45° to the surface and 90° to the 

 slide is moved by a micrometer screw from illuminator. The appearance in the eyepiece 

 one side to the other of the indentation consists of a band of light rumiing across a 

 image. It is easily possible to measure within black background. The microscope is fo- 

 0.001 in. on the magnified image which with cnsed on one edge of this band, and the 

 a magnification of 10 X means 0.0001 in. in image thus forms a magnified contour of the 

 the actual depression. Excellent equipment surface. If the magnification is M, then the 

 is available in which the microscope is built pitch or frequency of variations along the 

 into the hardness testing machine. band is magnified M times, and the departure 



Comparison Microscope. In the estima- from straight lines, representing depths, 3=2 

 tion of surface finish by comparison with M times. Measurements are made with a mi- 

 standards, the conventional microscope suf- crometer eyepiece. The instrument is suit- 

 fers from the disadvantage that only one able for measurement of surface finish of 

 specimen can be viewed at a time and ap- turned, bored and ground surfaces in which 

 pearances have to be memorized. It is not the scratches all run in one direction, 

 practicable to arrange specimen and stand- The Introscope. The examination of the 

 ard side by side for simultaneous viewing, so interior surfaces of long tubes such as rifle 

 that special comparison microscopes have bores and gun barrels is a problem for which 

 been designed, the objects being well sepa- the conventional microscope is unsuited. The 

 rated while the images are formed in adja- Introscope design for this purpose consists 

 cent positions in the eyepiece. This is done of a low-power microscope with built-in il- 

 with prisms which form semicircular images luminator, and a special copying system of 

 on each half of the eyepiece. lenses which enables the objective at some 



Projection Microscope. It is possible to adjustable distance down the tube to be well 



make comparisons of specimen and standard separated from the eyepiece at the end of 



by projection in which a screen takes the tube. The objective forms an image of /i of 



form of a photographic plate. The two ob- part S of the surface under examination; 



jects are not viewed simultaneously but a light from the lamp scattered from S reaches 



photographic record is made of each sepa- the lens after reflection by a prism. Copying 



rately and thus the choice of the eyepiece units consisting of pairs of collimating lenses 



magnification is determined by the resolving successively transfer the image to I2 , h , h 



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