COATACT MICRORADIOGRAPHY 



Encyclopedia of Physics. Vol. XXX (Edited 

 by S. Flugge, Springer-Verlag, Berlin, 1957). 



11. CossLETT, V. E., Engstrom, a., and Pattee 



H. H., Jr., "X-ray jSIicroscopy and Micro- 

 radiography," Academio Press, New York, 

 1957. 



12. Baez, a. v., J. Opt. Soc. Am., 42, 756 (1952). 



13. Gabor, D., Proc. Roy. Soc, A197, 454 (1949). 



14. Myers, O. E.,Jn.,Am. J. Phys.,19, 359 (1951). 



15. Strong, J., "Concepts of Classical Optics," 



W. H. Freeman & Co., 1958. 



16. Henke, B. L., Seventh Annual Conference on 



Industrial Applications of X-ray Analysis, 

 University of Denver, 1958. 



17. Mack, J. E., and Martin, M. J., "The Photo- 



graphic Process," McGraw-Hill Co., Inc., 

 1939. 



18. KiRBY, D. S., Pubs. Astron. Soc. Pacific, 71, 



334 (1959). 



19. DeJager, C, Ann. de Geophysique, II, 1 



(1955). 



20. GiACcoNi, R., AND Rossi, B., /. Geophys. Res., 



65, 773 (1960). 



21. Berning, p. H., Hass, G., and Madden, R. P., 



/. Opt. Soc. Am., 50, 586 (1960). 



22. Walker, W. C, Rustgi, O. P., and Weissler, 



G. L., /. Opt. Soc. Am., 49, 471 (1959). 



Albert V. Baez 



X-RAY MICROSCOPY 



BONE STRUCTURE AND AGING BY CONTACT 

 MICRORADIOGRAPHY. See MEDICO-BIO- 

 LOGIC RESEARCH BY MICRORADIOG- 

 RAPHY, p. 591. 



CONTACT MICRORADIOGRAPHY 



Microradiography is the name apphed to 

 the oldest and simplest type of x-ray imag- 

 ing, which is accomplished by placing the 

 specimen in direct contact with a recording 

 material, exposing to x-rays, and subse- 

 quently viewing the image with a micro- 

 scope. No direct x-ray magnification is ob- 

 tained, and the maximum resolution is 

 therefore limited by the granularity or struc- 

 ture of the recording material. Although the 

 earliest uses of the basic method go back 

 several decades (1-3), it was not until the 

 introduction of the Lippmann type photo- 

 graphic emulsion, with grain size under a 

 micron, that high optical magnification of 

 the x-ray image became useful. Many dis- 

 cussions of this technique are in the litera- 

 ture (4-8) and additional applications will 

 be found elsewhere in this volume. We shall 

 limit our discussion to the technical require- 

 ments for microradiography, and to a de- 



scription of some of the newer modifications 

 and extensions of the basic method. 



Basic Geometry of Contact Method 



The great simplicity of the contact image 

 geometry is an obvious advantage when the 

 other possible systems of x-ray imaging are 

 considered by comparison. Less obvious are 

 the advantages in speed, resolution and 

 width of field which are obtainable with the 

 contact method. The author has indicated 

 (16, 20) how this method may offer superior 

 potentialities in these respects than the 

 other techniques of x-ray microscopy now 

 known. 



To realize these advantages for a given 

 specimen size and thickness requires the 

 proper choice of source size and source loca- 

 tion with respect to the specunen. In general, 

 the source-to-specimen distance should be 

 small to give maximum intensity, but it must 

 not be so small that the som'ce penumbra 

 limits the resolution or that the obliquity 

 of the rays causes image distortion or un- 

 even illumination over the desired field. For 

 the fixed source diameter of a standard x-ray 

 tube and average specimen thickness (10- 



561 



