ULTRASOFT X-RAY MICROSCOPY 



being measured is allowed to pass through 

 the projector lens to the phototube window. 

 In this manner stray light scatter is effec- 

 tively eliminated. In Fig. 16, the resolution 

 of this system is demonstrated by the resolv- 

 ing of the Fresnel fringes associated with the 

 imaging of a diffraction grating of 10 micron 

 spacing ; the freedom from stray light scatter- 

 ing or "spill-over" is shown by the relatively 

 sharp corners of the shadow produced by a 

 25 micron wire. 



Application of Contact Microradiog- 

 raphy to Microniass Measurement 



A standard test object which has been used 

 in this study for quantitative microradio- 

 graphic analysis has been the human red 

 blood cell (erythrocyte) which was chosen 

 not only because of its importance to certain 

 medical research, but in particular here be- 

 cause it is of such material and size as to 

 make its precise measurement approach the 



MICROPHOTOMETER RESOLUTION 

 ( 0.5/1 x|0/i SLIT) 



IQS 



IO/< - ZEISS CALIBRATION GRATING 



ZERO LIGHT 



— o.oor— 



WIRE 



Fig. 16. Tests of the resolution and freedom 

 from stray light scatter for the microphotometer 

 shown in Fig. 14. 



10^ 



10' 



8 10 



50 



100 



X{A)- 



FiG. 17. Absorption characteristics for ultra- 

 soft x-radiations of essentially the hemoglobin 

 composition of human red blood cells (as deter- 

 mined for one test sample). 



limit of present day x-ray microscopy and 

 appreciably beyond the capability of other 

 types of microscopy, e.g., interferometric 

 microscopy. Sample smears of these cells are 

 easy to prepare in a standard, reproducible 

 manner. The single vacumn dried cell is ap- 

 proxmiately 8 microns in diameter, 2 microns 

 in depth, biconcave, of total mass 30 X V<r'^- 

 g and of mass density of about 0.4 g/cm^ Its 

 chemical composition is almost entirely he- 

 moglobin. 



In a recent study (10) a sample of normal 

 blood was centrifuged and washed in physio- 

 logical saline five times. 1" x 3" Spectro- 

 scopic-649 plates were coated with a thin 

 protective film of Parlodion by dipping into 

 a 1 % solution of Parlodion in amyl acetate, 

 and then smeared in the usual clinical man- 

 ner. A portion of the same sample was chem- 

 ically analysed for its effective absorption 

 components, C, X, and H. The analysis 

 for this sample and the corresponding ultra- 

 soft x-ray absorption curve is shown in 

 Fig. 17. 



A typical microradiographic field of the 



691 



