AUTOMATIC RECORDING PH.OTOGRAPHIC DENSITOMETERS

Transcription

1 No. 4 `5, Dec., 1955 AUTOMATIC RECORDING DENSITOMETERS 35 inefficient monochromatization by 20 mm Fe. When average energy of secondary electron is assumed to be 70 kev, speculated tee value is 1.4 x 103 This value isabout 3 times that of experimental one, to which 130 kev electron corresponds. In both. cases of 100 kvp and 200 kvp, experimental values of,ue are equal to inverse of range of electron whose energy is equal to about 2/3 of incident x-ray photon energy. Although above considerations are still insufficient, y will be able to account for intensifying action of lead screens qualitatively. Conclusion When an x-ray film with lead screens of suitable thickness is exposed to x-rays whose quality was hardened by approriate metal filters, photographic density increases. several times more than in alternative case. Optimum thickness of front screen increases with incident x-ray photon energy, but saturation value of thickness of back screen decreases with increasing x-ray photon energy. Obtained results are summarized in Table 1. LITERATURE 1. A. H. COMPTON and S. K. ALLISON : "X-rays in Theory and Experiment" (Van Nostrand, New York, 1936) 2. T. SENDA : "Industrial Radiography", edit. by NDI (The Nikkan Kogyo Press, Tokyo, Japan, 1954) p G. H. HINE: Nucleonics, 7, (4), 18 (1950). 4. L. KATZ and A. S. PENFOLD: Rev. Phys., 21, 28 (1952). 5. M. DAVISON and D. EVANSE: ibid., R. GLOCKER : Z. Physik, 136, 352 (1953). Bulletin of Society of Scientific Photography of Japan, No. 4-5, Dec., 1955 AUTOMATIC RECORDING PH.OTOGRAPHIC DENSITOMETERS (Received Oct. 3, 1955) Mataichi TAJIMA & Shingo OUYE Research Laboratory, Fuji Photo Film Co., Ltd. Introcduction Recently, some photoelectric densitometers1 `5) have been devised taking place of visual densitometers for photographic densitometry. These photoelectric densitometers require less time than visual densitometer, and prevent ocular fatigue of observer, and refore, good accuracy of measurement may be maintained continuously, and personal errors may be diminished. But observed values by photoelectric or visual instruments must be plotted " manually " to draw a characteristic curve. This operation, which causes a personal error, requires much time and reduces speed of sensitometry. Now, authors devised automatic recording densitometers, which may be superior

2 36 M. TAJ1MA & S. 01=Bull. Soc. Sci. Phot. Japan to photoelectric densitometer, as devised densitometers can also draw characteristic curves, and moreover, are available as a microphotometer by changing sample driving gears and an illuminating slit. There is, however, anor type of automatic recording photographic densitometer, so-called " microphotometer ", which can observe an extremely narrow area of photographic meterial for sake of physical research of a developed image. Thinking over a few publication of study on automatic instruments, which record characteristic curve"), and conversely many on microphotometers8 `4) device of former type seems to be rar troublesome. The new instruments designed by authors are for transmission, and for reflection densitometry. In this paper, y report on T-54 (transmission type) and on R-55 (reflection type).* Performance Model T-54 automatic recording transmission densitometer: measuring density...diffuse printig density range of measuring density...d=0 `3 measuring rate (for one strip)...12/3 min. or 31/3 min. accuracy... }0.01 (density) measuring area ~1 mm (a projected slit image) electric source...ac 100 V 50 `or 60 ` recorder...electronic automatic balancing potentiometer strip chart recorder mfd. by Yokogawa Electric Works sample mm length, strip exposed by a continuous wedge circuit...dynode feedback logarithmic amplifier and a functional resistance Model R-55 automatic recording reflection densitometer: measuring density reflection density range of measuring density...d=0 `2.5 measuring rate (for one strip)...5 min., 12/3 min. or 15 min. accuracy... }0.01 (density) measuring area ~1 mm (a projected slit image) electric source...ac 100 V 50 `or 60 ` recorder...electronic automatic balancing potentiometer recorder mfd. by Hokushin Electric Co. sample mm length, strip exposed by a continuous wedge circuit...dynode feedback logarithmic amplifier and a cor - rection circuit The strip chart recorder is used for se recording densitometer, so se instruments are more time-saving, and more proper for routine sensitometry than ors. Externals of T-54 and R-55 are shown in Figs. 1, 2 and Figs. 3, 4, respectively. * The authors already reported o n T-54, at Meeting of Soc. Sci. Phot. Japan, 1954).

3 No. 4-5, Dec., 1955AUTOMATIC 1 Front view 3 Front view of of RECORDING DENSITOMETERS T-54 R strip Procedure stand Mcdel for T-54: about of Chassis ct Side view cf cover and side T-54 R-55 plate with remcved measurement After switching electrical circuit half an hcur, in crder to be warmed index of recorder control panel 37 is adjusted to zero pcint ( 1), and sensitivity is on, up and by turning controlled instrument stabilized, is allcwed and n to a kncb set up on right cf by means of a standardized wedge. cide A sample with strip, clamped on strip holder so that a mark of hcider may coinone of sample, is measured always starting frcm pcint which gives a definite leg E value. recording value. pen Then is situated By pressing a starting synchronously by means begins to be recorded. When measurement cn position a position buttcn, cf each of of sample synchronous is over, four chart paper paper is corresponding strip and chart motor, whereupon electrical relays operate adjusted, to so that definite lcg E paper move accurately a characteristic curve automatically, so that

4 38 M. TAJIMA & S. OUYEBull. Soc. Sci. Phot. JaPan. recording pen may be lifted from chart paper, paper may stop, strip holder may return to initial position, and stop. The strip is removed. All se processes require about 1 min. 40 sec. The procedure using R-55 recording densitometer is similar to that using T Optical system of transmission recording densitometer ( T-54) 6 Optical system of reflection recording densitometer ( R-55) The optical system The optical system of transmission densitometer is shown in 5. and that

5 No. 4 `5, Dec., 1955AUTOMATIC RECORDING DENSITOMETERS 39 of reflection densitometer in 6. In each system, we adopted a relay condenser system, that projects a slit image on photographic image, minifying into area of 0.5 ~1 mm. The electrical system Since output current from photoelectric detector is nearly proportional to intensity of light incidented on phototube, an electrical device as follows is necessary in order to obtain an output being in direct proportion to photographic density. (A) Some logarithmic amplifier. (B) The null method with an intensity control mechanism6.15) The dynode feedback circuit was used in each densitometer of T-54Yand R-55. However, because output current is not in direct proportion to photographic density by this circuit only, a functional resistance was used in electronic potentiometer for correction. By this correcting method, higher accuracy and greater ease were obtained than by or ordinary method16). 7 shows block diagram of amplifier. 7 Block diagram of amplifier The sample and wedge Test strips to be measured by transmission densitometer T-54 have a width of 10 to 45 mm and an efficacy length of 120 mm, and prepared so that ir range of logarithmic exposure varies from 0.00 to.4.80 linearly during 120 mm. Not only photographic plate but film can be measured by T-54 densitometer. An efficacy length of test strip to be measured by reflection densitometer R-55 is same 120 mm as T-54 densitometer, but range of exposure is log E=3.00 during 120 mm. These test strips are measured running on slit image of 0.5 x 1 mm. The optical wedges for sensitometric exposure are a continuous type with a difference of optical density between maximum and minimum, dd =4.8 and 3.0, respectively, for T-54 and R-55. These optical wedges must vary by same rate of density as constant distance on those. But, even if ratio of distance to density (D) is below 120-! 4 mm to dd =4.8 or 3.0, it can be corrected by changing gear.

6 40 M. TAJIMA & S. OUYE Bull. Soc. Sci. Phot. Japan The sensitometric wedge for T-54 was made bymr. S. Fukushima by casting method. 8 shows example of measurements. 8 Example of measurements. A rise in middle of curve (developed for 8 min.) shows how faithfully this densitometer recorded defect of sensitcmetric strips. Special applications 1) As a recording color densitometer: These automatic recording densitometers can be used as a recording color densitometer with three color filters of red, green and blue in place of opal glass. 2) As a microphotometer: These automatic recording densitometers can be used as a microphotometer by illuminating an extremely narrow area with a smaller slit than normal size. Making scanning speed down to 10 mm/min., it is possible to record faithfully sudden change of a density value to very short distance on specimen. 3) As a small density difference meter: It is required frequently to detect a slight and a sectional difference of photographic density, or to measure slight growth of density such as by printingout effect17). Or ordinary densitometers can not distinguish a smaller difference of density than On contrary, difference of density can be detected and recorded by adding a simple electric circuit to T-54 or R-55. These measurements mean no increase by an efficacy figure but difference of density. Conclusion In this paper T-54 of transmission recording densitometer and R-55 of reflection recording densitometer have been described. No trouble has arisen on practical use during two years since that time. We wish to shorten recording time to less than five minutes for measuring one sample using reflection densitometer. It will be obtained by raising dynamic character, in or words by making sensitive response of densitometer.

7 No. 4 `-5, Dec., 1955 AUTOAIATIC RECORDING DENSITOIIIETERS 41 There is anor defect, that three traces are confused in recording color density. We are framing next trial instrument which can draw with three color inks corresponding to three filters. Acknowledgment The authors wish to express ir indebtedness to Dr. S. Fujisawa, head of Research Laboratory, Fuji Photo Film Co., Ltd., to Mr. M. Terao who instructed us,_ and to Dr. Z. Koana, Professor at Tokyo University, who designed optical system_ of reflection densitometer for authors. LITERATURE 1. R. H. HIJBER and A. B. RA KITS: J. Opt. Soc. Amer., 39, 873 (1949) 2. M. H. SWEET: J. Soc. Motion Picture Television Engrs., 51, 35 (1950) 3. K. G. MACLEISH: ibid., (1953) 4. O. L. GOBLE: J. Sci. Instr., 30, 110 (1953) 5. H. G. FAIRWEATHER: Brit. P., 601, C. TUTTLE: J. Opt. Soc. Amer., 2G, 282 (1936) 7. R. PINOIR and M. RABAL: Science et inds. phot., 25, 87 (1954) 8. J. ROULLEALT and A. CORRIEZ: ibid., 15, 12 (1944) 9. J. G. FRAYNE and G. R. CRANE: J. Soc. Motion Picture Television Engrs., 45, 370 (1945) 10. J. C. M. BRENTALS: Rev. Sci. Instr., 16, 309 (1945) 11. A. V ASSEY et E. VASSEY: Science et inds. phot., 19, 56 (1948) 12. A. TAYLOR: J. Sci. Instr., 28, 200 (1951) 13. L. LUNDIN: Arkiv Fysik, 4, 391 (1952) 14. R. I. TAIT and F. C. CHALKLIN: J. Sci. Instr., 30, 268 (1953) 15. C. A. MORRISON: J. Opt. Soc. Amer., 42, 90 (1952) 16. M. H. SWEET: ibid., 37, 432 (1947) 17. E. KATZ: Physica, 7, 755 (1942)