Abstract

It is shown that the temperature-dependence of the luminescent efficiency of numerous phosphors may be used for the observation, measurement, and recording of temperatures and temperature distributions. Remarkably high temperature-sensitivities can be obtained by exciting the phosphors under such conditions that their efficiency is far below the optimal efficiency obtainable with the same phosphors. Thus, they are used under conditions which are most unfavorable for any other practical application and for most investigations. In particular, the strong temperature-dependence of superlinear phosphors, and the variation of this dependence with the exciting intensity, have been used for the development of thermometric and thermographic methods.

Two methods are described: In the first, the surface to be observed is coated with a luminescent material and evenly illuminated with ultraviolet radiation. The temperature distribution on the surface of the object under test becomes visible as a pattern of brightness or color of the luminescent coating. This pattern can be observed visually, measured by visual or photoelectric photometry, or recorded photographically. The result may be displayed in various ways. Isotherm charts can be obtained easily by purely photographic means. In the second method, a temperature-sensitive phosphor screen is placed in the focus of a suitable optical system. An image of the distribution of the thermal radiation from the object becomes visible on the screen as a brightness pattern which is easily recorded photographically and on which measurements can be carried out. While the second method does not require any coating of the object, the first is by far the more sensitive. A number of pictures illustrating the two methods and a discussion of their performance are given.

© 1949 Optical Society of America

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References

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  1. H. W. Leverenz, R.C.A. Review,  7, 238 (1947).
  2. Nail, Urbach, and Pearlman, “New Observations on Super-linear Luminescence,” J. Opt. Soc. Am. 39, 690 (1949).
    [Crossref] [PubMed]
  3. At the New York Meeting of the Society, a short motion-picture film corresponding to the sequences of Figs. 5 and 8, the latter in color, was shown.

1949 (1)

1947 (1)

H. W. Leverenz, R.C.A. Review,  7, 238 (1947).

J. Opt. Soc. Am. (1)

R.C.A. Review (1)

H. W. Leverenz, R.C.A. Review,  7, 238 (1947).

Other (1)

At the New York Meeting of the Society, a short motion-picture film corresponding to the sequences of Figs. 5 and 8, the latter in color, was shown.

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Figures (15)

F. 1
F. 1

Dependence of luminescent intensity upon temperature (from Leverenz).

F. 2
F. 2

Temperature-dependence of efficiency for a zinc-cadmium sulfide phosphor: 50% ZnS, 50% CdS, 2% NaCl, 400 ppm Ag, 1.0 ppm Ni. Fired at 1090°C for 30 minutes. Excited by 365 mµ.

F. 3a
F. 3a

Device for calibrating temperature-sensitive phosphors (in room light).

F. 3b
F. 3b

Device for calibrating temperature-sensitive phosphors (under ultraviolet radiation).

F. 4
F. 4

Arrangement for studying air stream impinging upon phosphor screen. Nozzle can be moved by a pinion from contact with screen to six inches away.

F. 5
F. 5

Thermal effect of air stream impinging on back of phosphor screen. a. Phosphor screen under ultraviolet excitation. No air stream on surface. b. Air stream on. Nozzle approximately six inches from screen. c.-h. Air stream on. Nozzle moved successively closer to the screen. In Fig. 5h the nozzle is almost in contact with the screen.

F. 6
F. 6

High-contrast print of thermal pattern produced by air stream. Step wedge was used in printing for calibration. Numbers on steps are temperatures in degrees centigrade represented by the density of the step.

F. 7
F. 7

Isotherms on the screen obtained from set of prints similar to that in Fig. 6. Numbers are temperatures in degrees centigrade.

F. 8
F. 8

Glass still. a. As seen in room light. b. Condenser coated with phosphor. Seen under ultraviolet illumination. c. Still in operation; no cooling water. d. Still in operation; cooling water on; condenser beginning to function. e.-f. Same as d, but successively later stages.

F. 9
F. 9

Set-up for thermoradiography.

F. 10
F. 10

Thermoradiographs of soldering iron taken at temperatures indicated.

F. 11
F. 11

Glass diffusion pump. a. In room light. b. Thermoradiograph of pump in operation. c. Contact-thermograph of pump in operation.

F. 12
F. 12

Glass vacuum tube. a. Phosphor screen under ultraviolet illumination. b. Vacuum tube under room illumination. c. Thermoradiograph of tube with filament current on. d. Thermoradiograph of tube with one plate carrying rated current. e. Same as d, after several minutes of operation. f. Thermoradiograph of tube with both plates carrying rated current. Envelope of tube radiating.

F. 13
F. 13

Photographs by thermal radiation. All pictures taken in dark room at 28°C. Top: Hotplate and tea kettle. Bottom: Piece of ice.

F. 14
F. 14

Thermoradiograph of human hand taken against room background of 27°C.