DE2218150C3 - Device for determining the integral optical density of an object with a heterogeneous structure - Google Patents

Description

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The invention relates to an apparatus for determining the integral optical density of a Object of heterogeneous structure with a light source, projection optics for projecting the Object on a photodetector and a device arranged in front of the photodetector for simultaneous Logarithmization of the luminous flux of the individual pixels of the object.

A device of this type is in a special print from "75 years of optical measuring instruments" (1968), P. 77 to 81, Carl Zeiß, number S 34-260 Scho. IX / 68 Poo., Described. With this known Vorichtung is in the projection path for the light from the light source to the photodetector between the Light source on the one hand and the projection optics or parts thereof on the other hand a photo plate with a photographic recording of the object to be examined inserted. The known device requires In any case, as a preparatory step, the production of a photographic record of the to Examining object, on the basis of which the actual measurement can only then be carried out. In addition, the desired logarithmic characteristic for the Realize light sensitivity with a photo plate only very approximately, so that, apart from the Cumbersome time-consuming preparation of the measurement, also its result in terms of its accuracy not able to fully satisfy.

The invention is therefore based on the object, a device of the type mentioned in the Way to train that they can carry out the measurement in a time-saving manner directly on the object to be examined itself and with the achievement of high measurement accuracy without the use of complicated mechanical or electronic computing systems.

The "set problem is achieved according to the invention in that the device for simultaneous Loeariihmierung of the luminous flux of the individual pixels of the object from behind the projection optics arranged electronic image converter with a luminescent screen with logarithmic ^ - electron current-luminance characteristic consists.

The device designed according to the invention thus makes use of the object of interest on the one hand itself as an immediate object of measurement, and it delivers thanks to the high accuracy in the coincidence between the desired logarithmic curve on the one hand and the luminance characteristics of the used electronic image converter on the other hand, measurement results of very high accuracy. on In this way, the device designed according to the invention enables the measuring times for the density determination to reduce and arithmetic operations such as logarithmizing and integrating in the determination to completely exclude the integral optical density of the respective object. In addition, the In accordance with the invention, no expensive and complicated mechanical and electronic devices are required Systems and still leads to a high measurement accuracy.

A preferred embodiment for a device designed according to the invention is characterized in that the luminescent screen of the image converter contains a material with the following chemical composition as the active substance: manganese 0.17 percent by weight. Cobalt 3 · K) ⁴ percent by weight and zinc sulfide 99.82 percent by weight.

For the further explanation of the invention, reference is now made to the drawing in which an embodiment is shown; shows in detail in the drawing

Fig.! a device for determining the integral optical density in the form of a block diagram and

Fig. 2 graphs of! Ogarilhmischen Dependencies for explaining the mode of operation of the device from FIG. 1.

The device shown in Fig. 1 for determining the integral optical density of objects with heterogeneous structure contains along a optical axis 1 arranged one behind the other a light source 2, a projection optics 3 with a table for setting up the respective object, a diaphragm 4 to limit the measuring zone, an electronic one Image converter 5 with a luminescent screen which has a logarithmic electron sirom luminance characteristic guaranteed for the image converter 5, and an image receiver 6.

In the given case, a secondary electron multiplier is used as the image receiver 6.

As a diaphragm 4, an iris diaphragm, any invariable diaphragm or the entrance window of the electronic imager 5 is used.

Any known electronic image converter with a luminescent screen which has a logarithmic electron current-luminance characteristic can be used as the electronic image converter 5. As an example of such a coating, a material may be mentioned which has the following composition: 0.17 weight percent of manganese, cobalt 3 x 10 ~ ⁴ weight percent zinc sulfide and 99.82 percent by weight.

A Rol-yellow light filler is set up in the beam path behind the luminescent screen.

When measuring micro-objects, e.g. B. from biological cells, a monochromator in connection with a microscope can be used as projection optics 3 can be used in transmitted light and in the bright field when measuring. Objects in the form of Photo plates, photographic films, chromatograms and the like can be provided by projection optics 3 with folo lenses to be used.

In Fig. 2 the logarithmic function Ig / of the light form and the electron current-luminous density characteristic /, (/) for the electrical image converter 5 is shown.

The integral optical density D of the respective object in a limited zone can be expressed by the following formula:

niche image converter by a constant quantity ß, so it applies

From (l), (2) and (3) it follows

D = J [A - Ig /) ds = J [A - Z ₁ + ßld.s
.s

= [A + B) s - J /, ds

d.s.

/ "= Strength of the luminous flux that hits the object and falls on the medium.

/ = Strength of the luminous flux passing through the limited zone in its different points has stepped

s = area of the delimited zone.
The expression Ig ~~ can be in the form of the relationship

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lg / ₀ - Ig / = A - Ig /

(2)

in which A is a constant.

Like F i g. 2 shows, the function Ig / in the interval from I to I ₀ differs from the electron current-luminance characteristic /, (/) of the electro-Then it is necessary to obtain a quantity proportional to the integral optical density of the respective object, two Make measurements of the luminance on the luminescent screen of the electronic image converter 5.

In accordance with the foregoing, the method shown in FIG. 1 device shown the following Functionality:

The object illuminated by the light source 2 is with the aid of the projection optics 3 on the projected light-sensitive surface of the electronic image converter 5. The object image is created with the Aperture 4 limited.

In this case, a part of the background on which the object lies is located within the diaphragm 4.

The luminous flux from the luminescent screen of the electronic image converter 5 is passed through the image receiver 6, and its size is proportional to the second term of expression (4). After that, will on the light-sensitive surface of the electronic image converter 5 only the one with the same aperture 4 limited background projected without an object and, in turn, the luminous flux by means of the image receiver 6 registered. In this case the magnitude of the luminous flux is the first term of expression (4) proportional. The difference between the luminous fluxes then becomes that of the integral optical density of the respective object proportional size determined.

1 sheet of drawings

Claims (2)

Patent claims: I. Apparatus for determining the integral optical density of an object of heterogeneous Structure with a light source, projection optics for projecting the object onto a photodetector and a device arranged in front of the photodetector for simultaneous logarithmization of the luminous flux of the individual pixels of the object, characterized in that the device for simultaneous logarithing the luminous flux of the individual pixels of the object from an electronic projection screen arranged behind the projection optics (3) ler (5) with a luminescent screen with a logarithmic mixer Electron current-luminance characteristic exists. 2. Vorrichlung according to claim I, characterized in that the luminescent screen of the image converter (5) contains a material with the following chemical composition as the active substance: manganese 0.17 percent by weight. Cobalt 3 ■ KK ⁴ percent by weight and zinc sulfide 99.82 percent by weight.