DE1889093U - IMAGE CONVERTER TUBE. - Google Patents

Description

The innovation concerns an image converter tube in which airtight bulb near its entrance end and a photocathode near its exit end at a distance therefrom the image is provided by the secondary screen and also by electron-optical screens Means for directing emitted from the photocathode Photoelectrons are provided on the inside of the secondary screen. The secondary screen usually has fluorescent or luminescent character and leaves Appoint the image in question as soon as it is in operation, the tube is hit by photoelectrons. The 3ekundaj? Screen is here suitable for direct visual observation or can also serve to show the image pattern formed on it to be transferred to another device. Tubes of this general design are referred to as image converter tubes.

PROPo3144

Bine kind of image converter tubes - on which the / firing is in front of. all, but not exclusive, are so-called -. brightness intensifier or image intensifier tubes,. "as they are used - especially in" X-ray technology, in order to increase the brightness of a primary image generated by X-rays. \ _: '"", "'; ■■■ ν '-" .. ". .- ■ "■.:

Quite, generally, the task of the fire is to be based on the To improve the construction of image converter tubes., that the initial image of on dust; or other within. of hermetically sealed tubular piston existing contaminants Keep foreign bodies free from disturbances will. "". . '. ■ -.-.-- ■ -. ".." ■ --.-. ■ "- '... ■

In the manufacture of large-scale SlectrOnenröhrew · V there are many sources of contamination / which, despite all the care taken during manufacture, practically: cannot be avoided; "; let. Small! foreign bodies and dust particles of all kinds that float in the air of the ¥ erstatte, and often small; lint from the textile fabrics of the work clothing are electrically charged, then get into the tube before it is evacuated - and then adhere on the tube walls. by - electrostatic attraction and are finally permanently trapped in the ear. Fragments of: -metal and metal oxides from metal electrode soldering processes, which are carried out in the course, burden a further source of misalignment .. Frequent - a photo-emitting layer inside the tube after its airtight closure- through.'Verdampfungsnie ^ hit voÄ in ^: '^i; the tube, made of electrically, heated:, enclosed in the tube piston-

separate evaporation containers evaporated alkali metals, formed * Such processes lead-to that, within the airtight closed tube contaminating foreign bodies are present, such as peeled off the walls of the evaporator container and / or vaporized. Particles and generated by Feben reactions chemical compounds.- ; ; -. ·. ..

In the case of brightness intensifier tubes of z. B. for X-ray image intensification. used art. is another and particularly troublesome source of pollution from the presence of the Fluorescent layer given that. the outer surface of the primary or input screens of the tube covered. The ones in such. Fluorescent layers used in tubes contain relatively fragile constituents., and particles are able to to be peeled off from them during the operation of the tube.

With regard to the brightness gain brought about by ..such an image converter tube is brought about, and the op-. table enlargement of yours through an optical device. or other. The means of observation of the output image viewed is the; . Presence of any such foreign objects, which are on or behind the surface of the tube's home screen. can put on the screen as. a stain is visible and therefore seriously affects the usability of the device.

For these reasons, certain sensitive image converter tubes such as :, orthicons used in television cameras, require _; 1 that they are treated carefully and only in a Hörigontal / eii-. - ^;

.läge or at a small angle m DER, horizontal plane ■ ■ being operable to settling-von.Schwebteilchen a cloud within the tube, zti avoid, which settle on and behind the output screen and so _that; Could spoil the picture. This is "a serious restriction on the mode of operation of such a tube and completely unacceptable in many applications, such as in particular with high-altitude image intensifier tubes, since, for example, medical X-ray work" must usually be carried out in any orientation of the tube, including its vertical position.

The task of the firing is now to create an image converter tube of the type mentioned at the beginning, which allows all the aforementioned difficulties and limitations to be avoided by clearly preventing any foreign bodies that are inevitable in an image converter tube from looking at or behind the exit surface of the Image of the tubes-supplying secondary shield. Of the tube. Above all in the case of picture tubes, which are equipped with a fluorescent primary screen that provides images, the objective of the firing also clearly includes any foreign bodies that can be copied from the fluorescent surface, to prevent them from entering the general tube cavity, from where they can 'settle on or behind the secondary screen.'"ν ..-. . ,. . . . ^! ;

This task; is . at "the back before it chi ag exien -Bi Idwand5.eröhre of the ^ G-attung defined at the beginning; Vbr." allem da- --- "solved by that according to the! firing .between the secondary screen and the Output end.des tubular piston an annular ^r

This dust shield is arranged with an edge piece facing the seal underneath the shield and a further edge area that sits tightly on the inside of the tube. This dust shield separates the space enclosed between the secondary shield and the outlet end, the tubular bulb, in a sealing manner. the general cavity of the tubular piston against the entry of foreign particles. ^: . - ■ ",: ..". - ■ ■■ ". ^V _; '. .-

Another feature of the innovation, especially for X-ray image intensifier tubes and the like. is applicable, the photocathode is on the output string of a supplying the image. Primary screen is provided, the one on the input side by a protective shield permeable to incoming rays. Has a covered. Fluorescent layer and the primary screen has sealing means with a pair of flanged, ring-shaped support members, one of which has flanges on the circumferential areas of the protective screen or the photoemission layer. The photocathode rests on the surface and whose ajader plan protrudes from this support plane, and furthermore an annular sealing strip with a generally U-shaped cross-section is provided, the legs of which lie sealingly on the two protruding support members training is completed. called fluorescent layer of the general. cavity of the .. \ tube piston against outbreaks of fluorescent.! particles in the piston cavity sealing. .. / ~

Other features of the proposed mifeder control ■. ^: . ^: . Bildvifandlerrahre go out of the-Zeilehnang hsrviar · ', ^ die - ■ one-. ". -". "

Image converter tube of the type proposed here in an embodiment selected as an example, schematically illustrated in section. 1 shows, in a cross section, in which certain dimensions are exaggerated for the sake of clarity: a primary or input screen for a brightness intensifier tube according to the innovation, FIG. 2 also brings the exit end of the same tube in a cross section with partially falsified dimensions and reveals the secondary or exit screen, which is equipped with the dust shield according to the innovation. Finally, FIG. simplified on a smaller scale represents the image intensifier tube ,, which is connected to the two in ^ ¹ Ig, 1 and 2 equipped in detail illustrated improvements ..., except for the fact the .Röhre has been limited in the manner of representation on the main components. . .

The tube according to the innovation will now be explained using an X-ray image intensifier tube. The tube shown in FIG. 3 has an airtight, evacuated glass bulb 27. A primary screen is provided, which is here generally designated by 28, expediently supported in the bulb near its inlet end, which is at the top here. This primary screen, which is described in detail in connection with FIG. 1, has a fluorescent layer 2 on its entrance or top side and a photoemission layer 3 on its exit or bottom side, which forms the photocathode. Within the spatially restricted output end, which is below here, a secondary or output screen 32 is arranged in the tubular piston 27, which is illustrated in detail in Fig-, and will also be described

will. The Selaindärschirm has on its entrance, - 'or -. Top side a fluorescent layer ... 1-7 "· -'-. '■ .- ■" ..- "

A system of ring-shaped electron optics. Electrodes are provided coaxially between the primary screen 28 and the secondary screen 32. These electrodes, shown schematically under the reference numbers 29, 30, 31 and 40, are in operation of the tube at certain potentials for the purpose of focusing one of the photo emission layers 3 of the primary screen 28 ^: on the fluorescent layer, 17 of the Secondary screen. 32 emitted photo electron beam connected. ". '"'; ■

The general mode of operation of the tube is. The following X-rays impinging on the fluorescent layer.2 'of the primary screen 28 excite a fluorescent effect j. and the resulting photons hit the photo emission layer. ^ or photocathode 3 of the primary screen. Thus photoelectrons are emitted in a pattern that corresponds to the original X-ray MId. These photoelectrons are accelerated and at the same time by the effect _; the jUlektrodensystems 29 - .30, 31 and 40 accelerates to the secondary screen 32zu * The 'Photo electron excite the Kuor-it ^^ zenzoberf laugh 17 ^of: - Sekundärsch ^ irms 32 and depict an image -the exactly the original X-ray image corresponds to 'but'. . reduced '■' - "■ G-ize and substantially increased .Helligkeit aufweist.Wenn a" such imaged on the screen 32 Bild.durch one-amplifying optical G et up instrument betraöhtet: ,, _is: to -his, .ursprüngli - to restore chen dimensions - soiifc. the gain in brightness or luminescence about several thousand times, greater, -.

than before * -Instead of looking directly at the image also in other ways, e.g. photographically, kineinate— be evaluated graphically or on the Bernsehweg. -'- ■.

It is easy to explain that any small; Foreign bodies which have entered the between the secondary screen 32 and the wall of the tubular bulb. 27 penetrate the enclosed space "to serious" spots on the exit sM Id. Especially after its reinforcement. ¥ enn ^: themselves such. Foreign particles either on ... the exit side of the "secondary... Screen. 32" or on the inner surface of the. 27 drop, they project highly contrasting shadows that seriously affect the quality of the "observed image, even if the lights that cast the Sß'ha, kittens are very small. It is just as easy to understand that the dropping of lights on - . the input side of Sekundärechirms 32 much less, is troublesome because the incident photoelectron beam ge.den point of the fluorescent layer 17 applies within a wide range of angles of incidence, so that geVsTöhnlich a considerable number _of. electrons is present which DIE fluorescent. Emission of the layer in a. .Under such a ώτΈτβ rmäkkör ^ er lying area excited. "- ■" ■ "_. -. . - ".: - ■ - ;.

The sources of contaminating foreign bodies in the tube, are manifold and inevitable · .-. They include. Dust particles, who are in the-v '/ workshop air and electrostatically, charged, so that they are not moved out when the tube is evacuated can be «In them there are also: fragments of. Me-. ■ -tall- and oxides. säwie. other- constituents; ^ 'die- per- fes

Evaporation impact of the photocathode layer 3 can be generated on the screen 28 after the tube has been hermetically sealed from the evaporation containers, not shown here, which can be arranged in the specially designed central electrode 31 . Perhaps the main source of contamination within the tube is in the fluorescent layer 2 of the primary screen 28. The fluorescent layer used in certain applications contains quite fragile components and pieces of tin containing tin tend to be peeled off from it. These fragments, which additionally impair the output image, can also have a detrimental effect on the photoemission properties of the photocathode layer 3 on the lower surface of the primary screen 28.

Fig. 1 shows in detail the structure of the primary screen 28 according to the hiring. It has a thin, curved glass plate 1 with the aforementioned photo-emissive layer forming the photo-cathode J, which is provided on its lower surface, preferably is produced by evaporation precipitation within the airtight tube. The upper surface of the Glass plate 1 trqgj; the fluorescent layer 2 having a suitable Composition to be excited by X-rays. The lower surface of the plate 1 is' over an intermediate annular electrode 4, which serves to connect to the Photocathode 3 apply an operating potential to the upper surface of the inwardly protruding flange of an inner ring-

angled. ■

shaped, a 4uerschmitt-exhibiting and from the corresponding Metal-made support member 6 attached. The primary electrode also has a thin aluminum foil 7, which is transparent to incident X-rays, in the same curvature as that Glass plate 1 arched and above the upper surface of the flu-

_..::;:; ■ -: ■ ^'[v - - 10 ■■■■;; ■■ = "■ ■■■ ■■■ v

orescence layer 2 is arranged in. slight abstajid ..: 'The purpose of this aluminum childes / orders mainly, dariii, on the primary screen a greater amount of through the. Fluorescent layer 2 in upward direction - .. emitted. To reflect back photons and thereby increase the effectiveness of the primary screen. The peripheral portion of the aluminum, sheet 7 is of the lower surface by a innen.gerichteten -Plansehes äusseren.ringförmigen nozzle member: 5 "■ loading strengthens that was its t s ^ tone of the inner wall of the ^{Rohrenkolhens.:.} ÜTDer an Eoyar power or the like is aiD-supported. - ■ ■ ^.: .. ^:

The annular support members 5 ^ M 6 Ioesitzen ... downwardly projecting flanges 8 and 12, whereby.der flange 12 of the inner support member, β lies within the flange 8 of the outer support member 5. In Fig. 1 is of course the-. ■ ■ - .. space between the individual ropes for reasons of clarity; is exaggerated. In fact, the inner flanged support member is inserted into the outer support member 5 with only a small gap. In practice, however, it has been found that even ^{such a small margin:} for example in the order of 0.2 mm. Radius is sufficient to remove small fragments of the less stable components of the X-ray sensitive fluorescent layer 2 in the intermediate area around the flanges 8 and 12; the support member, the 5 and 6 to enter. . . - .... /. .;

According to the fire, the transition of such fragments will be through the intermediate space between, the flanges 8 and 12. in. the / ■

general cavity - of the tube cage ens by the fact that an annular, preferably made of thin aluminum foil of ... " z. B. 0.05 mm thick sealing strip '10U-shaped cross-section is provided outer leg 9 on the inner surface of the - to be ^ ussenflansches 8 and diiö'ht with its inner legs 11 on the inner surface of the inner flange 12. Thus, "causes the seal Star tire 10 that intercepted 2 escaped particles of the fluorescent layer and prevented", the secondary screen. 32 and / or the photocathode 3 to dirty.

The in ^ 'ig. Secondary screen 32 shown in detail in 2 has a flat glass plate 18 with a fluorescent layer 17 deposited on its upper surface 20 can be extensive. from the inner surface of the piston tube 27 by suitable means such as. B. a ^ JC ^ var-Dichiung ^ be worn. Has a metallic holding member 19 with an angled cross-section _; a lower flange attached to the outer circumference of the support member 20 by soldering points 21 and an inwardly protruding upper flange which overlaps the outer edge area of the fluorescent layer 17. An annular spring member 22 or a resilient washer is clamped between the upper surface of the fluorescent layer 17 and the lower surface of the upper flange of the retaining member 17 to resiliently hold the secondary screen against its retaining members. ...

^; . "..." At 24 the -ilaclren-shaped / support member '20 is soldered onto our surface around its inner rim area -hBrum \ the inverted upper 3-length 25 of a generally frustoconical, ring-shaped metallic dust shield 23 . The "wider base of this dust shield 25" has an upwardly turned rounded flange 26 which sits on the upper surface, the end wall of the tubular piston 27. The dust shield 23 effectively protects the shield between the secondary shield 32 . and the tube-col.benenäwanduhg enclosed skin, against the entry of foreign particles. In the manufacture of the tube it is an advantage that relatively broad tolerances are obtained in order to determine the point, . _an which the support member 20 is supported by the glass bulb, and ^since: the free space between the secondary plate panel 18 uad the Röhrenendwandungvon a - ^ eyelets to the other ^ may change the - lächgiebigkeit of the dust shield 23, particularly to the... The lower rounded flange 25 makes it possible to accommodate such different dimensions. The frustoconical shape of the stub shield 25. prevents undesirable light reflections from the luorescence 17 on the inner surfaces :, of the shield 23.. -ι - ... ^: - λ ^:: .: ". ::. 1 ^:

X-ray image intensifier tubes constructed in this way, which at the same time have both main features of control, namely the escape of fluorescent particles. the -._ ■ / - primary screen-hindering sealing strip. 10 ^: and .den the lin-. - .. ^ anybody steps from leilchen. Origin in the space. Below.

of the secondary screen 32 preventive & dust shield 23 have Excellent performance in terms of the purity, clarity and general quality of the output images you generate * The extraordinarily troublesome effects of trapped in the tube floating dust particles on the quality; of the image and resolution of all parts of the original image, a constant Source of interference for users of tubes of this general ■ -nen Kind so far, be at. of the tube proposed here, and there is no restriction on the handling and orientation of the tube in use. Of course the two improvements proposed here can also be used successfully separately from one another. Particularly In the case of image converter tubes that do not have a fluorescent layer on their primary screen, it goes without saying that the sealing strip 10 would be superfluous.

Claims (5)

- 14— S c h U-t ζ a η s ρ r ü c h e; - 1. Image converter tube, in the airtight bulb near its input end a photocathode and near its output end at a distance from this a secondary screen providing the image and also electron-optical means for. Direction from the photocathode emitted photoelectrons are provided on the inside of the secondary screen, characterized in that between the secondary screen (32) and the output end of the tube bulb (27) an annular dust shield (23) with a seal (24) opposite the circumference of the screen. standing edge piece (25) and a further, on the inside of the tube piston sealingly seated edge area is arranged. 2. Tube according to claim 1, characterized in that the Dust shield (23) is frustoconical and with his narrow base facing the secondary screen (32) and with its wider base facing the inner surface of the tubular piston (27) is.. . . 3. Tube according to claim 2, characterized in that the Dust shield (23) is designed to be resilient in such a way that it changes the distance between the secondary shield and the end wall of the tube housing (27) can compensate. "..., - ■ 15-- 4. Tube according to one of claims 1 Isis 3, characterized in that ; net that the photocathode (3) on. the - ^ outgoing side of a the image providing primary screen (28) is provided, "the one on the input side covered by a protective shield (-7) that is permeable to incoming rays (2) possesses and means with sealing the primary shield a pair of flanged ring-shaped support members (5, 6) has, one flange (5, 6) on the peripheral areas of the protective shield (7) or the. Photo emission layer the photocathode (.3) rests and its other flange (8, -. 12) from this level; .projects, - and; furthermore an annular "Generally U" shaped weatherstrip (10) .Cross-section is provided, the legs of which. (9,1-1), poetic on the two protruding support members (8, 1.2) - lie. 5. Tube according to claim 4, characterized in that: the sealing strip (.10). made of aluminum foil is.:. '.. "