IL26836A - Observation or photography devices in closed spaces and in particular in bubble chambers - Google Patents

Description

'JllOJl IHD Τ31Π]"Ί 'Π PATENT ATTORNEYS ■ D'DIDD ' ΙΠ11) PATENTS AND DESIGNS ORDINANCE SPECIFICATION IMPROVEMENTS IN OBSERVATION OR PHOTOGRAPHV DEVICES IN CLOSED SPACES AND IN PARTICULAR IN BUBBLE CHAMBERS yiaya *Rna ni»»a "mo na n^*sV i» mVanonV o^apnna o»>i¾aw J/We COMMISSAR! AT A L'ENERGIE ATOM I QUE, OF 29, SUE OE LA FEDERATION, PARIS 1 ε, FRANCE. do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement :- The present invention relates to devices for disclosing what takes place in a closed space and it is especially concerned with devices for photographing nuclear phenomenons in a dark closed space which is not accessible, such as a hot cell, a nuclear reactor channel, a ' Wilson chamber and, in particular, a bubble chamber.

The chief object of this invention is to improve said devices concerning the possible reduction of the observation or photography window provided in the wall of the chamber, the possibility of incorporating powerful illuminating means whieh do not produce parasitic light and the quality of the image.

Preliminary to setting forth the chief feature of the: invention the following definitions will be given: Being given a dioptrical system, consisting of one or several lenses and a diaphragm provided with a central hole, ei^call ciapc lar, located behind this dioptrical system, with reference to the direotion of propagation of light, The "rear pupil plane" is the plane of this diaphragm, and the "front pupil plane" is the image of the rear pupil plane given by said dioptrical system; Now, the present invention consists, according to the main feature of the present invention, in providing, in combination^ the following elements disposed behind one another, starting from the window, and centered on a common optical axis: - a first dioptrical system including a front l&ns the f¾ont face of which is flat, at least substantially, i.e. which may be slightly oonvex or slightly concave, and the rear face of which is in the form of a surface of the kind consisting of ellipsoidal and paraboloidal surfaces, this first dioptrical system being adapted to give . a virtual image of the inside of the ohamber and possibly consisting of the window thereof; said first dioptrical system, said illuminating system being preferably disposed substantially symmetrically about said common optical axis; - a "second dioptrical system, including several lenses, for transferring toward the rear the virtual image produced by the first dioptrical system and giving a real image of the inside of the space to be observed; - mask means consisting of a system of masks located in the vicinity of the image plane of the whole of the two above mentioned dioptrical systems for stopping substantially all the light rays from the illuminating system reflected by both of the faces of the lens of the first dioptrical system; and # a third dioptrical system, including several lenses, for transferring toward the rear the real image produced by the whole of the two first mentioned dioptrical systems and giving a real image located in a plane where is located a receiver.

Preferably, with such a device, forming both a wide angle objective having a great fiold depth and a periscope, there is combined, in the wall of the chamber to be observed, a window consisting of an optical glass meniscus the two faces of which are in the form of concentric spherical surfaces, the device being then disposed with respect to this window so that the common center of said spherical surfaces is at the point where the optical axis of the device intersects the front pupil plane, which, on the one hand, eliminates any disturbing reflection on the faces of the window and, on the other hand, reduces the aberrations and eliminates distortions due to the window, A Preferred embodiment of the present invention will be hereinafter described with reference to the appended drawings, given merely by way of example, and in which: The only figure is a sectional view, through the optical axis, of a device according to the present invention placed opposite the window of a bubble chamber. instance a mass 2 of liquid hydrogen and provided with a transparent window 3 consisting of a meniscus having an inner spherical face 4 and an outer spherical face 5 "both having their center at 6. The left hand portion (not shown) of chamber t is coated with a reflecting adhesive strip having the same optical properties as a catadioptrical surface (it reflects the light that strikes it in the incident direction which may be any direction).

The observation and/or photographic device according to the present invention, which constitutes both a wide angle objective (since the angle 2a of the most inclined incident rays 7 is generally greater than 100° and may reach 120-130°) of a focal length averaging mm and of great field depth and a periscope in view of its length which may reach and even exceed 1 meter, reaching for instance from 1.5 m to 2,5 m, comprises, starting from window 3, the following elements centered on optical axis 8: - a first dioptrical system including a lens 9 the front face 10 of which is shown flat, but may be slightly convex or concave, and the rear face 11 of which is in the form of an ellipsoid (or possibly of a paraboloid) of revolution, this system giving a virtual image of the inside of chamber 1 , *·> a diaphragm 12 ard, immediately in front of the rear pupil plane 13 of this diaphragm, an illumiioting system 14 directed toward the front through said first dioptrical system 9, said illuminating system 1 being disposed substantially symmetrically about optical axis 8; in particular, illuminating system 1 is located at a distance d from axis 8 such that the mask 12a which surrounds (and define£ said diaphragm 12 stops substantially all the light rays from illuminating system 1 that are reflected by faces 4 and 5 of window 3; - a second dioptrical system 1 iaoluding several lenses 16,17? 18, 19 for transferring toward the rear the virtual image given by the first dioptrical system 9 to form in the vicinity of plane 20 a real imago - a system of masks 21 , 22 disposed in the vicinity of the image plane 20 of the whole of the two dioptrical systems 9 and 15 to stop substantially -all the light rays from illuminating system 14 reflected by the faces 10 and 1 of lens 9j and - a third dioptrical system 23, including several lenses 24,25, 26, 27, 28, for transferring toward the rear the real image produced by the two first dioptrical systems 9 and 15 to give a real imago in a plane 29 where is located an optical receiver (an observer's eye, a photographic plate or film, the mosaic of a television transmitter, etc.).

In a preferred embodiment of the invention, given by way of example, both of the spherical faces 4 and 5 of window 3 have their center at 6 where optical axis 8 intersects the front pupil plane 6a of diaphragm 12 (through lens 9), and lens 9 has a flat front face 10 and an ellipsoidal rear face 11, the focus of the ellipsoid that is at the greater distance therefrom' being located at 30, where optical axis 8 intersects the rear pupil plane 13.

When the face 11 of lens 9 is a portion of a paraboloid of revolution, point 6 is the image of the remote focus 30 through lens 9 and, in this case, the distance between point 30 and 3jBns 9 is preferably chosen to range between ten and twenty times the focal length of this lens.

Concerning the aberrations and distortions, it will be noted that when the faces 4 and 5 of window 3 have their common center at a point 6 in the front pupil plane 6a, this window produces no aberration with the exception of a slight spherical aberration and of a field curvature, which can easily be corrected by means of dioptrical systems 15 and 23, calculated to correct also the aberrations introduced by Ions 9.

It will ' also be noted that since the face 11 of lens 9 has a longitudinal section in the sha e of an elli se or ossibl a arabol) great angle, like ray 7 > with optical axis 8, gives, when its cross section tends toward zero, an excellent image, which would not be the case if face 11 had a different longitudinal section. This is the case of a stigmatism for any ray (the sagittal and J aagential focal lines being confounded for this radius) and not of a stigmatism within the scope of the convential Gauss approximation (for rays little inclined with respect to the axis). Finally, lens 9 has pupil aberration (which means that it expands the entrance pupil gradually as. -the distance from the optical axis 8 is greater) so that the illumination of the final image, in plane 29 , of an elementary area ds seen under an angle b from optical axis 8 is of the order of magnitude of EQ cos b, if E is the illumination of the final image of an area of the same size and luminance as area ds but which would be seen under an angle b = 0,' instead of the usual law E = ΕoΛ cos b,7 so that there is obtained a more uniform illumination of the image in plane 9 for an object of uniform luminance.

The illuminating source 1 consists advantageously of a tore-shaped flash tube, but it may comprise several electric bulls disposed in an annular row surrounding optical axis 8.

Masks 21 and 22 (which have the shape of circular annular elements, as shown, in the case of a tore-shaped flash tube) may be advantageously made as follows. ¾ro photographic filns or plates are placed in the planes 3 and 32 where said masks are to be located and the illuminating system 1 is brought into operation, the whole of the device being in position. The light rays from said illuminating system 14 not only illuminate the inside of chamber 1 , passing successively through faces 11 , 10 , 5 and 4, but also undergo parasitic reflections on these faces. The rays that have passed through lens 9 from the rear toward the front form an image of the flash tube in the front pupil plane 6a in the vicinity of point 6 and the rays transmitted from this image extend substantially normally to the and 5 are finally stopped by mask 12a, which limits diaphragm 2. As for the rays from flash tube 1 reflected by faces 11 and 10, they pass through diaphragm 12 and dioptrical system 15 and transfer into planes 31 and 32 the images of flash tube in "mirrors" 11 and 10. These images sensitize the photographic films or plates placed in said planes and cause the silver salt or other sensitive substance of said films or plates to be blackened or otherwise acted upon. It is then possible to use as masks either these blackened films or plates or screens obtained by transferring in any suitable manner these blackened pictures onto other supports or, again, screens having dimensions equal to, or slightly greater than, those measured on the blackened films or plates. In view of the fact that, as a rule, reflections on window 3 have no effect on the determination of the dimensions of masks 21 and 22, these masks can be determined without the device being disposed in front of the window of abubble chamber.

The drawing shows the paths of travel of two extreme rays , to wit a ray 7 of maximum inclinations a and an axial ray 33 passing close to the limit of diaphragm 12.

The device according to this invention has, over existing devices used for the same purpose, many advantages among which the following ones may be cited.

First, it constitutes a wide angle objective without distortion and having a great field depth.

It has an entrance pupil at the front which permits of reducing the size of the chamber window, which is very interesting in the case of bubble chambers.

The front lens 9 of the device may even constitute, if this is useful, the window.

The exit pupil is remote from the image plane of the front lens 9 which permits easy image transfers. The device therefore consti tutes a periscope the length of which may reach or exceed 1m and reach The device includes an illuminating system, in particular m an annular flash tube, located after the front lens.

The parasitic lights are excluded and the effect of illumination is correct, even for incident rays very much inclined with respect to the optical axis.

Since the objective is a wide angle objective with a great depth of field, it is possible to obtain, with a window of moderate size, a good image of the whole inside space of a large size chamber, in particular of the whole of the bubbles formed along the paths of the trajectories of the charged particles in a large size bubble chamber, the illuminating system 14 being brought into play in synchronis with the starting of the operation of the bubble chamber.

In a general manner, while the above description discloses what is deemed to be a practical and efficient embodiment of the present invention, said invention is not limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the invention as comprehended within the scope of the appended claims.

Claims (1)

HAVING MOW PARTICULARLY DESCRIBED AND A30ERTAINE0 (THE NATURE OF OUR 8AID INVENTION A^ IN -WHAT MANNER THE SAME IS TO BE PERFORMED, WE DECLARE THAT WHAT WE CLAIM 18: ¾P - WHAT WE CLAIM IS : , A device for disclosing through a window what takes place in a closed space, and in particular in a bubble chamber, characterized in that it comprises, in combination, the following elements disposed behind one another, starting from said window, - a first dioptrical system including a front lens the front face of which is flat, at least substantially, i.e. which may be slightly convex or slightly concave, and the rear face of which is in the form of a surface of the kind consisting of ellipsoidal and paraboloidal surfaces, this first dioptrical system being adapted to give a virtual image of the inside of the chamber and possibly consisting of the window thereof; - a diaphragm and, immediately in front of the rear pupil plane of this diaphragm, a system of illumination toward the front through said first dioptrical system, said illuminating system being preferably disposed substantially symmetrically about said common optical axis; - a second' dioptrical system?including several lenses, for transferring toward the rear the virtual image produced by the first dioptrical system and giving a real image of the inside of the space to be observed; mask means consisting of a system of masks located in the vicinity of the image plane of the whole of the two above mentioned dioptrical systems for stopping substantially all the light rays from the illuminating system reflected by both of the faces, of the lens of the first dioptrical system; 'and - a third dtptrical system, including several lenses, for transferring toward the rear the real image produced by the whole of the two first mentioned dioptrical systems and giving a real image located in a plane where is located a receiver. 2. A device according to claim 1 further characterized-dn that th.e longitudinal section of the rear fac/o of the front lens of said first dioptrical system is a portion of an ellipse the respective foci of which are located in the front and rear pupil planes of said diaphragm. 3. A device according to claim 1 further characterized in, that the illuminating system consists of a tore-shaped flash tube and the system of masks comprises circular annular shaped elements. 4. A device according to claim 1 further characterized in' that said masks located in the vicinity of the image plane of the whole of said two first mentioned dioptrical systems are made from photo-sensitive elements placed in the planes of said masks and sensitized by operation of said illuminating system. 5· In combination with a system according to claim 1, a window for a vessel limiting said closed space, characterized in that it is made of an optical glass meniscus both of thefaces of which are in the form of portions of concentric spheres, said device being disposed so that the point' where the optical axis of said device intersects the front pupil plane coincides with the common center of thefaces of said meniscus. 6. A combination according to claim 5 further characterized in that said illuminating system comprises a tore-shaped element the mean radius of which is such that said mask means surrounding said diaphragm stops substantially all the light rays from said illuminating system and reflected by said window faces. 7. A device according to any of the preceding claims and substantially as illustrated by the accompanying drawings. DATED THIS 8ΤΗ OAV OF NOVEMBER 1966

1.10.66-ST.