US3510193A - Suppression of schlieren phenomena - Google Patents

Suppression of schlieren phenomena Download PDF

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Publication number
US3510193A
US3510193A US661173A US3510193DA US3510193A US 3510193 A US3510193 A US 3510193A US 661173 A US661173 A US 661173A US 3510193D A US3510193D A US 3510193DA US 3510193 A US3510193 A US 3510193A
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US
United States
Prior art keywords
schlieren
fluid
observation window
exposed surface
channel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US661173A
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English (en)
Inventor
Ulrich La Roche
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rheinmetall Air Defence AG
Rheinmetall Industrie AG
Original Assignee
Oerlikon Contraves AG
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Publication date
Application filed by Oerlikon Contraves AG filed Critical Oerlikon Contraves AG
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Publication of US3510193A publication Critical patent/US3510193A/en
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Expired - Lifetime legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0006—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means to keep optical surfaces clean, e.g. by preventing or removing dirt, stains, contamination, condensation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B17/00—Methods preventing fouling
    • B08B17/02—Preventing deposition of fouling or of dust

Definitions

  • Wall means defines an enclosed space which has a predetermined inner temperature.
  • An observation window is mounted in the wall means exposed to this inner temperature and has a surface which is located outside the space and is exposed to a body of fluid having a different temperature.
  • a nozzle structure is arranged adjacent the exposed surface and defines a fluid channel extending normal to the exposed surface and having an inner end adjacent to the exposed surface, and an annular gap communicating with the fluid channel so that, when suction is applied to the annular gap, fluid will be drawn through the channel in the direction against the exposed surface of the observation window and will thereupon be caused to flow across the observation window in radial direction and toward the marginal zones of the exposed surface.
  • This phenomenon can be very undesirable under certain circumstances, for instance if it is necessary to conduct observations through that zone of the fluid in which the phenomenon has developed.
  • the results obtained can be significantly affected in an adverse manner if such observation must be made through a schlieren-containing zone or region of fluid.
  • schlieren-containing zone or region of fluid It is of course known that there are differences in the size of schlieren, some of which are relatively small while others are much larger. It is particularly the relatively large schlieren which have been found objectionable under the circumstances just discussed because they decrease the contrast in the observation of relatively small objects or of objects which move rapidly with respect to their size.
  • the present invention overcomes the aforementioned problems. More particularly, the present invention inhibits the development of schlieren, and particularly of the relatively large schlieren, which, as mentioned before, have been found objectionable in optical observations.
  • I provide a method of inhibiting in a body of fluid which contacts the exposed surface of a solid body, the formation of the schlieren resulting from the existence of a temperture differential between the surface and the fluid.
  • My novel method comprises inducing the flow of a stream of the fluid in the direction against the exposed surface, and deflecting the stream of fluid adjacent the exposed surface so that it will flow in a plurality of directions along the surface and towards the marginal zones of the same.
  • My invention resides, however, not only in the aforedescribed method, but also in an arrangement for carrying out this method, and in this arrangement I provide wall means which defines an enclosed space having a predetermined inner temperature, and an observation window mounted in the wall means exposed to the predetermined temperature.
  • the observation window has a surface located outside the space and being exposed to a body of fluid which has a different temperature than the temperature prevailing within the enclosed space.
  • the stream of fluid will advantageously be caused to fiow in the direction normal to the exposed surface of the observation window, and will then be withdrawn in radial direction along the exposed surface toward the marginal zones thereof, advantageously by being subjected to suction.
  • application of my novel invention inhibits the schlieren formation and reduces the median size of the schlieren, that is of the turbulent inclusions which develop in the boundary layer as a result of the existing temperature differential between the fluid and the exposed surface.
  • the rate of flow of boundary layer fluid which is occasioned in accordance withthe present invention, is not so great as to result in the formation of turbulence.
  • a particularly important area of application for my novel invention is optical observation and/or measuring devices, particularly those which are used for observing and/or ranging of relatively small objects at relatively great distance.
  • the most sensitive optical and/or mechanical elements are arranged in a housing which frequently is maintained at a precisely controlled internal temperature and which is provided with an observation window extending transversely of the optical observation axis to which it is coaxial. It is this observation window which is to be protected against the formation of the schlieren phenomenon of the type discussed above.
  • FIG. 1 illustrates, in fragmentary section, one embodi ment of the invention in its most simple form
  • FIG. 2 is a view similar to FIG. 1, but illustrating a modified embodiment
  • FIG. 3 illustrates yet a further embodiment of the invention, also in a view substantially similar to FIG. 1;
  • FIG. 4 illustrates yet an additional embodiment of the invention in partly-sectioned, partly-diagrammatic form.
  • FIG. 1 DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail, and firstly FIG. 1 thereof, it will be seen that reference numeral indicates an optical observation window which is mounted in a wall means 11.
  • the wall means 11 should be understood to define or constitute a part of, a housing enclosing an internal space.
  • the optical axis of the observation window 10 is indicated by the line AA and arranged outwardly adjacent the outer exposed surface of the observation window 10, there is arranged inhibiting means for inhibiting the formation of schlieren, and particularly of large-sized schlieren.
  • This inhibiting means comprises, as FIG. 1 clearly shows, an annular body 12 which defines a channel 12a.
  • FIG. 1 shows that the channel 12a is coaxial with the optical axis A-A of the observation window 10.
  • the gap 13 further communicates with a conduit 14 which is connected to a diagrammatically illustrated suction device.
  • the latter need not be discussed in detail because suitable suction devices are well known to those skilled in the art and because the invention does not reside in details of such a device.
  • a body of fluid usually air
  • air is outwardly adjacent the wall means 11 and the outer exposed surface of the observation window 10, so that it surrounds the member 12.
  • a stream of this air will be aspirated through the channel 12a in the direction of the arrows and towards the exposed surface of the observation window 10.
  • the flow of air changes direction because of the suction exerted on it and flows across the exposed surface of the observation window 10 in radially outward direction towards and beyond the marginal Zones of the exposed surface.
  • new air is constantly being aspirated through the channel 12a in the direction of the arrows and it must be remembered that the suction exerted must be such that this new air will be aspirated with the minimum of possible turbulence as already indicated earlier.
  • the observation window is again assumed to be an optical observation window and is identified with reference numeral 20.
  • the wall defining the inner enclosed space, and on which the observation window is mounted, is identified with reference numeral 20a.
  • Member 22 corresponds to the member 12 of FIG. 1 and defines with the marginal zones of the exposed surface of the observation window 20 an annular gap 22b to the gap 13 shown in FIG. 1.
  • the gap 22b has an annular filter 23 arranged therein. This may be in the form of a strip of filter material which is, of course, airpermeable. The purpose of the filter 23 is to assure even and turbulence-free withdrawal of the air at all points of the circumference of the gap 22b.
  • FIG. '2 differs from that of FIG. 1 in yet another respect in that member 22 is provided adjacent the inner end of the passage 22a with an annular slot 25 which surrounds that portion of the member 22 which defines the channel 22a.
  • the slot 25 also communicates with the aspiration conduit 24, just as does the gap 22b, and the purpose of providing the slot 25 is to withdraw the boundary layer of air from the vicinity of the member 22 and of the wall means 20a so as to prevent it from being aspirated into the inlet end of the channel 22a.
  • This boundary layer air has already schlieren formed therein so that its aspiration into the channel 22a is not desirable.
  • reference numeral 3 indicates a telescope tube on which there is mounted, for instance by being slid over the free end of the tube 3 and being frictionally retained thereon, an arrangement which comprises an optical observation Window 30 outwardly adjacent to whose outer exposed surface there is arranged a member 32 corresponding to the members 12 in FIG. 1 and 22 in FIG. 2.
  • the member 32 defines an aspirating channel 32a corresponding to the channels 12a and 22a of FIGS. 1 and 2, respectively. It further defines an annular gap 32b corresponding to the gap 22b of FIG. 2, and the gap 32b has disposed therein a filter element 33 which corresponds to the filter element 23 in FIG. 2 and which is, of course, air-permeable.
  • the annular gap 32b communicates with a suction or aspiration conduit 34 which in turn is connected with a suitable suction device, such as shown in FIG. 1.
  • a suction or aspiration conduit 34 which in turn is connected with a suitable suction device, such as shown in FIG. 1.
  • the interior of the telescope tube 3 can be maintained at a desired and preferably constant temperature, for instance by filling it with an extremely light gas, such as helium, and circulating this gas in the tube 3.
  • the boundary layer which develops at the outer exposed surface of the window 30 and tends to form schlieren as a result of the existing temperature differential, is withdrawn through the gap 32b.
  • the embodiment of FIG. 3 also comprises means for preventing the aspiration of schlieren-containing boundary layer to the free end or inlet end of the channel 32a, the reason being the same as set forth in FIG. 2. Unlike the embodiment of FIG. 2, however, the embodiment of FIG. 3 achieves this prevention of schlieren-containing boundary layer air not via a slot corresponding to the slot 25, but via a radially outwardly projecting flange 320 which extends relatively far away from the member 32 and thus guides the schlieren-containing boundary layer away from the inlet end of the channel 32a.
  • reference numeral 50 is intended to identify a photo theodolite which rests on a platform 5 turnable about a vertical axis V.
  • the instrument 50 is provided with an objective-tubus 51 which can be turned about a horizontal axis H.
  • a dome-shaped housing 52 surrounds the instrument 50 and is secured to the platform 5 so as to be turnable with the same and, therefore, with the instrument 50.
  • the housing 52 is provided with a meridional slot which is covered by a curved closure member 53.
  • the member 53 is operatively associated with the instrument 50 so as to slide along the meridional slot of the housing 52 in correspondence with elevational movements of the tubus 51 about the axis H.
  • the closure member 53 will slide out of the way.
  • the closure member 53 carries an optical observation window 40 whose optical axis AA is always in alignment with the optical axis of the tubus 51 by virtue of the fact that the operative connection between the drive means for the tubus 51 and the drive means for the closure member 53 effects movements of the two in such a manner as to maintain this axial alignment.
  • a roller-type closure or curtain 54 has a free end secured to the closure member 53 so that it is rolled up when the closure member 53 moves towards the left and downwardly in the picture, and is upwardly withdrawn if the closure member moves in the opposite direction. Thus, whatever portion of the meridional slot of the housing 52 is exposed by the closure member 53 is immediately closed by the curtain 54.
  • the observation window 40 is provided with my novel arrangement adjacent both its outer and inner exposed surfaces.
  • a body 42 corresponding to the body 32 of FIG. 3 is arranged adjacent the outer exposed surface of the observation window 40 and defines therewith an annular gap such as that illustrated in FIG. 3, which has disposed therein an air-permeable annular filter 43 corresponding to the filter 33 of FIG. 3.
  • the annular gap communicates with an aspiration conduit 44 which in turn is connected to a suction device as illustrated in FIG. 1.
  • a second nozzle body Arranged adjacent the inner exposed surface of the observation window 40, that is the surface which faces the interior of the housing 52, is a second nozzle body, identified with reference numeral 42a, which defines a further annular gap which also has disclosed therein an annular filter 43a.
  • This gap communicates with aspiration conduit 44a which is connected to the same suction means as that to which the conduit 44 is connected, or to a separate suction means.
  • the purpose of this arrangement is to assure that the boundary layer air is withdrawn from both the inner and outer exposed surfaces of the observation window 40, to eliminate the formation of schlieren, thereby making it possible to maintain the entire interior space within the housing 52 at constant temperature without danger of the development of schlieren.
  • a schlieren inhibiting arrangement particularly in conjunction with optical apparatus, comprising, in combination, wall means defining an enclosed space having a predetermined inner temperature therein; an observation window mounted in said wall means with the inside surface thereof exposed to said predetermined temperature and having a surface located outside said space and exposed to a body of fluid having a different temperature than said predetermined temperature; inhibiting means outwardly adjacent to said outside surface for effecting the flow of a stream of said fluid from a region remote from said surface initially in direction against said surface and subsequently in a plurality of directions along said surface toward the marginal zones thereof, said inhibiting means comprising an annular suction channel extending along the marginal zones of said surface concentric therewith and having radially inwardly facing suction aperture means, and nozzle means for directing from a region remote from said outside surface a substantially turbulence-free stream of fluid in direction axially of said suction channel against the center of said outside surface; and suction means connected to said annular suction channel for withdrawing through said radially inwardly facing aperture means the fluid
  • said window being an optical observation window and having an optical axis, and wherein said suction channel is coaxial with said optical axis.
  • said nozzle means having an outlet end adjacent said exposed surface and communicating with said annular gap, and an inlet end spaced from said outlet end and from said exposed surface; and wherein said preventing means comprises a flange extending radially of said nozzle means in the region of said inlet end.
  • said nozzle means having an outlet end adjacent said exposed surface and communicating with said annulargap, and an inlet end spaced from said outlet end and said exposed surface; and wherein said preventing means comprises slot means provided in said nozzle means and communicating with said annular gap for aspirating therethrough and into said annular gap schlieren-containing boundary-layer fluid so as to prevent aspiration of such fluid into said inlet end.
  • said slot means comprises an annular slot.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Telescopes (AREA)
  • Radiation Pyrometers (AREA)
  • Optical Measuring Cells (AREA)
  • Indicating Or Recording The Presence, Absence, Or Direction Of Movement (AREA)
  • Sampling And Sample Adjustment (AREA)
US661173A 1966-08-15 1967-08-15 Suppression of schlieren phenomena Expired - Lifetime US3510193A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1175866A CH444520A (de) 1966-08-15 1966-08-15 Verfahren zum Behindern der Ausbildung optisch störender Schlieren an einem Fenster mit Temperatursprung zum angrenzenden Raum und Gerät zur Durchführung dieses Verfahrens

Publications (1)

Publication Number Publication Date
US3510193A true US3510193A (en) 1970-05-05

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US661173A Expired - Lifetime US3510193A (en) 1966-08-15 1967-08-15 Suppression of schlieren phenomena

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US (1) US3510193A (de)
CH (1) CH444520A (de)
DE (1) DE1572616B2 (de)
FR (1) FR1533820A (de)
GB (1) GB1174325A (de)
NL (1) NL6710190A (de)
SE (1) SE325721B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0277081A1 (de) * 1987-01-07 1988-08-03 Scitex Corporation Ltd. Vorrichtung zur Stabilisation der Strahlungsenergieverteilung in einem Laserstrahlabtaster
US4887779A (en) * 1987-12-01 1989-12-19 The Boeing Company Roll drum sensor housing having sliding window
US20070183027A1 (en) * 2003-02-13 2007-08-09 Macdougall Craig H Forward view apparatus for motor vehicles
US20120087647A1 (en) * 2010-10-08 2012-04-12 Mori Seiki Co., Ltd. In-magazine imaging device enclosure

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2508181A1 (fr) * 1981-06-19 1982-12-24 Sopelem Dispositif d'etancheite pour un instrument optique

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3103712A (en) * 1961-05-23 1963-09-17 Allinikov Sidney High temperature resistant viewing device
US3118231A (en) * 1964-01-21 Rathsmill
US3310356A (en) * 1963-02-08 1967-03-21 Gen Precision Inc Lens protective device utilizing dual air streams

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3118231A (en) * 1964-01-21 Rathsmill
US3103712A (en) * 1961-05-23 1963-09-17 Allinikov Sidney High temperature resistant viewing device
US3310356A (en) * 1963-02-08 1967-03-21 Gen Precision Inc Lens protective device utilizing dual air streams

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0277081A1 (de) * 1987-01-07 1988-08-03 Scitex Corporation Ltd. Vorrichtung zur Stabilisation der Strahlungsenergieverteilung in einem Laserstrahlabtaster
US4834520A (en) * 1987-01-07 1989-05-30 Scitex Corporation Ltd. Device for stabilization of beam intensity distribution in laser scanners
US4887779A (en) * 1987-12-01 1989-12-19 The Boeing Company Roll drum sensor housing having sliding window
US20070183027A1 (en) * 2003-02-13 2007-08-09 Macdougall Craig H Forward view apparatus for motor vehicles
US7344258B2 (en) * 2003-02-13 2008-03-18 Macdougall Craig Hart Forward view apparatus for motor vehicles
US20120087647A1 (en) * 2010-10-08 2012-04-12 Mori Seiki Co., Ltd. In-magazine imaging device enclosure
US8444330B2 (en) * 2010-10-08 2013-05-21 Mori Seiki Co., Ltd. In-magazine imaging device enclosure

Also Published As

Publication number Publication date
DE1572616A1 (de) 1970-07-30
GB1174325A (en) 1969-12-17
DE1572616B2 (de) 1971-10-28
SE325721B (de) 1970-07-06
CH444520A (de) 1967-09-30
NL6710190A (de) 1968-02-16
FR1533820A (fr) 1968-07-19

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