WO1998014801A1 - Strengthened optical glass filter - Google Patents
Strengthened optical glass filter Download PDFInfo
- Publication number
- WO1998014801A1 WO1998014801A1 PCT/US1997/016726 US9716726W WO9814801A1 WO 1998014801 A1 WO1998014801 A1 WO 1998014801A1 US 9716726 W US9716726 W US 9716726W WO 9814801 A1 WO9814801 A1 WO 9814801A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- core
- cladding
- lens
- accordance
- glass
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B3/00—Simple or compound lenses
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
- G02B7/028—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
Definitions
- spatial filter lens refers to a lens through which a laser beam passes into an evacuated space.
- fluence refers to energy expressed in Joules/cm 2 .
- Fused silica by its very nature, does not lend itself to the familiar glass strengthening practices of air tempering, surface modification by ion-exchange, or surface crystallization. Thus, there is a particular need for a glass strengthening procedure that is applicable to fused silica. It is a basic purpose of the present invention to meet this observed need. It is a further purpose to provide an optical filter lens having increased mechanical strength and/or less thickness. Another purpose is to provide such a lens having the transmissive characteristics of fused silica. A specific purpose is to provide a relatively thin, spatial filter lens for a high-fluence laser that can withstand the necessary pressure differential in service. It is also a purpose to provide a method of producing such an improved filter lens.
- the article of the invention is a laminated, optical glass filter lens comprising a core and a cladding, the core having an essentially pure, fused oxide composition and the cladding having a different, fused oxide composition, the cladding having a coefficient of thermal expansion (CTE) lower than that of the core glass.
- CTE coefficient of thermal expansion
- the method aspect of the invention comprises depositing particles of a fused metal oxide to form an optical lens core and then depositing particles of a different fused metal oxide composition to form a cladding on the core, the cladding having a lower
- FIGURES 1 and 2 are schematic drawings illustrating, respectively, a perspective view and a side view of an article in accordance with the invention.
- fused silica is a preferred material for production of optical filter lenses, in particular, lenses for use in a high-fluence laser. Accordingly, the invention was developed for, and is described with respect to, an article of this material. However, it will be apparent that the basic principles involved apply equally to any fused metal oxide composition otherwise meeting the necessary qualifications, including binary metal oxide compositions.
- Fused silica has traditionally been produced by flame hydrolysis of silicon tetra chloride, the process being well known to those active in the art. Recently, it has been proposed to use silane derivatives, in particular, octamethylcyclotetrasiloxane, as a substitute precursor for silica.
- FIGURE 1 is a perspective view of a symmetrically laminated, optical glass article 10 illustrating the invention.
- Laminated article 10 has a flat core section 12 that has a first cladding layer 14 on one surface and a second cladding layer 16 on the opposite surface.
- Article 10 may, for example, be a spatial filter lens. It is shown as having a cylindrical shape. However, it may also have a square, other rectangular, circular or disc shape if desired.
- Core 12 is a pure, fused-oxide glass, in this case, fused-silica with a CTE of about 5xlO "7 /° C.
- Cladding layers 14 and 16 are the same binary glass, here a Si0 2 -TiO 2 glass. The properties of this binary glass depend on the TiO 2 content which may be up to about 10% by weight.
- FIGURE 2 is a schematic side view of the laminated article of FIGURE 1.
- Such an article may be manufactured using the same flame hydrolysis process that is commonly used to produce a monolithic, SiO 2 article.
- the primary considerations in forming the laminated body are good control of thickness in the layers, and control of the
- SiO 2 :TiO weight fraction or ratio SiO 2 :TiO weight fraction or ratio.
- Known equipment and procedure for producing molten particles of silica may be employed in producing the present laminated article. It is necessary only to provide dual vapor streams to the flame. One stream will contain a TiO 2 precursor, such as TiCl 4 , and the other stream will contain a Si0 2 precursor, such as SiCL». The contents of the streams will be adjusted to provide the ultimate desired TiO 2 /SiO 2 weight ratio in the binary glass particles deposited to form the initial cladding layer.
- the TiCl source is stopped. This permits depositing a layer 12 of pure SiO 2 to form the core of the laminated body. Then, the TiCl 4 source is reopened to deposit the upper cladding layer 14.
- the cladding must have a lower CTE, preferably up to 10xl0 "7 /° C. lower, than the core.
- a SiO 2 -TiO 2 cladding may have a CTE of close to 0 while the silica core has a CTE of about 5xl0 "7 /° C.
- the TiO content in the cladding may have a gradient profile.
- the resulting laminated body upon cooling to room temperature, has significant compressive stresses induced in the cladding layer due to the expansion differential. These compressive stresses must be overcome before any tensile stresses can be introduced by bending. Furthermore, the thermal expansion of the cladding glass can be tailored by adjusting its composition to induce the desired level of surface compression.
- the cladding glass can be incorporated using the same flame hydrolysis process as that employed for manufacturing monolithic, fused-silica lenses.
- the fused silica lens can experience surface damage on the vacuum side if the tensile stress exceeds the threshold value.
- the consequences of lens failure can be very costly, particularly to ancillary equipment. Consequently, it has been found necessary to keep the failure probability several orders of magnitude lower than that of most glass products. This is done by reducing the allowable design stress to about 5.5 MPa (800 psi). Furthermore, the stored elastic energy at a peak flexure stress of 5.5 MPa (800 psi) is sufficiently low to contain damage in the remote case of lens failure.
- the thickness of a cladding layer (t s ) is much lower than the thickness of the silica core (t c ).
- the typical t 0 :t s ratio is about 20: 1. This cladding layer thickness has been found sufficient to contain surface damage within the compression layer.
- Fused silica the core material
- Setting Temperature (T c ) 990°C.
- T s T c -1500 ⁇ E s E c (l- ⁇ )
- the stored elastic energy in a fused-silica core ⁇ c which will contribute to fragmentation of a laminated lens, is negligibly small compared with that due to flexure of a lens under vacuum loading This is due to a low value of internal tension This low internal tension value is also desirable to avoid risk of fracture when a laminated lens is ground and polished to a required power
- ⁇ s , ⁇ d, t R and ⁇ /R values for TiO 2 contents of 0-3% by weight in a laminated article.
- ⁇ d denotes the safe design stress
- ⁇ /R the net stored energy due to bending and lamination
- R denotes the radius in a circular lens. It denots one-half the side in a square lens, and one-half the short side in a rectangular lens.
- the thickness t of a laminated lens can be reduced significantly compared with that of a monolithic, silica lens while limiting the net tensile stress on the vacuum side to 6.9 MPa (800 psi).
- TiO 2 levels as low as 1.5% can reduce the lens thickness by 33.5% with 43% lower stored energy than that in a monolithic lens stressed to 12.5 MPa (1810 psi).
- the net stored energy in the thin, laminated lens will be higher due to larger contributions from bending.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Glass Compositions (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP97942617A EP0929827A4 (en) | 1996-09-30 | 1997-09-18 | Strengthened optical glass filter |
JP10516596A JP2001501743A (en) | 1996-09-30 | 1997-09-18 | Enhanced light glass filter |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US2711796P | 1996-09-30 | 1996-09-30 | |
US60/027,117 | 1996-09-30 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1998014801A1 true WO1998014801A1 (en) | 1998-04-09 |
Family
ID=21835792
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1997/016726 WO1998014801A1 (en) | 1996-09-30 | 1997-09-18 | Strengthened optical glass filter |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0929827A4 (en) |
JP (1) | JP2001501743A (en) |
KR (1) | KR20000048738A (en) |
WO (1) | WO1998014801A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN102879980B (en) * | 2012-10-12 | 2015-09-09 | 中国科学院长春光学精密机械与物理研究所 | Temperature self-adaptation space remote sensing camera airframe structure |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4209229A (en) * | 1978-09-25 | 1980-06-24 | Corning Glass Works | Glass-ceramic coated optical waveguides |
US5400428A (en) * | 1992-05-13 | 1995-03-21 | Spectranetics Corporation | Method and apparatus for linearly scanning energy over an optical fiber array and coupler for coupling energy to the optical fiber array |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1960121A (en) * | 1930-02-10 | 1934-05-22 | American Optical Corp | Glass treatment |
US3673049A (en) * | 1970-10-07 | 1972-06-27 | Corning Glass Works | Glass laminated bodies comprising a tensilely stressed core and a compressively stressed surface layer fused thereto |
US3676043A (en) * | 1970-10-26 | 1972-07-11 | Sylvania Electric Prod | Photoflash lamp having laminated glass envelope |
JPS58217901A (en) * | 1982-06-14 | 1983-12-19 | Nippon Kogaku Kk <Nikon> | Laminate vapor-deposited on both sides |
JPS5993403A (en) * | 1982-11-19 | 1984-05-29 | Furukawa Electric Co Ltd:The | Optical fiber |
DD230651A3 (en) * | 1983-10-21 | 1985-12-04 | Zeiss Jena Veb Carl | LASER RADIATION-RESISTANT ABSORPTION-FREE OXIDIC LAYERING STOCK ELEMENT |
US4781970A (en) * | 1987-07-15 | 1988-11-01 | International Business Machines Corporation | Strengthening a ceramic by post sinter coating with a compressive surface layer |
US4956000A (en) * | 1989-06-28 | 1990-09-11 | Reeber Robert R | Gradient lens fabrication |
-
1997
- 1997-09-18 EP EP97942617A patent/EP0929827A4/en not_active Withdrawn
- 1997-09-18 WO PCT/US1997/016726 patent/WO1998014801A1/en not_active Application Discontinuation
- 1997-09-18 KR KR1019990702720A patent/KR20000048738A/en not_active Application Discontinuation
- 1997-09-18 JP JP10516596A patent/JP2001501743A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4209229A (en) * | 1978-09-25 | 1980-06-24 | Corning Glass Works | Glass-ceramic coated optical waveguides |
US5400428A (en) * | 1992-05-13 | 1995-03-21 | Spectranetics Corporation | Method and apparatus for linearly scanning energy over an optical fiber array and coupler for coupling energy to the optical fiber array |
Non-Patent Citations (1)
Title |
---|
See also references of EP0929827A4 * |
Also Published As
Publication number | Publication date |
---|---|
EP0929827A1 (en) | 1999-07-21 |
JP2001501743A (en) | 2001-02-06 |
EP0929827A4 (en) | 2000-11-22 |
KR20000048738A (en) | 2000-07-25 |
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