CA2101309C - Objective lens for a free-space photonic switching system - Google Patents
Objective lens for a free-space photonic switching systemInfo
- Publication number
- CA2101309C CA2101309C CA002101309A CA2101309A CA2101309C CA 2101309 C CA2101309 C CA 2101309C CA 002101309 A CA002101309 A CA 002101309A CA 2101309 A CA2101309 A CA 2101309A CA 2101309 C CA2101309 C CA 2101309C
- Authority
- CA
- Canada
- Prior art keywords
- lens
- array
- positive
- collimated
- objective lens
- 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 - Fee Related
Links
- 230000003287 optical effect Effects 0.000 claims description 6
- 125000006850 spacer group Chemical group 0.000 description 4
- 206010010071 Coma Diseases 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 238000003491 array Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 101001026208 Bos taurus Potassium voltage-gated channel subfamily A member 4 Proteins 0.000 description 1
- 108091006146 Channels Proteins 0.000 description 1
- 201000009310 astigmatism Diseases 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/22—Telecentric objectives or lens systems
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
- G02B9/12—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having three components only
Abstract
An objective lens for a free-space photonic switching system is disclosed. The objective lens is utilized to change a collimated array of beams into an array of spots which will focus on the array of spatial light modulating elements (S-SEEDs, for example). The requirements for the lens (low f-number, field of view, etc.), result in a lens which includes an external stop, positive doublet, a positive (e.g., plano-convex) lens and a negative (e.g., field flattener) lens, the latter pair of lenses being separated by a predetermined distance d.
Description
2I0~3~~
OBJECTIVE LENS FOR A FREE-SPACE
PHOTONIC SWTTCHING SYSTEM
Technical Field The present invention relates to an objective lens for a free-space photonic switching system and, more particularly, to an objective lens capable of providing a focused array of spots to an associated array of photosensitive devices.
Background of the Invention Free-space photonic switching and computing systems utilize macroscopic optical elements such as holograms, gratings, lenses and mirrors as their basic hardware building blocks. In these systems, information is carried by arrays of beams of light which are collimated, manipulated and focused onto spatial light modulators in a stage-by-stage fashion. As such, free-space photonic switching systems provide the ability to interconnect a large number of communication channels at relatively high bit rates.
With respect to the design of lenses for a such free-space system, a number of requirements must be addressed. A lens is required to provide the focusing of a collimated beam array onto an array of light modulators. In order that each beam provide the correct "information", therefore, the light beams must be highly focused and distinct. In some cases, the beam arrays can be very large, on the order of a 64x64 element square. When the modulators utilized are symmetric self electro-effect devices (S-SEEDs), the switching speed is inversely proportion to the active window area of each S-SEED. Therefore, for relatively high rates of switching speed, relatively small active window areas are required. Thus, it is desired to minimize the f-number of the objective lens (to provide both a large numerical aperture and small spot size). Further requirements include diffraction-limited performance on a flat surface (essentially uniform illumination of the entire array) and telecentricity in the image space.
These and other requirements must therefore be considered when designing an objective lens for a free-space photonic switching system.
Summary of the Invention The requirements as outlined above are addressed by the present invention which relates to an objective lens for a free-space photonic switching system and, more particularly, to an objective lens which comprises relatively few components, yet provides a focused array of spot beams to an associated array of photosensitive devices, as further defined by the appended claims.
- la -In accordance with one aspect of the present invention there is provided a free-space photonic switching system comprising an optical source for producing as an output a collimated array of beams; an array of spatial light modulating devices; and an objective lens disposed between said optical source S and said array of spatial light modulating devices, said obj ective lens positioned to receive as an input said collimated array of beams and utilized for focusing said array of collimated beams onto said array of spatial light modulating devices, the lens comprising a positive doublet lens; a positive lens disposed beyond said positive doublet lens; a negative lens separated a predetermined distance d from said positive lens; and an external stop located before the entrance of said positive doublet lens, wherein the collimated array passes through said external stop, enters the positive doublet lens and exits the negative lens, so as to provide a focused spot beam array on said array of spatial light modulating devices.
..~'f _ ~~.Q~.~09 Brief Description of the Drawing FIG. 1 illustrates an exemplary stage of a free-space photonic switching system which may utilize the objective lens configuration of the present invention;
FIG. 2 contains a cross-section view of the objective lens of the present invention; and FIG. 3 contains a cross-section view of an assembled objective lens of the present invention.
Detailed Description FIG. 1 illustrates an exemplary stage 10 of an N-stage free-space photonic switching system. Stage 10 includes a high-power laser diode source 12, such as an AIGaAs semiconductor laser. The single collimated output beam from laser source 12 subsequently passes through a grating 14, such as a mufti-phase (e.g., Dammann) grating, which generates an array of beams from the single collimated laser beam. The array output from grating 14 subsequently passes through an optical isolator 16, where isolator 16 includes in this particular embodiment a polarization beam splitting cube 18 and quarter wave plate 20. The array of beams from grating 14 will pass through isolator 16 relatively unimpeded. An objective lens 30, discussed in detail hereinafter in association with FIGS. 2 and 3, is used to change the collimated array output from grating 14 into an array of spots which will focus on the surface of a spatial light modulator 22, in this case an array of S-SEEDs. The spot array is subsequently modulated by S-SEEDs 22 and redirected through objective lens 30 (which functions, in this direction, to form a collimated array of beams). In the return direction, quarter wave plate 20 rotates the collimated array such that the array is reflected by polarization beam splitting cube 18 and directed into an interconnection hologram 24 which is coupled to the next stage of the free-space photonic switching system (not shown).
In general, therefore, objective lens 30 performs the function of focusing the collimated array of beams onto the array of the light modulating devices.
To determine the required characteristics of objective lens 30, the following criteria need to be addressed. First, the stop location of objective lens 30 is defined by the position of grating 14. Therefore, the lens must include an external stop location so that isolator 16 may be inserted in the signal path between grating 14 and lens 30.
The size and geometry of isolator 16 also influence the required separation between grating 14 and lens 30. Additionally, the lens must have an f-sin (8) distortion so that the spacing of the focused spots on array 22 is uniform as a function of the order of grating 14. When S-SEEDS are used as the array devices, their switching speed is inversely proportional to their active window size, as mentioned above.
Therefore, to maximize system speed, it is desired to minimize the window size, which results in minimizing the f-number of the lens. Further, telecentricity of the lens in the image plane is desired to maintain the spot array size as the SEED array is focused, as well as to provide a symmetrical light path through the lens.
For a particular application, which will be discussed in detail in association with FIGS. 2 and 3, it was desired to provide a lens which was capable of focusing an array of spot beams onto an array of 4096 S-SEED elements (a 64x64 square array), with a spacing of approximately 0.02mm between adjacent elements and an array diagonal length of approximately 1.81mm (thus defining the field of view). Given the low f-number desired and the competing desire to provide a relatively compact overall system, a lens with a focal length of approximately l5mm may be utilized, thus providing an angular field of view of 7 °. It is to be understood that these particular dimensions are exemplary only, and may be modified as a function of the dimensions of the particular spatial light modulating array being employed.
An exemplary objective lens 30 which meets the various criteria discussed above is illustrated in FIG. 2. As shown, lens 30 includes a positive doublet 32, a positive lens 34, and a negative lens 36, where negative lens 36 is separated a predetermined distance d from positive lens 34. Positive lens 34 may be placed in physical contact with doublet lens 32. However, such physical contact may result in damage to the lenses and is therefore not recommended. As mentioned above, a necessary requirement for lens 30 is the provision of an external stop, so as to allow for the insertion of the redirecting components between the stop and the lens. In the arrangement shown in FIG. 2, stop 38 is located external to the lens system, and will lie in the plane of grating 14 (FIG. 1). Similar to a Petzval type lens, the use of positive doublet 32 provides for a relatively high numerical aperture over a small field of view (i.e., low f-number). Spherical aberration is controlled by the utilization of a high index glass in positive doublet 32. The utilization of a field flatterer lens for negative lens 36 provides for correction of field curvature and distortion. Coma and astigmatism may be corrected by the relative lens powers, thicknesses and spacing d, as necessary, by the user. An f-sin(6) distortion may be introduced by the design of field flatterer lens 36 (alternatively, an f-tan(9) or f(0) distortion may be introduced by changing the lens design). The sum of all lens thicknesses is greater than the focal length of lens 30. In a preferred embodiment, doublet 32 may comprise a relatively low index of refraction glass (such as BK7) -t and a relatively high index of refraction glass (such as LASFN 18), positive (piano-convex) lens 34 may comprise BK7, and negative (field-flattener) lens may comprise BAK4.
FIG. 3 illustrates objective lens 30 as assembled within a barrel housing 40. A first spacer 42 of thickness t, is included to provide lens alignment. A second spacer 44 of thickness t2 rests upon a flat surface 46 of piano-convex lens 34 and an enlarged annular flat surface 48 formed around the periphery of field flattener lens 36. Upon assembly, spherical aberration may be corrected by adjusting the thickness tz of second spacer 44. On-axis coma may be corrected simply by rotating either doublet lens 32, field flattener lens 36, or both.
Any linear coma which may be present may be compensated by adjusting the thickness t, of first spacer 42.
f ~y=~
OBJECTIVE LENS FOR A FREE-SPACE
PHOTONIC SWTTCHING SYSTEM
Technical Field The present invention relates to an objective lens for a free-space photonic switching system and, more particularly, to an objective lens capable of providing a focused array of spots to an associated array of photosensitive devices.
Background of the Invention Free-space photonic switching and computing systems utilize macroscopic optical elements such as holograms, gratings, lenses and mirrors as their basic hardware building blocks. In these systems, information is carried by arrays of beams of light which are collimated, manipulated and focused onto spatial light modulators in a stage-by-stage fashion. As such, free-space photonic switching systems provide the ability to interconnect a large number of communication channels at relatively high bit rates.
With respect to the design of lenses for a such free-space system, a number of requirements must be addressed. A lens is required to provide the focusing of a collimated beam array onto an array of light modulators. In order that each beam provide the correct "information", therefore, the light beams must be highly focused and distinct. In some cases, the beam arrays can be very large, on the order of a 64x64 element square. When the modulators utilized are symmetric self electro-effect devices (S-SEEDs), the switching speed is inversely proportion to the active window area of each S-SEED. Therefore, for relatively high rates of switching speed, relatively small active window areas are required. Thus, it is desired to minimize the f-number of the objective lens (to provide both a large numerical aperture and small spot size). Further requirements include diffraction-limited performance on a flat surface (essentially uniform illumination of the entire array) and telecentricity in the image space.
These and other requirements must therefore be considered when designing an objective lens for a free-space photonic switching system.
Summary of the Invention The requirements as outlined above are addressed by the present invention which relates to an objective lens for a free-space photonic switching system and, more particularly, to an objective lens which comprises relatively few components, yet provides a focused array of spot beams to an associated array of photosensitive devices, as further defined by the appended claims.
- la -In accordance with one aspect of the present invention there is provided a free-space photonic switching system comprising an optical source for producing as an output a collimated array of beams; an array of spatial light modulating devices; and an objective lens disposed between said optical source S and said array of spatial light modulating devices, said obj ective lens positioned to receive as an input said collimated array of beams and utilized for focusing said array of collimated beams onto said array of spatial light modulating devices, the lens comprising a positive doublet lens; a positive lens disposed beyond said positive doublet lens; a negative lens separated a predetermined distance d from said positive lens; and an external stop located before the entrance of said positive doublet lens, wherein the collimated array passes through said external stop, enters the positive doublet lens and exits the negative lens, so as to provide a focused spot beam array on said array of spatial light modulating devices.
..~'f _ ~~.Q~.~09 Brief Description of the Drawing FIG. 1 illustrates an exemplary stage of a free-space photonic switching system which may utilize the objective lens configuration of the present invention;
FIG. 2 contains a cross-section view of the objective lens of the present invention; and FIG. 3 contains a cross-section view of an assembled objective lens of the present invention.
Detailed Description FIG. 1 illustrates an exemplary stage 10 of an N-stage free-space photonic switching system. Stage 10 includes a high-power laser diode source 12, such as an AIGaAs semiconductor laser. The single collimated output beam from laser source 12 subsequently passes through a grating 14, such as a mufti-phase (e.g., Dammann) grating, which generates an array of beams from the single collimated laser beam. The array output from grating 14 subsequently passes through an optical isolator 16, where isolator 16 includes in this particular embodiment a polarization beam splitting cube 18 and quarter wave plate 20. The array of beams from grating 14 will pass through isolator 16 relatively unimpeded. An objective lens 30, discussed in detail hereinafter in association with FIGS. 2 and 3, is used to change the collimated array output from grating 14 into an array of spots which will focus on the surface of a spatial light modulator 22, in this case an array of S-SEEDs. The spot array is subsequently modulated by S-SEEDs 22 and redirected through objective lens 30 (which functions, in this direction, to form a collimated array of beams). In the return direction, quarter wave plate 20 rotates the collimated array such that the array is reflected by polarization beam splitting cube 18 and directed into an interconnection hologram 24 which is coupled to the next stage of the free-space photonic switching system (not shown).
In general, therefore, objective lens 30 performs the function of focusing the collimated array of beams onto the array of the light modulating devices.
To determine the required characteristics of objective lens 30, the following criteria need to be addressed. First, the stop location of objective lens 30 is defined by the position of grating 14. Therefore, the lens must include an external stop location so that isolator 16 may be inserted in the signal path between grating 14 and lens 30.
The size and geometry of isolator 16 also influence the required separation between grating 14 and lens 30. Additionally, the lens must have an f-sin (8) distortion so that the spacing of the focused spots on array 22 is uniform as a function of the order of grating 14. When S-SEEDS are used as the array devices, their switching speed is inversely proportional to their active window size, as mentioned above.
Therefore, to maximize system speed, it is desired to minimize the window size, which results in minimizing the f-number of the lens. Further, telecentricity of the lens in the image plane is desired to maintain the spot array size as the SEED array is focused, as well as to provide a symmetrical light path through the lens.
For a particular application, which will be discussed in detail in association with FIGS. 2 and 3, it was desired to provide a lens which was capable of focusing an array of spot beams onto an array of 4096 S-SEED elements (a 64x64 square array), with a spacing of approximately 0.02mm between adjacent elements and an array diagonal length of approximately 1.81mm (thus defining the field of view). Given the low f-number desired and the competing desire to provide a relatively compact overall system, a lens with a focal length of approximately l5mm may be utilized, thus providing an angular field of view of 7 °. It is to be understood that these particular dimensions are exemplary only, and may be modified as a function of the dimensions of the particular spatial light modulating array being employed.
An exemplary objective lens 30 which meets the various criteria discussed above is illustrated in FIG. 2. As shown, lens 30 includes a positive doublet 32, a positive lens 34, and a negative lens 36, where negative lens 36 is separated a predetermined distance d from positive lens 34. Positive lens 34 may be placed in physical contact with doublet lens 32. However, such physical contact may result in damage to the lenses and is therefore not recommended. As mentioned above, a necessary requirement for lens 30 is the provision of an external stop, so as to allow for the insertion of the redirecting components between the stop and the lens. In the arrangement shown in FIG. 2, stop 38 is located external to the lens system, and will lie in the plane of grating 14 (FIG. 1). Similar to a Petzval type lens, the use of positive doublet 32 provides for a relatively high numerical aperture over a small field of view (i.e., low f-number). Spherical aberration is controlled by the utilization of a high index glass in positive doublet 32. The utilization of a field flatterer lens for negative lens 36 provides for correction of field curvature and distortion. Coma and astigmatism may be corrected by the relative lens powers, thicknesses and spacing d, as necessary, by the user. An f-sin(6) distortion may be introduced by the design of field flatterer lens 36 (alternatively, an f-tan(9) or f(0) distortion may be introduced by changing the lens design). The sum of all lens thicknesses is greater than the focal length of lens 30. In a preferred embodiment, doublet 32 may comprise a relatively low index of refraction glass (such as BK7) -t and a relatively high index of refraction glass (such as LASFN 18), positive (piano-convex) lens 34 may comprise BK7, and negative (field-flattener) lens may comprise BAK4.
FIG. 3 illustrates objective lens 30 as assembled within a barrel housing 40. A first spacer 42 of thickness t, is included to provide lens alignment. A second spacer 44 of thickness t2 rests upon a flat surface 46 of piano-convex lens 34 and an enlarged annular flat surface 48 formed around the periphery of field flattener lens 36. Upon assembly, spherical aberration may be corrected by adjusting the thickness tz of second spacer 44. On-axis coma may be corrected simply by rotating either doublet lens 32, field flattener lens 36, or both.
Any linear coma which may be present may be compensated by adjusting the thickness t, of first spacer 42.
f ~y=~
Claims (6)
1. A free-space photonic switching system comprising an optical source for producing as an output a collimated array of beams;
an array of spatial light modulating devices; and an objective lens disposed between said optical source and said array of spatial light modulating devices, said objective lens positioned to receive as an input said collimated array of beams and utilized for focusing said array of collimated beams onto said array of spatial light modulating devices, the lens comprising a positive doublet lens;
a positive lens disposed beyond said positive doublet lens;
a negative lens separated a predetermined distance d from said positive lens; and an external stop located before the entrance of said positive doublet lens, wherein the collimated array passes through said external stop, enters the positive doublet lens and exits the negative lens, so as to provide a focused spot beam array on said array of spatial light modulating devices.
an array of spatial light modulating devices; and an objective lens disposed between said optical source and said array of spatial light modulating devices, said objective lens positioned to receive as an input said collimated array of beams and utilized for focusing said array of collimated beams onto said array of spatial light modulating devices, the lens comprising a positive doublet lens;
a positive lens disposed beyond said positive doublet lens;
a negative lens separated a predetermined distance d from said positive lens; and an external stop located before the entrance of said positive doublet lens, wherein the collimated array passes through said external stop, enters the positive doublet lens and exits the negative lens, so as to provide a focused spot beam array on said array of spatial light modulating devices.
2. In the system of claim 1, the positive lens being separated from the positive doublet lens.
3. In the system of claim 1, the positive doublet lens comprising a first lens of a relatively low refractive index material and a second lens of a relatively high refractive index material.
4. In the system of claim 1, the positive lens comprising a plano-convex lens.
5. In the system of claim 4, the piano-convex lens comprising a relatively low refractive index material.
6. In the system of claim 1, the negative lens comprising a field flattener lens.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US969,495 | 1992-10-30 | ||
| US07/969,495 US5353164A (en) | 1992-10-30 | 1992-10-30 | Objective lens for a free-space photonic switching system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2101309A1 CA2101309A1 (en) | 1994-05-01 |
| CA2101309C true CA2101309C (en) | 1999-09-28 |
Family
ID=25515635
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002101309A Expired - Fee Related CA2101309C (en) | 1992-10-30 | 1993-07-26 | Objective lens for a free-space photonic switching system |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5353164A (en) |
| EP (1) | EP0595533A1 (en) |
| JP (1) | JPH06214152A (en) |
| KR (1) | KR940009706A (en) |
| CA (1) | CA2101309C (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW297100B (en) * | 1994-07-25 | 1997-02-01 | Philips Electronics Nv | |
| JPH08106043A (en) * | 1994-10-05 | 1996-04-23 | Fuji Photo Optical Co Ltd | Objective lens for endoscope |
| RU2267143C2 (en) * | 1998-06-05 | 2005-12-27 | Эй Эф Эн Ллк | Optical switch( variants ), optical switching device( variants ) and mode of switching of an optical signal |
| JP3346374B2 (en) * | 1999-06-23 | 2002-11-18 | 住友電気工業株式会社 | Laser drilling machine |
| CA2280531C (en) * | 1999-08-19 | 2008-06-10 | Simon Thibault | F-sin (.theta.) lens system and method of use of same |
| US6650413B2 (en) | 1999-08-08 | 2003-11-18 | Institut National D'optique | Linear spectrometer |
| US6597831B2 (en) | 2000-11-29 | 2003-07-22 | Institut National D'optique | Linear wavelength DWDM |
| US20070272792A1 (en) * | 2006-05-26 | 2007-11-29 | Herzel Laor | Optical switching apparatus |
Family Cites Families (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2055859A (en) * | 1933-11-16 | 1936-09-29 | Ludwig M Dieterich | Optical system and method |
| GB836087A (en) * | 1957-04-04 | 1960-06-01 | Ludwig Fakob Bertele | Photographic objective |
| US3039360A (en) * | 1958-03-17 | 1962-06-19 | Gen Precision Inc | Lens with remote entrance pupil |
| US3733404A (en) * | 1970-09-04 | 1973-05-15 | Squibb & Sons Inc | Antibacterial composition containing alpha-aminobenzyl penicillins |
| JPS5641974B2 (en) * | 1973-07-07 | 1981-10-01 | ||
| US3876291A (en) * | 1973-07-09 | 1975-04-08 | American Optical Corp | Ten power microscope objective |
| JPS5248010B2 (en) * | 1973-12-05 | 1977-12-07 | ||
| US4082415A (en) * | 1974-03-27 | 1978-04-04 | Trw Inc. | Holographic lens array and method for making the same |
| US3982821A (en) * | 1974-04-26 | 1976-09-28 | American Optical Corporation | Microscope objectives |
| JPS5248011B2 (en) * | 1974-05-14 | 1977-12-07 | ||
| US4111529A (en) * | 1974-08-14 | 1978-09-05 | Olympus Optical Co., Ltd. | Optical system for an endoscope |
| US4300817A (en) * | 1978-09-08 | 1981-11-17 | U.S. Precision Lens Incorporated | Projection lens |
| US4304467A (en) * | 1979-05-29 | 1981-12-08 | International Business Machines Corporation | Focussed laser beam optical system |
| US4348081A (en) * | 1979-09-05 | 1982-09-07 | U.S. Precision Lens Inc. | Projection lens |
| US4526442A (en) * | 1981-01-28 | 1985-07-02 | U.S. Precision Lens, Inc. | Compact projection lens |
| JPS60115908A (en) * | 1983-11-28 | 1985-06-22 | Konishiroku Photo Ind Co Ltd | Projection lens |
| US4740067A (en) * | 1984-04-03 | 1988-04-26 | Minolta Camera Kabushiki Kaisha | Projection lens system |
| JP2563175B2 (en) * | 1987-05-14 | 1996-12-11 | 旭光学工業株式会社 | Endoscope objective lens |
| JPH04151622A (en) * | 1990-10-16 | 1992-05-25 | Ricoh Co Ltd | Electrooptical modulation element |
-
1992
- 1992-10-30 US US07/969,495 patent/US5353164A/en not_active Expired - Lifetime
-
1993
- 1993-07-26 CA CA002101309A patent/CA2101309C/en not_active Expired - Fee Related
- 1993-10-12 KR KR1019930021091A patent/KR940009706A/en not_active Application Discontinuation
- 1993-10-20 EP EP93308332A patent/EP0595533A1/en not_active Withdrawn
- 1993-10-29 JP JP5292376A patent/JPH06214152A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| CA2101309A1 (en) | 1994-05-01 |
| EP0595533A1 (en) | 1994-05-04 |
| JPH06214152A (en) | 1994-08-05 |
| US5353164A (en) | 1994-10-04 |
| KR940009706A (en) | 1994-05-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |