CA2213327A1 - Improvements in microlens fabrication - Google Patents
Improvements in microlens fabricationInfo
- Publication number
- CA2213327A1 CA2213327A1 CA 2213327 CA2213327A CA2213327A1 CA 2213327 A1 CA2213327 A1 CA 2213327A1 CA 2213327 CA2213327 CA 2213327 CA 2213327 A CA2213327 A CA 2213327A CA 2213327 A1 CA2213327 A1 CA 2213327A1
- Authority
- CA
- Canada
- Prior art keywords
- substrate
- curable
- nozzle tip
- forming liquid
- nozzle
- 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.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B3/00—Simple or compound lenses
- G02B3/0006—Arrays
- G02B3/0012—Arrays characterised by the manufacturing method
- G02B3/0031—Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00009—Production of simple or compound lenses
- B29D11/00365—Production of microlenses
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Health & Medical Sciences (AREA)
- Ophthalmology & Optometry (AREA)
- Mechanical Engineering (AREA)
Abstract
A method of forming an optical element on the surface of a substrate by ejecting a curable microlens forming liquid from a nozzle onto the surface of the substrate and curing the curable microlens forming liquid. The nozzle tip is parallel to the surface of the substrate when the nozzle tip is moved away from the substrate. Anamorphic lenses may be formed by moving the nozzle tip immediately after ejecting liquid onto the surface of the substrate.
F/numbers of lenses in an array are made more uniform by allowing the lenses to settle while in liquid form before curing. F/number of lenses may be controlled by controlling the surface tension of the surface of the substrate.
F/numbers of lenses in an array are made more uniform by allowing the lenses to settle while in liquid form before curing. F/number of lenses may be controlled by controlling the surface tension of the surface of the substrate.
Description
DEMANDES OU BREVET'S VOLUMINEU~C
LA PRESENTS PARTlE DE CETTE DEMANDS OU CE BREVET
COMPREND PLUS D'UN TOME.
CSC! EST LE TOME ~ DE
NOTE: Pour les tomes additionels, veuillez contacter le Bureau canadien des brevets JUMBO APPtICATIONS/PATENTS
THAN ONE VOLUME ~ . , THIS lS VOLUME ,~_ OF
NOTE: For additional volumes-pf~ase~contact the Canadian Patent Office .
TITLE OF INVENTION:
Improvements in Microlens Fabrication NAMES OF INVENTORS:
Barrie Peter Keyworth James Neil McMullin Dino J. Corazza FIELD OF THE INVENTION:
This invention relates to methods for making optical lenses on substrates.
CLAIM TO COPYRIGHT:
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document, as it appears in the Patent Office patent file or records, but otherwise reserves all copyright rights whatsoever.
BACKGROUND OF THE INVENTION:
United States patent no. 5,534,101 of Keyworth and McMullin issued July 9, 1996, describes a method and apparatus for the formation of microlenses by ejecting a curable liquid through a syringe onto a planar substrate. The apparatus includes an x-y movable support fob the substrate, a z-movable support for the syringe, a system to regulate pressure in the syringe and a computer to control the overall process. Microlensea are formed by lowering the syringe tip to the substrate surface, at which time a computer controller triggers a pressure regulator to momentarily increase the pressure inside the syringe. This causes a volume of liquid to be deposited on the substrate surface. When the desired amount of liquid has been dispensed on the surface, the pressure regulator is triggered to lower the pressure in the syringe. The syringe is then lifted off the substrate. An array of microlenses can be fabricated by repeating the above procedure with the substrate moved to a different position relative to the syringe.
While adequate microlensee for some purposes can be made following the technique described in United States patent no. 5, 534, 101, the inventors have found methods of improving the lens uniformity and quality, and controlling the lens characteristics.
SUMMARY OF THE INVENTION:
In general the invention deals with a method of forming microlenses on a substrate that comprises the steps of positioning a nozzle tip sufficiently close to the surface of a substrate that curable microlens forming liquid may form a bridge between the nozzle tip and the surface, momentarily ejecting curable microlens forming liquid from the nozzle onto the substrate, moving the nozzle tip away from the surface of the substrate to detach the nozzle tip from the curable microlens forming liquid and curing the curable microlens forming liquid to form an optical element on the surface of the substrate.
In a further aspect of the invention, an anamorphic lens is formed by moving the nozzle tip laterally after deposition of curable microlens forming liquid to form a microlens.
In a further aspect of the invention, an array of microlenses is formed by translating the nozzle tip between repetitions of the process of forming the microlens. Uniform arrays are formed by allowing the lenses to settle while in liquid form to a uniform shape before curing.
In a further aspect of the invention, an array of microlenses is formed with spacing between microlenses the same as the spacing between light sources in an array of light sources.
In a further aspect of the invention, f number of the lenses is modified by alteration of the properties of the surface of the substrate, for example by modifying the curing time of a substrate spin coated with a uniform film of curable liquid.
In a further aspect of the invention, the surface of the substrate is formed with a different curable microlens forming liquid from the light guide forming liquid used to make the microlenses.
These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS:
There will now be described preferred embodiments of the invention, with reference to the drawings, by way of illustration, in which like numerals denote like elements and in which:
Figure 1 is a schematic showing an embodiment of the prior art apparatus described in United States patent no. 5,534,101;
Figure 2 is a side view of a dispensing tip in the process of carrying out an embodiment of the method of the invention;
Fig. 3A is a schematic showing dispensing of a droplet onto a substrate 10;
LA PRESENTS PARTlE DE CETTE DEMANDS OU CE BREVET
COMPREND PLUS D'UN TOME.
CSC! EST LE TOME ~ DE
NOTE: Pour les tomes additionels, veuillez contacter le Bureau canadien des brevets JUMBO APPtICATIONS/PATENTS
THAN ONE VOLUME ~ . , THIS lS VOLUME ,~_ OF
NOTE: For additional volumes-pf~ase~contact the Canadian Patent Office .
TITLE OF INVENTION:
Improvements in Microlens Fabrication NAMES OF INVENTORS:
Barrie Peter Keyworth James Neil McMullin Dino J. Corazza FIELD OF THE INVENTION:
This invention relates to methods for making optical lenses on substrates.
CLAIM TO COPYRIGHT:
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document, as it appears in the Patent Office patent file or records, but otherwise reserves all copyright rights whatsoever.
BACKGROUND OF THE INVENTION:
United States patent no. 5,534,101 of Keyworth and McMullin issued July 9, 1996, describes a method and apparatus for the formation of microlenses by ejecting a curable liquid through a syringe onto a planar substrate. The apparatus includes an x-y movable support fob the substrate, a z-movable support for the syringe, a system to regulate pressure in the syringe and a computer to control the overall process. Microlensea are formed by lowering the syringe tip to the substrate surface, at which time a computer controller triggers a pressure regulator to momentarily increase the pressure inside the syringe. This causes a volume of liquid to be deposited on the substrate surface. When the desired amount of liquid has been dispensed on the surface, the pressure regulator is triggered to lower the pressure in the syringe. The syringe is then lifted off the substrate. An array of microlenses can be fabricated by repeating the above procedure with the substrate moved to a different position relative to the syringe.
While adequate microlensee for some purposes can be made following the technique described in United States patent no. 5, 534, 101, the inventors have found methods of improving the lens uniformity and quality, and controlling the lens characteristics.
SUMMARY OF THE INVENTION:
In general the invention deals with a method of forming microlenses on a substrate that comprises the steps of positioning a nozzle tip sufficiently close to the surface of a substrate that curable microlens forming liquid may form a bridge between the nozzle tip and the surface, momentarily ejecting curable microlens forming liquid from the nozzle onto the substrate, moving the nozzle tip away from the surface of the substrate to detach the nozzle tip from the curable microlens forming liquid and curing the curable microlens forming liquid to form an optical element on the surface of the substrate.
In a further aspect of the invention, an anamorphic lens is formed by moving the nozzle tip laterally after deposition of curable microlens forming liquid to form a microlens.
In a further aspect of the invention, an array of microlenses is formed by translating the nozzle tip between repetitions of the process of forming the microlens. Uniform arrays are formed by allowing the lenses to settle while in liquid form to a uniform shape before curing.
In a further aspect of the invention, an array of microlenses is formed with spacing between microlenses the same as the spacing between light sources in an array of light sources.
In a further aspect of the invention, f number of the lenses is modified by alteration of the properties of the surface of the substrate, for example by modifying the curing time of a substrate spin coated with a uniform film of curable liquid.
In a further aspect of the invention, the surface of the substrate is formed with a different curable microlens forming liquid from the light guide forming liquid used to make the microlenses.
These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS:
There will now be described preferred embodiments of the invention, with reference to the drawings, by way of illustration, in which like numerals denote like elements and in which:
Figure 1 is a schematic showing an embodiment of the prior art apparatus described in United States patent no. 5,534,101;
Figure 2 is a side view of a dispensing tip in the process of carrying out an embodiment of the method of the invention;
Fig. 3A is a schematic showing dispensing of a droplet onto a substrate 10;
Fig. 3B is a schematic showing formation of an anamorphic lens by movement of the nozzle in a transverse direction;
Fig. 3C shows the outline of an anamorphic lens 34 produced as shown in Fig. 3B;
Fig. 4 is a graph showing uniformity of focal length for several lenses in an array where array is cured immediately after formation of the last lens;
Fig. 5 is a graph showing uniformity of focal length for several lenses in an array where the liquid droplets in the array were allowed to settle for 30 minutes before curing with W radiation;
Fig. 6 is a graph showing a typical relationship between curing time (hence surface tension of the surface layer of the substrate) and lens f/number;
Fig. 7 is a graph showing a second relationship between curing time of the substrate (hence surface tension of the surface layer of the substrate) and lens f/number; and Fig. 8 is a schematic showing application of an array of microlenses to collimate light from an array of lasers.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS:
Referring to Fig. 1 there is shown a prior art apparatus for forming a light guide on a substrate 10. The substrate 10 may be silicon dioxide, glass, lithium niobate or any semi-conducting material used for making electronic components . The substrate 10 has an upper planar surface 12, and rests on a support 14 forming part of an xy translation stage 16. A
container 18 containing curable microlens forming liquid 20, having a nozzle 22, is mounted on an arm 24 of a z-axis actuator 26, which is lowered to dispense liquid and raised during re-positioning of the nozzle.
The z-axis actuator 26 and xy translation stage 16 5 together form a means for controllably changing the spatial relationship of the nozzle to the substrate.
The z-axis actuator 26 regulates the height of the nozzle above the substrate 10, while the xy translation stage regulates the horizontal location of the nozzle 22 on the substrate 10. Flow of liquid 20 from the container 18 and nozzle 22 is regulated by means of a dispenser 28. The xy translation stage 16 and z-axis actuator 26 are controlled by controller 32.
Microlenses are formed by lowering the nozzle 22 to the substrate surface 12, at which time the computer controller 32 triggers a pressure regulator in the dispenser 28 to momentarily increase the pressure inside the container 18. This causes a volume of liquid to be deposited on the substrate surface 12. When the desired amount of liquid has been dispensed on the surface 12 , the pressure regulator is triggered to lower the pressure in the container 18.
The nozzle 22 is then lifted off the substrate surface 12. An array of microlenses may be made by repeating the above procedure with the substrate 10 moved to a different position relative to the nozzle 22. The volume of curable microlens forming liquid dispensed per time unit, and hence the width of a microlens formed by the deposition of curable microlens forming liquid from the nozzle 22, is controlled by controlling pressure in the dispenser 28. The dispenser 28 operates by applying a regulated air pressure to the surface of the liquid contained in the container 18, forcing the liquid through the dispensing tip 30 of the nozzle 22. Control signals for the controller 32 may be supplied by joystick 34 or by computer 36, for example controlled according to the program filed with the United States Patent and Trademark Office as a microfiche appendix in United States patent no. 5,534,101, or, for the implementation of the methods according to the invention described and claimed in this patent document, in accordance with the program attached hereto as an appendix.
The curable microlens forming liquid 20 is preferably cured using liquid curing radiation, such as from UV source 38 with light guide 42 for delivering the light to the desired location. The source 38 of liquid curing radiation may also be moved over the surface of the substrate in a linear pattern by using the xy translation state. A microscope 44 may be used to inspect the manufacturing process.
The nozzle 22 is preferably formed from a tube of internal diameter less than about 100 um (as for example 50~rn), but may consist simply of a small aperture in a container. A syringe having barrel inside diameter 1 cm with a 100 um inside diameter tip has been found successful. A capillary tube may also be used as the nozzle 22 with liquid supplied from a pump (not shown). In such an instance, only the capillary need be moved, rather than the entire nozzle.
The curable microlens forming liquid 20 is preferably a W curable polymer (n between 1.5 and 1.6) such as Norland~ 68 optical adhesive (n = 1.54) that cures with low shrinkage when exposed to ultraviolet light. In this patent document, a curable microlens forming liquid is a liquid having the property that under known conditions, as for example exposure to ultraviolet light, it may undergo reactions that solidify the liquid to yield a material that is at least partially transparent to light.
During dispensing the tip 30 should be either in contact with the substrate surface or slightly above it. By contrast with the apparatus shown in Fig. 1, and described in United States patent no. 5,534,101, the W source is not positioned closed to the needle tip for curing. Rather, the lenses are dispensed on a flat surface, allowed to a settle for a period of time (about 30 mins.) to improve uniformity and are placed in a W eprom eraser for curing. The eprom eraser is a small compartment with an 8" fluorescent tube inside. This allows all the lenses to be cured uniformly.
The computer described in this application may be a NeXTStation running NeXTStep operating system version 2.1 or higher, available from NeXT Computer Inc., or compatible, the controller may be a Newport/Klinger MotionMaster 2000 with A/D, D/A
option, the actuator may be a Newport/Klinger BMCC
series with 76:1 gears, the translation stages may be Newport/Klinger MR series with 63 mm travel, the dispenser may be an EFD Inc., model 900 and the W
source may be a Logical Devices Inc. model QW-TB
eprom eraser, all of which products are commonly commercially available.
In United States patent no. 5,534,101, the nozzle 22 is shown to have an oblique orientation with respect to the surface of the substrate 10. In the microlens fabrication process of the present invention, it is preferred to form microlenses with the nozzle tip 30 parallel to the planar surface 12 of the substrate 10. The nozzle tip 30 shown in Fig. 2 is the annular face of the nozzle 22 that forms the axial extremity of the nozzle 22. The nozzle 22 itself may be at an angle, with the tip 30 also at an angle to the nozzle, but a tip 30 perpendicular to the axis of the nozzle is preferred. During deposition of a microlens, the nozzle tip 30 should lie in a plane parallel to the surface 12 and, after deposition of curable microlens forming material, the nozzle 22 is preferably removed from the surface 12 in a direction perpendicular to the surface 12 as shown by the arrow A. The object is to ensure that the curable microlens forming liquid detaches from all parts of the nozzle tip 30 at the same time as the nozzle tip 30 is moved away from the substrate. During deposition, curable microlens forming liquid should bridge the gap between the nozzle tip 30 and the surface 12, such that the curable microlens forming liquid does not fall freely between the nozzle tip 30 and the substrate 12.
If the nozzle tip 30 is not moved while curable microlens forming liquid is momentarily ejected from the nozzle 22, then a symmetrical, circular microlens is formed. In some case, however, anamorphic or elliptical lenses may be desirable, in which the resulting lens has two distinct focal lengths for both the major and minor axes of the elliptical lens. In this instance, the syringe tip is moved slightly in one transverse direction across the surface 12 immediately after momentarily ejecting curable microlens forming liquid from the nozzle 22 without lifting the nozzle tip 30 away from the curable microlens forming liquid. The nozzle tip 30 is then moved away from the surface of the substrate 12 in a direction perpendicular to the surface of the substrate 12 to separate the nozzle tip 30 from the curable microlens forming liquid. Fig. 3A shows a droplet 32 dispensed onto a substrate 10 by nozzle 22.
Fig. 3B shows movement of the nozzle 22 in a transverse direction indicated by the arrow A. The resulting anamorphic lens 34 is shown in Fig. 3C. The lens shown is approximately 258 x 311 ~tm and has an f/number of 3.06 x 3.60. Movement of the nozzle 22 should be less than the diameter of the lens, in the order of 10-100 Vim. Such lenses have utility for example in coupling a laser with a diverging elliptical output beam to to a circular fiber.
Arrays of microlenses may be produced by repeating the procedure of depositing a controlled volume of curable microlens forming liquid on the planar surface at different locations on the surface 12 to form droplets on the surface 12. The nozzle 22 is moved across the surface in between periods of depositing the droplets. The nozzle tip 30 should be detached from the curable microlens forming liquid before moving or translating the nozzle tip 30 across the substrate. It is preferred that the array of microlenses be allowed to settle to a uniform shape and then be cured by the application of curing radiation such as ultraviolet light. The length of time that the droplets should be allowed to settle is dependent on the degree of uniformity required and the properties, such as viscosity and surface tension, of the curable microlens forming liquid, rather than the dynamics of dispensing the liquid. For example, if the curable microlens forming liquid is NorlandT" 68 optical adhesive, then a settling time of 30 minutes after the last lens in an array is deposited has been found useful. Preferably, the settling time should be at least long enough for the last droplet deposited to settle substantially to a stable shape, that is, to reach equilibrium. Figs . 4 and 5 illustrate divergence 5 of focal length with rapid cure (Fig. 4) and uniform focal length when the droplets are allowed to settle (Fig. 5) .
The f/number of a microlens formed by ejection of a droplet of curable microlens forming 10 liquid onto a substrate depends on the contact angle between the droplet surface and the surface of the substrate. The contact angle depends on the ratio of the liquid/substrate and liquid/air surface tension.
F/number of a microlens may then be altered by changing the surface tension between the curable microlens forming liquid and the substrate. This may be accomplished by using different types of curable microlens forming liquid. In addition, this may be accomplished by altering properties of the surface layer, such as by spin coating different curable microlens forming liquids onto the surface layer, and manipulating the curing process for example the intensity of the curing radiation and the time during which the curing takes place. A typical relationship between curing time (hence surface tension of the surface layer of the substrate) and lens f/number is illustrated in Fig. 6 for Norland~ 65 optical adhesive lenses on Norland~ 65 optical adhesive cladding. Fig.
7 illustrates a similar relationship for NorlandT~ 68 optical adhesive lenses on Norland~" 65 optical adhesive cladding. Each different combination of curable liquid used for the lens and the curable liquid used to form the substrate layer will result in a different characteristic curve of substrate curing time verses f/number. The f/number of the microlens may be controlled by pre-selecting the type of curable microlens forming liquids and the surface tension of the curable microlens forming liquid. Other methods of forming the surface layer may be used that are suitable for forming a layer of optically transparent material on a substrate.
Parameters that affect the f number including the length and intensity of W curing, the settling time, the thickness of the substrate and the lens, the type of material used for the lens and substrate, spin time of the substrate (where a coating is spun onto the substrate) and batch to batch variation in the polymer used as the curable microlens forming liquid.
By use of the same optical adhesive, such as NOA'~ 65, as both substrate and lens making material, f numbers up to 16 and also greater than 16 may be obtained by controlling the curing time of the substrate. With different curable microlens forming liquids used to make the substrate coating and lens, a wide range of f numbers may be obtained.
The method of the invention may be used to form collimated beams from arrays of vertical-cavity surface-emitting lasers 50 (VCSEL) for example with the arrangement shown schematically in Fig. 8. The lenses 52 are dispensed on a transparent substrate 54 at a spacing corresponding to the measured spacing of the VCSEL 50. The dispensing apparatus can be reprogrammed to different spacings in a matter of seconds. After the lenses 52 are dispensed and cured, they are actively aligned to the emitting VCSELs 50 and the substrate 54 is fixed in place with epoxy on a structure 56 that supports the VCSELs 50.
Fig. 3C shows the outline of an anamorphic lens 34 produced as shown in Fig. 3B;
Fig. 4 is a graph showing uniformity of focal length for several lenses in an array where array is cured immediately after formation of the last lens;
Fig. 5 is a graph showing uniformity of focal length for several lenses in an array where the liquid droplets in the array were allowed to settle for 30 minutes before curing with W radiation;
Fig. 6 is a graph showing a typical relationship between curing time (hence surface tension of the surface layer of the substrate) and lens f/number;
Fig. 7 is a graph showing a second relationship between curing time of the substrate (hence surface tension of the surface layer of the substrate) and lens f/number; and Fig. 8 is a schematic showing application of an array of microlenses to collimate light from an array of lasers.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS:
Referring to Fig. 1 there is shown a prior art apparatus for forming a light guide on a substrate 10. The substrate 10 may be silicon dioxide, glass, lithium niobate or any semi-conducting material used for making electronic components . The substrate 10 has an upper planar surface 12, and rests on a support 14 forming part of an xy translation stage 16. A
container 18 containing curable microlens forming liquid 20, having a nozzle 22, is mounted on an arm 24 of a z-axis actuator 26, which is lowered to dispense liquid and raised during re-positioning of the nozzle.
The z-axis actuator 26 and xy translation stage 16 5 together form a means for controllably changing the spatial relationship of the nozzle to the substrate.
The z-axis actuator 26 regulates the height of the nozzle above the substrate 10, while the xy translation stage regulates the horizontal location of the nozzle 22 on the substrate 10. Flow of liquid 20 from the container 18 and nozzle 22 is regulated by means of a dispenser 28. The xy translation stage 16 and z-axis actuator 26 are controlled by controller 32.
Microlenses are formed by lowering the nozzle 22 to the substrate surface 12, at which time the computer controller 32 triggers a pressure regulator in the dispenser 28 to momentarily increase the pressure inside the container 18. This causes a volume of liquid to be deposited on the substrate surface 12. When the desired amount of liquid has been dispensed on the surface 12 , the pressure regulator is triggered to lower the pressure in the container 18.
The nozzle 22 is then lifted off the substrate surface 12. An array of microlenses may be made by repeating the above procedure with the substrate 10 moved to a different position relative to the nozzle 22. The volume of curable microlens forming liquid dispensed per time unit, and hence the width of a microlens formed by the deposition of curable microlens forming liquid from the nozzle 22, is controlled by controlling pressure in the dispenser 28. The dispenser 28 operates by applying a regulated air pressure to the surface of the liquid contained in the container 18, forcing the liquid through the dispensing tip 30 of the nozzle 22. Control signals for the controller 32 may be supplied by joystick 34 or by computer 36, for example controlled according to the program filed with the United States Patent and Trademark Office as a microfiche appendix in United States patent no. 5,534,101, or, for the implementation of the methods according to the invention described and claimed in this patent document, in accordance with the program attached hereto as an appendix.
The curable microlens forming liquid 20 is preferably cured using liquid curing radiation, such as from UV source 38 with light guide 42 for delivering the light to the desired location. The source 38 of liquid curing radiation may also be moved over the surface of the substrate in a linear pattern by using the xy translation state. A microscope 44 may be used to inspect the manufacturing process.
The nozzle 22 is preferably formed from a tube of internal diameter less than about 100 um (as for example 50~rn), but may consist simply of a small aperture in a container. A syringe having barrel inside diameter 1 cm with a 100 um inside diameter tip has been found successful. A capillary tube may also be used as the nozzle 22 with liquid supplied from a pump (not shown). In such an instance, only the capillary need be moved, rather than the entire nozzle.
The curable microlens forming liquid 20 is preferably a W curable polymer (n between 1.5 and 1.6) such as Norland~ 68 optical adhesive (n = 1.54) that cures with low shrinkage when exposed to ultraviolet light. In this patent document, a curable microlens forming liquid is a liquid having the property that under known conditions, as for example exposure to ultraviolet light, it may undergo reactions that solidify the liquid to yield a material that is at least partially transparent to light.
During dispensing the tip 30 should be either in contact with the substrate surface or slightly above it. By contrast with the apparatus shown in Fig. 1, and described in United States patent no. 5,534,101, the W source is not positioned closed to the needle tip for curing. Rather, the lenses are dispensed on a flat surface, allowed to a settle for a period of time (about 30 mins.) to improve uniformity and are placed in a W eprom eraser for curing. The eprom eraser is a small compartment with an 8" fluorescent tube inside. This allows all the lenses to be cured uniformly.
The computer described in this application may be a NeXTStation running NeXTStep operating system version 2.1 or higher, available from NeXT Computer Inc., or compatible, the controller may be a Newport/Klinger MotionMaster 2000 with A/D, D/A
option, the actuator may be a Newport/Klinger BMCC
series with 76:1 gears, the translation stages may be Newport/Klinger MR series with 63 mm travel, the dispenser may be an EFD Inc., model 900 and the W
source may be a Logical Devices Inc. model QW-TB
eprom eraser, all of which products are commonly commercially available.
In United States patent no. 5,534,101, the nozzle 22 is shown to have an oblique orientation with respect to the surface of the substrate 10. In the microlens fabrication process of the present invention, it is preferred to form microlenses with the nozzle tip 30 parallel to the planar surface 12 of the substrate 10. The nozzle tip 30 shown in Fig. 2 is the annular face of the nozzle 22 that forms the axial extremity of the nozzle 22. The nozzle 22 itself may be at an angle, with the tip 30 also at an angle to the nozzle, but a tip 30 perpendicular to the axis of the nozzle is preferred. During deposition of a microlens, the nozzle tip 30 should lie in a plane parallel to the surface 12 and, after deposition of curable microlens forming material, the nozzle 22 is preferably removed from the surface 12 in a direction perpendicular to the surface 12 as shown by the arrow A. The object is to ensure that the curable microlens forming liquid detaches from all parts of the nozzle tip 30 at the same time as the nozzle tip 30 is moved away from the substrate. During deposition, curable microlens forming liquid should bridge the gap between the nozzle tip 30 and the surface 12, such that the curable microlens forming liquid does not fall freely between the nozzle tip 30 and the substrate 12.
If the nozzle tip 30 is not moved while curable microlens forming liquid is momentarily ejected from the nozzle 22, then a symmetrical, circular microlens is formed. In some case, however, anamorphic or elliptical lenses may be desirable, in which the resulting lens has two distinct focal lengths for both the major and minor axes of the elliptical lens. In this instance, the syringe tip is moved slightly in one transverse direction across the surface 12 immediately after momentarily ejecting curable microlens forming liquid from the nozzle 22 without lifting the nozzle tip 30 away from the curable microlens forming liquid. The nozzle tip 30 is then moved away from the surface of the substrate 12 in a direction perpendicular to the surface of the substrate 12 to separate the nozzle tip 30 from the curable microlens forming liquid. Fig. 3A shows a droplet 32 dispensed onto a substrate 10 by nozzle 22.
Fig. 3B shows movement of the nozzle 22 in a transverse direction indicated by the arrow A. The resulting anamorphic lens 34 is shown in Fig. 3C. The lens shown is approximately 258 x 311 ~tm and has an f/number of 3.06 x 3.60. Movement of the nozzle 22 should be less than the diameter of the lens, in the order of 10-100 Vim. Such lenses have utility for example in coupling a laser with a diverging elliptical output beam to to a circular fiber.
Arrays of microlenses may be produced by repeating the procedure of depositing a controlled volume of curable microlens forming liquid on the planar surface at different locations on the surface 12 to form droplets on the surface 12. The nozzle 22 is moved across the surface in between periods of depositing the droplets. The nozzle tip 30 should be detached from the curable microlens forming liquid before moving or translating the nozzle tip 30 across the substrate. It is preferred that the array of microlenses be allowed to settle to a uniform shape and then be cured by the application of curing radiation such as ultraviolet light. The length of time that the droplets should be allowed to settle is dependent on the degree of uniformity required and the properties, such as viscosity and surface tension, of the curable microlens forming liquid, rather than the dynamics of dispensing the liquid. For example, if the curable microlens forming liquid is NorlandT" 68 optical adhesive, then a settling time of 30 minutes after the last lens in an array is deposited has been found useful. Preferably, the settling time should be at least long enough for the last droplet deposited to settle substantially to a stable shape, that is, to reach equilibrium. Figs . 4 and 5 illustrate divergence 5 of focal length with rapid cure (Fig. 4) and uniform focal length when the droplets are allowed to settle (Fig. 5) .
The f/number of a microlens formed by ejection of a droplet of curable microlens forming 10 liquid onto a substrate depends on the contact angle between the droplet surface and the surface of the substrate. The contact angle depends on the ratio of the liquid/substrate and liquid/air surface tension.
F/number of a microlens may then be altered by changing the surface tension between the curable microlens forming liquid and the substrate. This may be accomplished by using different types of curable microlens forming liquid. In addition, this may be accomplished by altering properties of the surface layer, such as by spin coating different curable microlens forming liquids onto the surface layer, and manipulating the curing process for example the intensity of the curing radiation and the time during which the curing takes place. A typical relationship between curing time (hence surface tension of the surface layer of the substrate) and lens f/number is illustrated in Fig. 6 for Norland~ 65 optical adhesive lenses on Norland~ 65 optical adhesive cladding. Fig.
7 illustrates a similar relationship for NorlandT~ 68 optical adhesive lenses on Norland~" 65 optical adhesive cladding. Each different combination of curable liquid used for the lens and the curable liquid used to form the substrate layer will result in a different characteristic curve of substrate curing time verses f/number. The f/number of the microlens may be controlled by pre-selecting the type of curable microlens forming liquids and the surface tension of the curable microlens forming liquid. Other methods of forming the surface layer may be used that are suitable for forming a layer of optically transparent material on a substrate.
Parameters that affect the f number including the length and intensity of W curing, the settling time, the thickness of the substrate and the lens, the type of material used for the lens and substrate, spin time of the substrate (where a coating is spun onto the substrate) and batch to batch variation in the polymer used as the curable microlens forming liquid.
By use of the same optical adhesive, such as NOA'~ 65, as both substrate and lens making material, f numbers up to 16 and also greater than 16 may be obtained by controlling the curing time of the substrate. With different curable microlens forming liquids used to make the substrate coating and lens, a wide range of f numbers may be obtained.
The method of the invention may be used to form collimated beams from arrays of vertical-cavity surface-emitting lasers 50 (VCSEL) for example with the arrangement shown schematically in Fig. 8. The lenses 52 are dispensed on a transparent substrate 54 at a spacing corresponding to the measured spacing of the VCSEL 50. The dispensing apparatus can be reprogrammed to different spacings in a matter of seconds. After the lenses 52 are dispensed and cured, they are actively aligned to the emitting VCSELs 50 and the substrate 54 is fixed in place with epoxy on a structure 56 that supports the VCSELs 50.
Another example of the flexibility of this technology is in the custom placing of microlenses for other multiple optical sources, such as stacked diode arrays, whose positions cannot be controlled to photolithographic resolution. By measuring the positions of the emitting areas and inputting this information to the dispensing software, one can build custom optics in a matter of minutes. Where glass lenses are preferred, the dispensed polymer lens shape may be transferred to the substrate material by reactive ion etching.
A person skilled in the art could make immaterial modifications to the invention described and claimed in this patent without departing from the essence of the invention.
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A person skilled in the art could make immaterial modifications to the invention described and claimed in this patent without departing from the essence of the invention.
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LA PRESENTE PARTIE DE CETTE DEMANDE OU CE BREVET
COMPREND PLUS D'UN TOME.
CECI EST LE TOME 4 DE , ~.
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THiS SECTION OF THE APPLICATION/PATENT CONTAINS MORE
THAN ONE VOLUME
THIS IS VOLUME OF
' NOTE: For additional volumes-pi~ase contact the Canadian Patent Office .
Claims (18)
1. A method of forming an optical element on a substrate, the substrate having a planar surface, using a nozzle having a nozzle tip, the method comprising the steps of:
A) positioning the nozzle tip sufficiently close to the surface that curable microlens forming liquid may form a bridge between the nozzle tip and the surface;
B) momentarily ejecting curable microlens forming liquid from the nozzle onto the substrate;
C) moving the nozzle tip across the surface of the substrate in a transverse direction immediately after momentarily ejecting curable microlens forming liquid from the nozzle without lifting the nozzle tip away from the curable microlens forming liquid;
D) moving the nozzle tip away from the surface of the substrate in a direction perpendicular to the surface of the substrate to separate the nozzle tip from the curable microlens forming liquid; and E) curing the curable microlens forming liquid to form an elliptical optical element on the surface of the substrate.
A) positioning the nozzle tip sufficiently close to the surface that curable microlens forming liquid may form a bridge between the nozzle tip and the surface;
B) momentarily ejecting curable microlens forming liquid from the nozzle onto the substrate;
C) moving the nozzle tip across the surface of the substrate in a transverse direction immediately after momentarily ejecting curable microlens forming liquid from the nozzle without lifting the nozzle tip away from the curable microlens forming liquid;
D) moving the nozzle tip away from the surface of the substrate in a direction perpendicular to the surface of the substrate to separate the nozzle tip from the curable microlens forming liquid; and E) curing the curable microlens forming liquid to form an elliptical optical element on the surface of the substrate.
2. A method of forming an optical element on a substrate, the substrate having a planar surface, using a nozzle having a nozzle tip, the method comprising the steps of:
A) positioning the nozzle tip adjacent the surface;
B) momentarily ejecting curable microlens forming liquid from the nozzle onto the substrate;
C) moving the nozzle tip away from the substrate to detach the nozzle tip from the curable microlens forming liquid;
D) moving the nozzle tip across the surface of the substrate;
E) repeating steps A-D until an array of microlenses is formed;
F) allowing the array of microlenses to settle while in liquid form to a uniform shape; and G) curing the curable microlens forming liquid that makes up the array of microlenses.
A) positioning the nozzle tip adjacent the surface;
B) momentarily ejecting curable microlens forming liquid from the nozzle onto the substrate;
C) moving the nozzle tip away from the substrate to detach the nozzle tip from the curable microlens forming liquid;
D) moving the nozzle tip across the surface of the substrate;
E) repeating steps A-D until an array of microlenses is formed;
F) allowing the array of microlenses to settle while in liquid form to a uniform shape; and G) curing the curable microlens forming liquid that makes up the array of microlenses.
3. The method of claim 2 further comprising:
providing an array of spaced apart light sources; and moving the nozzle tip according to the manner of step D to form an array of microlenses having a spacing between microlenses equal to the spacing between the light sources.
providing an array of spaced apart light sources; and moving the nozzle tip according to the manner of step D to form an array of microlenses having a spacing between microlenses equal to the spacing between the light sources.
4. The method of claim 3 further comprising aligning the array of microlenses to collimate light from the light sources.
5. The method of claim 2 in which each step D
further comprises moving the nozzle tip away from the substrate in a direction perpendicular to the surface of the substrate.
further comprises moving the nozzle tip away from the substrate in a direction perpendicular to the surface of the substrate.
6. The method of claim 5 in which the nozzle tip is not moved while curable microlens forming liquid is momentarily ejected from the nozzle.
7. An array of microlenses formed by the method of claim 2.
8. A method of forming an optical element on a substrate, using a nozzle having a nozzle tip, the method comprising the steps of:
forming a surface layer on the substrate;
positioning the nozzle tip sufficiently close to the surface that curable microlens forming liquid may form a bridge between the nozzle tip and the surface layer;
momentarily ejecting first curable microlens forming liquid from the nozzle onto the substrate;
moving the nozzle tip away from the surface layer to detach the nozzle tip from the curable microlens forming liquid; and curing the first curable microlens forming liquid to form an optical element on the surface layer.
forming a surface layer on the substrate;
positioning the nozzle tip sufficiently close to the surface that curable microlens forming liquid may form a bridge between the nozzle tip and the surface layer;
momentarily ejecting first curable microlens forming liquid from the nozzle onto the substrate;
moving the nozzle tip away from the surface layer to detach the nozzle tip from the curable microlens forming liquid; and curing the first curable microlens forming liquid to form an optical element on the surface layer.
9. The method of claim 8 in which forming the surface layer comprises:
spin coating a second curable microlens forming liquid onto the surface layer; and curing the second curable microlens forming liquid.
spin coating a second curable microlens forming liquid onto the surface layer; and curing the second curable microlens forming liquid.
10. The method of claim 8 in which forming the surface layer comprises:
forming a surface layer with a second curable microlens forming liquid; and curing the second curable microlens forming liquid.
forming a surface layer with a second curable microlens forming liquid; and curing the second curable microlens forming liquid.
11. The method of claim 10 in which the first and second light guide forming liquid have the same composition.
12. The method of claim 10 in which the first and second light guide forming liquid have different composition.
13. A microlens formed by the method of claim 8.
14. A microlens formed by the method of claim 9.
15. A method of forming an optical element having a pre-selected f/number on a surface of a substrate, using a nozzle having a nozzle tip and a first curable microlens forming liquid, wherein the f/number of the optical element has a known relationship to the surface tension of the surface of the substrate, the method comprising the steps of:
forming a surface layer on the substrate, wherein the surface layer has a surface tension selected to produce an optical element formed of the first curable microlens forming liquid and which has the pre-selected f/number;
positioning the nozzle tip adjacent the surface layer;
momentarily ejecting first curable microlens forming liquid from the nozzle onto the surface layer;
moving the nozzle tip away from the surface layer; and curing the first curable microlens forming liquid to form an optical element on the surface layer having the pre-selected f/number.
forming a surface layer on the substrate, wherein the surface layer has a surface tension selected to produce an optical element formed of the first curable microlens forming liquid and which has the pre-selected f/number;
positioning the nozzle tip adjacent the surface layer;
momentarily ejecting first curable microlens forming liquid from the nozzle onto the surface layer;
moving the nozzle tip away from the surface layer; and curing the first curable microlens forming liquid to form an optical element on the surface layer having the pre-selected f/number.
16. The method of claim 15 in which forming the surface layer comprises:
spin coating a second curable microlens forming liquid onto the surface layer; and curing the second curable microlens forming liquid.
spin coating a second curable microlens forming liquid onto the surface layer; and curing the second curable microlens forming liquid.
17. A microlens formed by the method of claim 15.
18. A method of forming an optical element on a substrate, the substrate having a planar surface, using a nozzle having a nozzle tip, with the optical element aligned with an array of spaced light sources, the method comprising the steps of:
A) positioning the nozzle tip adjacent the surface;
B) momentarily ejecting curable microlens forming liquid from the nozzle onto the substrate;
C) moving the nozzle tip away from the substrate to detach the nozzle tip from the curable microlens forming liquid;
D) moving the nozzle tip across the surface of the substrate by a distance equal to the spacing between the light sources;
E) repeating steps A-D until an array of microlenses is formed;
F) allowing the array of microlenses to settle while in liquid form to a uniform shape;
G) curing the curable microlens forming liquid that makes up the array of microlenses; and H) aligning the array of microlenses with respect to the array of light source to collimate light from the light sources.
A) positioning the nozzle tip adjacent the surface;
B) momentarily ejecting curable microlens forming liquid from the nozzle onto the substrate;
C) moving the nozzle tip away from the substrate to detach the nozzle tip from the curable microlens forming liquid;
D) moving the nozzle tip across the surface of the substrate by a distance equal to the spacing between the light sources;
E) repeating steps A-D until an array of microlenses is formed;
F) allowing the array of microlenses to settle while in liquid form to a uniform shape;
G) curing the curable microlens forming liquid that makes up the array of microlenses; and H) aligning the array of microlenses with respect to the array of light source to collimate light from the light sources.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2213327 CA2213327A1 (en) | 1997-08-19 | 1997-08-19 | Improvements in microlens fabrication |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2213327 CA2213327A1 (en) | 1997-08-19 | 1997-08-19 | Improvements in microlens fabrication |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2213327A1 true CA2213327A1 (en) | 1999-02-19 |
Family
ID=4161286
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2213327 Abandoned CA2213327A1 (en) | 1997-08-19 | 1997-08-19 | Improvements in microlens fabrication |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2213327A1 (en) |
-
1997
- 1997-08-19 CA CA 2213327 patent/CA2213327A1/en not_active Abandoned
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