Patent Application
20060049154
Many products contain components that are positioned relative to one another during a manufacturing assembly process. However, after initial positioning, it may be desired that these components be held in a fixed relative position. For example, many cameras (those embedded in wireless telephones for instance) have a fixed focal length. Accordingly, the camera modules, e.g., lens assembly components, may be adjustably focused during manufacturing and then locked for the life of the product.
Current approaches for facilitating adjustment during manufacturing and locking of camera components thereafter include threading a plastic part that holds the lenses (lens holder) into another plastic part that holds the imaging sensor (housing). The spacing between the lens assembly and the sensor is adjusted by turning the threaded engagement. When correctly positioned, UV cure epoxy is typically used to lock the two plastic parts together. A final baking step, such as may involve placing a plurality of parts assemblies into an oven for periods of minutes to hours, may be performed to fully cure the epoxy. The above adjustment and bonding steps are repeated individually for each camera manufactured.
Plastic welding techniques have been used in some industries for bonding plastic parts together in a manufacturing process. For example, laser based plastic welding has been utilized in the automotive industry where liquid and gas-tight joints are desired (e.g., headlight and taillight assemblies).
Plastic laser welding is a non-contact process wherein overlapping joints of separate parts are heated by laser energy and fused together, typically at speeds of from approximately 0.5 meters/minute to approximately 3 meters/minute. Although virtually all thermoplastics can be laser welded, specific material properties with regard to the absorption and transmission of the laser radiation are required for the process to be successfully applied. Specifically, conventional laser welding techniques require an outer overlapping plastic layer to be transparent and the inner overlapping layer to opaque to absorb the laser radiation, thereby allowing the inner overlapping layer to heat to the melting point and bond with the outer overlapping layer when laser energy is applied. Additionally, a good fit between the parts to be joined is typically required to ensure proper bonding and high weld strength.
The present invention is directed to systems and methods which utilize laser plastic welding techniques in bonding camera assembly components after their adjustment to a desired relative position.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
Directing attention to
The embodiment of lens holder 111 and housing 120 illustrated in
Embodiments in accordance with the invention implement different configurations for the interface between lens holder assembly 110 and housing 120. For example, the embodiment of
Embodiments in accordance with the invention provide an interface between lens holder assembly 110 which itself may provide a locking engagement between lens holder assembly 110 and housing 120. For example, the embodiment of
Embodiments in accordance with the invention, once a desired relative position of lenses and aperture 112 and sensor 130 is obtained through adjusting the relative positions of lens holder assembly 110 and housing 120, laser energy is applied to bond at least a portion of lens holder 111 to housing 120 through a weld formed when the materials thereof heat to their melting point. For example, a beam from a laser which radiates in the infra-red spectrum may be focused on a portion of housing 120 which overlaps a portion of lens holder 111 to provide a weld.
In order to provide a bond of suitable strength to reliably maintain the desired relative position, embodiments in accordance with the invention employ compatible materials (e.g., materials, such as the same or very similar polymers, which can flow together and adhere to each other when at or above the melting point) between lens holder 111 and housing 120, or at least with respect to the overlapping portions thereof where a weld is to be formed. According to one embodiment, lens holder 111 and housing 120 are both comprised of polycarbonate. However, embodiments in accordance with the invention may use other materials (e.g., thermoplastics such as acrylic, polystyrene, polyamide, acrylonitrile-butadiene-styrene (ABS), and the like) having a melting point achievable through the application of laser energy for relatively short periods of time (e.g., 1-4 seconds), provided the materials of lens holder 111 and housing 120 are compatible with respect to providing a suitable weld bond.
Lens holder 111 and housing 120 of embodiments in accordance with the invention are further adapted to facilitate application of a laser plastic welding process. According to one embodiment, the material of housing 120 is adapted to be transparent or translucent to the wavelength of light emitted by a laser used in the laser plastic welding process, whereas the material of lens holder 111 is adapted to be absorptive of the wavelength of light emitted by a laser used in the laser plastic welding process. Accordingly, laser energy may be passed through housing 120 and absorbed by lens holder 111, thereby causing a portion of lens holder 111 to heat to its melting point (this process often being referred to as “transmission welding”). A portion of housing 120 adjacent to that portion of lens holder 111 heated to its melting point may also be heated to its melting point. For example, a portion of housing 120 may be heated to its melting point through heat conducted/reflected from lens holder 111. Additionally or alternatively, a portion of housing 120 may be heated to its melting point through heat absorbed by housing 120 not being perfectly transparent with respect to the laser energy.
Although comprising a material which is transparent or translucent to the wavelength of light emitted by a laser used in the laser plastic welding process, embodiments of housing 120 are opaque to visible light. Specifically, because housing 120 comprises a camera assembly housing in association with a light path used in imaging, it is desirable to control the infiltration of this path by ambient light during its operation as a camera. Accordingly, the material of housing 120 of embodiments blocks wavelengths of visible light, although passing (or more readily passing) wavelengths of the laser output. For example, a pigment, such as a red pigment, may be added to a polycarbonate base material to provide acceptable transmission qualities with respect to infra-red laser emissions while blocking visible light (or some portion thereof) sufficiently to facilitate camera operation. The use of such a pigment to block some portion of visible light may be particularly useful in some configurations, such as where a black-and-white image is being captured and/or where a colored filter, corresponding to the pigment used, is implemented with respect to the sensor.
Laser energy transmissive and laser energy absorptive properties may be provided in a number of ways, including chemically and structurally. For example, a base polymer, such as polycarbonate, utilized with respect to each of lens holder 111 and housing 120 may be acceptably IR translucent/transparent. Accordingly, lens holder 111 may be chemically adapted to exhibit desired absorptive properties through introduction of an additive, such as carbon black, to the base polymer.
According to another embodiment, housing 120, although perhaps not being acceptably IR translucent, is structurally adapted to allow laser energy to be applied very near an interface between housing 120 and lens holder 111. For example, in the embodiment of
Laser energy used in providing bonding welds according to embodiments in accordance with the invention may be applied to one or more points or positions as determined to provide a bond of suitable strength. For example, where laser plastic welding techniques of the present invention are used to provide a bond for holding the relative position of components to facilitate employing a different bonding technique, such as heat-cured or time-cured epoxy, a single or a few bonding welds may be used. Moreover, these welds may be relatively small, e.g., the laser energy applied in a very short burst (such as on the order of 0.5-2 seconds), depending upon the laser power and beam spot diameter, to melt and thus weld only a very small area, because a primary bond may be provided by a different bonding technique. However, where laser plastic welding techniques of the present invention are used to provide a sole source bond for holding the relative position of components, a larger number of bonding welds may be used. For example, one embodiment in accordance with the invention uses at least 3 bonding welds, such as may be substantially equally spaced about the overlapping interface of the components, in order to reliably fix the relative position of the components.
Bonding welds according to embodiments in accordance with the invention may be point welds (e.g., “tack” welds) or running welds (e.g., “seam” welds). For example, one or more of the aforementioned at least 3 bonding welds may comprise a point weld resulting from application of laser energy to corresponding points for a period of time, such as on the order of 0.5-4 seconds. Additionally or alternatively, one or more of the aforementioned at least 3 bonding welds may comprise a running weld resulting from relative movement between the assembly and the laser beam during application of laser energy, such as may result in welding speeds of from approximately 0.5 mm/second to approximately 5 mm/second. Although running welds may involve more time to accomplish than point welds, running welds may be desirable in some situations, such as where a seal against gas, liquid or light infiltration is to be provided by the bonding weld.
Directing attention to
Optical element 521 may comprise a beam splitter operable to substantially equally split the energy of the laser output beam into multiple beams. Such laser beams are directed to illuminate selected portions of housing 120 and provide a welding bond using optical elements 522, such as may comprise mirror surfaces. Specifically, a first beam may be directed to a surface of housing 120 by optical element 521, a second beam may be directed to a surface of housing 120 by a first optical element 522, and a third beam may be directed to a surface of housing 120 by a second optical element. Accordingly, system 500 may be operated to activate laser 510 to emit a single pulse of sufficient duration, e.g., 1-4 seconds, and provide multiple laser plastic welds to bond lens holder 111 to housing 120.
Although the use of a beam splitter and mirror surfaces has been discussed above, embodiments in accordance with the present invention may utilized any number of configurations for delivering laser energy to components to be bonded. For example, laser 510 may illuminate one or more portions of housing 120 without the use of a beam splitter. According to one embodiment, optical element 521 comprises a scanner, e.g., a rotating or moving mirror surface of suitable shape, to direct the output of laser 510 toward one or more positions on housing 120. Such a scanner may be useful in providing running welds, as described above, in addition to or in the alternative to point welds, also as described above. Of course, in addition to or in the alternative to providing optics to direct the output of laser 510, embodiments of the invention may utilize relative movement with respect to laser 510 and a camera component assembly to provide illumination of portions of housing 120. Embodiments in accordance with the invention may provide such illumination without the use of optics assembly 520, if desired. Moreover, embodiments in accordance with the present invention may use multiple lasers to provide laser energy for bonding welds as described herein.
Directing attention to
At block 602 the relative position of camera components is adjusted. For example, lens holder assembly 111 may be moved with respect to housing 120 to provide a desired focal length between lenses 112 and sensor 130.
At block 603 laser energy is applied to provide a bonding weld between camera components. For example, laser 510 may be energized to emit an IR beam focused on one or more points on housing 120. This energy may pass through housing 120 sufficiently to reach corresponding points on lens holder 111, where the energy is absorbed. This energy may be absorbed sufficiently and applied a sufficient amount of time to cause the points on lens holder 111 to reach the melting point of the material. Additionally, sufficient energy may be absorbed by, or conducted to, points on housing 120 interfacing with the aforementioned points on lens holder 111, thereby allowing the material of each component to flow, intermingle, and provide a weld.
At block 604 post-laser bonding manufacturing activity is performed. For example, additional components of the camera may be assembled, the camera may be tested, etcetera. Where bonding techniques in addition to laser plastic welding are used in bonding the camera components, additional bonding activity may be performed at block 604. For example, curing activity with respect to an epoxy resin, such as to apply heat cure, allow time to pass, or apply UV energy, may be performed (or the addition of an adhesive).
From the above it can readily be seen that laser plastic welding according to embodiments in accordance with the present invention provides a bond which may be applied very quickly and which provides sufficient holding of a desired relative position of components to facilitate further manufacturing processing immediately thereafter. Accordingly, significant time (e.g., several to many seconds) may be saved in the manufacturing of camera assemblies by employing the concepts of the present invention. In a high-volume manufacturing environment, such time savings can have a large impact on the manufacturing cost. Moreover, the use of laser plastic welding according to embodiments in accordance with the present invention may be relied upon to avoid contamination of lenses or sensor surfaces of camera assembly when bonding camera components together. Such camera assemblies may comprise any number of different camera types, including low cost digital cameras such as are now common in cellular telephones, high quality digital cameras, film cameras, and even video cameras.
Although embodiments in accordance with the invention have been described with reference to cameras and camera components, the concepts of the present invention are applicable to a number of different assemblies benefiting from precise adjustment before bonding. Embodiments in accordance with the invention are particularly useful with respect to assemblies wherein opacity with respect to visible light is desired with respect to the bonded components.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
The present application is related to co-pending and commonly assigned U.S. patent application Ser. No. 10/870,215 entitled “Cam-Locking Positioning Mechanism,” filed Jun. 17, 2004, the disclosure of which is hereby incorporated herein by reference.
