Optics: measuring and testing – By alignment in lateral direction
Reexamination Certificate
2002-03-29
2004-06-29
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By alignment in lateral direction
C356S400000
Reexamination Certificate
active
06757063
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and apparatus for the alignment and assembly of opto-electronic components in general and, more particularly, to precision alignment and assembly of microelectromechanical (“MEM”) components for use in fiber-optic networks.
BACKGROUND OF THE INVENTION
In order to facilitate the large volume production of fiber-optic telecommunication assemblies, it is necessary to develop high productivity methods for manufacturing precision opto-mechanical assemblies. This includes avoiding, as much as possible, (1) the need to actively align components using measured optical performance as feedback, and (2) the need to maintain high mechanical tolerances during assembly so as to achieve the required optical performance.
The assembly of fiber-optic telecommunication components often include the alignment of an optical element (e.g., an optical filter, an optical switch pump laser, a Fabry-Perot tunable filter, a vertical cavity surface emitting laser, etc.) to a lens (or a system of lenses) which directs light to or from the optical element. Significantly, many new MEM-based devices of the sort which may be used in fiber-optic component assemblies have a well-defined geometric pattern in a plane perpendicular to the optical axis of the device. See, for example, pending prior U.S. patent application Ser. No. 09/105,399, filed Jun. 26, 1998 by Parviz Tayebati et al. for MICROELECTROMECHANICALLY TUNABLE, CONFOCAL, VERTICAL CAVITY SURFACE EMITTING LASER AND FABRY-PEROT FILTER, which patent application discloses tunable Fabry-Perot filters and tunable vertical cavity surface emitting lasers (VCSEL's). The fact that many new optical devices have the aforementioned well-defined geometric patterns opens up new possibilities for utilizing machine vision systems to assist in the precision alignment and assembly of fiber-optic components.
Some known methods for assembling lens systems utilize the imaging of light propagating through a machine vision system to measure the centers of lenses in the assembly. However, these methods do not involve imaging or utilizing the images of any geometrical features of the components that are being assembled.
Other assembly methods are known in which the alignment of components is based solely on images of the geometrical features of those components. In these latter types of alignment techniques, the component is imaged before it is positioned in its assembly rather than during the positioning operation. However, such alignment methods are highly susceptible to positioning errors due to any movement that occurs after imaging, and also due to movement that occurs while positioning the component. Very precise positioning mechanisms can be utilized to reduce the errors induced by these movements. However, these high precision positioning mechanisms add significantly to the cost of manufacturing the overall product.
SUMMARY OF THE INVENTION
As a result, one object of the present invention is to provide novel apparatus for the precise alignment and assembly of opto-electronic components.
Another object of the present invention is to provide a novel method for the precise alignment and assembly of opto-electronic components.
With the above and other objects in view, as will hereinafter appear, there is provided a method for aligning a lens and an opto-electronic device for assembly into a discrete package, the method comprising:
producing a light beam of a selected shape and wavelength and directing it along a selected path to an imaging device, whereby a first spot image of the light beam is formed on the imaging device;
recording the first spot image produced on the imaging device;
determining the coordinates of the center of the first spot image;
positioning a lens so that (a) it intersects the axis of the light beam and (b) its center axis extends substantially parallel to the axis of the light beam, whereby the light beam passes through and is modified by the lens and a second spot image of the modified light beam is formed on the imaging device;
recording the second spot image produced on the imaging device;
determining the coordinates of the center of the second spot image;
moving, while the light source is energized, the lens laterally of the light beam until the center of the second spot image coincides with the center of the first spot image;
positioning a selected opto-electronic device with an optical axis between the lens and the imaging device so that (a) it is adjacent to the lens, (b) it intersects the center axis of the light beam and (c) its optical axis extends substantially parallel to the axis of the light beam;
producing, while the light source is de-energized, an image of the opto-electronic device on the imaging device;
recording the image of the opto-electronic device;
comparing the image of the opto-electronic device with a pre-recorded geometrical pattern and determining from such comparison the X and Y coordinates of the optical axis of the opto-electronic device; and
moving the opto-electronic device until the X and Y coordinates of its the optical axis coincide with the recorded coordinates of the second spot image.
In another aspect of the invention, there is provided an apparatus for aligning a lens and an opto-electronic device for assembly into a discrete package, the apparatus comprising:
a fixed light source for producing light of a selected wavelength, and optical means for transmitting that light as an initial beam;
a first manipulator for supporting a lens in the path of the initial beam and for moving that lens on command along mutually orthogonal X and Y axes that extend perpendicular to the initial beam, the lens being adapted to transmit and shape the initial beam so as to produce a modified beam;
a second manipulator for supporting an opto-electronic device in the path of the initial beam and for moving the opto-electronic device on command along mutually orthogonal X and Y axes that extend perpendicular to the initial beam;
a machine vision system comprising (a) an imaging device positioned to record an image of the initial beam, a lens-modified image of the initial beam produced by a lens carried by the first manipulator and a visible light image of an opto-electronic device carried by the second manipulator, and (b) a programmed means for generating a first error signal representative of the position of the center of the image of the lens-modified beam relative to the center of the image of the initial beam, and a second error signal representative of the position of the optical center of the opto-electronic device relative to the position of the center of the image of the lens-modified beam; and
means for applying the first and second error signals to the first and second manipulators, respectively, so as to (a) cause the first manipulator to move in the X and/or Y directions to the extent required to make the center of the lens-modified beam coincide with the center of the initial beam and (b) cause the second manipulator to move in the X and/or Y directions to the extent required to make the optical center of the opto-electronic device coincide with the center of the lens-modified beam.
And in another aspect of the invention, there is provided a method for aligning a lens and an opto-electronic device for assembly into a discrete package, the method comprising:
(a) providing: (1) a light source for producing a beam of light that emulates the light which will exist in the package during its intended operation, and optical means for shaping that beam, (2) first and second manipulators each adapted to support a component and to move the supported component along mutually orthogonal X and Y axes that are perpendicular to the optical axis of the beam of light, and (3) a machine vision system having an imaging device that is aligned with the light source, the machine vision system being electrically coupled to the first and second manipulators so as to electrically control operation of the manipulators;
(b) energizing the light source so as to produce an initial image
Kogan Yakov
McCallion Kevin J.
Sakhitab Farhang
Font Frank G.
Gorecki John C.
Lauchman Layla
Nortel Networks Ltd
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