Optical: systems and elements – Lens – With support
Reexamination Certificate
2000-02-24
2001-11-20
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With support
C359S819000, C359S872000
Reexamination Certificate
active
06320706
ABSTRACT:
FIELD OF THE INVENTION
The invention relates in general to positioning mounts for optical, opto-mechanical and electro-optical components, and in particular to positioning mounts that are adhesively fixated.
BACKGROUND OF THE INVENTION
Optical assemblies or components, for instance laser assemblies and optical cavities feature a number of components that need to be precisely aligned relative to each other.
A typical optical assembly consists mainly of a planar assembly platform on which a number of devices are positioned relative to each other. The devices are attached to pedestals that provide varying degrees of freedom in the positioning.
U.S. Pat. No. 4,466,102 describes a modular dye laser. The pedestals introduced in this patent are mainly stacked plates that can slide along the planar top surface of a modular assembly platform. No specific method is provided to fixate the pedestals in the defined test position.
U.S. Pat. No. 4,827,485 describes a diode pumped solid state laser that is placed on a pedestal including an adjustment mechanism of essentially two wobble plates that can be rotated against each other. The pedestal provides a limited vertical adjustment without any fixating feature.
To fixate optical assemblies or components in their designated position the pedestals are typically soldered onto the assembly platform. The soldering process places an unfavorable thermal load on the assembly. Soldering of the pedestals themselves is also hard to accomplish without disturbing the overall configuration. The overall configuration is defined by a number of individual mounts positioned in a friction resistant manner relative to each other.
UV-curing adhesives have been utilized to circumvent the problems associated with the soldering technique. Pedestals or mounts are at least partially made of translucent material such that a curing UV-light can be directed onto the adhesive film between the individual mounts.
U.S. Pat. No. 5,170,409 describes a laser resonator assembly that utilizes a translucent assembly platform on which the individual components of the laser resonator assembly are positioned. The individual components are adhesively attached to blocks, which are also translucent. The invention provides a simple method to position and fixate the individual components. The mounting method does not provide enough degrees of freedom that are necessary for a precise fixation in position and orientation of the individual optical components within the laser resonator assembly. Further, the beam has to travel through the adhesive junction and the mount. As a result, both the adhesive junction and the mount have to fulfill optical requirements, which limits there optimization regarding mechanical and thermal behavior.
Another shortcoming is that the adhesive has a relatively high resilience, which causes, in combination with a thick film application of the adhesive, that the blocks creep back towards the position prior to the positioning adjustment. Another shortcoming is that the shape defined adhesive fixation described in the patent does not provide a possibility to adjust the optical axes of the elements with respect to the optical plane of the laser resonator assembly. As a result, the glue gap is more or less wedge-like shaped, which eventually results in misalignment during the curing process and long term instability.
A further shortcoming is that adhesive junction of the optical elements is in the beam path of the laser. Hence, the attaching surfaces have to fulfill primarily optical properties, which do not allow them to be roughened. Yet, roughening an attaching surface enhances its wetting characteristic and allows a reliable thin film adhesive attachment. In addition, a wedge shaped cured adhesive eventually imposes an optical distortion to the beam.
Finally, a shortcoming of the patent is that the thermal loads imposed onto the optical elements result in a thermal expansion of the mount. The thermal loads result for instance from optical absorption of the adhesive and the mounting material through which the light travels. The thermal expansion changes the orientation of the optical axes of the optical elements.
Therefore, there exists a need for a simple and economical method and apparatus to position and fixate an optical element without the limitations described in the paragraphs above.
OBJECTS AND ADVANTAGES
It is a primary object of the present invention to provide a method and apparatus to precisely adjust and fixate an optical element.
It is a further object of the present invention to provide an optical element and a side mount in relational shapes that allow free positioning and orienting with five degrees of freedom.
It is a further object of the present invention to provide a method and apparatus to fixate an optical element with a radiation curing adhesive in a way such that a guided laser is not effected by the adhesive junction.
It is a further object of the present invention to provide a method and apparatus to fixate an optical element with thin film adhesive junctions.
It is a further object of the present invention to provide an angular adjustment possibility for the optical axis of an optical element relative to the optical plane of a laser resonator assembly.
It is a further object of the present invention to provide a method to fixate an optical element such that thermal expansion does not change the orientation of the optical axis of the optical element.
Finally, it is an object of the present invention to provide a mounting system for thermal isolation and/or bi-directional thermal control.
SUMMARY
The invention introduces a method to position and adhesively fixate an optical element with a minimal space requirement that is simple, fault tolerant and lasting. A system of a specifically shaped optical element and a specifically shaped side mount is introduced. The optical element can be any active or passive element e.g. a mirror. Both the mirror and the side mount have additional features that are necessary and/or assist in the positioning and fixating.
The preferred application of the present invention is for fabricating laser resonator assemblies (LRA). Never the less the present invention may be also applied too any optical systems, microwave and RF systems, fiber optic systems, telescopes, binoculars, satellite systems. In a LRA, a laser beam is typically guided by a number of optical elements that are positioned and fixated on an assembly plate. The precision, with which the optical elements are positioned and oriented determines among other influences the quality and efficiency of the LRA. To maximize the precision of an LRA the optical elements are mounted such that dimensional distortion because of thermal expansion of the main assembly plate remains low.
The assembly plate holds mainly a number of optical elements as for instance mirrors, lenses, prisms, optical filters, wave plates, linear crystals, non linear crystals, optical diodes, sensors, pinholes, beam dumps, gain media, modulators, passive filters, active filters, polarizers, shutters, reticles, diode lenses, diode lasers and any combination of the above. Optical elements may be optical, opto-mechanical and electro-optical components as known to those skilled in the art. All parts of a LRA must maintain their position over several thousand operational hours.
The assembly plate has a top surface, which is utilized as an attaching surface. To position and fixate optical elements, the invention introduces an aligning chuck that is connected to a conventional aligning gauge. The aligning chuck has a clamping feature that corresponds with two or more clamping surfaces with a distinct clamping portion of the mirror. The aligning chuck is preferably a vacuum chuck, which evacuates a portion of at least one clamping surface. Consequently, the mirror is pressed by the air pressure against that particular clamping surface and the friction between that clamping surface and the mirror establishes a rigid attachment between them.
The use of the vacuum chuck allows a simple attachment
Byer Mark
Conway George
Mitchell Gerald
Richard Derek J.
Lightwave Electronics
Lumen Intellectual Property Services Inc.
Mack Ricky
LandOfFree
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