Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2002-03-15
2004-07-20
Duverne, J. F. (Department: 2839)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
Reexamination Certificate
active
06764226
ABSTRACT:
The present invention relates to an improved device for housing a planar optical component for use in chemical sensing for example.
New chemical sensor technologies using optical techniques (in particular interferometric techniques) are providing new high performance devices. Whilst these devices are relatively simple in terms of components, the tolerances required in the assembly-procedure can be extremely onerous. Of these, end illuminated interferometric devices are perhaps the most demanding. In such cases, sub-micron misalignment between the electromagnetic radiation source (typically a collimated, focussed laser) and the sensor substrate itself may be sufficient to prevent its correct operation.
There are several situations which may lead to distorted output from a conventional device. Thus, the light beam may pass over the top of the planar optical component and distort the output received by-the detector. Similarly, where the device comprises a planar sensing waveguide and a planar reference waveguide, if the light misses a waveguide or fails to illuminate both equally, the output may be lost or distorted. Thus, if any of the components (eg light source, lenses, polarisers, sensors etc) are misaligned by as little as 2×10
−7
metres (200 nm) the performance of the device will be adversely effected. The provision of a device which ensures that waveguides are illuminated equally without admitting stray light represents a significant technical challenge.
More generally, there is a need for sensor assemblies of simpler construction and improved reliability. The range and applicability of chemical sensors could be greatly enhanced if it were possible to achieve lower manufacturing costs and greater robustness. An important consideration in developing suitable devices is temperature management. This imposes various design constraints related to the thermal mass of areas requiring insulation and the disposal of unwanted heat into the environment.
The present invention seeks to provide an improved device for housing a planar optical component such as a chemical sensor which is-capable of ultra high precision temperature control. The device is advantageously robust and gives enhanced signal to noise ratios (sensitivity). Moreover, the invention seeks to provide an optical (interferometric) chemical sensor device which is simple to machine and assemble and fault tolerant in terms of construction errors and which may be used to obtain reliable information relating to the changes occurring within the device.
Thus viewed from one aspect the present invention provides a device comprising:
an optical assembly adapted to mount a planar optical component (eg a sensor) so as to define a longitudinal path through the device in which the planar optical component is effectively exposed in free space and including guiding means for correlating along said longitudinal path the position of said planar optical component and of a source of electromagnetic radiation, whereby to expose said planar optical component to said electromagnetic radiation along said longitudinal path whilst substantially eliminating stray electromagnetic radiation,
wherein the optical assembly comprises a cavity which permits access to a face of the planar optical component or a face of a base with which the planar optical component is in intimate thermal contact whereby to enable an inner temperature controller to be positioned in thermal contact with the planar optical component for controlling the temperature of the planar optical component.
The inner temperature controller is capable of permitting fine temperature control of the planar optical component (eg sensor) and may be a heat pump or thermo-electric controller capable of providing or removing heat as desired. In a preferred embodiment, the inner temperature controller is an inner Peltier assembly capable of adding heat to or dissipating heat from the planar optical component. The inner Peltier assembly may comprise an inner Peltier mounted on an inner Peltier mount. The inner Peltier mount conveniently provides thermal mass. Preferably, the Peltier mount has a concave underside to optimise thermal contact with the planar optical component (or its base). The inner Peltier and inner Peltier mount may be provided with suitable insulation as desired.
Preferably the planar optical component is a sensor. In a preferred embodiment, the sensor is mounted on a sensor base and is in intimate thermal contact therewith. The base is typically made of stainless steel which advantageously provides thermal mass. Preferably the optical assembly is thermally insulating to permit the sensor, sensor base and Peltier mount to be in intimate thermal contact with the inner Peltier and thermally isolated from other components of the device.
Preferably the device is provided with a Peltier exhaust assembly which permits thermal transfer from the exhaust side of the inner Peltier to the environment.
Preferably the Peltier exhaust assembly comprises an exhaust plate positioned to allow thermal exchange with the environment. The exhaust plate is conveniently located at or near to an end of the device remote from the optical assembly. Preferably the Peltier exhaust assembly comprises means for thermally contacting the inner Peltier assembly with the exhaust plate. A thermally conducting strip may be used for this purpose (eg of copper). Preferably, the Peltier exhaust assembly comprises an exhaust guide (eg in the form of a ring) which is capable of fitting over the insulating collar of the laser module. The exhaust guide defines a slot into which the exhaust strip may be inserted.
In a preferred embodiment, the optical assembly and inner temperature controller are contained within a conducting sleeve. The conducting sleeve fulfils thermal management of the temperature sensitive components of the device eg provides a highly stable temperature environment for the inner temperature controller, provides precision temperature control for peripheral components such as the laser diode, provides a thermally stable environment for temperature control electronics and controls the temperature of incoming gases or liquids through the inlet and outlet ports. All these functions contribute to the temperature of the planar optical component being contained within desirable limits (typically the target control span is 20 micro Kelvin).
In a preferred embodiment, the conducting sleeve comprises a heat shroud which is typically made of copper. The heat shroud is preferably provided with an opening which is suitably disposed to coincide with the cavity in the optical assembly. This advantageously allows the inner Peltier assembly to be inserted in the optical assembly, after the optical assembly has been inserted in the conducting sleeve (eg heat shroud).
Preferably, the heat shroud comprises an integral laser module holder for inserting a laser module. Preferably the laser module holder is provided with an outwardly disposed insulating collar. Preferably the electronics are housed within the heat shroud.
Preferably the device comprises an outer temperature controller-which permits-coarse temperature control of for example the conducting sleeve, laser module, laser module holder, the exterior parts of the optical assembly and the electronics. The outer temperature controller is thermally independent of the inner temperature controller. The outer temperature controller conveniently takes the form of an outer Peltier assembly. Preferably, the outer Peltier assembly is provided externally of the restraining sleeve which is provided with an aperture to enable exposure of an effective area of the conducting sleeve to achieve thermal contact with the outer Peltier assembly.
Preferably, the device is provided with a means for urging the Peltier exhaust assembly onto the inner Peltier assembly. For example, a restraining sleeve is added outwardly of the heat shroud to force the Peltier exhaust assembly onto the inner Peltier assembly at one end and the exhaust plate at the other.
A preferred device o
Cross Graham
Freeman Neville John
Duverne J. F.
Fairfield Sensors Limited
Howrey Simon Arnold & White L.L.P.
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