This invention relates to micro optical devices and more particularly to a micro optical sensor and a method of sensing a parameter.
Cantilever-type devices are used in micro sensors. For example, in an accelerometer, displacement or deflection of a cantilever beam may be an indication of acceleration to be sensed or monitored. As another example, in a biological lab-on-chip application, deflection of the cantilever beam may be measured as an indication of a biological mass deposited on the cantilever beam.
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Accordingly, it is an object of the present invention to provide a micro optical device and a method of sensing a parameter with which the applicants believe at least some of the aforementioned disadvantages may at least be alleviated or which may provide a useful alternative for the known devices and methods.
According to the invention there is provided a micro optical device comprising:
The movable member may comprise a diaphragm or membrane, for example. In a preferred embodiment of the invention, the movable member comprises a cantilever beam.
The other part of the body may comprise a base and the cantilever beam may be supported on the base by a support, to overhang the base.
The movable member may be made from any suitable material and in a preferred embodiment, the movable member is at least partially made from a semiconductor material.
The base and movable member may be integrally formed from the semiconductor material.
The semiconductor material may be a direct band-gap semiconductor material. Alternatively, the semiconductor material may be an indirect band-gap semiconductor material. The indirect band-gap semiconductor material may comprise silicon.
The base may comprise bulk silicon, the cantilever beam may comprise a first part of a layer of silicon provided on the bulk silicon by a silicon on insulator (SOI) technology and the support may comprise a first part of an intermediate isolation layer provided by the SOI technology.
The optical element may be mounted in or on the movable member, but preferably is integrally formed with the movable member.
The optical element may comprise an optical detector.
Alternatively, the optical element may comprise an optical source such as an electroluminescent device (for example a semiconductor pn junction or a thermal element) or a device comprising a photo-luminescent material which emits light after having been excited by another optical source. The light source used to excite the photo-luminescent material may be integrated with the body or may be external thereto.
In a preferred embodiment, the cantilever beam is made of a semiconductor material and the optical source comprises at least one junction between a first part of the movable member of a first doping kind and a second part of the movable member of a second doping kind. The first doping kind may be p-type and the second doping kind may be n-type.
In one embodiment, the cantilever beam may comprise a first part and a second part extending away from the support to meet at the at least one junction towards corresponding distal ends of the first and second parts of the movable member.
The device may comprise an optical detector for cooperating with the optical source.
The optical detector may be provided on a separate body. In other embodiments, the optical detector may be integrally formed with the body.
The device may comprise an optical mirror between the optical source and the optical detector. The optical mirror may be external of the body or may form part of the body and the optical detector may be provided on the body. The optical detector may be provided in the bulk silicon.
In another embodiment, the optical detector may comprise a second part of the SOI layer of silicon and may be supported on the bulk silicon by a second part of the intermediate isolation layer.
In yet other embodiments, the device may comprise an optical path extending in one straight line between the optical source and the optical detector.
The optical detector may be provided in the bulk silicon. The optical detector may be provided laterally spaced from the cantilever beam. Alternatively, the cantilever beam may extend over the optical detector.
In another embodiment, the optical detector may comprise a second part of the SOI layer of silicon and may be supported on the bulk silicon by a second part of the intermediate isolation layer.
The optical detector may comprise a position sensitive detector. In addition or alternatively, the optical detector may comprise a spectrally sensitive optical detector.
Also included within the scope of the invention is a device comprising a body; the body comprising a movable member which is moveable relative to another part of the body; an optical element provided on the movable member; at least first and second spaced optical waveguides and a controllable power supply connected between the body and the movable member to deform the movable member and thereby to bring a selected one of the at least first and second wave guides into communication with the optical element.
The optical element may comprise any one or both of an optical source and an optical detector.
The at least first and second waveguides may comprise optical fibre.
According to another aspect of the invention there is provided a method of sensing a parameter comprising the steps of:
The parameter to be sensed may be any parameter that changes at least one of the physical dimensions, shape, configuration and optical characteristics of the movable member and/or the optical source integrated therewith. Parameters that deform or deflect the movable member or otherwise change the direction of emitted light include, but is not limited to, mass, acceleration, gravity, pressure and orientation. Other parameters include physical or chemical parameters that change optical characteristics such as, spectral absorption, transmission, dispersion or reflectivity of the movable member or the integrated optical source.
The invention will now further be described, by way of example only, with reference to the accompanying diagrams wherein:
a) and (b) are diagrammatic representations of a fourth example embodiment of the sensor device according to the invention;
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In the example embodiments described herein, the movable member comprises a cantilever beam 14 that is mounted on a base 26 of the body 12 to extend over the base. The moveable member may alternatively comprise a diaphragm or membrane, for example. The optical element 16 may be an optical source, such as an electroluminescent device (for example a thermal element) or a device comprising a photo-luminescent material, which emits light after having been excited by another optical source. The light source used to excite the photo-luminescent material may be integrated with the body or may be external thereto.
However, in the example embodiments herein described, the optical source 16 comprises one or more p-n junctions in a semiconductor material. The p-n junctions may be reverse or forward biased to generate photons, and the semiconductor material may be any direct or indirect band-gap material compatible with the semiconductor manufacturing process utilized. In the case of SOI (silicon on insulator) CMOS technology, the semiconductor material comprises silicon and the cantilever beam 14 comprises a first part of the active silicon layer of the SOI technology and a first part 20.1 of the underlying buried oxide (BOX) layer serves to support the cantilever beam towards one end thereof on the bulk material. The remainder of the BOX is removed or sacrificed at 18, to form the cantilever beam extending over the base of bulk material.
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Another example embodiment is shown in
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In the example embodiment of
It is known that mechanical stress (tensile or compressive) may alter the energy band structure of semiconductor materials, for example change the forbidden energy gap value between the conduction and valence bands of the material. Since the emission spectrum of semiconductor light emitting devices depends on the energy gap and energy band structure, in the device 10 in
In
Number | Date | Country | Kind |
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2010/05125 | Jul 2010 | ZA | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB11/53046 | 7/8/2011 | WO | 00 | 4/1/2013 |