MEMS optical isolators

Details MEMS optical isolators MEMS optical isolators

2000-02-29

2002-08-27

Kim, Robert H. (Department: 2882)

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

C250S234000, C250S23700G

Reexamination Certificate

active

06441360

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related to optical isolators utilizing micro-electromechanical systems (MEMS).
2. Description of the Related Art
Electromechanical devices combine electrical and mechanical attributes as in motors and magnetic relays. There are also opto-electronic devices which combine light generation and/or light detection with electronics, such as in optical transmitters and receivers. Optical isolators (“opto-isolators”) are typically used in applications where a non-electrical connection in an electrical system is needed, such as to provide electrical isolation between components of a system. Such uses are widespread in biology, chemistry, physics, medicine and engineering. In medicine, for example, medical equipment may be interfaced with a patient through sensors or probes that are further connected to monitoring apparatus. For safety, the sensors/probes must be electrically isolated from the monitoring apparatus to protect against voltage surges and spikes that could injure or harm a patient. This isolation is accomplished by utilizing opto-isolators that convert an electrical signal to an optical signal for receipt by an optical detector. After receipt, the optical signal is typically re-converted to an electrical signal (i.e. a photo-current is generated) for analysis or processing.
MEMS is a technology that exploits lithographic mass fabrication techniques of the kind that are used by the semiconductor industry in the manufacture of silicon integrated circuits. Generally, the technology involves preparing a multilayer structure by sequentially depositing and shaping layers of a multilayer wafer that typically includes a plurality of polysilicon layers that are separated by layers of silicon oxide and silico nitride. The shaping of individual layers is commonly performed by etching, which is itself generally controlled by masks that are patterned by photolithographic techniques. The technology may also involve the etching of intermediate sacrificial layers of the wafer to release overlying layers for use as thin elements that can be easily-deformed or moved.
MEMS technology has proven highly versatile and has been used to form a wide variety of miniature devices varying in size from millimeters to microns. MEMS technology is discussed, for example, in a paper entitled “MEMS the Word for Optical Beam Manipulation”, published in
Circuits and Devices
, Jul. 1997, pp. 11-18.
MEMS technology allows for the production of opto-isolators which are smaller and operate with lower power consumption than pre-existing designs.
SUMMARY OF THE INVENTION
The present invention is directed to an optical isolator for selectively conveying an optical signal along an optical path from a signal source to a detector spaced from the source. This functionality is accomplished by generating an optical signal from the signal source and directing it to a MEMS device positioned in the optical path between the source and detector. The MEMS device includes a moveable element which, when activated, will selectively direct the optical signal between the source and detector.
In one embodiment, the moveable element is a shutter which can be moved to a position directly in the optical path for preventing or limiting the detection of the optical signal by the detector, and out of the optical path for allowing detection of the optical signal.
In another embodiment, the moveable element is a MEMS tilt mirror operable for providing a variable optical signal attenuator. By selectively controlling an amount of tilt applied to the tilt mirror, the amount of light directed to the detector can be varied.
In yet another embodiment, aperture elements are used to configure the shape of the optical signal. A source aperture is disposed between a moveable MEMS element and an optical source for shaping the optical signal prior to receipt by the MEMS element. A detector aperture may also be included between the moveable MEMS element and the optical detector.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.


REFERENCES:
patent: 6137105 (2000-10-01), Drobot et al.
patent: 6201629 (2001-03-01), McClelland et al.

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