Multiple laser optical systems and methods

Details Multiple laser optical systems and methods Multiple laser optical systems and methods

2000-11-28

2004-05-11

Rosenberger, Richard A. (Department: 2877)

Optics: measuring and testing

Position or displacement

Position transverse to viewing axis

C033S707000

Reexamination Certificate

active

06734981

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to the field of sensing. More specifically, the present invention relates to multiple laser optical sensing systems and methods.
BACKGROUND OF THE INVENTION
Previous approaches to addressing sensing needs have generally involved using a single light signal from a light source, such as a light emitting diode, and multiple detectors. In order to illuminate a large area in an environment using a single light source, two general methods are known. One approach typically involves emitting a broad light signal from the light source and detecting the signal with one of multiple detectors positioned throughout the environment. The other approach typically involves emitting a narrow light signal from the light source, spreading the signal around the environment by reflecting it off of a rotating mirror, for instance, and detecting the signal with one of multiple detectors positioned throughout the environment. While feasible both approaches typically require multiple detectors and are usually not power efficient as a result, yielding a low signal-to-noise ratio. A poor power-transfer ratio reflects this inefficiency as the individual detector that receives a light signal usually detects only a portion of the signal that was originally emitted. Consequently, the signal that was detected generally provides only limited information about a target being sensed in the environment. These approaches also tend to limit the size range of the target being sensed in an environment due to the nature of the single light signal.
The limitations of these previous approaches are often manifested in applications such as detecting the motion of a target in an environment. Many motion detection systems generally involve a line-of-sight operation, where at least one detector detects the motion of a target as the target breaks a beam of light emitted from a light source. In relatively simple applications, such as determining the presence or absence of a target, this approach generally suffices. For more complex applications, such as determining the direction of the target's motion, this approach proves less adequate. When a target moves across a single light signal emitted by a light source, the signal received by a detector gradually decreases as the signal blocked by the target gradually increases. This gradual change in signal detection typically requires a complex algorithm to determine the position of the target in the environment. Adding multiple detectors can provide more information and decrease the complexity of the algorithm required, although that introduces power inefficiencies as mentioned previously, as well as added cost associated with additional hardware.
The limitations of the aforementioned approaches also relate to applications involving target recognition. Many known systems, either for recognizing only specific targets or for mapping spatial characteristics of targets, involve spreading a light signal with a rotating mirror and/or using multiple detectors. Holograms may also be used to spread the light signal by dividing the signal into smaller light signals. An approach for detecting only specific targets involves emitting pulses of signals from a transceiver, receiving the signals that reflect off of a target, and comparing the received signals with preset signals reflected off of known targets. Information about the known objects is typically stored in a database. An approach for mapping a target involves superimposing light signals received by different detectors in the presence of a target and comparing the signals with respect to signals associated with the environment without the target.
While each of these approaches is feasible for a particular function, none is known to perform several functions. This deficit creates a need for a versatile system that is both power efficient and cost effective. Such a system could be capable of, for instance, detecting the presence or absence of any target or of a specific target, detecting the spatial characteristics of a target, detecting the motion of any target or a specific target, or detecting various characteristics about the motion of a target.
BRIEF SUMMARY OF THE INVENTION
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention, and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
An aspect of the present invention includes a multiple laser optical sensing system for detecting target characteristics using a vertical cavity surface emitting laser. The system can include a vertical cavity surface emitting laser structure with at least two emission apertures that could be defined by photolithography. A laser signal can be emitted into an environment from each of the emission apertures. The system can also include at least one detector that is operationally responsive to the vertical cavity surface emitting laser structure. Finally, the system can include a microprocessor that is operationally coupled to the detector(s). In operation, the vertical cavity surface emitting laser structure can emit at least two laser signals into the environment, which may be occupied by a target. At least one detector detects the laser signals once they have passed through the environment. The microprocessor can then determine target characteristics based on laser signals received by the detector(s). Within the same vertical cavity surface emitting laser structure, the laser signals emitted could be identical or not identical. Optics can also be added to the system, such that laser signals pass through at least one lens or reflect off of a mirror or mirrors after exiting the emission apertures.
An aspect of the present invention provides methods for detecting target characteristics transmissively or reflectively using a vertical cavity surface emitting laser. In a transmissive method, a vertical cavity surface emitting laser structure can statically emit at least two laser signals into an environment, which may be occupied by a target. The target can block at least one of the laser signals passing through the environment, and at least one detector can transmissively receive any of the signals not blocked by the target. A microprocessor can then determine target characteristics by comparing characteristics of the laser signals emitted by the vertical cavity surface emitting laser structure with characteristics of the signals received by the detector(s).
In a reflective method, a vertical cavity surface emitting laser structure can serially emit at least one laser signal at a time into an environment, which may be occupied by a target. At least one of the laser signals can reflect off of the target and can be detected by at least one detector. A microprocessor can then determine target characteristics by comparing temporal characteristics, of the laser signals emitted by the vertical cavity surface emitting laser structure with temporal characteristics of the signals received by the detector(s).
In any method of the present invention, a microprocessor could determine the size or shape of a target by determining which laser signals are received by a detector after different arrays of laser signals are emitted by a vertical cavity surface emitting laser structure. The microprocessor could also detect motion of the target in an environment by detecting changes in the array of laser signals that are blocked or reflected off of the target.
The novel features of the present invention will become apparent to those of skill in the art upon examination of the following detailed description of the invention or can be learned by practice of the present invention. It should be understood, however, that the detailed description of the invention and the specific examples presented, while indicating certain embodiments of the present invention, are provided for illustration p

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