Optical communications – Transmitter
Reexamination Certificate
2000-02-22
2004-10-12
Pascal, Leslie (Department: 2633)
Optical communications
Transmitter
C398S201000, C356S450000
Reexamination Certificate
active
06804470
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to signal propagation systems and, more particularly, to such systems in which a signal in the form of radiation, such as electromagnetic radiation, is propagated through a medium or through space, usually between a transmitter and a receiver. It should not be inferred, however, that the invention pertains only to communication systems. As will become apparent from this specification, the invention also has application to other signal propagation systems, such as the use of electromagnetic or particle radiation in the analysis of specimen structure.
In many situations in which an electromagnetic radiation signal is transmitted through a medium (including a vacuum), a relatively high level of energy is used to transmit the radiation signal. Moreover, it is almost uniformly accepted that high energy levels are needed for propagation of the radiation signal. Yet there are many applications in which it would be advantageous to reduce the transmitted energy level. Prior to the present invention, no one has been able suggest how this goal might be accomplished.
A notable example of an application appropriate to the invention is the transmission of data such as text, video, or audio, using electromagnetic radiation. With the prodigious volume of such information now being transmitted over ground-based transmitters and receivers and over satellite links, a substantial reduction in energy usage would be highly desirable. This reduction would be particularly advantageous when applied to a transmitter at a remote site, such as on a satellite, for which electrical power is severely limited. In other situations, it would be equally advantageous to provide a substantially increased signal range for a given power consumption.
Another class of applications relevant to this invention concerns the use of electromagnetic or particle radiation in the analysis of specimen structure. Such applications known in the art are inclusive of virtually the entire electromagnetic spectrum from radio waves through x-rays and of a wide variety of specimens. A specific example is the inspection of manufactured semiconductor structure. It would be desirable to accomplish this task with x-ray inspection beams having -an ultra-low energy content instead of the relatively high energy content that must presently be employed.
In one class of radiography applications, the specimen to be analyzed is subject to damage from energy deposited by an incident radiation beam. A goal that has eluded researchers in this area is to make use of physical properties of a specimen, such as refraction, reflection, or phase shifting, to analyze the specimen without concurrent energy deposition. The ultimate goal in specimen analysis is three-dimensional reconstruction of a specimen image without the use of energy in the incident beam.
It will be appreciated from the foregoing that there are variety of applications using radiation signal propagation for which it would be highly desirable to employ radiation of significantly reduced energy content, without commensurately reducing the detectability of information carried on the signal being propagated. The present invention, as will now be described, accomplishes this goal in an elegant, completely novel and, perhaps, revolutionary manner.
SUMMARY OF THE INVENTION
The principal object of this invention is to transmit and receive a radiation signal such as a radio wave in such a way as to significantly reduce the energy content of the signal, but without commensurately reducing the detectability of information carried on the signal. As will become apparent as the description proceeds, the nature of this invention is such that it may provide an important resolution of conflicting fundamental physical theories concerning the nature of electromagnetic radiation. Although this aspect of the invention disclosure may raise interesting, and even controversial, theoretical concerns, it is believed that the detailed structure of the present invention, and verification of its functionality, can be described independently of such theoretical concerns.
The multiplicity of operational uses for the invention yield several distinct but closely related systems. These various operational uses are in fields of application in which the normal energy content of an electromagnetic or particle radiation beam is inherently disadvantageous, or where totally new applications are made possible with significantly reduced beam energy.
The present invention relates to an energy-depleted radiation transmitter and receiver. While it is expedient to summarize the invention in terms appropriate to optical wavelengths, it will be appreciated that the invention is applicable over a wide range of the electromagnetic spectrum, and is equally applicable to particle radiation systems.
For the transmitter, in one of its simplest embodiments, two well-collimated coherent beams, as from a laser with a split beam, are caused to intersect with a small but finite relative angulation along nearly coincident trajectories. At the region of maximum intersection, an interference pattern is formed. This pattern may be a sequence of bright and dark bands. The origin of these bands resides with a lateral migration of energy flux within the intersecting beams toward regions where there is constructive interference and away from regions where there is destructive interference.
In the extreme for two interfering beams, the central region of a bright band may have a nearly doubled energy flux: compared to the average energy flux of the intersecting beams whereas the central region of a dark band potentially may have a nearly zero energy flux. As will soon become clear, the transmitter of the invention propagates radiation from at least one of these dark bands of depleted energy.
Because the invention is functional, it may be inferred that the dark band, although clearly energy depleted, nevertheless still has a wave-like attribute that can carry information, which is the essence of the present invention. The existence of this wave-like attribute may be demonstrated by a simple experiment, which is described in the following paragraphs.
A slit aperture, inserted into the beam path at the location of the interference pattern, initially is aligned with a bright band. The slit should be sufficiently narrow to pass only the central part of a bright band but not so narrow as to produce the Frauenhoffer condition for diffraction. With these restrictions on the slit and appropriate use of lenses in the beam path, the transmitted bright band readily is split into two distinct beams at a selected point sufficiently distant from the slit. This separation is feasible because the transmitted band is a composition of parts of the angularly converging slit-incident beams.
A simple photodetector receiver, situated at the selected distant point, readily measures the energy from the two beam spots on its photon-sensitive surface. The two beam spots appear as a pair of parallel elongated ovals approximately slit-shaped, as expected. The slit is then realigned to a dark band. The slit now appears to transmit nothing and this is apparently supported by an essentially zero reading of the photodetector receiver. Nevertheless, the apparatus is now in a configuration critical to the operation of this invention.
A third beam is split off of the initial coherent beam. Unlike the first two beams, which converged on the slit, the third beam is transmitted directly to the photodetector. The beam spot of the third beam encompasses the entire area where the previous two bright band elongated oval beam spots had been located. The expected energy of the third beam is, of course, measured by the photodetector, but an additional and remarkable phenomenon may be observed at the photodetector. The beam spot of the third beam on the photodetector surface now exhibits two parallel elongated oval interference patterns. Furthermore, these interference patterns are not brighter on average than the rest of the third beam spot
Mirell Daniel Joseph
Mirell Stuart Gary
Heal Noel F.
Pascal Leslie
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