USRE48338E1 - Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect - Google Patents

Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect Download PDF

Info

Publication number
USRE48338E1
USRE48338E1 US15/854,566 US201115854566A USRE48338E US RE48338 E1 USRE48338 E1 US RE48338E1 US 201115854566 A US201115854566 A US 201115854566A US RE48338 E USRE48338 E US RE48338E
Authority
US
United States
Prior art keywords
signal
optical element
reference signal
interference
medium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active, expires
Application number
US15/854,566
Inventor
Jean-François Morizur
Hans Bachor
Nicolas Treps
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cailabs SAS
Original Assignee
Cailabs SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cailabs SAS filed Critical Cailabs SAS
Priority to US15/854,566 priority Critical patent/USRE48338E1/en
Application granted granted Critical
Publication of USRE48338E1 publication Critical patent/USRE48338E1/en
Active legal-status Critical Current
Adjusted expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/0121—Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/06—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the phase of light

Definitions

  • the present invention relates to a method and a system for configuring a device for correcting the effect of a medium on a light signal having propagated through said medium.
  • the invention also relates to a method, a device and a system for correcting said effect.
  • the signal at the output of the medium is a disordered or blurred version of the light signal input to the medium.
  • the modification applied by the medium must be corrected in order to recover the information conveyed by the light signal.
  • a device comprising several reflexion elements separated by a static propagation medium may be used to realise any spatial transformation on a light signal (Programmable Unitary Spatial Modes Manipulation, Jean-Pierre Morizur, Lachlan Nicholls, Pu Jian, Seiji Armstrong, Nicolas Treps, Boris Hage, Magnus Hsu, Warwick Bowen, Jiri Janousek, Hans-A. Bachor).
  • Another object of the present invention is to provide a method and a system making it possible to efficiently correct the effect of a medium on a light signal having propagated through said medium.
  • Another object is furthermore to provide an industrially applicable method and a system making it possible to correct the effect of a medium on a light signal having propagated through said medium.
  • Another object is furthermore to provide a method and a system making it possible to correct the effect of a medium on a light signal having propagated through said medium in a faster and inexpensive fashion.
  • Yet another object of the invention is to provide a method and a system making possible a complete correction of the effect of a medium on a light signal having propagated through said medium.
  • Such objects are accomplished through a method for configuring a device to correct the effect of a medium on a light signal having propagated through said medium, said device comprising at least one optical element whose spatial phase profile is individually adjustable, said method comprising several iterations of the following steps:
  • medium it is meant a medium or a combination of media, each medium being a natural or artificial medium.
  • a single optical element comprising independent sections whose phase profiles are individually adjustable, may be used to perform several successive reflexions or phase changes, in order to avoid the use of several such optical elements.
  • the method according to the invention makes it possible to configure a device to efficiently and completely correct the effect of a medium on a light signal having propagated through said medium.
  • the present invention provides a method that is simple to implement.
  • the configuration of the correcting device is entirely based on the disordered signal propagated through the correcting device and doesn't comprise any computation of the transmission matrix of the medium.
  • the errors that may be caused by such a computation operation are avoided and the method according to the invention is industrially applicable, less expensive and less time consuming than the prior art techniques.
  • the reference signal may be propagated through the device in the opposite direction to that of the disordered signal.
  • the step of measuring an interference parameter may comprise a step of measuring for each optical element:
  • a pixel is defined as the smallest area of an optical element for which it is possible to modify the phase profile.
  • the interference parameter may comprise a parameter relative to the phase difference between the disordered signal and the reference signal.
  • the interference parameter may comprise a parameter relative to the phase of the interference signal at each pixel or zone of the optical element.
  • the interference parameter may comprise, for an optical element, a parameter relative to the intensity of the interference signal, more particularly the light intensity, for each pixel or zone of the optical element, or the total light intensity, of the interference signal obtained by interference of the reference signal and the disordered signal.
  • the total light intensity of the interference signal for an optical element corresponds to the sum of the intensities measured for all the zones or pixels of the optical element.
  • the light intensity of the interference between the disordered signal and the reference signal may be used to measure the powers and the phase difference between these two signals.
  • the method according to the invention may comprise a step to oscillate in time the overall phase of the reference signal and/or first signal.
  • Such a modulation makes the intensity of the interference between the disordered signal and the reference signal oscillate in time. For each zone of the optical element where the intensity of the interference is measured the local phase difference relative to the other zones between the reference signal and the disordered signal can be computed.
  • phase of the interference signal at each pixel or zone of the optical element with respect to a reference pixel or a predetermined phase reference is used to decide the necessary modification to the phase profile of this pixel or zone.
  • the step of modifying the spatial phase profile of an optical element may comprise modifying the phase delay applied by at least one zone and/or at least one pixel of said optical element to a light signal.
  • a feature of the method according to the invention is that the reference signal, the first signal or both the reference signal and the first signal may be modulated spatially before propagating through the medium and the correcting device.
  • the method according to the invention may comprise a step to modulate the intensity profile of the reference signal and/or first signal.
  • the method according to the invention may also comprise a step to produce the reference signal and the first signal from two or more spatially separated incoherent light sources. Indeed this incoherence is equivalent to a spatial modulation of the overall source.
  • Such a spatial modulation makes it possible to configure the device, more particularly the spatial phase profile of each optical element, so that any effect of any complex medium on any light signal is corrected. Indeed, if the reference and first signals were not spatially modulated, then the spatial profile of the reference and first signals would remain static. The correcting device would then be configured according to only one spatial profile and would be able to correct the disordered signal only for one spatial profile.
  • the method according to the invention may also comprise a step for measuring a visibility parameter.
  • an overall phase modulation applied to the reference signal or the disordered signal makes it possible to measure an interference visibility parameter between the reference signal and the disordered signal.
  • an interference visibility parameter may be measured at a given position, for instance before, after or in the correcting device as the interference visibility parameter measured between two light signals remains identical whatever the measurement position.
  • the reference signal is phase modulated before propagating through the correcting device.
  • An interference parameter is measured for each pixel of each optical element.
  • the measured interference parameter is the intensity of the interference signal.
  • the intensity of the interference signal measured at each pixel of an optical element oscillates in time.
  • phase difference between these oscillations and the reference oscillation measured at a pixel with high intensity is calculated.
  • phase difference By modifying the phase delay applied by each pixel of an optical element, the phase difference are reduced to 0 and all the oscillating interference signals measured for the optical element are synchronised. This synchronisation increases the visibility of the interference between the reference signal and the disordered signal.
  • the optimization step may be conducted individually for each optical element and one after each other whatever the order.
  • the method according to the invention may also comprise a step of generating the first signal and the reference signal from a unique light signal.
  • the light signal may be divided into two light signals, one being the first signal and the other the reference signal.
  • the invention also relates to a device for correcting the effect of a medium on a light signal having propagated through said medium, comprising at least one optical element whose spatial phase profile is individually adjustable and configured according to the configuration method according to the invention.
  • the two optical elements are separated by a combination of lenses and free space propagation.
  • At least one optical element is a spatial light modulator or a deformable mirror.
  • the invention also relates to a method for correcting the effect of a medium on a light signal having propagated through said medium, said method implementing a device comprising at least one optical element whose phase profile is individually adjustable, said method comprising:
  • the correcting method according to the present invention may also comprise at least one adjusting step for adjusting the configuration of the device if changes occur in the medium during the correcting phase.
  • a control light signal is sent regularly through the system to readjust the device, using the configuration method.
  • This control light signal can be different from the light signal used in the configuration phase.
  • the control light signal is sent through the output of the device, and is reflected at the input of the complex medium.
  • the control light goes through the correcting device, the medium, the medium again and finally the correcting device again.
  • the device corrects the effect of the medium. Additional small changes occurring in the medium can be corrected using the calibration method with the control light.
  • the invention also relates to a system for configuring a device for correcting the effect of a medium on a light signal having propagated through said medium, said device comprising at least one optical element whose spatial phase profile is individually adjustable, said system comprising:
  • the means for propagating the reference signal may be adapted to propagate the reference signal through the device in the opposite direction to that of the disordered signal
  • the system according to the invention may also comprise modulation means to introduce an overall phase modulation on the reference signal or the disordered signal before propagating said signal through the correcting device.
  • the system according to the invention may also comprise an element to modulate the spatial profile of the reference signal, the first signal or both these signals before they are sent in the medium or the correcting device.
  • the measuring means may comprise one CCD camera or one CCD camera for each optical element.
  • Such a CCD camera may be configured for measuring an interference parameter for each pixel of the optical element.
  • the system according to the invention may also comprise reflexion means to transmit to the CCD camera a part of the interference signal obtained by interference of the disordered signal and the reference signal.
  • the means for modifying the phase profile of an optical element may comprise at least one actuator for each optical element, more particularly an actuator for each zone or pixel of each optical element. Such actuators may be integrated to the optical elements.
  • the invention also relates to a system for correcting the effect of a medium on a light signal having propagated through said medium, said system comprising:
  • the invention also relates to a computer program comprising the instructions to implement the steps of a configuration method according to the present invention when said computer program is executed by a computer or computing means.
  • the phase profiles of each optical element of said correcting device may first be determined on a computer by simulation. When the correction if satisfactory, the phase profiles of each optical element is set and the device is then ready to use.
  • the methods, the device, the systems and the computer program according to the present invention may also be used to apply a given deformation to a light signal.
  • the given deformation is the deformation applied by the medium through which the first signal propagates.
  • the disordered signal thus obtained at the output of the medium is used as reference signal in the methods, device, systems and computer program according to the present invention.
  • the second signal identical to the first signal, is used as the signal to be modified by the methods, device, systems and computer program according to the invention so that said second signal is modified to be identical to the disordered signal.
  • the reference signal and the second signal are switched.
  • FIG. 1 schematically represents an example of a correcting device
  • FIG. 2 is a block diagram of an embodiment of the configuration method according to the invention.
  • FIG. 3 is a block diagram of an embodiment of the correction method according to the invention.
  • FIG. 4 schematically represents an embodiment of the correcting system according to the invention.
  • FIG. 5 schematically represents the means for measuring the amplitude of the interference signal for each pixel of an optical element
  • FIG. 6 schematically represents the amplitude of the interference signal measured for each pixel of an optical element before and after configuration.
  • FIG. 1 schematically represents an example of a correcting device.
  • the correcting device 100 comprises at least one input 102 and at least one output 104 .
  • the correcting device 100 comprises several optical elements 106 1 - 106 n .
  • Each optical element 106 has an adjustable spatial phase profile.
  • each optical element 106 may be a spatial phase modulator (SLM) or a deformable mirror (DM).
  • SLM spatial phase modulator
  • DM deformable mirror
  • Each optical element 106 is separated from another optical element 106 by free space propagation and a lens (not represented), which perform an optical transform.
  • a disordered signal is input to the correcting device 100 and propagates across the optical elements 106 one after another. After the last optical element 106 n , the disordered signal is corrected and the correcting device provides the corrected version of the disordered signal.
  • the several optical elements 106 1 - 106 n may be replaced by independent section of a single optical element, i.e. a spatial phase modulator or a deformable mirror.
  • FIG. 2 is a block diagram of an embodiment of the configuration method according to the invention.
  • the configuration method 200 comprises a first step 202 of generation of a light signal.
  • the spatial profile of the light signal is modulated using an accousto-optic modulator, a simple chopper or another mean to change the spatial profile of the light.
  • the spatial modulation may be random.
  • the light signal is divided into two identical light signals called the first signal and the reference signal.
  • the first signal is propagated through a medium, and thus a disordered signal is obtained at the output of the medium.
  • the reference signal is phase modulated.
  • the disordered signal and the reference signal are propagated through the correcting device, i.e. the optical elements, in opposite directions.
  • the propagation of the disordered signal and the modulated reference signal through each optical element generates an interference signal at each optical element, and more particularly at each pixel of each optical element.
  • step 212 an optimization of the interference between the disordered signal and the modulated reference signal is performed.
  • the optimization step 212 comprises a step 214 measuring an interference parameter, i.e. the light intensity of the interference signal, for each pixel of an optical element of the correcting device. For each pixel, the measured intensity of the interference signal oscillates due to the phase modulation of the reference signal. Thus, for a given optical element there are as many oscillating signals as pixel.
  • an interference parameter i.e. the light intensity of the interference signal
  • the optimization step 212 also comprises a step 216 for modifying the spatial phase profile of the considered optical element in order to synchronise all the measured oscillating signals.
  • the synchronisation for an optical element may be performed as follows.
  • a reference pixel is chosen among all the pixels of the optical element.
  • Steps 214 and 216 are realised for each optical element of the correcting device whatever the order. This condition is verified at step 218 that makes sure that steps 214 and 216 are realised for all optical elements of the correcting device.
  • a second interference parameter i.e. the interference visibility
  • the interference visibility value is tested.
  • other measurements can be used as termination parameters such as the contrast of the output image of the system, a local contrast of the output image, the fidelity to a desired intensity profile, the fidelity to a desired phase profile, the fidelity to a desired intensity and phase profile, the symmetry of the output image, the asymmetry of the output image, the phase differences measured at different points in the device, the intensity profiles measured at different points in the device.
  • the optimization step 212 is repeated until a satisfactory value of the interference visibility is obtained.
  • FIG. 3 is a block diagram of an embodiment of the correction method according to the invention.
  • the correction method 300 represented en FIG. 3 comprises a configuration phase 302 , configuring a correction device as the device 100 represented on FIG. 1 and realised according to the configuration method 200 represented en FIG. 2 .
  • the correction method 300 also comprises a correcting phase 304 , after the configuration phase 302 .
  • the correcting phase comprises a step 306 for correcting a disordered signal with the configuration device.
  • the correcting phase also comprises a step 308 for adjusting the configuration of the device if changes occur on the medium during the correcting step. Then the correcting step 306 is stopped. The adjusting step 308 is realised. When the adjusting step 308 is finished the correcting step 308 is continued.
  • FIG. 4 schematically represents a correcting system 400 according to the invention.
  • the correcting system 400 represented on FIG. 4 comprises a source 402 providing a spatially modulated light signal 404 .
  • the light signal 404 is divided into two equal and identical light signals by a semi-reflective mirror 406 .
  • a first light signal 408 and a reference light signal 410 are obtained.
  • the first light signal 408 is propagated through the medium 412 and a disordered light signal 414 is obtained at the output of the medium 412 .
  • the reference signal 410 is entered into a phase modulator 516 thanks to two reflective mirrors 418 and 420 .
  • the disordered signal 414 is propagated through the correcting device 100 from the input 102 to the output 104 and crosses all the optical elements 106 from the first optical element 106 1 to the last optical element 106 n .
  • the modulated reference signal 410 is propagated through the correcting device 100 from the output 104 to the input 102 and crosses all the optical elements 106 from the last optical element 106 n to the first optical element 106 1 .
  • the propagation of the disordered signal 414 and the modulated reference signal 410 causes an interference signal in the correcting device, for instance at each optical element 106 .
  • the system 400 comprises an optimization module 418 1 - 418 n for each optical element.
  • Each optimization module 418 i comprises a CCD camera 420 i measuring the amplitude of the interference signal for each pixel of the optical element 106 i and at least one actuator 422 i adapted to modify the phase profile of each pixel of the optical element 106 i .
  • the actuator 422 i realizes a stochastic modification of the phase delay applied by each pixel of the optical element 106 i .
  • the optimization is realised for every optical element 106 one after another. For example, the optimization is realised for the first optical element 106 1 , then the second optical element 106 2 and so on. When one optimization step is realised for each element, then a first optimization cycle is completed. A second optimization cycle is then realised and so on.
  • the optimization is stopped when a desired value of the interference visibility is reached, for example 0.95.
  • the order in which the optimization is realised on the optical elements 106 is not important.
  • FIG. 5 is a schematic representation of the means for measuring the amplitude of the interference signal for each pixel of an optical element.
  • the CCD camera 422 is adapted and configured to measure the intensity of the interference signal for each pixel 502 of the pixels 502 1 - 502 p of the optical element 106 i .
  • the intensity of the interference signal is measured in the same way for each pixel 502 j of the optical element 106 i .
  • the disordered signal 414 is reflected on a semi-reflective mirror 504 i associated to the optical element 106 i .
  • a part 414 1 of the disordered signal having crossed the pixel 502 j of the optical element 106 i is projected to the CCC camera 422 i .
  • a second part 414 2 continues to propagate to the optical element 106 i+1 .
  • the modulated reference signal 410 coming from the optical element 106 i+1 and going to cross the pixel 502 j of the optical element 106 i is reflected on the semi reflective mirror 504 i .
  • a part 410 1 of the modulated reference signal 410 is then reflected to a mirror 506 i which in turn reflects this part 410 1 of the modulated reference signal 410 to the CCD camera 422 i .
  • a second part 410 2 continues to propagate to the optical element 106 i , more particularly to the pixel 502 j of the optical element 106 i .
  • the intensity of the interference signal is measured by the CCD camera 522 for each pixel 502 of each optical element 106 .
  • FIG. 6 schematically represents the intensity of the interference signal measured for each pixel of an optical element, for example at the step 214 of the configuration method represented on FIG. 2 .
  • the oscillating curves 604 1 , 604 j and 604 p on the graph 602 of FIG. 6 schematically represent the intensity of the interference signal measured for the pixels 1 , j and p of an optical element 106 before calibration.
  • the oscillating intensity curves 604 are not synchronised and the total intensity, i.e. the sum of the intensity measured for each pixel, does not oscillate. It means that the value of the interference visibility parameter is 0.
  • the oscillating curves 604 1 , 604 j and 604 p on the graph 606 of FIG. 6 schematically represent the intensity of the interference signal measured for the pixels 1 , j and p of an optical element 106 after calibration.
  • the oscillating amplitude curves 604 are well synchronised and the total intensity, i.e. the sum of the intensity measured for each pixel is maximal.
  • the device is well configured and is able to correct the disordered signal and recover the initial signal.
  • the invention is particularly adapted to correct the effect of an optical fibre on a light signal.
  • the methods, the device and the systems according to the invention has been particularly shown and described for the correction of the effect of a medium on a light signal.
  • the methods, the device and the systems according to the invention may also be used to apply a given deformation to a light signal.
  • the medium is used to apply the given deformation and:

Abstract

A method and a system is provided for configuring a device for correcting the effect of a medium on a light signal having propagated through the medium, the device including at least one optical element whose phase profiles are individually adjustable. The configuring system and method include propagating a reference signal and a disordered signal obtained at the output of the medium through the correcting device. An interference parameter is measured and optimized by modifying the phase profile of each of the optical elements of the correcting device. A method and a system is also provided for correcting the effect of a medium on a light signal having propagated through the medium.

Description

FIELD OF THE INVENTION
The present invention relates to a method and a system for configuring a device for correcting the effect of a medium on a light signal having propagated through said medium. The invention also relates to a method, a device and a system for correcting said effect.
BACKGROUND OF THE INVENTION
A light signal propagating through a medium, more particularly an optical medium, an optical fibre for instance, undergoes a modification applied by said medium to the signal. The signal at the output of the medium is a disordered or blurred version of the light signal input to the medium. The modification applied by the medium must be corrected in order to recover the information conveyed by the light signal.
Nowadays, there is no method or system to efficiently and completely correct the effect of a medium on light signal having propagated through said medium.
Some researchers focus on a technique consisting of computing the complete transmission matrix of a medium and use it to correct the disordered signal in order to retrieve the information conveyed by the initial light signal. Such a technique is time consuming because it involves a series of measurements and needs an important computation power. Moreover the calculation involved may introduce errors.
The inventors of the present invention have mathematically proved that a device comprising several reflexion elements separated by a static propagation medium may be used to realise any spatial transformation on a light signal (Programmable Unitary Spatial Modes Manipulation, Jean-François Morizur, Lachlan Nicholls, Pu Jian, Seiji Armstrong, Nicolas Treps, Boris Hage, Magnus Hsu, Warwick Bowen, Jiri Janousek, Hans-A. Bachor).
OBJECTS OF THE INVENTION
It is an object of the present invention to overcome the aforementioned drawbacks.
Another object of the present invention is to provide a method and a system making it possible to efficiently correct the effect of a medium on a light signal having propagated through said medium.
Another object is furthermore to provide an industrially applicable method and a system making it possible to correct the effect of a medium on a light signal having propagated through said medium.
Another object is furthermore to provide a method and a system making it possible to correct the effect of a medium on a light signal having propagated through said medium in a faster and inexpensive fashion.
Yet another object of the invention is to provide a method and a system making possible a complete correction of the effect of a medium on a light signal having propagated through said medium.
SUMMARY OF THE INVENTION
The invention is disclosed as precised in the appended claims.
Such objects are accomplished through a method for configuring a device to correct the effect of a medium on a light signal having propagated through said medium, said device comprising at least one optical element whose spatial phase profile is individually adjustable, said method comprising several iterations of the following steps:
    • propagating a first light signal through said medium, said propagating step providing a so-called disordered signal,
    • propagating said disordered signal through said device,
    • propagating a second light signal, called reference signal, through said device, said reference signal being identical to said first signal,
    • optimizing the interference between said disordered signal and said reference signal, said optimizing step comprising at least one iteration of the following steps for at least one optical element:
      • measuring at least one interference parameter between said disordered signal and said reference signal, and
      • modifying the phase profile of at least one optical element depending on said interference parameter.
By “medium” it is meant a medium or a combination of media, each medium being a natural or artificial medium.
A single optical element, comprising independent sections whose phase profiles are individually adjustable, may be used to perform several successive reflexions or phase changes, in order to avoid the use of several such optical elements.
The method according to the invention makes it possible to configure a device to efficiently and completely correct the effect of a medium on a light signal having propagated through said medium.
The present invention provides a method that is simple to implement.
Indeed, the configuration of the correcting device is entirely based on the disordered signal propagated through the correcting device and doesn't comprise any computation of the transmission matrix of the medium. Thus, the errors that may be caused by such a computation operation are avoided and the method according to the invention is industrially applicable, less expensive and less time consuming than the prior art techniques.
The reference signal may be propagated through the device in the opposite direction to that of the disordered signal.
The step of measuring an interference parameter may comprise a step of measuring for each optical element:
    • an interference parameter for one or several zones of each optical element, and/or
    • an interference parameter for each pixel of each optical element, and/or
    • an interference parameter for the whole optical element.
In the present application, a pixel is defined as the smallest area of an optical element for which it is possible to modify the phase profile.
Thus, for each optical element, it is possible to focus on a part of the optical element corresponding to a pixel of its phase profile or a wider zone of the optical element. Such a feature decreases the configuration time of the correcting device.
The interference parameter may comprise a parameter relative to the phase difference between the disordered signal and the reference signal.
More particularly the interference parameter may comprise a parameter relative to the phase of the interference signal at each pixel or zone of the optical element.
In a particular embodiment of the method according to the invention the interference parameter may comprise, for an optical element, a parameter relative to the intensity of the interference signal, more particularly the light intensity, for each pixel or zone of the optical element, or the total light intensity, of the interference signal obtained by interference of the reference signal and the disordered signal. The total light intensity of the interference signal for an optical element corresponds to the sum of the intensities measured for all the zones or pixels of the optical element.
Indeed, the light intensity of the interference between the disordered signal and the reference signal may be used to measure the powers and the phase difference between these two signals.
In a particular embodiment of this feature, the method according to the invention may comprise a step to oscillate in time the overall phase of the reference signal and/or first signal.
Such a modulation makes the intensity of the interference between the disordered signal and the reference signal oscillate in time. For each zone of the optical element where the intensity of the interference is measured the local phase difference relative to the other zones between the reference signal and the disordered signal can be computed.
In a preferred embodiment the phase of the interference signal at each pixel or zone of the optical element with respect to a reference pixel or a predetermined phase reference is used to decide the necessary modification to the phase profile of this pixel or zone.
The step of modifying the spatial phase profile of an optical element may comprise modifying the phase delay applied by at least one zone and/or at least one pixel of said optical element to a light signal.
A feature of the method according to the invention is that the reference signal, the first signal or both the reference signal and the first signal may be modulated spatially before propagating through the medium and the correcting device.
In a particular embodiment of this feature, the method according to the invention may comprise a step to modulate the intensity profile of the reference signal and/or first signal.
The method according to the invention may also comprise a step to produce the reference signal and the first signal from two or more spatially separated incoherent light sources. Indeed this incoherence is equivalent to a spatial modulation of the overall source.
Such a spatial modulation makes it possible to configure the device, more particularly the spatial phase profile of each optical element, so that any effect of any complex medium on any light signal is corrected. Indeed, if the reference and first signals were not spatially modulated, then the spatial profile of the reference and first signals would remain static. The correcting device would then be configured according to only one spatial profile and would be able to correct the disordered signal only for one spatial profile.
The method according to the invention may also comprise a step for measuring a visibility parameter.
Indeed, an overall phase modulation applied to the reference signal or the disordered signal makes it possible to measure an interference visibility parameter between the reference signal and the disordered signal. Such an interference visibility parameter may be measured at a given position, for instance before, after or in the correcting device as the interference visibility parameter measured between two light signals remains identical whatever the measurement position.
In a preferred embodiment of the method according to the present invention, the reference signal is phase modulated before propagating through the correcting device. An interference parameter is measured for each pixel of each optical element. The measured interference parameter is the intensity of the interference signal.
As the reference signal is modulated, the intensity of the interference signal measured at each pixel of an optical element oscillates in time.
The phase difference between these oscillations and the reference oscillation measured at a pixel with high intensity is calculated.
By modifying the phase delay applied by each pixel of an optical element, the phase difference are reduced to 0 and all the oscillating interference signals measured for the optical element are synchronised. This synchronisation increases the visibility of the interference between the reference signal and the disordered signal.
The optimization step may be conducted individually for each optical element and one after each other whatever the order.
The method according to the invention may also comprise a step of generating the first signal and the reference signal from a unique light signal. The light signal may be divided into two light signals, one being the first signal and the other the reference signal.
The invention also relates to a device for correcting the effect of a medium on a light signal having propagated through said medium, comprising at least one optical element whose spatial phase profile is individually adjustable and configured according to the configuration method according to the invention.
In a particular embodiment of the device according to the invention, the two optical elements are separated by a combination of lenses and free space propagation.
In a particular embodiment of the device according to the invention, at least one optical element is a spatial light modulator or a deformable mirror.
The invention also relates to a method for correcting the effect of a medium on a light signal having propagated through said medium, said method implementing a device comprising at least one optical element whose phase profile is individually adjustable, said method comprising:
    • a configuration phase for configuring said device according to the configuration method according to the invention, and
    • a correcting phase correcting said signal with said calibrated device.
The correcting method according to the present invention may also comprise at least one adjusting step for adjusting the configuration of the device if changes occur in the medium during the correcting phase.
In a particular embodiment of the method according to the invention, a control light signal is sent regularly through the system to readjust the device, using the configuration method.
This control light signal can be different from the light signal used in the configuration phase.
In a particular embodiment of the method according to the invention, the control light signal is sent through the output of the device, and is reflected at the input of the complex medium. Thus, the control light goes through the correcting device, the medium, the medium again and finally the correcting device again. After the configuration phase, the device corrects the effect of the medium. Additional small changes occurring in the medium can be corrected using the calibration method with the control light.
The invention also relates to a system for configuring a device for correcting the effect of a medium on a light signal having propagated through said medium, said device comprising at least one optical element whose spatial phase profile is individually adjustable, said system comprising:
    • means for propagating a first light signal through said medium, said medium thus providing a so-called disordered signal,
    • means for propagating said disordered signal through said device,
    • means for propagating a second light signal, called reference signal, through said device, said reference signal being identical to said first signal,
    • means for measuring an interference parameter between said disordered signal and said reference signal, and
    • means for modifying the phase profile of at least one of said optical elements depending on said interference parameter.
The means for propagating the reference signal may be adapted to propagate the reference signal through the device in the opposite direction to that of the disordered signal
The system according to the invention may also comprise modulation means to introduce an overall phase modulation on the reference signal or the disordered signal before propagating said signal through the correcting device.
The system according to the invention may also comprise an element to modulate the spatial profile of the reference signal, the first signal or both these signals before they are sent in the medium or the correcting device.
The measuring means may comprise one CCD camera or one CCD camera for each optical element. Such a CCD camera may be configured for measuring an interference parameter for each pixel of the optical element.
The system according to the invention may also comprise reflexion means to transmit to the CCD camera a part of the interference signal obtained by interference of the disordered signal and the reference signal.
The means for modifying the phase profile of an optical element may comprise at least one actuator for each optical element, more particularly an actuator for each zone or pixel of each optical element. Such actuators may be integrated to the optical elements.
The invention also relates to a system for correcting the effect of a medium on a light signal having propagated through said medium, said system comprising:
    • a correcting device comprising at least one optical elements whose spatial phase profile is individually adjustable, and
    • a configuring system according to invention.
The invention also relates to a computer program comprising the instructions to implement the steps of a configuration method according to the present invention when said computer program is executed by a computer or computing means.
Such a computer program makes it possible to:
    • simulate, on a computer or computing means, the correction of an effect of a given medium on a light signal to determine the phase profile of at least one optical element of a given correcting device, and
    • configure said at least one optical element of said correcting device once the phase profile is determined by simulation.
Thus, for a given medium and a given correcting device, the phase profiles of each optical element of said correcting device may first be determined on a computer by simulation. When the correction if satisfactory, the phase profiles of each optical element is set and the device is then ready to use.
The methods, the device, the systems and the computer program according to the present invention may also be used to apply a given deformation to a light signal.
In this case, the given deformation is the deformation applied by the medium through which the first signal propagates. The disordered signal thus obtained at the output of the medium is used as reference signal in the methods, device, systems and computer program according to the present invention.
The second signal, identical to the first signal, is used as the signal to be modified by the methods, device, systems and computer program according to the invention so that said second signal is modified to be identical to the disordered signal.
To put it in another way, in this case, the reference signal and the second signal are switched.
BRIEF DESCRIPTION OF THE DRAWINGS
The new and inventive features believed characteristics of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative detailed embodiment when read in conjunction with the accompanying drawings, wherein:
FIG. 1 schematically represents an example of a correcting device;
FIG. 2 is a block diagram of an embodiment of the configuration method according to the invention;
FIG. 3 is a block diagram of an embodiment of the correction method according to the invention;
FIG. 4 schematically represents an embodiment of the correcting system according to the invention;
FIG. 5 schematically represents the means for measuring the amplitude of the interference signal for each pixel of an optical element;
FIG. 6 schematically represents the amplitude of the interference signal measured for each pixel of an optical element before and after configuration.
 PREFERRED EMBODIMENT OF THE INVENTION
In the following specifications, elements common to several figures are referenced through a common identifier.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically represents an example of a correcting device.
The correcting device 100 comprises at least one input 102 and at least one output 104.
Between the input 102 and the output 104, the correcting device 100 comprises several optical elements 106 1-106 n. Each optical element 106 has an adjustable spatial phase profile. For instance, each optical element 106 may be a spatial phase modulator (SLM) or a deformable mirror (DM). Each optical element 106 is separated from another optical element 106 by free space propagation and a lens (not represented), which perform an optical transform.
When configured, a disordered signal is input to the correcting device 100 and propagates across the optical elements 106 one after another. After the last optical element 106 n, the disordered signal is corrected and the correcting device provides the corrected version of the disordered signal.
In another embodiment of the correcting device, the several optical elements 106 1-106 n may be replaced by independent section of a single optical element, i.e. a spatial phase modulator or a deformable mirror.
FIG. 2 is a block diagram of an embodiment of the configuration method according to the invention.
The configuration method 200 comprises a first step 202 of generation of a light signal.
At a step 203 the spatial profile of the light signal is modulated using an accousto-optic modulator, a simple chopper or another mean to change the spatial profile of the light. The spatial modulation may be random.
At a step 204 the light signal is divided into two identical light signals called the first signal and the reference signal.
At a step 206 the first signal is propagated through a medium, and thus a disordered signal is obtained at the output of the medium.
At a step 208, the reference signal is phase modulated.
At step 210, the disordered signal and the reference signal are propagated through the correcting device, i.e. the optical elements, in opposite directions.
The propagation of the disordered signal and the modulated reference signal through each optical element generates an interference signal at each optical element, and more particularly at each pixel of each optical element.
At step 212 an optimization of the interference between the disordered signal and the modulated reference signal is performed.
The optimization step 212 comprises a step 214 measuring an interference parameter, i.e. the light intensity of the interference signal, for each pixel of an optical element of the correcting device. For each pixel, the measured intensity of the interference signal oscillates due to the phase modulation of the reference signal. Thus, for a given optical element there are as many oscillating signals as pixel.
The optimization step 212 also comprises a step 216 for modifying the spatial phase profile of the considered optical element in order to synchronise all the measured oscillating signals.
The synchronisation for an optical element may be performed as follows. A reference pixel is chosen among all the pixels of the optical element. For each pixel of the optical element:
    • the phase of the interference signal is measured,
    • a phase delay is determined by comparing the measured phase to the phase of the reference pixel,
    • the spatial phase applied by the pixel is modified in order to decrease/cancel said phase delay.
      Instead of choosing a reference pixel, a reference phase may be chosen and the phase delay for each pixel may be determined by comparing the phase of the interference signal of each pixel to the reference phase.
Steps 214 and 216 are realised for each optical element of the correcting device whatever the order. This condition is verified at step 218 that makes sure that steps 214 and 216 are realised for all optical elements of the correcting device.
When steps 214 and 216 are realised for all the optical elements of the correcting device, a second interference parameter, i.e. the interference visibility, is computed at step 220.
At step 222 the interference visibility value is tested.
If the value of the interference visibility is satisfactory than the configuration method is ended and the device is ready to use.
Instead of the visibility, other measurements can be used as termination parameters such as the contrast of the output image of the system, a local contrast of the output image, the fidelity to a desired intensity profile, the fidelity to a desired phase profile, the fidelity to a desired intensity and phase profile, the symmetry of the output image, the asymmetry of the output image, the phase differences measured at different points in the device, the intensity profiles measured at different points in the device.
In the contrary, i.e. if the value of the interference visibility is not satisfactory, for instance less than a predetermined threshold, then the optimization step 212 is repeated until a satisfactory value of the interference visibility is obtained.
FIG. 3 is a block diagram of an embodiment of the correction method according to the invention.
The correction method 300 represented en FIG. 3 comprises a configuration phase 302, configuring a correction device as the device 100 represented on FIG. 1 and realised according to the configuration method 200 represented en FIG. 2.
The correction method 300 also comprises a correcting phase 304, after the configuration phase 302.
The correcting phase comprises a step 306 for correcting a disordered signal with the configuration device.
The correcting phase also comprises a step 308 for adjusting the configuration of the device if changes occur on the medium during the correcting step. Then the correcting step 306 is stopped. The adjusting step 308 is realised. When the adjusting step 308 is finished the correcting step 308 is continued.
FIG. 4 schematically represents a correcting system 400 according to the invention.
The correcting system 400 represented on FIG. 4 comprises a source 402 providing a spatially modulated light signal 404. The light signal 404 is divided into two equal and identical light signals by a semi-reflective mirror 406. Thus, a first light signal 408 and a reference light signal 410 are obtained.
The first light signal 408 is propagated through the medium 412 and a disordered light signal 414 is obtained at the output of the medium 412.
The reference signal 410 is entered into a phase modulator 516 thanks to two reflective mirrors 418 and 420.
The disordered signal 414 is propagated through the correcting device 100 from the input 102 to the output 104 and crosses all the optical elements 106 from the first optical element 106 1 to the last optical element 106 n.
The modulated reference signal 410 is propagated through the correcting device 100 from the output 104 to the input 102 and crosses all the optical elements 106 from the last optical element 106 n to the first optical element 106 1.
The propagation of the disordered signal 414 and the modulated reference signal 410 causes an interference signal in the correcting device, for instance at each optical element 106.
The system 400 comprises an optimization module 418 1-418 n for each optical element.
Each optimization module 418 i comprises a CCD camera 420 i measuring the amplitude of the interference signal for each pixel of the optical element 106 i and at least one actuator 422 i adapted to modify the phase profile of each pixel of the optical element 106 i.
The actuator 422 i realizes a stochastic modification of the phase delay applied by each pixel of the optical element 106 i.
The optimization is realised for every optical element 106 one after another. For example, the optimization is realised for the first optical element 106 1, then the second optical element 106 2 and so on. When one optimization step is realised for each element, then a first optimization cycle is completed. A second optimization cycle is then realised and so on.
The optimization is stopped when a desired value of the interference visibility is reached, for example 0.95.
The order in which the optimization is realised on the optical elements 106 is not important.
FIG. 5 is a schematic representation of the means for measuring the amplitude of the interference signal for each pixel of an optical element.
Let's consider that all the optical elements 106 comprise the same number of pixels, for instance p pixels.
The CCD camera 422, is adapted and configured to measure the intensity of the interference signal for each pixel 502 of the pixels 502 1-502 p of the optical element 106 i.
The intensity of the interference signal is measured in the same way for each pixel 502 j of the optical element 106 i.
The disordered signal 414 is reflected on a semi-reflective mirror 504 i associated to the optical element 106 i. A part 414 1 of the disordered signal having crossed the pixel 502 j of the optical element 106 i is projected to the CCC camera 422 i. A second part 414 2 continues to propagate to the optical element 106 i+1.
The modulated reference signal 410 coming from the optical element 106 i+1 and going to cross the pixel 502 j of the optical element 106 i is reflected on the semi reflective mirror 504 i. A part 410 1 of the modulated reference signal 410 is then reflected to a mirror 506 i which in turn reflects this part 410 1 of the modulated reference signal 410 to the CCD camera 422 i. A second part 410 2 continues to propagate to the optical element 106 i, more particularly to the pixel 502 j of the optical element 106 i.
Thus the intensity of the interference signal is measured by the CCD camera 522 for each pixel 502 of each optical element 106.
FIG. 6 schematically represents the intensity of the interference signal measured for each pixel of an optical element, for example at the step 214 of the configuration method represented on FIG. 2.
The oscillating curves 604 1, 604 j and 604 p on the graph 602 of FIG. 6, schematically represent the intensity of the interference signal measured for the pixels 1, j and p of an optical element 106 before calibration.
Before calibration, the oscillating intensity curves 604 are not synchronised and the total intensity, i.e. the sum of the intensity measured for each pixel, does not oscillate. It means that the value of the interference visibility parameter is 0.
The oscillating curves 604 1, 604 j and 604 p on the graph 606 of FIG. 6, schematically represent the intensity of the interference signal measured for the pixels 1, j and p of an optical element 106 after calibration.
After calibration, the oscillating amplitude curves 604 are well synchronised and the total intensity, i.e. the sum of the intensity measured for each pixel is maximal.
The device is well configured and is able to correct the disordered signal and recover the initial signal.
The invention is particularly adapted to correct the effect of an optical fibre on a light signal.
Alternative Embodiments
In the given examples, the methods, the device and the systems according to the invention has been particularly shown and described for the correction of the effect of a medium on a light signal. However, the methods, the device and the systems according to the invention may also be used to apply a given deformation to a light signal.
In such a use, the medium is used to apply the given deformation and:
    • the method 200 and system 400 for configuring the correcting device 100 are identical, and the input 102 and the output 104 of the correcting device are switched when the device is in use, i.e. after the device has been configured, for example when the device is used in method 300; or
    • the device 100 is used as it is, and the reference signal 410 and the disordered signal 414 are switched in the methods 200 and 300 and in the system 400, i.e. the disordered signal 414 is used as the reference signal and the reference signal us used as the disordered signal.
While the invention has been particularly shown and described mainly with reference to a preferred embodiment, it will be understood that various changes in form and detail may be made therein without departing from the spirit, and scope of the invention.

Claims (34)

The invention claimed is:
1. A method for configuring a device to correct the effect of a medium on a light signal having propagated through said medium, said device comprising at least one optical element a plurality of optical elements whose spatial phase profile is individually adjustable, said method comprising the following steps:
propagating a first light signal through said medium, said propagating step providing a disordered signal;
propagating said disordered signal through said device the optical elements;
propagating a second light signal, called reference signal, through said device the optical elements in a propagation direction opposite to a propagation direction of the disordered signal, said reference signal being identical to said first signal to generate an interference signal between said disordered signal and said reference signal;
optimizing interference between said disordered signal and said reference signal, said optimizing step comprising the interference signal by repeating at least one iteration of the following steps for at least one optical element:
measuring at least one interference parameter between said disordered signal and said reference signal of the interference signal; and
modifying the phase profile of at least one optical element depending on said interference parameter.
2. The method according to claim 1 27, wherein the step of measuring an interference parameter comprises a step of measuring for each optical element:
an interference parameter for several zones of each optical element, and/or
an interference parameter for each pixel of each optical element, and/or
an interference parameter for the whole optical element.
3. The method according to claim 1, wherein the interference parameter comprises a parameter relative to the intensity of the interference signal obtained by interference of the reference signal and the disordered signal.
4. The method according to claim 1, wherein the step of modifying the spatial phase profile of an the at least one optical element comprises modifying the phase delay applied by at least one zone and/or at least one pixel of said optical element to a light signal.
5. The method according to claim 1, also comprising a step for phase modulating the reference signal before propagating it through the device the optical elements.
6. The method according to claim 5, also comprising a step for measuring an interference visibility parameter between the reference signal and the disordered signal.
7. The method according to claim 1 27, wherein the optimizing step is realised for each optical element of the correcting device one after another.
8. The method according to claim 1, also comprising a step of generating the first light signal and the reference signal from a unique light signal.
9. The method according to claim 8, comprising a step to modulate spatially the unique light signal.
10. A non-transitory computer-readable medium comprising: instructions to implement the steps of a method according to claim 1 that, when said computer program is instructions are executed by a computer or by computing means, cause the computer or computing means to correct the effect of a medium on a light signal having propagated through said medium by:
causing a source to propagate a first light signal through said medium, said propagating step providing a disordered signal;
causing said disordered signal to propagate through optical elements whose spatial phase profile is individually adjustable;
causing the source to propagate a second light signal, called reference signal, through the optical elements in a propagation direction opposite to a propagation direction of the disordered signal, said reference signal being identical to said first signal to generate an interference signal between said disordered signal and said reference signal;
causing at least one optimization module to optimize the interference signal by repeating at least one iteration of the following steps for at least one optical element;
measure at least one interference parameter of the interference signal; and
modify the phase profile of at least one optical element depending on said interference parameter.
11. A device for correcting the effect of a medium on a light signal having propagated through said medium, comprising at least one optical element whose spatial phase profile is individually adjustable and configured according to the method according to claim 1.
12. The device according to claim 11, wherein at least one optical element is a spatial light modulator or a deformable mirror.
13. A method for correcting the effect of a medium on a light signal having propagated through said medium, said method implementing a device comprising at least one optical element a plurality of optical elements whose phase profile is profiles are individually adjustable, said method comprising:
a configuration phase for configuring said device according to the method according to claim 1, and
a correcting phase correcting said signal with said calibrated device.
14. The method according to claim 13, also comprising at least one adjusting step for adjusting the configuration of the device if changes occur in the medium during the correcting phase.
15. A system for configuring a device for correcting the effect of a medium on a light signal having propagated through said medium, said device comprising at least one optical element whose spatial phase profile is individually adjustable, said system comprising:
means for propagating a first light signal through said medium, said medium thus providing a disordered signal;
means for propagating said disordered signal through said device;
means for propagating a second light signal, called reference signal, through said device, said reference signal being identical to said first signal;
means for measuring an interference parameter between said disordered signal and said reference signal at the level of each optical element; and
means for modifying the phase profile of at least one of said optical elements to increase said interference parameter.
16. The system according to claim 15, also comprising modulation means for modulating the reference signal before propagating said reference signal through the correcting device.
17. The system according to claim 15, wherein the measuring means comprise a CCD camera for each optical element.
18. The system according to claim 15, wherein the modifying means comprise at least one actuator for each optical element.
19. A system for correcting the effect of a medium on a light signal having propagated through said medium, said system comprising:
a correcting device comprising at least one optical element whose spatial phase profile is individually adjustable, and
a configuring system according to claim 15 to configure said device.
20. A method for configuring a device to apply a given deformation to a light signal, said device comprising at least one optical element a plurality of optical elements whose spatial phase profile is profiles are individually adjustable, said method comprising the following steps:
propagating a first light signal through a medium, said propagating step providing a reference signal;
propagating said reference signal through said device the optical elements;
propagating a signal to deform second light signal through said device optical elements in a propagation direction opposite to a propagation direction of the reference signal, said signal to deform second light signal being identical to said first reference signal;
using the reference signal to apply the given deformation to the second light signal and generating an interference signal between said second light signal and said reference signal;
optimizing interference between said reference signal and said signal to deform, said optimizing step comprising said interference signal by repeating at least one iteration of the following steps for at least one optical element:
measuring at least one interference parameter between said reference signal and said signal to deform of said interference signal; and
modifying the phase profile of at least one optical element depending on said interference parameter.
21. A system for configuring a device to apply a given deformation to a light signal, said device comprising at least one optical element whose spatial phase profile is individually adjustable, said system comprising:
means for propagating a first light signal through a medium, said medium thus providing a reference signal;
means for propagating said reference signal through said device;
means for propagating a signal to deform through said device, said signal to deform being identical to said first signal;
means for measuring an interference parameter between said reference signal and said signal to deform at the level of each optical element; and
means for modifying the phase profile of at least one of said optical elements to increase said interference parameter.
22. A non-transitory computer-readable medium comprising: instructions to implement the steps of a method for configuring a device to correct the effect of a medium on a light signal having propagated through said medium that, when said computer program is instructions are executed by a computer or by computing means, said device comprising at least one optical element whose spatial phase profile is individually adjustable, said method comprising the following steps cause the computer or computing means to apply a given deformation to a light signal by:
propagating a first light signal through said a medium, said propagating step providing a reference signal;
propagating saidcausing the reference signal to propagate through said deviceoptical elements whose spatial phase profiles are individually adjustable utilizing a source;
propagatingcausing a signal to deformsecond light signal to propagate through said deviceoptical elements in a propagation direction opposite to a propagation direction of the reference signal utilizing the source, said signal to deformsecond light signal being identical to said firstreference signal;
using the reference signal to apply the given deformation to the second light signal and generating an interference signal between said second light signal and said reference signal;
optimizingcausing at least one optimization module to optimize said interference between said reference signal and said signal to deform, said optimizing step comprisingsignal by repeating at least one iteration of the following steps for at least one optical element:
measuring at least one interference parameter between said reference signal and said signal to deform of said interference signal; and
modifying the phase profile of at least one optical element depending on said interference parameter.
23. A device for applying a given deformation to a light signal, comprising at least one optical element whose spatial phase profile is individually adjustable and configured according to the following method:
propagating a first light signal through a medium, said propagating step providing a reference signal;
propagating said reference signal through said device;
propagating a signal to deform through said device, said signal to deform being identical to said first signal;
optimizing interference between said reference signal and said signal to deform, said optimizing step comprising at least one iteration of the following steps for at least one optical element:
measuring at least one interference parameter between said reference signal and said signal to deform: and
modifying the phase profile of at least one optical element depending on said interference parameter.
24. A method for applying a given deformation to a light signal, said method implementing a device comprising at least one optical element whose phase profile is individually adjustable, said method comprising:
a configuration phase for configuring said device, and
a deformation phase deforming said signal with said calibrated device;
said configuration phase comprising:
propagating a first light signal through a medium, said propagating step providing a reference signal:
propagating said reference signal through said device;
propagating a signal to deform through said device, said signal to deform being identical to said first signal;
optimizing interference between said reference signal and said signal to deform, said optimizing step comprising at least one iteration of the following steps for at least one optical element:
measuring at least one interference parameter between said reference signal and said signal to deform: and
modifying the phase profile of at least one optical element depending on said interference parameter.
25. A system for applying a given deformation to a light signal, said system comprising:
a deformation device comprising at least one optical element whose spatial phase profile is individually adjustable; and
a configuring system to configure said device, said configuring system comprising:
means for propagating a first light signal through a medium, said medium thus providing a reference signal;
means for propagating said reference signal through said device;
means for propagating a signal to deform through said device, said signal to deform being identical to said first signal;
means for measuring an interference parameter between said reference signal and said signal to deform at the level of each optical element; and
means for modifying the phase profile of at least one of said optical elements to increase said interference parameter.
26. The method of claim 1, wherein each optical element is separated from another optical element by free space propagation and a lens.
27. A method for configuring a device to correct the effect of a medium on a light signal having propagated through said medium, said device comprising a plurality of optical elements whose spatial phase profile is individually adjustable, said method comprising the following steps:
propagating a first light signal through said medium, said propagating step providing a disordered signal;
propagating said disordered signal through the optical elements;
propagating a second light signal, called reference signal, through the optical elements, said reference signal being identical to said first signal to generate an interference signal between said disordered signal and said reference signal, wherein said reference signal is propagated through each optical element in a propagation direction opposite to the propagation direction of the disordered signal; and
optimizing the interference signal by repeating at least one iteration of the following steps for at least one optical element:
measuring at least one interference parameter of the interference signal; and
modifying the phase profile of at least one optical element depending on said interference parameter.
28. A method for configuring a device to correct an effect of a medium on a light signal having propagated through the medium, the device comprising a plurality of optical elements whose spatial phase is individually adjustable, the method comprising:
propagating a disordered signal and a reference signal through the optical elements in opposite directions to generate an interference signal between the disordered signal and the reference signal, the disordered signal comprising a first light signal having propagated through the medium, the reference signal comprising a second light signal identical to the first light signal;
optimizing the interference signal by performing at least one iteration of the following steps for at least one optical element:
measuring at least one interference parameter of the interference signal; and
modifying the phase profile of the at least one optical element depending on the interference parameter.
29. A method for configuring a device to apply a given deformation to a light signal, said device comprising a plurality of optical elements whose spatial phase profiles are individually adjustable, said method comprising the following steps:
propagating a first light signal through a medium, said propagating step providing a reference signal;
propagating the reference signal through the optical elements;
propagating a second light signal through said optical elements, said second light signal being identical to said reference signal, wherein said reference signal is propagated through each optical element in a propagation direction opposite to the propagation direction of the second light signal;
using the reference signal to apply the given deformation to the second light signal and generating an interference signal between said second light signal and said reference signal;
optimizing said interference signal by repeating at least one iteration of the following steps for at least one optical element:
measuring at least one interference parameter of said interference signal; and
modifying the phase profile of at least one optical element depending on said interference parameter.
30. The method according to claim 20, wherein the step of modifying the phase profile of the at least one optical element comprises modifying the phase delay applied by at least one zone and/or at least one pixel of said optical element to a light signal.
31. The method according to claim 20, further comprising a step for phase modulating the reference signal before propagating it through the optical elements.
32. The method according to claim 20, further comprising a step of generating the reference signal and the second light signal from a unique light signal.
33. The method according to claim 32, further comprising a step to modulate spatially the unique light signal.
34. The method of claim 20, wherein each optical element is separated from another optical element by free space propagation and a lens.
US15/854,566 2010-12-21 2011-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect Active 2032-02-25 USRE48338E1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US15/854,566 USRE48338E1 (en) 2010-12-21 2011-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
EP10196310A EP2469221A1 (en) 2010-12-21 2010-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect.
EP10196310 2010-12-21
PCT/EP2011/073535 WO2012085046A1 (en) 2010-12-21 2011-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect
US13/993,805 US9250454B2 (en) 2010-12-21 2011-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect
US15/854,566 USRE48338E1 (en) 2010-12-21 2011-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect

Publications (1)

Publication Number Publication Date
USRE48338E1 true USRE48338E1 (en) 2020-12-01

Family

ID=44065284

Family Applications (2)

Application Number Title Priority Date Filing Date
US15/854,566 Active 2032-02-25 USRE48338E1 (en) 2010-12-21 2011-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect
US13/993,805 Ceased US9250454B2 (en) 2010-12-21 2011-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect

Family Applications After (1)

Application Number Title Priority Date Filing Date
US13/993,805 Ceased US9250454B2 (en) 2010-12-21 2011-12-21 Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect

Country Status (8)

Country Link
US (2) USRE48338E1 (en)
EP (2) EP2469221A1 (en)
JP (1) JP5990544B2 (en)
CN (1) CN103299154B (en)
AU (1) AU2011347385C1 (en)
BR (1) BR112013015061A2 (en)
CA (1) CA2821106C (en)
WO (1) WO2012085046A1 (en)

Families Citing this family (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3016973B1 (en) 2014-01-30 2017-08-11 Cailabs DEVICE FOR PROCESSING LIGHT / OPTICAL RADIATION, METHOD AND SYSTEM FOR DESIGNING SUCH A DEVICE
FR3025957B1 (en) 2014-09-11 2016-12-23 Cailabs CHROMATIC DISPERSION COMPENSATION DEVICE AND METHOD
US10073221B2 (en) * 2015-09-30 2018-09-11 Nokia Of America Corporation Beamforming for an optical switch
FR3049135B1 (en) 2016-03-15 2020-02-14 Cailabs MULTIMODE FIBER OPTIC COMMUNICATIONS DEVICE WITH MODAL DISPERSION COMPENSATION COMPONENT
FR3049134B1 (en) 2016-03-15 2018-07-13 Cailabs DEVICE FOR MULTIMODE FIBER OPTIC COMMUNICATIONS WITH INTERVERSION OF PROPAGATION MODES
JP7083821B2 (en) * 2016-06-17 2022-06-13 ソルボンヌ・ユニヴェルシテ Equipment and related methods for illuminating objects with controlled light intensity
FR3061964A1 (en) 2017-01-19 2018-07-20 Cailabs TRANSFORMING THE VARIATION OF A PARAMETER OF A BEAM INTO THE VARIATION OF ANOTHER OF ITS PARAMETERS
FR3076358B1 (en) 2017-12-28 2019-12-20 Cailabs OPTICAL DEVICE HAVING MEANS FOR ITS PRECISE ASSEMBLY, METHOD FOR ASSEMBLING OR TESTING THE DEVICE
FR3076357B1 (en) 2017-12-29 2021-10-22 Cailabs MULTI PASSAGE CAVITY OF AN OPTICAL SPATIAL MANIPULATION DEVICE OF LUMINOUS RADIATION.
FR3078412B1 (en) 2018-02-26 2022-01-14 Cailabs METHOD FOR DESIGNING A MULTIPLANE CONVERSION DEVICE, PHASE PLATE OBTAINED THROUGH THIS METHOD, AND MULTIPLANE CONVERSION DEVICE
FR3084478A3 (en) * 2018-07-25 2020-01-31 Cailabs MODAL FILTERING DEVICE COMPRISING A MULTIPLAN LIGHT CONVERSION DEVICE
WO2020021196A1 (en) * 2018-07-25 2020-01-30 Cailabs Device for processing light radiation, comprising a multi-plane light conversion device
FR3092404B1 (en) 2019-02-04 2021-10-22 Cailabs OPTICAL DEVICE FOR COMBINING A PLURALITY OF BEAMS, AND SYSTEM USING SUCH A DEVICE
FR3097334A1 (en) 2019-06-17 2020-12-18 Cailabs FIXING PROCESS OF A SINGLE-MODE OPTICAL FIBER AND OF A MULTI-MODE OPTICAL FIBER, OPTICAL COUPLING EQUIPMENT AND OPTICAL FIBER THAT CAN BE OBTAINED THANKS TO SUCH A PROCESS
FR3097659B1 (en) 2019-06-21 2024-04-19 Cailabs Light source comprising at least one semiconductor chip carrying at least one diode
FR3104271B1 (en) 2019-12-04 2021-12-17 Alpao ADAPTIVE OPTICAL SYSTEM WITH IMPROVED RESPONSE TIME, RELATED USE AND PROCESS
FR3106668B1 (en) 2020-01-29 2022-01-21 Cailabs DEVICE FOR PROCESSING A LIGHT BEAM THROUGH A MULTI-PLANE CONVERTER TO CONFORM IT TO A PREDETERMINED SHAPE
FR3120450B1 (en) 2021-03-04 2023-11-24 Cailabs System for compensating the distortion of a wavefront of incident light radiation
WO2022246695A1 (en) * 2021-05-26 2022-12-01 The University Of Hong Kong Improving classical and quantum free-space communication by adaptive optics and by separating the reference and signal beams
FR3128798A1 (en) 2021-10-28 2023-05-05 Cailabs Device for processing at least two single-mode light beams
FR3129002A1 (en) 2021-11-05 2023-05-12 Safran Electrical & Power Connection device by transmission channel reassignment to an on-board multiplexed passive fiber communication network for an aircraft
FR3129221A1 (en) 2021-11-15 2023-05-19 Safran Electrical & Power Hybrid optical multiplexer, associated hybrid optical demultiplexer and associated on-board optical communication network
FR3137189A1 (en) 2022-06-27 2023-12-29 Cailabs MULTI-PASS CAVITY OF AN OPTICAL DEVICE FOR SPATIAL MANIPULATION OF LIGHT RADIATION

Citations (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4291224A (en) 1978-11-30 1981-09-22 Nippon Kogaku K.K. Light image space frequency component extracting device
US4384762A (en) 1980-02-18 1983-05-24 Canon Kabushiki Kaisha Focusing screen device
US5090795A (en) 1987-10-22 1992-02-25 Hughes Aircraft Company Integrated adaptive optics apparatus
EP0562424A1 (en) 1992-03-25 1993-09-29 Texas Instruments Incorporated Embedded optical calibration system
JPH06250108A (en) 1993-02-22 1994-09-09 Hitachi Ltd Compensation optical device and astronomical telescope, optical data link, and laser working machine using same
JPH08189806A (en) 1995-01-11 1996-07-23 Fuji Xerox Co Ltd Interference measuring method and interferometer
US5717516A (en) * 1996-03-01 1998-02-10 Hughes Electronics Hybrid laser power combining and beam cleanup system using nonlinear and adaptive optical wavefront compensation
EP0980123A2 (en) * 1998-08-11 2000-02-16 TRW Inc. High average power fiber laser system with phase front control
US6200309B1 (en) * 1997-02-13 2001-03-13 Mcdonnell Douglas Corporation Photodynamic therapy system and method using a phased array raman laser amplifier
US6275250B1 (en) * 1998-05-26 2001-08-14 Sdl, Inc. Fiber gain medium marking system pumped or seeded by a modulated laser diode source and method of energy control
JP2002040368A (en) 2000-07-27 2002-02-06 National Institute Of Advanced Industrial & Technology Optically driven type wave front correction video method and device
US6430328B1 (en) 2000-10-13 2002-08-06 William H. Culver Optical switch
US20020122254A1 (en) * 2000-12-22 2002-09-05 Jesper Gluckstad Method and an apparatus for generating a phase-modulated wave front of electromagnetic radiation
US6519385B1 (en) * 2000-09-27 2003-02-11 The Boeing Company Method and apparatus for controllably positioning an optical fiber to introduce a phase shift
WO2003036368A1 (en) 2001-10-25 2003-05-01 Hamamatsu Photonics K.K. Phase modulation apparatus and phase modulation method
US6597836B2 (en) * 2001-06-20 2003-07-22 The Boeing Company Optical phased array control system
JP2004045326A (en) 2002-07-15 2004-02-12 Konica Minolta Holdings Inc Interferometer
US20040125380A1 (en) 2002-12-26 2004-07-01 Hrl Laboratories, Llc Adaptive optical system with self-referencing contrast control
US7194155B1 (en) 2004-08-10 2007-03-20 The Board Of Trustees Of The Leland Stanford Junior University Adaptive control for mitigating interference in a multimode transmission medium
CN101189532A (en) 2005-06-06 2008-05-28 株式会社拓普康 Distance measuring device
CN101271575A (en) 2008-04-09 2008-09-24 东华大学 Orthogonal projection emendation method for image measurement in industry close range photography
US20090046372A1 (en) 2005-04-08 2009-02-19 Jonathan Maram Wavefront correction system
US20090201575A1 (en) 2008-02-07 2009-08-13 Imra America, Inc. High power parallel fiber arrays
JP2009216454A (en) 2008-03-07 2009-09-24 Canon Inc Wavefront aberration measuring apparatus, wavefront aberration measuring method, exposure apparatus, and device manufacturing method
JP4350186B2 (en) 1999-01-06 2009-10-21 オリンパス株式会社 Focusing device

Patent Citations (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4291224A (en) 1978-11-30 1981-09-22 Nippon Kogaku K.K. Light image space frequency component extracting device
US4384762A (en) 1980-02-18 1983-05-24 Canon Kabushiki Kaisha Focusing screen device
US5090795A (en) 1987-10-22 1992-02-25 Hughes Aircraft Company Integrated adaptive optics apparatus
EP0562424A1 (en) 1992-03-25 1993-09-29 Texas Instruments Incorporated Embedded optical calibration system
JPH06250108A (en) 1993-02-22 1994-09-09 Hitachi Ltd Compensation optical device and astronomical telescope, optical data link, and laser working machine using same
JPH08189806A (en) 1995-01-11 1996-07-23 Fuji Xerox Co Ltd Interference measuring method and interferometer
US5717516A (en) * 1996-03-01 1998-02-10 Hughes Electronics Hybrid laser power combining and beam cleanup system using nonlinear and adaptive optical wavefront compensation
US6200309B1 (en) * 1997-02-13 2001-03-13 Mcdonnell Douglas Corporation Photodynamic therapy system and method using a phased array raman laser amplifier
US6275250B1 (en) * 1998-05-26 2001-08-14 Sdl, Inc. Fiber gain medium marking system pumped or seeded by a modulated laser diode source and method of energy control
EP0980123A2 (en) * 1998-08-11 2000-02-16 TRW Inc. High average power fiber laser system with phase front control
JP4350186B2 (en) 1999-01-06 2009-10-21 オリンパス株式会社 Focusing device
JP2002040368A (en) 2000-07-27 2002-02-06 National Institute Of Advanced Industrial & Technology Optically driven type wave front correction video method and device
US6519385B1 (en) * 2000-09-27 2003-02-11 The Boeing Company Method and apparatus for controllably positioning an optical fiber to introduce a phase shift
US6430328B1 (en) 2000-10-13 2002-08-06 William H. Culver Optical switch
US20020122254A1 (en) * 2000-12-22 2002-09-05 Jesper Gluckstad Method and an apparatus for generating a phase-modulated wave front of electromagnetic radiation
US6597836B2 (en) * 2001-06-20 2003-07-22 The Boeing Company Optical phased array control system
WO2003036368A1 (en) 2001-10-25 2003-05-01 Hamamatsu Photonics K.K. Phase modulation apparatus and phase modulation method
JP2004045326A (en) 2002-07-15 2004-02-12 Konica Minolta Holdings Inc Interferometer
US20040125380A1 (en) 2002-12-26 2004-07-01 Hrl Laboratories, Llc Adaptive optical system with self-referencing contrast control
US7194155B1 (en) 2004-08-10 2007-03-20 The Board Of Trustees Of The Leland Stanford Junior University Adaptive control for mitigating interference in a multimode transmission medium
US20090046372A1 (en) 2005-04-08 2009-02-19 Jonathan Maram Wavefront correction system
CN101189532A (en) 2005-06-06 2008-05-28 株式会社拓普康 Distance measuring device
US20090201575A1 (en) 2008-02-07 2009-08-13 Imra America, Inc. High power parallel fiber arrays
JP2011512653A (en) 2008-02-07 2011-04-21 イムラ アメリカ インコーポレイテッド High power parallel fiber array
JP2009216454A (en) 2008-03-07 2009-09-24 Canon Inc Wavefront aberration measuring apparatus, wavefront aberration measuring method, exposure apparatus, and device manufacturing method
CN101271575A (en) 2008-04-09 2008-09-24 东华大学 Orthogonal projection emendation method for image measurement in industry close range photography

Non-Patent Citations (23)

* Cited by examiner, † Cited by third party
Title
Australian Examination Report for Australian Application No. 2011347385 dated Aug. 22, 2014, 3 pages.
Borevich et al., Subgroups of the Unitary Group that Contain the Group of Diagonal Matrices, translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematichskogo Instituta im. V.A. Stekova AN SSR, vol. 86, (1979), pp. 19-29.
Chinese First Office Action for Chinese Application No. 201180061009.8 dated Mar. 4, 2015, 14 pages.
Chinese Search Report for Chinese Application No. 201180061009, dated Feb. 12, 2015, 2 pages.
Chinese Second Office Action for Chinese Application No. 201180061009.8 dated Sep. 22, 2015, 6 pages.
European Office Action for European Application No. 11813827 dated Nov. 17, 2017, 7 pages.
European Search Report for European Application No. 10196310 dated Jun. 14, 2011, 7 pages.
Hsu et al, Optical Pattern Recognition via Adaptive Spatial Homodyne Detection, J. Opt. Soc. Am. A, vol. 27, No. 12 (Dec. 2010), pp. 2583-2587.
International Search Report for International Application No. PCT/EP2011/073535 dated Mar. 21, 2012, 4 pages.
International Written Opinion for International Application No. PCT/EP2011/073535 dated Mar. 21, 2012, 5 pages.
Japanese Decision to Grant for Japanese Application No. 2013-554802, dated Aug. 9, 2016, 5 pages with English Translation.
Japanese Notification of Reasons for Refusal for Japanese Application No. 2013-554802 dated Nov. 30, 2015, 3 pages.
Japanese Search Report for Japanese Application No. 2013-554802, dated Oct. 20, 2015, 26 pages with English Translation.
J-F. Morizur, Lachlan Nicholls, Pu Jian, Seiji Armstrong, Nicolas Treps, et al.. Programmable unitary spatial modes manipulation. 2010. <hal-00483672>.
Mansell et al., "A Low-Cost Compact Metric Adaptvie Optics System," Society of Photo-Optical Instrumentation Engineers, vol. 6711-20, 2007, 11 pages.
Morizur et al, Spatial Reshaping of A Squeezed State of Light, Eur. Phys. J. D., vol. 61, (2011), pp. 237-239.
Morizur, J.F. et. al, "Programmable Unitary Spatial Mode Manipulation", Journal of Optical Society of America, vol. 27, No. 11, Nov. 2010, pp. 2524-2531, Optical Society of America.
Panicker et al., "Algorithms for Compensation of Multimode Fiber Dispersion Using Adaptive Optics," Journal of Lightwave Technology, vol. 27, No. 24, Dec. 15, 2009, pp. 5790-5799.
Popoff, S.M. et al, "Measuring the Transmission Matrix in Optics: An Approach to the Study and Control of Light Propagation in Disordered Media", Physical Review Letters, No. 104, Mar. 12, 2010, pp. 1-4, The American Physical Society.
Sakamaki et al., "New Optical Waveguide Design Based on Wavefront Matching Method," Journal of Lightwave Technology, vol. 25, No. 11, Nov. 2007, pp. 3511-3518.
Shen et al., "Compensation for Multimode Fiber Dispersion by Adaptive Optics," Optics Letters, vol. 30, No. 22, Nov. 15, 2005, pp. 2985-2987.
Vellekoop et al., "Exploiting disorder for perfect focusing", Nature Photonics vol. 4, (Feb. 14, 2010), pp. 320-322.
Vellekoop, LM et al, "Exploiting Disorder for Perfect Focusing", Nature Photonics, vol. 4, May 2010, pp. 320-322, Macmillian Publishers Limited.

Also Published As

Publication number Publication date
US20140118811A1 (en) 2014-05-01
BR112013015061A2 (en) 2016-08-09
CN103299154A (en) 2013-09-11
EP2656003B1 (en) 2019-02-13
CA2821106C (en) 2019-06-18
EP2469221A1 (en) 2012-06-27
EP2656003A1 (en) 2013-10-30
AU2011347385C1 (en) 2015-10-01
JP5990544B2 (en) 2016-09-14
AU2011347385A1 (en) 2013-07-25
CA2821106A1 (en) 2012-06-28
US9250454B2 (en) 2016-02-02
CN103299154B (en) 2016-03-02
AU2011347385B2 (en) 2015-03-26
WO2012085046A1 (en) 2012-06-28
JP2015509203A (en) 2015-03-26

Similar Documents

Publication Publication Date Title
USRE48338E1 (en) Method and system for configuring a device for correcting the effect of a medium on a light signal, method, device and system for correcting said effect
JP6561072B2 (en) Apparatus for processing light / optical radiation and methods and systems for designing the apparatus
JP5945341B1 (en) Spatial phase modulator
JP7001835B2 (en) Systems and methods for compensating nonlinear response characteristics with phase shift deflection measurements
WO2020007274A1 (en) Light beam scanning control method and device, system and corresponding medium
US8019233B2 (en) Method and apparatus for using a hologram to control the optical field distribution of light generated by a light source and launched into an end of an optical waveguide
Yang et al. Theoretical proof of parameter optimization for sinusoidal fringe projection profilometry
Huang et al. Fast, closed-loop iterative system-on-chip of deflection efficiency enhancement for a liquid crystal optical phased array
CN104898270A (en) DMD optical system light source position positioning auxiliary device and light source position adjusting method
CN105204168B (en) It is a kind of based on double wave front calibrator without wave front detector far-field laser beam apparatus for shaping and method
CA2875867A1 (en) Improving stability of an optical source in an optical network test instrument
Segel et al. Modal vs. zonal wavefront-sensorless adaptive optics for free-space laser communications
JP5563518B2 (en) Variable dispersion compensator phase optimization method, phase optimized variable dispersion compensator, and phase optimization apparatus
Li et al. All-purpose automatic image stacking for sparse aperture telescopes using dynamic metric stochastic parallel gradient descent algorithm
JPWO2020065841A1 (en) Optical scanning device, imaging device, adjusting device for optical scanning device, and adjusting method for optical scanning device
US20220414313A1 (en) Length compensating waveguide for an optical circuit
CN112985306B (en) Anti-diffraction mixed self-adaptive compensation interference detection method and device and computer equipment
US20220244527A1 (en) Micro-electro-mechanical scanning mirror control method, control apparatus, and system
Ke Adaptive-Optics Correction Technology
KR20240001618A (en) Adaptive optics
JP2020506411A (en) A method for fast simulation of optical systems.
CN115698833A (en) Signal processing device, signal processing method, program, and lighting device
Kim et al. Processing System Design for Implementing a Linear Quadratic Gaussian (LQG) Controller to Optimize the Real-Time Correction of High Wind-Blown Turbulence
KR20230133512A (en) System and method for depth of field expansion
KR101541420B1 (en) The wavefront correction apparatus for the adaptive optics using an anamorphic lens

Legal Events

Date Code Title Description
FEPP Fee payment procedure

Free format text: ENTITY STATUS SET TO UNDISCOUNTED (ORIGINAL EVENT CODE: BIG.); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY

FEPP Fee payment procedure

Free format text: ENTITY STATUS SET TO SMALL (ORIGINAL EVENT CODE: SMAL); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY

MAFP Maintenance fee payment

Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YR, SMALL ENTITY (ORIGINAL EVENT CODE: M2552); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY

Year of fee payment: 8