KR102437442B1 - Wireless Optical Communication Receiving Apparatus And Method For Narrow FoV and Mitigating Solar Noise - Google Patents

Abstract

The present invention detects one of a first lens that focuses incident light, a beam splitter that splits the light incident through the first lens at a predetermined ratio, and the branched light to determine the position and determine the maximum light intensity Through the image sensor unit for outputting a feedback control signal according to the selected position, a spatial light filter that filters so that the rest of the branched light is incident, and the incident light is transmitted to an area corresponding to the feedback control signal, and the spatial light filter It is possible to provide a wireless optical communication receiving apparatus and method capable of accurately detecting a wireless optical signal by mitigating solar noise with a narrow viewing angle, including a light detecting unit that detects transmitted light and converts it into an electrical signal.

Description

TECHNICAL FIELD [0001] Wireless Optical Communication Receiving Apparatus And Method For Narrow FoV and Mitigating Solar Noise

The present invention relates to a wireless optical communication receiving apparatus and method, and to a wireless optical communication receiving apparatus and method for reducing a viewing angle and alleviating background optical noise.

Since free space optical communication (FSO) transmits an optical signal through the air without a transmission path composed of optical fibers, there is no restriction on transmission speed and transmission capacity, and there are no restrictions on frequency use. In addition, since data is transmitted through space as a medium, compared to wired optical communication, the cost and installation time required for optical fiber construction are dramatically reduced, and thus an effective communication network can be constructed.

Wireless optical communication is a method of transmitting an optical signal using a laser, and is mainly used outdoors and can easily perform communication over a long distance of several kilometers. However, deterioration of transmission performance may occur due to the influence of sunlight, and deterioration of signal-to-noise ratio (SNR) performance of several to tens of dB may occur depending on the type of sunlight noise. The most effective way to mitigate such noise is to use a receiver with a narrow field of view (FoV) of several tens to hundreds of urad. However, since beam wandering or scintillation due to the atmosphere or a change in the position of the optical receiver must be considered, FoV of several to several hundred mrad level is currently applied. Therefore, a technique capable of mitigating solar noise with a narrow viewing angle is required.

Korean Patent No. 10-1997532 (registered on July 2, 2019)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wireless optical communication receiving apparatus and method capable of mitigating solar noise with a narrow viewing angle.

Another object of the present invention is to provide a wireless optical communication receiving apparatus and method capable of accurately detecting a wireless optical signal by focusing and dividing incident light using a lens to detect a location where the divided light is focused and filtering the remaining area. is doing

A wireless optical communication receiving apparatus according to an embodiment of the present invention for achieving the above object includes: a first lens for focusing incident light; a beam splitter that splits the light incident through the first lens at a predetermined ratio; an image sensor unit that detects one of the branched lights to determine a position of a maximum light intensity, and outputs a feedback control signal according to the determined position; a spatial light filter that filters the remaining of the branched light to be incident and the light incident to the region corresponding to the feedback control signal is transmitted; and a light detection unit that detects the light transmitted through the spatial light filter and converts it into an electrical signal.

The spatial light filter may transmit light incident to an area having a predetermined size based on a position designated by the feedback control signal.

The spatial light filter may be implemented as either a deformable mirror device (DMD) or a spatial light modulator (SLM).

The image sensor unit may be configured such that an area for sensing light corresponds to an area where the spatial light filter filters incident light.

The wireless optical communication receiver may further include a second lens disposed between the spatial light filter and the light detection unit to focus the light filtered by the spatial light filter and transmit it to the light detection unit.

The wireless optical communication receiving apparatus may further include an opening formed in the shape of a hole protruding to the outside or opened to the inside in order to block a direct light component among background light noise in the incident light.

The wireless optical communication receiver may further include an attenuation filter disposed between the beam splitter and the image sensor unit to attenuate light incident to the image sensor unit so that light saturation does not occur in the image sensor unit.

The wireless optical communication receiving apparatus may further include a signal processing unit to obtain a transmitted signal by demodulating the electrical signal obtained by the optical detection unit in a predetermined demodulation method.

A wireless optical communication reception method according to another embodiment of the present invention for achieving the above object includes focusing the incident light using a lens; branching the light incident through the lens at a predetermined ratio; determining a position of a maximum light intensity by detecting one of the branched lights, and outputting a feedback control signal according to the determined position; filtering the light incident to the region designated by the feedback control signal from the rest of the branched light to be transmitted; and detecting the filtered light and converting it into an electrical signal.

Therefore, the wireless optical communication receiving apparatus and method according to an embodiment of the present invention focuses the incident light using a lens, divides the focused light by a beam splitter, detects a location where the divided light is focused, and receives an optical signal. By limiting the area to be used, it is possible to accurately detect a radio optical signal. Therefore, it is possible to mitigate solar noise with a narrow viewing angle, thereby suppressing deterioration of transmission performance.

1 is a diagram schematically illustrating a process in which an optical signal is transmitted and detected in a wireless optical communication system according to an embodiment of the present invention.
FIG. 2 shows a change in an optical signal in the wireless optical communication system of FIG. 1 .
FIG. 3 is a diagram for explaining the structure of the wireless optical communication receiver of FIG. 1 .
4 illustrates an example in which the spatial light modulator of FIG. 3 spatially filters received light.
5 shows a wireless optical communication reception method according to an embodiment of the present invention.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings. However, the present invention may be embodied in several different forms, and is not limited to the described embodiments. In addition, in order to clearly explain the present invention, parts irrelevant to the description are omitted, and the same reference numerals in the drawings indicate the same members.

Throughout the specification, when a part "includes" a certain component, it does not exclude other components unless otherwise stated, meaning that other components may be further included. In addition, terms such as "... unit", "... group", "module", and "block" described in the specification mean a unit that processes at least one function or operation, which is hardware, software, or hardware. and a combination of software.

1 is a diagram schematically illustrating a process in which an optical signal is transmitted and detected in a wireless optical communication system according to an embodiment of the present invention, FIG. 2 shows a change in an optical signal in the wireless optical communication system of FIG. 1, and FIG. 3 is It is a diagram for explaining the structure of the wireless optical communication receiver of FIG. 1 . 4 shows an example in which the spatial light modulator of FIG. 3 spatially filters received light.

Referring to FIG. 1 , in a wireless optical communication system, a light generating module 200 of an optical transmitting device generates an optical signal and radiates it to the optical receiving device 100 . Here, the light generating module 200 may be implemented as a laser diode (LD), etc., using an Intensity Modulation/Direct Detection (IM/DD) based On-Off Keying (OOK) modulation technique, etc. An optical signal can be modulated and transmitted.

Meanwhile, the light receiving apparatus 100 according to the present embodiment detects and receives an optical signal from light emitted from the light transmitting apparatus and incident through the FSO channel.

In FIG. 2, (a) shows the optical transmission signal emitted from the optical transmission device, (b) shows the optical signal absorbed and scattered by the FSO channel while passing through the FSO channel, (c) shows the inside of the optical receiving device Indicates an incident light reception signal.

As shown in (a) of FIG. 2 , the light generating module 200 generates and radiates light having excellent straightness, such as a laser. However, since the emitted light is transmitted over a long distance of several km to several tens of Km in the FSO channel using the atmosphere as a medium, it can be attenuated by absorbing and scattering light by the FSO channel as shown in (b) in the transmission process, as well as being attenuated by the sun. Background light noise, such as light, can lower the signal-to-noise ratio (SNR).

In addition, the wireless optical communication system is also used between base stations in fixed locations, but is mainly used for communication with unmanned aerial vehicles (UAVs). It is difficult to pinpoint the exact location of the In this case, since the position of the transmitted optical signal is not precisely fixed, as shown in (c), the position with the strongest intensity in the received light is deviated from the center, making it difficult for the optical receiving device to accurately detect the optical signal.

Accordingly, the optical reception apparatus 100 according to the present embodiment determines the position of the transmitted optical signal first, and detects the optical signal according to the determined position, thereby greatly improving the reception accuracy of the optical signal.

Referring to FIG. 3 , in this embodiment, the light receiving apparatus 100 includes an opening 110 , a first lens 120 , a beam splitter 130 , an image sensor unit 140 , a spatial light filter 150 , and a second It may include two lenses 160 , a light detection unit 170 , and a signal processing unit 180 .

The opening 110 may be formed in a shape to protrude to the outside of the light receiving device 100 as shown in FIG. 3 as a configuration to block a direct light component of background light noise, but is formed in a hole shape open to the inside. it might be In FIG. 3 , as an example, the opening 110 is shown to be formed in a cylindrical shape, but the opening 110 may be formed in various shapes to prevent the direct light component of the background light noise from being incident into the light receiving device 100 . .

When the opening 110 is formed in the light receiving apparatus 100 as described above, the direct light component of the background light noise is easily blocked. However, the background light noise of the scattered light component is not blocked and may be incident on the light receiving device 100 together with the optical signal transmitted from the light transmitting device.

The light incident through the opening 110 first passes through the first lens 120 , and the light passing through the first lens 120 is focused in the spatial light filter 150 . At this time, a beam splitter 130 is disposed between the first lens 120 and the spatial light filter 150 , and the beam splitter 130 transmits light incident through the lens 120 at a predetermined ratio. , so that the divided light is incident on the image sensor unit 140 and the spatial light filter 150, respectively. In this case, the split ratio may be set so that a relatively high ratio of light is transmitted to the spatial light filter 150 and a low ratio of light is transmitted to the image sensor unit 140 . For example, the beam splitter 130 may divide the light incident to the spatial light filter 150 to a ratio of the light incident to the image sensor unit 140 to 100:1.

This is because, in the present embodiment, the image sensor unit 140 is simply used to determine the exact position of the light incident through the first lens 120 . The image sensor unit 140 includes an image sensor and detects light that is divided and incident by the beam splitter 130, and a feedback control signal fc for controlling the spatial light filter 150 according to the position where the light is sensed. create and output

A region to which light is incident in the image sensor unit 140 may be configured to correspond to a region to which light is incident in the spatial light filter 150 , and the position of the region to which light is most strongly incident is tracked. Then, the feedback control signal fc indicating the tracked position is output to the spatial light filter 150 .

Here, the image sensor unit 140 includes an image sensor having a high frame rate, detects light incident at high speed, determines the position of the light detected with the strongest intensity, and generates a feedback control signal fc. can be printed out. This is because the spatial light filter 150 can accurately filter the incident light only when the image sensor unit 140 detects the intensity of light for each area at high speed.

Meanwhile, in the light receiving apparatus 100 according to the present embodiment, an attenuation filter 141 may be further included between the beam splitter 130 and the image sensor unit 140 . Although the light with reduced intensity is incident on the image sensor unit 140 by dividing the light according to a predetermined ratio by the beam splitter 130 , the intensity of the divided light nevertheless causes a light saturation phenomenon in the image sensor unit 140 . can occur And when the light saturation phenomenon occurs, the image sensor unit 140 may not be able to narrowly limit the position where the light intensity is strongest, so that it may not be able to output the normal feedback control signal fc. Also, the light saturation phenomenon may cause damage to the image sensor unit 140 . Accordingly, in the light receiving apparatus 100 of the present embodiment, an attenuation filter 141 is additionally provided between the beam splitter 130 and the image sensor unit 140 , and the beam splitter 130 enters the image sensor unit 140 . By attenuating the light intensity, it is possible to prevent light saturation from occurring in the image sensor unit 140 . Here, the attenuation filter 141 may be implemented as, for example, a neutral density (ND) filter.

The spatial light filter 150 filters so that only the area designated by the feedback control signal fc is transmitted in the light divided by the beam splitter 130 in response to the feedback control signal fc, and the remaining area is blocked. . When the feedback control signal fc is applied, the spatial light filter 150 allows incident light to be transmitted only in an area of a predetermined size around a position designated by the applied feedback control signal fc, and in the remaining area. It can be filtered to block the light. Referring to the example of FIG. 4 , in the spatial light filter 150 , only light incident to the inner region of the circle indicated in red is transmitted centered on the position designated by the feedback control signal fc, and the light incident to the remaining regions is You can filter it to be blocked.

As described above, since the area in which the image sensor unit 140 detects light and the filtering area of the spatial light filter 150 are configured to correspond to each other, the image sensor unit 140 selects the area in which the light is detected with the strongest intensity. When the feedback control signal fc is designated and transmitted, the spatial light filter 150 transmits light in the region where the light is incident with the strongest intensity, while easily blocking the light incident on the remaining region.

Here, the spatial light filter 150 may be implemented as, for example, a deformable mirror device (DMD) or a spatial light modulator (SLM).

Light filtered by the spatial light filter 150 is incident on the light detector 170 through the second lens 160 . The second lens 160 re-focuses the light incident through the spatial light filter 150 and transmits it to the light detection unit 170 , so that the light detection unit 170 detects the incident light more efficiently.

The photodetector 170 detects an optical signal incident through the second lens 160 , converts it into an electrical signal, and transmits the converted electrical signal to the signal processor 180 . The photodetector 170 may be implemented as, for example, a photodiode.

The signal processing unit 180 demodulates a signal to be transmitted from the transmitting device in a predetermined manner with respect to the electrical signal applied from the optical detection unit 170 . In general, in wireless optical communication, OOK (On-Off Keying) modulation method based on binary signal with implementation simplicity, low price, and high reliability is mainly used, but PPM (Pulse Position Modulation) or PAM (Pulse Amplitude Modulation) method may be used, and the signal processing unit 180 may demodulate the electrical signal according to a demodulation method corresponding to the modulation method applied by the transmitting apparatus (not shown).

In some cases, the signal processing unit 180 receives an image signal from the image sensor unit 140 , analyzes a position where the light intensity is strongest from the applied image signal, and transmits the feedback control signal fc to the spatial light filter 150 . It can be configured to output.

In the present embodiment, the light receiving device 100 focuses the light incident through the opening 110 using the first lens 120 and an image sensor unit ( 140) is used to detect a focused position in the spatial light filter 150 that has passed through the first lens so that only light in an area corresponding to the detected position can pass through the spatial light filter 150, It ensures the FoV and makes it possible to obtain a high signal-to-noise ratio.

5 shows a wireless optical communication reception method according to an embodiment of the present invention.

When the wireless optical communication reception method of FIG. 5 is described with reference to FIGS. 1 to 4 , first, when light is incident through the opening 110 , it is transmitted through the first lens 120 and the incident light is filtered through a spatial light filter. It is focused to (150) (S10). Then, the focused light is split at a predetermined ratio by using the light splitter 130 positioned on the path focused by the spatial light filter 150 ( S20 ). When the light is split by the light splitter 130, one of the split lights is sensed using an image sensor (S30). Here, the area in which light is sensed is configured to correspond to an area in which the spatial light filter 150 can filter light. Then, a position where the detected light intensity is strongest is determined (S40). When the position with the strongest light intensity is determined, a feedback control signal fc designating the determined position is generated and output to the spatial light filter 150 (S50).

The remainder of the light split by the light splitter 130 is incident on the spatial light filter 150 , and among the incident light, it is incident on a region of a predetermined size based on a position specified by the applied feedback control signal fc. Filters so that only light is transmitted and the rest is blocked (S60). Then, the light that is filtered by the spatial light filter 150 and is incident through the second lens 160 is detected by the light detector 170 and converted into an electrical signal (S70).

Accordingly, the signal processing unit 180 demodulates the electrical signal transmitted from the photodetector 170 in a predetermined manner to obtain a signal transmitted from the transmission device (S80).

The method according to the present invention may be implemented as a computer program stored in a medium for execution by a computer. Here, the computer-readable medium may be any available medium that can be accessed by a computer, and may include all computer storage media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, and read dedicated memory), RAM (Random Access Memory), CD (Compact Disk)-ROM, DVD (Digital Video Disk)-ROM, magnetic tape, floppy disk, optical data storage, and the like.

Although the present invention has been described with reference to the embodiment shown in the drawings, which is only exemplary, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

Accordingly, the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims.

100: light receiving device 110: opening
120: first lens 130: beam splitter
140: image sensor unit 141: attenuation filter
150: spatial light filter 160: second lens
170: light detection unit 180: signal processing unit

Claims (16)

a first lens for focusing the incident light;
a beam splitter that splits the light incident through the first lens at a predetermined ratio;
an image sensor unit that detects the intensity of one area of the branched light, determines a position having the maximum light intensity, and outputs a feedback control signal according to the determined position;
a spatial light filter that filters the remaining of the branched light to be incident and the light incident to the region corresponding to the feedback control signal is transmitted; and
A light detection unit for detecting the light transmitted through the spatial light filter and converting it into an electrical signal,
The image sensor unit
a region for sensing light is set to correspond to a region where the spatial light filter filters incident light;
The image sensor unit tracks the position of the region where light is most strongly incident, and the feedback control signal is output based on the tracked position.
The method of claim 1, wherein the spatial light filter is
A wireless optical communication receiving device that transmits light incident to an area of a predetermined size based on a position specified by the feedback control signal. The method of claim 2, wherein the spatial light filter is
A wireless optical communication receiver implemented as either a Deformable Mirror Device (DMD) or a Spatial Light Modulator (SLM). delete According to claim 1, wherein the wireless optical communication receiving device
and a second lens disposed between the spatial light filter and the light detection unit to focus the light filtered by the spatial light filter and transmit the light to the light detection unit. According to claim 1, wherein the wireless optical communication receiving device
The wireless optical communication receiver further comprising an opening protruding to the outside or formed in the shape of a hole opened inwardly to block a direct light component of background light noise from incident light. According to claim 1, wherein the wireless optical communication receiving device
The wireless optical communication receiver further comprising an attenuation filter disposed between the beam splitter and the image sensor unit to attenuate light incident to the image sensor unit so that light saturation does not occur in the image sensor unit. According to claim 1, wherein the wireless optical communication receiving device
The wireless optical communication receiver further comprising a signal processing unit to obtain a transmitted signal by demodulating the electrical signal obtained by the optical detection unit in a predetermined demodulation method. focusing the incident light using a lens;
branching the light incident through the lens at a predetermined ratio;
detecting the intensity of one area of the branched light using an image sensor, determining a position having the maximum light intensity, and outputting a feedback control signal according to the determined position;
filtering the light incident to the region designated by the feedback control signal from the rest of the branched light to be transmitted; and
Detecting the filtered light and converting it into an electrical signal,
The image sensor is set such that a region for detecting light corresponds to a region for filtering the remaining incident light among the lights branched in the filtering step,
The image sensor tracks a position of an area where light is most strongly incident, and the feedback control signal is output based on the tracked position. The method of claim 9, wherein the filtering comprises:
A wireless optical communication reception method for transmitting light incident on an area of a predetermined size with respect to a location specified by the feedback control signal. The method of claim 10, wherein the filtering comprises:
A wireless optical communication reception method performed using either a Deformable Mirror Device (DMD) or a Spatial Light Modulator (SLM). delete 10. The method of claim 9, wherein the wireless optical communication receiving method
Prior to outputting the feedback control signal, the method further comprising attenuating light incident on the image sensor so that light saturation does not occur in the image sensor. 10. The method of claim 9, wherein the wireless optical communication receiving method
The method further comprising the step of re-focusing the filtered light in the filtering step to be more easily detected in the step of converting into an electrical signal by using a lens. 10. The method of claim 9, wherein the wireless optical communication receiving method
The wireless optical communication receiving method further comprising the step of blocking the direct light component of the background light noise through an opening formed in the shape of a hole protruding to the outside or opened inward before the step of focusing the light to be incident. 10. The method of claim 9, wherein the wireless optical communication receiving method
After the converting into the electrical signal, the method further comprising: obtaining a transmitted signal by demodulating the obtained electrical signal in a predetermined demodulation method.

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