JP2006340280A

JP2006340280A - Optical axis alignment initializing apparatus of optical spatial communication system

Info

Publication number: JP2006340280A
Application number: JP2005165461A
Authority: JP
Inventors: Koichi Yoshida; 耕一吉田; Takeshi Tsujimura; 健辻村
Original assignee: Nippon Telegraph and Telephone Corp
Current assignee: Nippon Telegraph and Telephone Corp
Priority date: 2005-06-06
Filing date: 2005-06-06
Publication date: 2006-12-14

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical axis alignment initializing apparatus of an optical spatial communication system which efficiently realizes alignment initialization for coarsely adjusting an optical axis between a mobile terminal and a fixed station, and efficiently establishes an optical link. <P>SOLUTION: A transmitter 11 is provided with a movable reflection mirror 12 for reflecting a laser beam by an LD (laser diode). A receiver 13 is provided with a movable reflection mirror 14 for guiding a laser beam to beam splitters 15, 16, a PSD (position sensing device) for detecting the irradiation positions of the laser beams split by the beam splitters 15, 16, and a PD (photodiode) for receiving the split beams from the beam splitters 15, 16. A beam incident angle sensor 19 is provided on the receiver 13, and a searching area where the PSD can capture the laser beam via the movable reflection mirror 14 is moved along an incident beam captured by the beam incident angle sensor 19, thereby guiding the laser beam from the transmitter 11 to the PSD in the receiver 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、空間中にレーザー光を伝播させて通信を行う光空間通信システムにおいて、移動を伴う端末が固定局との光のリンクを確立し光軸の自動調整を行いながら光通信を行う前の光軸の粗調整を行うアライメント初期化を効率的に実現できる光空間通信システムの光軸アライメント初期化装置に関するものである。 The present invention relates to an optical space communication system that performs communication by propagating laser light in a space before a mobile terminal establishes an optical link with a fixed station and performs optical communication while automatically adjusting an optical axis. The present invention relates to an optical axis alignment initialization apparatus for an optical space communication system capable of efficiently realizing alignment initialization for performing rough adjustment of the optical axis.

従来、例えばビル−ビル間光空間通信のような通常の光空間通信では２つの送受信機を固定的に対向配置し風や振動などによる微小な軸ズレの影響を補正するメカニズムが採用されている。一方、端末の移動を伴う光空間通信では広範囲な相対位置変化に伴う軸ズレに対応する光軸調整機構が不可欠となる（例えば、非特許文献１参照。）。この場合、移動端末の任意の初期状態において固定局との光のリンクを確立し光軸調整モードに入るためには光軸を粗調整するアライメントの初期化が必要となる。拡散光やビーム径を拡大した場合に比べビーム径を絞った場合の光空間通信は秘匿性や耐クロストーク特性に優れるがアライメントの初期化は容易ではなく、試行錯誤に頼ったり長時間の調整パラメータの探索が必要になるといった問題が生じてくる。 Conventionally, in a normal optical space communication such as a building-to-building optical space communication, a mechanism has been adopted in which two transmitters / receivers are fixedly arranged opposite to each other to correct the influence of a slight axis shift due to wind or vibration. . On the other hand, in optical space communication involving movement of a terminal, an optical axis adjustment mechanism that corresponds to an axial shift accompanying a wide range of relative position changes is indispensable (see, for example, Non-Patent Document 1). In this case, in order to establish an optical link with a fixed station and enter an optical axis adjustment mode in an arbitrary initial state of the mobile terminal, it is necessary to initialize alignment for coarse adjustment of the optical axis. Optical space communication when the beam diameter is narrowed compared to the case of expanding the diffused light and beam diameter is excellent in secrecy and crosstalk resistance, but the initialization of the alignment is not easy, relying on trial and error or long-time adjustment There arises a problem that it is necessary to search for parameters.

Koichi Yoshida,Tatsuro Yano,and Takeshi Tsujimura:“Automatic Optical Axis Alignment for Active Free Space Optics”,SICE Annual Conference in Sapporo,August4-6,2004,Hokkaido Institute of Tecnology,Japan,p.2035-2040Koichi Yoshida, Tatsuro Yano, and Takeshi Tsujimura: “Automatic Optical Axis Alignment for Active Free Space Optics”, SICE Annual Conference in Sapporo, August 4-6, 2004, Hokkaido Institute of Tecnology, Japan, p.2035-2040

本発明の目的は、上記従来技術の課題を克服し、通信可能な任意の初期状態にある移動端末と固定局との間の光軸の粗調整を行うアライメント初期化を効率的に実現し、光のリンクを効率よく確立することを可能にする光空間通信システムの光軸アライメント初期化装置を提供することにある。 The object of the present invention is to overcome the above-mentioned problems of the prior art and efficiently realize alignment initialization for performing coarse adjustment of the optical axis between a mobile terminal and a fixed station in an arbitrary initial state in which communication is possible. It is an object of the present invention to provide an optical axis alignment initialization apparatus for an optical space communication system that makes it possible to establish an optical link efficiently.

上記目的を達成するために本発明の光空間通信システムの光軸アライメント初期化装置は、送信装置に、送信用レーザー光源によるレーザー光の発射方向（パン・チルト角）が調整可能なように２自由度の送信用可動式反射鏡を備え、受信装置に、送信装置から到達したレーザー光の向きを調整し直列に配置された２つのビームスプリッターへ導く２自由度の受信用可動式反射鏡と、最初のビームスプリッターにより２分した一方の分岐光を次のビームスプリッターによりさらに２分したレーザー光それぞれの照射位置を検知する２つのＰＳＤ（ＰｏｓｉｔｉｏｎＳｅｎｓｉｎｇＤｅｖｉｃｅ）と、最初のビームスプリッターによるもう１つの分岐光を受光する受信用ＰＤ（ＰｈｏｔｏＤｅｔｅｃｔｏｒ）とを備え、空間中にレーザー光を伝播させて通信を行う光空間通信システムにおいて、受信装置にビーム入射角検出器を設置し、前記ビーム入射角検出器と前記受信用可動式反射鏡の両方をカバーするように送信装置からのレーザー光を前記送信用可動式反射鏡により高速スキャンさせたときに、前記２つのＰＳＤが前記受信用可動式反射鏡を介してレーザー光を捕らえることの可能な探索領域を前記ビーム入射角検出器が捕らえた入射光線に沿って移動させることにより送信装置からのレーザー光を受信装置のＰＳＤに導くことを特徴とするものである。 In order to achieve the above object, the optical axis alignment initialization apparatus of the optical space communication system of the present invention is configured so that the transmission direction of the laser beam by the laser beam source for transmission (pan / tilt angle) can be adjusted. A movable reflector for transmission with a degree of freedom, and a movable reflector for reception with two degrees of freedom that guides the receiving device to two beam splitters arranged in series by adjusting the direction of the laser beam that has arrived from the transmitter. Two PSDs (Position Sensing Device) for detecting the irradiation position of each of the laser beams divided into two by the next beam splitter and one split light divided by the first beam splitter, and another by the first beam splitter It is equipped with a PD (Photo Detector) for receiving the branched light and laser light in the space. In an optical space communication system in which communication is performed by propagation, a laser beam from a transmitting device is installed so that a beam incident angle detector is installed in a receiving device and covers both the beam incident angle detector and the movable reflector for reception. When the light is scanned at a high speed by the movable reflector for transmission, the beam incident angle detector forms a search region where the two PSDs can capture laser light via the movable reflector for reception. The laser beam from the transmitting device is guided to the PSD of the receiving device by moving along the captured incident light beam.

本発明の光空間通信システムの光軸アライメント初期化装置によれば、移動を伴う光空間通信システムにおいて任意の初期位置にある移動端末と固定局との光のリンクを確立して光空間通信を開始するための光軸の粗調整を行うアライメント初期化を効率的に実現できるという効果がある。 According to the optical axis alignment initialization apparatus for an optical space communication system of the present invention, an optical link between a mobile terminal at an arbitrary initial position and a fixed station is established in an optical space communication system involving movement to perform optical space communication. There is an effect that the alignment initialization for performing the coarse adjustment of the optical axis for starting can be efficiently realized.

以下図面を参照して本発明の実施の形態例を詳細に説明する。
図１は本発明の実施形態例に係る光空間通信システムの光軸アライメント初期化装置を示す構成説明図である。送信装置１１にはレーザー光Ｌを発射する送信用レーザー光源例えばレーザーダイオードＬＤが設けられ、前記レーザーダイオードＬＤから発射されたレーザー光Ｌの光路にはレーザー光Ｌの発射方向（パン・チルト角）が調整可能なように２自由度の送信用可動式反射鏡である２自由度可動式反射鏡１２が設けられる。一方、受信装置１３には送信装置１１から到達したレーザー光Ｌの向きを調整する２自由度の受信用可動式反射鏡である２自由度可動式反射鏡１４が設けられ、前記２自由度可動式反射鏡１４で反射されたレーザー光Ｌの光路には直列に配置された２つのビームスプリッター１５，１６が設けられる。前記２つのビームスプリッター１５，１６にはそれぞれ対応してプリズム斜面１７，１８が設けられる。前記２自由度可動式反射鏡１４で反射されたレーザー光Ｌを最初のビームスプリッター１５により２分した一方の分岐光を次のビームスプリッター１６によりさらに２分したレーザー光Ｌそれぞれの照射位置にはレーザー光Ｌそれぞれの照射位置を検知する２つのＰＳＤ１，ＰＳＤ２が設けられる。前記２自由度可動式反射鏡１４で反射されたレーザー光Ｌを最初のビームスプリッター１５により２分したもう１つの分岐光を受光する位置には受信用ＰＤが設けられる。受信装置には送信装置１１から到達したレーザー光Ｌのビーム入射角を検出するビーム入射角センサ１９が設置される。前記ビーム入射角センサ１９は、ビーム入射角センサ１９と２自由度可動式反射鏡１４の両方をカバーするように送信装置１１からのレーザー光Ｌを２自由度可動式反射鏡１２により高速スキャンさせたときに、２つのＰＳＤ１，ＰＳＤ２が２自由度可動式反射鏡１４を介してレーザー光Ｌを捕らえることの可能な探索領域をビーム入射角センサ１９が捕らえた入射光線に沿って移動させることにより送信装置１１からのレーザー光Ｌを受信装置１３のＰＳＤ１，ＰＳＤ２に導くものである。 Embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 is an explanatory diagram showing a configuration of an optical axis alignment initialization apparatus for an optical space communication system according to an embodiment of the present invention. The transmission device 11 is provided with a transmission laser light source for emitting a laser beam L, for example, a laser diode LD, and in the optical path of the laser beam L emitted from the laser diode LD, the emission direction (pan / tilt angle) of the laser beam L Is provided with a two-degree-of-freedom movable reflector 12 that is a two-degree-of-freedom movable reflector for transmission. On the other hand, the receiving device 13 is provided with a two-degree-of-freedom movable reflecting mirror 14 that is a two-degree-of-freedom movable reflecting mirror for adjusting the direction of the laser beam L that has arrived from the transmitting device 11, and is movable with two degrees of freedom. Two beam splitters 15 and 16 arranged in series are provided in the optical path of the laser beam L reflected by the reflective mirror 14. The two beam splitters 15 and 16 are provided with prism inclined surfaces 17 and 18, respectively. The laser beam L reflected by the two-degree-of-freedom movable mirror 14 is divided into two by the first beam splitter 15 and one split beam is further divided by the next beam splitter 16 at each irradiation position of the laser beam L. Two PSD1 and PSD2 for detecting the irradiation position of each laser beam L are provided. A receiving PD is provided at a position for receiving another branched light obtained by dividing the laser light L reflected by the two-degree-of-freedom movable mirror 14 by the first beam splitter 15. A beam incident angle sensor 19 that detects the beam incident angle of the laser light L that has arrived from the transmitting device 11 is installed in the receiving device. The beam incident angle sensor 19 scans the laser beam L from the transmitter 11 at a high speed with the two-degree-of-freedom movable reflector 12 so as to cover both the beam incident-angle sensor 19 and the two-degree-of-freedom movable reflector 14. When two PSDs 1 and 2 move the search area where the laser beam L can be captured via the movable mirror 14 having two degrees of freedom along the incident light beam captured by the beam incident angle sensor 19. The laser beam L from the transmitter 11 is guided to PSD1 and PSD2 of the receiver 13.

すなわち、送信装置１１では送信用ＬＤから発射されるレーザー光Ｌを２自由度可動式反射鏡１２で反射させ受信装置１３側へ送出する。受信装置１３では到達光を２自由度可動式反射鏡１４で反射させて２つのビームスプリッター１５，１６へ導いている。最初のビームスプリッター１５で２分された光の一方を受信用ＰＤで受光し、もう一方はさらに２分されビームスポット検出用の２つのＰＳＤ１，ＰＳＤ２に到達する。また、送信装置１１と受信装置１３間はそれぞれ対応して設けられた制御部２０，２１を用いて通常の電波無線や赤外線などによる無線ＬＡＮにより互いの情報を交換できるようになっている。 That is, the transmission device 11 reflects the laser light L emitted from the transmission LD with the two-degree-of-freedom movable reflecting mirror 12 and transmits it to the reception device 13 side. In the receiving device 13, the reaching light is reflected by the movable mirror 14 with two degrees of freedom and guided to the two beam splitters 15 and 16. One of the lights divided by the first beam splitter 15 is received by the receiving PD, and the other is further divided by two to reach the two PSD1 and PSD2 for beam spot detection. In addition, the transmitting device 11 and the receiving device 13 can exchange information with each other by a wireless LAN such as a normal radio wave or infrared rays using the control units 20 and 21 provided correspondingly.

非特許文献１で示されているように受信装置１３への入射光とＰＤ光学系の間の関係はプリズム斜面１８に対するＰＳＤ２の鏡像をＰＳＤ２′とするとＰＳＤ１とＰＳＤ２′上のレーザービームスポットの位置によってパラメトライズされる。光軸調整はＰＤ光学系の光軸に対応して定義される２つのＰＳＤ１，ＰＳＤ２上の基準点からのズレを２自由度可動式反射鏡１４へフィードバックすることにより行われるが、通信可能な任意の相対位置にある送信装置１１と受信装置１３間で光のリンクを確立するには先ず送信装置１１からのレーザー光Ｌを受信装置１３のＰＳＤ１，ＰＳＤ２が受光可能な探索範囲へと導く必要がある。 As shown in Non-Patent Document 1, the relationship between the incident light to the receiver 13 and the PD optical system is that the position of the laser beam spot on PSD1 and PSD2 ′ is PSD2 ′ when the mirror image of PSD2 with respect to the prism inclined surface 18 is PSD2 ′. Is parametrized. The optical axis adjustment is performed by feeding back to the two-degree-of-freedom movable reflecting mirror 14 the deviation from the reference point on the two PSD1 and PSD2 defined corresponding to the optical axis of the PD optical system. In order to establish an optical link between the transmission device 11 and the reception device 13 at an arbitrary relative position, it is first necessary to guide the laser light L from the transmission device 11 to a search range where the PSD 1 and PSD 2 of the reception device 13 can receive light. There is.

図２は本発明の実施形態例に係る受信装置がレーザー光を捕らえることのできる探索範囲を示す説明図である。すなわち、受信装置１３の２つのＰＳＤ１，ＰＳＤ２が２自由度可動式反射鏡１４を介して受光できるレーザー入射光の範囲を示しており、図２のＡは２つのビームスプリッター１５，１６のプリズム斜面１７，１８が直線に見える方向から見た図、図２のＢは図２のＡと直交する矢印方向からＰＳＤ２′を見た場合の様子を示す図である。図２のＢ中の楕円が２自由度可動式反射鏡１４を示し、図２のＢ中の円がＰＳＤ１，ＰＳＤ２の受光範囲（レーザー光ビームスポットの検出範囲）を示すとき、ＰＳＤ１，ＰＳＤ２の探索範囲は２自由度可動式反射鏡１４の楕円を窓とみなしてＰＳＤ１，ＰＳＤ２検出範囲の円が捕らえることのできる光線の集合として定義され、図２のＡ中の斜線部分で表されている。 FIG. 2 is an explanatory diagram showing a search range in which the receiver according to the embodiment of the present invention can capture laser light. 2 shows the range of laser incident light that can be received by the two PSDs 1 and 2 of the receiving device 13 via the two-degree-of-freedom movable mirror 14. FIG. 2A shows the prism slopes of the two beam splitters 15 and 16. 17 and 18 are views seen from a direction in which a straight line is seen, and FIG. 2B is a view showing a state when PSD 2 'is seen from the direction of an arrow orthogonal to A in FIG. When the ellipse in B of FIG. 2 indicates the two-degree-of-freedom movable reflector 14, and the circle in B of FIG. 2 indicates the light receiving range of PSD1 and PSD2 (detection range of the laser beam spot), PSD1 and PSD2 The search range is defined as a set of rays in which the circle of the detection range of PSD1 and PSD2 can be captured by regarding the ellipse of the movable mirror 14 with two degrees of freedom as a window, and is represented by the hatched portion in A of FIG. .

前記光軸アライメントの初期化は次のような手順で実行できる。
［１］送信装置１１から発射されるレーザー光Ｌを受信装置１３の２自由度可動式反射鏡１４とビーム入射角センサ１９を同時に包含できるような適当なパン・チルト角の範囲内でラスタスキャンさせる。送信装置１１を直接人手で操作できないときは送信装置１１側にカメラ等を設置し無線ＬＡＮを介して遠隔操縦する。
［２］受信装置１３のビーム入射角センサ１９で捕らえた角度情報からレーザー光発射点候補の集合としての直線を受信装置１３の基準座標系において定義する。
［３］ＰＳＤ１，ＰＳＤ２の探索範囲の中心線が前記［２］の直線上を通過するように２自由度可動式反射鏡１４を調整し、その交点をＰＳＤ１，ＰＳＤ２によってレーザー光Ｌが検出されるまで移動させる。 The optical axis alignment can be initialized by the following procedure.
[1] Raster scan of the laser beam L emitted from the transmitter 11 within an appropriate pan / tilt angle range that can simultaneously include the two-degree-of-freedom movable reflector 14 and the beam incident angle sensor 19 of the receiver 13. Let When the transmission device 11 cannot be directly operated manually, a camera or the like is installed on the transmission device 11 side and remotely controlled via a wireless LAN.
[2] A straight line as a set of laser light emission point candidates is defined in the reference coordinate system of the receiving device 13 from the angle information captured by the beam incident angle sensor 19 of the receiving device 13.
[3] Adjust the two-degree-of-freedom movable reflector 14 so that the center line of the search range of PSD1 and PSD2 passes on the straight line [2], and the laser beam L is detected by PSD1 and PSD2 at the intersection. Move until

図３は本発明の実施形態例に係る探索範囲の移動による光軸アライメントの初期化を示す説明図である。すなわち、ＰＳＤ１，ＰＳＤ２の探索範囲は一定の広がりを持つため探索範囲を移動していくとある時点において前記［２］で定義された直線をその範囲に含むことになり、原理的にはその時点までの間にレーザー光Ｌが探索範囲へ誘導され光軸アライメントの初期化が完了することになる。 FIG. 3 is an explanatory diagram showing initialization of the optical axis alignment by moving the search range according to the embodiment of the present invention. That is, since the search range of PSD1 and PSD2 has a certain spread, when the search range is moved, the straight line defined in [2] is included in the range at a certain point in time. In the meantime, the laser beam L is guided to the search range, and the initialization of the optical axis alignment is completed.

なお、本発明は、上記実施形態例そのままに限定されるものではなく、実施段階ではその要旨を逸脱しない範囲で構成要素を変形して具体化できる。また、上記実施形態例に開示されている複数の構成要素の適宜な組み合せにより種々の発明を形成できる。例えば、実施形態例に示される全構成要素から幾つかの構成要素を削除してもよい。更に、異なる実施形態例に亘る構成要素を適宜組み合せてもよい。 Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiment examples may be appropriately combined.

本発明の実施形態例に係る光空間通信システムの光軸アライメント初期化装置を示す構成説明図である。1 is a configuration explanatory view showing an optical axis alignment initialization apparatus of an optical space communication system according to an embodiment of the present invention. FIG. 本発明の実施形態例に係る受信装置がレーザー光を捕らえることのできる探索範囲を示す説明図である。It is explanatory drawing which shows the search range which can receive the laser beam by the receiver which concerns on the example of embodiment of this invention. 本発明の実施形態例に係る探索範囲の移動による光軸アライメントの初期化を示す説明図である。It is explanatory drawing which shows initialization of the optical axis alignment by the movement of the search range which concerns on the example of embodiment of this invention.

符号の説明Explanation of symbols

１１…送信装置、１２…２自由度可動式反射鏡、１３…受信装置、１４…２自由度可動式反射鏡、１５，１６…ビームスプリッター、１７，１８…プリズム斜面、１９…ビーム入射角センサ、２０，２１…制御部、ＬＤ…レーザーダイオード、ＰＤ…フォトディテクタ、ＰＳＤ１，ＰＳＤ２…ポジションセンシングデバイス、Ｌ…レーザー光。 DESCRIPTION OF SYMBOLS 11 ... Transmitter, 12 ... 2-degree-of-freedom movable reflector, 13 ... Receiver, 14 ... 2-degree-of-freedom movable reflector, 15, 16 ... Beam splitter, 17, 18 ... Prism slope, 19 ... Beam incident angle sensor , 20, 21 ... control unit, LD ... laser diode, PD ... photo detector, PSD1, PSD2 ... position sensing device, L ... laser light.

Claims

送信装置に、送信用レーザー光源によるレーザー光の発射方向（パン・チルト角）が調整可能なように２自由度の送信用可動式反射鏡を備え、受信装置に、送信装置から到達したレーザー光の向きを調整し直列に配置された２つのビームスプリッターへ導く２自由度の受信用可動式反射鏡と、最初のビームスプリッターにより２分した一方の分岐光を次のビームスプリッターによりさらに２分したレーザー光それぞれの照射位置を検知する２つのＰＳＤ（ＰｏｓｉｔｉｏｎＳｅｎｓｉｎｇＤｅｖｉｃｅ）と、最初のビームスプリッターによるもう１つの分岐光を受光する受信用ＰＤ（ＰｈｏｔｏＤｅｔｅｃｔｏｒ）とを備え、空間中にレーザー光を伝播させて通信を行う光空間通信システムにおいて、
受信装置にビーム入射角検出器を設置し、前記ビーム入射角検出器と前記受信用可動式反射鏡の両方をカバーするように送信装置からのレーザー光を前記送信用可動式反射鏡により高速スキャンさせたときに、前記２つのＰＳＤが前記受信用可動式反射鏡を介してレーザー光を捕らえることの可能な探索領域を前記ビーム入射角検出器が捕らえた入射光線に沿って移動させることにより送信装置からのレーザー光を受信装置のＰＳＤに導くことを特徴とする光空間通信システムの光軸アライメント初期化装置。 The transmitting device is equipped with a movable reflector for transmission with two degrees of freedom so that the emitting direction (pan / tilt angle) of the laser beam from the transmitting laser light source can be adjusted, and the laser beam that has arrived from the transmitting device to the receiving device The two-degree-of-freedom movable reflector for receiving light that is guided to two beam splitters arranged in series and one split light divided into two by the first beam splitter was further divided into two by the next beam splitter. Providing two PSDs (Position Sensing Devices) that detect the irradiation position of each laser beam and a PD (Photo Detector) for receiving another split beam from the first beam splitter, and propagating the laser beam in space In an optical space communication system for performing communication,
A beam incident angle detector is installed in the receiver, and the laser beam from the transmitter is scanned at high speed by the movable reflector for transmission so as to cover both the beam incident angle detector and the movable reflector for reception. When the two PSDs are transmitted along the incident light beam captured by the beam incident angle detector, the search area in which the two PSDs can capture the laser beam via the movable reflector for reception is transmitted. An optical axis alignment initialization device for an optical space communication system, wherein laser light from the device is guided to PSD of a receiving device.