JP3647628B2 - Satellite-type full-duplex infrared LAN system - Google Patents

Description

【０００５】
赤外線ＬＡＮでは、ｎ：ｎ通信を必要とし、しかも送信機の消費電力を抑える目的から、サテライト型システムが案出されている。これは、端末間は天井に取付けた天井取付け制御局を介して通信をするものであり、端末側送受信機は天井取付け制御局とLOSでDirected通信をし、天井取付け制御局は或るエリア内の任意の場所より通信することが求められることよりLOSでNondirected通信を行うシステムである。このシステムは、端末側送受信機の消費電力を軽減でき、赤外線ＬＡＮに適したシステムと言える。
【０００６】
一方、ＬＡＮの方式として世界で最も利用されているのが、ＣＳＭＡ／ＣＤ（Carrier Sense Multiple Access with Collision Detection）方式であり、その動作原理は次のとおりである。
【０００７】
（ａ）ネットワークに接続されている端末はネットワーク上に情報が伝送されていないかどうか確認する（ＣＳＭＡ）。
【０００８】
（ｂ）ある端末に送信したい情報がある場合、情報に相手のアドレスと自分のアドレスをつけてパケットとし、ネットワークに送る。パケットはネットワーク上のすべての方向に流れる。
【０００９】
（ｃ）端末は、送られてきたパケットが自分宛てのものであればこれを取り入れる。
【００１０】
（ｄ）２つ以上の端末が同時にアクセスする場合、パケットが衝突する。この時、衝突信号はネットワーク上の端末に通知され（ＣＤ）、送信中の端末は衝突を検出すると直ちにジャム信号を送出する。ジャム信号はＬＡＮ内の送信中の端末が確実に衝突を認識し、伝送を中断することを保証する。衝突によって伝送を中断した場合は、一定時間待って再度送信を試みる。
【００１１】
このＣＳＭＡ／ＣＤ方式はチャネル容量の８０〜９５％を使用可能な非常に効率の良い伝送方式である。そのため、このＣＳＭＡ／ＣＤを実現することが、高スループット（チャネル使用効率）を実現するとともに、既に導入されているイーサネットＬＡＮに親和性のある赤外線ＬＡＮを構築でさる。そして、この通信方式を実現するためには、送信中の如何に関わらず衝突信号の伝送が必要であり、これを赤外線空間伝送で実現しようとした場合、全二重通信の実現が不可欠である。
【００１２】
従来、赤外線ＬＡＮシステムでは、全二重通信を諦め、電波を利用した無線ＬＡＮの通信方式に利用されているＣＳＭＡ／ＣＡ（Carrier Sense Multiple Access with Collision Avoidance）方式を採用するのが一般的であった。また、全二重通信を実現するために、自分の発光した反射光をキャンセルするキャンセル方式が採用されたりしたが、十分な効果が得られているとは言えなかった。
【００１３】
【発明が解決しようとする課題】
このように赤外線空間伝送において全二重通信を実現するうえで障害となるのが、自己の発光する光の反射光を受信してしまうことである。
【００１４】
本発明はこのような難点に鑑みなされたもので、他の発信する光と自己の反射光を弁別し、自己の反射光レベルを受信感度以下に抑圧し、２波長による全二重通信、しいてはＣＳＭＡ／ＣＤ方式の通信方式を可能にするサテライト型全二重赤外線ＬＡＮシステムを提供することを目的とする。
【００１５】
【課題を解決するための手段】
この目的を達成するために本発明のサテライト型全二重赤外線ＬＡＮシステムは、赤外線を利用して室内集中制御局の制御局赤外線発受光部と複数の室内端末に接続されたそれぞれの端末赤外線発受光部との間で送受信を行なうサテライト型全二重赤外線ＬＡＮシステムであって、制御局赤外線発受光部には受光面の法線方向からの受光感度を減少し、受光面の法線から偏角した方向からの受光感度を増大する指向特性を有する凹レンズを配設してなり、凹レンズは、受光面に向かう入射側断面において法線の両側に大きな２個の屈折・反射山部を有し、出射側断面は外側から前記法線に向かって段状、鋸状の形状をもつ小さな多数の屈折・反射山部を有している。
【００１６】
また、本発明のサテライト型全二重赤外線ＬＡＮシステムは、制御局赤外線発受光部の制御局送信赤外線波長と端末赤外線発受光部の端末送信赤外線波長とは互いに異なるものである。
【００１７】
また、本発明のサテライト型全二重赤外線ＬＡＮシステムは、制御局赤外線発受光部の制御局送信赤外線波長には短波長、端末赤外線発受光部の端末送信赤外線波長には長波長を使用するものである。
【００１８】
また、本発明のサテライト型全二重赤外線ＬＡＮシステムは、制御局赤外線発受光部および端末赤外線発受光部にはそれぞれ干渉フィルタを配設したものである。
【００１９】
また、本発明のサテライト型全二重赤外線ＬＡＮシステムは、制御局赤外線発受光部には受信用に長波長側透過特性の干渉フィルタ、端末赤外線発受光部には受信用に短波長側透過特性の干渉フィルタを配設したものである。
【００２０】
また、本発明のサテライト型全二重赤外線ＬＡＮシステムは、端末赤外線発受光部には送信用に長波長側透過特性の干渉フィルタを配設したものである。
【００２１】
また、本発明のサテライト型全二重赤外線ＬＡＮシステムは、制御局赤外線発受光部には受信用にカラーフィルタを配設したものである。
【００２２】
【発明の実施の形態】
以下、本発明のサテライト型全二重赤外線ＬＡＮシステムにおける好ましい実施の形態例を説明する。
【００２３】
本発明のサテライト型全二重赤外線ＬＡＮシステムは、ネットワーク接続形態にサテライト型を採用するとともに、室内端末側と室内集中制御局側の発光部ＬＥＤの発光波長を変え、干渉フィルタを利用し自己の反射光を抑えたものである。このことにより、これまで不可能であった発光部ＬＥＤの２波長による全二重通信、しいてはＣＳＭＡ／ＣＤ方式の通信方式を可能にする。
【００２４】
全二重通信を行うためには、送信と受信の波長を変えて行えばよいのであるが、発光部ＬＥＤはレーザーのようにコヒーレンス性がないため、発光波長にある広がりがあるほか、個々の発光波長にばらつきがある。また、赤外線ＬＡＮでは、数Ｍｂｐｓの高速伝送をより少ない電力で広範囲な通信を行うことが求められる。そのためには、ＬＥＤのより良好な周波数応答特性およびより大きな電気／光変換効率を有することが必要となり、使用する発光部ＬＥＤはその組成から８００〜９００ｎｍ程度のものに限られる。そのため、この近接する波長を弁別しなければならず、特性の優れたフィルタの利用が必要となる。
【００２５】
良好なフィルタ特性を有する光学フィルタとしては、薄膜蒸着による干渉フィルタがよく知られている。しかしながら、この干渉フィルタはフィルタ特性が急峻であるが、光の入射角によりフィルタ特性が図１のように変化する欠点がある。これはネットワークの基本であるｎ：ｎ通信には、非常に不都合である。なぜなら、ｎ：ｎ通信では１：１通信と異なり、送信機と受信機間が常に一定の方向を向いているとは限らず、寧ろあらゆる方向から来る光を受信しなければならないからである。
【００２６】
しかしながら、サテライト型では、その端末側送受信機は、常に天井取付け制御局と通信するため、常に天井取付け制御局方向を向いていることになる。すなわち、天井取付け制御局は全方位からの光を受けることが必要であるが、端末側送受信機は天井取付け制御局方向を向き、制御局からの光の入射角は、垂直に入射してくる。そのため、端末側送受信機には干渉フィルタの利用が可能である。
【００２７】
次に、天井取付け制御局に干渉フィルタを適用するにあたっての技法について説明する。
【００２８】
先ず、天井取付け制御局から光を送出した時の光パワー分布を調べることとする。或るサービスエリア内を受信機の最低受信感度以上の光パワーで満たす必要があり、効果的な赤外線の放射を実現するには均一な分布とすることが望まれる。
【００２９】
図２に示すように、天井取付け制御局の発光部ＬＥＤの配置を以下のように仮定する。光源の放射する信号光電力の方向分布は一般化Lambertianモデルで与えられる。このモデルを使い光パワー分布を算出すると図３のようになる。この図３より、光パワーが比較的均一に分布し、効果的な放射をしていることが認められる。しかしながら、天井取付け制御局の真下とそこから４ｍ離れたところの単位面積当たりの光パワーとを比較すると、４ｍ地点での光パワーは真下に比べわずか５．４％である。更に、この光が反射し、天井取付け制御局の受信機に入射する光パワーを考えた場合、光パワーは距離の二乗に反比例し、また有効受光面績は光の入射角θに対し、ｃｏｓθの割合（４ｍ地点ではθ＝６３°、ｃｏｓ６３°＝０．４５４）となることを考慮すると、反射光を全部受信出来たたとしても、真下に比べ４ｍ地点からの反射光は約０．５％となる。同様に２ｍ地点の反射光は真下に比べ約１０％である。このことより、反射光は真下近辺の反射光が支配的で、周辺部からの反射光はもともと小さく無視できることがわかる。
【００３０】
ここで、天井取付け制御局（サテライト）から放射される赤外線パワーの分布モデルは以下のとおりである。
【００３１】
・水平方向には、９０°間隔で４方向（ｘプラス方向、ｘマイナス方向、ｙプラス方向、ｙマイナス方向）
・各ＬＥＤは、天井からの見下ろし角４５°で床方向を向け、Ψ＝４５°
また、ＬＥＤの仕様を以下のようにする。
【００３２】
・１方向当たりのＬＥＤ発光パワー：１Ｗ×４
・ＬＥＤ指向半値角：Φ＝４０°
以上のことより、天井取付け制御局は真下方向から帰ってくる反射光を主に抑圧すればよいことになる。
【００３３】
本発明では、天井取付け制御局の発信用発光部ＬＥＤに短波長帯発光部ＬＥＤを、受光部に長波長側通過干渉フィルタをそれぞれ利用している。そのため、自己の放射光は天井から床方向に放射され、或るエリア内の各地点より反射して帰ってくる。それぞれの反射光は、受光部に入射されるが、干渉フィルタの透過特性（入射角の増大とともに短波長側にシフトする）により、透過する光の量が入射角の増大と共に増加することになる。しかし、先に述べたように最も影響の大きい真下近辺の反射光を充分に抑圧することができるため、全体の反射光を受信感度以下に抑圧可能となる。また、真下から離れたところにある端末側送信機は、その送信用発光部ＬＥＤに長波長帯の発光部ＬＥＤを利用することから、干渉フィルタの作用によって光パワーを抑圧することもない。
【００３４】
更に、本発明では、端末用送受信機の反射光をより抑圧し、ダイナミックレンジを広げる目的で送信用発光部ＬＥＤに長波長帯透過特性の干渉フィルタを配している。これは、先に述べたように発光部ＬＥＤが広い波長分布を有したり、使用する発光部ＬＥＤの特性から送受２波長を完全に分離することは困難であるから、干渉フィルタによる弁別効果をより高めるために放射する波長を制限するものである。
【００３５】
また、自己反射の抑圧に先に述べた干渉フィルタによる弁別以外に、カラーフィルタによる弁別によっても同様の効果を達成できる。カラーフィルタは干渉フィルタと同程度のフィルタ特性を有しているが、長波長側透過特性のものしか存在しない。そのため、端末用送受信機には利用不可能であるが、天井取付け制御局用フィルタに適用可能である。しかも、カラーフィルタは干渉フィルタのように光の入射角によりフィルタ特性が変化することもない。
【００３６】
また、一部上述したようにサテライト型赤外線ＬＡＮでは、天井取付け制御局が広範囲なエリアからの通信を可能とするためには、受信機の指向特性が広角である必要がある。
【００３７】
その実現のために本発明では、天井取付け制御局の受光部に受光面の法線方向からの受光感度を減少し、受光面の法線から偏角した方向からの受光感度を増大する指向特性を有する凹レンズを備え、それぞれの自己の反射光を効果的に抑えるとともに、天井取付け制御局の指向特性を広角にし、通信エリアの広い全二重通信を可能にする。また、室内端末側と室内集中制御局側の発光部ＬＥＤの発光波長を変えるとともに、天井取付け制御局及ぴ端末側送受信機の受信部に干渉フィルタを備えることによって自己反射の抑圧の効果をより確かなものにしている。
【００３８】
本発明では、このような特性を有する凹レンズを利用することにより、最も反射光の大きいエリア方向の受信感度を低くし、端末側送受信機からの信号光を受信し易くするため、感度を高めている。
【００３９】
また、システム構築の柔軟性を考えた場合、より反射光を抑圧するシステムが望まれる。そのためには、上述の凹レンズの使用に加え、天井取付け制御局と端末側送受信機の送信用発光部ＬＥＤの発光に波長の異なる２波長を用い、受光部でフィルタにより弁別する方法が取られる。先に述べたように発光部ＬＥＤの非コヒーレンス性や干渉フィルタの特性の不十分さなどにより充分な弁別が出来なくとも、先の凹レンズ効果とあいまって、大きな自己反射の抑圧効果が得られる。
【００４０】
【実施例】
以下、本発明のサテライト型全二重赤外線ＬＡＮシステムにおける好ましい実施例を図面にしたがって説明する。
【００４１】
図４に本発明の第１の実施例によるサテライト型全二重赤外線ＬＡＮシステムを示す。赤外線ＬＡＮでは、室内端末１の消費電力を抑えたり、安全性の観点から端末側送信機３の発光部５における発光部ＬＥＤの発光パワーを極力抑えることが求められる。採用したサテライト型赤外線ＬＡＮシステムは、端末側送受信機３、４を天井取付け制御局２方向に上向けるため、光軸調整が必要となるが、端末側送信機３から天井取付け制御局２への伝播損失は６５ｄＢと比較的小さく（表１）、赤外線ＬＡＮを実現する最も現実的なシステムであると言える。
【００４２】
本発明の実施例の主要諸元を表２に示し、天井取付け制御局２と端末側送受信機３、４の発受光部５、６の構造を図４に示す。天井取付け制御局２は制御局側送受信機７、８を備え、それぞれ発受光部９、１０を有している。
【００４３】
【表２】

【００４４】
天井取付け制御局２は広範囲からの光を受ける構造となっている。勿論、その受信エリアと兼ね合いより、受光部１０にレンズを取付け集光することも可能である。受光部１０には、自己の反射光を抑圧するために長波長側透過干渉フィルタ１２を備えている。発光部９には短波長側透過干渉フィルタ１２ａを備えている。
【００４５】
端末側受光部６には、自己の反射光を抑圧するために短波長側透過干渉フィルタ１３を備えている。端末側受光部６は天井取付け制御局２方向を向き、干渉フィルタ１３面に対し垂直方向からの光を中心に受光する仕組となっている。更に、端末側受光部６には、太陽光などの背景光を抑圧するために長波長側透過特性を有する樹脂製の可視光抑圧フィルタ１４を備えている。このため、結果的に光学的バンドパス・フィルタの特性を実現していることになる。また、天井取付け制御局２と同様に、受光部６にレンズを取付け集光することも可能である。なお、１８は受光部６のフォトダイオードレンズを示す。発光部５には長波長側透過干渉フィルタ１３ａを備えている。更に、端末用送信機３の反射光をより抑圧し、ダイナミックレンジを広げる目的で送信用発光部５の発光部ＬＥＤに長波長帯透過特性の干渉フィルタ１３ｂを配している。これは、先に述べたように発光部ＬＥＤが広い波長分布を有したり、使用する発光部ＬＥＤの特性から送受２波長を完全に分離することは困難であるから、干渉フィルタによる弁別効果をより高めるために放射する波長を制限するものである。端末側受光部６と同様に、端末側発光部５、制御局側発光部９、制御局側発受光部１０にはそれぞれ太陽光などの背景光を抑圧するために長波長側透過特性を有する樹脂製の可視光抑圧フィルタ１５、１６、１７を備えている。
【００４６】
更に、天井取付制御局２と端末側送信機３のそれぞれの発光部５、発光部９における発光部ＬＥＤの発光波長は明確に離れている必要はない。自己の放射する反射光を受信感度以下に抑えればよいから、何割か抑制できる程度、たとえば、８５０ｎｍと８９０ｎｍといった程度の波長の違いでも十分に実現可能である。図５に本実施例における制御局２及び端末側１の発光部５、９の発光波長及び干渉フィルタ１２、１３の透過特性を示し、干渉フィルタ１２、１３のカットオフ波長が制御局発光部９の発光部ＬＥＤの発光波長よりに設定してある。これは、端末側送受信機３、４の携帯端末のネットワーク接続を想定し、低消費電力化を図るための措置として干渉フィルタ１３により端末側発光部５の発光部ＬＥＤの受光パワーが少なくなるのを防ぐためである。
【００４７】
図６に本発明の第２の実施例によるサテライト型全二重赤外線ＬＡＮシステムを示す。赤外線ＬＡＮでは、室内端末１の消費電力を抑えたり、安全性の観点から端末側送信機３の発光部５における発光部ＬＥＤの発光パワーを極力抑えることが求められる。サテライト型赤外線ＬＡＮシステムは、端末側受信機４を天井取付け制御局２の方向に上向けるため、光軸調整が必要となるが、端末側送信機３から天井取付側制御局２への伝播損失が６５ｄＢと比較的小さく（表１）、赤外線ＬＡＮを実現する最も現実的なシステムであると言える。
【００４８】
本発明の実施例の主要諸元を表２に示し、天井取付け制御局２と端末１側の受光部の構造を図６に示す。
【００４９】
天井取付け制御局２は広範囲からの光を受ける構造となっている。勿論、その受信エリアと兼ね合いより、受光部１０にレンズを取り付け集光することも可能である。受光部１０は、自己の反射光を抑圧するために短波長側透過特性のカラーフィルタ２０を備えている。
【００５０】
端末側受光部６は、自己の反射光を抑圧するために短波長側透過特性の干渉フィルタ１３を備えている。端末側受光部６は天井取付け制御局２の方向を向き、干渉フィルタ１３の面に対し垂直方向からの光を中心に受光する仕組となっている。更に、太陽光などの背景光を抑圧するために長波長側透過特性を有する樹脂性の可視光抑圧フィルタ１４を備えている。このため、結果的に光学的バンドパス・フィルタの特性を実現していることになる。また、天井取付け制御局２と同様に、受光部６に集光用のレンズを取付けることも可能である。
【００５１】
更に、天井取付制御局２の発光部９（図７）と端末側１の送信機４の発光部５における発光部ＬＥＤの発光波長は実施例のように明確に離れている必要はない。自己の放射する反射光を受信感度以下に抑えればよいから、何割か抑圧できる程度、たとえば、８５０ｎｍと８９０ｎｍといった程度の波長の違いでも十分に実現可能である。
【００５２】
室内集中制御局２及び室内端末側１の発光部９、５の発光波長及びフィルタ１２、１３の透過特性を図５に示す。ここで、フィルタのカットオフ波長が室内集中制御局２の発光部９における発光部ＬＥＤの発光波長よりに設定してある。これは、室内端末１側はそのアプリケーションとしてモバイル・コンピューティングが考えられ、携帯端末のネットワーク接続を想定し、低消費電力化を図る必要から、干渉フィルタ１３により端末側発光部ＬＥＤの受光パワーが少なくなるのを防ぐためのものである。
【００５３】
図７に本発明の第３の実施例によるサテライト型全二重赤外線ＬＡＮシステムを示す。
【００５４】
本実施例では、天井取付け制御局２の受信部１０に受光面２６の法線方向２７からの受光感度を減少し、受光面２６の法線から偏角した方向２８からの受光感度を増大する指向特性を有する凹レンズ２５を備え、それぞれの自己の反射光を効果的に抑えるとともに、天井取付け制御局２の指向特性を広角にし、通信エリアの広い全二重通信を可能にする。凹レンズ２５は図８（ａ）に示すように受光面２６に向かう入射側断面において法線方向の両側に大きな２個の屈折・反射山部２９ａ、２９ｂを有し、出射側断面は外側から法線に向かって段状、鋸状の形状をもつ小さな多数の屈折・反射山部３０を有する。また、室内端末１側と室内集中制御局２側の発光部９、５における発光部ＬＥＤの発光波長を変えるとともに、天井取付け制御局２及び室内端末側１の送受信機３、４、７、８の受信部１０、６に干渉フィルタ１３、１３ａ、１２、１２ａを備えることによって自己反射の抑圧の効果をより確かなものにしている。
【００５５】
本発明では、図８（ｂ）に示す特性を有する凹レンズを利用することにより、最も反射光の大きいエリア方向の受信感度を低くし、端末側１の送受信機３、４からの信号光を受信し易くするため、感度を高めている。図８（ｃ）において、レンズのない場合の光の入射角に対する受信感度は■で示される特性を示し、本発明のレンズは◆で示される特性を示す。図より、凹レンズを入れることにより入射角０°の場合は、受光感度を約６０％に低減できる。すなわち、反射光を４０％抑えることが可能となる。更に、凹レンズのない場合は、入射角が大きくなると受信感度が急激に減少し、端末側送受信機からの光を急激に受信出来なくなるが、凹レンズを入れることによりこれを大幅に改善できる。
【００５６】
また、システム構築の柔軟性を考えた場合、より反射光を抑圧するシステムが望まれる。そのためには、上述レンズの使用に加え、天井取付け制御局２と端末１側の送信機３、７の発光部ＬＥＤの発光を波長の異なる２波長を用い、受信部で干渉フィルタにより弁別する方法が取られる。先に述べたように発光部ＬＥＤの非コヒーレンス性や干渉フィルタの特性の不十分さなどにより充分な弁別が出来なくとも、先の凹レンズ効果とあいまって、大きな自己反射の抑圧効果が得られる。
【００５７】
こうして図９に示すように本発明のサテライト型全二重赤外線ＬＡＮシステムによれば、室内の天井取付け制御局２と室内端末１ａ、１ｂ間において全二重で赤外線通信でネットワーク接続することができる。
【００５８】
【発明の効果】
以上の説明から明らかなように、本発明のサテライト型全二重赤外線ＬＡＮシステムによれば、これまで不可能とされてきた赤外線全二重通信を実現するものであり、ネットワークの通信方式として最も普及しているＣＳＭＡ／ＣＤ方式の衝突信号の伝送を可能にし、ＣＳＭＡ／ＣＤ方式に親和性がありスループットの高い赤外線ＬＡＮシステムを実現可能である。
【図面の簡単な説明】
【図１】 本発明の第１の実施例によるサテライト型全二重赤外線ＬＡＮシステムに使用する干渉フィルタにおける光の入射角と透過率の関係を示す図。
【図２】 本発明の第１の実施例によるサテライト型全二重赤外線ＬＡＮシステムのサテライトとしての天井取付け制御局が放射する赤外線のパワー分布モデルを示す図。
【図３】 本発明の第１の実施例によるサテライト型全二重赤外線ＬＡＮシステムの光パワー分布計算結果を示す図。
【図４】 （ａ）、（ｂ）は本発明の第１の実施例によるサテライト型全二重赤外線ＬＡＮシステムの天井取付け制御局と端末側送受信機の発受光部の構造を示す図。
【図５】 本発明の第１の実施例によるサテライト型全二重赤外線ＬＡＮシステムの干渉フィルタの特性を示す図。
【図６】 本発明の第２の実施例によるサテライト型全二重赤外線ＬＡＮシステムの天井取付け制御局と端末側送受信機の発受光部の構造を示す図。
【図７】 （ａ）、（ｂ）は本発明の第３の実施例によるサテライト型全二重赤外線ＬＡＮシステムの天井取付け制御局と端末側送受信機の発受光部の構造を示す図。
【図８】 （ａ）は本発明の第３の実施例によるサテライト型全二重赤外線ＬＡＮシステムの凹レンズの構造を示す図、（ｂ）は本発明の第３の実施例によるサテライト型全二重赤外線ＬＡＮシステムの凹レンズを利用した場合の相対的受信感度を示す図。
【図９】 本発明のサテライト型全二重赤外線ＬＡＮシステムの実施形態例を示す図。
【図１０】 従来の光ＬＡＮシステムの形態を示す図。
【符号の説明】
１・・・・・室内端末
２・・・・・室内集中制御局（天井取付け制御局）
５、６・・・・・端末赤外線発受光部
９、１０・・・・・制御局赤外線発受光部
１２、１２ａ、１３、１３ａ・・・・・干渉フィルタ
２０・・・・・カラーフィルタ
２５・・・・・凹レンズ
２６・・・・・受光面
２７・・・・・法線方向
２８・・・・・法線から偏角した方向
２９ａ、２９ｂ・・・・・（大きな）屈折・反射山部
３０・・・・・（小さな）屈折・反射山部 [0001]
BACKGROUND OF THE INVENTION
The present invention relates to a satellite-type full-duplex infrared LAN system, and in particular, a satellite-type full-duplex in which a centralized control station is arranged in a room, and a terminal is connected to a network by infrared communication with the centralized control station in full-duplex. The present invention relates to an infrared LAN system.
[0002]
[Prior art]
In general, in a data transmission system using infrared rays, six types shown in FIG. 10 are conceivable depending on the positional relationship between a transmitter and a receiver and whether the light to be used is direct light or reflected light.
[0003]
As shown in the figure, an infrared spatial transmission system that is basically used indoors requires a line-of-sight (LOS) type that uses direct light and requires a line-of-sight path, and a line-of-sight path that uses reflected light. Non-LOS (Non-Line of Sight) type. Furthermore, the degree of strictness with respect to the alignment of the optical axis between the transmitter and the receiver varies depending on the spread of the light radiation beam of the transmitter and the viewing angle of the receiver, and the Directed type and Nondirected (reflected light). ) Type and Hybrid (intermediate) type. Table 1 shows the characteristics when the Directed type, Nondirected type, Line of Sight type, and Non-Line of Sight type are combined.
[0004]
[Table 1]

[0005]
In the infrared LAN, a satellite type system has been devised for the purpose of requiring n: n communication and reducing the power consumption of the transmitter. This is because the terminals communicate with each other via a ceiling-mounted control station mounted on the ceiling. The terminal-side transceiver communicates directly with the ceiling-mounted control station using LOS, and the ceiling-mounted control station is in a certain area. It is a system that performs Nondirected communication with LOS because it is required to communicate from any place. This system can reduce the power consumption of the terminal-side transceiver and can be said to be a system suitable for an infrared LAN.
[0006]
On the other hand, the most widely used LAN system in the world is the CSMA / CD (Carrier Sense Multiple Access with Collision Detection) system, and its operation principle is as follows.
[0007]
(A) A terminal connected to the network checks whether information is transmitted on the network (CSMA).
[0008]
(B) When there is information to be transmitted to a certain terminal, the other party's address and one's own address are attached to the information to form a packet and sent to the network. Packets flow in all directions on the network.
[0009]
(C) The terminal takes in the sent packet if it is addressed to itself.
[0010]
(D) When two or more terminals access simultaneously, packets collide. At this time, the collision signal is notified to the terminal on the network (CD), and the transmitting terminal immediately transmits a jam signal when the collision is detected. The jam signal ensures that the transmitting terminal in the LAN recognizes the collision and interrupts the transmission. If transmission is interrupted due to a collision, it will try again after a certain period of time.
[0011]
This CSMA / CD system is a very efficient transmission system that can use 80 to 95% of the channel capacity. Therefore, realization of this CSMA / CD realizes high throughput (channel use efficiency) and constructs an infrared LAN having affinity with the already installed Ethernet LAN. In order to realize this communication method, it is necessary to transmit a collision signal regardless of whether it is being transmitted. If this is to be realized by infrared spatial transmission, it is indispensable to realize full-duplex communication. .
[0012]
Conventionally, in infrared LAN systems, CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method, which is used for wireless LAN communication method using radio waves, has been generally adopted. It was. Moreover, in order to realize full-duplex communication, a canceling method for canceling the reflected light emitted by itself is adopted, but it cannot be said that a sufficient effect is obtained.
[0013]
[Problems to be solved by the invention]
Thus, the obstacle to realizing full-duplex communication in infrared space transmission is receiving the reflected light of the light emitted by itself.
[0014]
The present invention has been made in view of such difficulties, and discriminates other transmitted light from its own reflected light, suppresses its own reflected light level below reception sensitivity, and performs full-duplex communication by two wavelengths. It is an object of the present invention to provide a satellite-type full-duplex infrared LAN system that enables a CSMA / CD communication system.
[0015]
[Means for Solving the Problems]
In order to achieve this object, the satellite-type full-duplex infrared LAN system of the present invention uses infrared light to transmit and receive each terminal infrared light emitting / receiving unit connected to the control station infrared light emitting / receiving unit of the indoor centralized control station and a plurality of indoor terminals. This is a satellite-type full-duplex infrared LAN system that transmits and receives data to and from the light receiving unit, and the control station infrared light emitting and receiving unit reduces the light receiving sensitivity from the normal direction of the light receiving surface and deviates from the normal of the light receiving surface. Concave lenses having directivity characteristics that increase the light receiving sensitivity from the angled direction are arranged, and the concave lens has two large refraction / reflection crests on both sides of the normal line in the incident side cross section toward the light receiving surface. The exit side cross section has a large number of small refracting / reflective peaks having stepped and saw-like shapes from the outside toward the normal line.
[0016]
In the satellite-type full-duplex infrared LAN system of the present invention, the control station transmission infrared wavelength of the control station infrared transmission / reception unit and the terminal transmission infrared wavelength of the terminal infrared transmission / reception unit are different from each other.
[0017]
The satellite-type full-duplex infrared LAN system of the present invention uses a short wavelength for the control station transmission infrared wavelength of the control station infrared light emitting and receiving unit and a long wavelength for the terminal transmission infrared wavelength of the terminal infrared light emitting and receiving unit. It is.
[0018]
In the satellite type full-duplex infrared LAN system of the present invention, an interference filter is provided in each of the control station infrared emitting / receiving unit and the terminal infrared emitting / receiving unit.
[0019]
In addition, the satellite type full-duplex infrared LAN system of the present invention has a long wavelength transmission characteristic interference filter for reception in the control station infrared transmission / reception unit, and a short wavelength transmission characteristic for reception in the terminal infrared transmission / reception unit. This interference filter is provided.
[0020]
In the satellite-type full-duplex infrared LAN system of the present invention, an interference filter having long-wavelength side transmission characteristics is arranged for transmission at the terminal infrared light emitting / receiving unit.
[0021]
In the satellite-type full-duplex infrared LAN system of the present invention, a color filter is provided for reception in the control station infrared emitting / receiving unit.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the satellite-type full-duplex infrared LAN system of the present invention will be described.
[0023]
The satellite full-duplex infrared LAN system of the present invention adopts a satellite type as a network connection form, changes the light emission wavelength of the light emitting unit LED on the indoor terminal side and the indoor central control station side, and uses an interference filter to The reflected light is suppressed. This enables full-duplex communication by two wavelengths of the light emitting unit LED, which has been impossible until now, that is, a CSMA / CD communication method.
[0024]
In order to perform full-duplex communication, it is only necessary to change the wavelength of transmission and reception, but since the light emitting unit LED has no coherence like a laser, there is a spread in the light emission wavelength, There are variations in emission wavelength. In addition, in the infrared LAN, it is required to perform wide-range communication with less power for high-speed transmission of several Mbps. For that purpose, it is necessary to have a better frequency response characteristic and a larger electric / light conversion efficiency of the LED, and the light emitting part LED to be used is limited to one having a composition of about 800 to 900 nm. Therefore, it is necessary to discriminate between these adjacent wavelengths, and it is necessary to use a filter having excellent characteristics.
[0025]
As an optical filter having good filter characteristics, an interference filter by thin film deposition is well known. However, this interference filter has a steep filter characteristic, but has a drawback that the filter characteristic changes as shown in FIG. 1 depending on the incident angle of light. This is very inconvenient for n: n communication which is the basis of the network. This is because, unlike the 1: 1 communication, the n: n communication does not always have a fixed direction between the transmitter and the receiver, but rather has to receive light coming from all directions.
[0026]
However, in the satellite type, since the terminal-side transceiver always communicates with the ceiling-mounted control station, it always faces the ceiling-mounted control station. In other words, the ceiling-mounted control station needs to receive light from all directions, but the terminal-side transceiver faces the ceiling-mounted control station, and the incident angle of light from the control station is incident vertically. . Therefore, an interference filter can be used for the terminal-side transceiver.
[0027]
Next, a technique for applying the interference filter to the ceiling-mounted control station will be described.
[0028]
First, the optical power distribution when light is transmitted from the ceiling-mounted control station is examined. It is necessary to fill a certain service area with optical power equal to or higher than the minimum receiving sensitivity of the receiver, and a uniform distribution is desired to realize effective infrared radiation.
[0029]
As shown in FIG. 2, the arrangement of the light emitting units LED of the ceiling-mounted control station is assumed as follows. The directional distribution of signal light power emitted by the light source is given by the generalized Lambertian model. FIG. 3 shows the light power distribution calculated using this model. It can be seen from FIG. 3 that the optical power is distributed relatively uniformly and emits effectively. However, when comparing the optical power per unit area just below the ceiling-mounted control station and 4 m away from it, the optical power at the point of 4 m is only 5.4% as compared to just below. Furthermore, when the light power reflected and incident on the receiver of the ceiling-mounted control station is considered, the light power is inversely proportional to the square of the distance, and the effective light receiving surface is cos θ with respect to the light incident angle θ. In consideration of the ratio (θ = 63 °, cos63 ° = 0.454 at the 4m point), even if all the reflected light can be received, the reflected light from the 4m point is about 0.5 %. Similarly, the reflected light at the 2m point is about 10% compared to the position just below. From this, it is understood that the reflected light is predominantly near the bottom, and the reflected light from the peripheral part is originally small and can be ignored.
[0030]
Here, the distribution model of the infrared power radiated from the ceiling-mounted control station (satellite) is as follows.
[0031]
・ In the horizontal direction, 4 directions at 90 ° intervals (x plus direction, x minus direction, y plus direction, y minus direction)
・ Each LED faces the floor at a 45 ° angle from the ceiling, Ψ = 45 °
Moreover, the specification of LED is as follows.
[0032]
-LED emission power per direction: 1W x 4
LED half-value angle: Φ = 40 °
From the above, the ceiling-mounted control station has only to suppress the reflected light returning from directly below.
[0033]
In the present invention, a short wavelength light emitting unit LED is used as a light emitting unit LED for transmission of a ceiling mounted control station, and a long wavelength side interference filter is used as a light receiving unit. Therefore, the self-radiated light is radiated from the ceiling toward the floor and reflected back from each point in a certain area. Each reflected light is incident on the light-receiving unit, but the amount of transmitted light increases as the incident angle increases due to the transmission characteristics of the interference filter (shifts to the short wavelength side as the incident angle increases). . However, as described above, the reflected light in the vicinity immediately under the greatest influence can be sufficiently suppressed, so that the entire reflected light can be suppressed below the reception sensitivity. In addition, since the terminal-side transmitter that is located immediately below the light-emitting unit LED in the long wavelength band is used for the light-emitting unit LED for transmission, the optical power is not suppressed by the action of the interference filter.
[0034]
Furthermore, in the present invention, an interference filter having a long wavelength band transmission characteristic is arranged in the light emitting LED for transmission in order to further suppress the reflected light of the transmitter / receiver for the terminal and widen the dynamic range. As described above, the light emitting unit LED has a wide wavelength distribution, or it is difficult to completely separate the transmission and reception two wavelengths from the characteristics of the light emitting unit LED to be used. In order to increase it, the wavelength to be emitted is limited.
[0035]
In addition to the discrimination by the interference filter described above for suppression of self-reflection, the same effect can be achieved by the discrimination by the color filter. The color filter has a filter characteristic comparable to that of the interference filter, but only has a long wavelength side transmission characteristic. Therefore, it cannot be used for a terminal transceiver, but can be applied to a filter for a ceiling-mounted control station. Moreover, the color filter does not change its filter characteristics depending on the incident angle of light unlike the interference filter.
[0036]
Further, as described above in part, in the satellite infrared LAN, in order for the ceiling-mounted control station to communicate from a wide area, the directivity of the receiver needs to be wide-angle.
[0037]
For this purpose, the present invention reduces the light receiving sensitivity from the normal direction of the light receiving surface to the light receiving part of the ceiling mounted control station, and increases the light receiving sensitivity from the direction deviated from the normal of the light receiving surface. In addition to effectively suppressing the reflected light of each self, the directivity characteristics of the ceiling-mounted control station are widened to enable full-duplex communication with a wide communication area. In addition, the emission wavelength of the light emitting unit LED on the indoor terminal side and the indoor central control station side is changed, and the interference filter is provided on the receiving unit of the ceiling mounted control station and the terminal side transceiver to further suppress the effect of self-reflection. Make sure.
[0038]
In the present invention, by using a concave lens having such characteristics, the reception sensitivity in the area direction where the reflected light is the largest is lowered and the signal light from the terminal-side transceiver is easily received. Yes.
[0039]
Moreover, when considering the flexibility of system construction, a system that suppresses reflected light is desired. For this purpose, in addition to the use of the concave lens described above, a method is used in which two wavelengths having different wavelengths are used for light emission of the transmission light emitting unit LED of the ceiling mounted control station and the terminal-side transceiver, and the light receiving unit discriminates with a filter. As described above, even if sufficient discrimination cannot be performed due to the non-coherence property of the light emitting unit LED and insufficient characteristics of the interference filter, a large self-reflection suppression effect is obtained in combination with the concave lens effect.
[0040]
【Example】
Hereinafter, preferred embodiments of the satellite-type full-duplex infrared LAN system of the present invention will be described with reference to the drawings.
[0041]
FIG. 4 shows a satellite-type full-duplex infrared LAN system according to the first embodiment of the present invention. In the infrared LAN, it is required to suppress the power consumption of the indoor terminal 1 and to suppress the light emission power of the light emitting unit LED in the light emitting unit 5 of the terminal side transmitter 3 as much as possible from the viewpoint of safety. The satellite-type infrared LAN system adopted requires the optical transceiver to be adjusted because the terminal-side transceivers 3 and 4 are directed upward in the direction of the ceiling-mounted control station 2, but the terminal-side transmitter 3 is connected to the ceiling-mounted control station 2. Propagation loss is relatively small at 65 dB (Table 1), which can be said to be the most realistic system for realizing an infrared LAN.
[0042]
The main specifications of the embodiment of the present invention are shown in Table 2, and the structures of the light emitting / receiving sections 5 and 6 of the ceiling mounting control station 2 and the terminal side transceivers 3 and 4 are shown in FIG. The ceiling-mounted control station 2 includes control station side transceivers 7 and 8, and has light emitting and receiving portions 9 and 10, respectively.
[0043]
[Table 2]

[0044]
The ceiling-mounted control station 2 has a structure that receives light from a wide range. Of course, it is also possible to collect light by attaching a lens to the light receiving unit 10 in consideration of the reception area. The light receiving unit 10 includes a long wavelength side transmission interference filter 12 in order to suppress the reflected light of itself. The light emitting unit 9 includes a short wavelength side transmission interference filter 12a.
[0045]
The terminal side light receiving unit 6 includes a short wavelength side transmission interference filter 13 in order to suppress its own reflected light. The terminal-side light receiving unit 6 faces the ceiling-mounted control station 2 and receives light mainly from the direction perpendicular to the surface of the interference filter 13. Further, the terminal side light receiving unit 6 includes a resin visible light suppression filter 14 having a long wavelength side transmission characteristic in order to suppress background light such as sunlight. As a result, the characteristics of the optical bandpass filter are realized. Similarly to the ceiling-mounted control station 2, it is also possible to collect light by attaching a lens to the light receiving unit 6. Reference numeral 18 denotes a photodiode lens of the light receiving unit 6. The light emitting unit 5 includes a long wavelength side transmission interference filter 13a. Further, an interference filter 13b having a long wavelength band transmission characteristic is disposed in the light emitting unit LED of the transmission light emitting unit 5 for the purpose of further suppressing the reflected light of the terminal transmitter 3 and extending the dynamic range. As described above, the light emitting unit LED has a wide wavelength distribution, or it is difficult to completely separate the transmission and reception two wavelengths from the characteristics of the light emitting unit LED to be used. In order to increase it, the wavelength to be emitted is limited. Similar to the terminal-side light receiving unit 6, the terminal-side light emitting unit 5, the control station-side light emitting unit 9, and the control station-side light emitting / receiving unit 10 each have long-wavelength side transmission characteristics to suppress background light such as sunlight. Resin visible light suppression filters 15, 16, and 17 are provided.
[0046]
Furthermore, the light emission wavelengths of the light emitting units LED in the light emitting unit 5 and the light emitting unit 9 of the ceiling mounting control station 2 and the terminal-side transmitter 3 do not have to be clearly separated. Since it is only necessary to suppress the reflected light radiated by itself below the reception sensitivity, even a difference in wavelength such as 850 nm and 890 nm can be sufficiently realized. FIG. 5 shows the emission wavelengths of the light emitting units 5 and 9 on the control station 2 and the terminal side 1 and the transmission characteristics of the interference filters 12 and 13 in this embodiment, and the cutoff wavelength of the interference filters 12 and 13 is the control station light emitting unit 9. It is set from the light emission wavelength of the light emitting part LED. Assuming that the mobile terminals of the terminal side transceivers 3 and 4 are connected to the network, the interference filter 13 reduces the light receiving power of the light emitting unit LED of the terminal side light emitting unit 5 as a measure for reducing power consumption. Is to prevent.
[0047]
FIG. 6 shows a satellite type full-duplex infrared LAN system according to a second embodiment of the present invention. In the infrared LAN, it is required to suppress the power consumption of the indoor terminal 1 and to suppress the light emission power of the light emitting unit LED in the light emitting unit 5 of the terminal-side transmitter 3 as much as possible from the viewpoint of safety. The satellite infrared LAN system requires the optical axis to be adjusted because the terminal-side receiver 4 is directed toward the ceiling-mounted control station 2, but the propagation loss from the terminal-side transmitter 3 to the ceiling-mounted control station 2 is necessary. Is relatively small at 65 dB (Table 1), and can be said to be the most realistic system for realizing an infrared LAN.
[0048]
Table 2 shows the main specifications of the embodiment of the present invention, and FIG. 6 shows the structure of the light receiving unit on the ceiling-mounted control station 2 and the terminal 1 side.
[0049]
The ceiling-mounted control station 2 has a structure that receives light from a wide range. Of course, it is also possible to collect light by attaching a lens to the light receiving unit 10 in consideration of the reception area. The light receiving unit 10 includes a color filter 20 having a transmission characteristic on the short wavelength side in order to suppress its own reflected light.
[0050]
The terminal side light receiving unit 6 includes an interference filter 13 having a short wavelength side transmission characteristic in order to suppress the reflected light of itself. The terminal-side light receiving unit 6 faces the ceiling-mounted control station 2 and receives light centered on light from a direction perpendicular to the surface of the interference filter 13. Further, a resinous visible light suppression filter 14 having a long wavelength side transmission characteristic is provided to suppress background light such as sunlight. As a result, the characteristics of the optical bandpass filter are realized. Similarly to the ceiling-mounted control station 2, it is possible to attach a condensing lens to the light receiving unit 6.
[0051]
Further, the light emission wavelengths of the light emitting units LED in the light emitting unit 9 (FIG. 7) of the ceiling mounting control station 2 and the light emitting unit 5 of the transmitter 4 on the terminal side 1 do not need to be clearly separated as in the embodiment. Since it is only necessary to suppress the reflected light radiated by itself below the receiving sensitivity, even a difference in wavelength such as 850 nm and 890 nm can be sufficiently realized.
[0052]
FIG. 5 shows the emission wavelengths of the light emitting units 9 and 5 on the indoor central control station 2 and the indoor terminal side 1 and the transmission characteristics of the filters 12 and 13. Here, the cutoff wavelength of the filter is set to be greater than the emission wavelength of the light emitting unit LED in the light emitting unit 9 of the indoor central control station 2. This is because mobile computing is considered as an application on the indoor terminal 1 side, and it is necessary to reduce power consumption assuming a network connection of a portable terminal. Therefore, the light reception power of the terminal side light emitting unit LED is reduced by the interference filter 13. This is to prevent the decrease.
[0053]
FIG. 7 shows a satellite type full-duplex infrared LAN system according to a third embodiment of the present invention.
[0054]
In the present embodiment, the light receiving sensitivity from the normal direction 27 of the light receiving surface 26 is decreased in the receiving unit 10 of the ceiling mounted control station 2 and the light receiving sensitivity from the direction 28 deviated from the normal line of the light receiving surface 26 is increased. A concave lens 25 having directivity is provided to effectively suppress the reflected light of each self, and the directivity of the ceiling-mounted control station 2 is widened to enable full duplex communication with a wide communication area. As shown in FIG. 8A, the concave lens 25 has two large refracting / reflective peaks 29a and 29b on both sides in the normal direction in the incident side cross section toward the light receiving surface 26, and the emission side cross section is normal from the outside. A large number of small refracting / reflective peaks 30 having a stepped shape and a saw shape toward the line are provided. Moreover, while changing the light emission wavelength of light emission part LED in the light emission parts 9 and 5 of the indoor terminal 1 side and the indoor centralized control station 2 side, the transceivers 3, 4, 7, 8 of the ceiling-mounted control station 2 and the indoor terminal side 1 are changed. By providing the interference filters 13, 13a, 12, and 12a in the receiving units 10 and 6, the effect of suppressing self-reflection is further ensured.
[0055]
In the present invention, by using a concave lens having the characteristics shown in FIG. 8B, the reception sensitivity in the area direction where the reflected light is the largest is lowered, and the signal light from the transceivers 3 and 4 on the terminal side 1 is received. Sensitivity is increased to make it easier. In FIG. 8 (c) , the reception sensitivity with respect to the incident angle of light in the absence of a lens shows the characteristic indicated by ▪ , and the lens of the present invention shows the characteristic indicated by ◆ . From the figure, it is possible to reduce the light receiving sensitivity to about 60% when the incident angle is 0 ° by inserting a concave lens. That is, the reflected light can be suppressed by 40%. Further, in the case where there is no concave lens, the reception sensitivity decreases rapidly as the incident angle increases, and it becomes impossible to receive light from the terminal-side transceiver abruptly. However, this can be greatly improved by inserting a concave lens.
[0056]
Moreover, when considering the flexibility of system construction, a system that suppresses reflected light is desired. For this purpose, in addition to the use of the lens described above, a method of discriminating light emitted from the light emitting section LEDs of the ceiling-mounted control station 2 and the transmitters 3 and 7 on the terminal 1 side using two wavelengths having different wavelengths by an interference filter at the receiving section Is taken. As described above, even if sufficient discrimination cannot be performed due to the non-coherence property of the light emitting unit LED and insufficient characteristics of the interference filter, a large self-reflection suppression effect is obtained in combination with the concave lens effect.
[0057]
Thus, as shown in FIG. 9, according to the satellite-type full-duplex infrared LAN system of the present invention, it is possible to establish a network connection between the indoor ceiling-mounted control station 2 and the indoor terminals 1a and 1b by full-duplex infrared communication. .
[0058]
【The invention's effect】
As is apparent from the above description, the satellite full-duplex infrared LAN system of the present invention realizes infrared full-duplex communication that has been impossible until now, and is the most network communication method. It is possible to transmit a collision signal of the popular CSMA / CD system, and it is possible to realize an infrared LAN system having a high throughput and affinity to the CSMA / CD system.
[Brief description of the drawings]
FIG. 1 is a diagram showing the relationship between light incident angle and transmittance in an interference filter used in a satellite full-duplex infrared LAN system according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an infrared power distribution model emitted by a ceiling-mounted control station as a satellite of the satellite-type full-duplex infrared LAN system according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a calculation result of optical power distribution of the satellite type full-duplex infrared LAN system according to the first embodiment of the present invention.
FIGS. 4A and 4B are diagrams showing structures of a ceiling-mounted control station and a light emitting / receiving unit of a terminal-side transceiver in a satellite-type full-duplex infrared LAN system according to a first embodiment of the present invention.
FIG. 5 is a diagram showing the characteristics of the interference filter of the satellite full-duplex infrared LAN system according to the first embodiment of the present invention.
FIG. 6 is a diagram showing structures of a ceiling-mounted control station and a light emitting / receiving unit of a terminal-side transceiver in a satellite-type full-duplex infrared LAN system according to a second embodiment of the present invention.
FIGS. 7A and 7B are diagrams showing structures of a ceiling-mounted control station and a light emitting / receiving unit of a terminal-side transceiver in a satellite-type full-duplex infrared LAN system according to a third embodiment of the present invention.
8A is a diagram showing the structure of a concave lens of a satellite-type full-duplex infrared LAN system according to a third embodiment of the present invention, and FIG. 8B is a satellite-type full-duplex according to the third embodiment of the present invention. The figure which shows the relative receiving sensitivity at the time of using the concave lens of a heavy infrared LAN system.
FIG. 9 is a diagram showing an embodiment of a satellite-type full-duplex infrared LAN system of the present invention.
FIG. 10 is a diagram showing a form of a conventional optical LAN system.
[Explanation of symbols]
1 ... Indoor terminal 2 ... Indoor central control station (ceiling mounting control station)
5, 6... Terminal infrared light emitting / receiving unit 9, 10... Control station infrared light emitting / receiving unit 12, 12a, 13, 13a... Interference filter 20. ·····concave lens
26: Light receiving surface
27 ... Normal direction
28 ...... Direction deviated from normal
29a, 29b ... (large) refraction / reflection mountain
30 ...... (Small) Refraction / Reflection Mountain

Claims (7)

A satellite-type full-duplex infrared LAN system that transmits and receives between an infrared emitting / receiving unit of a control station of an indoor centralized control station and each terminal infrared emitting / receiving unit connected to a plurality of indoor terminals using infrared rays. ,
The control station infrared light emitting / receiving unit is provided with a concave lens having a directivity characteristic that decreases the light receiving sensitivity from the normal direction of the light receiving surface and increases the light receiving sensitivity from the direction deviated from the normal line of the light receiving surface. And
The concave lens has two large refracting / reflective peaks on both sides of the normal line on the incident side cross section toward the light receiving surface, and the output side cross section is stepped and saw-shaped from the outside toward the normal line. A satellite-type full-duplex infrared LAN system characterized by having a large number of small refracting / reflective peaks having a shape. 2. The satellite-type full-duplex infrared LAN system according to claim 1 , wherein a control station transmission infrared wavelength of the control station infrared transmission / reception unit and a terminal transmission infrared wavelength of the terminal infrared transmission / reception unit are different from each other . The short wavelength is used for the control station transmission infrared wavelength of the control station infrared light emitting / receiving unit, and the long wavelength is used for the terminal transmission infrared wavelength of the terminal infrared light emitting / receiving unit. Satellite type full-duplex infrared LAN system. The satellite-type full-duplex infrared LAN system according to any one of claims 1 to 3, wherein an interference filter is provided in each of the control station infrared light emitting / receiving unit and the terminal infrared light emitting / receiving unit. The control station infrared light emitting / receiving unit is provided with an interference filter having a long wavelength transmission characteristic for reception, and the terminal infrared light emitting / receiving unit is provided with an interference filter having a short wavelength transmission characteristic for reception. The satellite-type full-duplex infrared LAN system according to any one of claims 1 to 4. The satellite-type full-duplex infrared LAN system according to any one of claims 1 to 5, wherein an interference filter having a transmission characteristic on a long wavelength side is disposed in the terminal infrared light emitting / receiving unit for transmission. . The satellite-type full-duplex infrared LAN system according to any one of claims 1 to 6, wherein a color filter is disposed in the control station infrared light emitting / receiving unit for reception .

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