JP6002955B2

JP6002955B2 - Reflective concentrator

Info

Publication number: JP6002955B2
Application number: JP2012096907A
Authority: JP
Inventors: 文孝村山; 裕之黒川; 悦司大村
Original assignee: Kyosemi Corp
Current assignee: Kyosemi Corp
Priority date: 2012-04-20
Filing date: 2012-04-20
Publication date: 2016-10-05
Anticipated expiration: 2032-04-20
Also published as: JP2013225586A

Description

本発明は、空間に照射された可視光又は赤外線を媒体として通信を行なう空間光通信用受光装置等に使用される反射集光型受光器に関し、詳しくは、凹面鏡の内側に受光素子を鏡面側に向けて配置し、凹面鏡からの反射光を受光素子が効率良く受光するようにした反射集光型受光器に関する。 The present invention relates to a reflection / condensing light receiver used in a light receiving device for spatial light communication that performs communication using visible light or infrared light irradiated to a space as a medium, and more specifically, a light receiving element is provided on the mirror side inside a concave mirror. It is related with the reflection condensing type | mold light receiver which it has arrange | positioned toward the surface and a light receiving element receives efficiently the reflected light from a concave mirror.

電波を通信媒体とした無線通信は、携帯電話網、無線ＬＡＮ、近距離無線通信など多くの分野で使用されている。しかし、電波を媒体として使用する無線通信は、人の近くで送受信を行なう場合、電磁波の人体への影響を考慮して、送信電力を上げることができない。 Wireless communication using radio waves as a communication medium is used in many fields such as a cellular phone network, a wireless LAN, and short-range wireless communication. However, in wireless communication using radio waves as a medium, when transmission / reception is performed near a person, the transmission power cannot be increased in consideration of the influence of electromagnetic waves on the human body.

また、無線通信に使用される電波の周波数帯域は、既に多くの使用分野において割り振られ、使用されていることもあって、広帯域の周波数帯を自由に使用することはできない。さらに、病院などの特殊な環境下においては、電波の使用に制限が加えられるなどの制約がある。 In addition, the frequency band of radio waves used for wireless communication has already been allocated and used in many fields of use, and a wide frequency band cannot be freely used. Furthermore, there are restrictions such as restrictions on the use of radio waves in special environments such as hospitals.

そこで、近年、可視光や赤外線を通信媒体として用いる空間光通信の開発が進み、各種の空間光通信システムが提案されている。 Therefore, in recent years, development of spatial optical communication using visible light or infrared rays as a communication medium has progressed, and various spatial optical communication systems have been proposed.

特開平１０−３２２２７６号公報Japanese Patent Laid-Open No. 10-322276 特開２００９−３０２５１９号公報JP 2009-302519 A

この種の従来の空間光通信システムでは、通常、受信器側の受光器は、集光レンズを含む光学系と受光素子とから構成され、送信器側の投光器から投光された光を光学系で集光し、受光素子に当て、受光信号を出力するようにしている。特に、送信器と受信器の相対的な位置が移動する空間光通信装置においては、送信器の投光器から照射された光が受信器の受光器に到達する光量が低い場合を考慮して光の集光率を上げるために、集光レンズを含む光学系を大型とする必要があり、受光器の形状が比較的大型化し、特に集光レンズを用いた場合、受光器の厚さ寸法が長くなり、小型化が難しいという問題があった。 In this type of conventional spatial light communication system, the light receiver on the receiver side is usually composed of an optical system including a condenser lens and a light receiving element, and the light projected from the light projector on the transmitter side is the optical system. The light is condensed and applied to the light receiving element, and a light reception signal is output. In particular, in a spatial light communication device in which the relative positions of a transmitter and a receiver move, considering the case where the amount of light radiated from the transmitter of the transmitter reaches the light receiver of the receiver is low, In order to increase the light collection rate, it is necessary to make the optical system including the condensing lens large, and the shape of the photoreceiver becomes relatively large. Especially when the condensing lens is used, the thickness of the photoreceiver is long. Therefore, there was a problem that miniaturization was difficult.

一方、リフレクタレンズを受光素子の受光路に配置して、受光器の厚さ寸法を短くした空間光通信用の受光器が、上記特許文献１などで提案されている。しかし、この反射集光型の受光器は、リフレクタレンズ内に、凸面鏡と凹面鏡を配置して光学系を構成し、そのリフレクタレンズの背後に受光素子を配置する構成のため、やはり光学系が大型化する問題があった。 On the other hand, a light receiver for spatial light communication in which a reflector lens is disposed in a light receiving path of a light receiving element and a thickness dimension of the light receiver is shortened is proposed in Patent Document 1 and the like. However, this reflection-condensing type light receiver has a configuration in which a convex mirror and a concave mirror are arranged in a reflector lens to constitute an optical system, and a light receiving element is arranged behind the reflector lens, so that the optical system is still large. There was a problem.

そこで、本発明者らは、凹面鏡と、凹面鏡の内側の略中央に配設した受光素子とを有する反射集光型受光器の研究開発を行う間、その成果として、受光素子の受光面を凹面鏡の鏡面に向けて配置し、凹面鏡で反射された光を受光素子に入射するようにした反射集光型受光器を、上記特許文献２において提案した。 Accordingly, while conducting research and development of a reflective condensing type light receiving device having a concave mirror and a light receiving element disposed substantially in the center of the concave mirror, the present inventors have developed the light receiving surface of the light receiving element as a concave mirror. In Japanese Patent Application Laid-Open No. 2004-259542, a reflection condensing type light receiver is proposed which is arranged toward the mirror surface of the light source and is configured such that light reflected by the concave mirror is incident on the light receiving element.

この反射集光型受光器は、図７のように、受光素子９を凹面鏡８の内側に配置し、受光素子９の受光面を鏡面側に向け、受光素子９の１対の電極リード線１１，１２を中央部から両側に開くように延設して構成され、凹面鏡８のみを光学系に使用するので、小型化が可能となり、従来の受光器に比べ受光効率も向上させることができる。しかし、主に直射日光などの強力な光の集光による受光素子９の破損を防止するために、図８に示すように、受光素子９の受光面を、凹面鏡８（放物面鏡）の焦点位置から鏡面側にずらし、凹面鏡８の内側に受光素子９を配置している。 As shown in FIG. 7, the reflection / condensing light receiver has the light receiving element 9 disposed inside the concave mirror 8, the light receiving surface of the light receiving element 9 faces the mirror surface, and a pair of electrode lead wires 11 of the light receiving element 9. , 12 are extended from the center so as to open on both sides, and only the concave mirror 8 is used in the optical system, so that the size can be reduced and the light receiving efficiency can be improved as compared with the conventional light receiver. However, in order to prevent damage to the light receiving element 9 due mainly to the collection of strong light such as direct sunlight, the light receiving surface of the light receiving element 9 is made of a concave mirror 8 (parabolic mirror) as shown in FIG. The light receiving element 9 is arranged inside the concave mirror 8 by shifting from the focal position to the mirror side.

つまり、この反射集光型受光器は、図８に示す如く、凹面鏡８の焦点Ｆが、凹面鏡８の中心軸線Ｌ上にあって、凹面鏡８の中心位置から前方に焦点距離ｆの距離に位置する構成であるが、受光素子９は、その焦点Ｆから所定距離ｈ（例えば、約ｆ／１０）だけ、内側に（凹面鏡８の中心軸線上の鏡面側に）ずらした位置に配置している。 In other words, as shown in FIG. 8, this reflective condensing type light receiver has the focal point F of the concave mirror 8 on the central axis L of the concave mirror 8 and is located at a focal distance f forward from the center position of the concave mirror 8. However, the light receiving element 9 is arranged at a position shifted from the focal point F by a predetermined distance h (for example, about f / 10) inwardly (to the mirror surface on the central axis of the concave mirror 8). .

そこで、反射集光型受光器の性能実験及び受光状態のシミュレーション試験を実施したところ、図８及び図９の光線跡に示す如く、凹面鏡８の中心部近傍で反射された光は受光素子９の受光面（凹面鏡側を向く面）に到達するものの、凹面鏡８の周縁部近傍で反射された光は受光素子の受光面から外れ、受光面に到達していないことが判明した。 Therefore, when a performance experiment and a simulation test of the light receiving state of the reflection / condensing light receiver were performed, the light reflected in the vicinity of the central portion of the concave mirror 8 is reflected by the light receiving element 9 as shown in the ray traces of FIGS. Although it reached the light receiving surface (the surface facing the concave mirror side), it was found that the light reflected near the periphery of the concave mirror 8 deviated from the light receiving surface of the light receiving element and did not reach the light receiving surface.

つまり、図９Ａは、反射集光型受光器の凹面鏡の焦点Ｆ位置に受光素子９を配置し、正面から平行光線を入射させたとき、受光素子９に到達する光線跡Ｌ１を示し、図９Ｂは、同じ条件で受光素子９を焦点Ｆから凹面鏡８の鏡面側に偏位させて配置したとき、受光素子９に到達する光線跡Ｌ２を示している。円形の光線跡Ｌ１，Ｌ２内の中央の矩形部分Ｋは受光素子の影である。 That is, FIG. 9A shows a ray trace L1 that reaches the light receiving element 9 when the light receiving element 9 is arranged at the focal point F position of the concave mirror of the reflective condensing type light receiver and a parallel light beam is incident from the front. These show the light trace L2 that reaches the light receiving element 9 when the light receiving element 9 is deviated from the focal point F to the mirror surface side of the concave mirror 8 under the same conditions. A central rectangular portion K in the circular ray traces L1 and L2 is a shadow of the light receiving element.

図８のように反射集光型受光器が凹面鏡８を介して正面から平行光線を受光した場合、受光素子９をその焦点Ｆから鏡面側にずらして配置したとき、図９Ｂに示すように、凹面鏡の広い領域Ｃ（光線跡Ｌ２の外側の部分）において受光素子９の受光面に到達しない領域が広く存在する。つまり、受光素子９を凹面鏡８の焦点Ｆから鏡面側に偏位させて配置したとき、受光素子９の受光面に到達する空間光は、凹面鏡全体ではなく、図８の凹面領域Ａ１（凹面鏡の中央部）の鏡面で反射された反射光に限定され、その周縁部の凹面領域Ａ２からの反射光は受光素子９に到達していない。この現象は、受光素子９をその焦点Ｆから反鏡面側にずらして配置したときも、同様である。 As shown in FIG. 9B, when the reflective condensing type light receiver receives parallel rays from the front via the concave mirror 8 as shown in FIG. 8, when the light receiving element 9 is shifted from the focal point F to the mirror side, as shown in FIG. There is a wide area that does not reach the light receiving surface of the light receiving element 9 in the wide area C of the concave mirror (portion outside the ray trace L2). That is, when the light receiving element 9 is arranged to be deviated from the focal point F of the concave mirror 8 to the mirror surface side, the spatial light reaching the light receiving surface of the light receiving element 9 is not the entire concave mirror, but the concave area A1 in FIG. The reflected light is limited to the reflected light reflected by the mirror surface of the central portion, and the reflected light from the concave surface area A <b> 2 at the peripheral edge does not reach the light receiving element 9. This phenomenon is the same when the light receiving element 9 is shifted from the focal point F to the side opposite to the mirror surface.

このため、受光素子９をその焦点Ｆからずらして配置したときには、凹面鏡８の中央部の凹面領域Ａ１の反射光のみが使用され、凹面鏡８の大きな面積を占める周縁部近傍の凹面領域Ａ２が使用されていないことから、受光素子９が受光する空間光の受光効率が低くなり、受光素子９の光電変換効率を高くできないという課題があった。 For this reason, when the light receiving element 9 is shifted from the focal point F, only the reflected light of the concave surface area A1 in the center of the concave mirror 8 is used, and the concave surface area A2 in the vicinity of the peripheral portion occupying a large area of the concave mirror 8 is used. Therefore, there is a problem that the light receiving efficiency of the spatial light received by the light receiving element 9 is lowered, and the photoelectric conversion efficiency of the light receiving element 9 cannot be increased.

本発明は、上記の点に鑑みなされたもので、小型化が可能で、直射日光などの強力な光の集光による受光素子の破損を防止しつつ、受光素子の受光・光電変換効率を向上させることができる反射集光型受光器を提供することを目的とする。 The present invention has been made in view of the above points, and can be miniaturized, improving the light receiving / photoelectric conversion efficiency of the light receiving element while preventing the light receiving element from being damaged by the collection of strong light such as direct sunlight. It is an object of the present invention to provide a reflective condensing light receiver that can be made to operate.

上記目的を達成するために、本発明の反射集光型受光器は、情報信号を重畳した空間光を、焦点を有する凹面鏡を介し反射集光して受光する、受光素子を有した反射集光型受光器において、
該凹面鏡は、中心の法線である中心軸線上に焦点を有する正規凹面鏡の、一部を切り取った部分凹面鏡として形成され、該受光素子は、該焦点を通る該中心軸線上に、その受光面を該部分凹面鏡の鏡面側に向けて配置され、
該部分凹面鏡は、該正規凹面鏡の該焦点を通る該中心軸線を、一方の縁部寄りに偏位させた位置で、該正規凹面鏡の一部を切り取った形状に形成され、
前記受光素子の１対の電極リードが、該部分凹面鏡の外殻を形成する直方体状の凹面鏡本体の反凹面側の底部から、該部分凹面鏡の上部に位置する該受光素子まで、該凹面鏡本体の両側の側壁に沿って配設され、一方の該電極リードが該受光素子の近傍の側壁を経て該受光素子に接続され、他方の該電極リードが該部分凹面鏡の周縁部内側を経てまたは該凹面鏡本体の壁部上を経て該受光素子に接続されたことを特徴とする。
In order to achieve the above object, a reflection / condensing light receiver according to the present invention reflects and collects spatial light on which an information signal is superimposed through a concave mirror having a focal point and receives the light. Type receiver
The concave mirror is formed as a partially concave mirror of a normal concave mirror having a focal point on a central axis that is a normal line of the center, and the light receiving element has its light receiving surface on the central axis passing through the focal point. Arranged toward the mirror side of the partially concave mirror,
The partial concave mirror is formed in a shape in which a part of the regular concave mirror is cut off at a position where the central axis passing through the focal point of the regular concave mirror is deviated toward one edge ,
A pair of electrode leads of the light receiving element is formed on the concave mirror body from the bottom of the concave concave mirror body forming the outer shell of the partial concave mirror to the light receiving element positioned above the partial concave mirror. One electrode lead is connected to the light receiving element through a side wall in the vicinity of the light receiving element, and the other electrode lead is connected to the inner side of the peripheral part of the partial concave mirror or the concave mirror. It is connected to the light receiving element through the wall of the main body.

ここで、上記正規凹面鏡とは、放物線などＸＹ座標上の曲線を、Ｙ軸（中心軸線）の回りで回転させたときに生じる凹面を、鏡面とする凹面鏡を意味する。また、上記焦点は、凹面鏡に入射した平行光線の反射光が集中する点である、正確な意味の焦点のほか、概略的な焦点、つまりある程度の面積を有する焦点位置を、凹面鏡に入射する平行光線の反射光が通過し、ピントのずれを生じさせるような、概略焦点を含む意味である。 Here, the regular concave mirror means a concave mirror whose mirror surface is a concave surface generated when a curve on an XY coordinate such as a parabola is rotated around the Y axis (center axis). The focal point is a point where the reflected light of the parallel rays incident on the concave mirror is concentrated. In addition to an accurate focal point, a rough focal point, that is, a parallel focal point having a certain area is incident on the concave mirror. This means that it includes a general focal point through which reflected light of the light beam passes and causes a defocus.

この発明によれば、凹面鏡が正規凹面鏡の一部を切り取った部分凹面鏡として形成されるため、正規凹面鏡を使用する受光器に比べ、より小型化することができる。 According to the present invention, since the concave mirror is formed as a partial concave mirror obtained by cutting out a part of the regular concave mirror, the size can be further reduced as compared with a light receiver using the regular concave mirror.

また、直射日光などの強力な光の集光による受光素子の破損を防止するために、受光素子が中心軸線上で焦点位置から鏡面側に或いは反鏡面側にずらして配置された場合であっても、部分凹面鏡は、その殆どの鏡面領域で反射する反射光を受光素子の受光面に入射させるため、受光素子の受光効率を向上させ、光電変換効率を向上させることができる。 In addition, in order to prevent damage to the light receiving element due to the condensing of strong light such as direct sunlight, the light receiving element is shifted from the focal position to the mirror surface side or the anti-mirror surface side on the central axis. However, since the partially concave mirror makes the reflected light reflected by most of the mirror region enter the light receiving surface of the light receiving element, the light receiving efficiency of the light receiving element can be improved and the photoelectric conversion efficiency can be improved.

また、正規凹面鏡の焦点位置に受光素子が配置される場合でも、部分凹面鏡の鏡面の大きさは正規凹面鏡に比して小さく、反射光の光量は正規凹面鏡に比べ限定され、直射日光などの強力な光の集光による受光素子の破損を防止することができる。 Even when the light receiving element is placed at the focal position of the regular concave mirror, the size of the mirror surface of the partial concave mirror is smaller than that of the regular concave mirror, and the amount of reflected light is limited compared to the regular concave mirror. It is possible to prevent the light receiving element from being damaged by the concentrated light.

本発明の反射集光型受光器によれば、小型化が可能であり、直射日光などの強力な光の集光による受光素子の破損を防止し、受光素子の受光・光電変換効率を向上させることができる。 According to the reflective condensing type photoreceiver of the present invention, it is possible to reduce the size, prevent damage to the light receiving element due to the collection of strong light such as direct sunlight, and improve the light receiving / photoelectric conversion efficiency of the light receiving element. be able to.

本発明の一実施形態を示す反射集光型受光器の拡大斜視図である。It is an expansion perspective view of the reflective condensing type light receiver which shows one Embodiment of this invention. 同反射集光型受光器の平面図である。It is a top view of the reflection condensing type light receiver. 図１のIII−III断面図である。FIG. 3 is a sectional view taken along line III-III in FIG. 1. 同反射集光型受光器の半断面斜視図である。It is a half section perspective view of the same reflective condensing type light receiver. 反射集光型受光器に平行光線を入射させたときの、反射光の状態を示す説明断面図である。It is explanatory sectional drawing which shows the state of reflected light when a parallel ray is entered into a reflective condensing type light receiver. 正規凹面鏡の断面説明図である。It is a section explanatory view of a regular concave mirror. 従来の反射集光型受光器の拡大斜視図である。It is an expansion perspective view of the conventional reflective condensing type light receiver. 同反射集光型受光器の断面図である。It is sectional drawing of the same reflective condensing type light receiver. 凹面鏡に平行光線を入射させたときの、受光素子に到達する光束のシミュレーション図を示し、（Ａ）は従来の反射集光型受光器の凹面鏡の焦点位置に受光素子を配した場合、（Ｂ）は受光素子を焦点位置から鏡面側にオフセットした場合である。The simulation figure of the light beam which reaches | attains a light receiving element when a parallel ray is made to enter a concave mirror is shown, (A) shows the case where a light receiving element is arranged at the focal position of the concave mirror of a conventional reflection-condensing type light receiver. ) Is a case where the light receiving element is offset from the focal position to the mirror surface side. （Ａ）（Ｂ）は受光素子を焦点から偏位して部分凹面鏡を切り取った位置を示す光束シミュレーション説明図である。(A) (B) is light beam simulation explanatory drawing which shows the position which shifted the light receiving element from the focus and cut off the partial concave mirror.

以下、本発明の実施形態を図面に基づいて説明する。この反射集光型受光器は、送信器等から投光照射された空間光を、部分凹面鏡２を介し反射集光し、受光素子３により受光する受光器であり、部分凹面鏡２の内側の縁部近傍に、つまり中央部から縁部に偏位した位置に、受光素子３がその受光面３ａを部分凹面鏡２の鏡面側に向けて配置されて構成される。部分凹面鏡２は、直方体状に形成された凹面鏡本体１内に形成されている。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. This reflection / condensing light receiver is a light receiver that reflects and collects spatial light emitted from a transmitter or the like via a partial concave mirror 2 and receives the light by a light receiving element 3. The light receiving element 3 is arranged in the vicinity of the portion, that is, at a position deviated from the center portion to the edge portion with the light receiving surface 3a facing the mirror surface side of the partial concave mirror 2. The partial concave mirror 2 is formed in a concave mirror main body 1 formed in a rectangular parallelepiped shape.

受光素子３の１対の電極リード４，５は、凹面鏡本体１の底部から両側の側壁に沿って配設され、カソード用の電極リード４は受光素子３の近傍の側壁を経て受光素子３のカソードに接続される。アノード用の電極リード５は部分凹面鏡２の周縁部近傍の壁部に沿って配設され、受光素子３のアノードに接続される。つまり、受光素子３を平面から見た場合、受光素子３の両電極に接続された１対の電極リード４，５は、部分凹面鏡２の前面から開くように延設され、凹面鏡本体１の両側の外壁面を底部まで下り、図示しない回路基板の受光回路に接続されるようになっている。 A pair of electrode leads 4, 5 of the light receiving element 3 are disposed along the side walls on both sides from the bottom of the concave mirror body 1, and the cathode electrode lead 4 passes through the side wall in the vicinity of the light receiving element 3. Connected to the cathode. The anode electrode lead 5 is disposed along the wall near the peripheral edge of the partial concave mirror 2 and is connected to the anode of the light receiving element 3. That is, when the light receiving element 3 is viewed from a plane, the pair of electrode leads 4 and 5 connected to both electrodes of the light receiving element 3 are extended so as to open from the front surface of the partial concave mirror 2, The outer wall surface is lowered to the bottom, and is connected to a light receiving circuit of a circuit board (not shown).

なお、上記とは逆に、１対の電極リード４，５は、アノード用の電極リードを受光素子３の近傍の側壁を経て受光素子３のアノードに接続し、カソード用の電極リードを部分凹面鏡２の周縁部近傍の壁部に沿って配設し、受光素子３のカソードに接続してもよい。 Contrary to the above, in the pair of electrode leads 4 and 5, the anode electrode lead is connected to the anode of the light receiving element 3 through the side wall near the light receiving element 3, and the cathode electrode lead is connected to the partial concave mirror. 2 may be disposed along the wall portion in the vicinity of the peripheral edge portion 2 and connected to the cathode of the light receiving element 3.

部分凹面鏡２は、図６に示すように、正規凹面鏡２０の一部（直方体部分Ｂ２の箇所）を切り取った形状に形成される。正規凹面鏡２０は、図６のように、中心軸線Ｌ上にその焦点Ｆを有する放物面鏡であり、ＸＹ座標上の放物線を、Ｙ軸（中心軸線Ｌ）の回りで回転させたときに生じる凹面を、鏡面とする放物凹面鏡である。なお、正規凹面鏡２０は、必ずしも正確な放物面鏡でなくてもよく、円弧を中心軸線の回りで回転させて形成した球面凹面鏡、或いは楕円孤を中心軸線の回りで回転させて形成した楕円凹面鏡とすることもできる。 As shown in FIG. 6, the partial concave mirror 2 is formed in a shape obtained by cutting off a part of the regular concave mirror 20 (a portion of the rectangular parallelepiped portion B <b> 2). The regular concave mirror 20 is a parabolic mirror having a focal point F on the central axis L as shown in FIG. 6, and when the parabola on the XY coordinates is rotated around the Y axis (the central axis L). This is a parabolic concave mirror having a concave surface as a mirror surface. The regular concave mirror 20 is not necessarily an accurate parabolic mirror, and is a spherical concave mirror formed by rotating an arc around the central axis, or an ellipse formed by rotating an elliptical arc around the central axis. It can also be a concave mirror.

部分凹面鏡２は、正規凹面鏡２０の一部を切り取った形状、例えば図６に示すように、正規凹面鏡の中心部を部分凹面鏡の縁部近傍に偏位させた位置の直方体部分Ｂ２を切り取った形状に形成されている。この正規凹面鏡２０の一部を切り取った直方体部分Ｂ２を平面的に示すと、上記で説明したシミュレーション試験時の光線跡Ｌ２を示した図９Ｂに示すように、受光素子を凹面鏡の焦点Ｆの位置から鏡面側にずらして配置した正規凹面鏡において、焦点Ｆの位置する中央軸線を凹面鏡の縁部近傍に偏位させた形状の直方体状に部分凹面鏡２は形成されている。つまり、平面的には、図９Ｂのように、受光素子３の受光面３ａを正規凹面鏡２０の焦点Ｆから鏡面側にずらした状態で、その受光素子３を一辺の縁部に含む長方形で、部分凹面鏡２は切り取られた直方体部分Ｂ２の形状に形成される。これにより、図９Ｂの如く、直方体部分Ｂ２で入射し鏡面で反射された光線跡Ｌ２の殆どが受光素子に到達するため、部分凹面鏡２は、その鏡面で反射した反射光の殆ど全てが、受光素子３に入射することとなる。 The partial concave mirror 2 has a shape obtained by cutting a part of the regular concave mirror 20, for example, a shape obtained by cutting a rectangular parallelepiped portion B2 at a position where the center of the regular concave mirror is displaced near the edge of the partial concave mirror as shown in FIG. Is formed. When the rectangular parallelepiped portion B2 obtained by cutting a part of the regular concave mirror 20 is shown in plan, the light receiving element is positioned at the focal point F of the concave mirror as shown in FIG. 9B showing the ray trace L2 in the simulation test described above. The partial concave mirror 2 is formed in a rectangular parallelepiped shape in which the central axis where the focal point F is located is displaced near the edge of the concave mirror. That is, in a plan view, as shown in FIG. 9B, in a state where the light receiving surface 3a of the light receiving element 3 is shifted from the focal point F of the regular concave mirror 20 to the mirror surface side, the light receiving element 3 is a rectangle including the edge of one side, The partial concave mirror 2 is formed in the shape of a cut rectangular parallelepiped portion B2. As a result, as shown in FIG. 9B, most of the light trace L2 incident on the rectangular parallelepiped portion B2 and reflected by the mirror surface reaches the light receiving element. The light enters the element 3.

このように、受光素子３の受光面３ａを、正規凹面鏡２０の焦点Ｆから鏡面側にずらした状態であっても、図９Ｂの如く、部分凹面鏡２が直方体部分Ｂ２で切り取って形成されることにより、鏡面で反射した空間光の殆どを、受光素子９の受光面に到達させるようになっている。よって、図８における凹面領域Ａ３を使用し、周縁部の凹面領域Ａ２を使用しないため、反射光が受光素子９の受光面に到達しない領域は凹面鏡には殆どなくなり、部分凹面鏡２の鏡面で反射された反射光の殆ど全てが、受光素子３の受光面に入射することとなる。 In this way, even when the light receiving surface 3a of the light receiving element 3 is shifted from the focal point F of the regular concave mirror 20 to the mirror surface side, the partial concave mirror 2 is formed by cutting the rectangular parallelepiped portion B2 as shown in FIG. 9B. Thus, most of the spatial light reflected by the mirror surface reaches the light receiving surface of the light receiving element 9. Therefore, since the concave surface area A3 in FIG. 8 is used and the concave surface area A2 at the peripheral portion is not used, the area where the reflected light does not reach the light receiving surface of the light receiving element 9 is almost eliminated by the concave mirror and reflected by the mirror surface of the partial concave mirror 2 Almost all of the reflected light is incident on the light receiving surface of the light receiving element 3.

また、上記のように受光器の凹面鏡を部分凹面鏡２とすることは、製造上でのメリットが非常に大きい。つまり、反射集光型受光器を小型化する場合、凹面鏡自体をそのまま小型化することもできるが、この種の反射集光型受光器で使用される凹面鏡は、例えば一辺を約３．４ｍｍとするように、非常に小さく、このような小形の凹面鏡を高い精度で正確に製造することは容易ではない。そこで、本発明では、正規凹面鏡２０の一部を切り取って部分凹面鏡２として使用するようにしており、正規凹面鏡２０は部分凹面鏡２に比べれば大形であり、精度の高い凹面鏡を比較的容易に製造することができる。 Further, as described above, the use of the concave mirror of the light receiver as the partial concave mirror 2 has a great advantage in manufacturing. That is, in the case of downsizing the reflection-condensing light receiver, the concave mirror itself can be downsized as it is, but the concave mirror used in this type of reflection-condensing light-receiving device has, for example, a side of about 3.4 mm. Thus, it is very difficult to manufacture such a small concave mirror accurately with high accuracy. Therefore, in the present invention, a part of the regular concave mirror 20 is cut out and used as the partial concave mirror 2, and the regular concave mirror 20 is larger than the partial concave mirror 2, and a highly accurate concave mirror is relatively easy. Can be manufactured.

部分凹面鏡２の外殻を形成する凹面鏡本体１は、図１〜３のように、合成樹脂により略直方体の箱状に形成され、凹面鏡本体１の内側に、上記のような部分凹面鏡２が形成される。部分凹面鏡２は、放物面に、反射用の銀、アルミニウムなどの金属膜をめっき或いは蒸着して形成され、部分放物面鏡が形成されている。図６に示すように、正規凹面鏡２０の一部を切り取った部分凹面鏡２の焦点Ｆは、一方の縁部寄りに偏位して位置する放物面鏡の中心軸線Ｌ上に位置し、受光素子３が、その受光面３ａをその中心軸線Ｌ上で焦点Ｆから鏡面側に僅かにずらした位置に配置される。つまり、図５に示すように、受光素子３の受光面３ａから鏡面まで下ろした垂線の長さは、部分凹面鏡２の焦点距離ｆより僅かに短くなっている。 The concave mirror main body 1 that forms the outer shell of the partial concave mirror 2 is formed in a substantially rectangular parallelepiped box shape with synthetic resin as shown in FIGS. 1 to 3, and the partial concave mirror 2 as described above is formed inside the concave mirror main body 1. Is done. The partial concave mirror 2 is formed by plating or vapor-depositing a metal film such as silver or aluminum for reflection on a parabolic surface, thereby forming a partial parabolic mirror. As shown in FIG. 6, the focal point F of the partial concave mirror 2 obtained by cutting a part of the regular concave mirror 20 is located on the central axis L of the parabolic mirror located so as to be deviated closer to one edge portion. The element 3 is disposed at a position where the light receiving surface 3a is slightly shifted from the focal point F to the mirror surface side on the central axis L. That is, as shown in FIG. 5, the length of the perpendicular line from the light receiving surface 3 a of the light receiving element 3 to the mirror surface is slightly shorter than the focal length f of the partially concave mirror 2.

凹面鏡本体１の小型化に加え、部分凹面鏡２の焦点距離ｆは、例えば２ｍｍと非常に短く設定され、部分凹面鏡２の一辺の長さも、例えば３．４ｍｍと非常に短く形成される。受光素子３の受光面３ａの一辺は、例えば約０．５ｍｍである。これにより、本発明の反射集光型受光器は、非常に小型化することができる。 In addition to downsizing of the concave mirror body 1, the focal length f of the partial concave mirror 2 is set to be very short, for example, 2 mm, and the length of one side of the partial concave mirror 2 is also formed to be very short, for example, 3.4 mm. One side of the light receiving surface 3a of the light receiving element 3 is, for example, about 0.5 mm. Thereby, the reflective condensing type light receiver of the present invention can be very miniaturized.

凹面鏡本体１は、例えば熱可塑性樹脂などの合成樹脂（例えば、ＰＥＥＫ樹脂、ＰＰＳ樹脂）により直方体状に成形され、凹面鏡本体１内に部分凹面鏡２が形成される。部分凹面鏡２は、上述のように、一辺の縁部近傍に、中心軸線Ｌを位置させるように、正規凹面鏡の中央部から偏位した位置に形成される（図５）。また、受光素子３はその受光面３ａを、その中心軸線Ｌ上の焦点Ｆから鏡面側に僅かにずらした位置に位置させ、部分凹面鏡２の鏡面側に向けて配置される。 The concave mirror body 1 is formed into a rectangular parallelepiped shape with a synthetic resin such as a thermoplastic resin (for example, PEEK resin or PPS resin), and a partial concave mirror 2 is formed in the concave mirror body 1. As described above, the partial concave mirror 2 is formed at a position displaced from the central portion of the regular concave mirror so that the central axis L is positioned in the vicinity of the edge of one side (FIG. 5). In addition, the light receiving element 3 is arranged with its light receiving surface 3a positioned slightly shifted from the focal point F on the central axis L to the mirror surface side and facing the mirror surface side of the partially concave mirror 2.

受光素子３の１対の電極（アノード電極、カソード電極）には各々電極リード４，５が半田付け或いは導電性接着剤により接続され、両電極に接続される１対の電極リード４，５は、上述のように、部分凹面鏡２の両側の壁部に、底部から上部まで配設される。また、カソード側の電極リード４は短距離で受光素子３に接続され、アノード側の電極リード５は、凹面鏡本体１の側壁から上面の縁部に沿って延設され、その平面側から受光素子３の電極に接続されるように配設される。 Electrode leads 4 and 5 are respectively connected to a pair of electrodes (anode electrode and cathode electrode) of the light receiving element 3 by soldering or conductive adhesive, and the pair of electrode leads 4 and 5 connected to both electrodes are As described above, it is disposed from the bottom to the top on the wall portions on both sides of the partial concave mirror 2. The cathode-side electrode lead 4 is connected to the light-receiving element 3 at a short distance, and the anode-side electrode lead 5 extends from the side wall of the concave mirror body 1 along the edge of the upper surface, and from the plane side to the light-receiving element. 3 to be connected to the three electrodes.

なお、図１，２などに示すアノード側の電極リード５は、凹面鏡本体１の内側に配置されているが、凹面鏡本体１の壁部の縁部に沿って配置することもでき、その場合、凹面鏡本体１の内側ではなく外側となるので、部分凹面鏡２の有効開口面積を広くすることができる。また、カソード側の電極リード４とアノード側の電極リード５は、相互に逆の位置関係で配置することもできる。 In addition, although the electrode lead 5 on the anode side shown in FIGS. 1 and 2 is disposed inside the concave mirror body 1, it can also be disposed along the edge of the wall portion of the concave mirror body 1. Since it is not the inside of the concave mirror body 1 but the outside, the effective opening area of the partial concave mirror 2 can be increased. Further, the cathode-side electrode lead 4 and the anode-side electrode lead 5 can be disposed in a mutually opposite positional relationship.

また、このような電極リード４，５の端部は、凹面鏡本体１の底部両側に開くように位置しているため、反射集光型受光器を回路基板上に実装したとき、回路基板上の導電層に対し、電極リード４，５の端部をリフロー半田などにより、確実かつ正確に結合することができる。さらに、１対の電極リード４，５は、凹面鏡本体１の両側に開くように延設され、凹面鏡本体１の外側面を経て受光回路に接続されるため、１対の電極リード４，５と受光回路のプリアンプのグランド間に生じる静電容量は、単純に受光素子をプリアンプ等の入力側に接続した場合に比べ、大幅に減少させることができる。 In addition, since the ends of the electrode leads 4 and 5 are positioned so as to open on both sides of the bottom of the concave mirror body 1, when the reflective condensing type light receiver is mounted on the circuit board, The ends of the electrode leads 4 and 5 can be reliably and accurately coupled to the conductive layer by reflow soldering or the like. Further, since the pair of electrode leads 4 and 5 are extended so as to open on both sides of the concave mirror main body 1 and are connected to the light receiving circuit through the outer surface of the concave mirror main body 1, The capacitance generated between the grounds of the preamplifiers of the light receiving circuit can be greatly reduced as compared with the case where the light receiving element is simply connected to the input side of the preamplifier or the like.

凹面鏡本体１内（部分凹面鏡２内）の凹部６内には、受光素子３が、その受光面３ａの中心を、部分凹面鏡２の焦点位置より僅かに鏡面側にずらして位置させた状態で、凹部６内に透明合成樹脂（例えばエポキシ樹脂など）が充填される。この透明合成樹脂の充填により、受光素子３の反射面側の受光面３ａを透明合成樹脂で覆うようにし、これらを保護する。また、凹部６内の透明合成樹脂の充填により、部分凹面鏡２内の光の屈折率を調整して、部分凹面鏡２の焦点位置を任意に調整することができる。 In the concave portion 6 in the concave mirror body 1 (in the partial concave mirror 2), the light receiving element 3 is positioned with the center of the light receiving surface 3a slightly shifted from the focal position of the partial concave mirror 2 to the mirror surface side. The recess 6 is filled with a transparent synthetic resin (for example, an epoxy resin). By filling the transparent synthetic resin, the light receiving surface 3a on the reflection surface side of the light receiving element 3 is covered with the transparent synthetic resin to protect them. Moreover, the refractive position of the light in the partial concave mirror 2 can be adjusted by filling the transparent synthetic resin in the concave portion 6, and the focal position of the partial concave mirror 2 can be arbitrarily adjusted.

受光素子３には、例えばＳｉＡＰＤ（シリコンアバランシュフォトダイオード）を使用することができる。このＳｉＡＰＤの受光素子３は、逆バイアスを印加して光電流を増幅させ、高速の信号を高感度で受光することが可能であり、高いＳ／Ｎ比を得ることができる。受光する空間光としては、青色光、白色光などの可視光のほか、赤外線を使用することもでき、その場合、赤外線を高効率で受光するフォトダイオードが使用される。つまり、反射集光型受光器では、受光する空間光として白色光、青色光などの可視光を受光するが、赤外線（近赤外線）を使用することもできる。この場合、受光素子３として赤外線用フォトダイオードを使用することとなる。 For the light receiving element 3, for example, SiAPD (silicon avalanche photodiode) can be used. This light receiving element 3 of SiAPD can apply a reverse bias to amplify the photocurrent, receive a high-speed signal with high sensitivity, and obtain a high S / N ratio. In addition to visible light such as blue light and white light, infrared light can also be used as the spatial light to be received. In this case, a photodiode that receives infrared light with high efficiency is used. That is, in the reflection-condensing light receiver, visible light such as white light and blue light is received as received spatial light, but infrared light (near infrared light) can also be used. In this case, an infrared photodiode is used as the light receiving element 3.

また、受光素子３の受光面には、ＡＲコート（反射防止膜）を施すことが好ましい。ＡＲコートは、例えばフッ化マグネシウムを受光面３ａに真空蒸着して形成され、薄膜を透過して奥の面で反射する光と薄膜の透過光を干渉させて、受光面３ａからの反射を防止し、受光素子３の受光効率を向上させることができる。 Further, it is preferable to apply an AR coating (antireflection film) to the light receiving surface of the light receiving element 3. The AR coat is formed, for example, by vacuum-depositing magnesium fluoride on the light receiving surface 3a, and prevents light reflected from the light receiving surface 3a by interfering with the light transmitted through the thin film and reflected by the back surface and the transmitted light of the thin film. In addition, the light receiving efficiency of the light receiving element 3 can be improved.

上記構成の反射集光型受光器は、図５に示すように、部分凹面鏡２の前方から平行光線を受光した場合、部分凹面鏡２の鏡面で反射される光は、部分凹面鏡２の焦点Ｆに集光し、受光素子３の受光面３ａに入射する。 As shown in FIG. 5, when the reflection / condensing light receiver having the above configuration receives parallel light rays from the front of the partial concave mirror 2, the light reflected by the mirror surface of the partial concave mirror 2 is focused on the focal point F of the partial concave mirror 2. The light is condensed and incident on the light receiving surface 3 a of the light receiving element 3.

部分凹面鏡２は、正規凹面鏡２０の一部を、図９Ｂに示す直方体部分Ｂ２（反射光が受光素子３に到達する部分）で切り取って形成されているので、鏡面で反射される光の殆どが受光素子３の受光面３ａに入射し、小型の凹面鏡に拘わらず、受光効率を高くすることができる。勿論、部分凹面鏡２の反射集光型受光器は、正規凹面鏡を備える従来の反射集光型受光器に比して、大幅に小型化することができる。さらに、受光素子３の受光面３ａは、部分凹面鏡２の焦点Ｆから鏡面側に僅かにずらして配置されるので、直射日光などの強力な光が入射した場合でも、受光素子３の受光面３ａ上で集光することがなく、受光素子３の焼損（破損）は防止することができる。 Since the partial concave mirror 2 is formed by cutting a part of the regular concave mirror 20 at a rectangular parallelepiped portion B2 (a portion where the reflected light reaches the light receiving element 3) shown in FIG. 9B, most of the light reflected by the mirror surface is formed. Light is incident on the light receiving surface 3a of the light receiving element 3, and the light receiving efficiency can be increased regardless of a small concave mirror. Of course, the reflection / condensing light receiver of the partial concave mirror 2 can be significantly reduced in size as compared with a conventional reflection / condensing light receiver including a regular concave mirror. Further, since the light receiving surface 3a of the light receiving element 3 is arranged slightly shifted from the focal point F of the partial concave mirror 2 toward the mirror surface side, even when strong light such as direct sunlight enters, the light receiving surface 3a of the light receiving element 3 The light is not condensed above, and the light receiving element 3 can be prevented from being burned (damaged).

さらに、凹面鏡を部分凹面鏡２として小型化した場合、必然的に受光素子３に接続される電極リードの影の面積が、部分凹面鏡２の平面の面積に対し相対的に増大し、その影による受光効率の低下が無視できなくなるが、上記実施形態の受光器では、部分凹面鏡２の縁部近傍に受光素子３が中心部から偏位して配置されるので、一方の電極リード４の影が殆ど入らず、影による受光効率の低下を防止することができる。 Further, when the concave mirror is miniaturized as the partial concave mirror 2, the area of the shadow of the electrode lead inevitably connected to the light receiving element 3 increases relative to the area of the plane of the partial concave mirror 2, and light reception by the shadow is received. Although the reduction in efficiency cannot be ignored, in the light receiver of the above-described embodiment, the light receiving element 3 is arranged near the edge of the partial concave mirror 2 so as to be displaced from the center, so that the shadow of one of the electrode leads 4 is almost absent. It is possible to prevent a decrease in light receiving efficiency due to shadows.

なお、図面では、アノード側の電極リード５が部分凹面鏡２の内側に入って配設されるが、上述のように、アノード側の電極リード５を凹面鏡本体１の縁部上で縁部に沿って配設すれば、アノード側の電極リード５の影による受光効率の低下を防止することができる。 In the drawing, the anode-side electrode lead 5 is disposed inside the partial concave mirror 2. However, as described above, the anode-side electrode lead 5 is disposed on the edge of the concave mirror body 1 along the edge. If it is arranged, it is possible to prevent a decrease in light receiving efficiency due to the shadow of the electrode lead 5 on the anode side.

また、上記実施形態では、受光素子３の受光面３ａを凹面鏡の焦点Ｆから鏡面側にずらして配置したが、凹面鏡の中心軸線Ｌ上であれば、受光素子３の受光面３ａを、反鏡面側にずらして配置することもでき、或いは受光素子３の受光面３ａを焦点Ｆに配置することもできる。受光素子３の受光面３ａを焦点Ｆに配置した場合、部分凹面鏡２の鏡面からの反射光は殆どが受光素子３に入射することとなるが、部分凹面鏡２の鏡面の広さは正規凹面鏡より小さく限定されるので、直射日光などの強力な光の入射による、受光素子３の焼損（破損）を防止しつつ、受光素子３の受光効率を高めることができる。 Moreover, in the said embodiment, although the light-receiving surface 3a of the light receiving element 3 was shifted and arrange | positioned from the focus F of a concave mirror to the mirror surface side, if it is on the central axis L of a concave mirror, the light-receiving surface 3a of the light receiving element 3 will be anti-mirror surface. The light receiving surface 3a of the light receiving element 3 can also be disposed at the focal point F. When the light receiving surface 3a of the light receiving element 3 is arranged at the focal point F, most of the reflected light from the mirror surface of the partial concave mirror 2 is incident on the light receiving element 3, but the size of the mirror surface of the partial concave mirror 2 is larger than that of a regular concave mirror. Since it is limited to a small size, it is possible to increase the light receiving efficiency of the light receiving element 3 while preventing the light receiving element 3 from being burned (damaged) due to the incidence of strong light such as direct sunlight.

また、上記部分凹面鏡２は、平面的に、正規凹面鏡の焦点位置を、凹面鏡本体１の縁部近傍に偏位して位置させながら、正規凹面鏡の一部を方形状に切り取るように形成したが、図１０Ａの直方体部分Ｂ３のように、その焦点位置を部分凹面鏡の略中央に配置させて、正規凹面鏡の一部を直方体形状に切り取るように部分凹面鏡を形成することもできる。この場合、電極リードの長さは上記のものより長くなるが、電極リードの細径化により、電極リードの影の影響を少なくして受光効率を向上させつつ、受光器の小型化を図ることができる。 In addition, the partial concave mirror 2 is formed so as to cut out a part of the regular concave mirror in a square shape while the focal position of the regular concave mirror is displaced in the vicinity of the edge of the concave mirror body 1 in plan view. As shown in FIG. 10A, the partial concave mirror can be formed such that a focal position thereof is arranged at substantially the center of the partial concave mirror and a part of the regular concave mirror is cut into a rectangular parallelepiped shape. In this case, the length of the electrode lead is longer than the above, but by reducing the diameter of the electrode lead, the influence of the shadow of the electrode lead is reduced and the light receiving efficiency is improved, and the light receiver is reduced in size. Can do.

また、図１０Ｂの直方体部分Ｂ４のように、その焦点位置を部分凹面鏡の角部に配置させて、正規凹面鏡の一部を直方体形状に切り取るように部分凹面鏡を形成することもできる。この場合、図１０Ｂに示される光束の右下部分が部分凹面鏡から外れるが、焦点位置を部分凹面鏡の角部に配置させることにより、電極リードの影の影響をなくすことができるため、受光効率を向上させつつ、受光器の小型化を図ることができる。 Further, like the rectangular parallelepiped portion B4 in FIG. 10B, the partial concave mirror can be formed such that the focal position is arranged at the corner of the partial concave mirror and a part of the regular concave mirror is cut into a rectangular parallelepiped shape. In this case, the lower right portion of the light beam shown in FIG. 10B is deviated from the partial concave mirror, but the influence of the shadow of the electrode lead can be eliminated by arranging the focal point at the corner of the partial concave mirror, so that the light receiving efficiency is improved. The size of the photoreceiver can be reduced while improving.

このように、凹面鏡が、中心軸線Ｌを中央部に有する正規凹面鏡２０の一部を切り取った部分凹面鏡２として形成されるので、正規凹面鏡を使用する反射集光型受光器に比べ、受光器の小型化が可能となる。 In this way, the concave mirror is formed as a partial concave mirror 2 obtained by cutting off a part of the regular concave mirror 20 having the central axis L at the center, and therefore, compared with the reflective condensing type light receiver using the regular concave mirror. Miniaturization is possible.

さらに、部分凹面鏡２は、正規凹面鏡２０一部を、反射光が受光素子３に到達する直方体部分Ｂ２〜Ｂ４等で切り取った形状に形成されているので、鏡面で反射される光の殆どが受光素子３の受光面３ａに入射し、小型の凹面鏡に拘わらず、受光効率を高め、光電変換効率を向上させることができる。 Furthermore, since the partial concave mirror 2 is formed in a shape in which a part of the regular concave mirror 20 is cut off by the rectangular parallelepiped portions B2 to B4 where the reflected light reaches the light receiving element 3, most of the light reflected by the mirror surface is received. The light is incident on the light receiving surface 3a of the element 3 and the light receiving efficiency can be increased and the photoelectric conversion efficiency can be improved regardless of a small concave mirror.

また、部分凹面鏡２は正規凹面鏡２０の一部の鏡面で反射された反射光のみが限定的に受光素子３の受光面３ａに入射することとなるので、直射日光などの強力な光の集光による受光素子の破損を防止することができる。 Further, in the partial concave mirror 2, only the reflected light reflected by a part of the mirror surface of the regular concave mirror 20 is incident on the light receiving surface 3 a of the light receiving element 3 in a limited manner, so that powerful light such as direct sunlight is condensed. It is possible to prevent the light receiving element from being damaged.

１凹面鏡本体
２部分凹面鏡
３受光素子
３ａ受光面
４電極リード
５電極リード
６凹部
２０正規凹面鏡
Ａ１凹面領域
Ａ２凹面領域
Ａ３凹面鏡領域
Ｂ２直方体部分
Ｂ３直方体部分
Ｂ４直方体部分 DESCRIPTION OF SYMBOLS 1 Concave mirror main body 2 Partial concave mirror 3 Light receiving element 3a Light receiving surface 4 Electrode lead 5 Electrode lead 6 Concave 20 Regular concave mirror A1 Concave surface area A2 Concave region A3 Concave mirror region B2 Cuboid part B3 Cuboid part B4 Cuboid part

Claims

In a reflective and condensing type light receiver having a light receiving element that receives and reflects and collects spatial light superimposed with an information signal through a concave mirror having a focal point,
The concave mirror is formed as a partially concave mirror of a normal concave mirror having a focal point on a central axis that is a normal line of the center, and the light receiving element has its light receiving surface on the central axis passing through the focal point. Arranged toward the mirror side of the partially concave mirror,
The partial concave mirror is formed in a shape in which a part of the regular concave mirror is cut off at a position where the central axis passing through the focal point of the regular concave mirror is deviated toward one edge ,
A pair of electrode leads of the light receiving element is formed on the concave mirror body from the bottom of the concave concave mirror body forming the outer shell of the partial concave mirror to the light receiving element positioned above the partial concave mirror. One electrode lead is connected to the light receiving element through a side wall in the vicinity of the light receiving element, and the other electrode lead is connected to the inner side of the peripheral part of the partial concave mirror or the concave mirror. A reflection-condensing light receiver connected to the light-receiving element through a wall portion of the main body.