JP2565795Y2 - Light receiving device for optical communication - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light receiving device for optical communication applied to spatial transmission optical communication.

[0002]

2. Description of the Related Art A spatial transmission optical communication device using a space transmission system performs optical communication using the atmospheric space as a transmission medium, and transmits a signal light output from the light transmitting device to the atmospheric space. The optical communication is performed by inputting the data to a distant receiving device.

Here, the light receiving device is configured to receive the signal light from the light transmitting device by a condenser lens and a light receiving element. That is, the light receiving device is configured to once condense the signal light from the light transmitting device through the condensing lens and then receive the light on the light receiving surface of the light receiving element. The focal point of the incident signal light is
Optical communication can be performed in a state where the optical communication device always exists at the position of the light receiving surface of the light receiving element.

However, for example, when the light transmitting device is fixed at a certain place and the light receiving device is mounted on a moving body or the like to perform optical communication, the optical axis of the light receiving device is changed due to the vibration of the moving body or a change in the traveling direction. When the angle of deviation increases, the signal light incident via the condenser lens is collected at a position shifted from the light receiving surface of the light receiving element, making communication impossible. Therefore, it is necessary to increase the light receiving angle of the light receiving device, that is, the angle at which light can be received.
Thus, conventionally, the light receiving angle of the light receiving element has been increased by enlarging the light receiving surface of the light receiving element.

That is, by expanding the light receiving surface of the light receiving element, the light receivable range is expanded, and even if the light condensing position of the signal light incident through the condensing lens is slightly shifted,
The signal light is received.

[0006] However, when the light receiving surface of the light receiving element is enlarged, the junction capacitance of the light receiving element becomes large, so that a new problem arises in that the sensitivity to high frequency signals is reduced. On the other hand, a method of widening the light receiving angle by forming the condenser lens with a short-focus optical system is also conceivable.

That is, in the case of the light receiving device configured as described above, the signal light from the light transmitting device is focused at a short distance by the short focus optical system. As a result, the light-receiving angle with respect to the light-receiving element increases.

However, it is difficult to make the focal length of a lens having a constant aperture smaller than the F-number of "1.0" or less. There are limits to shortening.

[0009]

Therefore, as described above, in the conventional light receiving device, the light receiving angle of the light receiving device is increased by increasing the light receiving area of the light receiving element or by using a short focus optical system. .

However, when the light-receiving area of the light-receiving element is increased, there is a disadvantage that the sensitivity to high-frequency signals is reduced. When a short-focus optical system is used, when the lens diameter is kept constant. Since the focal length is limited, it is difficult to increase the light receiving diameter, and there is a disadvantage that the cost is further increased.

The present invention has been made in view of the above problems,
It is an object of the present invention to provide a light receiving device for optical communication capable of widening a light receiving angle without having to enlarge a light receiving surface of a light receiving element or using a short focus optical system.

[0012]

That is, in the light receiving device for optical communication according to the present invention, adjacent to the outside of the first condenser lens and different from the lens surface of the first condenser lens. A plurality of condensing lenses having an inclined lens surface are provided, and a reflecting mirror for guiding each focus of each of the plurality of condensing lenses to the center position of the light receiving element is provided. When the signal light to be incident is out of the light receivable range of the light receiving element, the signal light incident from any of the plurality of condenser lenses is reflected by the corresponding reflecting mirror and is incident on the light receiving element.

[0013]

In other words, even if the signal light incident through the first condenser lens does not enter the light receiving surface of the light receiving element, the signal light enters the light receiving surface by the plurality of lenses and the reflecting mirror. The light can be incident, and the light receiving angle can be enlarged.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a light receiving device for optical communication. This light receiving device is provided with a first condenser lens 11 on the signal light entrance side, and outputs light from a light transmitting device (not shown). It is configured to collect signal light.

The optical axis L1 of the condenser lens 11 is
Above, a light receiving element 12 composed of a photodiode or the like is disposed with its light receiving surface 13 facing the first condenser lens 11, and the signal light collected by the first condenser lens 11 is It is configured to receive light.

In this case, the center of the light receiving surface 13 of the light receiving element 12 is located on the optical axis L1 of the first condenser lens 11 and at the focal position F1 of the first condenser lens 11. Placed in

Further, a second condenser lens 16 having a lens surface having an inclination angle A1 with the lens surface of the first condenser lens 11
Is disposed adjacent to the first condenser lens 11. The line symmetric position of the focal position F2 of the second condenser lens 16 is the focal position F1 of the first condenser lens 11, that is,
A reflecting mirror 14 having a reflecting mirror surface 15 overlapping the center of the light receiving surface 13 is provided.

Here, the optical axis L of the first condenser lens 11
The incident light S1 parallel to 1 is condensed by the first condenser lens 11 and is incident on the light receiving surface 13 of the light receiving element 12. The incident light S2 incident on the optical axis L1 at an inclination angle A1 is the first light. When the light passes through the condensing lens 11, the light does not enter the light receiving surface 13.

On the other hand, when the lens surface of the second condenser lens 16 is set at an inclination angle A1 with respect to the first condenser lens 11,
The incident light S3 parallel to the incident light S2 is transmitted to the second condenser lens 16
Incident light parallel to the optical axis line L2, and enters the focal position. This signal light is reflected by the reflecting mirror surface 15,
The light enters the light receiving surface 13.

The angle between a straight line L4 connecting the center of the first condenser lens 11 and one end of the light receiving surface 13 and the optical axis L1 is A.
2. Assuming that an angle between a straight line L5 connecting the center of the second condenser lens 16 and one end of the virtual image 17a of the light receiving surface 13 formed by the reflecting mirror surface 15 and the optical axis L2 is A3, the light passes through the first condenser lens 11 The incident signal light is not only the signal light parallel to the optical axis L1 of the first condenser lens 11 but also the direct light receiving surface 1 if the incident light S4 is in a range smaller than the incident angle A2.
3 is incident.

Further, only the incident light S3 parallel to the optical axis L2 of the second condenser lens 16 is reflected by the reflecting mirror surface 15 via the second condenser lens 16 and enters the light receiving surface 13. In addition, the signal light S5 that is incident at an angle smaller than the optical axis L2 of the second condenser lens 16 and the incident angle A3 is also reflected by the reflecting mirror surface 15, and enters the light receiving surface 13. For this reason, as a light-receiving range of this light receiving device, when the light receiving angle θ passes through the first condenser lens 11, −A 2 <θ <A 2, and the light reception angle θ passes through the second condenser lens 16. In this case, (A1−A3) <θ <(A1 + A3). At this time, if the angle is set so that A2> (A1−A3), the light receiving angle θ continuously changes in the range of −A2 <θ <(A1 + A3).

Further, the optical axis L of the first condenser lens 11
The third lens is located at a position opposite to the second condenser lens 16 with respect to the first lens.
And a reflecting mirror 18 for causing the light condensed by the third condensing lens 17 to enter the light receiving element 12, and a second condensing lens 16 and a reflecting mirror 15.
It is installed by the same method as above. In this case, the light receiving angle θ becomes − (1A + A3) <θ <(A1 + A3), and a wider light receiving angle θ can be realized in the left and right than in the case where only the first condenser lens 11 is used.

As a result, as shown in FIG. 2, the directivity of each condenser lens is determined by the dotted line 31, the first condenser lens 11 and the second and third condenser lenses 16 and 17. However, at the dotted lines 32 and 33, the directivity of the entire light receiving element 12 is in the range of the solid line 34, which is clearly wider than the directivity 31 of only the first condenser lens 11.

As described above, the second and third condenser lenses 1
By providing the corresponding reflecting mirrors 14 and 18 and the corresponding reflecting mirrors 14 and 18, it becomes possible to reflect the signal light that has not entered the light receiving surface 13 and make it incident on the light receiving surface 13. For example, the light receiving device is moved. Even if the light receiving device is mounted on the body and performs optical communication, and the light receiving device shifts in the focal position due to vibration or a change in the traveling direction, the signal light focused outside the light receiving surface 13 is reflected by the reflecting mirrors 14 and 18. The light can be reflected and incident on the light receiving surface 13.

Therefore, according to the light receiving device for optical communication having the above structure, the lens surface having the inclination A1 different from the lens surface of the first condenser lens 11 is provided adjacent to the outside of the first condenser lens 11. A plurality of condenser lenses 16 and 17 are provided, and the focal point of each of the plurality of condenser lenses 16 and 17 is reflected and guided to the center position of the light receiving element 12.
4 and 18 are provided, and when the signal light incident on the first condenser lens 11 enters outside the receivable range of the light receiving element 12, the signal light enters from one of the plurality of condenser lenses 16 and 17. Since the signal light is reflected by the corresponding reflecting mirrors 14 and 18 and is incident on the light receiving element 12, the signal light incident through the first condenser lens 11 is
Signal light can be made to enter the light receiving surface 13 by the plurality of lenses 16 and 17 and the reflecting mirrors 14 and 18, thereby increasing the light receiving angle θ. become able to.

The arrangement of the condenser lens in the above embodiment is not limited to the lens arrangement arranged in the horizontal direction as shown in FIG. 3A, but also to the vertical and horizontal arrangements as shown in FIG. Any of a configuration arranged in the horizontal direction and a configuration arranged in the vertical, horizontal, and oblique directions as shown in FIG. 3C can be realized.

Further, in the above embodiment, the second and third condenser lenses 16 and 1 arranged on the left and right of the first condenser lens 11 are used.
Although the inclination, focal position, etc. of 7 are treated as having the same configuration, the light receiving device for optical communication of the present invention is not limited to this, and a condenser lens having a different inclination and focal position is combined. Thus, a light receiving device having an asymmetric light receiving range can be configured.

[0029]

As described above, according to the present invention, a signal light output from a light transmitting device is received by using the atmospheric space as a transmission medium and optical communication is performed, and a signal output from the light transmitting device is transmitted. A first condenser lens for condensing light, and a light receiving element disposed at a focal position on the optical axis of the first condenser lens and receiving signal light incident through the first condenser lens When,
A plurality of condenser lenses which are arranged adjacent to the first condenser lens and have an inclination, and which have different focal positions from the first condenser lens, and respective focal positions of the plurality of condenser lenses And a plurality of planar signal light reflecting mechanisms for reflecting the light to the focal position of the first condenser lens, respectively.
If the signal light incident from an angle that is not the same as the optical axis of the condenser lens is collected outside the light receiving range of the light receiving element,
The signal light is condensed by any one of the plurality of condenser lenses, is reflected by the signal light reflection mechanism, and is incident on the light receiving area of the light receiving element. It is possible to widen the light receiving angle without having to use a short focus optical system.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a light receiving device for optical communication according to an embodiment of the present invention.

FIG. 2 is a diagram showing a light receiving range in a light receiving element of the light receiving device for optical communication.

FIG. 3 is a view showing an arrangement state of condenser lenses in the light receiving device for optical communication.

[Explanation of symbols]

11: first condenser lens, 12: light receiving element, 13: light receiving surface, 14, 18: reflecting mirror, 15: reflecting mirror surface, 16: second
17: Third condenser lens, 17a: virtual image of the light receiving surface, A1: lens inclination angle, L1, L2: optical axis, F
1, F2: Focus position.

Claims (1)

(57) [Scope of request for utility model registration] An optical communication light receiving device for receiving a signal light output from a light transmitting device using an atmospheric space as a transmission medium and performing optical communication, wherein the light receiving device collects the signal light output from the light transmitting device. A first condenser lens, and a focal point on the optical axis of the first condenser lens;
A light receiving element that receives the signal light incident through the first condenser lens; and a focal point different from the first condenser lens that is arranged adjacent to the first condenser lens with an inclination. A plurality of condensing lenses having positions, and a plurality of planar signal light reflecting mechanisms for respectively reflecting the focal positions of the plurality of condensing lenses to the focal position of the first condensing lens, When the signal light incident from an angle that is not the same as the optical axis of the first condenser lens is collected outside the light receiving range of the light receiving element, the signal light is transmitted by any of the plurality of condenser lenses. A light receiving device for optical communication, wherein the light is condensed, reflected by the signal light reflecting mechanism, and made incident on a light receiving range of the light receiving element.