JPH0593886A - Optical spatial transmission device - Google Patents

Abstract

(57) [Abstract] (Correction) [Object] The present invention is to reliably receive a light receiving element in an optical space transmission device that transmits desired information through a light beam that transmits a space without impairing the field of view. It is possible to control the amount of incident light, and to reliably transmit information even at an extremely close distance. According to the present invention, the polarization plane of a deflecting beam splitter 42 is tilted with respect to the polarization plane of a received light beam, and the amount of the received light beam incident on a light receiving element 30 is adjusted.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology (FIG. 2) Problem to be Solved by the Invention (FIG. 2) Means for Solving the Problem (FIG. 1) Action (FIG. 1) Example (1) Configuration of Example (FIG. 1) (2) Effect of Example (3) Other Example Effect of Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical space transmission device,
In particular, it is suitable for application to an optical space transmission device that transmits desired information through a light beam that transmits space.

[0003]

2. Description of the Related Art Conventionally, in this type of optical space transmission device, a part of a light beam sent to a transmission target is folded back and observed together with observation light coming from the transmission target.
There is proposed a device which can easily confirm the irradiation position of the light beam.

That is, as shown in FIG. 2, in the optical space transmission device 1, the laser diode 2 is driven by a predetermined information signal, and the transmission light beam LA1 having a predetermined plane of polarization is emitted from the laser diode 2. The lens 4 converts the transmission light beam LA1 into parallel rays, and then transmits the deflected beam splitter 6 to guide it to the lens 8. The lens 8 converts the transmission light beam LA1 into a converged light beam, and then the lens 1
The transmission light beam LA1 is converted into parallel rays having a predetermined size and guided to the mirror 12.

Here, the mirror 12 is arranged in parallel with the mirror 14, and is also arranged with an inclination of about 45 degrees in the optical path so that the inclination can be adjusted via a predetermined drive system. Thereby, in the optical space transmission apparatus 1, the transmission light beam LA1 is reflected by the mirrors 12 and 14, so that the inclination of the mirrors 12 and 14 can be adjusted and the emission direction of the transmission light beam LA1 can be changed. Has been done.

The half mirror 16 has a transmission light beam LA1.
Part of the light is reflected and guided to the corner cube prism 18. As a result, in the optical space transmission device 1, the optical path of the transmission light beam LA1 is bent by the corner cue prism 18, transmitted through the half mirror 16, and imaged by the imaging device 20.
Lead to.

Further, the half mirror 16 transmits the remaining transmission light beam LA1 and makes it enter the convex lens 22. Here, the convex lens 22 can be displaced perpendicularly to the optical axis by driving a predetermined actuator, so that in the optical space transmission device 1, the position of the lens 22 is changed and the transmission light beam LA1. The irradiation position of can be largely changed.

The lens 24 is a large-diameter convex lens, and is arranged at a predetermined distance from the convex lens 22, whereby the transmission light beam LA1 focused by the convex lens 22 is formed.
Is converted into a substantially parallel light beam of a predetermined size and emitted. As a result, in the optical space transmission device 1, the transmission light beam LA1 emitted from the lens 24 is irradiated onto the transmission target, and a desired information signal can be transmitted via the transmission light beam LA1.

In contrast to the transmission light beam LA1, the reception light beam LA2 coming from the transmission object is focused by the lens 24, converted into parallel rays by the lens 22, and incident on the half mirror 16. To do. At this time, ambient light LA3 to be transmitted (hereinafter referred to as observation light) also enters the half mirror 16 together with the received light beam LA2, is reflected by the half mirror 16 and enters the imaging device 20. As a result, in the optical space transmission apparatus 1, the transmission target can be observed through the imaging device 20, and the irradiation position of the transmission light beam LA1 can be easily adjusted.

At this time, in the optical space transmission device 1, the transmission light beam LA is transmitted by the corner cube prism 18.
By returning the optical path of No. 1 and entering the imaging device 20, the transmission light beam LA1 can be guided to the imaging device 20 as if it came from the irradiation position of the transmission light beam LA1. Accordingly, in the optical space transmission device 1,
Through the imaging device 20, the irradiation position of the transmission light beam LA1 can be observed as a bright and shining point.

On the other hand, in the received light beam LA2, a part thereof is similarly reflected by the half mirror 16 and guided to the image pickup device 20, so that the position of the transmission target can be observed as a bright and shining point. Thereby, in the optical space transmission apparatus 1, the irradiation position of the transmission light beam LA1 can be easily confirmed, and the installation work of the optical space transmission apparatus 1 can be simplified.

On the other hand, the received light beam LA2 transmitted through the half mirror 16 is reflected by the mirrors 14, 12 and the lens 1.
It is incident on the deflected beam splitter 6 through 0 and 8 sequentially. Here, the received light beam LA2 is the transmitted light beam LA1.
Is emitted from the transmission object so that the planes of polarization are orthogonal to each other, and is reflected by the deflected beam splitter 6 to enter the beam splitter 26.

Here, the received light beam LA2 is partially reflected and focused on the photodiode 30 via the lens 28, whereby the output signal of the photodiode 30 is processed by a predetermined signal processing circuit and transmitted. It is adapted to be able to receive a predetermined information signal sent from the object. On the other hand, the received light beam LA2 that has passed through the beam splitter 26, after passing through the filter 32, is focused by the position detection element (PDS) 36 via the lens 34.

As a result, in the optical space transmission device 1,
Based on the output signal of the position detection element 36, the mirror 12,
A servo system for controlling the tilt of 14 and the position of the lens 22 and correcting the irradiation position of the transmission light beam LA1 as a whole is formed, and even when the optical space transmission device 1 vibrates due to wind or the like, it is possible to reliably perform the operation. The transmission light beam LA1 can be sent to the transmission target.

Thus, the optical space transmission apparatus 1 can be easily installed by using the image pickup apparatus 20 and can transmit a desired signal bidirectionally through the light beams LA1 and LA2 for transmitting the space. ing.

A shutter 38 is inserted between the corner cube prism 18 and the half mirror 16, and the shutter 38 is closed if necessary so that the image pickup device 20 can observe only the transmission target. There is.

[0017]

By the way, the optical space transmission apparatus 1 of this type can be easily installed, and since it is not necessary to install a cable or the like for each transmission, the optical space transmission apparatus 1 can be fixed on the roof of a building or the like. In addition to transmitting information by
For example, it is considered to be convenient for use in television broadcasting.

In such a television relay,
Depending on the relay site, a video signal may be transmitted to a transmission object that is several [km] away. Therefore, in this type of optical space transmission apparatus, the transmission light beam LA1 is efficiently transmitted.
And the received light beam LA2 needs to be transmitted. That is, in this type of optical space transmission device, the transmission light beam L
In order to reduce the loss of A1 and the received light beam LA2,
It is necessary to select optical elements, etc.

On the other hand, when the distance to the transmission target is short, a predetermined amount of light can be secured by limiting the amount of light using, for example, a mechanical diaphragm. However, at the actual relay site, for example, dozens of meters on both banks of the river
A video signal may be transmitted between distant points.

In this case, in the mechanical diaphragm, it is necessary to finely adjust the diaphragm so that a desired light amount can be obtained with the diaphragm being sufficiently narrowed.

However, since the transmission light beam LA1 and the reception light beam LA2 of this type have high coherence, even if the aperture is finely adjusted in such a state that the aperture is sufficiently narrowed, the light amount is actually small. There are problems that cannot be adjusted. That is, when the diaphragm is sufficiently narrowed down, the diaphragm may be opened to increase the light amount. If you further narrow down the aperture,
The field of view becomes smaller and the transmission light beam LA1
However, there was a problem that the image signal could not be transmitted at a very close distance in the end because the irradiation position could not be corrected.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose an optical space transmission apparatus capable of reliably transmitting information even to an extremely close transmission target.

[0023]

In order to solve such a problem, according to the present invention, a transmission light beam LA1 of a predetermined polarization plane modulated by a predetermined information signal is sent to a transmission / reception device arranged at a predetermined distance. At the same time, by receiving the reception light beam LA2 having a predetermined plane of polarization transmitted from the transmission / reception device, an information signal is transmitted to the transmission / reception device via the transmission light beam LA1 and transmitted from the transmission / reception device via the reception light beam LA2. In the optical space transmission device 40 that receives the predetermined information signal, the light source 2 that emits the transmission light beam LA1, the light receiving element 30 that receives the reception light beam LA2, and the transmission light beam LA1 that is emitted from the light source 2 are provided. A polarized light beam separating means that reflects or transmits, and transmits or reflects the received light beam LA2, which is opposite to the transmitted light beam LA1, and guides it to the light receiving element. 6, and transmission optical beam LA1 emitted from the polarized light beam separation means 6 to the transmission / reception device, and transmission optical systems 10, 12 for guiding the received light beam LA2 coming from the transmission object to the polarized light beam separation means 6. 1
4, 22, 24, and a polarized beam splitter 42 is interposed between the light receiving element 30 and the polarized light beam separating means 6.
The polarization plane of the polarization beam splitter 42 is changed with respect to the polarization plane of the reception light beam LA2, and the light amount of the reception light beam LA2 incident on the light receiving element 30 is adjusted.

[0024]

The polarized light beam splitter 42 is inserted between the light receiving element 30 and the polarized light beam separating means 6 to receive the received light beam LA.
The received light beam LA that enters the light receiving element 30 by changing the polarization plane of the polarization beam splitter 42 with respect to the polarization plane of 2
If the light amount of 2 is adjusted, the reception light beam LA2
You can adjust the amount of light.

[0025]

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

(1) Configuration of the Embodiment In FIG. 1 in which parts corresponding to those in FIG. 2 are designated by the same reference numerals, 40 denotes an optical space transmission device as a whole, and a lens 2
A deflecting beam splitter 42 is interposed between the beam splitter 8 and the beam splitter 26.

That is, in this type of optical space transmission device 40, by using the deflected beam splitter 6,
The transmission light beam LA1 and the reception light beam LA2 are separated by utilizing the difference in polarization plane.

If the angle of the plane of polarization of the deflected beam splitter 42 is inclined with respect to the plane of polarization of the received light beam LA2, the total amount of light is adjusted according to the inclination without impairing the field diameter. be able to.

Further, it is possible to effectively avoid the interference of the received light beam LA2 as in the case of using the mechanical diaphragm, and it is possible to reliably adjust the light quantity.

That is, in the optical space transmission device 40,
The output signal of the light receiving element 30 is given to the signal processing circuit 44, and the information signal S1 sent from the transmission target is demodulated here.
Further, in the optical free space transmission device 40, the output signal is given to the signal level detection circuit 46, and the signal level detection result is output to the motor drive circuit 48.

Here, the motor drive circuit 48 rotationally drives the motor 50 based on the signal level detection result so that the output signal of the light receiving element 30 becomes a predetermined signal level. The motor 50 tilts the angle of the deflected beam splitter 42 via a predetermined gear so that the received light beam L
The polarization plane of the polarized beam splitter 42 is set to a predetermined angle with respect to the polarization plane of A2. Thus, by using the deflected beam splitter 42, the loss in the deflected beam splitter 42 can be reduced, and information can be reliably transmitted to a transmission object at a long distance.

(2) Effects of the Embodiments With the above-described structure, the deflection beam splitter is tilted with respect to the plane of polarization of the received light beam LA2 to adjust the amount of incident light on the light receiving element, thereby making it possible to transmit objects that are very close together. Also, the light amount of the received light beam can be adjusted to a desired light amount, and thus information can be reliably transmitted even to an extremely close transmission target.

(3) Other Embodiments In the above-described embodiments, the case where the optical space transmission device is used for television relay is described, but the present invention is not limited to this, and various information signals are transmitted. It can be widely applied to optical space transmission devices.

[0034]

As described above, according to the present invention, the deflection beam splitter is tilted with respect to the plane of polarization of the received light beam, and the light amount of the received light beam incident on the light receiving element is adjusted, thereby reducing the loss. As a result, the light quantity of the received light beam can be adjusted to a desired light quantity as required, and thereby an optical space transmission apparatus can be obtained that can reliably transmit information even to an extremely close transmission target.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical free space transmission apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a conventional optical space transmission device.

[Explanation of symbols]

1, 40 ... Optical space transmission device, 2 ... Laser diode, 6, 42 ... Deflection beam splitter, 16 ... Half mirror, 24 ... Convex lens, 50 ... Motor.

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[Procedure amendment]

[Submission date] February 10, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction content]

[0005] Here, the mirror 12, the mirror 14 and co,
It is arranged at an angle of about 45 degrees in the optical path, and the inclination can be adjusted via a predetermined drive system. Accordingly, in the optical space transmission device 1, the mirrors 12 and 14 are
By reflecting the transmitted light beam LA1 by adjusting the tilt of the mirrors 12 and 14
The injection direction of 1 can be changed.

Claims (1)

[Claims] 1. A transmission light beam of a predetermined polarization plane modulated by a predetermined information signal is transmitted to a transmission / reception device arranged at a predetermined distance, and a reception light beam of a predetermined polarization plane is transmitted from the transmission / reception device. By receiving the light, the optical space transmission device that transmits the information signal to the transmission / reception device via the transmission light beam and receives the predetermined information signal transmitted from the transmission / reception device via the reception light beam. A light source that emits the transmission light beam, a light-receiving element that receives the reception light beam, reflects or transmits the transmission light beam emitted from the light source, and the reception light beam is opposite to the transmission light beam. The polarized light beam separating means for transmitting or reflecting the beam to the light receiving element and the transmitting light beam emitted from the polarized light beam separating means for transmitting / receiving the light are provided. And a transmission optical system for guiding the received light beam coming from the transmission object to the polarized light beam separating means, and inserting a polarizing beam splitter between the light receiving element and the polarized light beam separating means. ,
An optical space transmission device, wherein the polarization plane of a polarization beam splitter is changed with respect to the polarization plane of the received light beam to adjust the light quantity of the received light beam incident on the light receiving element.