JP2006310913A - Optical transmission apparatus and optical space transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of a complicated mechanism for deflecting an optical transmission signal and an increased optical transmission power in order to carry out optical transmission within a wide optical reception installation range. <P>SOLUTION: A lens 204 is provided on a front side of a light emitting element unit 203, vertical drive sections 206a, 206b, and horizontal drive sections 207a, 207b move the lens 204 so as to deflect an optical transmission signal with a power density distribution wherein a plurality of optical power density maximum parts exist. Thus, the optical receivers can correctly reproduce information data within the optical receiver installation range being a two-dimensional wide range by having only to move the lens 204 within a small range. Since it is not necessary to send out optical transmission signal of power density more than the minimum power density, and transmission power can be supressed small. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical space transmission system that transmits information data such as a video signal, an audio signal, and a digital data signal as an optical signal between an optical transmission device and an optical reception device through a free space.

  In the optical space transmission system, it is necessary to obtain an optical power density of a certain value (minimum received light power density) or higher so that information data can be reproduced from the optical transmission signal at the position of the optical receiver. On the other hand, it is desirable to widen the range in which the optical receiver can be installed so that the user can easily use it.

  For this reason, as a conventional optical space transmission system, there has been a system in which an optical transmission signal from an optical transmission device has a substantially uniform optical power density over a wide range. (For example, refer to Patent Document 1). FIG. 11 shows the configuration of the optical transmitter of the conventional optical space transmission system described in Patent Document 1, and FIG. 12 shows the light of the conventional optical space transmission system described in Patent Document 1. The optical power density distribution of the optical transmission signal sent out from a transmitter is shown.

  In FIG. 11, the light from the light emitting elements 1a and 1b and the light from the light emitting elements 1c and 1d are transmitted through the lenses 2a and 2b, respectively. The transmission light from the lens 2a and the lens 2b was superposed to make the optical power density almost uniform over a wide range as shown in FIG. As a result, an optical power density equal to or higher than the minimum received power density was obtained in a wide range.

  On the other hand, some conventional optical space transmission systems adjust the optical axis of the transmitted light in order to obtain the light receiving power of the optical signal necessary for signal reproduction in the optical receiver ( For example, see Patent Document 2). FIG. 13 shows an optical transmitter / receiver of a conventional optical space transmission system described in Patent Document 2. In FIG.

In FIG. 13, the optical transmission / reception device 10 serves as both an optical transmission device and an optical reception device, but here it will be described as an optical transmission device. An optical transmission signal is transmitted from the transmission lens 11, and the optical transmission signal is received by an opposing receiving device (not shown). This optical transmission signal has a maximum power density almost on the optical axis of the transmission lens 11, and a power density equal to or higher than the minimum received light power density can be obtained in a relatively narrow angle range near the optical axis. Yes. Then, in order to align the direction of the maximum power density with the direction of the opposing receiving device (thus, to align the optical axis of the transmitting lens 11 with the direction of the opposing receiving device), it is rotated by orthogonal axes 13 and 14 and transmitted. It was the structure which deflects the direction of a lens.
Japanese Patent Laid-Open No. 11-150513 (page 3, FIG. 1) Japanese Patent Laid-Open No. 10-276133 (page 4, FIG. 11)

  However, in the conventional configuration such as Patent Document 1, an optical transmission signal must be transmitted so that a received light power density equal to or higher than the minimum received light power density can be obtained at all positions over a wide angle range. In addition, the range needs to be expanded two-dimensionally. For this reason, there is a problem that a large optical transmission power is required and the power consumption becomes extremely large.

  In the conventional configuration such as Patent Document 2, it is not necessary to increase the optical transmission power so much, but the axis of the optical transmission signal is deflected over the wide range of directions in which the optical receiver may be installed. There was a need to do. For this reason, there has been a problem that the mechanism for driving the transmission lens becomes complicated and large, and it takes a long time to deflect and adjust the axis of the optical transmission signal.

  The present invention solves the above-described conventional problems, and provides an optical space transmission system capable of transmitting information to an optical receiver in a short time with a small optical transmission power and a mechanism that can be simplified and miniaturized. For the purpose.

  In order to solve the above-described conventional problems, the optical space transmission system according to the first aspect of the present invention is a light source unit in which an optical transmission device gives a power density distribution having a plurality of optical power density maximum portions to the optical transmission signal. And an optical axis deflection unit that deflects the entire transmission direction of the optical transmission signal, and an optical axis control unit that controls the optical axis deflection unit, wherein the optical axis control unit includes a plurality of light beams of the optical transmission signal. The optical axis deflecting unit is controlled so as to deflect any one of the power density maximum portions in the direction of the optical receiver.

  According to the optical space transmission system of the first aspect of the invention, it is possible to obtain a received light power density equal to or higher than the minimum received light power density over a wide installation range of the optical receiver with a small optical axis deflection range.

  An optical space transmission system according to a second invention of the present invention is an invention dependent on the first invention, wherein a plurality of optical power density maximum parts of the optical transmission signal are between adjacent optical power density maximum parts. The power density at the minimum optical power density is set to be lower than the minimum received light power density level at which the transmission signal can be received in the optical receiver.

  An optical space transmission system according to a third invention of the present invention is an invention dependent on the first invention, wherein a plurality of optical power density maximum parts of the optical transmission signal are adjacent to each other. The power density at the minimum portion of the optical power density is set to ¼ or less of the power density at the maximum portion of the optical power density.

  According to the optical space transmission system of the second and third inventions, the transmission power of the optical transmission signal can be kept small.

  An optical space transmission system according to a fourth invention of the present invention is an invention dependent on any one of the first to third inventions, wherein the plurality of optical power density maximum portions of the optical transmission signal are substantially equal to each other. Arranged at intervals, the optical axis control unit controls the optical axis deflection unit within a deflection range that does not exceed at least the adjacent optical power density maximum.

  An optical space transmission system according to a fifth invention of the present invention is an invention dependent on any one of the first to third inventions, wherein a plurality of optical power density maximum portions of the optical transmission signal are substantially equal to each other. Arranged at intervals, the optical axis control unit controls the optical axis deflection unit within a half angle deflection angle range equal to or less than 1 / (2 · cos 45 °) times an angular difference between adjacent optical power density maximum portions. It has a configuration.

  According to the optical space transmission systems of the fourth and fifth inventions, a received light power density equal to or higher than the minimum received light power density can be obtained efficiently over a wide installation range of the optical receiver in a small optical axis deflection angle range. Can do.

  An optical space transmission system according to a sixth aspect of the present invention is an invention dependent on any one of the first to fifth aspects, wherein the light source section is constituted by a plurality of light emitting elements.

  An optical space transmission system according to a seventh aspect of the present invention is an invention dependent on any one of the first to sixth aspects, wherein the light source unit includes a plurality of light emitting elements and a front surface of the plurality of light emitting elements. It is comprised by the lens provided in.

  According to the optical space transmission systems of the sixth and seventh inventions, it is possible to realize a light source unit that gives a power density distribution having a plurality of optical power density maximum portions to an optical transmission signal with a simple configuration.

  An optical space transmission system according to an eighth aspect of the present invention is an invention dependent on the seventh aspect, wherein the distance from the plurality of light emitting elements is substantially equal to the focal length of the lens. Yes.

  According to the optical space transmission system of the eighth aspect of the present invention, a light source unit that provides a power density distribution having a plurality of light power density maximum portions to an optical transmission signal in a form having a plurality of beams having a small divergence angle is realized. Energy efficient transmission in a range.

  An optical space transmission system according to a ninth invention of the present invention is an invention dependent on any one of the first to sixth inventions, wherein the light source unit includes a plurality of light emitting elements and a front surface of the plurality of light emitting elements. And a diffusing plate that radiates diffused radiation that diffuses the emitted light of the light emitting element, and a lens that adjusts the spread angle of the diffused radiation from the diffusion plate.

  According to the optical space transmission system of the ninth aspect of the present invention, with a simple configuration, it is possible to provide a power density distribution having a plurality of optical power density maximum portions as described above, and to realize a light source portion having a small adverse effect on the human body. Can do.

  An optical space transmission system according to a tenth aspect of the present invention is an invention dependent on the ninth aspect, wherein the lens is disposed at a position where the distance from the diffusion plate is substantially equal to the focal length of the lens. is doing.

  According to the optical space transmission system of the tenth aspect of the present invention, the light source unit that provides a power density distribution having the plurality of light power density maximum portions in a form having a plurality of beams having a small divergence angle and has a small adverse effect on the human body. Realized and enables energy efficient transmission over a wide range.

  An optical space transmission system according to an eleventh aspect of the present invention is an invention dependent on any one of the seventh to tenth aspects, wherein the optical axis deflecting portion is substantially perpendicular to the lens axis. The lens driving unit moves in the direction.

  According to the optical space transmission system of the eleventh aspect, the power transmission signal having the power density distribution having the plurality of light power density maximum portions can be deflected with a simple configuration.

  An optical space transmission system according to a twelfth aspect of the present invention is an invention dependent on any one of the first to the tenth aspects, wherein the optical axis deflection unit is emitted from the light source unit. The movable reflection mirror is configured to reflect a signal, and the reflection direction of the entire optical transmission signal is deflected and emitted by changing the angle of the movable reflection mirror.

  According to the optical space transmission system of the twelfth aspect of the present invention, an optical transmission signal having a power density distribution having the plurality of optical power density maximum portions can be deflected by changing the angle of a small movable reflector.

  An optical space signal transmission system according to a thirteenth aspect of the present invention is an invention subordinate to the twelfth aspect, wherein light emitted from the plurality of light emitting elements intersects each other, and the movable reflection is applied to the intersecting portion. The mirror is provided.

  According to the optical space transmission system of the thirteenth aspect of the invention, the optical transmission signal having the power density distribution having the plurality of optical power density maximum portions can be deflected by the movable reflecting mirror having a small area.

  An optical space transmission system according to a fourteenth aspect of the present invention is an invention dependent on any one of the first to thirteenth aspects, wherein the optical receiver includes a light receiving unit that receives the optical transmission signal, A light reception power detection unit that detects the light reception power of the light reception unit; and a light reception information transmission unit that transmits light reception power information in the light reception power detection unit. A light reception information reception unit that receives light reception power information is provided, and the optical axis control unit is configured to control the optical axis deflection unit based on the light reception information received by the light reception information reception unit.

  According to the optical space transmission system of the fourteenth aspect, one of the optical power density maximum portions of the optical transmission signal of the power density distribution having the plurality of optical power density maximum portions is directed to the optical receiver with high accuracy. Can be deflected.

  According to the optical space transmission system of the present invention, information can be transmitted to an optical receiver in a short time with a small optical transmission power and a mechanism that can be simplified and miniaturized.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an optical space transmission system according to Embodiment 1 of the present invention. In FIG. 1, an optical space transmission system 100 includes an optical transmitter 101 and an optical receiver 111. The optical transmission device 101 includes a modulation circuit 103, a light source unit 104, an optical axis deflection unit 105, an optical axis control unit 106, and a light reception information reception unit 107. The optical reception device 111 includes a light reception unit 113 and a light reception power detection unit 114. The light receiving information transmitting unit 115 and the demodulating unit 116 are configured. In FIG. 15, broken line arrows indicate optical signals, and solid line arrows indicate electrical signals.

  Next, the operation of the optical space transmission system 100 will be described. An input signal including information data to be transmitted is input to the modulation circuit 103 of the optical transmission device 101, converted into an electric signal for modulating the light source unit 104, and then added to the light source unit 104. The light source unit 104 is a light source that transmits an optical transmission signal having a power density distribution having a plurality of optical power density maximum portions, which will be described in detail later. An optical transmission signal with a power density distribution having a plurality of optical power density maximum portions sent from the light source unit 104 is deflected in the entire direction by an optical axis deflecting unit 105 controlled by the optical axis control unit 106. Thus, the light is emitted from the optical transmission device 101 to free space. The radiated optical transmission signal is a broken-line arrow in FIG. 1, and has a power density distribution having a plurality of optical power density maximums as shown in the figure. The optical signal radiated to the free space is received by the light receiving unit 113 of the optical receiving device 111 and converted into an electric signal corresponding to the received light power. The received light power detecting unit 114 receives the electric signal from the light receiving unit 113 and amplifies it. The signal is output to the demodulator 116. The demodulator 116 outputs an output signal including information data. On the other hand, the light reception information sending unit 115 also receives a signal from the light reception power detection unit 114 and transmits the light reception power information to the light reception information reception unit 107 of the optical transmission device 101 (a chain line in the figure). As the transmission path of the received light power information, for example, a wireless transmission path using a separately provided radio wave is used, but an optical space transmission path, a wired transmission path, or the like may be used. Based on the received light power information from the received light information receiving unit 107, the optical axis control unit 106 deflects one of a plurality of maximum optical power density portions of the optical transmission signal in the direction of the light receiving unit 113 of the optical receiving device 111. Thus, the optical axis deflecting unit 105 is controlled. As a result, in the optical receiver, it is possible to obtain a light power density that is equal to or higher than the minimum received light power density capable of reproducing information data from the optical transmission signal. The light power density maximum portion deflected in the direction of the light receiving portion 113 may be a maximum portion that can be deflected in the direction of the light receiving portion 113 with the smallest deflection angle.

  As described above, information data can be transmitted as an optical signal from the optical transmitter 101 to the optical receiver 111 through free space.

  The point of deflecting the optical transmission signal in accordance with the direction of the optical receiver and transmitting the information data is the same as that of the conventional optical space transmission system shown in FIG. An optical transmission signal having a power density distribution having a plurality of optical power density maximum portions is transmitted, and the optical axis control unit 106 determines any one of the plurality of optical power density maximum portions of the optical transmission signal as the light receiving device 111. What is necessary is just to deflect in the direction of the light-receiving part 113. FIG. For example, the deflection may be performed within a deflection range that does not exceed at least the adjacent maximum optical power density maximum, and even if the optical axis deflection unit 105 has a small deflection angle, a wide installation range of the optical receiver 111 can be covered. The deflection unit 105 can be made small and simple. Compared with the conventional optical space transmission system shown in FIG. 11, it is not necessary to send a substantially uniform power density equal to or higher than the minimum received power density to the entire installation range of the optical receiver 111, and the optical power density maximum portion. If the vicinity is equal to or higher than the minimum light reception power density, the distance may be smaller than the minimum light reception power density. For example, since the discrete power density distribution as shown in FIG. 1 is sufficient, the optical transmission power of the light source unit 104 can be greatly reduced.

  FIG. 2 is a side sectional view showing an optical transmission device 201 in the configuration example of the optical transmission device 101 of the optical space transmission system of the present invention described in FIG. 3 is a rear sectional view as seen from the direction of arrow A in the two-point difference line in FIG. 1, and FIG. 4 is a front sectional view in the direction of the two-point difference line in FIG.

  2 to 4, a light emitting element unit 203 composed of a plurality of (seven in the figure) light emitting elements 203a to 203g arranged in a two-dimensional manner is fixed to a housing 205 of the optical transmission device 201. . A plurality of light beams whose optical axes are substantially parallel to each other are emitted from the plurality of light emitting elements 203 a to 203 g of the light emitting element unit 203. A lens 204 is provided on the front surface of the light emitting element unit 203, and the distance from the light emitting elements 203 a to 203 g is substantially equal to the focal length of the lens 204. As a result, the light beams from the light emitting elements 203a to 203g are converted into a plurality of beams, each of which is a substantially parallel beam and having different angles. The light emitting element unit 203 and the lens 204 correspond to the light source unit 104 in the optical transmission system 100 of FIG. 1 and transmit an optical transmission signal having a power density distribution having a plurality of optical power density maximum portions. The lens 204 is fixed to the housing 205 via vertical drive units 206a and 206b and horizontal drive units 207a and 207b that move the lens 204 in the horizontal direction and the vertical direction, respectively. Accordingly, the lens 204 can be moved two-dimensionally in a plane perpendicular to the axis of the lens 204 using the vertical driving units 206a and 206b and the horizontal driving units 207a and 207b. By moving the lens 204 in this manner, the direction of the entire optical transmission signal having a power density distribution having a plurality of optical power density maximum portions can be deflected. That is, the vertical drive units 206a and 206b, the horizontal drive units 207a and 207b, and the lens 204 correspond to the optical axis deflection unit 105 of the optical transmission system 100 in FIG. The vertical drive units 206a and 206b and the horizontal drive units 207a and 207b can be realized by using a voice coil or the like.

  2 to 4, the modulation circuit 103, the optical axis control unit 106, and the light reception information receiving unit 107 in FIG. 1 are omitted and not shown.

  Next, the operation of the optical transmission apparatus 201 will be described.

  As described above, an optical transmission signal having a power density distribution having a plurality of light power density maximum portions is transmitted by the light emitting element unit 203 and the lens 204. For example, if there is an optical receiver installation surface as shown in FIG. 2, the power density distribution as shown in FIG. 2 is obtained on the optical receiver installation surface. Since the light emitting elements 203a to 203g of the light emitting element unit 203 are arranged at equal intervals, the light power density maximum portions of the power density distribution are also arranged at substantially equal intervals. In this power density distribution, the optical receiver is used only in a portion exceeding the minimum received light power density as shown in FIG. 2 (in FIG. 2, the solid line of the power density distribution is on the right side of the minimum received light power density). Information data can be reproduced correctly. FIG. 5 shows, in broken lines, the receivable range of the receiving device when the receiving device installation surface in FIG. 2 is viewed from the arrow A side. As shown in FIGS. 2 and 5, when the optical receiver 213 is installed, the optical receiver 213 cannot correctly reproduce the information data in this state. Therefore, as shown in FIG. 6, when the lens 204 is moved downward by δ in FIG. 6 by the vertical driving units 206a and 206b, an optical transmission signal having a power density distribution having a plurality of optical power density maximum portions is obtained. By deflecting downward in FIG. 6, the power density distribution in the optical receiver 213 can be made larger than the minimum received light power density, and the information data can be reproduced correctly. Similarly, when the optical receiver 213 ′ is installed as shown in FIGS. 2 and 5, the lens 204 is moved downward in FIG. 7 by the vertical drive units 206a and 206b as shown in FIG. The information data can be correctly reproduced by the optical receiver 213 by moving by δ ′. The driving direction and driving amount of the vertical driving units 206a and 206b can be determined by the received light power information in FIG.

  In the above, only the vertical drive units 206a and 206b are used, but the horizontal drive units 207a and 207b are also used at the same time to deflect the emission direction of the optical transmission signal two-dimensionally, and the installation range of the two-dimensional optical receiver Can be covered. For example, the lens 204 is moved by the vertical drive units 206a and 206b and the horizontal drive units 207a and 207b so that the center moves within the solid circle in the range where the power density indicated by the broken-line circle in FIG. The optical receiver installation range in a two-dimensional range can be covered. At this time, the half angle of the deflection angle in the emission direction of the optical transmission signal is 0.58 (1 / (2 · cos 30 °)) times or more of the angle difference (α in FIG. 2) between adjacent optical power density maximum portions. By doing so, the polarization directions of the adjacent optical power density maximum portions can be overlapped with each other, and the optical receiver installation range within the entire range of the seven solid line circles in FIG. 5 can be covered.

  Since only a small deflection angle needs to be given to the optical transmission signal in this way, the lens 204 is replaced with the vertical drive units 206a and 206b and the horizontal drive units 207a and 207b as in the first embodiment of the present invention. Therefore, it is possible to use a deflection method having a simple configuration in which the lens is moved by the movement.

  Compared with the conventional optical transmission system shown in FIGS. 11 to 12, it is not necessary to send an optical transmission signal to the entire optical receiver range with a power density distribution equal to or higher than the minimum received light power density. Transmission power can be reduced. In particular, as shown in FIG. 2, if the optical power density distribution is made discrete by providing a portion where the power density is almost zero between the optical power density maximum parts, the transmission power can be greatly reduced. It becomes.

  As described above, according to the first embodiment of the present invention, the lens 204 is provided on the front surface of the light emitting element unit 203, and the lens 204 is moved by the vertical driving units 206a and 206b and the horizontal driving units 207a and 207b. By deflecting an optical transmission signal having a power density distribution having a maximum optical power density distribution, the lens 204 can be moved within a small range by moving the lens 204 within a small two-dimensional range. Information data can be reproduced correctly.

  Further, since it is not necessary to transmit an optical transmission signal having a power density equal to or higher than the minimum received light power density over the entire two-dimensional wide range of optical receiver installation ranges, the transmission power can be kept small.

  In the first embodiment, the light emitting elements 203a to 203g of the light emitting element unit 203 are arranged as shown in FIG. 4, and an optical transmission signal having a power density distribution having a plurality of light power density maximum portions from the lens 204 is obtained. However, instead of the light emitting element unit 203, the light emitting element unit 303 in which the light emitting elements 303a to 303i are arranged at almost equal intervals as shown in FIG. An optical transmission signal having a power density distribution may be emitted. In this case, the half angle of the outgoing direction deflection angle of the optical transmission signal is set to 0.71 (1 / (2 · cos 45 °)) times or more of the angle difference between adjacent optical power density maximums. The polarization directions of the matching optical power density maxima can be superimposed on each other. Even if the case of FIG. 8 is included, if there is a small deflection angle of about 0.71 (1 / (2 · cos 45 °)) times the angular difference between adjacent optical power density maximums, a two-dimensional wide range. Thus, it is possible to correctly reproduce the information data in the optical receiver apparatus installation range.

  In the first embodiment, the light emitted from the light emitting elements 203a to 203g of the light emitting element unit 203 is converted into substantially parallel light by the lens 204, but needless to say, it is not always necessary to use parallel light. Yes.

  In the first embodiment, the light receiving information from the light receiving device 111 is used for controlling the optical axis deflecting unit 105. However, even when other control methods are used, a plurality of optical power densities are used. By deflecting the optical transmission signal having the power density distribution having the maximum portion, there is no change in the effect that it is possible to cover a wide two-dimensional optical receiver installation range with a small deflection angle.

(Embodiment 2)
FIG. 9 is a configuration diagram of the optical transmission device 401 of the optical space transmission system according to the second embodiment of the present invention. A block diagram showing the configuration of the optical space transmission system is the same as FIG. In FIG. 9, the same components as those in FIG.

  9 is different from the optical transmission device 201 in the first embodiment of the present invention shown in FIG. 2 in that the light emitting element unit 403 is added with light emitting elements 403a to 403g (light emitting elements 403d to 403g are added similarly to FIG. 4). 2 is arranged in a two-dimensional manner, but not shown in the figure), and a diffusion plate 408 provided in front of the light emitting elements 403a to 403g. The distance between the lens 204 and the diffusion plate 408 is substantially equal to the focal length of the lens 204. The diffuser plate 408 converts incident light into diffused light having a distribution conforming to the Lambertian distribution. For example, a fine granular transparent material having a different refractive index is mixed into a transparent resin material, or a transparent resin material is used. Or a fine foam structure.

  In Embodiment 1 of the present invention described above, the spread angle of the emitted light from the light emitting elements 203a to 203g of the light emitting element unit 203 is directly converted by the lens 204, and an optical transmission signal is generated efficiently. However, depending on the magnitude of the light output of the light emitting elements 403a to 403g, the optical transmission signal may be harmful to human eyes such as eyes. In such a case, the configuration shown in Embodiment 2 can reduce harmful effects on the human body. In the second embodiment, the light emitted from the light emitting elements 403a to 403g is diffused by the diffusion plate 408 to reduce coherence, and then the divergence angle is converted by the lens 204, whereby a plurality of optical power densities are obtained. An optical transmission signal with a power density distribution having a local maximum is transmitted. For this reason, even if the emitted light is collected using an optical device such as an eyeball lens or binoculars, it is difficult to converge on a minute spot, and harmful effects on the human body can be reduced. Even in this case, an optical transmission signal having a power density distribution having a plurality of optical power density maximum portions is transmitted, and the lens 204 is moved by the vertical driving units 206a and 206b and the horizontal driving units 207a and 207b (not shown). Thus, the information data can be correctly reproduced by the optical receiver in the two-dimensional wide optical receiver installation range only by deflecting the optical transmission signal within a small angle range. Further, since it is not necessary to transmit an optical transmission signal having a power density equal to or higher than the minimum received light power density over the entire two-dimensional wide optical receiver installation range, the transmission power can be suppressed to be small. It is the same.

  As described above, according to the second embodiment of the present invention, the lens 204 is provided on the front surface of the light emitting element unit 403 including the light emitting elements 403a to 403g and the diffusion plate 408 provided on the front surface of the light emitting elements 403a to 403g. The lens 204 is moved by the driving units 206a and 206b and the horizontal driving units 207a and 207b to deflect an optical transmission signal having a power density distribution having a plurality of optical power density maximum portions, so that the lens 204 can be moved in a small range. By simply moving it, information data can be correctly reproduced by the optical receiver in the two-dimensional wide optical receiver installation range, and the adverse effect of the optical transmission signal on the human body can be reduced.

  In Embodiment 2 of the present invention, since the light emitted from the light emitting elements 403a to 403g is diffused by the diffusion plate 408, each of the light emitted from the light emitting elements 403a to 403g uses the lens 204. However, it becomes difficult to reduce the spread. For this reason, the discrete power density distribution as shown in FIG. 2 is not achieved, and the continuous power density distribution as shown in FIG. 9 may be obtained. Even in such a case, the power density of the light power density minimum portion between the adjacent light power density maximum portions of the plurality of light power density maximum portions should be, for example, ¼ or less of the power density of the light power density maximum portion. For example, the transmission power can be suppressed to about ½ or less compared to the case where an optical transmission signal having a power density equal to or higher than the minimum light reception power density is transmitted to the entire optical receiver installation range.

  In the first and second embodiments of the present invention, the optical transmission signal is deflected by moving the lens 204. However, the present invention can cover a two-dimensional wide optical receiver installation range with a small deflection angle by deflecting an optical transmission signal having a power density distribution having a plurality of optical power density maximum portions, and optical transmission power. It is a feature that can be kept low. Therefore, as in the first and second embodiments, a simple configuration for moving the lens 204 can be used, but the method for deflecting the optical transmission signal is not limited to this. For example, as in the conventional optical transmission system shown in FIG. 13, the optical transmission signal may be deflected by using two orthogonal rotation mechanisms. Even when such a change method is used, the rotation range of the rotation mechanism can be reduced by deflecting the optical transmission signal having a power density distribution having a plurality of optical power density maximum portions. For this reason, the rotation mechanism can be simplified, and furthermore, the effect that the adjustment of the polarization direction can be completed in a short time can be obtained.

  Further, instead of moving the lens 204 to deflect the optical transmission signal, it may be deflected by a movable reflecting mirror. For example, FIG. 10 shows a power density distribution light having a plurality of light power density maximum portions obtained by converting emitted light from a light emitting element unit 503 composed of a plurality of light emitting elements 503a to 503c by a lens 504 as in FIG. Although the transmission signal is sent out, the angle of the movable reflecting mirror 509 is changed by the driving units 506a and 506b in order to deflect the optical transmission signal. Even in such a case, the movable angle range of the movable reflecting mirror 509 can be reduced by adopting a configuration that deflects the optical transmission signal having a power density distribution having a plurality of optical power density maximum portions. It becomes possible to cover a wide optical receiver installation range with the configuration. For example, even if a movable reflecting mirror (MEMS (Micro-Electro-Mechanical Systems) mirror) manufactured using a semiconductor manufacturing technique is used, a wide optical receiver installation range can be covered. In FIG. 10, the distance between the plurality of light emitting elements 503 a to 503 c and the lens 504 is substantially equal to the focal length of the lens 504, as in FIG. 2, and the emitted light from each of the light emitting elements 503 a to 503 c is A plurality of light beams that are substantially parallel to each other. At this time, the plurality of light beams intersect with each other at one point. By providing the movable reflecting mirror 509 at this intersection, the area of the reflecting surface necessary for the movable reflecting mirror 509 can be reduced. When the light emitted from the light emitting elements 503a to 503c of the light emitting element unit 503 has an optical axis parallel to each other, the distance between the intersection and the lens 504 is the focal length of the lens 504, and is at that position. A movable reflecting mirror 509 may be provided. However, when the light emitted from the light emitting elements 503a to 503c of the light emitting element unit 503 is not an optical axis parallel to each other, the distance between the intersection and the lens 504 is not the focal distance of the lens 504, but also intersects. A movable reflecting mirror 509 may be provided in the portion.

  The optical space transmission system according to the present invention has a feature that information can be transmitted to an optical receiver in a short time with a small optical transmission power and a mechanism that can be simplified and miniaturized. It is useful as an optical space transmission system for transmitting data. It can also be used for spatial transmission of video signals and audio signals, and for applications such as remote control.

Configuration diagram of optical space transmission system according to Embodiment 1 of the present invention 1 is a side view showing the configuration of an optical transmission apparatus according to Embodiment 1 of the present invention. FIG. 3 is a rear cross-sectional view showing the configuration of the optical transmission device according to the first embodiment of the present invention. Front sectional drawing which shows the structure of the optical transmitter in Embodiment 1 of this invention Explanatory drawing of the receivable range of the optical receiver installation surface in Embodiment 1 of this invention Side view showing optical transmission signal deflection example 1 of the optical transmission apparatus in the first embodiment of the present invention. Side view showing an optical transmission signal deflection example 2 of the optical transmission device according to the first embodiment of the present invention. The front view which shows the modification of the light emitting element unit in Embodiment 1 of this invention. Side view showing the configuration of the optical transmission apparatus according to the second embodiment of the present invention. The side view which shows the modification of the transmission / reception apparatus in Embodiment 1 of this invention Side view showing the configuration of a conventional optical space transmission system Characteristics diagram of power density distribution of conventional optical space transmission system A perspective view showing a configuration of a conventional optical space transmission system

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical space transmission system 101 Optical transmitter 103 Modulation circuit 104 Light source part 105 Optical axis deflection part 106 Optical axis control part 107 Light reception information reception part 111 Light reception apparatus 113 Light reception part 114 Light reception power detection part 115 Light reception information transmission part 116 Demodulation part DESCRIPTION OF SYMBOLS 201 Optical transmitter 203 Light emitting element unit 203a-203g Light emitting element 204 Lens 205 Case 206a, 206b Vertical drive part 207a, 207b Horizontal drive part 213,213 'Light receiving device 303 Light emitting element unit 303a-303i Light emitting element 401 Optical transmitter 403 Light-Emitting Element Units 403a to 403c Light-Emitting Element 408 Diffuser 501 Optical Transmitting Device 503 Light-Emitting Element Units 503a to 503c Light-Emitting Element 504 Lenses 506a and 506b Drive Unit 509 Movable Reflector

Claims (14)

An optical transmitter that transmits an optical transmission signal through free space,
A light source unit that gives a power density distribution having a plurality of optical power density maximums to the optical transmission signal;
An optical axis deflector for deflecting the entire transmission direction of the optical transmission signal;
An optical axis control unit for controlling the optical axis deflection unit,
The optical axis control unit controls the optical axis deflecting unit so as to deflect any one of a plurality of maximum optical power density portions of the optical transmission signal in the direction of the optical receiving device. The power density of the optical power density minimum part between adjacent optical power density maximum parts of the plurality of optical power density maximum parts of the optical transmission signal is smaller than the minimum received light power density level at which the transmission signal can be received in the optical receiver. The optical transmission device according to claim 1. The power density of the minimum optical power density between the adjacent maximum optical power density portions of the plurality of maximum optical power density portions of the optical transmission signal is set to ¼ or less of the power density of the maximum optical power density portion. 2. The optical transmission device according to 1. The plurality of optical power density maximum portions of the optical transmission signal are arranged at substantially equal intervals, and the optical axis control unit is configured to deflect the optical axis within a deflection range that does not exceed at least the adjacent optical power density maximum portion. The optical transmission device according to claim 1, wherein the optical transmission device is configured to control a unit. The plurality of optical power density maximum portions of the optical transmission signal are arranged at substantially equal intervals, and the optical axis control section is 1 / (2 · cos 45 °) of the angle difference between adjacent optical power density maximum portions. The optical transmission device according to any one of claims 1 to 3, wherein the optical axis deflection unit is controlled within a half angle deflection angle range equal to or less than double. The optical transmission device according to claim 1, wherein the light source unit includes a plurality of light emitting elements. The optical transmission device according to claim 1, wherein the light source unit includes a plurality of light emitting elements and a lens provided in front of the plurality of light emitting elements. The optical transmission device according to claim 7, wherein the lens is disposed such that a distance from the plurality of light emitting elements is substantially equal to a focal length of the lens. The light source unit is provided on a plurality of light emitting elements, front surfaces of the plurality of light emitting elements, a diffusion plate that emits diffused radiation that diffuses light emitted from the light emitting elements, and a spread angle of the diffused radiation from the diffusion plate. The optical transmission device according to claim 1, wherein the optical transmission device is configured by a lens to be adjusted. The optical transmission device according to claim 9, wherein the lens is disposed at a position where a distance from the diffusion plate is substantially equal to a focal length of the lens. The optical transmission device according to any one of claims 7 to 10, wherein the optical axis deflection unit includes a lens driving unit that moves the lens in a direction substantially perpendicular to the axis of the lens. The optical axis deflecting unit is configured by a movable reflecting mirror that reflects the optical transmission signal emitted from the light source unit, and deflects and emits the reflection direction of the entire optical transmission signal by changing the angle of the movable reflecting mirror. The optical transmission device according to claim 1, wherein the optical transmission device is characterized. The optical transmitter according to claim 12, wherein emitted light from the plurality of light emitting elements intersects each other, and the movable reflecting mirror is provided at the intersecting portion. An optical space transmission system that includes an optical transmitter and an optical receiver, and transmits an optical transmission signal from the optical transmitter to the optical receiver via free space,
The optical transmitter is
A light source unit that gives a power density distribution having a plurality of optical power density maximums to the optical transmission signal;
An optical axis deflector for deflecting the entire transmission direction of the optical transmission signal;
An optical axis control unit for controlling the optical axis deflection unit,
The optical axis control unit controls the optical axis deflecting unit so as to deflect any one of the plurality of optical power density maximum portions of the optical transmission signal in the direction of the optical receiver;
The optical receiver is
A light receiving unit for receiving the optical transmission signal;
A received power detection unit for detecting the received power of the light receiving unit;
A light receiving information sending unit for sending received light power information in the received light power detecting unit;
The optical transmitter is
Furthermore, it has a light reception information reception unit that receives light reception power information from the light reception information transmission unit, and the optical axis control unit controls the optical axis deflection unit based on the light reception information received by the light reception information reception unit. Optical space transmission system configured.

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