JP3108960B2 - Optical space transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for spatially transmitting information such as video and audio, and more particularly to an optical space transmission device for preventing a laser beam for transmitting information from being irradiated on a person or the like.

[0002]

2. Description of the Related Art For example, when video and audio signals are transmitted between a video reproducing apparatus and a television, information is transmitted using light to improve the degree of freedom in layout of the video reproducing apparatus and the television in a room. In some cases, an optical spatial transmission device that performs spatial transmission of the optical signal is used. By the way, in an optical space transmission device using laser light as light for information transmission, an interpersonal safety device for preventing the laser light from being irradiated on a person is required.

[0003] Conventionally, Japanese Unexamined Patent Application Publication No.
And Japanese Patent Application Laid-Open No. 57-85014 and
Japanese Patent No. 90341 discloses that the output of an optical signal is stopped when a photocoupler provided in an optical transmission line is pulled out or a substrate in an optical transmission device is pulled out, and light leaks from a connector portion to irradiate a person. A safety mechanism is disclosed to prevent this from happening.

[0004]

However, since these are all personal safety mechanisms in an optical fiber transmission line, there is a problem that they cannot be applied to a personal safety device for laser light in an optical space transmission line having no connector. Was.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide an optical space transmission apparatus capable of preventing a laser beam used for spatial transmission of information from irradiating a person or the like. Is what you do.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a transmitting unit for outputting a parallel light beam modulated based on a predetermined information signal, and a light receiving unit for receiving the light beam. A spatial light transmission device including a receiving unit for demodulating, a light source provided in one of the transmitting unit and the receiving unit, and outputting infrared light for obstacle detection along the light beam; and the transmitting unit. And a light receiving intensity detecting means for receiving the infrared light and detecting the light receiving intensity of the infrared light, and the light beam is provided based on a detection result of the light receiving intensity detecting means. Control means for outputting or stopping, a single light source for outputting the infrared light is arranged on the same axis as the light beam of the parallel light, and the infrared light is gradually out of the radius of the light beam. Spread to Circumference of the light beam with a spread angle Yo
And the received light intensity detecting means is arranged on the same axis as the light beam, and the infrared light around the light beam is converged by an infrared light converging lens to thereby receive the received light intensity detecting means. The light is condensed at a point.

[0007]

According to the optical space transmission apparatus of the present invention, the received light intensity of the infrared light for obstacle detection output from the light source along the light beam is detected by the received light intensity detecting means, so that the infrared light is transmitted. The presence / absence of an obstacle that blocks light is detected. When the obstacle is detected, the output of the light beam is stopped by the control means, and when the removal of the obstacle is detected, the light beam is output again by the control means. Accordingly, when there is an obstacle to block the light beam, the output of the light beam can be stopped before the obstacle is irradiated with the light beam.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a transmission unit of a free-space optical transmission apparatus according to one embodiment of the present invention in a partial block diagram, FIG. 2 is an explanatory diagram showing an arrangement state of a light emitting diode shown in FIG. FIG. 4 is a block diagram showing a partial configuration of a receiving unit of the free-space optical transmission apparatus according to one embodiment of the present invention.
FIG. 4 is an explanatory diagram showing an arrangement state of a focusing lens and a photodetector for laser light and infrared light shown in FIG.

In the transmission unit 1 shown in FIG. 1, for example, an analog signal such as a video signal is converted into a frequency pre-modulation unit (PFM-M
D) 11, and a digital signal such as an audio signal passes through an encoding unit (CMI-CODEC) 12 and a laser driver (LD drive) of an electric-optical conversion unit (E / O) 13
er) 131.

A laser driver 131 modulates a laser beam LB output from a laser diode 132 based on a signal sent from the frequency pre-modulator 11 or the encoder 12, and the modulated laser beam LB is The beam is shaped into a parallel light beam (light beam) by the collimator lens 14 and transmitted to space.

The laser beam LB output from the laser diode 132 is received by a photodetector 133, and a signal corresponding to the amount of received light, ie, a laser power, is transmitted from the photodetector 133 to an auto power controller (APC) 13
4 is input. And the auto power controller 1
34 performs feedback control via the laser driver 131 based on the signal from the photodetector 133 so as to stabilize the laser power of the laser beam LB output from the laser diode 132.

A light emitting diode (LED) 15 is provided on the optical axis of the laser beam LB passing through the collimating lens 14, as shown in FIG. This light emitting diode 15 is driven by a signal from a laser driver 131 modulated by the IM modulator 16 as shown in FIG. 1, and is directed in the same direction as the laser beam LB to detect an obstacle. R
B1 emits light with an appropriate spread angle. For this reason,
The laser beam LB that has passed around the light emitting diode 15 becomes a substantially donut-shaped beam light in cross section, and the surrounding area is surrounded by infrared light RB1 for obstacle detection emitted from the light emitting diode 15. Shape.

Reference numeral 17 in FIG. 1 denotes a light detection beam emitted from a light emitting diode (LED) 31 of the receiving unit 3 to be irradiated with infrared light RB2 for controlling the output of the laser beam LB. Reference numeral 18 denotes an amplifier (IV) for amplifying the output of the photodetector 17. Further, reference numeral 19 in FIG. 1 is a security circuit that detects the presence or absence of an obstacle that blocks the optical path of the laser beam LB based on the output level of the photodetector 17 amplified by the amplifier 18.

When the output level of the photodetector 17 amplified by the amplifier 18 exceeds a predetermined value, the security circuit 19 determines that there is an obstacle to block the optical path of the laser beam LB. Act on
Laser diode 132 through laser driver 131
The output of the laser beam LB from is stopped.

On the other hand, in the receiving unit 3 shown in FIG. 3, the laser beam LB from the transmitting unit 1 has a substantially annular cross section.
Through a laser beam converging lens 32 disposed on the optical path and having a focal length of f1 for the first photoelectric conversion unit (O / O).
E: 1) The light is incident on the 33 photodetectors 331 (see FIG. 4). A signal output from the light detection element 331 in response to the incidence of the laser light LB is amplified by an amplifier (IV) 332 and input to an auto gain controller (AGC) 333, where the signal level is adjusted to be constant.

After that, a band-pass filter (BP)
F) In 334, frequency components other than the predetermined frequency band are cut, and a part is output to the comparator 38, and an analog signal component such as a video signal is converted into a frequency demodulator (PFM-DEM) in the remaining part. The digital signal components such as audio signals pass through a decoding unit (CMI-CODEC) 35 and are output to external devices such as televisions.

In the receiving unit 3 shown in FIG. 3, an infrared light RB1 for detecting an obstacle, which is transmitted so as to surround the laser light LB from the transmitting unit 1, is provided on the optical path thereof with a converging lens for laser light. The second photoelectric conversion unit () is disposed in a donut shape so as to surround the second focusing lens 32 and has a focal length f2 longer than the focal length f1 of the focusing lens 32 for laser light. O / E: 2) 37
(See FIG. 4).

A signal output from the light detection element 371 in response to the incidence of the infrared light RB1 for obstacle detection is supplied to an amplifier (I
V) amplified at 372 and gained by the auto gain controller (A
GC) 373, where the first photoelectric conversion unit 33
In conjunction with the automatic gain controller 333, the signal level is adjusted to be constant. After that, frequency components other than the predetermined frequency band are cut by the band pass filter (BPF) 374 and output to the comparator 38.

In the comparator 38, the laser light LB output from the band-pass filter 334 of the first photoelectric conversion unit 33 and the band-pass filter 374 of the second photoelectric conversion unit 37 is output.
The level of the signal corresponding to the reception intensity of the infrared light RB1 is compared with the level of the signal corresponding to the reception intensity of the infrared light RB1 for obstacle detection. When the level of the signal is higher, a low-level signal is output. On the other hand, when the signal level corresponding to the reception intensity of the infrared light RB1 is lower, that is, when the reception intensity of the infrared light RB1 for obstacle detection is lower than the reception intensity of the laser light LB, the comparison is performed. The device 38 outputs a high level signal.

The low-level or high-level signal output from the comparator 38 is input to an IM modulator 39,
Here, the drive signal input to the light emitting diode 31 for transmitting the infrared light RB2 for controlling the output of the laser light LB is modulated by the low or high level comparator output.

In this embodiment, the light emitting diode 15 of the transmission unit 1 corresponds to a light source, and the laser driver 131, the auto power controller 134,
The security circuit 19, the light emitting diode 31 and the comparator 38 of the receiving unit 3 correspond to control means, and the second photoelectric conversion unit 37 of the receiving unit 3 corresponds to light receiving intensity detecting means.

Next, the operation of controlling the emission of the laser beam LB in the optical space transmission apparatus according to the present embodiment having the above configuration will be described. First, the laser diode 1 of the transmission unit 1
32, the laser beam LB for information transmission is output from the light emitting diode 15 and the infrared light RB for obstacle detection is output from the light emitting diode 15.
1 is output, and the photodetectors 331, 3 of the receiving unit 3 are output.
A signal having a level corresponding to the received light intensity of the laser light LB and the infrared light RB <b> 1 incident on the output 71 is output from the band-pass filter 334 of the first photoelectric conversion unit 33 and the band-pass filter of the second photoelectric conversion unit 37. 374 output.

Here, as shown in FIG. 5A, when there is no obstacle on the optical path between the laser beam LB and the infrared beam RB1 for obstacle detection, the first and second photoelectric conversion units 33 are provided. , 37
Output from the band-pass filters 334 and 374 of
A signal having a level corresponding to the received light intensity of the laser light LB and the infrared light RB1 for obstacle detection is transmitted to the auto gain controller 333 of the first photoelectric conversion unit 33 and the auto gain of the second photoelectric conversion unit 37 linked thereto. It is adjusted to a predetermined level (200 mV in this embodiment) by the controller 373. In such a state where there is no obstacle, FIG.
As shown in (b) and (c), the bandpass filter 37
There is no difference between the levels of the signals A and B output from 4,334 (AB = 200 mV-200 mV = 0 mV). Therefore, the comparator 38 outputs a low level signal.

Then, the infrared light RB2 having a low received light intensity modulated by the low level signal is emitted from the light emitting diode 31.
And is received by the light detection element 17 of the transmission unit 1. The output of the light detecting element 17 is amplified by an amplifier 18 and input to a security circuit 19. Since the level of the input signal is lower than a predetermined value, the security circuit 19 generates a laser beam LB and a red light for obstacle detection. It is detected that there is no obstacle on the optical path with the external light RB1, and the output of the laser light LB is continued.

In a state where a disturbance having a substantially uniform distribution density, such as smoke S shown in FIG. 6A, is on the optical path between the laser light LB and the infrared light RB1 for obstacle detection, FIG. (B),
As shown in (c), the band pass filters 374, 33
4, the levels of the output signals A and B both decrease (100 mV in this embodiment), and the band-pass filter 374
There is no difference in the level of the signal output from the 334 (AB)
= 100 mV-100 mV = 0 mV). Therefore, a low-level signal is output from the comparator 38, and thereafter, the operation is the same as that shown in FIG.

Further, when a moving obstacle such as a pedestrian M shown in FIG. 7A crosses the optical path between the laser light LB and the infrared light RB1 for detecting the obstacle, the moving obstacle M is a laser. The optical path of the infrared light RB1 for obstacle detection is blocked before the light LB. Then, since the level adjustment by the auto gain controller 373 is performed in conjunction with the auto gain controller 333 of the first photoelectric conversion unit 33, the level of the output signal B from the band-pass filter 334 remains unchanged (200 mV in this embodiment). However, the level of the output signal A from the band-pass filter 374 decreases (100 mV in this embodiment). Therefore, as shown in FIGS. 7B and 7C, a difference of 100 mV occurs between the levels of the signals A and B output from the band-pass filters 374 and 334 (BA = 200 mV−100 mV = 100 mV). , The output signal level of the comparator 38 rebounds to a high level.

Then, the infrared light RB2 having a high light emission intensity modulated by the high level signal is emitted from the light emitting diode 31.
And is received by the light detection element 17 of the transmission unit 1. The output of the light detection element 17 is amplified by the amplifier 18 and input to the security circuit 19. Since the level of the input signal is higher than a predetermined value, the security circuit 19 outputs the infrared light RB1 for obstacle detection. The presence of an obstacle on the optical path is detected, and the output of the laser beam LB from the laser diode 132 is stopped by the laser driver 131 via the auto power controller 134.

As described above, in the optical space transmission apparatus according to the present embodiment, when an obstacle approaches the optical path of the laser light LB, the red light for detecting the obstacle is provided before the obstacle interrupts the optical path of the laser light LB. Since the output of the laser beam LB is stopped when the optical path of the external light RB1 is blocked, it is possible to prevent the laser beam LB from being irradiated on an obstacle such as a human. Then, when the obstacle moves away and does not block the infrared light RB1, this corresponds to the case shown in FIG. 5, and the transmission of the laser light LB can be recovered again by recovering the output.

In the optical space transmission apparatus according to the present embodiment, signals of levels corresponding to the light receiving intensities of the laser light LB and the infrared light RB1 incident on the light detecting elements 331 and 371 of the receiving unit 3 are compared. Since the output of the laser light LB is stopped when there is a difference between the received light intensities of the laser light LB and the infrared light RB1, the output of the laser light LB may be erroneously stopped due to disturbance such as smoke S. Can not be.

In this embodiment, a light emitting diode 15 for outputting an infrared light RB1 for detecting an obstacle along the light beam LB is provided in the transmitting unit 1, and the light emitting diode 15 receives the infrared light RB1. Although the configuration in which the second photoelectric conversion unit 37 for detecting the received light intensity is provided on the receiving unit 3 side has been described,
A light source for outputting an infrared light for detecting an obstacle;
The transmission unit 1 may be provided with a unit that receives infrared light for detecting an obstacle and detects the intensity of the received infrared light.

In the present embodiment, signals of levels corresponding to the light receiving intensities of the laser light LB and the infrared light RB1 incident on the light detecting elements 331 and 371 of the receiving unit 3 are compared, and the laser light LB and the red light are compared. The output of the laser beam LB is stopped when there is a difference in the received light intensity of the external light RB1, but only the received light intensity of the infrared light RB1 for obstacle detection is monitored, and the received light intensity of the infrared light RB1 is monitored. The output of the laser beam LB may be stopped when is decreased.

In order to feed back the received light intensity of the infrared light RB1 to the emission control of the laser light LB, in this embodiment, the output control infrared light RB2 output from the light emitting diode 31 of the receiving unit 3 is used. Although used, a feedback system using transmission means for wireless signals or the like may be constructed.

When the transmitting unit 1 is provided with a means for receiving infrared light for detecting an obstacle and detecting the received light intensity, a security circuit 19 is connected to the means by wire to construct a feedback system. May be.

Further, in this embodiment, a light emitting diode 15 for outputting an infrared light RB1 for detecting an obstacle is arranged on the optical axis of the laser light LB, and the area around the laser light LB is a red light for detecting an obstacle. Although surrounded by the external light RB1, for example, as shown in FIG. 8A, a red light for obstacle detection is provided around the laser diode 132 of the transmission unit 1 in the same direction as the laser light LB to be output. A plurality of light emitting diodes 15 that output the external light RB1 may be provided.

In response to this, as shown in FIG. 8 (b), the receiving unit 3 side also receives the infrared light RB1 around the light detecting element 331 where the laser light LB is incident. A plurality of detection elements 371 may be provided. With this configuration, as shown in FIG. 8C, the infrared light converging lens 36 (see FIG. 4) on the receiving unit 3 side can be omitted.

In addition, the infrared light RB1 for obstacle detection and the infrared light RB2 for output control are used for alignment between the transmission unit 1 and the reception unit 3 (correction of the deviation of the optical axis of the laser light LB). It may be used also as the infrared light to be used.

[0037]

As described above, according to the present invention, the received light intensity of the infrared light for detecting an obstacle outputted from the light source along the light beam is detected by the received light intensity detecting means, whereby the infrared light is detected. The presence or absence of an obstacle that blocks light is detected, and when the obstacle is detected, the output of the light beam is stopped by the control means. Thus, when there is an obstacle to block the light beam, the output of the light beam can be stopped before the obstacle is irradiated with the light beam, and the laser beam used for spatial transmission of information can be stopped. Can be prevented from irradiating a person or the like.

Further, even when disturbance such as smoke S having a substantially uniform distribution density flows into the optical path between the laser beam between the transmitting unit and the receiving unit and the infrared light for detecting an obstacle, the spatial transmission of information is possible. Can be greatly reduced. Furthermore, to surround the laser light with infrared light,
For example, a small but dangerous laser such as a dental mirror can be reflected to detect all dangerous objects.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a transmission unit of an optical free space transmission apparatus according to one embodiment of the present invention in partial blocks.

FIG. 2 is an explanatory diagram showing an arrangement state of a light emitting diode 15 shown in FIG.

FIG. 3 is a block diagram illustrating a receiving unit of the free-space optical transmission apparatus according to one embodiment of the present invention, with partial blocks.

FIG. 4 is an explanatory diagram showing the arrangement of a focusing lens and a photodetector for laser light and infrared light shown in FIG. 3;

FIG. 5 is a diagram showing a relationship between a spatial state between the transmission unit and the reception unit shown in FIGS. 1 and 3 and a reception intensity of laser light and infrared light for detecting an obstacle, and FIG. FIG. 5 (b) is a waveform diagram showing a detection signal A of the infrared light RB1 from the bandpass filter 374, and FIG. 5 (c) is a laser beam LB from the bandpass filter 334. 3 is a waveform diagram showing a detection signal B of FIG.

FIG. 6 is a diagram showing a relationship between a spatial state between the transmitting unit and the receiving unit shown in FIGS. 1 and 3 and a reception intensity of laser light and infrared light for detecting an obstacle, and FIG. FIG. 6 is an explanatory view showing a state in which there is a disturbance with a substantially uniform distribution density.
6B is a waveform diagram showing a signal A from the bandpass filter 374, and FIG. 6C is a waveform diagram showing a signal B from the bandpass filter 334.

FIG. 7 is a diagram showing a relationship between a spatial state between the transmission unit and the reception unit shown in FIGS. 1 and 3 and a reception intensity of laser light and infrared light for obstacle detection, and FIG. FIG. 7B is a diagram illustrating a state in which a moving obstacle approaches, FIG. 7B is a waveform diagram illustrating a signal A from the band-pass filter 374, and FIG.
(C) is a waveform diagram showing a signal B from the bandpass filter 334.

FIG. 8 is a diagram showing a main part of an optical free space transmission apparatus according to another embodiment of the present invention. FIG. 8A is a front view showing a main part of a transmission unit according to this embodiment, and FIG. FIG. 8B is a front view showing a main part of the receiving unit according to this embodiment, and FIG. 8C is a diagram showing the transmission state of laser light between the transmitting unit and the receiving unit shown in FIGS. 8A and 8B. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitting unit 3 Receiving unit 11 Frequency premodulation part 12 Encoding part 13 Electro-optical conversion part 14 Collimating lens 15 Light emitting diode (light source) 16 IM modulator 17 Photodetection element 18 Amplifier 19 Security circuit (control means) 31 Light emitting diode (Control means) 32 Convergence lens for laser light 33 First photoelectric conversion unit 34 Frequency demodulation unit 35 Combination unit 36 Convergence lens for infrared light 37 Second photoelectric conversion unit (light receiving intensity detecting means) 38 Comparator (control means) 39 IM modulator 131 laser driver (control means) 132 laser diode 133 photodetector 134 auto power controller (control means) 331,371 photodetector 332,372 amplifier 333,373 auto gain controller 334,374 band pass filter LB laser Light (light beam RB1, RB2 infrared light f1, f2 the focal length S smoke M pedestrian

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 10/00-10/28

Claims (1)

(57) [Claims] 1. An optical space transmission apparatus comprising: a transmission unit that outputs a light beam of parallel light modulated based on a predetermined information signal; and a reception unit that receives and demodulates the light beam. And a light source that is provided in one of the receiving units and outputs infrared light for obstacle detection along the light beam, and is provided in one of the other of the transmitting unit and the receiving unit, and outputs the infrared light. Light-receiving intensity detecting means for receiving and detecting the light-receiving intensity of the infrared light; and control means for outputting or stopping the light beam based on a detection result of the light-receiving intensity detecting means, and outputting the infrared light. A single light source is arranged on the same axis as the light beam of the parallel light, and the infrared light has a divergence angle such that the infrared light gradually spreads outside the radius of the light beam.
And the light reception intensity detecting means is arranged on the same axis as the light beam, and the infrared light around the light beam is converged by an infrared light converging lens to detect the light reception intensity. An optical space transmission device characterized in that the light is condensed on a means.