JP3604019B2 - Optical space transmission equipment - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an optical space transmission apparatus using laser light as a signal light source, and more particularly to an optical space transmission apparatus that facilitates optical axis adjustment of an apparatus using a laser whose oscillation wavelength is in the infrared region.
[0002]
[Prior art]
A conventional free-space optical transmission device will be described with reference to FIGS.
First, with the conventional optical space transmission device, information to be transmitted is converted into intensity modulation of light, and the intensity-modulated light is emitted into the atmosphere toward the receiving side, and the modulated light incident on the receiving side is demodulated. Thus, transmission of a desired information signal is performed through the air space.
[0003]
That is, as shown in FIG. 5, bidirectional optical space transmission performed between one optical space transmission device 50A and the other optical space transmission device 50B is transmitted from one optical space transmission device 50A (or 50B). The laser light modulated by the signal is emitted (emitted light L1) via the lens 1D, and the similarly modulated laser light (incident light L2) from the other optical space transmission device 50B (or 50A) is passed through the lens 1D. This is realized by receiving light through the light source.
[0004]
Next, an example of an optical space transmission apparatus using a visible light semiconductor laser invented by the present applicant and already filed as Japanese Patent Application No. 5-353410 is shown in FIG. Will be explained. The optical space transmission apparatus shown in the figure has a configuration in which transmission and reception functions are integrated, and shows an example of a configuration in which bidirectional information transmission can be performed by installing exactly the same apparatus in opposition. ing.
[0005]
First, the basic configuration of the optical system is a semiconductor laser 3C as a light source, a lens 1A for converting a laser beam into a parallel beam, a polarizing beam splitter 2 for separating light, a lens 1B for narrowing the laser beam again, and a lens 1D for emitting a laser beam. , And a lens 1C for condensing incident light on the photodetecting element 4.
[0006]
Next, in the operation as a transmitter, information to be transmitted is converted into a transmission signal by a transmission signal processing circuit 10 and input to a driver 11 for driving the semiconductor laser 3C. The laser beam of the semiconductor laser 3C driven by the driver 11 according to the transmission signal is expanded by the lens 1A into a beam having a constant diameter, passes through the polarizing beam splitter 2, is again narrowed down by the lens 1B, and is finally emitted. Is converted into substantially parallel outgoing light L1 by the large-diameter lens 1D for transmission to the partner device.
[0007]
The operation as a receiver is as follows. The laser beam sent from the partner device, that is, the incident light L2, is converted into a constant diameter by the large-diameter lens 1D and the lens 1B, and is bent by the polarizing beam splitter 2 before the lens. The light is condensed on the light detecting element 4 by 1C. The optical signal is converted into an electric signal by the photodetector 4, the signal is shaped by the preamplifier 13, the AGC 14 and the like, and the received signal is restored to the original information by the received signal processing circuit 15.
[0008]
The above-described optical space transmission apparatus employs an automatic tracking method for automatically capturing the other party's apparatus and keeping the transmission optical axes of the two apparatuses in alignment. In this automatic tracking method, when the method of controlling the attitude by moving the entire optical system is adopted, since the control performance largely depends on the mass of the optical system, the smaller the mass, the higher the optical space transmission with the higher automatic tracking performance. Can be a device.
[0009]
Here, the dominantly large optical system is the exit lens 1D, and by reducing this, the mass of the optical system can be effectively reduced. The oscillation intensity of the semiconductor laser 3C must be increased. However, for environmental hygiene, the power density per unit area with respect to the laser oscillation wavelength is specified, and the power density is limited to a small value in the visible light band used in the above-described conventional apparatus.
[0010]
This is stipulated from the viewpoint of eye protection, and the background will be described with reference to FIG.
This figure shows the relationship between the transmittance of light from the cornea to the fundus and the wavelength of the absorptance at the fundus, both of which are 100% above the cornea. According to FIG. 7, almost no light enters the eye with ultraviolet rays or far infrared rays having a wavelength longer than 1500 nm. On the other hand, the cornea and the crystalline lens are transparent with respect to visible light and near-infrared light of approximately 400 nm to 1200 nm, and the light intensity per unit area at the fundus becomes extremely large due to the focusing action of the crystalline lens. Also, it can be seen that the light absorptivity at the fundus is large for blue light, but decreases as the wavelength increases, and the absolute absorption of energy becomes extremely small even when the light reaches the fundus.
[0011]
Therefore, from such a viewpoint, the allowable power density with respect to the wavelength of the laser is specified for environmental hygiene for the eyes. For example, the allowable power density of a unit area having a wavelength of 780 to 830 nm, that is, the maximum allowable exposure amount, which is conventionally used, is 0.32 mW / cm ² in a long exposure state. On the other hand, that of a semiconductor laser of 1400 nm to 1600 nm is 100 mW / cm ^2, which is much larger than that of a wavelength of 780 nm to 830 nm.
[0012]
Therefore, since the power density can be increased by using the above-mentioned semiconductor laser of 1400 nm to 1600 nm, that is, the optical system can be reduced, so that the C / N ratio can be improved, the optical space transmission apparatus can be downsized, and automatic tracking control can be performed. Performance can be improved.
[0013]
Now, an optical device called a collimator scope has been developed and mounted on a conventional optical space device by the present inventors for adjusting the optical axis and maintaining the line (hereinafter, this optical device is referred to as a “collimator scope”). Described). As schematically shown in FIG. 8, the collimator scope 160 includes prisms 25A and 25B, the imaging optical system 7, and the imaging device 8 as main members. In some cases, a half mirror is used instead of the prisms 25A and 25B. As described later, the imaging device 8 needs to image the background of the partner device side in conformity with human vision, and therefore employs a silicon CCD (Charge Coupled Device) generally used in video cameras and the like. ing.
[0014]
The function of the collimating scope 160 is to simultaneously capture the outgoing light L1 from the own device, the incident light L2 coming from the other device, and the background image of the other device, and the outgoing light L1 from the own device reaches any position on the other device. The self-device detects whether or not the optical axis is adjusted, and adjusts and holds the optical axis based on this information.
[0015]
Further, the operation of the collimating scope 160 will be described with reference to FIG.
First, light coming from the partner device side passes through the prism 25B and is condensed on the image pickup device 8 by the image pickup optical system 7. This situation is shown in FIG. 9A, in which the other party, that is, the receiving device 30 and its background are photographed.
[0016]
Next, the outgoing light L1 from the apparatus becomes substantially parallel light by the lens 1D, and a part thereof is reflected by the prism 25A and condensed on the image pickup device 8 through the image pickup optical system 7. This state is shown in FIG. 9B, and is captured as a bright point 31 in the emission direction.
[0017]
The image actually displayed on the monitor (not shown) is a composite of FIGS. 9A and 9B shown in FIG. 9C. Can be recognized at a glance at the other party's location where the outgoing light L1 has reached. Therefore, by moving the bright point 31 in the direction indicated by the arrow Y by adjustment of its own device and matching it with the receiving device 30, the optical axis can be matched, that is, the line can be connected. The operation of matching the optical axes can be automatically performed based on the image data described above.
[0018]
However, when a semiconductor laser having a wavelength of 1400 nm to 1600 nm is used as described above, the collimating scope 160 uses the characteristics of the imaging device 8 to generate the background light that is visible light and the emission light L1 and the incident light L2 that are infrared light. There was a problem that it was not possible to capture images at the same time, and it was not possible to obtain positional information of these lights as it was.
[0019]
In addition, in order to solve a visual problem, it has been widely practiced to combine infrared light and visible light and make two optical axes coincide with each other. For example, it is well known that a guide HeNe beam is coaxially superimposed on a processing YAG laser beam. However, it is extremely difficult to improve the overlay accuracy to a level required for optical space transmission by the conventional technology. For example, as described in Japanese Patent Application Laid-Open No. 63-254405, two laser light sources are modulated through modulating means of different frequencies, the degree of superposition is checked by a split photodetector, and control is performed. However, the scale is large and it is difficult to adopt it in an optical space transmission device.
[0020]
[Problems to be solved by the invention]
As described above, in order to improve the performance of automatic tracking control along with miniaturization of the optical system, by using an infrared semiconductor laser as the light source for main signal transmission, the imaging device having the same sensitivity as vision or vision is used. There is a problem that the laser light cannot be recognized and it becomes difficult to adjust the optical axis between the devices.
Therefore, the present invention has been made in view of such a problem, and an object of the present invention is to make it easy to adjust the optical axis between optical space transmission apparatuses using infrared light as a main signal transmission light source. It is.
[0021]
[Means for Solving the Problems]
The present invention has been devised in order to solve the problems of the optical space transmission apparatus, and employs the following method as a means for solving the problem.
[0022]
The laser light of the semiconductor laser oscillating at another wavelength at which the image sensor of the collimator scope has sensitivity through the optical coupler is combined with the infrared semiconductor laser light modulated by the information to be transmitted. Is emitted toward the partner device, and the partner device detects the light having the sensitivity of the image sensor among the transmitted combined light and adjusts the optical axis.
[0023]
A wavelength conversion element that receives infrared light and converts it into another wavelength with which the imaging element has sensitivity is provided in the optical path of the collimator scope, and the converted light is detected to perform optical axis adjustment. Solve.
[0024]
[Action]
ADVANTAGE OF THE INVENTION According to the optical space transmission apparatus of this invention, since the problem which cannot recognize the infrared laser beam for transmission with a visual or silicon image sensor can be solved by a simple method, optical axis adjustment between apparatuses can be solved. The optical axis adjustment between the apparatuses can be automatically performed using the technology of the collimator scope already developed by the inventors of the present invention.
[0025]
Further, as described above, since the infrared laser light having a large maximum allowable exposure amount can be used, the size of the apparatus is reduced and the performance of the automatic tracking control is improved.
[0026]
【Example】
An optical space transmission device according to the present invention will be described with reference to FIGS.
The gist of the present invention is to use, as a light source, a semiconductor laser having a power density per unit area that is relatively large, for example, a semiconductor laser having a wavelength of 1400 nm to 1600 nm, and to easily adjust the optical axis between devices by using a collimating scope technique. Therefore, the basic configuration of the optical space transmission apparatus and the transmission system thereof are the same as those of the conventional example, and the same components are denoted by the same reference numerals and the description of the configuration and functions will be omitted. Is omitted.
[0027]
Further, as described above, the image pickup element used in the collimator scope of the optical space transmission apparatus according to the present invention needs to image the background of the partner apparatus in accordance with human vision. A silicon image sensor (for example, a CCD) having the following is used. Therefore, in order to recognize a laser beam having a wavelength of 1400 nm to 1600 nm for main signal transmission, it is necessary to obtain light having a wavelength which is coaxial with the laser beam and has a sensitivity to the image sensor.
[0028]
Description of Related Items In FIG. 1, a semiconductor laser 3A that oscillates at a wavelength of 1400 nm to 1600 nm for main signal transmission is used as a first light source, and oscillates at a wavelength at which an image pickup device (for example, a CCD) made of visible light or silicon has sensitivity. With the semiconductor laser 3B to be opened as the second open state, the respective laser beams are put into optical fibers 9A and 9B, and the output ends thereof are connected to the optical coupler 5. At this time, the two laser lights are combined in the optical coupler 5, but in order not to waste the power of the laser light for transmitting the main signal, the optical fiber 9A is connected to the main port and the optical fiber 9B is connected to the width port. It is desirable to reduce the coupling between them, that is, to increase the junction loss (for example, 3 dB or more).
[0029]
The two laser lights combined in the optical coupler 5 again enter the optical fiber 9C, are guided to the focal point of the lens 1A by the optical fiber 9C as shown in FIG. And is emitted as outgoing light L1.
[0030]
As described in the conventional example, the collimator scope 160 is provided to capture the outgoing light L1 from the lens 1D and the incident light L2 from the partner device, and a part of the outgoing light L1 is provided by the prism 25A forming the combining prism 6A. The light is reflected and condensed on the image pickup device 8 by the image pickup optical system 7. At this time, the laser light of the semiconductor laser 3B combined with the emission light L1 is detected based on the sensitivity characteristics of the imaging device 8, and therefore, the emission direction of the main signal transmission semiconductor laser 3A, which is one of the combined lights, is recognized. be able to. This state is the same as that shown in FIG.
[0031]
Next, light from the background including the counterpart device passes through the prism 25B and is also condensed on the image pickup device 8 by the image pickup optical system 7. This situation is the same as that shown in FIG.
[0032]
The image actually displayed on the monitor (not shown) is that shown in FIG. 9C, from which the relative positional relationship between the partner device and the emitted light L1 can be recognized. Therefore, it is possible to easily adjust the optical axis between the devices of the optical space transmission device from the information on the positional relationship.
[0033]
Furthermore, by using the second laser light to be synthesized, it is possible to carry, for example, a signal for controlling the device or communicating between the devices independently of the main signal of the first laser light. Therefore, the quality of the main signal can be improved, and the number of lines of the main signal can be increased.
[0034]
Example 1
Next, a first embodiment of the present invention will be described with reference to FIGS. 2 (a), 3 (a) and 3 (b).
In this embodiment, the laser beam energy of the semiconductor laser 3A oscillating at a wavelength of 1400 nm to 1600 nm for main signal transmission is used to convert the laser beam into a wavelength at which a visible or silicon image sensor has sensitivity, and the emission direction of the emission light L1. Is to recognize.
[0035]
Reference numeral 100 in FIG. 2A denotes a reflection-type light wavelength conversion element, which is formed by including photoluminescence particles 20 in a long-wavelength light absorbing material 21 and whose surface 18 is smoothed so that light is not scattered. Have been. A light reflecting member 22 is adhered to the back surface 19 as a substrate and reflects light on this surface.
[0036]
The photoluminescent particles 20 emit visible light when electrons excited by short-wavelength light energy are combined with holes by irradiation of infrared light. Accordingly, by using the laser light energy having a wavelength of 1400 nm to 1600 nm for transmitting the main signal, a wavelength light having a sensitivity of a visible or silicon image sensor is obtained.
[0037]
Next, an apparatus for recognizing the emission direction of the emitted light L1 using the reflective light wavelength conversion element 100 will be described with reference to FIG. FIG. 3A shows the optical configuration of the present embodiment. The light source is only the semiconductor laser 3A, and the configuration of the combining prism is changed to that shown in FIG. 3B. 1 is the same as FIG. The combining prism 6B is composed of a prism 25A and a prism 25B and a reflection type optical wavelength conversion element 100 sandwiched between the prisms 25A and 25B.
[0038]
The laser beam of the semiconductor laser 3A passes through the optical system and is emitted from the lens 1D toward the partner device. At this time, a part of the emitted light L1 is taken into the collimator scope 160 from the prism 25A, reflected, and condensed on the image pickup device 8 by the image pickup optical system 7. At this time, in the reflection type optical wavelength conversion element 100 of the combining prism 6B, the visible or silicon image pickup element emits wavelength light having sensitivity by the laser light energy of the semiconductor laser 3A, and the image pickup element 8 picks up the image. This state is the same as that shown in FIG.
[0039]
Next, the background light including the partner device passes through the prism 25 </ b> B and is also condensed on the imaging device 8 by the imaging optical system 7. This situation is the same as that shown in FIG.
[0040]
The image actually displayed on the monitor (not shown) is that shown in FIG. 9C, from which the relative positional relationship between the partner device and the emitted light L1 can be recognized. Therefore, it is possible to easily adjust the inter-device optical axis of the optical space transmission device from the information on the positional relationship.
[0041]
Example 2
A second embodiment of the present invention will be described with reference to FIGS.
This embodiment uses a transmission type optical wavelength conversion element 101 (to be described later in detail) using photoluminescence particles. The optical configuration of the optical space transmission apparatus is substantially the same as that of the first embodiment shown in FIG. They are the same, and are different in that a transmission type optical wavelength conversion element 101 is provided immediately before the imaging element 8 instead of using the reflection type optical wavelength conversion element 100 in the combining prism.
[0042]
That is, also in this embodiment, the laser light energy of the semiconductor laser 3A which oscillates at a wavelength of 1400 nm to 1600 nm for transmitting the main signal is converted into a wavelength having a sensitivity of a visible or silicon image sensor, and the emission light L1 is It is intended to recognize the emission direction.
[0043]
First, the transmission-type light wavelength conversion element 101 shown in FIG. 2B is formed by including the photoluminescence particles 20 in the long-wavelength absorption material 21, and the surface 18 is smoothed so that light is not scattered. . Further, on the back surface 19, a light transmitting member 23 from visible light to a wavelength of 1600 nm is provided as a substrate. Therefore, by utilizing the laser light energy having a wavelength of 1400 nm to 1600 nm by the photoluminescent particles 20, a wavelength at which a visible or silicon image sensor has sensitivity is obtained and light is transmitted.
[0044]
Next, an apparatus for recognizing the emission direction of the emission light L1 using the transmission type optical wavelength conversion element 101 will be described with reference to FIG. FIG. 4 shows a configuration of the imaging optical system 7, the imaging element 8, and the transmission type optical wavelength conversion element 101 in the collimator scope 160 which is a main part of the present embodiment.
[0045]
The method of recognizing the emission direction of the emitted light L1 in this embodiment will be described with reference to FIG. 3A. The laser light of the semiconductor laser 3A is emitted from the lens 1D toward the partner device through the optical system. At this time, a part of the emitted light L1 is taken into the collimator scope from the prism 25A, reflected, and condensed on the image pickup device 8 by the image pickup optical system 7. At this time, the transmission type optical wavelength conversion element 101 set on the mounting member 9 immediately before the image pickup element 8 emits visible or silicon wavelength light having sensitivity by the laser light energy of the semiconductor laser 3A, and the image pickup is performed. An image is captured by the element 8. This state is the same as that shown in FIG.
[0046]
Next, the background light including the partner device passes through the prism 25 </ b> B and is also condensed on the imaging device 8 by the imaging optical system 7. This situation is the same as that shown in FIG.
[0047]
The image actually displayed on the monitor (not shown) is that shown in FIG. 9C, from which the relative positional relationship between the partner device and the emitted light L1 can be recognized. Therefore, it is possible to easily adjust the optical axis between the devices of the optical space transmission device from the information on the positional relationship.
[0048]
As described above, in the first embodiment and the second embodiment, the example in which the present invention is applied to the optical space transmission apparatus having the integrated transmission and reception that can perform transmission and reception with one apparatus has been described. It goes without saying that the present invention may be applied to a device in a separate form.
[0049]
Although the photoluminescence material is in the form of powder, the surface 18 of the transmission-type light wavelength conversion element 101 is formed to be smooth, and light scattering due to the photoluminescence material is used by disposing it very near the front surface of the imaging element 8. It can be reduced to the extent that there is no problem.
[0050]
【The invention's effect】
Even if a laser beam having a wavelength of 1400 nm to 1600 nm is used as a light source, a light source that can be visually recognized or can be easily recognized by a silicon image sensor can be easily obtained, and thereby, the optical axis alignment between the devices can be easily performed. Can be done.
[0051]
In providing a servo mechanism for searching for and automatically tracking a partner device, which is extremely important in an optical space transmission device, a laser beam having a wavelength of a maximum allowable exposure of 1400 nm to 1600 nm is used. Therefore, the mass of the entire optical system can be reduced, so that the servo characteristics can be improved.
[0052]
In addition, since the laser light having the wavelength of 1400 nm to 1600 nm is used, there is an environmental health effect for eyes.
[0053]
Further, the second laser beam to be synthesized can be provided with, for example, a signal for controlling the apparatus or communicating between the apparatuses independently of the main signal, thereby improving the quality of the main signal, A large number of main signal lines can be secured.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining related matters.
FIGS. 2A and 2B are schematic cross-sectional views of a light wavelength conversion element used in the present invention, wherein FIG. 2A shows a reflection type light wavelength conversion element, and FIG. 2B shows a transmission type light wavelength conversion element.
3A and 3B are diagrams for explaining a first embodiment according to the present invention, wherein FIG. 3A shows an optical configuration thereof, and FIG. 3B shows a combined optical system used in the present embodiment.
FIG. 4 is a diagram for explaining a second embodiment according to the present invention.
FIG. 5 is a diagram illustrating a transmission state of the free-space optical transmission device.
FIG. 6 is a block diagram illustrating a basic configuration of a conventional optical free space transmission apparatus.
FIG. 7 is a diagram showing the transmittance of light entering the cornea of the eye to the fundus and the absorptance at the fundus.
FIG. 8 is a schematic diagram for explaining a collimator scope.
9A and 9B are diagrams for explaining the optical axis adjustment of the optical space transmission device using the collimator scope, where FIG. 9A is an image capturing the reception-side device, and FIG. The outgoing light indicates the outgoing direction to the receiving-side device, and (c) is an image captured by an actual collimating scope obtained by combining (a) and (b).
[Explanation of symbols]
Reference Signs List 1A-1D Lens 2 Polarization Beam Splitter 3A-3C Semiconductor Laser 4 Photodetector 5 Optical Coupler 6A, 6B Synthetic Prism 7 Imaging Optical System 8 Imaging Device 9A-9C Optical Fiber 10 Transmission Signal Processing Circuit 11 Driver 13 Preamplifier 14 AGC
Reference Signs List 15 received signal processing circuit 20 photoluminescence particles 21 long wavelength light absorbing material 22 light reflecting member 23 light transmitting members 25A, 25B prisms 50A, 50B optical space transmission device

Claims (4)

A transmitting means for transmitting the semiconductor laser by modulating the laser light of the semiconductor laser in accordance with a transmission signal and emitting the modulated laser light to the outside, and receiving and demodulating the modulated laser light incident from the outside; And a receiving means for obtaining a signal by using
The signal light source is constituted by a semiconductor laser having a wavelength of 1400 nm or more and 1600 nm or less, and this is used as a first light source,
A light source for intended to adjust the device between the optical axis of the optical atmospheric link system by converting the laser light obtained from the previous SL first light source into light having an image pickup element sensitivity due to visible light or silicon by the wavelength conversion element in the the obtained structure, an optical atmospheric link system according to claim <br/> to this as the second light source. Configuration it's the second light source, the first optical wavelength conversion device photoluminescence material formed by dispersing encompassed member for absorbing the laser light emitted by the light energy of the laser light obtained from a light source 2. The optical space transmission apparatus according to claim 1 , wherein: The optical wavelength converting element, light of claim 2, characterized in that together with the surface of the member that absorbs the light comprising the photoluminescence material smooth surface, provided with the light reflecting member on the rear surface Spatial transmission equipment. The optical wavelength converting element, with the surface of the member that absorbs the light comprising the photoluminescence material smooth surface, according to claim 2, characterized in that a visible light transmitting member on the back surface Optical space transmission equipment.

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