JP4984996B2 - Deflection device, condensing device using the same, and spatial light receiving device using the same - Google Patents

Description

  The present invention provides a deflecting device that guides incident light in a certain direction even when there is a change in the incident direction within a certain range, a condensing device that condenses light from the deflecting device, and light from the condensing device And a spatial light receiving device that guides an optical signal to an optical signal processing device.

  When performing spatial optical communication, when the transmission side is viewed from the reception side due to fluctuations in the air layer that is the propagation path of light, the direction of the transmission side, that is, the incident direction of light on the reception side is within a minute angle. It is known to be constantly shaking. This fluctuation in the incident direction makes it difficult to input incident light into an optical fiber having only a fine incident region.

  In order to cope with this fluctuation, there is known a device that has a tracking device that tracks the incident direction and a movable mirror, and that stably adjusts the movable mirror with a control signal from the tracking device and stably guides the light received to the optical fiber. Yes.

  Moreover, there exists patent document 1 as what made the structure which does not have said control part etc. by devising a condensing system. Patent Document 1 relates to an optical remote control receiver used in an optical space transmission system that performs device control such as lighting and data communication between terminals by spatial transmission using an optical signal in an indoor space such as an office or home. This is because an optical remote control receiver that can reduce the effects of optical noise by efficiently installing a filter that limits the incidence of optical noise to the optical remote control receiver and that also ensures a sufficient receivable distance. It is disclosed. This is a light receiving device composed of a wide-angle light-receiving lens that can receive an optical signal transmitted from a transmitter in a wide range, a light-receiving element that receives the optical signal condensed by the wide-angle light-receiving lens, and a signal amplification circuit. In an optical remote control receiver comprising a module and a filter for blocking optical noise due to illumination light, etc., a light quantity adjusting filter for attenuating the optical noise is inserted in the incident optical path of the optical noise such as illumination light Remote control receiver.

  Patent Document 2 discloses a distance measuring device that provides a compact multi-point distance measuring device without reducing distance measuring accuracy even for a wide angle of view. The light emitting system and the light receiving system are arranged in the base line length direction, and a plurality of spot lights are projected from the light projecting system toward the distance measuring object side along the base line length direction of the light emitting unit. In a multi-point distance measuring device that receives spot light reflected on the distance measuring object side by the position detection type light receiving system and measures the distance to the distance measuring object, the light receiving system includes a light receiving lens. And a light receiving element having a light receiving portion that receives light that has passed through the light receiving lens, and a reflecting member that reflects the spot light of the light emitting portion toward the light receiving portion.

  Patent Document 3 discloses a reflection measuring device that accurately measures the distance to the object to be measured in a wide angle range and is small and lightweight. First, the light receiving lens of the reflection measuring device is arranged in a blade shape by repeatedly circulating an annular short focal portion, intermediate focal portion, and long focal portion having different focal lengths from the outer periphery of the lens toward the center of the lens. A circular focus Fresnel lens. The short focal portion, the middle focal portion, and the long focal portion have longer focal lengths in this order. The short focal point condenses the refracted light from the light receiving lens at the center of the light receiving element when the incident angle of the incident light with respect to the light receiving lens is 0 degree, and the middle focal point receives the light receiving element when the incident angle is 4 degrees. Refracted light beam is collected at the center of the light-receiving element, and the long focal point collects refracted light beam at the center of the light receiving element when the incident angle is 8 degrees. Thereby, the received light quantity characteristic of the light receiving element with respect to the incident angle is flattened.

  Patent Document 4 discloses an optical coupling element and an optical coupling method capable of converting the spot size of the incident side light beam and the spot size of the output side light beam by orders of magnitude. This is because an optical coupling element that couples optical waveguide elements having different spot sizes has a modulation structure with a periodic refractive index at intervals similar to the wavelength of light used by the optical waveguide element. By using crystals, the spot size at the exit end is converted to a size different from the spot size at the entrance end.

  Non-Patent Document 1 describes a super collimator using a photonic crystal. In this super collimator, light is collected at the point of incidence on the photonic crystal and travels while being collected in the photonic crystal, but is scattered when emitted from the photonic crystal.

  As described above, in the conventional optical coupling device for guiding the optical space propagation signal to the photoelectric conversion element, there are those having an operation part and those having an operation part, but those having an operation part have a low response speed, I couldn't cope with fast changes. In addition, high-precision angle control is required.

  In addition, if the light condensing system is devised to have a structure that does not have a moving part such as a rotary mirror, the light incident on the light converging system cannot be efficiently collected in the photoelectric conversion element. Is only partially used.

JP 7-298374 A JP-A-8-14886 Japanese Patent Laid-Open No. 9-21874 JP 2001-4869 A

  The structure that does not have a moving part such as a rotating mirror can cope with a fast change of incident light, but the utilization efficiency of received light is increased by devising a condensing system.

  In the deflecting device of the present invention, the condensing device using the same, and the spatial light receiving device using the same, the light received by devising the condensing system when the optical spatial propagation signal is incident on the receiving device. Can be used with high efficiency.

The present invention is a deflecting device that first converts light incident from an incident direction at a certain solid angle into light in a predetermined direction. This deflecting device has a fiber plate in which both ends are flattened by bundling optical fibers having a refractive index in the center higher than that in the peripheral part, and an optical fiber having a refractive index in the center part lower than that in the peripheral part is bundled at both ends. And a capillary plate having a part or one end in a flat, concave, or convex lens shape. Further, light is incident on the fiber plate, and then the light is passed through the capillary plate. With this unique configuration, incident light having different incident directions is converted into light in a predetermined direction and is incident on a transmission optical fiber .

In general, the optical fiber of the fiber plate has a mirror surface symmetry at the entrance end and the exit end, and when light of a single wavelength is incident on this, the exit light is periodically arranged in the fiber plate. It is known to have an interference pattern reflecting the above. Therefore, in the present invention, by changing the positions of the incident end and the exit end so as not to have mirror symmetry, the incident end and exit having a mirror symmetry corresponding to one-to-one with a linear optical fiber. By shifting from the correspondence relationship with the ends, the incident end and the exit end do not have mirror symmetry , thereby suppressing the effect of the interference.

  Moreover, the refractive index of a center part can be made lower than a peripheral part by making the optical fiber used for said capillary plate into a hollow optical fiber.

  Further, the numerical aperture can be increased by making the diameter of the exit end of the fiber plate larger than the diameter of the entrance end.

  Further, the light collected from the capillary plate can be selected by making the diameter of the exit end of the capillary plate smaller than the diameter of the entrance end.

  Further, by making the shape of the exit end of the capillary plate a concave lens or a convex lens, the light emitted from the deflecting device of the present invention can be condensed or diverged.

  Further, the output beam can be narrowed by providing a condensing system in front of any of the above-described deflecting devices.

  Further, by further including a condensing system that condenses the light emitted from any of the above-described deflecting devices, a condensing device that condenses light in a minute region can be realized.

  The communication device using the optical signal can be realized by making the light of the above-described condensing device incident on the optical fiber and performing signal processing as it is or performing signal processing with an electrical signal after performing photoelectric conversion. . In this case, a spatial light receiving device used for the receiving unit of the spatial light communication can be configured by the light condensing device and the optical fiber.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, devices having the same function or similar functions are denoted by the same reference numerals unless there is a special reason.

  FIG. 1 shows a fiber plate in which both ends are flattened by bundling optical fibers whose refractive index is higher in the center than in the peripheral part, and both end parts in which optical fibers whose refractive index is lower in the center than in the peripheral part are bundled. It is a figure which shows the deflection | deviation apparatus comprised using the capillary plate which made flat. This deflecting device is characterized in that outgoing light is in the same direction d4 with respect to incident light having a single wavelength from the directions d1 and d2 having different incident angles. The direction of the emitted light is a direction along the direction of the optical fiber used for the capillary plate. Here, as the optical fiber used for the capillary plate, an optical material having a refractive index lower than that of the peripheral part may be used in the central part, in addition to the hollow fiber normally used.

  Such a deflection characteristic is an effect obtained by combining the fiber plate and the capillary plate close to each other or in close contact with each other.

  FIG. 2A or FIG. 2B is a diagram showing the direction of outgoing light when single wavelength light is incident on the fiber plate 2 or capillary plate 3, respectively. When light having a single wavelength from the d1 and d2 directions is incident on the fiber plate 2, the emitted light is diffused in either case. Further, when light having a single wavelength from the d1, d2, or d3 direction is incident on the capillary plate 3, only d3 along the optical axis is selectively emitted.

  FIG. 3 shows a spatial light receiver configured using a condensing device 6 in which the fiber plate 2 and the capillary plate 3 are in close contact with each other so that light enters from the fiber plate side. The light from the condensing device 6 is input to the optical fiber 5 used for transmission. Here, what is assumed as the incident light is, for example, the incident light at the time of reception of the spatial light communication.

  Here, it is desirable to adjust the distance between the fiber plate 2 and the capillary plate 3 so that the intensity of light incident on the incident end of the optical fiber 5 is maximized. This is because the distance between the fiber plate and the capillary plate needs to be adjusted depending on the size and pitch of the fibers and capillaries used for each. As a special case, when the fibers and the capillaries coincide, it is desirable that the fibers and the capillaries be in close contact with each other.

  As described above, if the incident angle from the light collecting device 6 to the optical fiber 5 is not extremely large even if the light incident angle to the light collecting device 6 changes, the light entering the light collecting device 6 It can be regarded as constant regardless of the incident angle. That is, even when the wavefront of the signal light fluctuates in spatial light communication, more stable reception is possible compared to the conventional case.

  FIG. 4 is a diagram showing a spatial light receiving device having a configuration in which light from the capillary plate 3 is collected by a condensing device 6 that condenses light by a condensing lens system 4 and is incident on an optical fiber 5. The incident position on the optical fiber 5 is substantially the focal position of the condenser lens system 4. Since the light incident on the light collecting device 6 is usually a thick light beam, the light collecting effect can be enhanced by using the light collecting system 4 as shown in FIG.

  FIG. 5 is a diagram showing a spatial light receiving device having a configuration in which light is collected by the light collecting system 1 and then incident on the fiber plate 2. Since the amount of light incident on the optical fiber 5 can be increased by increasing the light directed to the optical fiber 5 as the output light of the fiber plate 2, the light is condensed at the position of the fiber plate 2 on the extension line of the optical fiber 5. It is clear that it is desirable to do so.

  FIG. 6 shows an optical fiber which is condensed by a condensing device 1 for condensing by a condensing system 4 after being condensed by a condensing system 1 and incident on a fiber plate 2 and condensed by a condensing system 4. FIG. 6 is a diagram illustrating a spatial light receiving device having a configuration that is incident on a light source 5. The advantage of this receiving apparatus is that even when it is difficult to increase the diameter of the fiber plate 2 or capillary plate 3, the diameter can be easily increased for incidence.

  FIG. 7 shows an example in which the aperture at the incident end of the fiber plate 8 is reduced and the aperture on the capillary plate 3 side is increased. In this configuration, the numerical aperture (NA) of the capillary plate 3 can be increased, and when the lens diameter is grounded after the capillary plate 3, light from a light source having a large numerical aperture can be obtained. Such a fiber plate 8 can be produced by bundling optical fibers, drawing them to a high temperature exceeding the softening point, stretching them, cooling them, hardening them, and then cutting them. Also, in order to produce as low a temperature as possible, the fiber of plastic material and the optical fiber of silicon oxide are bundled so as to maintain a substantially uniform distribution, and the diameter of the bundle is increased at a high temperature exceeding the softening point of the fiber of plastic material. It can also be produced by applying a thinning stress to form a fiber bundle with a constriction in a part, and cooling and curing to cut.

  FIG. 8 is a view showing a cross section of a combination of a circular fiber plate 2 and a tapered capillary plate 9. Each capillary of the capillary plate 9 is directed toward the focal point F. With this configuration, only light directed toward the focal point F can be selected.

  FIGS. 9A and 9B are views showing a cross section of a combination of a circular fiber plate 2 and a lens-shaped capillary plate 10a or 10b. The capillaries of these capillary plates 10a or 10b are parallel to the optical axis. By doing so, the emitted light can be condensed or dispersed.

  The above-mentioned fiber plate has, for example, a one-to-one correspondence between the incident end and the emission end with a linear optical fiber and has mirror symmetry. For this reason, it is known that when light of a single wavelength is incident in FIG. 2A, the distribution of the emitted light becomes a pattern having a shading that reflects the periodicity of the fiber plate optical fiber. Such a shading pattern causes fluctuations in the amount of incident light on the optical fiber when the incident wavefront varies due to atmospheric fluctuations in optical communication.

  For this reason, as shown in FIG. 10, the correspondence between the incident end and the exit end of each optical fiber is shifted from the above correspondence so as not to have mirror symmetry, thereby reducing the above-described shading. be able to. In particular, the correspondence relationship between the incident end and the exit end of the optical fiber is desirably as random as possible. In order to make it random in this way, the length should be called a fiber bundle, not the normal fiber plate length. In the present invention, there is no problem even if the optical path length of the fiber plate is long. In each of the above embodiments, by using the fiber plate of FIG. 7 as the fiber plate, it is possible to suppress fluctuations in the amount of light incident on the optical fiber due to the above-described shading.

  Moreover, as said condensing system, a condensing lens system, a concave reflecting mirror, a zone plate, etc. can be used.

  Moreover, in this invention, the light wave from several different directions can be received simultaneously.

A fiber plate in which both ends are flattened by bundling optical fibers having a refractive index higher than that in the peripheral part and an optical fiber having a refractive index lower in the central part than that in the peripheral part are bundled to flatten both ends. It is a figure which shows the deflection | deviation apparatus comprised using the capillary plate. It is a figure which shows the direction of the emitted light when the light of a single wavelength injects into a fiber plate or a capillary plate. It is a figure which shows the spatial light receiver comprised using the condensing apparatus which closely_contact | adhered the fiber plate and the capillary plate and made it inject light from the fiber plate side. FIG. 3 is a diagram showing a spatial light receiving device having a configuration in which light from a capillary plate 3 is collected by a condensing device 6 that condenses light by a condensing lens system 4 and is incident on an optical fiber 5. It is a figure which shows the spatial light receiver with the structure which injects into a fiber plate after condensing by a condensing system. A space with a configuration in which the light is collected by the light collecting system and then incident on the fiber plate, and the light from the capillary plate in close contact with the light is condensed by the light collecting device that collects the light from the condenser lens system and is incident on the optical fiber. It is a figure which shows an optical receiver. It is a figure which shows the example which made the diameter of the entrance end of a fiber plate small, and enlarged the diameter by the side of a capillary plate. It is a figure which shows the cross section of what combined the circular fiber plate and the taper capillary plate. It is a figure which shows the cross section of what combined the circular fiber plate and the lens-shaped capillary plate. FIG. 6 is a schematic diagram showing a fiber plate in which the density of the outgoing light is relaxed by shifting the correspondence between the incident end and the outgoing end of each optical fiber from the normal correspondence so as not to have mirror symmetry. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Condensing system 2 Fiber plate 3 Capillary plate 4 Condensing system 5 Optical fiber 6 Condensing apparatus 7 Fiber plate 8 Fiber plate 9 Capillary plate 10a Concave lens-shaped capillary plate 10b Convex-lens-shaped capillary plate

Claims (10)

A fiber plate in which optical fibers having a refractive index at the center higher than that at the periphery are bundled;
A capillary plate bundled with optical fibers having a refractive index at the center lower than that at the periphery;
A structure in which light is incident on the fiber plate;
With
Incident light having different incident directions is passed through the fiber plate and capillary plate as light in a predetermined direction, and is incident on a transmission optical fiber,
The optical fiber of the above-mentioned fiber plate is a straight optical fiber and is shifted from the correspondence between the incident end and the exit end having a mirror symmetry corresponding to 1: 1, and the entrance end and the exit end have mirror symmetry. A deflecting device characterized by not having . 2. The deflecting device according to claim 1 , wherein the optical fiber used for the capillary plate is a hollow optical fiber. The deflection apparatus according to claim 1 , wherein the fiber plate has a diameter of an output end larger than a diameter of an input end. Deflection device according to claim 1 or 3, characterized in that the flat end portions of the fiber plate. It said capillary plates, the deflection device according to claim 1 or 2, characterized in that less than the diameter of the entrance end of the aperture of the exit end. It said capillary plates, the deflection device according to claim 1, 2 or 4, characterized in that flattening the shape of the incident end or the exit end or both ends. The deflection apparatus according to claim 1 or 2 , wherein the capillary plate has a shape of a concave lens or a convex lens at an incident end, an output end, or both ends. 3. A deflecting device, further comprising a condensing system in front of the deflecting device according to claim 1 . 9. A condensing device, further comprising a condensing system for condensing light emitted from the deflection device according to claim 1, 2 or 8 . An optical fiber for entering the light of the light collecting device according to claim 9 is further provided,
A spatial light receiving apparatus, wherein incident light having different incident directions is incident on an optical fiber at a predetermined incident angle.

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