JP2007120742A - Rotary joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary joint allowing stable optical data transmission without arranging a light emitting element and a light receiving element in proximity while causing no deterioration of the transmission quality of signal light accompanied by the deviation of an optical axis in the rotary joint provided with an optical data transmission line. <P>SOLUTION: The rotary joint 1 is constituted to perform optical transmission from a rotating cylinder 3 side to a fixed cylinder 2 side by holding the rotating cylinder 3 rotatably to the fixed cylinder 2 through hollow bearings 4a, 4b. In this case, the rotating cylinder 3 is provided with an optical waveguide 19 penetrating the end face C side from the end face D side of the rotating cylinder 3, and a laser diode 13 is disposed on the end face C side opposedly to the end face D side. The fixed cylinder 2 has a photodiode 16 having a light receiving surface larger than the area of the end face B of the optical waveguide 19. The photodiode 16 is disposed facing the end face B of the optical waveguide 19 penetrating the end face D side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure of a rotary joint that performs data transmission between a fixed part and a rotating part rotatably combined with the fixed part by optical data transmission.

  Many surveillance camera devices that are fixedly installed on an indoor ceiling or the like that perform monitoring while changing the imaging direction by controlling the pan angle and tilt angle of the camera are widely used. Such a surveillance camera device capable of angle control has a configuration in which a fixed part fixedly installed on a ceiling or the like and a movable part rotatable in the pan direction are connected via an electric pan head. There are many things. That is, in the surveillance camera device, a movable part equipped with a camera having a tilt drive mechanism that rotates in the tilt direction is attached to one (movable part) of an electric pan head that is rotatable in the pan direction, and the electric cloud In many cases, the base (the fixed portion) is attached to one of the fixed portions, and the other fixed portion is fixedly installed on the ceiling or the like. In the surveillance camera device having such a configuration, the video signal output from the camera mounted on the movable unit is transmitted to the fixed unit via the electric camera platform, and image processing and output interface conversion are performed in the fixed unit. After that, it is output to an external monitor or video signal recording device.

  Several methods are known for the electronic camera platform used in the above-described surveillance camera device. Particularly, as an electronic camera platform that can continuously move the movable part in the pan direction, a slip ring and a brush are used. The construction of a signal connection path extending between the swivel part and the fixed part by a sliding contact is known. However, with this sliding contact method, the oil film or dust adheres to the contact part between the swiveling slip ring and the fixed brush, resulting in unstable electrical contact or noise associated with mechanical contact. There are problems such as deterioration of electrical contact performance due to long-term continuous sliding. In particular, when transmitting a video signal from the swivel unit to the fixed unit, it is difficult to secure a wide frequency band with the sliding contact method, so that the transmittable video signal is limited to a low-resolution video signal with a narrow frequency band. Therefore, there is a problem that it is difficult to transmit data of an HD video signal having high resolution.

  Therefore, in an electronic head having a swivel unit and a fixed unit, a video signal output from a camera attached to the swivel unit and a control signal transmitted from the fixed unit to the swivel unit are transmitted from the light emitting diode and the photodiode. A technique for improving the signal quality deterioration problem associated with the above-described sliding contact method by transmitting through a configured optical signal transmission path is known (for example, see Patent Document 1). Specifically, in Patent Document 1, an optical transmission unit is provided in the vicinity of the rotation axis in the turning unit, and an optical reception unit is provided in the vicinity of the rotation axis in the fixed unit. A technique is disclosed in which an output video signal is converted into signal light by an optical transmission unit to emit light, and light is received by an optical reception unit in the fixed portion through an opening between the turning portion and the fixed portion.

Further, as a technique that further improves the invention described in Patent Document 1, a slip ring transmission unit and an optical signal transmission unit that transmits a video signal are provided in a closed space constituted by a pan rotating body, a bearing housing, a cover, and the like. In addition, there is also known an electric head that improves the reliability of signal transmission by preventing oil film and dust from adhering to the light emitting element and the light receiving element (see, for example, Patent Document 2). In Patent Document 2, a signal is transmitted by a light emitting element fixed to one end of a rotating body so as to form an optical axis that coincides with the rotational axis of the rotating body, and a light receiving element that receives light from the light emitting element. Optical signal transmission means is disclosed.
JP-A-9-284612 JP 2001-183738 A

  However, according to Patent Document 1, since the optical transmission unit and the optical reception unit are respectively disposed in the vicinity of the rotation axis of the swivel unit, the optical axes of the light emitting diode and the photodiode do not coincide during the swiveling operation. The emission angle of the signal light emitted from the light emitting diode must be wide considering the deviation of the optical axis. That is, with the technique disclosed in Patent Document 1, it is extremely difficult to use a light emitting diode having a narrow emission angle such as a laser diode, and therefore, a sufficient S / N ratio is required because sufficient reception power cannot be obtained. Transmission of high-definition video is impossible, and only low-definition video signals with a low data transmission rate can be transmitted.

  Further, according to the method disclosed in Patent Document 2, transmission of signal light is performed through a free space between the light emitting element and the light receiving element arranged on the rotating shaft of the rotating body. When a change with time such as wear of the rotating mechanism occurs due to the rotating operation of the rotating body, there is a possibility that a deviation occurs between the rotating shaft of the rotating body and the optical axis of the optical signal transmitting means. When such an optical axis shift occurs, there arises a problem that the optical signal received by the receiving element varies with rotation. Further, in order to obtain a constant reception S / N ratio, it is necessary to obtain a considerable reception intensity as signal light. Therefore, it is necessary to arrange the transmission element and the reception element as close as possible, and the rotary joint. It becomes a big restriction in constructing.

  Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to perform optical data transmission between a fixed portion and a rotating portion that is rotatably combined with the fixed portion and each light of the light emitting element and the light receiving element. Even if there is a deviation in the axis, it can be performed stably without degrading the signal quality of the signal light, and stable optical data transmission is possible even if the light emitting element and the light receiving element are not arranged close to each other. Is to provide a reliable rotary joint.

In order to solve the above problems, the invention described in claim 1
One end face (D) of the cylindrical rotary part (3) is rotatably held by the fixed part (2) via bearings (4a, 4b) with a predetermined interval, and the rotary part A rotary joint (1) for performing optical transmission from the side to the fixed part side,
The rotating part is
A cylindrical optical waveguide (19) is passed through the end surface (C) from the one side to the other side of the rotating unit with the central axis passing through the tube and the rotating axis (P) of the rotating unit aligned. While providing
The light emitting element (13) is disposed on the other end face so as to face the one end face at a position where the optical axis of the light emitting element and the rotation axis coincide with each other.
The fixing part is
A light receiving element (16) having a light receiving surface with an area larger than the area of the end faces (A, B) of the optical waveguide is aligned with the optical axis of the light receiving element and the rotation axis and on the one side. A rotary joint (1) configured to face the end face (B) of the penetrated optical waveguide
Is to provide.

The invention described in claim 2
The fixing part is
A light receiving element having a light receiving surface having an area smaller than the area of the end surface of the optical waveguide through the condenser lens (20) for the light beam emitted from the end surface of the optical waveguide penetrating to the one side of the rotating unit The rotary joint (21) according to claim 1, wherein the rotary joint (21) is configured to condense on the light receiving surface in (26).
Is to provide.

The invention according to claim 3
One end face (D) of the cylindrical rotating part (3) is rotatably held by the fixing part (2) via bearings (4a, 4b) with a predetermined interval, and the fixing part A rotary joint (1) for performing optical transmission from the side to the rotating part side,
The rotating part is
A cylindrical optical waveguide (19) is passed through the end surface (C) from the one side to the other side of the rotating unit with the central axis passing through the tube and the rotating axis (P) of the rotating unit aligned. While providing
The light receiving element (16) having a light receiving surface with an area larger than the area of the end faces (A, B) of the optical waveguide is the other end face, and the optical axis of the light receiving element coincides with the rotation axis. Arranged to face the one end face at the position to be
The fixing part is
A rotary joint (1) having a configuration in which the light emitting element (13) is disposed so that the optical axis of the light emitting element coincides with the rotation axis and is opposed to the end face of the optical waveguide penetrating on the one side.
Is to provide.

The invention according to claim 4
The rotating part is
A light receiving element having a light receiving surface having an area smaller than the area of the end surface of the optical waveguide through the condenser lens (20) for the light beam emitted from the end surface of the optical waveguide penetrating the other side of the rotating unit The rotary joint (21) according to claim 3, wherein the rotary joint (21) is configured to condense on the light receiving surface in (26).
Is to provide.

The invention described in claim 5
The rotary joint (91) according to any one of claims 1 to 4, wherein the cylindrical optical waveguide is configured as a bendable optical fiber cable (19a).
Is to provide.

  According to the present invention, by arranging one end face of the optical waveguide close to the transmission surface of the light emitting element, optical coupling between the light emitting element and the optical waveguide is low loss and hardly affected by the optical axis shift. can do. The signal light incident on the optical waveguide is transmitted while suppressing the deterioration of the frequency response performance and the decrease of the optical signal level, and is emitted from the other end face. The signal light emitted from the other end face is received by the light receiving element provided close to the other end face of the optical waveguide, and the area of the light receiving face of the light receiving element is the area of the end face of the optical waveguide. By making it larger, the optical coupling between the optical waveguide and the light receiving element can be made less susceptible to the effects of the optical axis deviation with low loss, and thereby stable optical signal transmission having a transmission band of about 100 MHz. Can be done.

  Further, according to the present invention, the area of the light receiving surface of the light receiving element is made smaller than the area of the end face of the optical waveguide, and a condensing lens is provided between the light receiving element and the optical waveguide, thereby providing an optical waveguide. The optical coupling between the tube and the light receiving element can be made less susceptible to the effects of optical axis deviation with low loss, and thereby, optical signal transmission having a transmission band of 1 GHz or more can be stably performed.

  Further, according to the present invention, since signal light is transmitted through an optical waveguide, stable transmission can be performed without arranging a light emitting element and a light receiving element close to each other as in the prior art. The degree of freedom of arrangement of the light emitting element side substrate and the light receiving element side substrate is increased. In particular, when handling a data signal having a high transmission speed of gigabit class as a transmission signal, it is necessary to dispose the drive circuit as close as possible in the light emitting element, and the photoelectric conversion circuit is disposed as close as possible in the light receiving element. Since it is necessary, it is desirable that the light transmitting / receiving element is directly attached to the substrate. Since such an arrangement is possible according to the present invention, application to high-speed data transmission can be easily achieved. In addition, it is possible to provide a rotary joint that can reduce restrictions on the configuration of the rotary joint, is low-cost with a simple configuration, and can maintain stable performance for a long period of time.

  Furthermore, according to the present invention, by using a bendable optical fiber cable as an optical transmission path between the light emitting element and the light receiving element, it is possible to provide a mechanical part or the like on the rotating shaft inside the rotating part. Design freedom is obtained.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
<First Embodiment>
FIG. 1 is a schematic sectional view of a rotary joint according to the first embodiment of the present invention. In the rotary joint 1 shown in the same figure, the fixed cylinder portion 2 stores and fixes hollow bearings 4a and 4b as bearings that rotatably hold the rotary cylinder portion 3 about the axis P, thereby fixing the rotary cylinder portion. Each member as a rotating part held by 3 is rotatably held.

  A slip ring transmission portion 5 is formed on the outer periphery of the rotating cylinder portion 3 and inside the hollow bearings 4a and 4b. Specifically, the slip ring transmission portion 5 includes a plurality of (four in the present embodiment) conductive rings 6 on the outer periphery of the rotating cylinder portion 3 and insulated inside the hollow bearings 4a and 4b. It is fixed via the ring 7.

  A plurality (four in this embodiment) of brushes 8 are provided inside the fixed cylinder portion 2 via the insulating base 9 so as to maintain sliding contact corresponding to the four conductive rings 6 respectively. It is fixed. And each front-end | tip part of the four brushes 8 is pressed by the conductive ring 6 with the elastic force of each brush 8 itself, and the stability of contact is ensured.

  One end of a rotating portion side lead wire 10 is connected to each of the four conductive rings 6, and the other end of the rotating portion side lead wire 10 is drawn out to the rotating portion side through the inside of the rotating cylinder portion 3. Further, one end of the fixed part side lead wire 11 is connected to each of the four brushes 8, and the other end of the fixed part side lead wire 11 passes through the through hole of the fixed cylinder part 2 to the fixed part side. Pulled out. In this way, an electrical connection is established between the rotating portion side lead wire 10 and the fixed portion side lead wire 11 that are respectively connected via the brush 8 that is in sliding contact with the conductive ring 6.

  An optical signal transmission unit 12 is formed inside the rotary cylinder unit 3 and at the bottom of the fixed cylinder unit 2. Specifically, the end face C on the rotating portion side of the rotating cylinder portion 3 has a fitting shape that matches the outer shape of the laser diode 13 that is a light emitting element so that the optical axis of the laser diode 13 matches the axis P. Is formed. The laser diode 13 is attached to a laser diode substrate 14 on which a driver circuit (not shown) is mounted. The laser diode substrate 14 is end face C on the rotating portion side of the rotating cylinder portion 3 by a plurality of substrate mounting screws 15. It is fixed to. Thus, the laser diode 13 is fixedly installed with its optical axis aligned with the axis P.

  The end face D on the fixed part side of the rotating cylinder part 3 and the inner wall E on the bottom surface of the fixed cylinder part 2 maintain an interval of several hundred μm to several mm. From the bottom outer wall side of the fixed cylinder portion 2, a fitting shape that matches the outer shape of the photodiode 16 that is a light receiving element is formed so that the optical axis of the photodiode 16 matches the axis P. The photodiode 16 is attached to a photodiode substrate 17 on which a photoelectric conversion circuit (not shown) for received signal light is mounted. The photodiode substrate 17 is attached to the fixed cylinder portion 2 by a plurality of substrate mounting screws 18. Fixed to the bottom. As a result, the photodiode 16 is fixedly installed with its optical axis aligned with the axis P.

  The inside of the rotating cylinder portion 3 is a cavity, and has a cylindrical shape with an inner diameter of about several hundreds μm to several mm between the laser diode 13 and the photodiode 16 and having an inner high reflectance finish. An optical waveguide 19 having end faces A and B orthogonal to the central axis is provided with the central axis of the cylinder and the axis P aligned.

  Then, one of the optical waveguides 19 (on the end surface A side) can obtain an optical coupling optimum for the light emitted from the laser diode 13, that is, the light emitted from the laser diode 13 incident on the end surface A is the optical waveguide 19. It is fixed so that it does not leak outside. Thereby, the optical coupling between the laser diode 13 and the optical waveguide 19 is ensured stably without being influenced by the center deviation of the hollow bearings 4a and 4b that occurs with time. The other side (end face B side) of the optical waveguide 19 is exposed to the end face D on the fixed part side of the rotating cylinder part 3 and is fixed in non-contact with the light receiving part of the photodiode 16.

  The distance between the end face B of the optical waveguide 19 and the light receiving portion of the photodiode 16 is set to be a few millimeters or less so as not to physically contact, and the signal light emitted from the end face B is close to this distance. It enters the photodiode 16 through the free space.

  As described above, by providing the above-described configuration, the optical axis of the laser diode 13, the cylindrical central axis of the optical waveguide 19, and the optical axis of the photodiode 16 are held at the same positions. Reception is achieved.

  Next, a specific example of the combination of the optical waveguide 19, the laser diode 13, and the photodiode 16 will be shown, and an example of calculating the efficiency of optical data transmission and the degree of influence due to center deviation will be shown. FIG. 4 is a cross-sectional view of the optical signal transmission unit 12 in which the optical waveguide 19, the laser diode 13, and the photodiode 16 are combined. In the drawing, an optical waveguide 19 is a stainless steel cylinder having an inner diameter of 1 mm, an inner surface reflectance of 80%, and a dimension between end faces A and B of 50 mm. The laser diode 13 is a VCSEL (Vertical Cavity Surface Emitting Laser: surface emitting semiconductor laser) having a diameter of 10 μm and a spread angle of 30 degrees (all angles including 99% of the total luminous flux). The photodiode 16 is a photodiode having a diameter of 3 mm having an area larger than the inner diameter of the optical waveguide 19.

  The light emitting point of the laser diode 13 is fixed via a package at a position 1 mm from the end surface A side of the optical waveguide 19 as shown in the figure, and the light receiving surface of the photodiode 16 is the end surface B side of the optical waveguide 19 It is arranged at a position of 1 mm from.

  The optical transmission efficiency of each part in the above configuration will be described. The transmission efficiency between the laser diode 13 and the optical waveguide 19 is determined by the inner diameter of the optical waveguide 19 and the emission beam diameter of the laser diode 13 at the end face A of the optical waveguide 19, and in this configuration example, the transmission efficiency of the optical waveguide 19 If the beam diameter at the end surface A of the optical waveguide is about 0.686 mm with respect to the inner diameter of 1 mm, 100% transmission efficiency can be obtained.

  In this case, the allowable deviation of the center between the laser diode 13 and the optical waveguide 19 is ± 0.15 mm. With this allowable value, the transmission efficiency is 100% even with simple assembly and fixing. And 100% efficiency can be maintained even with respect to temperature change and secular change.

  On the other hand, the transmission efficiency of the optical waveguide 19 is determined by the inner surface reflectance of the optical waveguide 19 and the dimension between the end faces A and B. Here, FIG. 5 shows the transmission efficiency with respect to the inner surface reflectance when the dimension between the end faces A and B of the optical waveguide 19 is 50 mm. According to the figure, at an inner surface reflectance of 80% in this configuration example, a transmission efficiency of about 17.8% can be obtained in terms of the light quantity ratio between the end surfaces A and B.

  FIG. 6 shows the transmission efficiency with respect to the dimension between the end faces A and B of the optical waveguide 19 when the inner reflectance of the optical waveguide 19 is 80%. In the figure, the transmission efficiency of the optical waveguide 19 is shown by a solid line graph, and as a conventional method not using the optical waveguide 19, the light transmission / reception in the case where the wide LED light is directly irradiated to the photodiode is shown. The transmission efficiency at the distance between elements is shown by a dotted line graph. In the conventional method, the LED spread angle is 30 degrees, which is the same as the laser diode 13, and the photodiode diameter is also 3 mm.

  As shown in the figure, according to the conventional method, the transmission efficiency is attenuated by the square of the distance, whereas in the method using the internal reflection of the optical waveguide 19 in this embodiment, the transmission efficiency is greatly improved. It turns out that it is obtained. In this calculation, the case where the internal reflectance is 80% is shown as a value that can be obtained at a low cost. However, the sensitivity can be further increased and the distance can be extended by increasing the internal reflectance. The increase in sensitivity can increase the transmission speed and improve the mounting margin, and the extension of the distance can provide a margin for the configuration and arrangement of the equipment.

  The transmission efficiency between the optical waveguide 19 and the photodiode 16 is determined by the inner diameter of the optical waveguide 19, the spread angle of light emitted from the optical waveguide 19, and the diameter and position of the photodiode 16. The diameter of the emitted light irradiated to the photodiode 16 from the end face B of the optical waveguide 19 is about 1.536 mm, and the diameter of the photodiode 16 is 3 mm, so that 100% of the emitted light can be received. it can.

  In addition, the tolerance of the center deviation at that time is ± 0.716 mm. With this tolerance, a transmission efficiency of 100% can be secured even with simple assembly and arrangement, as well as changes in temperature and aging. Furthermore, optical data transmission can be performed without loss even with respect to cylinder rotation.

  By the way, when a photodiode having a relatively large area is used as the light receiving element as in this configuration example, there is a problem that the junction capacitance generated by the reverse bias operation of the photodiode is increased and the frequency band is narrowed. However, if the diameter is about 3 mm as in the above example, there is a photodiode that can obtain about 100 MHz as a high frequency cutoff frequency Fc (frequency at which the reception level is halved) for optical reception. By using it, it is possible to stably optically transmit an HD compressed video signal having a transmission rate of about several tens of Mbps.

<Second Embodiment>
FIG. 2 is a schematic sectional view of a rotary joint according to the second embodiment of the present invention. The rotary joint 21 shown in the figure has the same configuration as that of the rotary joint 1 in the first embodiment, but the configuration of the optical signal transmission unit 22, particularly the configuration of the light receiving portion that receives light through the optical waveguide 19. Different from the rotary joint 1. Therefore, in the description of the present embodiment, the same components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be omitted.

  In the rotary joint 21 of FIG. 2, the photodiode 26 is a light receiving element having an area larger than the inner diameter of the optical waveguide 19. The optical axis of the condenser lens 20 is aligned between the end face B of the optical waveguide 19 and the photodiode 26, and an optical signal emitted from the end face B of the optical waveguide 19 is received by the condenser lens 20. It arrange | positions so that it may condense to 26 and may receive. With this configuration, the optical coupling between the optical waveguide 19 and the photodiode 26 can be made less susceptible to the effect of optical axis deviation with low loss, and compared with the rotary joint 1 in the first embodiment. Thus, optical data transmission over a wider band is possible.

  Next, a specific example of a combination of the optical waveguide 19, the laser diode 13, the photodiode 26, and the condenser lens 20 will be shown, and an example of calculating the efficiency of optical data transmission and the degree of influence due to the center deviation will be shown. FIG. 7 is a cross-sectional view of the optical signal transmission unit 22 in which the optical waveguide 19, the laser diode 13, the photodiode 26, and the condenser lens 20 are combined. In the drawing, an optical waveguide 19 is a stainless steel cylinder having an inner diameter of 1 mm, an inner surface reflectance of 80%, and a dimension between end faces A and B of 50 mm. The laser diode 13 is a VCSEL having a diameter of 10 μm, a spread angle of 30 degrees (all angles including 99% of the total luminous flux), and an optical output of 0.5 mW. The photodiode 26 is a photodiode having a diameter of 0.6 mm. The condenser lens 20 is a convex lens having a diameter of 1.8 mm and a thickness of 0.9 mm.

  The light emitting point of the laser diode 13 is fixed via a package at a position 1 mm from the end face A side of the optical waveguide 19 as shown in the figure, and the condenser lens 20 is 0 from the end face B side of the optical waveguide 19. The photodiode 26 is disposed at a position 0.9 mm from the condenser lens 20.

  The optical transmission efficiency of each part in the above configuration will be described. The transmission efficiency between the laser diode 13 and the optical waveguide 19 and the transmission efficiency of the optical waveguide 19 are the same as those described in the first embodiment, and are omitted here. The transmission efficiency between the optical waveguide 19 and the photodiode 26 depends on the inner diameter of the optical waveguide 19, the spread angle of light emitted from the optical waveguide 19, the diameter and curvature radius of the condenser lens 20, and the position of the photodiode 16. In this configuration example, 71% of the light emitted from the end face B of the optical waveguide 19 can be received by the condenser lens 20.

  FIG. 8 shows a case where the distance from the end surface B of the optical waveguide 19 to the incident surface of the condenser lens 20 is 0.5 mm as a standard position, and the condenser lens 20 is displaced from the center (Y-axis displacement). Changes in the optical transmission efficiency when 20 is displaced in the optical axis direction of the emitted light (Z-axis displacement) are shown. According to the figure, the Y-axis displacement has a margin of ± 0.4 mm at the half-value level of the received light amount, and the Z-axis displacement has a margin of ± 1 mm or more at the half-value level of the received light amount. Therefore, optical data transmission can be performed with low loss even with respect to simple assembly and arrangement, temperature change, aging change, and cylinder rotation.

  If a photodiode 26 having an area smaller than the inner diameter of the optical waveguide 19 is used as the light receiving element as in the present embodiment, the junction capacitance generated by the reverse bias operation of the photodiode can be suppressed, and broadband reception can be achieved. It becomes possible. In this embodiment, 1 GHz or more can be secured as the high frequency cutoff frequency Fc for optical reception. Taking a high-definition video SXGA (Super Extended Graphics Array) as an example, if one screen is 1280 × 1024 pixels, the frame rate is 60 fps, and it is converted to a serial signal by parallel serial processing, then 1280 × 1024 conversion is performed. × 1024 × 60 × 1.25 = 1.31584 (Gbps). The high frequency cut-off frequency of the transmission system required to transmit serial data having the same bit rate is about half the bit rate, that is, about 0.66 GHz, and is a frequency lower than 1 GHz. Therefore, the rotary joint 21 is used. Thus, it is possible to optically transmit 60 fps SXGA data as an uncompressed signal.

  When the photodiode 26 is covered with a metal case and the signal light incident surface is protected by a light transmissive member such as glass, the protective member is formed in the shape of a condensing lens. Then, even if the signal light emitted from the end face B of the optical waveguide 19 is condensed on the photodiode 16 by this protective member, the same effect as in the present embodiment can be obtained.

<Third Embodiment>
In each of the first embodiments described above, the example in which the optical waveguide 19 is used as the member of the optical transmission path disposed between the laser diode 13 and the photodiode 16 in the optical signal transmission unit 12 has been described. In this embodiment, an example in which the optical waveguide 19 is replaced with a bendable optical fiber cable will be described.

  FIG. 9 is a schematic sectional view of a rotary joint according to the third embodiment of the present invention. The rotary joint 91 shown in the figure has the same configuration as the rotary joint 1 in the first embodiment, but the configuration of the optical signal transmission unit 92 is different from that of the rotary joint 1. Therefore, in the description of the present embodiment, the same components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be omitted.

  In the rotary joint 92 of FIG. 9, a bendable optical fiber member having a core diameter of several hundreds μm to several mm between the laser diode 13 and the photodiode 16 and having end faces Aa orthogonal to the center axis of the fiber. An optical fiber cable 19a having Ba is provided so that the center axis of the fiber in the light emitting part of the laser diode 13 and the optical axis coincide with each other, and the center axis of the fiber in the light receiving part of the photodiode 16 and the optical axis coincide. Yes.

  Then, one of the optical fiber cables 19a (on the end face Aa side) can obtain an optical coupling optimum for the light emitted from the laser diode 13, that is, the light emitted from the laser diode 13 incident on the end face Aa is the optical fiber cable 19a. It is fixed so that it does not leak outside. The other end (on the side of the end face Ba) of the optical fiber cable 19a is exposed to the outside of the end portion D on the fixed portion side of the rotary cylinder portion 3 and is fixed in non-contact with the light receiving portion of the photodiode 16.

  The distance between the end face Ba of the optical fiber cable 19a and the light receiving portion of the photodiode 16 is set so as not to physically contact, and the signal light emitted from the end face Ba passes through this short-distance free space. The light enters the photodiode 16.

  In a general optical fiber cable for data communication, a core of several tens of μm to several hundreds of μm is used in order to prevent the transmission frequency band from being limited by delay spread caused by passing signal light through a plurality of paths inside the fiber. Diameter is needed. However, in the present embodiment, since the length between the end surface Aa and the end surface Ba of the optical fiber cable 19a is about several centimeters, the above delay spread is not a problem, and even for high-speed optical data transmission of 10 Gbps, for example. There is no problem with bandwidth limitation.

  As described above in detail, in the rotary joint 91 of the present embodiment, the flexible optical fiber cable 19a is used as the optical transmission path between the laser diode 13 and the photodiode 16, so It is possible to improve the degree of freedom of design, such as making it possible to provide a mechanical part or the like on the shaft P. Further, when the optical fiber cable 19a is used, the transmission light taken into the optical fiber is repeatedly reflected on the inner wall of the fiber and transmitted to the opposite end. Since the reflection is performed by total reflection, a reflectance of approximately 100% can be obtained. As can be seen from FIG. 5, the transmission efficiency is 100% when the internal reflectance is 100%. Therefore, it is effective to use the optical fiber cable 19a when the optical waveguide 19 is insufficient in the reception level.

  The optical fiber cable 19a may be replaced with the optical waveguide 19 in the second embodiment described above to constitute an optical signal transmission unit.

  In each of the first to third embodiments, an example in which the laser diode 13 is disposed in the rotating cylinder portion 3 and the photodiode 16 (including the condenser lens 20) is disposed in the fixed cylinder portion 3 is possible. Contrary to this, even when the photodiode 16 (which may include the condensing lens 20) is arranged in the rotating cylinder portion 3 and the laser diode 13 is arranged in the fixed cylinder portion 3, Of course, the same effects as those of the embodiments can be obtained.

  Furthermore, in each of the first to third embodiments, the fixed cylinder portion 2 and the rotary cylinder portion 3 around the end surface B and the end surface Ba exposed from the end surface D on the fixed portion side of the rotary cylinder portion 3. Between them, you may make it provide the dustproof shield by buffer members, such as felt. The dust shield is fixed to the circumference of the shaft P without a gap, either on the inner wall E on the bottom surface of the fixed cylinder portion 2 or on the end surface D on the fixed portion side of the rotary cylinder portion 3. The dust shield fixed in this manner is in sliding contact with either the end face D on the fixed part side of the rotary cylinder part 3 or the bottom inner wall E of the fixed cylinder part 2 when the rotary cylinder part 3 rotates. For this reason, it is possible to block dust and lubricating oil from entering the end faces B and Ba, and to ensure stable optical transmission over a long period of time.

  Furthermore, in each of the first to third embodiments, by using an oil seal type for the hollow bearing 4b as a bearing, a closed space is formed by the fixed cylinder portion 2, the hollow bearing 4b, and the rotary cylinder portion 3. The closed space may be filled with lubricating oil having optical transparency. The dustproof effect can be particularly enhanced by filling the lubricating oil. Then, the end face B and Ba and the light receiving portion of the photodiode 16 can be further brought closer by the effect of the lubricating oil. Further, in the above closed space, if the space between the end faces B and Ba and the light receiving portion of the photodiode 16 is filled with lubricating oil having a refractive index higher than that of air, the coupling efficiency of signal light is further improved. Can be made. Therefore, by adopting such a configuration, it is possible to further suppress the transmission loss of signal light and keep the signal quality high.

  An example in which the first to second embodiments of the present invention described above are applied to a monitoring camera device will be described. FIG. 3 is a configuration example of a monitoring camera device to which any of the rotary joints 1, 21, or 91 described above is applied. In the description of the present embodiment, the case where the rotary joint 1 of the first embodiment is applied will be described, and the embodiment where the rotary joints 21 and 91 of the second and third embodiments are applied will be described. Since the implementation contents are substantially the same, the description thereof is omitted.

  In FIG. 3, the surveillance camera device 30 has a structure in which a movable portion 32 is attached to a fixed portion 31 fixedly installed on a ceiling via a rotary joint 1 as a pan rotation mechanism. Each pixel data is R, G, B 8-bit SXGA (1280 × 1024 pixels) or Quad-VGA (1280 × 960 pixels), and 30 fps video data (parallel video data) is stored in the movable unit 32. The output camera 301 and the parallel video data output from the camera 301 are converted into serial data, then converted to 8B-10B and supplied to the laser diode substrate 14 of the rotary joint 1. And a tilt drive unit 303 for rotating the camera 301 in the tilt direction.

  The fixing unit 31 includes a power supply unit 304 for supplying a driving voltage to the entire surveillance camera device 30, a control unit 305 for controlling the entire surveillance camera device 30, and the rotary joint 1 that is a pan rotation mechanism of the movable unit 32. After the pan drive unit 306 for rotating the movable unit 32 in the pan direction and the 8B-10B-converted serial data supplied from the movable unit 32 via the rotary joint 1 are converted into 10B-8B. , An S-P conversion unit 307 for outputting parallel video data of 8 bits each for R, G, B by serial-parallel (SP) conversion, and parallel video data obtained from the SP conversion unit 307 And a video output connector 308 for outputting to the outside.

  The power supplied from the power supply unit 304 to the movable unit 32 and the control signal supplied from the control unit 305 to the movable unit 32 are transmitted via the slip ring transmission unit 5 of the rotary joint 1. The serial data after the 8B-10B conversion supplied from the PS conversion unit 302 of the movable unit 32 to the SP conversion unit 307 of the fixed unit 31 through the rotary joint 1 passes through the optical signal transmission unit 12 of the rotary joint 1. Is transmitted.

  A control device 33 provided outside the monitoring camera device 30 controls the tilting operation of the camera 301 and the panning operation of the movable unit 32 with respect to the monitoring camera device 30. That is, the control device 33 transmits the tilt angle information and the tilt drive start request information to the control unit 305 of the fixing unit 31, and the control unit 305 passes these information through the slip ring transmission unit 5 of the rotary joint 1. To supply. Accordingly, the tilt driving unit 303 rotates the camera 301 in the tilt direction according to the supplied tilt angle information and tilt drive start request information.

  At the same time as this tilt control or at another time, the control device 33 transmits pan angle information and pan drive start request information to the control unit 305, and the control unit 305 that receives these information controls the pan drive unit 306. To do. Accordingly, the pan driving unit 306 rotates the movable unit 32 in the pan direction according to the pan angle information and the pan driving start request information.

  Next, data transmission of the parallel video data output from the camera 301 to the fixing unit 31 will be described in more detail. From the camera 301, 8-bit parallel video data for each of R, G, and B is output and supplied to the PS conversion unit 302. The PS conversion unit 302 converts the incoming parallel video data into one serial data, converts this serial data into 8B-10B, and supplies it to the laser diode substrate 14 of the rotary joint 1.

  Here, the transmission rate of the serial data subjected to the 8B-10B conversion by the PS converter 302 is 1280 × 1024 × 30 × 8 × 3 × 10/8 = 1 in the case of SXGA (1280 × 1024 pixels) video. .18 Gbps, and in the case of Quad-VGA (1280 × 960 pixels) video, 1280 × 960 × 30 × 8 × 3 × 10/8 = 1.106 Gbps. The laser diode 13 mounted on the laser diode substrate 14 emits signal light whose intensity is modulated by the serial data after 8B-10B conversion supplied from the PS converter 302, but the frequency response of the laser diode 13 is Since performance of about several GHz is common, optical data transmission with a transmission rate of 1.106 Gbps to 1.18 Gbps can be performed with a margin.

  The signal light having a transmission rate of 1.106 Gbps to 1.18 Gbps emitted from the laser diode 13 is incident on the end surface A of the optical waveguide 19, and the signal light transmitted through the optical waveguide 19 is transmitted from the end surface B to the fixed cylinder portion 2. Is incident on the photodiode 16 of the photodiode substrate 17 attached to the bottom of the substrate. The signal light received by the photodiode 17 is subjected to photoelectric conversion processing, and then 8B-10B converted serial data is supplied to the SP conversion unit 307.

  The SP conversion unit 307 performs 10B-8B conversion on the supplied serial data, and then converts the serial data into 8-bit R, G, and B parallel video data and outputs the parallel video data from the video output connector 308. Although not shown, the output parallel video data is supplied to the video display monitor to display the captured video of the camera 301 or supplied to the video data recording device and recorded in the recording unit.

  As described above in detail, according to the surveillance camera device to which the rotary joint 1 is applied, the transmission of the video data captured by the camera 301 from the movable part 32 to the fixed part 31 is performed by the optical signal transmission means of the rotary joint 1. Therefore, high-quality and large-capacity data transmission can be performed without being affected by noise generated by the conventional sliding contact method between the slip ring and the brush.

  Further, since it is guided to the photodiode 16 through the optical waveguide 19 in the optical signal transmission unit 12 of the rotary joint 1 as a data transmission path of large-capacity serial data, the eccentricity caused by the long-term rotation operation of the movable unit 32 is caused. The quality deterioration of the signal light due to the accompanying optical axis shift can be prevented, and the product life of the surveillance camera device 30 as a whole can be kept long.

  In particular, even if the image size is 1280 × 1024 pixels and each pixel is composed of R, G, B 8-bit data, and this image data is output from the camera 301 at 30 fps, The surveillance camera device 30 can perform data transmission via the rotary joint 1 while ensuring sufficient signal quality.

  INDUSTRIAL APPLICABILITY The present invention is useful for an electric pan head that requires a continuous turning operation over a long period of time.

It is a schematic sectional drawing of the rotary joint as the 1st Embodiment of this invention. It is a schematic sectional drawing of the rotary joint as the 2nd Embodiment of this invention. It is the figure which showed the structure of the surveillance camera apparatus to which any of the rotary joint as each 1st-3rd embodiment of this invention was applied. It is sectional drawing of the optical signal transmission part which combined the optical waveguide, the laser diode, and the photodiode in the 1st Embodiment of this invention. It is the graph which showed the transmission efficiency with respect to the internal-surface reflectance when the dimension between the both end surfaces of the optical waveguide in the 1st Embodiment of this invention is 50 mm. It is the graph which showed the transmission efficiency with respect to the dimension between the both end surfaces of the optical waveguide when the internal surface reflectance of an optical waveguide is 80% in the 1st Embodiment of this invention. It is sectional drawing of the optical signal transmission part which combined the optical waveguide, the laser diode, the photodiode, and the condensing lens in the 2nd Embodiment of this invention. In the second embodiment of the present invention, when the distance from one end face of the optical waveguide 19 to the incident surface of the condenser lens is 0.5 mm as a standard position, the condenser lens is shifted from the center, and the condenser lens FIG. 6 is a graph showing changes in optical transmission efficiency when the beam is displaced in the optical axis direction of emitted light. It is a schematic sectional drawing of the rotary joint as the 3rd Embodiment of this invention.

Explanation of symbols

1, 21, 91 Rotary joint 2 Fixed cylinder part 3 Rotating cylinder part 4a, 4b Hollow bearing 5 Slip ring transmission part 6 Conductive ring 7 Insulating ring 8 Brush 9 Insulating base 10 Rotating part side lead wire 11 Fixed part side lead wire 12, 22, 92 Optical signal transmission unit 13 Laser diode 14 Laser diode substrate 15, 18 Substrate mounting screw 16 Photo diode 17 Photo diode substrate 19 Optical waveguide 19a Optical fiber cable A, B End surface of optical waveguide Aa, Ba Optical fiber cable End face C End face on the rotating part side of the rotating cylinder part D End face on the fixed part side of the rotating cylinder part E Bottom inner wall of the fixed cylinder part P-axis

Claims (5)

A rotary joint that has an end face on one side of a cylindrical rotating part that is rotatably held by a fixed part via a bearing with a predetermined interval, and that transmits light from the rotating part side to the fixed part side. There,
The rotating part is
A cylindrical optical waveguide is provided through the end surface on the other side of the rotating part from the one side so that the central axis passing through the tube coincides with the rotating axis of the rotating part.
A light emitting element is disposed on the other end face so as to face the one end face at a position where the optical axis of the light emitting element coincides with the rotation axis,
The fixing part is
A light receiving element having a light receiving surface with an area larger than the area of the end face of the optical waveguide, the optical axis of the light receiving element being aligned with the rotation axis, and the optical waveguide penetrating to the one side. A rotary joint with a configuration that faces the end face. The fixing part is
The light receiving from the light receiving element having a light receiving surface having an area smaller than the area of the end surface of the optical waveguide through the condensing lens is applied to the light beam emitted from the end surface of the optical waveguide penetrating the one side of the rotating unit. The rotary joint according to claim 1, wherein the rotary joint is configured to collect light on a surface. A rotary joint that has an end face on one side of a cylindrical rotating part that is rotatably held by a fixed part via a bearing with a predetermined interval, and that transmits light from the fixed part side to the rotating part side. There,
The rotating part is
A cylindrical optical waveguide is provided through the end surface on the other side of the rotating part from the one side so that the central axis passing through the tube coincides with the rotating axis of the rotating part.
A light receiving element having a light receiving surface with an area larger than the area of the end surface of the optical waveguide, the end surface on the one side at a position where the optical axis of the light receiving element coincides with the rotation axis. Placed opposite to the
The fixing part is
A rotary joint having a configuration in which a light emitting element is disposed so that an optical axis of the light emitting element coincides with the rotation axis and is opposed to an end face of the optical waveguide penetrating on the one side. The rotating part is
The light receiving from the light receiving element having a light receiving surface having an area smaller than the area of the end surface of the optical waveguide through the condenser lens is emitted from the end surface of the optical waveguide penetrating the other side of the rotating unit. The rotary joint according to claim 3, wherein the rotary joint is configured to collect light on a surface.   The rotary joint according to claim 1, wherein the cylindrical optical waveguide is configured as a bendable optical fiber cable.

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