JP2012119890A - Optical transmission rotary joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmission rotary joint capable of securing communication stability.SOLUTION: An optical transmission rotary joint includes a rotating part held so as to be rotatable relative to a fixed part. The fixed part and the rotating part individually have an optical signal transmission and reception section including a light emitting part, a light receiving part, a reflecting surface for transmission, and a reflecting surface for reception. When optical transmission communication is performed between the optical signal transmission and reception sections disposed opposite to each other, an optical axis of an optical signal is adjusted by changing an angle of the reflecting surface for transmission at two locations where the optical signal transmission and reception sections disposed opposite to each other are positioned at an in-phase position and an out-of-phase position.

Description

  The present invention relates to an optical transmission rotary joint, and more particularly to an optical transmission rotary joint that performs bidirectional signal transmission using an optical signal between a fixed portion and a rotating portion that rotate relatively around one axis.

  As monitoring camera devices that are fixedly installed on an indoor ceiling or the like, many devices that perform monitoring while changing the imaging direction by controlling the pan angle and tilt angle of the camera are widely used. In many cases, an electric pan head that provides a rotation function to a fixed camera having no rotation function is used. In many of such angle-controllable surveillance camera devices, a fixed part fixedly installed on a ceiling or the like and a rotating part rotatable in the pan direction are connected via an electric pan head.

  More specifically, the rotation unit is provided with a tilt drive mechanism that drives the camera in the tilt direction, and this rotation unit is attached to a rotating part of an electric pan head that can rotate in the pan direction. On the other hand, the fixed part of the electric pan head is fixed to the ceiling or the like. Many surveillance camera devices have such a configuration. There is also an apparatus that is configured to electrically rotate only the pan direction by omitting the tilt control function or changing the tilt angle by a manual mechanism. In the monitoring camera device having such a configuration, the video signal output from the camera on the rotating unit is transmitted to the fixing unit via the connection unit between the fixing unit and the rotating unit, and image processing or image processing is performed on the fixing unit. The output interface is converted and output to an external monitor or video signal recording device.

  Several methods are known as a rotational connection method used in such a monitoring camera device. In particular, as a rotational connection method capable of continuously rotating the rotating part in the pan direction, a method of constructing a signal connection path between the rotating part and the fixed part by a sliding contact by a slip ring and a brush is known. . However, this sliding contact method is unstable in electrical contact due to oil film and dust adhering to the contact part between the rotating slip ring and the fixed brush, noise generated due to mechanical contact, There were problems such as deterioration of electrical contact performance due to continuous sliding. In particular, the generation of noise associated with rotation is a problem for video signals, and the occurrence of malfunctions is a problem for control signals such as pan / tilt. Furthermore, since the frequency band that can be transmitted is limited in such a mechanical contact system, it is difficult to transmit high-definition video signals and high-speed data that require a broadband transmission path.

  In order to avoid the adverse effects of the sliding contact method, a rotary joint using non-contact light transmission has also been proposed. This method was originally unidirectional transmission in which the video signal of the camera on the rotating unit is transmitted to the fixed unit. However, a method of sending a control signal of a camera or tilt motor from the fixed unit to the rotating unit, that is, a method of performing non-contact light transmission in both directions has been proposed.

  Patent Literature 1 below discloses an optical transmission rotary joint using two sets of light emitting elements and light receiving elements. In this rotary joint, the light receiving element on the fixed part and the light receiving element on the rotating part are arranged opposite to each other on the rotation axis of the rotating part. The light emitting element is disposed outside the light receiving element so as not to overlap the light receiving element. The optical axis is arranged so that the optical signal emitted from each light emitting element is projected obliquely toward the center of the counterpart light receiving element. However, this method can only handle short distances. In addition, since the light use efficiency is poor, there is a demerit that high power emission is necessary and heat generation is increased.

  Patent Document 2 below discloses an optical transmission rotary joint using a pair of light emitting elements and light receiving elements. In this rotary joint, a light guide member is inserted between the light emitting element and the light receiving element so as to substantially coincide with the rotation axis of the rotating part. Although this light guide member functions as an optical transmission path, a light receiving element having a larger area than the end face of the light guide member is used in order to suppress the influence of the optical axis shift. Or the lens which condenses the light radiate | emitted from the end surface of a light guide member to a light receiving element is used. However, although this system can stably transmit light, it can structurally transmit light only in one direction.

  In order to perform optical transmission, the signal light from the light emitting unit needs to reach the light receiving unit at an angle within the range of the directivity angle. Such an optical axis adjustment technique has also been proposed. Techniques for optical axis adjustment in optical transmission include a method using a sighting device provided on the transmission optical axis, a method for adjusting the optical axis using the reflected light of the corner cube provided in the receiver, and a parabolic reflector. There have been proposed a method using a light source, a method using a pilot light source dedicated to optical axis adjustment, and the like. Patent Literature 3 below discloses a method using a pilot light source dedicated to optical axis adjustment. In this method, an optical signal is received by a four-divided light receiving element (PD), and the optical axis is adjusted based on the difference in the received light level of each divided light receiving element.

JP 2001-44940 A JP 2007-120742 A JP 2000-31908 A

  Optical signal communication is not possible unless the light quantity reaches a certain level within the range of the directivity angle of the optical signal. However, in a humid environment such as outdoor installation, condensation occurs inside the apparatus depending on the amount of water vapor and the temperature contained in the air. If minute water droplets caused by condensation are present on the optical path, the signal light is scattered and the transmission efficiency is remarkably deteriorated. In some cases, communication becomes impossible. As a countermeasure against condensation, a method using a heater (electric heating wire) or a method for eliminating condensation by blowing wind on the condensation surface has been proposed. In Patent Document 3 described above, a dedicated heater is attached to the outside of the device in order to eliminate the condensation on the window, but a dew condensation detection means dedicated to dew condensation detection is required. For this reason, the cost burden is large, leading to an increase in size of the apparatus.

  The objective of this invention is providing the optical transmission rotary joint which can ensure the stability of communication.

  The optical transmission rotary joint of the present invention includes a rotating part (3) rotatably held with respect to the fixed part (2), and is bidirectional between the fixed part (3) and the rotating part (2). The fixed-side optical signal transmitting / receiving unit (10) provided on the fixed unit (2) and the rotating-side optical signal transmitting / receiving unit provided on the rotating unit (3) (10) and a hollow space (11) formed between the two optical signal transmission / reception units (10). The two optical signal transmission / reception units (10) respectively transmit the signal light from the transmission unit (12), the reception unit (14), and the own transmission unit (12) to the optical signal transmission / reception unit ( 10) a reflective surface for transmission (13) that reflects the light toward the other side, and a reflective surface for reception (15) that reflects the signal light from the optical signal transmitting / receiving unit (10) on the other side to the receiving unit (14) of itself. And. The light transmission rotary joint (5) further includes a control unit that controls the rotation of the rotating unit (3) and the angle change of the transmission reflecting surface (13). The rotation axis (CL2) for changing the angle of the first reflecting means (13) for transmission is orthogonal to the rotation axis (CL1) of the rotation unit (3), and the control unit is connected to the fixed unit ( Rotating the rotating part (3) with respect to 2), the two optical signal transmitting / receiving means (10) are moved in the same phase position and opposite phase position with respect to the rotation axis (CL1) of the rotating part (3). The optical axis of the signal light is adjusted by changing the angle of the transmission reflecting surface (13) at a point.

  Here, the control unit detects an abnormal state including a dew condensation state based on the amount of light received by the light receiving unit (14) at each of the same phase position and the opposite phase position, and detects an abnormal state. Sometimes, it is preferable to heat the heating means provided on the reflective surface for transmission (13) and the reflective surface for reception (14).

  According to the optical transmission rotary joint of the present invention, the optical axis adjusting mechanism for controlling the angle of the reflecting surface is provided on the optical path to reduce the size of the apparatus, and the optical signal transmitting / receiving unit provided in the fixed unit and the rotating unit, respectively. The optical axis can be adjusted efficiently simply by acquiring the received light quantity at the same phase position and opposite phase position with respect to the rotation axis.

  If the heating means described above is provided, an abnormal state including a dew condensation state on the reflecting surface can be detected by utilizing the optical axis adjustment means, and further, the dew condensation can be eliminated by controlling the heating means.

It is a block diagram of embodiment of an optical transmission rotary joint. (A) And (b) is explanatory drawing of the optical signal transmission in the said embodiment. (A)-(d) is explanatory drawing of the optical axis adjustment of the optical signal transmission in the said embodiment. (A) is a graph which shows the relationship between the reflective surface angle X and the received light quantity Y explaining the method of obtaining the adjustment point at the time of optical axis adjustment in the above embodiment, and (b) is the dew condensation state of the reflective surface. 5 is a graph showing a relationship between a reflection surface angle X and a received light amount Y. It is an expanded side view of the reflective surface angle change mechanism in the said embodiment. It is an enlarged side view of the 1st modification of a reflective surface angle change mechanism (reflective surface heating method). It is an enlarged side view of the 2nd modification of a reflective surface angle change mechanism. It is an enlarged side view of the 3rd modification of a reflective surface angle change mechanism. It is a cross-sectional perspective view of the unit which incorporated the electric power transmission mechanism and the rotation mechanism in the optical transmission rotary joint of the said embodiment. It is a block diagram of the rotation dome type surveillance camera with which the optical transmission rotary joint of the said embodiment was integrated. It is a flowchart of the abnormality detection control in the optical transmission rotary joint of the said embodiment.

  In the optical transmission rotary joint of the present embodiment, as shown in FIG. 1, a pair of optical signal transmission / reception units 10 are disposed to face each other with a hollow tube 11 interposed therebetween. A hollow space is formed inside the hollow tube 11. The hollow tube 11 is divided into a fixed part 2 and a rotating part 3 at the center. The fixed portion 2 and the rotating portion 3 may be divided by the hollow tube 11 as shown in FIG. 1 or may be divided between the hollow tube 11 and any one of the optical signal transmitting / receiving units 10. good. Each optical signal transmitting / receiving unit 10 includes an optical signal light emitting unit 12, an optical signal receiving unit 14, a reflection surface 13 that reflects signal light from its own optical signal light emitting unit 12 toward the counterpart optical signal transmitting / receiving unit 10, and A reflection surface 15 is provided for reflecting the signal light from the counterpart optical signal transmission unit 12 toward its own optical signal reception unit 14.

  Each optical signal transmission unit 12 of the present embodiment uses an L1ght Emitting Diode (LED), but a semiconductor laser (LD) or a surface emitting laser (VCSEL) may be used. Photodiode (PD) is used for the optical signal receiver 14.

  The reflective surfaces 13 and 15 are made of a stainless steel plate that has been subjected to a brilliant treatment, but a mirror, a resin with a smooth surface, or a member with a reflective film may be used. The stainless steel sheet that has been subjected to the glittering treatment has features such as excellent corrosion resistance, high strength, easy formation of a mounting shape, and low cost compared to a reflecting surface using glass.

  The hollow tube 11 is made of metal. Specifically, it is a machined brass, and the hollow inner surface is finished as a machined surface with less unevenness, and reflection on the hollow inner surface is also used. However, basically, it is sufficient that a space through which an optical signal passes is secured inside the hollow tube 11, and the hollow tube 11 may be made of resin or glass.

  Next, transmission of an optical signal will be described. As shown in FIG. 2A and FIG. 2B, the signal light emitted from the LED 12 at a constant radiation angle reaches the counterpart PD 14 while spreading. Here, the center axis (the one-dot chain line in the figure) of the spreading signal light is reflected by the reflecting surface 13 and then reaches θ1 (FIG. 2A) so as to reach the intersection 18 between the counterpart reflecting surface 15 and the rotation axis CL1. ) And θ2 (FIG. 2B) are set. Therefore, when the signal light reaches the intersection 18, half of the spread signal light is reflected again by the reflecting surface 15 and reaches the PD 14. By setting the optical axis in this way, regardless of the rotational positional relationship between the fixed portion 2 and the rotating portion 3, half of the signal light spread when the signal light reaches the intersection 18 is reflected on the reflecting surface. It is reflected at 15 and always sent to the PD 14. Therefore, the light quantity fluctuation | variation by rotation of the rotation part 3 with respect to the fixing | fixed part 2 is suppressed, and stable communication is implement | achieved.

  Further, even when the distance between the pair of opposing optical signal transmission / reception substrates (optical signal transmission / reception unit 10) is different (FIGS. 2A and 2B), it is easy to change the angle of the reflecting surface 13. Yes (see θ1, θ2). Further, since the rotation axis CL2 of the reflection surface 13 and the rotation axis CL1 of the rotation unit 3 with respect to the fixed unit 2 are arranged to be orthogonal to each other, the position of the reflection surface 13 (15) viewed from the direction of the rotation axis CL1 does not change. (In other words, the rotation axis CL2 only rotates around the intersection with the rotation axis CL1). For this reason, the light quantity fluctuation due to the rotation of the rotating unit 3 does not occur. As described above, the signal light emitted from the LED 12 is reflected twice and reaches the PD 14, so that not only the reflection surface 13 is used for optical axis adjustment but also the light-emitting / receiving components such as the LED 12 and the PD 14 are used as the rotation axis CL2. Therefore, the structure can be thinned (downsized).

  Next, optical axis adjustment will be described. As described above, the optical axis of the signal light emitted from the LED 12 is designed to pass through the intersection 18 after being reflected by the reflecting surface 13. If the optical axis is adjusted so as to pass through the intersection point 18, half of the signal light spread by the radiation angle is always reflected toward the PD 14 regardless of the rotational position (phase) of the rotating unit 3. However, if the optical axis is deviated from the intersection point 18 toward the PD 14 side, a lot of light is reflected toward the PD 14 at this rotational position (phase). The reflected signal light is significantly reduced. Conversely, the same applies when the optical axis is shifted toward the LED 12 side.

  Therefore, the optical axis is adjusted so that the optical axis of the signal light passes through the intersection 18 by changing the angle of the reflecting surface 13. The procedure for adjusting the optical axis will be described with reference to FIGS. 3 (a) to 3 (d). The optical axis adjustment is performed in a state where the communication path between the fixed unit 2 and the rotating unit 3 is not established. Each step of the optical axis adjustment proceeds to the next step at a predetermined time. First, as shown in FIG. 3A, in step 1, an angle detection function for detecting the rotation angle of the rotating unit 3 with respect to the fixed unit 2 by turning on the power or pressing a reset switch (not shown). The light emitting unit (LED 12) and the light receiving unit (PD 14) are in the same phase (the same position with respect to the rotation axis CL1) in the rotating unit 2 and the rotating unit 3. As the angle detection function, an encoder may be provided, or a control signal for a stepping motor that rotates the rotating unit 3 may be used. In the state shown in FIG. 3A, the LED 12 on the rotating unit 3 is caused to emit light, the angle of the reflecting surface 13 on the rotating unit 3 is changed, and the reflecting surface angle information is sequentially modulated and placed on the signal light. . The signal light is received by the PD 14 on the fixed unit 2, and correlation data in the same phase state between the angle of the reflection surface 13 on the rotating unit 3 and the light reception level of the PD 14 on the fixed unit 2 side is acquired.

  Next, as shown in FIG. 3B, in step 2, the rotation unit 3 is rotated by 180 ° using the angle detection function, and the light emitting unit (LED 12) and the light receiving unit in the rotation unit 2 and the rotation unit 3. (PD14) is set to the opposite phase. In the state shown in FIG. 3B, the LED 12 on the rotating unit 3 is caused to emit light, the angle of the reflecting surface 13 on the rotating unit 3 is changed, and the reflecting surface angle information is sequentially modulated and placed on the signal light. . This signal light is received by the PD 14 on the fixed unit 2, and correlation data between the angle and the light quantity in the opposite phase state are acquired. When the correlation data in the in-phase state acquired in step 1 and the correlation data in the anti-phase state acquired in step 2 are combined, a graph as shown in FIG. 4A is obtained. From the graph of FIG. 4A, an adjustment point Q corresponding to the angle of the reflecting surface 13 whose optical axis passes through the intersection 18 is obtained. Ideally, the adjustment point Q coincides with the angle of the design center.

  Subsequently, in step 3, the obtained angle information of the adjustment point Q is modulated into signal light, and this time, the rotating unit 3 is rotated at a predetermined speed at least once while causing the LED 12 on the fixed unit 2 to emit light. Even if the optical axis from the fixed part 2 to the rotating part 3 is not adjusted by rotating the rotating part 3 once while causing the LED 13 on the fixed part 2 to emit light, any angle within one rotation Thus, the signal light reaches a predetermined light amount or more. For this reason, the reflecting surface angle information of the adjustment point Q can be transmitted from the fixed unit 2 to the rotating unit 3. The rotating unit 3 sets the angle of the light-emitting reflecting surface 13 on the rotating unit 3 to an angle corresponding to the adjustment point Q based on the information transmitted from the fixed unit 2.

  Next, as shown in FIG. 3C, in step 4, the phase is returned to the same phase again, the LED 12 on the fixed part 2 is caused to emit light, and the angle of the reflecting surface 13 on the fixed part 2 is changed. The reflection surface angle information is modulated and placed on the signal light. This signal light is received by the PD 14 on the rotating unit 3, and correlation data between the angle and the light amount in the same phase state is acquired.

  As shown in FIG. 3D, in step 5, the rotating unit 3 is rotated 180 ° to have an opposite phase, and similarly, the LED 12 on the fixing unit 2 is caused to emit light and the reflecting surface 13 on the fixing unit 2 is illuminated. The angle is changed, and reflection surface angle information is sequentially modulated and placed on the signal light. This signal light is received by the PD 14 on the rotating unit 3, and correlation data between the angle and the light quantity in the opposite phase state are acquired. Similarly, the angle of the reflecting surface 13 corresponding to the adjustment point Q can be acquired from the correlation data in the in-phase state acquired in step 4 and the correlation data in the anti-phase state acquired in step 5.

  Subsequently, in step 6, the angle information of the obtained adjustment point Q is modulated into signal light, and this time the LED 12 on the rotating unit 3 is caused to emit light, and the rotating unit 3 is rotated at least once at a predetermined speed. The obtained angle information is reflected on the reflecting surface 13 for light emission on the fixed portion 2 (set to an angle corresponding to the adjustment point Q). The optical axis adjustment is thus completed. Note that during the optical axis adjustment described above, the rotation of the rotating unit 3 relative to the fixed unit 2 and the angle adjustment of the reflecting surface 13 are controlled by the control unit.

  Steps 1 to 3 are steps for adjusting the angle of the reflecting surface 13 for light emission on the rotating unit 3, and steps 4 to 6 are steps for adjusting the angle of the reflecting surface 13 for light emitting on the fixed unit 2. Steps 4 to 6 may be performed first, and then steps 1 to 3 may be performed. In addition, the measurement order of the same phase and the opposite phase may be switched. In addition, device driving or optical so that the return light reflected by the rotating unit 3 and incident on the PD 14 on the fixing unit 2 is sufficiently smaller than the signal light from the original rotating unit 3 is reflected by the rotating unit 3. If the system is set, steps 1 to 3 and steps 4 to 6 can be performed simultaneously (the same applies to the return light to the rotating unit 3). In this embodiment, since the same optical signal transmitting / receiving unit is used for the fixed unit 2 and the rotating unit 3, the wavelength of the signal light from the fixed unit 2 to the rotating unit 3 and the signal light from the rotating unit 3 to the fixed unit 2 are The wavelength is the same. However, if the wavelength of the optical signal from the rotating unit 3 to the fixed unit 2 and the wavelength of the optical signal from the fixed unit 2 to the rotating unit 3 are changed, light isolation is ensured by using devices corresponding to different wavelengths. Steps 1 to 3 and Steps 4 to 6 can be performed simultaneously.

  Next, dew condensation detection will be described. When condensation occurs on the reflecting surfaces 13 and 15, the correlation between the amount of light obtained by adjusting the optical axis and the angle of the reflecting surface is a state in which the amount of light falls and the amount of light changes gently as shown in FIG. become. A threshold is set in advance for the amount of light, and if the amount of light does not reach the threshold, it is determined that the condensation state is present. When it is determined that the condensation state is present, the reflecting surfaces 13 and 15 are heated to eliminate the condensation. If the reflective surfaces 13 and 15 are not improved by heating, a warning is issued as an abnormal state due to factors other than condensation such as the lifetime of the device or mechanical damage.

  In the present embodiment, a value that is 1/4 of the design value of the amount of received light is set as the threshold value. The threshold value is finally set through an environmental test in consideration of the type of light emitting / receiving device, performance variation, arrangement, installation environment, and the like. Regarding the radiation intensity of the LED 12 used in the present embodiment, the minimum value is defined as a half value of the standard value. For this reason, the threshold is determined so that signal transmission can be achieved even with half the radiation intensity of the LED having the weakest radiation intensity due to performance variations. Further, according to the above-described configuration, it is possible to detect an abnormal state of the optical transmission system including a dew condensation state. Furthermore, when only one of the bidirectional optical transmission lines is below the threshold value, only one is abnormal. The above-described configuration, such as determining that it is, is useful for investigating an abnormal state. Moreover, the above-described configuration is useful for investigating the cause of the abnormal state, such as whether the abnormality is caused by condensation or a failure due to the method of reducing the amount of light.

  Next, the angle adjustment mechanism will be described. As shown in FIG. 5, in the angle changing mechanism of the reflecting surface 13 in the present embodiment, the movable end of the reflecting plate 13a having the reflecting surface 13 is biased in advance to one side by a spring 13b. The output rotating shaft 13d of the motor 13c is configured as a lead screw, and changes the angle of the reflecting plate 13a (reflecting surface 13) via a moving member 13e screwed to the output rotating shaft 13d. A heater 13f is provided on the back surface of the reflecting plate 13a and is connected to the heating control unit 13g. A heater 15f is also provided on the back surface of the reflecting plate 15a having the reflecting surface 15 for receiving light. When condensation occurs on the reflection plates 13 and 15, the heating control unit 13g energizes the heaters 13f and 15f to generate heat and evaporates the condensation to eliminate the condensation.

  FIG. 6 shows a modification having heating means different from the angle changing mechanism of FIG. Since the reflecting plate 13a is movable, a heater 130f is disposed near the back surface of the reflecting plate 13a, and heat is conducted to the reflecting surface 13 by heat radiation. There is no need to connect wires so as to follow the movement of the reflector 13a, and the heater 130f can be fixedly installed, so that higher reliability can be ensured.

  7 and 8 show a modification in which the angle of the reflecting surface 13 is changed with a structure different from the angle changing mechanism of FIG. In the modification of FIG. 7, the angle of the reflecting plate 13a (reflecting surface 13) is changed by a pinion gear 130c that is rotationally driven by a motor (not shown) and a rack 130e that is linearly moved by the pinion gear 130c. The In the modification of FIG. 8, the cam 13j is rotated by the motor 13h via the reduction gear 13i, and the angle of the reflecting plate 13a (reflecting surface 13) is changed by this cam. The angle changing mechanism is not limited to these modified examples, and any mechanism that can reliably change the angle of the reflecting surface 13 may be used. The heating of the heaters 13f (130f) and 15f described above is controlled by the controller described above.

  FIG. 9 shows a unit in which the above-described rotary joint capable of bidirectional optical signal transmission is combined with a power transmission unit 20 by electromagnetic induction and a direct drive motor (DD motor) 30 having a hollow rotating shaft as a rotation driving means. Show. Concentric ferrite cores 22 and 23 incorporating windings are separated by a slight gap (in this case, 0.5 mm) around the outer periphery of the hollow tube 11 provided between the optical signal transmitting / receiving units 10 arranged opposite to each other. Are arranged. Non-contact power transmission is performed from the fixed portion 2 to the rotating portion 3 between the ferrite cores 22 and 23. The LED 12, the PD 14, and the reflecting surfaces 13 and 15 are mounted on the substrate 17. Reflection surface of the reflector 13 described above

  The rotating shaft of the DD motor 30 also serves as the hollow tube 11. By combining power transmission by electromagnetic induction and optical signal transmission, a rotary joint that can transmit signals and power from the fixed part 2 to the rotating part 3 in a non-contact manner, except for parts related to rotation and holding such as bearings. realizable. Furthermore, since a power transmission mechanism is not required by employing a DD motor, the size can be reduced and the operation sound can be extremely quiet.

  FIG. 10 shows a dome-type rotary camera unit 1 incorporating the DD motor integrated rotary joint 5 shown in FIG. The rotating part 3 is rotatably held with respect to the fixed part 2. A camera 4 is provided on the rotating unit 3 via a tilt mechanism unit (not shown). The camera 4 is protected by an acrylic transparent dome 6. The fixed part 2 is fixed to the ceiling 7. A DD motor integrated rotary joint 5 is mounted between the fixed portion 2 and the rotating portion 3, and the rotating portion 3 (camera 4) can rotate indefinitely relative to the fixed portion 2. Video data photographed by the camera 4 is converted from a parallel signal to a serial signal by the signal conversion unit 8 so as to be suitable for optical signal transmission, and then rotated as a signal light through the pair of optical signal transmission / reception units 10 described above. 3 to the fixed part 2.

  Since there is no need to rotate infinitely regarding tilt rotation, the tilt mechanism (including the tilt motor) is connected to the optical signal transmitting / receiving unit 10 of the rotating unit 3 by a coaxial cable. The serial signal transmitted to the fixed unit 2 is converted into a parallel signal again by the signal converting unit 9 and then sent to a control device such as a personal computer (PC) connected to an external network. In addition, since the pan / tilt rotation control unit is mounted on the rotation unit 3, the motor control signal is sent from the fixed unit 2 to the rotation unit 3 together with the camera control signal. That is, the signal is bidirectionally transmitted by the signal light. Electric power necessary for driving the camera 4, the pan rotation DD motor 30, and the tilt rotation motor is supplied from the fixed unit 2 to the rotation unit 3 by a non-contact power transmission unit 20 incorporated in the rotary joint 5. .

  Next, the above-described abnormality detection control will be described with reference to the flowchart shown in FIG. First, based on the correlation data (see FIGS. 4A and 4B) between the angle and the amount of light obtained as a result of the optical axis adjustment described above, it is determined whether the amount of received light is equal to or less than a threshold value. (Step S1). If the optical axis is adjusted correctly, the amount of received light should not be less than the threshold value. If step S1 is negative, that is, if the amount of received light exceeds the threshold value, it is assumed that no abnormality has occurred, and the process of step 1 is continued (always monitoring the occurrence of abnormality). On the other hand, if step S1 is affirmed, that is, if the amount of received light is equal to or smaller than the threshold value, an abnormality may have occurred, and first, the angle of the reflecting surface 13 is stored in the memory (step S3).

  Then, after step S3, the angle of the reflecting surface 13 is sequentially changed to obtain correlation data (light reception amount distribution) between the angle and the amount of light (step S5). Next, the adjustment point Q described above is obtained based on the correlation data acquired in step S5, and it is determined whether or not the amount of light received at the adjustment point Q is equal to or less than a threshold value (step S7). That is, step S1 is affirmed. In such a case, the optical axis adjustment is performed again in steps S3 to S7, and it is determined whether or not the abnormal state as shown in FIG.

  If step S7 is negative, that is, if the amount of received light exceeds the threshold value, it is assumed that no abnormality has occurred, and the process returns to step 1 (the occurrence of abnormality is constantly monitored). On the other hand, if step S7 is affirmed, if step S1 is affirmed, that is, if the amount of received light is less than or equal to the threshold value, an abnormality may occur even after readjustment of the optical axis. Information is called, and the angle of the reflecting surface 13 is returned to the initial angle (initial angle) (step S9).

  After step S9, a control signal (ON) is sent to the heating device, and the heaters 13f (130f) and 15f generate heat (step S11). Heat generation of the heaters 13f (130f) and 15f is continued for a certain time (step S13), and condensation that seems to be attached to the reflecting surfaces 13 and 15 is evaporated. After a certain time has elapsed, it is determined whether or not the amount of received light is greater than or equal to a threshold value (step S15). When step S15 is affirmed, that is, when the amount of received light is greater than or equal to the threshold value, it can be determined that the condensation has evaporated and the abnormality has been resolved, so a control signal (OFF) is sent to the heating device and the heater 13f (130f). , 15f is stopped (step S17). Thereafter, the monitoring of the amount of received light is continued (step S19).

  On the other hand, if step S15 is negative, that is, if the amount of received light is less than the threshold value, it can be determined that the abnormal state is not due to condensation but abnormal due to other factors. In this case, first, a control signal (OFF) is sent to the heating device, and heating of the unnecessary heaters 13f (130f) and 15f is stopped (step S21). Thereafter, a warning signal indicating that an abnormality has occurred is sent out (step S23).

  In this embodiment, the rotation axis CL2 of the reflection surface 13 is orthogonal to the rotation axis CL1 of the rotation unit 3, and the angle of the reflection surface 13 provided in the optical path is controlled while monitoring the amount of received light to adjust the optical axis. Done. When adjusting the optical axis, the transmission / reception unit 10 of the rotation unit 3 and the transmission / reception unit 10 of the fixed unit 2 are in the same phase and in the opposite phase with respect to the rotation axis CL1 (that is, on the same side with respect to the rotation axis CL1). The optimum angle (adjustment point Q) is determined while monitoring the amount of received light at two locations (when located at the opposite side and when located at the opposite side).

  Therefore, according to the present embodiment, the optical axis can be adjusted with information obtained by measuring the light quantity of the minimum necessary (two places). In addition, even when the transmission distance of the signal light is different, it can be easily handled. In addition, the conventional optical transmission rotary joint has a shorter optical transmission distance in the rotary joint than the optical transmission between multiple devices separated by a space. However, the amount of light was increased so that communication could be established. However, this is not necessary in this embodiment. Furthermore, in the conventional optical axis adjustment between a plurality of devices, it is necessary to measure the amount of light while changing the angle of the reflecting surface around the two rotation axes, so it is necessary to measure the amount of light at least at three or more points. . However, according to the present embodiment, since the rotation axis CL2 and the rotation axis CL1 are orthogonal to each other, the optical axis can be adjusted only by changing the angle of the reflection surface 13 about only one rotation axis CL2. Furthermore, according to the present embodiment, optical characteristic fluctuations due to the transmission reflecting surface 13 and the reception reflecting surface 15 accompanying the rotation of the rotating unit 3 can be minimized, and suitable communication stability can be realized.

  Moreover, according to this embodiment, the abnormal state including a dew condensation state is detectable using the optical axis adjustment function mentioned above. Further, the reflection surfaces 13 and 15 can be heated by the heaters 13f (130f) and 15f to remove condensation. Therefore, the dew condensation on the reflecting surfaces 13 and 15 can be prevented even in a humid environment, and the stability of optical communication can be ensured. As described above, conventionally, a method for removing condensation by heat generation and a method for removing condensation by blowing air have been proposed, but all require dedicated condensation detection means. In addition, there is a problem that the optical performance is deteriorated due to dust adhering to the reflection surface by the air blowing. However, in this embodiment, since the optical axis adjustment function is used, it is not necessary to provide a dedicated dew condensation detection means. Moreover, according to this embodiment, dew condensation can be eliminated without impairing the optical performance of the reflecting surfaces 13 and 15.

CL1 (rotary joint) rotation axis CL2 (reflection surface) rotation axis 1 rotation dome camera unit 2 (rotary joint) fixed part 3 (rotary joint) rotation part 4 camera 5 rotary joint 6 dome 7 ceiling 8 rotation side signal Conversion unit 9 Fixed side signal conversion unit 10 Optical signal transmission / reception unit 11 Hollow tube 12 Light emitting unit (LED)
13 Reflecting surface for transmission 14 Light receiving part (PD)
15 Receiving reflecting surface 17 Substrate 18 Intersection point of optical axis and reflecting surface rotation axis 20 Power transmission unit 22 Fixed ferrite core 23 Rotating ferrite core 30 Direct drive motor

Claims (2)

In an optical transmission rotary joint that includes a rotating unit that is rotatably held with respect to a fixed unit, and that transmits a bidirectional optical signal between the fixed unit and the rotating unit,
A fixed-side optical signal transmitting / receiving unit provided on the fixed unit;
A rotation-side optical signal transmission / reception unit provided on the rotation unit;
A hollow space formed between the two optical signal transmitting and receiving units,
The two optical signal transmission / reception units are a transmission unit, a reception unit, a transmission reflection surface that reflects signal light from the transmission unit of the transmission unit toward the optical signal transmission / reception unit on the other side, and a counterpart side, respectively. A receiving reflecting surface for reflecting the signal light from the optical signal transmitting / receiving unit to the receiving unit of itself,
The optical transmission rotary joint further includes a control unit that controls rotation of the rotating unit and angle change of the reflecting surface for transmission,
The rotation axis for changing the angle of the first reflecting means for transmission is orthogonal to the rotation axis of the rotation unit,
The control unit rotates the rotating unit with respect to the fixed unit to cause the two optical signal transmitting / receiving units to reflect the transmission reflection at two positions of an in-phase position and an anti-phase position with respect to the rotation axis of the rotating unit. An optical transmission rotary joint, wherein the optical axis of the signal light is adjusted by changing the angle of the surface.   The control unit detects an abnormal state including a dew condensation state based on the amount of received light received by the light receiving unit at each of the in-phase position and the reverse phase position, and when the abnormal state is detected, the transmission reflection is detected. The optical transmission rotary joint according to claim 1, wherein heating means provided on a surface and the receiving reflecting surface is heated.

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