JPH0224609A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To speed up data transmission by performing the data transmission between a rotary system and a stationary system in the mode of an optical signal. CONSTITUTION:Transmitted light from a light emission part 14 is made incident on a light receiving part through an optical fiber 15 and the data transmission between the rotary system 17 and stationary system 16 is performed in a noncontact state at a high data transmission rate. In this case, one-end surfaces of many optical fibers are made uniform on a plane intersecting orthogonally with the center axis of rotation. Further, the stationary system 16 is provided with many optical fibers and a light receiving part and when the light emission part 14 is provided on the rotary system 17, the data transmission from the rotary system 17 to the stationary system 16 is performed excellently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Field of Industrial Application) The present invention relates to a data transmission device that enables data transmission between a rotating system and a stationary system.

(Prior art) A data transmission device for data transmission includes a ring-shaped electrode and a brush electrode that slides on the ring-shaped electrode, and enables data transmission from a stationary system to a rotating system. There is something. This is called a slip ring device. FIG. 9 shows an example of a conventional slip ring device.

1 is a ring-shaped electrode formed in a ring shape, and 2 is a brush electrode that slides on this ring-shaped electrode 1. 3 is a transmitting section on the data transmitting side, and 4 is a receiving section on the data receiving side. The ring-shaped electrode 1 and the transmitter 3 belong to a stationary system, and the brush electrode 2 and the receiver 4 belong to a rotating system. A single signal supply point P is formed on the ring-shaped electrode 1, and the electrical signal (transmission data) output from the transmitter 3 is supplied from this signal supply point P to the ring-shaped electrode 1. The brush electrode 2 slides on the ring-shaped electrode 1 according to the rotation of the rotating system, and receives the electric signal supplied to the ring-shaped electrode 2 into the receiving section 4.

In this way, data is transmitted from the stationary system to the rotating system.

However, the slip ring device has a drawback in that when the diameter of the ring-shaped electrode increases, the relative speed of the sliding contact portion increases, causing instantaneous interruption of electrical connection, resulting in a decrease in data transmission capability. Even if the rotational speed of the ring electrode or the brush electrode is increased, the same drawbacks as described above will occur. The above disadvantages can be overcome by providing multiple stages of sliding contact parts, but then,
This results in decreased reliability and increased costs.

In addition, as the diameter of the ring-shaped electrode increases, the electric field propagation speed on the ring-shaped electrode becomes a problem, and a certain frequency (
cutoff frequency), signal transmission becomes impossible.

This is due to the following reason.

That is, the electric signal taken into the receiver 4 by the brush electrode 2 is the sum of the signal transmitted on the ring-shaped electrode 1 in the CWh direction and the signal transmitted in the opposite CCW direction. The position of the brush electrode 2 changes with the rotation of the rotating system.

When the brush electrode 2 is located very close to the signal supply point,
The propagation distance on the ring-shaped electrode 1 is 27 cr (r:
radius of the ring-shaped electrode 1), and their phases also differ. If the signal frequency is f and the signal propagation speed in the ring electrode 1 is V, then at the signal frequency f when the relationship v 2f holds, CW
The phase difference between the force direction propagation signal and the CCW direction propagation signal is 1
They become 80 degrees and cancel each other out, so their sum becomes zero. That is, f at this time becomes the cut-off frequency. For example, r=1m, v=1.5x108 m
/sec, the cutoff frequency is 11.9MHz
becomes. In this case, data transmission of 11.98 bits per second is impossible, and safe transmission is possible only up to a fraction of this value.

Here, third generation (also called R/R type) X-ray CT
In a scanner, the X-ray detector rotates together with the X-ray tube, so a data transmission cable connects the stationary system and the rotating system so that X-ray transmission information collected by the rotating system is transmitted to the stationary system. For this reason, the CW force direction must be stopped once every time it scans once in the CCW direction, and then scans in the opposite direction, making continuous high-speed scanning impossible.

Therefore, the inventor @ the present inventor attempted to omit the above-mentioned data transmission cable by applying a slip ring device, and to perform continuous high-speed scanning.

However, in order to perform high-speed continuous scanning in the third generation X-ray CT scanner, it is necessary to transmit data from the rotating system to the stationary system at a data rate of, for example, 12 Mbit per second, and this data transmission is The frequency makes it extremely difficult. Although it is possible to reduce the bit rate per ring electrode by installing a large number of slip ring devices, this inevitably increases the size and cost of the X-ray CT scanner.

(Problems to be Solved by the Invention) As described above, in conventional devices, high-speed data transmission is difficult.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a data transmission device capable of speeding up data transmission.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides data transmission that enables data transmission between a rotating system and a stationary system via optical communication means, One end side of a large number of optical fibers is arranged parallel to the central axis and along the circumferential surface of a cylinder having an axis equal to the central axis, and is in a non-contact state with the end surface of this one end side. The optical communication means is formed by providing a light emitting part for emitting transmitted light at the optical fiber, and providing a light receiving part for receiving the transmitted light from the light emitting part via the optical fiber on the other end side of the optical fiber. be.

(Function) In the present invention, various drawbacks in slip ring devices are eliminated by performing data transmission between the rotating system and the stationary system in the state of optical signals. That is, the transmitted light from the light emitting section is input to the light receiving section via the optical fiber,
Thereby, data transmission between the rotating system and the stationary system can be performed in a non-contact manner and at a high data transmission rate. Here, it is preferable that the end surfaces of one end of the plurality of optical fibers are aligned on a plane perpendicular to the rotation center axis.

In addition, when a large number of optical fibers and a light receiving section are installed in a stationary system, and a light emitting section is installed in a rotating system, data transmission from the rotating system to the stationary system can be performed satisfactorily. The light emitting part can be formed by having a generator or a light emitting diode, and either one of them can transmit 1q of suitable transmitted light.Furthermore, by using one made by arranging a plurality of optical fibers in a sheet shape in advance, It becomes easy to assemble the optical communication means, which is advantageous in terms of cost reduction.When this data transmission device is applied to a third generation X-ray CT scanner, the transmission rate of projection data can be increased, resulting in high speed and High resolution CT scans can be performed sequentially.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

FIG. 1 shows a third generation X-ray C data transmission device according to the present invention.
A case in which the present invention is applied to a T-scanner is shown, and FIG. 2 shows the device of this embodiment viewed from the direction of arrow 20 in FIG. 1.

The X-ray CT scanner has a pedestal (also referred to as a gantry) provided with a shadow hole 7, and this pedestal consists of a rotating part and a fixed part. The rotating part is bent to the rotating system 17, and the fixed part is bent to the stationary system 16.
belongs to

The rotation system 17 is configured as follows.

X on the rotating frame 8 whose rotation center is the center of the enemy shadow hole 7.
Wire tube 5. X-ray detector 11. DAS (Data Acquisition Electronics) 12. A transmission controller 132 and a light emitting section 14 are mounted. The X-ray tube 5 is for emitting X-rays toward the subject 30 placed in the shadow hole 7, and the X-ray detector 11 is for detecting the X-rays that have passed through the subject 30. It is necessary. The DAS 12 collects projection data based on the detection output of the X-ray detector 12, and includes an integrator, an A/D converter, and the like. The projection data collected by this DAS 12 is transmitted to the light emitting section 14 via the transmission controller 13. This light emitting section 14 is made up of an optical fiber 15 which will be described shortly.
It irradiates the transmitted light onto the end face of one end of the LED (
light emitting diode) or a laser generator.

When an LED or a semiconductor laser is used, transmission light can be generated by modulating the drive current with the output of the DAS 12. This drive current modulation is
3. In addition, when a gas laser is applied to the light emitting section 14, the laser light is modulated by the output of the DAS 12, so a modulator is provided on the output side of the gas laser, and the operation of this modulator is controlled by the transmission controller 13. do it like this. Furthermore, the rotating frame 8 and the motor 1
A belt 9 is wound between the rotary frame 8 and the rotary frame 8, and the rotary frame 8 is rotated by the motor 9 in the CW force direction in the CCW direction.

Next, the stationary system 16 will be explained.

The rotating system 17 is rotatably supported by the stationary system 16. This stationary system 16 has one cylindrical body slightly thicker than the diameter of the rotating frame 18, and a large number of optical fibers are densely arranged along the circumferential surface of this cylindrical body 19. The central axis of the cylindrical body 19 is the rotating frame 8
(Rotation system 17) The rotation system coincides with the rotation center, and one end side of a large number of optical fibers 15 is arranged so as to be parallel to the rotation center axis. A large number of optical fibers 15 are arranged so that their one end side end surfaces are aligned on a plane perpendicular to the central axis, and the transmitted light 21 from the light emitting section 14 is transmitted in a non-contact state with respect to this end surface. irradiated. The other ends of the multiple optical fibers 15 are bundled as shown in FIG.
It is connected to the light receiving section 22. The light receiving section 22 includes a lens 25 that condenses optical signals emitted from the other end surfaces of the multiple optical fibers 15 (generated by the light emitted from the light emitting section 14 in FIGS. 1 and 2), and The light-receiving element 24 receives the optical signal focused by the light receiving element 25 and converts it into an electrical signal. The electrical signal obtained by the light receiving element 24 is projection data, and this data is used for image reconstruction processing. In addition, in this embodiment, as shown in FIG.
3, thereby preventing the incidence of disturbance light.

Next, the relationship between the light emitting section 14 and the end surface of one end of the optical fiber 15 will be explained.

As shown in FIG. 5, the transmitted light from the LED or laser generator 14a has some spread. If this is left unattended, the utilization efficiency of the transmitted light 21 will decrease, so a semicylindrical lens 27 is placed after the LED or laser generator 14a, and this lens 27 allows the optical fiber 15 to be
This prevents the transmitted light 27 from spreading in a direction perpendicular to the arrangement direction. Incidentally, since the spread of the transmitted light 27 in the arrangement direction of the optical fibers 15 does not reduce the utilization efficiency of the transmitted light 27, it is left as is as shown in FIG. Therefore, when the lens 27 is interposed, the transmitted light irradiation area on the end face of the optical fiber becomes rectangular as shown by 28 in FIG. 7, and almost all of the transmitted light 21 is taken into the optical fiber 15.

Here, the data transmission device includes a transmission controller 13, a light emitting unit 14 . Optical fiber 15. It has a light receiving section 22,
The optical communication means includes a light emitting section 14. Optical fiber 15. Light receiving part 2
2.

Next, the operation of the above configuration will be explained.

Every minute rotation of the rotation system 17, X-rays 6 are emitted from the X-ray tube 5 toward the subject 30, and the X-rays that have passed through the subject 30 are
It is detected by the line detector 11.

Then, based on the detection no.j of this X-ray detector 11, D
The AS 12 collects projection data. The output of this DAS 12 is taken into the transmission controller 13. The data collection rate is 1000 times per second, and
The number of detection channels of the line detector 11 is 1024, and DA
If the output of S12 is 16 hits, it is 16 Mbi per second.
A data transmission rate of t is required. The output of the DAS 12 is parallel data, which is sent to the transmission controller 13.
The data is converted to serial data at , and then appropriately encoded for asynchronous communication. Transmission light is emitted from the light emitting unit 14 based on this encoded output, and the end face of the optical fiber 15 is irradiated with the transmitted light. Since the end faces of a large number of optical fibers 15 are arranged in a ring shape (see Fig. 1), the transmitted light can be accurately transmitted to the light receiving section 22 without momentary interruption regardless of the rotation of the rotating system 17. obtain.

Generally, the smaller the light receiving element, the faster the response speed.
It is preferable to use a small-sized light-receiving element 24. Even when a small light-receiving element is used, by interposing a lens 25 as shown in FIG. 4, the transmitted light emitted from the end face of the optical fiber 15 can be focused on the light-receiving cable 24.

Here, if a large number of optical fibers 15 are made of plastic, it is advantageous in terms of cost reduction. In the case of a plastic optical fiber, the optical path of the fiber is inclined at an angle θ with respect to the axis, as shown in FIG. The maximum value of the angle θ is about 30°, which does not exceed the acceptance angle of the optical fiber. Further, even if the size of the cylindrical body 19 and the routing of the optical fiber are considered, the length of the optical fiber will not exceed 3 m.

Therefore, the maximum variation l of the optical path length within the optical fiber is 1 max (1-1/cos θ(max) >
8?0.46 (m). The speed of light in the optical fiber is 2
X about 10'3 m/sec, and when the laser beam emitted from the light emitting part 14 is an infinitely spread impulse, the light pulse incident on the light receiving element 24 is 0.46 m / 2 xloEl m/sec =
It will have a spread of 2.3 n5ec. this is,
The response is sufficiently sharp for data transmission of approximately 16 Mbit/sec. Of course, the response speed of the elements themselves applied to the light emitting section 14 and the light receiving section 22 must be considered, but generally a speed of about 16 Mbit/sec can be easily obtained.

Note that the output of the light receiving section 22 is demodulated and then subjected to reconstruction processing.

In this way, according to the device of this embodiment, data is transmitted between the rotating system and the stationary system in the state of optical signals.
Unlike the slip ring device shown in FIG. 9, there is no momentary interruption of electrical connection, and high-speed data transmission is possible. Further, when the present invention is applied to a third generation X-ray CT scanner, high-speed data transmission enables high-speed continuous scanning without increasing the size of the frame or increasing costs. Furthermore, in this embodiment, a large number of optical fibers 15 are arranged at one end side parallel to the rotation center axis of the rotation system 16 and along the circumferential surface of the cylindrical body 19 having an axis equal to the center axis. According to such an optical fiber arrangement, it is easier to fix the optical fibers compared to, for example, arranging multiple optical fibers so that their end faces face the rotation center of the rotating system (that is, radially). It's easy. If a plurality of optical fibers arranged in a sheet shape are curved along the circumferential surface of the cylindrical body 19 in advance, assembly becomes easier.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, data is transmitted from the rotating system 17 to the stationary system 16, but on the contrary, data may be transmitted from the stationary system 16 to the rotating system 17. . In the case of the third generation CT scanner, data transmission from the stationary system 16 to the rotating system 17 includes transmission of control data to each part of the rotating system. Of course, a light emitting section and a light receiving section may be provided in the rotating system 17 and the stationary system 16, respectively, so that data transmission between the rotating system 17 and the stationary system 16 is bidirectional.

Furthermore, if filters that reduce wavelength components other than the wavelength of light used for data transmission are placed at strategic locations, it will be advantageous to prevent disturbance light from entering the system.

In the above embodiment, the other ends of all the optical fibers 15 are connected together to one light receiving section 22, but a large number of optical fibers are divided into several groups, and each group receives light. The light may be condensed into one optical fiber by bundling the fibers, and the optical fibers may be further bundled as many times as the number of groups described above and connected to the light receiving section 22. Alternatively, a dedicated light receiving section may be provided for each of the above groups, and the logical sum of the outputs of the plurality of light receiving sections may be obtained, or alternatively, the light receiving section output may be selected in synchronization with the rotation of the rotating system. You may also do so.

Further, in the above embodiments, the end face of the optical fiber and the light emitting part are opposed to each other, but there may be a case where the end face of the optical fiber and the light emitting part are not opposed to each other. For example, a mirror is interposed between the end face of the optical fiber and the light emitting part, and the mirror reflects the transmitted light from the light emitting part towards the end face of the optical fiber.

Note that the data transmission device according to the present invention can be applied not only to the third generation X-ray CT scanner but also to other devices having a rotating system and a stationary system.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a data transmission device that achieves high-speed data transmission.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an apparatus according to an embodiment of the present invention, and FIG.
An explanatory diagram of the device shown in the figure as seen from the direction of arrow 20, Fig. 3 is an explanatory diagram of the relationship between the optical fiber and the light receiving part, Fig. 4 is an explanatory diagram of the configuration of the light receiving part, and Figs. 5 and 6 are the end faces of the optical fiber. FIG. 7 is an explanatory diagram of the transmission light irradiation area, FIG. 8 is an explanatory diagram of the optical path within the optical fiber, and FIG. 9 is an explanatory diagram of the configuration of the slip ring device.

Claims (7)

[Claims] (1) A data transmission device that enables data transmission between a rotating system and a stationary system via optical communication means, the axis being parallel to and equal to the central axis of rotation of the rotating system. One end side of a large number of optical fibers is arranged along the circumferential surface of a cylindrical body having A data transmission device characterized in that the optical communication means is formed by providing a light receiving section on the other end side of the optical fiber for receiving the transmitted light from the light emitting section via the light emitting section. (2) The data transmission device according to claim 1, wherein the end surfaces of one end of the plurality of optical fibers are aligned on a plane perpendicular to the rotation center axis. (3) The plurality of optical fibers and the light receiving section belong to the stationary system, and the light emitting section belongs to the rotating system.
Or the data transmission device according to 2. (4) The data transmission device according to claim 1, 2 or 3, wherein the light emitting section includes a laser generator. (5) The data transmission device according to claim 1, 2 or 3, wherein the light emitting section includes a light emitting diode. (6) The data transmission device according to claim 1, 2, 3, 4, or 5, wherein the optical fibers in the optical communication means are formed by arranging a plurality of optical fibers in advance in a sheet shape. (7) The rotating system is a gantry rotating section of a third generation X-ray CT scanner, and projection data collected in the gantry rotating section is transmitted to the stationary system via the optical communication means. The data transmission device according to item 1, 2, 3, 4, 5 or 6.