GB2109189A - Apparatus for transferring data between relatively rotating members - Google Patents

Abstract

When data is transmitted between relatively rotating members in the form of electrical signals, this can be done using slip ring contacts. If, however, the information is required to be transmitted in optical form conventional slip rings obviously cannot be used. The problem is particularly acute when the information is to be transmitted along more than one optical line which would become twisted. Figure 2 shows a multiplexer (6) which multiplexes data from a number of inputs (5), each carrying light of different wavelengths lambda 1, lambda 2, lambda 3, lambda 4, onto a common optical line (7). This passes from one member (1) to another member (2) via a rotary joint (8) on the axis of rotation (X). The data is then demultiplexed by a demultiplexer (9) onto optical fibre outputs (10) which correspond to the inputs to the multiplexer (6) and carries the same wavelength lambda 1, lambda 2, lambda 3, lambda 4 as the inputs. Thuds by multiplexing the data only one line need be used and the rotary joint prevents the one becoming twisted. <IMAGE>

Description

SPECIFICATION Apparatus for transferring data between relatively rotating members This invention relates to apparatus for transferring data between relatively rotating members.

When data isto be transmitted between relatively rotating members in the form of electrical signals, this can be done with little difficulty by the use of slip ring contacts. If, however, the information is required to be transmitted in optical form conventional slip rings obviously cannot be used. This problem is particularly acute when the information is to be transmitted along more than one optical line since the latter would become twisted together by the rotary movement of the members, particularly when the rotary movement is predominantly in one sense, i.e., it progresses in one direction rather than being oscillatory.

The present invention arose in an attempt to overcome these problems.

Accordingly this invention provides apparatus for transferring data presented on a plurality of first lines attached for movement with a first member onto respective second lines attached for movement with a second member, the members being relatively rotatable about an axis, the apparatus comprising a common optical line which passes between the members via a rotary joint on the axis, a multiplexer arranged to multiplex the data from the first lines onto the common optical line and a demultiplexer arranged to demultiplex the data from the common line onto the second lines.

By using a single common optical line, which has a rotary joint on the axis of rotation, problems caused bytwisting do not arise and by employing multiplexing techniques different sets or channels of data are able to be transmitted by the common optical line.

Preferably the multiplexer is a colour multiplexer and the demultiplexer is a colour demultiplexer, the separate channels of data being carried by different wavelengths. However, other forms of multiplexing may be used, such as time division multiplexing.

Also it is preferable that inputs to the multiplexer and outputs from the demultiplexer be optical signals, but it is possible to use electrical signals.

In some circumstances it may be desirable for data to pass from the second member to the first member as well as from the first member to the second member in which case the multiplexer will also behave as a demultiplexer and the demultiplexer will also behave as a multiplexer. The data travelling in opposite directions can do so simultaneously or at different times.

One way in which the invention may be performed will now be described by way of example with reference to the accompanying drawings in which Figure 1 is a perspective view of one apparatus constructed in accordance with the invention; and Figure 2 is an axial cross-section of the apparatus shown in Figure 1.

The device shown in the drawings has two members 1 and 2, which are arranged so that they rotate with respect to each other about an axis X.

Two transducers 3 and 4 are mounted on the first member 1.

Information from the transducers 3 and 4 is transmitted along optical fibres 5. Each of the fibres 5 carries one channel of data and uses a different wavelength of light from that of the others, thus enabling colour multiplexing to be used. The optical fibres 5 act as inputs to a colour multiplexer 6, which multiplexes the data from the transducers 3 and 4 onto a single optical fibre or common optical line 7.

This single optical fibre 7 is broken at a rotary joint 8 which allows the members 1 and 2 to rotate without twisting the fibre 7. The two parts of the optical fibre 7 at the joint 8 are preferably not in contact with each other, although some form of refractive-index matching liquid may be present in the interface region.

The optical fibre 7 passes the data to a colour demultiplexer 9 which demultiplexes the signal received onto optical fibres 10 at its outputs.

Each optical fibre 5 input to the multiplexer 6 has a corresponding optical fibre 10 at the outputs of the demultiplexer 9.

Data can thus be transmitted from the first member 1 via the multiplexer 6, the common optical line 7 and the demultiplexer 9 to a second member 2.

In some applications of this device it may be desirable to transmit data both from the first member 1 to the second member 2 and from the second member 2 to the first member 1, either simultaneously or at different times. in this case the multiplexer 6 also acts as a demultiplexer and the demultiplexer 9 will act as a multiplexer.

The device described here uses infra-red light but of course visible and ultra-violet wavelengths may be used and the terms "optical" and "light" when used in this specification are defined as including such ultra-violet and visible wavelengths. Also reference to colour in the colour multiplexer and the colour multiplexer indicate radiation of different wavelengths and may equally well be applied to visible, infra-red and ultra-violet wavelengths.

1. Apparatusfortransferring data presented on a plurality of first lines attached for movement with a first member onto respective second lines attached for movement with a second member, the members being relatively rotatable about an axis, the apparatus comprising a common optical line which passes between the members via a rotary joint on the axis, a multiplexer arranged to multiplex the data from the first lines onto the common optical line and a demultiplexer arranged to demultiplex the data from the common line onto the second lines.

2. Apparatus as claimed in claim 1 and wherein the multiplexer is a colour multiplexer.

3. Apparatus as claimed in claim 2 and wherein the demultiplexer is a colour demultiplexer.

4. Apparatus as claimed in any preceding claim and wherein the plurality of first lines are optical lines.

5. Apparatus as claimed in any preceding claim and wherein the second lines are optical lines.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for transferring data between relatively rotating members This invention relates to apparatus for transferring data between relatively rotating members. When data isto be transmitted between relatively rotating members in the form of electrical signals, this can be done with little difficulty by the use of slip ring contacts. If, however, the information is required to be transmitted in optical form conventional slip rings obviously cannot be used. This problem is particularly acute when the information is to be transmitted along more than one optical line since the latter would become twisted together by the rotary movement of the members, particularly when the rotary movement is predominantly in one sense, i.e., it progresses in one direction rather than being oscillatory. The present invention arose in an attempt to overcome these problems. Accordingly this invention provides apparatus for transferring data presented on a plurality of first lines attached for movement with a first member onto respective second lines attached for movement with a second member, the members being relatively rotatable about an axis, the apparatus comprising a common optical line which passes between the members via a rotary joint on the axis, a multiplexer arranged to multiplex the data from the first lines onto the common optical line and a demultiplexer arranged to demultiplex the data from the common line onto the second lines. By using a single common optical line, which has a rotary joint on the axis of rotation, problems caused bytwisting do not arise and by employing multiplexing techniques different sets or channels of data are able to be transmitted by the common optical line. Preferably the multiplexer is a colour multiplexer and the demultiplexer is a colour demultiplexer, the separate channels of data being carried by different wavelengths. However, other forms of multiplexing may be used, such as time division multiplexing. Also it is preferable that inputs to the multiplexer and outputs from the demultiplexer be optical signals, but it is possible to use electrical signals. In some circumstances it may be desirable for data to pass from the second member to the first member as well as from the first member to the second member in which case the multiplexer will also behave as a demultiplexer and the demultiplexer will also behave as a multiplexer. The data travelling in opposite directions can do so simultaneously or at different times. One way in which the invention may be performed will now be described by way of example with reference to the accompanying drawings in which Figure 1 is a perspective view of one apparatus constructed in accordance with the invention; and Figure 2 is an axial cross-section of the apparatus shown in Figure 1. The device shown in the drawings has two members 1 and 2, which are arranged so that they rotate with respect to each other about an axis X. Two transducers 3 and 4 are mounted on the first member 1. Information from the transducers 3 and 4 is transmitted along optical fibres 5. Each of the fibres 5 carries one channel of data and uses a different wavelength of light from that of the others, thus enabling colour multiplexing to be used. The optical fibres 5 act as inputs to a colour multiplexer 6, which multiplexes the data from the transducers 3 and 4 onto a single optical fibre or common optical line 7. This single optical fibre 7 is broken at a rotary joint 8 which allows the members 1 and 2 to rotate without twisting the fibre 7. The two parts of the optical fibre 7 at the joint 8 are preferably not in contact with each other, although some form of refractive-index matching liquid may be present in the interface region. The optical fibre 7 passes the data to a colour demultiplexer 9 which demultiplexes the signal received onto optical fibres 10 at its outputs. Each optical fibre 5 input to the multiplexer 6 has a corresponding optical fibre 10 at the outputs of the demultiplexer 9. Data can thus be transmitted from the first member 1 via the multiplexer 6, the common optical line 7 and the demultiplexer 9 to a second member 2. In some applications of this device it may be desirable to transmit data both from the first member 1 to the second member 2 and from the second member 2 to the first member 1, either simultaneously or at different times. in this case the multiplexer 6 also acts as a demultiplexer and the demultiplexer 9 will act as a multiplexer. The device described here uses infra-red light but of course visible and ultra-violet wavelengths may be used and the terms "optical" and "light" when used in this specification are defined as including such ultra-violet and visible wavelengths. Also reference to colour in the colour multiplexer and the colour multiplexer indicate radiation of different wavelengths and may equally well be applied to visible, infra-red and ultra-violet wavelengths. CLAIMS

1. Apparatusfortransferring data presented on a plurality of first lines attached for movement with a first member onto respective second lines attached for movement with a second member, the members being relatively rotatable about an axis, the apparatus comprising a common optical line which passes between the members via a rotary joint on the axis, a multiplexer arranged to multiplex the data from the first lines onto the common optical line and a demultiplexer arranged to demultiplex the data from the common line onto the second lines.

2. Apparatus as claimed in claim 1 and wherein the multiplexer is a colour multiplexer.

3. Apparatus as claimed in claim 2 and wherein the demultiplexer is a colour demultiplexer.

4. Apparatus as claimed in any preceding claim and wherein the plurality of first lines are optical lines.

5. Apparatus as claimed in any preceding claim and wherein the second lines are optical lines.

6. Apparatus as claimed in claim 1 and substantially as described with reference to the accompanying drawings.