GB1561855A

GB1561855A - Emote control apparatus

Info

Publication number: GB1561855A
Application number: GB2428/77A
Authority: GB
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1978-01-18
Filing date: 1978-01-18
Publication date: 1980-03-05

Description

(54) IMPROVEMENTS IN OR RELATING TO REMOTE CONTROL APPARATUS (71) I, SECRETARY OF STATE FOR DEFENCE, London, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to remote control apparatus and particularly to apparatus for enabling a receiver to determine its position in directions normal to an axis from a Co- operating transmitter.

According to one aspect of this invention there is provided remote control apparatus of the aforesaid type including a transmitter comprising a radiation means for generating two non collinear, non-parallel strips of radiation and for forming images of these suips at infinity, b. rotation means for rotating the images of the strips of radiation in a circular path so that during their motion along the path the images are continuously moved to positions in which the image of each strip lies parallel to all of its previous positions, c. modulation means for modulating the radiation, d. modulation sweeping means for sweep ing the modulation of the radiation through a pre-determined range in the period taken to complete one rotation of the images by the rotation means, and a receiver comprising a. a detector for detecting the modulation of the radiation present in each image as it passes the detector, b. modulation discrimination means for dis criminating between each of the detected modulations and a predetermined modu lation and for generating difference sig nals indicative of the difference between the detected modulations and the cor responding predetermined modulations.

According to another aspect of this invention there is provided a transmitter, for remote control apparatus of the aforesaid type, comprising a. radiation means for generating two non collinear, non-parallel strips of radiation and for forming images of these strips at infinity, b. rotation means for rotating the images of the strips of radiation in a circular path so that during their motion along the path the images are continuously moved to positions in which the image of each strip lies parallel to all of its previous positions, c. modulaion means for modulating the radiation, d. modulation sweeping means for sweeping the modulation of the radiation through a predetermined range in the period taken to complete one rotation of the images by the rotation means.

Conveniently the strips of radiation are arranged to be mutually orthogonal in a substantially L-shape configuration.

The radiation may be provided by infrared sources. Conveniently these sources may be gallium aluminium arsenide lasers.

The modulation means may be for modulating the amplitude of the radiation and the modulation sweeping means may be for sweeping the frequency of the amplitude modulation of the radiation.

The rotation means may include a rotatably mounted wedge shaped prism and this prism may be a Risley prism where it is necessary to maintain the sensitivity of the apparatus with increasing distance between the transmitter and receiver. The sensitivity may, alternatively, be maintained by providing means for controlling the modulation sweep means so that in use, the range through which the modulation is swept is controlled in accordance with the distance between the transmitter and receiver. The sensitivity may, alternatively, be maintained by providing the receiver with means for amplifying the difference signals in accordance with the distance between the receiver and transmitter.

The invention will now be described by way of example only with reference to the drawings accompanying the Provisional Specification, of which Figure 1 shows an embodiment of remote control apparatus in accordance with the invention, Figure 2 shows the geometrical relationship between the detector and the images of the strips of radiation.

Figure 1 shows a transmitter 1 and a receiver 2. The transmitter includes radiation means comprising two gallium aluminium arsenide lasers 3 (by way of example a suitable type is manufactured by STC under type number STC243Ohetero-junction Galas laser) which radiate along their length, an appropriate power supply (not shown) and a projection lens 14. An amplitude modulating circuit 4 is provided and the frequency of the amplitude modulation is swept by a frequency sweep unit 5. The lasers 3 are arranged to be mutually orthogonal in an L shape configuration (see Figure 2) and are positioned at the focus of the projection lens 14 so that it forms images at infinity of the strips of radiation emitted by the lasers 3.These images are rotated in a circular path, so that during their motion they are continuously moved to position in which the image of each strip lies parallel to all of its previous positions, by rotation means which comprises a prism 6 which is wedge shaped in cross-section and is transparent to the radiation emitted by the lasers 3, and an electric motor 7. The motor 7 has an output shaft 8 on which is rigidly mounted a gear wheel 9. The prism 6 has a circular peri meter and is rotatably mounted on bearings (not shown). The perimeter is provided with a prism housing 10 which has gear teeth formed in its outer surface which engage with the gear wheel 9. The frequency sweep unit 5 is linked to rotation of the prism housing 10 so that each frequency sweep is synchronised to each revolution of the prism 6.

The lasers 3 are positioned so that the axis of rotation 27 of the prism 6 passes through the point at which the two strips of radiation, if extended, would meet. The receiver includes a detector 11 which is sensitive to the frequency of the amplitude modulation of the radiation emitted by the lasers 3 and produces electrical signals indicative of said frequency. The signals are fed to a frequency discriminator 12 which detects the frequencies of the received signals and produces outputs on line 13 proportional to the deviations of the said signals from the centre frequencies of the modulation ranges.

Figure 2 shows the images 3' of the strips of radiation emitted by the lasers 3 and the position of the detector 11. The images 3' may be considered to be formed in a plane which includes the detector 11 and which is normal to the axis of symmetry of the pro jection lens 14. The axis of symmetry of the lens 14 is collinear with the axis of rotation 27 of the prism 6. In Figure 2, to aid clarity, the images 3' are shown stationary and the path 15 of the detector 11 relative to the two images 3' has been plotted. The dotted circule 26 shows the relative path of the detector 11 when it is on the axis of rotation 27 of the prism 6. When the detector 11 is in this position the frequency it detects from each image 3' is the centre frequency of each modulation range.The relative path 15 is followed by the detector 11 when it is displaced from the axis 17 by displacements x and y in the cartesian co-ordinate directions X and Y. If the prism is rotated in a clock wise direction, as viewed from the projection lens 14, at an angular speed of w radians per second then the detector may be con sidered to rotate along the relative path 15 in an anticlockwise direction at the same angular speed w.The frequencies of the modulation of the amplitude of the radiation emitted by the lasers 3 and consequently pre sent in their images 3' may be written as fx and f, for the images which lie along the X ordinate and Y ordinates respectively of Figure 2 and: f=f,-av (1) f,=f+b(wt-ir/2) (2) where a and b are constants and t is the time measured from when the detector, if on the axis 27 and therefore following the rela tive path 26 would cross the image 3' which lies on the X ordinate. fl and fs are the centre frequencies of the modulation ranges for the images which lie along the X ordinate and Y ordinate respectively.

If however the detector 11 is in the position shown in the figure that is displaced by displacements x and y from the axis 27 then the times at which the detector crosses the images 3' lying on the X and Y ordinates are tx and t, respectively and may be written: wt=-sin-1(y/l) (3) wty=7r/21+sin-l(x/l) (4) where 1 is the distance from the detector 11 to the points at which the detectors relative path 15 crosses the images 3'.By substituting the times given by the equations (3) and (4) into the equations (1) and (2) respectively yields F, and F, which are the frequencies detected by the detector, therefore: F=f, +a sin-l(y/l) (5) F,=f2+b sin-l(x/l) (6) However if the displacements x and y are small compared with 1 equations (5) and (6) can be written: ay Fx=l + (7) I bx Fy=f2+ (8) I The frequency discriminator 12 detects the deviation of the detected frequencies Fx and Fy from the centre frequencies fl and f2 respectively and hence determines the displacements x and y. The constants a and b, and the radius of the relative path 1 of the detector are known.However l varies with the distance between the transmitter and receiver and consequently the sensitivity of the apparatus decreases with range. This may be compensated for, if required, in several ways. Firstly 1 may be varied by the use of a Risley prism in place of the single prism 6. A Risley prism is a combination of two thin prisms of equal power which can be rotated in opposite directions in their own plane and is equivalent to a single prism of variable power. Risley prisms are described and illustrated on pages 23 and 24 of the third edition of Fundamentals of Optics by Jenkins and White and published by the McGraw-Hill Book Co Inc.

Secondly a and b may be varied at the transmitter by varying the range of the frequency sweep performed by the frequency sweep unit 5. Thirdly the signals produced by the frequency discriminator 12 may be amplified by circuiuy whose gain varies with the distance between the transmitter and receiver.

By way of example only the parameters of the embodiment shown in Figure 1 were: Wavelength of radiation 850 nanometres Modulation triangular pulses of 100 nano-seconds width Carrier frequency f1 = 30 KHz; f,=40 KHz Modulation frequency range t 2 KHz Frequency of rotation of images 25 Hz Semi cone angle of cone of rotation 10 Milliradians Range of control up to 5 Km WHAT I CLAIM IS: 1.Remote control apparatus of the afore said type including a transmitter comprising a. radiation means for generating two non collinear, non-parallel strips of radiation and for forming images of these strips at infinity, b. rotation means for rotating the images of the strips of radiation in a circular path so that during their motion along the path the images are continuously moved to positions in which the image of each strip lies parallel to all of its previous positions, c. modulation means for modulating the radiation, d. modulation sweeping means for sweeping the modulation of the radiation through a predetermined range in the period taken to complete one rotation of the images by the rotation means, and a receiver comprising a. a detector for detecting the modulation of the radiation present in each image as it passes the detector, b. modulation discrimination means for dis criminating between each of the detected modulations and a predetermined modula tion and for generating difference signals indicative of the difference between the detected modulations and the corres ponding predetermined modulations.

2. A transmitter, for remote control apparatus of the aforesaid type, comprising a. radiation means for generating two non collinear, non-parallel strips of radiation and for forming images of these strips at infinity, b. rotation means for rotating the images of the strips of radiation in a circular path so that during their motion along the path the images are continuously moved to positions in which the image of each strip lies parallel to all of its previous positions, c. modulation means for modulating the radiation, d. modulation sweeping means for sweeping the modulation of the radiation through a predetermined range in the period taken to complete one rotation of the images by the rotation means.

3. Remote control apparatus as claimed in claim 1 or a transmitter as claimed in claim 2 in which the strips of radiation are arranged to be mutually orthogonal in a substantially L-shape configuration.

4. Remote control apparatus as claimed in claim 1 or 3, or a transmitter as claimed in claim 2 or 3 in which the strips of radiation are provided by infra-red sources of radiation.

5. Remote control apparatus or a transmitter as claimed in claim 4 in which the sources are gallium aluminium arsenide lasers.

6. Remote control apparatus as claimed in any one of claims 1, 3, 4 and 5 or a transmitter as claimed in any one of claims 2, 3, 4 and

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

Claims

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

However if the displacements x and y are small compared with 1 equations (5) and (6) can be written: ay Fx=l + (7) I bx Fy=f2+ (8) I The frequency discriminator 12 detects the deviation of the detected frequencies Fx and Fy from the centre frequencies fl and f2 respectively and hence determines the displacements x and y. The constants a and b, and the radius of the relative path 1 of the detector are known. However l varies with the distance between the transmitter and receiver and consequently the sensitivity of the apparatus decreases with range. This may be compensated for, if required, in several ways.Firstly 1 may be varied by the use of a Risley prism in place of the single prism 6. A Risley prism is a combination of two thin prisms of equal power which can be rotated in opposite directions in their own plane and is equivalent to a single prism of variable power. Risley prisms are described and illustrated on pages 23 and 24 of the third edition of Fundamentals of Optics by Jenkins and White and published by the McGraw-Hill Book Co Inc.

Secondly a and b may be varied at the transmitter by varying the range of the frequency sweep performed by the frequency sweep unit 5. Thirdly the signals produced by the frequency discriminator 12 may be amplified by circuiuy whose gain varies with the distance between the transmitter and receiver.

By way of example only the parameters of the embodiment shown in Figure 1 were: Wavelength of radiation 850 nanometres Modulation triangular pulses of 100 nano-seconds width Carrier frequency f1 = 30 KHz; f,=40 KHz Modulation frequency range t 2 KHz Frequency of rotation of images 25 Hz Semi cone angle of cone of rotation 10 Milliradians Range of control up to 5 Km WHAT I CLAIM IS: 1.Remote control apparatus of the afore said type including a transmitter comprising a. radiation means for generating two non collinear, non-parallel strips of radiation and for forming images of these strips at infinity, b. rotation means for rotating the images of the strips of radiation in a circular path so that during their motion along the path the images are continuously moved to positions in which the image of each strip lies parallel to all of its previous positions, c. modulation means for modulating the radiation, d. modulation sweeping means for sweeping the modulation of the radiation through a predetermined range in the period taken to complete one rotation of the images by the rotation means, and a receiver comprising a. a detector for detecting the modulation of the radiation present in each image as it passes the detector, b. modulation discrimination means for dis criminating between each of the detected modulations and a predetermined modula tion and for generating difference signals indicative of the difference between the detected modulations and the corres ponding predetermined modulations.
2. A transmitter, for remote control apparatus of the aforesaid type, comprising a. radiation means for generating two non collinear, non-parallel strips of radiation and for forming images of these strips at infinity, b. rotation means for rotating the images of the strips of radiation in a circular path so that during their motion along the path the images are continuously moved to positions in which the image of each strip lies parallel to all of its previous positions, c. modulation means for modulating the radiation, d. modulation sweeping means for sweeping the modulation of the radiation through a predetermined range in the period taken to complete one rotation of the images by the rotation means.
3. Remote control apparatus as claimed in claim 1 or a transmitter as claimed in claim 2 in which the strips of radiation are arranged to be mutually orthogonal in a substantially L-shape configuration.
4. Remote control apparatus as claimed in claim 1 or 3, or a transmitter as claimed in claim 2 or 3 in which the strips of radiation are provided by infra-red sources of radiation.
5. Remote control apparatus or a transmitter as claimed in claim 4 in which the sources are gallium aluminium arsenide lasers.
6. Remote control apparatus as claimed in any one of claims 1, 3, 4 and 5 or a transmitter as claimed in any one of claims 2, 3, 4 and

5 in which the modulation means is for modulating the amplitude of the radiation.
7. Remote control apparatus or a transmitter as claimed in claim 6 in which the modulation sweeping means is for sweeping the frequency of the amplitude modulation of the radiation.
8. Remote control apparatus as claimed in any one of claims 1 and claims 3 to 7 or a transmitter as claimed in any one of claims 2 to 7 in which the rotation means includes a rotatably mounted wedge shaped prism positioned so that when, in use, the prism is rotated the images are rotated as aforesaid.
9. Remote control apparatus or a transmitter as claimed in claim 8 in which the prism is a Risley prism.
10. Remote control apparatus as claimed in any one of claims 1 and 3 to 8 in which there is provided means for controlling the range through which the modulation is swept by the modulation sweep means so that, m use, the variation in the sensitivity of the apparatus with the distance between the transmitter and its co-operating receiver is controlled in a predetermined manner.
11. Remote control apparatus as claimed in any one of claims 1 and 3 to 8 in which the receiver is provided with means for amplifying the difference signals so that, in use, the variation in sensitivity of the apparatus with the distance between the receiver and a cooperating transmitter is controlled in a predetermined manner.
12. Remote control apparatus or a transmitter substantially as hereinbefore described with reference to the drawings filed with the provisional specification.