WO1995019577A1

WO1995019577A1 - Monitoring articles' positions

Info

Publication number: WO1995019577A1
Application number: PCT/GB1995/000089
Authority: WO
Inventors: Roger Mark Anthony Gilbert; Jonathan Weinreich
Original assignee: Mikto Limited
Priority date: 1994-01-18
Filing date: 1995-01-18
Publication date: 1995-07-20
Also published as: GB9400873D0; AU1422395A

Abstract

There is described a method and means for monitoring the position of an article (10) in space (that is to say the orientation of the article, its distance from a datum location and its angular movement away from an axis extending from the datum location). A number of photo-diodes (16) sensitive to infrared radiation are placed on surfaces of a cube (14) carried by the article (e.g. a headset in a virtual reality system) and an infrared radiation sensor (18) is placed at the datum location. Means in the article receive the outputs of the photo-diodes and provide in response to the level of illumination of each an output (22) indicative of the position in space of the article. To account for translational movement of the article away from the axis (Z) joining the article (10) and the datum location (18) the parts so far described may be augmented by an infrared sender (26) on the article illuminating a plurality of photo-diodes (30) located at a position spaced from the article (e.g. the datum location). A plurality of locations spaced from the article may be provided allowing a wearer of the headset freedom of movement. The outputs of the senders are modulated - demodulators (20) being provided in the means receiving the output signals of the photo-diodes. The outputs of the senders may also be polarised and polarising filters be provided in each of the photo-diodes. The effective modulation and polarisation applied to the outputs of the senders preferably differs.

Description

MONITORING ARTICLES POSITIONS

DESCRIPTION

TECHNICAL FIELD

The present invention relates to methods and apparatus for monitoring the position in space of articles relative and is more specifically, but not exclusively, concerned with monitoring the position in space of a headset in a virtual reality system.

Within this specification and any claims appended hereto the term "position in space of an article" should be taken to encompass the orientation of the article and the distance of the article from a datum location and/or the angular displacement of the article from a reference axis extending from the datum location. BACKGROUND ART In manufacturing processes and other branches of human endeavour, there is often need to monitor the position of an article, for example as it travels along a processing line. Many different ways of monitoring the positions of articles have been proposed including mounting on the article a readable tag (for example a bar code or radio tag) or monitoring its position by means of reflected or refracted radiation (for example laser light) . The proposals known to us in this field are all relatively costly to implement and difficult to maintain at optimum peak performance.

Again, in the field of virtual reality systems, in which a wearer of a headset is presented with a visual image of an area through which he may move by moving physically, there is need to monitor precisely the position of the headset and so of the wearer's head relative to one (or more) datum locations.

The proposals made to achieve his in the field of virtual reality systems known to us are again costly and difficult to maintain at an optimum performance level.

It is an object of the present invention to provide both method and means for monitoring the position in space, as defined above, of an article which alleviates and/or overcomes the disadvantages of the monitoring systems presently know to us. DISCLOSURE OF THE INVENTION In a first aspect the present invention provides a method of monitoring the position in space, as defined above, of an article which comprises mounting on the article a plurality of sensors operable in response to a particular form of radiation to provide output signals indicative of the level of that radiation falling thereon, mounting at a datum location a sender emitting said particular form of radiation and providing means for monitoring the output signals of said sensors which monitoring means is operable in response to those output signals to generate an output indicative of the position in space of the article.

Desirably, the method provides that at least two sensors are mounted on the article in planes which intersect.

Preferably, the method provides that at least three sensors are mounted on the article in planes which orthogonally intersect. The method may advantageously provide that there are five sensors provided on the article a first of which is placed in a first plane, two further of which are placed in planes lying parallel one to the other and intersecting orthogonally the first plane and the last two of which are placed in two planes lying parallel to one another and intersecting orthogonally both the first and the second planes. In a second aspect the present invention provides means for monitoring the position in space, as hereinbefore defined, of an article which means comprises a plurality of sensors mounted on the article and operable in response to a particular form of radiation to provide output signals indicative of the level of that radiation falling thereon, sender means mounted at a datum location for emitting said particular form of radiation and means receiving the output signals of said sensors and generating in response thereto an output indicative of the position in space of the article.

Desirably, there are provided at least two sensors mounted on the article, which sensors are mounted in planes which intersect. With advantage there may be at least three sensors mounted on the article, which sensors are mounted in planes which intersect.

Desirably, the planes intersect orthogonally. With particular advantage there are five sensors on the article, a first of which lies in a first plane, a second pair of which lie in respective parallel planes orthogonally intersecting the first plane and the last pair of which lie in respective parallel planes orthogonally intersecting of the first and the second planes. Desirably, each said sensor comprises a photo- diode sensitive to incident infra red radiation and operable to provide an output in response thereto. Desirably, said means at the datum location comprises an emitter or sender of modulated infra red radiation.

The infra red radiation emitted by the sender may be polarised and the sensors may have polarised filters associated therewith.

It will be appreciated that in such an arrangement the output of the sensors will vary depending upon the position of the article relative to the sender at the datum location, and in particular will allow the orientation of the article relative to axes extending orthogonally of the axis running from the article to the datum location to be indicated.

With particular advantage the means may further comprise a plurality of further sensors operable in response to a particular form of radiation to provide output signals indicative of the level of that radiation falling thereon, which devices are mounted at a location spaced from the article, further sender means mounted on the article for emitting said particular form of radiation and means receiving the output signals of said further sensors and operable in response thereto to generate an output indicative of the position in space, of the article relative to said location spaced from the article. Desirably, the location spaced from the article is the datum location.

At least two further sensors may be provided at the datum location in planes which intersect.

Desirably, at least three further sensors are provided at the datum location in planes which intersect.

With particular advantage five further sensors are provided at the datum location a first lying in a first plane, a first pair lying in respective second parallel planes orthogonally intersecting the first plane and a further pair lying in parallel planes orthogonally intersecting both the first and the second planes. The said further sensors preferably comprise photo-diodes sensitive to infra red radiation emitted by the further sender means.

The infra red radiation emitted by the sender is preferably modulated. If the further sender emits modulated infra red radiation then it is desirable the modulation provided by the further sender differs from that provided by the first mentioned sender.

If desired the radiation emitted by the sender means may be polarised and the sensors be associated with polarised filters.

Furthermore it is desirable (if the further sender emits polarised infra red radiation) that the angle of polarisation of its radiation be different to that of the of the infra red radiation emitted by the first mentioned sender.

A further aspect of the invention provides a system for tracking the position in space, as hereinbefore defined, of a virtual reality headset comprising a generally cuboid structure mounted on the headset the free surfaces of which each have mounted thereon a sensor operable in response to a particular radiation to provide an output signal indicative of the level of that radiation falling thereon , the headset further comprising means for receiving the output signals of said sensors and providing in response thereto an output indicative of the position in space of the headset, and sender means at a datum location for emitting the particular form of radiation.

The system for tracking the position in space of the virtual reality headset may further comprise a plurality of further sensor operable in response to a particular form of radiation to provide output signals, which sensors are mounted at a location spaced from the headset, further sender means mounted on the headset for emitting said particular form of radiation and means receiving the output signals of said sensors and operable in response thereto to generate an output indicative of the position.

With particular advantage such a system may comprise a number of pluralities of further sensors each plurality being mounted at a different location spaced from the article, one of said locations being said datum location.

The above and other aspects, features and advantages of the present invention will become apparent from the following description of embodiments thereof now made with reference to the accompanying drawings, in which:- BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic side view of part of a virtual reality system incorporating monitoring means embodying the present invention,

Figure 2 illustrates parts of the system of Figure 1 in more detail,

Figure 3 schematically illustrates operation of the system shown in Figures 1 and 2,

Figure 4 schematically illustrates means provided in the system of the Figures 1 and 2 for receiving the output signals of sensors in the system of Figure 1,

Figure 5 graphically illustrates the outputs of three of said sensors and the output of the means receiving the output signals of those sensors, and

Figure 6 schematically illustrates a further embodiment of the present invention.

MODES OF CARRYING OUT THE INVENTION Figure 1 schematically shows a virtual reality headset 10 on the head of a user. Headset 10 carries on its front surface 12 a cuboid 14 the five free faces of which orthogonally (or nearly so) intersect.

Each of the faces carries a photo-diode 16 sensitive to infra red radiation. Spaced from the headset 10 along an axis Z is an emitter or sender 18 mounted at a fixed, datum, location.

Figure 2 illustrates in more detail the headset showing the cuboid 14 on its front surface 12. The face of cuboid 12 spaced from the front surface 12 of the headset carries a photo-diode 16F. The two faces of the cuboid lying normally of the X axis in the Figure carry photo-diodes 16R and 16L respectively, and the two faces lying normally of the Y axis shown in the Figure carry photo-diodes 16A and 16B respectively.

Each of the photo-diodes 16 is sensitive to a particular frequency of infra red radiation falling thereon (as emitted by sender 18) and generates an output signal proportional to the level of radiation falling on it. Thus in the position shown in full outline in

Figure 3 sensor 16F will generate an output whilst the other four sensors 16R, 16L, 16A and 16B are quiescent and generate no output signal as they have no infra red radiation falling on them. Should the wearer of the headset turn his head (in the plane defined by the X and Z axes and shown in dotted outline in the Figure) the incident infra red radiation on the sensor 16F will reduce whilst the incident radiation on the sensors 16 will increase.

Figure 4 schematically illustrates the circuit of the means receiving the output signals of three of the sensors, 16F, 16R and 16L which is provided within the headset. The outputs of the three sensors 16 are fed to respective demodulators 20R, 20F and 20L. After demodulation each of the signals is passed to an inverter 22R, 22F and 22L to generate a DC signal output. The demodulated output signals are then fed to operator device 24 (the output from the sensor 16R being fed as a negative signal to the device whilst the output from sensor 16F and 16L are fed as positive signals) .

The output of device 24, COMP, is defined by the equality:-

COMP = (22L' - 22R')/(22F' + j (22L' - 22R')j)

Figure 5 illustrates graphically the output signals of each of the invertors 22 showing at 22R' how the output of the sensor 16R varies from a maximum at FR (when the headset is oriented such that the sensor 16R extends normally of the Z axis) through a range of values as the headset turns until the point where, shown at FC, no further irradiation falls upon the sensor 16R.

Curve 22F' shows that as the curve 22R' decreases (it is to be noted sinusoidally) the output of the sensor 16F increases sinusoidally until it reaches a maximum at FC, when the output from the sensor 16R has reduced to zero. Further rotation of the headset from this position results in the output of sensor 16F reducing whilst the output of sensor 16L increases until a maximum is reached, at FL, when the output of sensor 16F again reaches zero.

Because of the way in which the three outputs of the invertors 22 are operated upon in device 24 the resulting output signal, shown graphically at COMP in Figure 5, has the form of a substantially straight line rising from a negative level (at FR) to an equal and opposite level (at FL) and passing through a zero value when the sensor 16F is receiving its maximum level of irradiation.

In this way the means receiving the output signals of the sensors 16 determines the orientation of the headset about the Y axis (extending normally of the X - Z plane.

Similarly if the wearer of the headset should raise or drop his head (that is to say move his head in the

Y - Z plane) the output of the sensor 16F will reduce and the output of the sensor 16A (or 16B) increase.

The outputs of the sensors 16A, 16F and 16B are fed to a monitoring circuit in substance the same as that shown in Figure 4 which provides an output, similar to the curve COMP shown in Figure 4 and indicative of the degree of rotation of the headset about the X axis.

It will be appreciated that these two outputs indicative of the rotation of the headset (about the X and

Y axes) may be combined to give a relatively precise indication of the orientation of the headset. Whilst it is possible to implement the system without modulating the output of the sensor 18 - thereby relieving the necessity of demodulating the outputs of the

SUBSTITUTE SHEET RULE 26 sensors 16 - it is found desirable to effect this modulation and demodulation to reduce spurious effects which may be caused by ambient infra red radiation in the environment in which the virtual reality system is being used.

It will be appreciated that moving the headset along the Z axis (towards or away from the datum location) will increase (or decrease) the infra red radiation falling on the sensor 16F (or whichever other sensor(s) 16 is for the time being irradiated by the sender) and the location of the headset along the Z axis may thus be determined.

The determination of the distance (Z) of the headset from the sender location is proportional to the total intensity of radiation falling upon the sensors and one measure of this distance is provided by the equality:-

where 22F', 22R' and 22L' have the values assigned to them above and 22A' and 22B' are the outputs of invertors (not shown) respectively coupled to the sensors 16A and 16B in the way that invertors 22R and 22L are respectively coupled to the sensors 16R and 16L.

It will be seen that translational movement of the headset along the X and Y axes (without rotation about the Y or X axis) may give rise to spurious outputs - for example as the headset moves away from the Z axis the radiation incident on the photodiode 16F will decrease to an extent whilst one or more of the other photodiodes 16L, 16R, 16A or 16B will become more irradiated. In this way translational movement of the headset along the X or Y axis may be perceived by the system so far described to be rotation of the headset about the Y or X axis. To account for this embodiments of the present invention provide that the virtual reality headset 10 may carry as shown in Figure 6 an infra red radiating or emitting sender 26 and that a further cuboid 28 be located at a position spaced from the headset (for example at the datum location) .

Cuboid 28 carries on its five free faces photo- diodes 30A, 30F 30R, 30B and 30L coupled to circuitry similar to the circuitry receiving the outputs of the sensors 16 and providing similar outputs indicative of the posi .ion of the headset.

It will be appreciated - particularly from viewing schematic Figure 6 - that this arrangement effectively provides an indication of any translational movement of the headset along the X or Y axes - as shown in full line movement along the X axis will cause an output to be provided by both the photo-diodes 30F and 30L (or 30R) whilst, as shown in dotted outline, rotation of the headset about the Y axis will have no effect - sensor 30L will not be driven to provide an output. As with the arrangement of the sender 18 and photo-diodes 16, the further sender 26 is arranged to provide an modulated infra red output. Desirably, the modulation of the outputs of the senders 18 and 26 are different.

It will be appreciated that the possibility of spurious effects being engendered by ambient infra red radiation received by the sensors 16 and 30 may be further reduced if the radiation emitted by the senders 18 and 26 is polarised.

In such an arrangement polarised filters would be provided for the sensors 16 and 30. Advantageously the angle of polarisation for the radiation emitted by the senders 18 and 26 would be different (as would the filters used for the sensors 16 and 30) . For example the radiation emitted by the sender 18 may be vertically polarised whilst that emitted by the sender 26 be horizontally polarised.

It will be further appreciated that it is possible to have a plurality of cuboids 26 located within an area which can be traversed by a person wearing the headset - allowing significant freedom of movement of the wearer in space.

The reader skilled in this art will appreciated that there are many modification which may be made to the described arrangement without departing from the scope of the present invention. Forms of radiation other than infra red radiation may be used, for example ultra violet or, low level laser light, and sound. Although as described the planes carrying the photo-diodes on the cuboids 14 and 28 are mutually perpendicular, it will be appreciated that these planes may merely be nearly perpendicular if desired which arrangement could, it is believed, have beneficial advantages in certain circumstances.

INDUSTRIAL APPLICABILITY Whilst the above description has been specifically related to the use of a system embodying the present invention as applied to a virtual reality headset it will be appreciated that the system has application to many other forms of human endeavour in which it is desired to precisely and accurately monitor the position in space (as defined) of an object.

Claims

1. A method of monitoring the position in space as herein defined, of an article which comprises mounting on the article a plurality of sensors operable in response to a particular form of radiation to provide output signals indicative of the level of that radiation falling thereon, mounting at a datum location a sensor emitting said particular form of radiation and providing means for monitoring the output signals of said sensors which monitoring means is operable in response to those output signals to generate an output indicative of the position of the article.

2. A method as claimed in Claim 1, wherein at least two sensors are mounted on the article in planes which intersect.

3. A method as claimed in Claim 2, wherein at least three sensors are mounted on the article in planes which orthogonally intersect.

4. A method as claimed in any one of claims 1 to 3, wherein five sensors are mounted on the article a first of which is placed in a first plane, two further of which are placed in planes lying parallel one to the other and intersecting orthogonally the first plane and the last two of which are placed in two planes lying parallel to one another and intersecting orthogonally both the first and the second planes.

5. Means for monitoring the position in space, as herein defined, of an article which means comprises a plurality of sensors mounted on the article and operable in response to a particular form of radiation to provide output signals indicative of the level of that radiation falling thereon, sender means mounted at a datum location for emitting said particular form of radiation and means receiving the output signals of said sensors and generating in response thereto an output indicative of the position in space of the article.

6. Monitoring means as claimed in Claim 5, wherein there are provided at least two sensorΪ mounted on the article, which sensors are mounted in planes which intersect.

7. Monitoring means as claimed in Claim 5, wherein there are at least three sensors mounted on the article, which sensors are mounted in planes which intersect.

8. Monitoring means as claimed in Claim 6 or Claim 7, wherein said the planes intersect orthogonally.

9. Monitoring means as claimed in Claim 7, wherein there are five sensors mounted on the article a first of which lies in a first plane, a second pair of which lie in respective parallel planes orthogonally intersecting the first plane and the last pair of which lie in respective parallel planes orthogonally intersecting the first and the second planes.

SUBSTITUTE SHEET (RULE 26}

10. Monitoring means as claimed in any one of claims 5 to 9, wherein each said sensor comprises a photo¬ diode sensitive to incident infra red radiation and operable to provide an output in response thereto.

11. Monitoring means as claimed in any one of claims 5 to 10, wherein said sender at the datum location comprises an emitter of modulated infra red radiation.

12. Monitoring means as claimed in any one of claims 5 to 11, wherein the radiation emitted by the sender is polarised and the sensors are associated with polarised filters.

13. Monitoring means as claimed in any one of claims 5 to 12, which further comprises a plurality of further sensors operable in response to a particular form of radiation to provide output signals indicative of the level of radiation falling thereon, which sensors are mounted at a location spaced from the article, further sender means mounted on the article for emitting said particular form of radiation and means receiving the output signals of said further sensors and operable in response thereto to generate an output indicative of the position in space of the article relative to said location spaced from the article.

14. Monitoring means as claimed in Claim 13, wherein said further sensors are mounted at the datum location.

15. Monitoring means as claimed in Claim 12 or Claim 14, wherein at least two further sensors are provided at the datum location mounted in planes which intersect.

16. Monitoring means as claimed in Claim 14 or Claim 15, wherein at least three further sensors are provided at the datum location mounted in planes which intersect.

17. Monitoring means as claimed in any one of claims 14 to 16, wherein there are five further sensors at the datum location a first being mounted in a first plane, a first pair being mounted in respective parallel planes orthogonally intersecting the first plane and a further pair being mounted in the parallel planes orthogonally intersecting both the first and the second planes.

18. Monitoring means as claimed in Claim 17, wherein said further sensors comprise photo-diodes sensitive to infra red radiation emitted by the further sender means.

19. Monitoring means as claimed in Claim 18, wherein infra red radiation emitted by the further sender is modulated.

20. Monitoring means as claimed in Claim 19, wherein the modulation provided by the further sender differs from that provided by the first mentioned sender.

21. Monitoring means as claimed in any one of claims 18 to 20, wherein the infra red radiation emitted by the further sensor means is polarised and the further sensors have polarised filters associated! therewith.

22. Monitoring means as claimed in Claim 21, wherein the angles of polarisation of the radiation of the first mentioned and further sender means differ.

23 A system for tracking the position in space, as hereinbefore defined, of a virtual reality headset comprising a generally cuboid structure mounted on the headset the free surfaces of which each have mounted thereon a sensor operable in response to a particular form of radiation to provide an output signal indicative of the level of that radiation falling thereon, wherein the headset further comprises means for receiving the output signals of said sensors and providing in response thereto an output indicative of the position in space of the headset, means at a datum location for emitting the particular form of radiation.

24. A system as claimed in Claim 23, further comprising a plurality of further sensors operable in response to a particular form of radiation to provide output signals in response thereto which sensors are mounted at a location spaced from the headset, further sender means mounted on the headset for emitting said particular form of radiation and means receiving the output signals of said further sensors and operable in response thereto to generate an output indicative of the position in space of the article.

25. A system as claimed in Claim 24, further comprising a number of pluralities of further sensors each said plurality of sensors being mounted at a different location spaced from the article and one of said locations being said datum location.