GB2534846A - Head-mountable apparatus and systems - Google Patents

Abstract

A head mountable display (HMD) system in which images are generated for display to the user, comprises a detector 600 configured to detect one or more biometric attributes of a wearer of the HMD. A memory 710 is configured to store user data relating to two or more users of the HMD. A user identity detector 700 is configured to compare the detected biometric attributes with the user data stored in the memory so as to identify whether the HMD wearer is one of the two or more users. A controller 700, 720 is configured to control the generation of images for display, at least in part, according to the detection of the identity of the HMD wearer. The detectors 600 may include strap length detectors 610, inter-pupillary distance (IPD) detector 620 temperature detectors 630, heart rate detectors 640 and nose height detector 650.

Description

HEAD-MOUNTABLE APPARATUS AND SYSTEMS

BACKGROUND

Field of the Disclosure

This invention relates to head-mountable apparatus and systems.

Description of the Prior Art

The "background" description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as

prior art against the present invention.

A head-mountable display (HMD) is one example of a head-mountable apparatus. Audio headphones comprising a frame supporting one or more audio transducers are another example of a head-mountable apparatus. A head-mounted torch or light is a further example of a head-mountable apparatus. The following background discussions will relate mainly to HMDs, but the principles are also applicable to other types of head-mountable apparatus.

In an HMD, an image or video display device is provided which may be worn on the head or as part of a helmet. Either one eye or both eyes are provided with small electronic display devices.

Some HMDs allow a displayed image to be superimposed on a real-world view. This type of HMD can be referred to as an optical see-through HMD and generally requires the display devices to be positioned somewhere other than directly in front of the user's eyes. Some way of deflecting the displayed image so that the user may see it is then required. This might be through the use of a partially reflective mirror placed in front of the user's eyes so as to allow the user to see through the mirror but also to see a reflection of the output of the display devices. In another arrangement, disclosed in EP-A-1 731 943 and US-A-2010/0157433, a waveguide arrangement employing total internal reflection is used to convey a displayed image from a display device disposed to the side of the user's head so that the user may see the displayed image but still see a view of the real world through the waveguide. Once again, in either of these types of arrangement, a virtual image of the display is created (using known techniques) so that the user sees the virtual image at an appropriate size and distance to allow relaxed viewing. For example, even though the physical display device may be tiny (for example, 10 mm x 10 mm) and may be just a few millimetres from the user's eye, the virtual image may be arranged so as to be perceived by the user at a distance of (for example) 20 m from the user, having a perceived size of 5 m x 5m.

Other HMDs, however, allow the user only to see the displayed images, which is to say that they obscure the real world environment surrounding the user. This type of HMD can position the actual display devices in front of the user's eyes, in association with appropriate lenses or other optical components which place a virtual displayed image at a suitable distance for the user to focus in a relaxed manner -for example, at a similar virtual distance and perceived size as the optical see-through HMD described above. This type of device might be used for viewing movies or similar recorded content, or for viewing so-called virtual reality content representing a virtual space surrounding the user. It is of course however possible to display a real-world view on this type of HMD, for example by using a forward-facing camera to generate images for display on the display devices.

Although the original development of HMDs was perhaps driven by the military and professional applications of these devices, HMDs are becoming more popular for use by casual users in, for example, computer game or domestic computing applications.

The foregoing paragraphs have been provided by way of general introduction, and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

Various aspects and features of the present invention are defined in the appended claims and within the text of the accompanying description and include at least a head mountable apparatus such as a display and a method of operating a head-mountable apparatus as well as a computer program.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: Figure 1 schematically illustrates an HMD worn by a user; Figure 2 is a schematic plan view of an HMD; Figure 3 schematically illustrates the formation of a virtual image by an HMD; Figure 4 schematically illustrates another type of display for use in an HMD; Figure 5 schematically illustrates a pair of stereoscopic images; Figures 6 and 7 schematically illustrate a user wearing an HMD connected to a Sony® PlayStation 30 games console; Figure 8 schematically illustrates another example HMD; Figure 9 schematically illustrates a strap displacement detector; Figure 10 schematically illustrates an optical code; Figure 11 schematically illustrates a nose height detector; Figures 12 and 13 are schematic diagrams illustrating biometric analysis; and Figure 14 is a schematic flowchart illustrating a biometric analysis technique.

DESCRIPTION OF THE EMBODIMENTS

Referring now to Figure 1, a user 10 is wearing an HMD 20 (as an example of a generic head-mountable apparatus -other examples, where the technical context allows, including audio headphones or a head-mountable light source) on the user's head 30. The HMD comprises a frame 40, in this example formed of a rear strap and a top strap, and a display portion 50.

Note that the HMD of Figure 1 may comprise further features, to be described below in connection with other drawings, but which are not shown in Figure 1 for clarity of this initial explanation.

The HMD of Figure 1 completely (or at least substantially completely) obscures the user's view of the surrounding environment. All that the user can see is the pair of images displayed within the HMD.

The HMD has associated headphone audio transducers or earpieces 60 which fit into the user's left and right ears 70. The earpieces 60 replay an audio signal provided from an external source, which may be the same as the video signal source which provides the video signal for display to the user's eyes.

The combination of the fact that the user can see only what is displayed by the HMD and, subject to the limitations of the noise blocking or active cancellation properties of the earpieces and associated electronics, can hear only what is provided via the earpieces, mean that this HMD may be considered as a so-called "full immersion" HMD. Note however that in some embodiments the HMD is not a full immersion HMD, and may provide at least some facility for the user to see and/or hear the user's surroundings. This could be by providing some degree of transparency or partial transparency in the display arrangements, and/or by projecting a view of the outside (captured using a camera, for example a camera mounted on the HMD) via the HMD's displays, and/or by allowing the transmission of ambient sound past the earpieces and/or by providing a microphone to generate an input sound signal (for transmission to the earpieces) dependent upon the ambient sound.

A front-facing camera 122 may capture images to the front of the HMD, in use. A Bluetooth® antenna 124 may provide communication facilities or may simply be arranged as a directional antenna to allow a detection of the direction of a nearby Bluetooth transmitter.

In operation, a video signal is provided for display by the HMD. This could be provided by an external video signal source 80 such as a video games machine or data processing apparatus (such as a personal computer), in which case the signals could be transmitted to the HMD by a wired or a wireless connection 82. Examples of suitable wireless connections include Bluetooth® connections. Audio signals for the earpieces 60 can be carried by the same connection. Similarly, any control signals passed from the HMD to the video (audio) signal source may be carried by the same connection. Furthermore, a power supply 83 (including one or more batteries and/or being connectable to a mains power outlet) may be linked by a cable 84 to the HMD. Note that the power supply 83 and the video signal source 80 may be separate units or may be embodied as the same physical unit. There may be separate cables for power and video (and indeed for audio) signal supply, or these may be combined for carriage on a single cable (for example, using separate conductors, as in a USB cable, or in a similar way to a "power over Ethernet" arrangement in which data is carried as a balanced signal and power as direct current, over the same collection of physical wires). The video and/or audio signal may be carried by, for example, an optical fibre cable. In other embodiments, at least part of the functionality associated with generating image and/or audio signals for presentation to the user may be carried out by circuitry and/or processing forming part of the HMD itself. A power supply may be provided as part of the HMD itself.

Some embodiments of the invention are applicable to an HMD having at least one electrical and/or optical cable linking the HMD to another device, such as a power supply and/or a video (and/or audio) signal source. So, embodiments of the invention can include, for

example:

(a) an HMD having its own power supply (as part of the HMD arrangement) but a cabled connection to a video and/or audio signal source; (b) an HMD having a cabled connection to a power supply and to a video and/or audio signal source, embodied as a single physical cable or more than one physical cable; (c) an HMD having its own video and/or audio signal source (as part of the HMD arrangement) and a cabled connection to a power supply; or (d) an HMD having a wireless connection to a video and/or audio signal source and a cabled connection to a power supply.

If one or more cables are used, the physical position at which the cable 82 and/or 84 enters or joins the HMD is not particularly important from a technical point of view. Aesthetically, and to avoid the cable(s) brushing the user's face in operation, it would normally be the case that the cable(s) would enter or join the HMD at the side or back of the HMD (relative to the orientation of the user's head when worn in normal operation). Accordingly, the position of the cables 82, 84 relative to the HMD in Figure 1 should be treated merely as a schematic representation.

Accordingly, the arrangement of Figure 1 provides an example of a head-mountable display system comprising a frame to be mounted onto an observer's head, the frame defining one or two eye display positions which, in use, are positioned in front of a respective eye of the observer and a display element mounted with respect to each of the eye display positions, the display element providing a virtual image of a video display of a video signal from a video signal source to that eye of the observer.

Figure 1 shows just one example of an HMD. Other formats are possible: for example an HMD could use a frame more similar to that associated with conventional eyeglasses, namely a substantially horizontal leg extending back from the display portion to the top rear of the user's ear, possibly curling down behind the ear. In other (not full immersion) examples, the user's view of the external environment may not in fact be entirely obscured; the displayed images could be arranged so as to be superposed (from the user's point of view) over the external environment. An example of such an arrangement will be described below with reference to Figure 4.

In the example of Figure 1, a separate respective display is provided for each of the user's eyes. A schematic plan view of how this is achieved is provided as Figure 2, which illustrates the positions 100 of the user's eyes and the relative position 110 of the user's nose. The display portion 50, in schematic form, comprises an exterior shield 120 to mask ambient light from the user's eyes and an internal shield 130 which prevents one eye from seeing the display intended for the other eye. The combination of the user's face, the exterior shield 120 and the interior shield 130 form two compartments 140, one for each eye. In each of the compartments there is provided a display element 150 and one or more optical elements 160. Figure 2 also illustrates two eye tracking cameras 102, which are directed towards the user's eyes possibly via the optics 160, or possibly observing the user's eyes to the side of the optics 160. The eye tracking cameras 102 are arranged at known positions within the HMD so as to allow the current user's inter-pupillary distance (IPD) to be detected. The IPD measurement can be useful in various ways, for example in techniques for calibrating the displays 150 and/or optics 160, and/or in ways of handling and displaying stereoscopic images. These may or may not be provided for in embodiments of the present technology, but one aspect which is present in example embodiments is the use of the measured IPD in the detection and identification of a current user wearing the HMD. This technique will be discussed further below. The way in which the display element and the optical element(s) cooperate to provide a display to the user will be described with reference to Figure 3.

Referring to Figure 3, the display element 150 generates a displayed image which is (in this example) refracted by the optical elements 160 (shown schematically as a convex lens but which could include compound lenses or other elements) so as to generate a virtual image 170 which appears to the user to be larger than and significantly further away than the real image generated by the display element 150. As an example, the virtual image may have an apparent image size (image diagonal) of more than 1 m and may be disposed at a distance of more than 1 m from the user's eye (or from the frame of the HMD). In general terms, depending on the purpose of the HMD, it is desirable to have the virtual image disposed a significant distance from the user. For example, if the HMD is for viewing movies or the like, it is desirable that the user's eyes are relaxed during such viewing, which requires a distance (to the virtual image) of at least several metres. In Figure 3, solid lines (such as the line 180) are used to denote real optical rays, whereas broken lines (such as the line 190) are used to denote virtual rays.

An alternative arrangement is shown in Figure 4. This arrangement may be used where it is desired that the user's view of the external environment is not entirely obscured. However, it is also applicable to HMDs in which the user's external view is wholly obscured. In the arrangement of Figure 4, the display element 150 and optical elements 200 cooperate to provide an image which is projected onto a mirror 210, which deflects the image towards the user's eye position 220. The user perceives a virtual image to be located at a position 230 which is in front of the user and at a suitable distance from the user.

In the case of an HMD in which the user's view of the external surroundings is entirely obscured, the mirror 210 can be a substantially 100% reflective mirror. The arrangement of Figure 4 then has the advantage that the display element and optical elements can be located closer to the centre of gravity of the user's head and to the side of the user's eyes, which can produce a less bulky HMD for the user to wear. Alternatively, if the HMD is designed not to completely obscure the user's view of the external environment, the mirror 210 can be made partially reflective so that the user sees the external environment, through the mirror 210, with the virtual image superposed over the real external environment.

In the case where separate respective displays are provided for each of the user's eyes, it is possible to display stereoscopic images. An example of a pair of stereoscopic images for display to the left and right eyes is shown in Figure 5. The images exhibit a lateral displacement relative to one another, with the displacement of image features depending upon the (real or simulated) lateral separation of the cameras by which the images were captured, the angular convergence of the cameras and the (real or simulated) distance of each image feature from the camera position.

Note that the lateral displacements in Figure 5 could in fact be the other way round, which is to say that the left eye image as drawn could in fact be the right eye image, and the right eye image as drawn could in fact be the left eye image. This is because some stereoscopic displays tend to shift objects to the right in the right eye image and to the left in the left eye image, so as to simulate the idea that the user is looking through a stereoscopic window onto the scene beyond. However, some HMDs use the arrangement shown in Figure 5 because this gives the impression to the user that the user is viewing the scene through a pair of binoculars. The choice between these two arrangements is at the discretion of the system designer.

In some situations, an HMD may be used simply to view movies and the like. In this case, there is no change required to the apparent viewpoint of the displayed images as the user turns the user's head, for example from side to side. In other uses, however, such as those associated with virtual reality (VR) or augmented reality (AR) systems, the user's viewpoint needs to track movements with respect to a real or virtual space in which the user is located. Figure 6 schematically illustrates a user wearing an HMD connected to a Sony® PlayStation 3® games console 300 as an example of a base device. The games console 300 is connected to a mains power supply 310 and (optionally) to a main display screen (not shown).

A cable, acting as the cables 82, 84 discussed above (and so acting as both power supply and signal cables), links the HMD 20 to the games console 300 and is, for example, plugged into a USB socket 320 on the console 300. Note that in the present embodiments, a single physical cable is provided which fulfils the functions of the cables 82, 84. In Figure 6, the user is also shown holding a hand-held controller 330 which may be, for example, a Sony® Move® controller which communicates wirelessly with the games console 300 to control (or to contribute to the control of) game operations relating to a currently executed game program. The video displays in the HMD 20 are arranged to display images generated by the games console 300, and the earpieces 60 in the HMD 20 are arranged to reproduce audio signals generated by the games console 300. Note that if a USB type cable is used, these signals will be in digital form when they reach the HMD 20, such that the HMD 20 comprises a digital to analogue converter (DAC) to convert at least the audio signals back into an analogue form for reproduction.

Images from the camera 122 mounted on the HMD 20 are passed back to the games console 300 via the cable 82, 84. Similarly, if motion or other sensors are provided at the HMD 20, signals from those sensors may be at least partially processed at the HMD 20 and/or may be at least partially processed at the games console 300. The use and processing of such signals will be described further below.

The USB connection from the games console 300 also provides power to the HMD 20, according to the USB standard.

Figure 7 schematically illustrates a similar arrangement in which the games console is connected (by a wired or wireless link) to a so-called "break out box" acting as a base or intermediate device 350, to which the HMD 20 is connected by a cabled link 82,84. The breakout box has various functions in this regard. One function is to provide a location, near to the user, for some user controls relating to the operation of the HMD, such as (for example) one or more of a power control, a brightness control, an input source selector, a volume control and the like. Another function is to provide a local power supply for the HMD (if one is needed according to the embodiment being discussed). Another function is to provide a local cable anchoring point. In this last function, it is not envisaged that the break-out box 350 is fixed to the ground or to a piece of furniture, but rather than having a very long trailing cable from the games console 300, the break-out box provides a locally weighted point so that the cable 82, 84 linking the HMD 20 to the break-out box will tend to move around the position of the break-out box. This can improve user safety and comfort by avoiding the use of very long trailing cables.

It will be appreciated that the localisation of processing in the various techniques described in this application can be varied without changing the overall effect, given that an HMD may form part of a set or cohort of interconnected devices (that is to say, interconnected for the purposes of data or signal transfer, but not necessarily connected by a physical cable). So, processing which is described as taking place "at" one device, such as at the HMD, could be devolved to another device such as the games console (base device) or the break-out box. Processing tasks can be shared amongst devices. Source signals, on which the processing is to take place, could be distributed to another device, or the processing results from the processing of those source signals could be sent to another device, as required. So any references to processing taking place at a particular device should be understood in this context. Similarly, where an interaction between two devices is basically symmetrical, for example where a camera or sensor on one device detects a signal or feature of the other device, it will be understood that unless the context prohibits this, the two devices could be interchanged without any loss of functionality.

As mentioned above, in some uses of the HMD, such as those associated with virtual reality (VR) or augmented reality (AR) systems, the user's viewpoint needs to track movements with respect to a real or virtual space in which the user is located.

This tracking is carried out by detecting motion of the HMD and varying the apparent viewpoint of the displayed images so that the apparent viewpoint tracks the motion.

Figure 8 schematically illustrates another example HMD 400. The HMD 400 is similar in many respects to that shown in Figure 1, in that it comprises a display portion 410 (similar to the display portion 50 of Figure 1) to be positioned over the HMD wearer's eyes in use, and a frame formed of a pair of head straps 420, 430 to support the HMD on the wearers head in use. The strap 430 may be rotated upwards in a direction indicated by an arrow 432 to provide support from an upper region of the user's head. In an extreme example, the strap 430 may be rotated as far as the upper strap shown in Figure 1, but in other examples the strap 430 may be rotated upwards in use, for example, to go around the widest part of the user's head. Features such as the forward facing camera 122 and the antenna 124 of Figure 1 may be included but are not shown in Figure 8 for clarity of the diagram.

The HMD 400 provides various arrangements for detecting biometric attributes of the HMD wearer. In this context, the term "biometric" has its usual meaning, namely relating to metrics (or measurements) of properties of the human being wearing the HMD. Various examples of the detection of biometric attributes of the HMD wearer will be discussed below.

Pulse detection In use, the display section 410 is worn over the eyes of the HMD wearer but -in order to provide an "immersive" experience in which ambient light is excluded -the display section 410 includes shielding formations 440 which, in use, wrap around the upper front part of the user's face so as to mask the eyes from seeing ambient light. To the left and right sides of the user's eyes, the shielding formations 440 wrap party around the user's temples. In the present examples, at positions inside the shielding formations corresponding to one or both of the wearer's temples, a pulse detector 450 is provided so that when the HMD is being warned, the pulse detector 450 is in contact with or insufficiently close proximity to the user's temple to detect the user's pulse.

It will of course be appreciated that the temple is just one example of a location with respect to the user's head at which a pulse can be detected. For example, a pulse detector could be provided on an earpiece (such as the earpiece 60, not shown in Figure 8 for clarity of the diagram), on a portion of the shielding formations in contact with the user's forehead, on a portion of a strap 420 in contact with the back of the user's neck, and so on.

It will also be appreciated that a simple pulse measurement or detection (for example as a number of beats per minute (bpm)) is not necessarily sufficient to distinguish, alone, between multiple users, although in some instances there may be one user with a characteristic high pulse rate and another with a characteristic very low pulse rate such that the pulse rate, detected at the time of donning the HMD, can distinguish between these users. In other examples, as with each of the biometric attributes discussed here, the detected pulse rate can be used as one of a set of biometric attributes used to distinguish between different users.

This arrangement provides an example of a pulse detector configured to detect the HMD wearer's pulse as a biometric attribute of the HMD wearer.

Although a pulse rate could be detected to a resolution of 1 bpm, even the same user is unlikely to have exactly the same pulse rate on two different occasions. Therefore, in example embodiments, the pulse rate detector 450 is configured to detect the pulse rate to a less precise resolution of, say, 10 bpm or 25 bpm.

Inter-pupillary distance (IPD) The IPD can be detected using the cameras 102 discussed in connection with Figure 2 above. In some examples, a single camera could be used such that either the single camera is arranged to review both eyes via a lens or beam splitting arrangement, or the analysis relies upon an expected degree of symmetry between the wearers eyes so that the distance from one pupil to the nose would be the same as the distance from the other people to the nose. In some examples, the user can be encouraged to look directly forward while this measurement is taking place (even if the user does not know that the measurement is taking place) by the display of some piece of interesting information at a directly forward viewing position on the displays 150. In the samples, two cameras (as in Figure 2) are used. In this arrangement, it is less critical that the user is looking directly forward at the time of the measurement, although similar techniques may be used to encourage the user to look directly forwards.

This arrangement provides an example of one or more cameras directed (in use) at the HMD wearer's eyes; and a detection arrangement associated with the cameras to detect the inter-pupillary distance of the HMD wearer's eyes as a biometric attribute of the HMD wearer.

A typical IPD is of the order of 70 mm. In some example embodiments, a measurement precision of ± 1 mm is used.

Face or head temperature The wearer's face and/or head temperature can be detected by one or more temperature sensors 460 disposed in or on the HMD 400, for example inside the shielding formations 440 or on the inside of one of the straps 420, 430. The one or more temperature sensors can be contact sensors such as temperature-sensitive components like thermistors, or non-contact sensors such as infrared detectors.

While it is the case that most normally healthy individuals have a similar core body temperature, the skin surface temperature can vary from person to person according to the person's recent activity level and also their individual circulatory system carrying blood to the skin surface. Accordingly, the detection of skin surface temperature can provide a contributory or distinguishing feature is between one HMD wearer and another. In other examples, for example to reduce the effect on the measurement of recent activity, a temperature difference between two points on the skin (such as the forehead and the back of the ear) can be detected as the skin surface temperature detection.

This arrangement provides an example of a temperature detector configured to detect the HMD wearer's skin temperature as a biometric attribute of the HMD wearer.

A typical skin surface temperature is in the mid 30s degrees centigrade. A measurement accuracy or resolution of, say, ± 0.5°C is appropriate.

Strap length Figure 9 schematically illustrates a strap displacement detector. The straps 420, 430 are adjustable to fit different head sizes of different respective users. The head size, as indicated by the adjustment which the user applies to the straps 420, 430, can provide one or more biometric attributes relating to that user.

Each of the straps 420, 430 is adjustable at a respective adjustment portion 422, 434. At an adjustment portion, in some examples, one part of the strap may be slid over the other part of the strap to adjust the total usable length of the strap. A plan view of such an arrangement is shown in Figure 9 in which at the adjustment portion 422, 434, strap portions 472, 474 may slide over one another and a retainer 470 is provided to hold the strap portions together while still allowing this sliding motion. End stops 476, 478 provide a maximum strap length, when the end stops 476, 478 are in contact, and optionally can provide a minimum strap length when the end stops contact buffer portions 480, 482 on one or both of the straps.

Various techniques may be used to detect movement of the strap portions relative to one another. An example is shown in Figure 9, in which an optical detector 490 detects characteristic markings on an inner surface 492 of one of the strap portions, and provides signals relating to the detected markings to a detector arrangement 494 which converts the detected markings into an indication of the strap movement or position.

Figure 10 schematically illustrates an optical code 500 which might be used in the example embodiments as the characteristic markings discussed above. Various types of characteristic markings may be used. It is not necessarily a requirement that any single marking indicates an absolute position of the strap portions relative to one another, because the detector 494 can detect motion relative to a previously detected position. In other examples, however, a set of characteristic markings may be provided (for example, as a non-repeating pseudorandom set of stripes or bars) such that the absolute position of the straps relative to another can be detected without the need for knowledge of any previously detected position.

This arrangement provides an example of one or more head straps having an adjustable strap length; and a detection arrangement associated with the one or more head straps to detect the length, in use, of the one or more head straps as a biometric attribute of the HMD wearer.

A typical head circumference is of the order of 50-60 cm. The variation in head circumference provided by the movable straps may be of the order of ± 6 cm. A detection resolution of the relative strap portion position of, say, 2 mm is therefore appropriate. This in turn can influence the size and nature of the characteristic markings such as the optical code 500.

Nose height Figure 11 schematically illustrates a nose height detector. Although the term "nose height" is used, the intention here is to detect a physical size attribute of an upper portion of the wearer's face, in a generally vertical direction (relative to the face orientation). The display portion (shown in a schematic form in Figure 11) is slightly linked to a front lower portion 510 of the strap 420 such that relative movement in the direction shown by an arrow 520 in Figure 8 is possible between the two items. In a similar manner to the position detection shown in Figure 9, characteristic markings are provided on a surface of one of the movable parts and an optical detector 530 coupled to detection circuitry 540 detects a relative position of the two items. Here, the allowable range of movement may be, for example, of the order of ± 1.5 cm, so a detection resolution of 1 mm is appropriate.

This arrangement provides an example of a display section having an adjustable position with respect to the one or more head straps; and a detection arrangement associated with the display section to detect the relative position of the display section and the one or more head straps as a biometric attribute of the HMD wearer.

Combination of detected biometric attributes The processing of the detected biometric attributes may be performed by processing resources provided at the HMD, by processing resources provided externally, for example at a games console or a break-out box, or by a combination of these. The choice of where to provide the processing of the detected biometric attributes is a system design decision depending upon available processing resources once other tasks are taken into account. If the processing is carried out primarily at the HMD, then less information needs to be passed by a communication link from the HMD to an external apparatus but the processing requirements and power requirements at the HMD are greater. On the other hand, if the processing is carried out primarily at an external apparatus, then the processing requirements and power requirements for the HMD reduced but there is a greater amount of data to be transferred from the HMD to the external apparatus. Two examples are shown in Figures 12 and 13, which are schematic diagrams illustrating biometric analysis. In Figure 12, the processing is carried out primarily at an external apparatus. In Figure 13, the processing is carried out primarily at the HMD.

In each of Figures 12 and 13, items shown to the left of a vertical broken line indicate items provided at the HMD, and items shown to the right of the vertical broken line indicate items provided at an external apparatus. A set of sensors 600 (providing an example of a detector configured to detect one or more biometric attributes of a wearer of the HMD) provides the biometric attributes detection discussed above. These comprise one or more strap length detectors 610, and IPD detector 620, one or more temperature detectors 630, one or more heart rate detectors 640 and eight nose height detector 650. It will be appreciated that these are just examples of the types of biometric attribute detectors which may be used. There will also be appreciated that different systems may employ different permutations of detectors, so that there is no specific requirement to use all of the detector shown in Figures 12 or 13.

An analyser 700 associated with a memory 710 in which user data relating to two or more users of the HMD may be stored, compares the detected biometric attributes with the user data stored in the memory so as to identify whether the HMD wearer is one of the two or more users. The analyser 700 also controls storage of data in the memory 710 (as discussed below) and passes information to a game engine 720 to control operations of the game engine 720 as discussed below. The analyser 700 and the game engine 720 cooperate to provide an example of a controller configured to control the generation of images for display (by the HMD), at least in part, according to the detection of the identity of the HMD wearer.

A difference between Figure 12 and Figure 13 is that in an arrangement in which the processing is carried out primarily by an external apparatus, an identification 660 of the particular HMD may be passed, with the detected attribute data, to the analyser 700 in the external apparatus.

The way in which the apparatus of Figures 12 or 13 operates will now be discussed with reference to Figure 14.

Figure 14 is a schematic flowchart illustrating a biometric analysis technique. the flowchart of Figure 14 partitions operations between the HMD and an external apparatus in a similar manner to that shown in Figure 13, which is to say that the analyser function 700 is provided at the HMD. It will of course however be appreciated that the analyser function (and the flowchart steps relating to the analyser function) may be provided instead at the external apparatus. As before, flowchart steps shown to the left of a vertical broken line indicate steps carried out at the HMD, and flowchart steps to the right of the vertical broken line indicate steps carried out at the external apparatus.

At a step 800, the user wearer puts on the HMD. At a step 810, the one or more detectors acquire sensor readings or detections indicating one or more detected biometric attributes of the HMD wearer.

At a step 820, the analyser 700 compares the detected biometric attributes or data derived from the detected biometric attributes with user data stored in the memory 710. If the detected biometric attributes match the user data stored in the memory 710 then control passes to a step 830 at which a particular user, of the users for whom user data is stored in the memory 710, is detected as the identity of the current HMD wearer. At a step 840, the analyser 700 instructs the game engine 720 to operate according to the detected user and at a step 850 the game engine provides gameplay or other operations appropriate to the detected identity of the user.

Returning to the step 820, if the detected biometric attributes do not match the user data stored in the memory 710 then control passes to a step 860 at which the currently detected biometric attributes, or data derived from them, are stored in the memory 710. At this stage, however, all that is known by the analyser 700 is that an unknown user is wearing the HMD. Accordingly, at a step 870 the analyser 700 instructs the game engine 720 to acquire the identity of the current user which the game engine 720 does at a step 880, for example by asking the current user to type his or her name into a data entry window. In response that information, the analyser 700 stores the identity of the current user in association with the stored biometric attributes at a step 890, and control also passes to the step 850 at which gameplay appropriate to that user is provided. The control path starting at the "no" outcome of the step 820 therefore provides an example of an arrangement in which, in an instance in which a user identity detector detects that the detected biometric attributes do not correspond to user data stored in the memory: the user identity detector is configured to store user data relating to the detected biometric attributes in the memory; and the controller is configured to request user identify data from the HMD wearer for storing in the memory in association with the stored user data.

It will be appreciated that in the context of multiple detections of different respective biometric attributes, a test which detects similarity between the detected biometric attributes and user data stored in the memory 710 can be organised in various ways. For example, a "match" metric can be derived indicating an overall quality of match between the two sets of data, for example by summing a set of normalised differences between the stored information and the detected attributes of the current HMD wearer, and applying a threshold test to the "match" metric to decide whether the current HMD wearer corresponds to one of the stored user identities. If two or more user identities meet the threshold test, the identity having the "match" metric indicative of a better match is selected.

The arrangements of Figure 14 provide an example of a method of operation of a head mountable display (HMD) system in which images are generated for display to the user, the method comprising: detecting one or more biometric attributes of a wearer of the HMD; storing user data relating to two or more users of the HMD; comparing the detected biometric attributes with the user data stored in the memory so as to identify whether the HMD wearer is one of the two or more users; and controlling the generation of images for display, at least in part, according to the detection of the identity of the HMD wearer.

It will be appreciated that the various techniques described above may be carried out using software, hardware, software programmable hardware or combinations of these. It will be appreciated that such software, and a providing medium by which such software is provided (such as a machine-readable non-transitory storage medium, for example a magnetic or optical disc or a non-volatile memory) are considered as embodiments of the present invention.

It will also be appreciated that numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practised otherwise than as specifically described herein.

Claims (11)

1. CLAIMS1. A head mountable display (HMD) system in which images are generated for display to the user, the HMD system comprising: a detector configured to detect one or more biometric attributes of a wearer of the HMD; a memory configured to store user data relating to two or more users of the HMD; a user identity detector configured to compare the detected biometric attributes with the user data stored in the memory so as to identify whether the HMD wearer is one of the two or more users; and a controller configured to control the generation of images for display, at least in part, according to the detection of the identity of the HMD wearer.
2. 2. A system according to claim 1, in which the HMD comprises: one or more cameras directed (in use) at the HMD wearer's eyes; and a detection arrangement associated with the cameras to detect the inter-pupillary distance of the HMD wearer's eyes as a biometric attribute of the HMD wearer.
3. 3. A system according to claim 1 or claim 2, in which the HMD comprises: one or more head straps having an adjustable strap length; and a detection arrangement associated with the one or more head straps to detect the length, in use, of the one or more head straps as a biometric attribute of the HMD wearer.
4. 4. A system according to claim 3, in which the HMD comprises: a display section having an adjustable position with respect to the one or more head straps; and a detection arrangement associated with the display section to detect the relative position of the display section and the one or more head straps as a biometric attribute of the HMD wearer.
5. 5. A system according to any one of the preceding claims, in which the HMD comprises: a pulse detector configured to detect the HMD wearer's pulse as a biometric attribute of the HMD wearer.
6. 6. A system according to any one of the preceding claims, in which the HMD comprises: a temperature detector configured to detect the HMD wearer's skin temperature as a biometric attribute of the HMD wearer.
7. 7. A system according to any one of the preceding claims, in which, in an instance in which a user identity detector detects that the detected biometric attributes do not correspond to user data stored in the memory: the user identity detector is configured to store user data relating to the detected biometric attributes in the memory; and the controller is configured to request user identify data from the HMD wearer for storing in the memory in association with the stored user data.
8. 8. A system according to any one of the preceding claims, in which the controller is part of 10 a computer games system.
9. 9. A method of operation of a head mountable display (HMD) system in which images are generated for display to the user, the method comprising: detecting one or more biometric attributes of a wearer of the HMD; storing user data relating to two or more users of the HMD; comparing the detected biometric attributes with the user data stored in the memory so as to identify whether the HMD wearer is one of the two or more users; and controlling the generation of images for display, at least in part, according to the detection of the identity of the HMD wearer.
10. 10. Computer software which, when executed by a computer, causes the computer to carry out the method of claim 9.
11. 11. A non-transitory machine-readable storage medium which stores computer software according to claim 10.