MECHANICAL AND DIGITAL ADJUSTMENT OF HEAD- MOUNTABLE DISPLAY INTERPUPILLARY DISTANCE
BACKGROUND
[0001] Extended reality (XR) technologies include virtual reality (VR), augmented reality (AR), and mixed reality (MR) technologies, and quite literally extend the reality that users experience. XR technologies may employ head- mountable displays (HMDs). An HMD is a display device that can be worn on the head. In VR technologies, the HMD wearer is immersed in an entirely virtual world, whereas in AR technologies, the HMD wearer’s direct or indirect view of the physical, real-world environment is augmented. In MR, or hybrid reality, technologies, the HMD wearer experiences the merging of real and virtual worlds.
BRIEF DESCRIPTION OF THE DRAWINGS [0002] FIGs. 1 and 2 are top view and front view diagrams, respectively, of an example head-mountable display (HMD) having eyepiece assemblies that are adjustably separable from one another.
[0003] FIG. 3 is a front view diagram of the example HMD of FIGs. 1 and 2 in which the eyepiece assemblies have been mechanically adjusted to have a greater physical distance between them.
[0004] FIG. 4 is a graph of an example of mechanical and digital adjustment of HMD interpupillary distance (IPD).
[0005] FIG. 5 is a graph of just the example digital IPD adjustment of
FIG. 4. [0006] FIG. 6 is a graph of another example of mechanical and digital adjustment of HMD IPD.
[0007] FIG. 7 is a graph of just the example digital IPD adjustment of FIG. 6. [0008] FIGs. 8, 9, and 10 are top view diagrams of an example of mechanical and digital HMD IPD adjustment in which the digital adjustment is realized by offsetting images displayed on display panels of an HMD.
[0009] FIGs. 11 and 12 are top view diagrams of another example of mechanical and digital HMD IPD adjustment in which the digital adjustment is realized by offsetting images displayed on display panels of an HMD.
[0010] FIGs. 13 and 14 are top view diagrams of a third example of mechanical and digital HMD IPD adjustment in which the digital adjustment is realized by offsetting images displayed on display panels of an HMD.
[0011] FIG. 15 is a flowchart of an example method for mechanically and digitally adjusting HMD IPD.
[0012] FIG. 16 is a block diagram of an example HMD.
[0013] FIG. 17 is a block diagram of an example computer-readable data storage medium.
DETAILED DESCRIPTION [0014] As noted in the background, a head-mountable display (HMD) can be employed as an extended reality (XR) technology to extend the reality experienced by the HMD’s wearer. An HMD can include a small display panel in front of each eye of the wearer, as well as various sensors to detect or sense the wearer and/or the wearer’s environment so that the images projected on the display panels convincingly immerse the wearer within an XR, be it a virtual reality (VR), augmented reality (AR), a mixed reality (MR), or another type of XR. An HMD may include a lens or multiple lenses positioned in the optical path between each display panel and the corresponding eye of the user.
[0015] For the user of an HMD to receive an optimal experience, the HMD has to be properly fitted or worn by the user. From a visual perspective, the HMD may provide a maximal (or more generally a specified) stereoscopic optical field of view when the centers of the images displayed on the display panels of the HMD are aligned with pupils of the HMD wearer’s eyes - that is, when the interpupillary distance (IPD) of the wearer matches the IPD of the HMD itself.
The IPD of the HMD may be considered as the distance between the centers of the images displayed on the display panels of the HMD, as viewable through lenses positioned between the wearer’s eyes and the panels. [0016] Because different people have differently sized heads and faces, different sizes of noses, and different IPDs, mass-produced HMDs and HMDs that are otherwise not manufactured for particular wearers are often IPD adjustable. An HMD may include a pair of eyepiece assemblies that each include an eyetube in which a display panel and a lens or multiple lens are disposed. The eyepiece assemblies may be adjustably separable from one another to permit mechanical adjustment of the HMD’s IPD. Mechanical IPD adjustment in this respect can mean that the actual physical distance between the panels is adjusted to match the IPD of the wearer of the HMD. [0017] The degree to which IPD can be mechanically adjusted may be limited. For instance, the maximum physical distance at which the eyepiece assemblies can be separated from one another may be limited by the overall size of the HMD. The minimum physical distance, or more generally a second physical distance less than the first physical distance, at which the assemblies can be separated may be limited by how closely they can be positioned to one another within the HMD, as well as by the geometry of the wearer’s facial features. Mechanical IPD adjustment may thus not permit users having relatively large or relatively small IPDs from optimally using the HMD, because the HMD’s IPD cannot be adjusted to match such a user’s IPD.
[0018] The IPD of an HMD may instead be digitally adjusted to match the IPD of the wearer. For instance, to decrease IPD, the images displayed on the display panels may be shifted towards one another. By comparison, to increase IPD, the images displayed on the panels may be shifted away from one another. Digital IPD adjustment in this respect can mean that the distance between the centers of the images displayed on the panels is adjusted to match the IPD of the wearer of the HMD. Digital IPD adjustment permits the IPD of the HMD to be adjusted without having to change the actual physical distance between the display panels. [0019] A difficulty with digital IPD adjustment is that the lenses of the
HMD’s eyepiece assemblies focusing the wearer’s eyes on the display panels typically have regions at which the lens provides optimal optical quality, such as artifact-free sharpness greater than a specified threshold. If the image displayed on a display panel of an eyepiece assembly is shifted too much inwards or outwards, the user may view the displayed image through a portion of the lens outside this region. Digital IPD adjustment may result in users with relatively large or small IPDs having a degraded experience. Furthermore, the range in which IPD can be digitally adjusted may have to be relatively limited so as not to unduly impact field of view.
[0020] Techniques described herein provide for both mechanical and digital adjustment of HMD IPD. The HMD includes a pair of eyepiece assemblies that are adjustably separable from one another to mechanically adjust their IPD, and thus the IPD of the HMD itself. The IPD is further digitally adjusted based on a detected distance separating the eyepiece assemblies. For instance, the HMD can include a sensor to detect the distance between the eyepiece assemblies, and hardware logic to further digitally adjust the IPD - which has already been mechanically adjusted - based on the detected distance between the assemblies. [0021] Because the HMD’s IPD is both mechanically and digitally adjustable, the IPD can be adjusted to a greater range than if it were just mechanically adjustable. As a result, the HMD can accommodate a wider range of different users, including those with relatively large or small IPDs.
Furthermore, because the HMD’s IPD is both mechanically and digitally adjustable, digital adjustment of IPD can just supplement mechanical IPD adjustment, instead of being the sole way by which IPD is adjusted. Digital IPD adjustment thus does not have to be as extreme, avoiding users from having to view images through portions of lenses outside regions of the lenses at which the lenses provide optimal quality.
[0022] FIG. 1 is a top view diagram of an example HMD 100, whereas FIGs. 2 and 3 are front view diagrams of the HMD 100. The HMD 100 includes left and right eyepiece assemblies 102L and 102R, which are collectively referred to as a pair of eyepiece assemblies 102, and can also include hardware logic 105 and a connection member 112. The left eyepiece assembly 102L includes an eyetube 108L within which a display panel 104L, a lens 106L, and an eyecup 110L are disposed. The right eyepiece assembly 102R likewise includes an eyetube 108R within which a display panel 104R, a lens 106R, and an eyecup 110R are disposed.
[0023] The left and right display panels 104L and 104R are collectively referred to as the display panels 104. Each display panel 104 may be a flat- panel display, such as a liquid-crystal display (LCD) panel, organic light-emitting diode (OLED) display panel, a panel on which an image is projected for display, or another type of display panel. The left and right lens 106L and 106R are collectively referred to as the lenses 106 and may each be one lens as shown in FIG. 1 or encompass multiple lenses. The left and right eyecups 110L and 110R are collectively referred to as the eyecups 110. [0024] The display panel 104 and the eyecup 110 of each eyepiece assembly 102 may be disposed at opposite ends of a respective eyetube 108, with the lens 106 of the eyepiece assembly 102 disposed within the optical path between the eyecup 110 and the display panel 104. A user can position the HMD 100 against his or her face, with the eyecups 110 surrounding the eyes, to view images displayed on the display panels 104, through the lenses 106. The user perceives corresponding different images displayed on the display panels 104 as a singular combined image. [0025] The display panels 104 and the lens 106 may be fixably (i.e. , immovably) positioned within their respective eyetubes 108. That is, each display panel 104 and each lens 106 may not be physically movable within their respective eyetube 108, such as by motors, and so on, apart from overall movement of the eyepiece assembly 102 itself that includes the eyetube 108. Stated another way, the lens 106 of each eyepiece assembly 102 is fixably (i.e., immovably) positioned relative to its respective display panel 104. Physical movement of an eyepiece assembly 102 results in corresponding movement of its display panel 104 and lens 106 in unison with one another, with the panel 104 and the lens 106 not further being independently movable within their respective eyetube 108.
[0026] The eyepiece assemblies 102 are adjustably separable from one another, such as by being adjustably coupled to each another via the connection member 112. The connection member 112 may be a coupling gear like a rack- and-pinion gear in which a cylindrical pinion translates rack movement of one assembly 102 to rack movement of the other assembly 102. The connection member 112 may be a different type of connection member as well.
[0027] Referring to FIGs. 2 and 3, the connection member 112 may include a lever 202 as specifically depicted in FIGs. 2 and 3. Manually moving the lever 202 to the left causes the eyepiece assemblies 102 to move towards one another as in FIG. 2, whereas manually moving the lever 202 to the right causes the assemblies 102 to move away from one another as in FIG. 3. The connection member 112 may instead be coupled to a motor to automate adjustment of the distance between the eyepiece assemblies 102.
[0028] The FIMD 100 has an IPD, which may be considered as the IPD of the eyepiece assemblies 102 of the FIMD 100. The IPD of the eyepiece assemblies 102 may in turn be considered as the distance between the centers of the images displayed on the display panels 104. The eyepiece assemblies 102 are adjustably separable from one another to mechanically adjust the IPD of the FIMD 100. That is, physically moving the eyepiece assemblies 102 closer together or farther apart correspondingly decreases or increases the distance between the centers of the images displayed on the display panels 104, and thus results in mechanical adjustment of FIMD IPD. [0029] The FIMD 100 can include a sensor 204. The sensor 204 detects the distance separating the eyepiece assemblies 102 as the assemblies 102 are moved closer together or farther apart. In the specific example of FIGs. 2 and 3, the sensor 204 may be a linear potentiometer having a rod 206. As the eyepiece assemblies 102 are drawn closer together, the rod 206 recedes into the body of the sensor 204 as in FIG. 2, and as the assemblies 102 are moved farther apart, the rod 206 extends from the body of the sensor 204 as in FIG. 3. As another example, the potentiometer may be akin to a slide switch, in which movement of a sliding member attached to one assembly 102 is captured by the geometry of the other assembly 102.
[0030] The hardware logic 105 of the HMD 100 may be implemented as a processor and a non-transitory computer-readable data storage medium storing program code. For example, the processor may be a general-purpose processor that executes program code stored on a memory. As another example, the processor and the computer-readable data storage medium may be implemented as an application-specific integrated circuit (ASIC) that has been encoded with the program code. [0031] The hardware logic 105 displays corresponding images on the display panels 104. The hardware logic 105 further digitally adjusts the IPD of the eyepieces assemblies 102 - and thus the IPD of the HMD 100 - based on the distance separating the assemblies 102 as detected by the sensor 204. For instance, the hardware logic 105 may offset the display of a corresponding image on each display panel 104 based on the detected distance between the eyepiece assemblies 102. The hardware logic 105 may offset the images displayed on the display panel 104 inwards with shorter separation distances and offset the images outwards with longer separation distances.
[0032] The IPD of the HMD 100 is thus digitally adjusted separate from (viz., independent of) being mechanically adjusted. Inwardly offsetting the images displayed on the display panels 104 decreases the distance between the centers of the images, and therefore decreases HMD IPD, regardless of the physical distance between the eyepiece assemblies 102. Similarly, outwardly offsetting the images displayed on the display panels 104 increases the distances between the centers of the images and increases HMD IPD regardless of the distance between the eyepiece assemblies 102.
[0033] The IPD of the HMD 100 is likewise mechanically adjustable separate from (viz., independent of) being digitally adjusted. Increasing the physical distance between the eyepiece assemblies 102 increases the distance between the centers of the images displayed on the display panels 104, and therefore increases HMD IPD, regardless of how much the images have been offset, if at all. Similarly, decreasing the physical distance between the eyepiece assemblies 102 decreases the distance between the centers of the images displayed on the display panels 104, and decreases HMD IPD regardless of how much the images have been offset, if at all.
[0034] FIG. 4 shows a graph 400 depicting example mechanical and digital HMD IPD adjustment as a function of inter-eyepiece assembly separation distance. The x-axis 402 denotes separation between the eyepiece assemblies of an HMD, from minimum separation 406 to maximum separation 407. The y-axis 404 denotes IPD of the HMD. The solid line 408 specifies the IPD that results from just mechanical adjustment, from a minimum IPD 410 to a maximum IPD 412. Mechanical IPD adjustment results from moving the eyepiece assemblies of the HMD closer together or farther apart.
[0035] The terms “maximum” and “minimum” (as well as “maximally” and “minimally”) may be considered relative and not absolute terms as used herein, in some implementations. That is, the terminology “maximum” may be construed as “large,” whereas the terminology “minimum” may be construed as “small” in some implementations. For example, the maximum separation 407 may be a separation greater than a first threshold and greater than the minimum separation 406. Similarly, the minimum separation 406 may be a separation less than a second threshold and less than the maximum separation 407. The second threshold in this instance may be the same or less than the first threshold. [0036] The dashed line 414 specifies the IPD that results from both mechanical adjustment and digital adjustment, from a minimum IPD 416 to a maximum IPD 418. Digital IPD adjustment can result from inwardly or outwardly offsetting the images displayed on the display panels of the eyepiece assemblies in correspondence with the detected physical distance separating the assemblies. At point 422 where the lines 408 and 414 cross, the images are centered left-to- right on their respective display panels, corresponding to zero offset.
[0037] The amount of digital IPD adjustment is the difference 420 between the lines 408 and 414. To the right of point 422, increased inter-eyepiece assembly separation increases the amount by which IPD is digitally adjusted. To the left of point 422, decreased inter-assembly separation similarly increases the (absolute) amount by which IPD is digitally adjusted. For instance, the images displayed on the display panels may be maximally outwardly offset at maximum separation 407, and maximally inwardly offset at minimum separation 406.
[0038] The graph 400 therefore shows how both digitally and mechanically adjusting IPD can result in a greater FIMD IPD range than if IPD were just mechanically adjusted. The minimum IPD 416 that combined digital and mechanical adjustment can realize is less than the minimum IPD 410 that just mechanical adjustment can realize. Similarly, the maximum IPD 418 that combined digital and mechanical adjustment can realize is greater than the maximum IPD 412 that just mechanical adjustment can realize. The range between the minimum IPD 416 and the maximum IPD 418 of combined digital and mechanical adjustment is greater than the range between the minimum IPD 410 and the maximum IPD 412 of just mechanical adjustment.
[0039] FIG. 5 shows a graph 500 depicting just the example digital HMD IPD adjustment of FIG. 4. The x-axis 402 denotes separation between the eyepiece assemblies of an HMD, from minimum separation 406 to maximum separation 407, as in FIG. 4. The y-axis 502 denotes how much IPD is adjusted. The bold solid line 504 specifies how much the IPD is digitally adjusted as a function of inter-eyepiece assembly separation distance. The IPD of the HMD is digitally adjusted in a linear manner in the example of FIG. 5 consistent with FIG. 4, but may instead be non-linear, such as in the case in which the line 504 is instead a curve.
[0040] At each inter-eyepiece assembly separation distance along the x-axis 402, the line 504 has a value on the y-axis 502 representing the difference between the values of the lines 414 and 408 on the y-axis 404 in FIG. 4 at the corresponding separation distance. At point 422, no digital IPD adjustment occurs. At minimum inter-eyepiece assembly separation 406, maximum negative digital IPD adjustment 506 occurs, and at maximum inter-assembly separation 407, maximum positive digital IPD adjustment 508 occurs. [0041] The maximum negative and positive digital IPD adjustments 506 and 508 can be equal to one another in absolute value. The maximum negative digital IPD adjustment 506 is the difference between the minimum IPD 416 realized by both mechanical and digital adjustment and the minimum IPD 410 realized by just mechanical adjustment in FIG. 4. The maximum positive digital IPD adjustment is the difference between the maximum IPD 418 realized by both mechanical and digital adjustment and the maximum IPD 412 realized by the just mechanical adjustment in FIG. 4.
[0042] FIG. 6 shows a graph 600 depicts another example of mechanical and digital FIMD IPD adjustment as a function of inter-eyepiece assembly separation distance. As in FIG. 4, the x-axis 402 denotes separation between the eyepiece assemblies of an FIMD, from minimum separation 406 to maximum separation 407, and the y-axis 404 denotes IPD of the FIMD. The solid line 408 again specifies the IPD that results from just mechanical adjustment, from a minimum IPD 410 to a maximum IPD 412.
[0043] The dashed line 604 specifies the IPD that results from both mechanical adjustment and digital adjustment when inter-eyepiece assembly separation is less than point 602, to a minimum IPD 416 at minimum separation 406. The dashed line 610 specifies the IPD that results from both mechanical adjustment and digital adjustment when inter-eyepiece assembly separation is greater than point 608, to a maximum IPD 418 at maximum separation 406. At inter-assembly separation distances between the points 602 and 608, no digital IPD adjustment occurs; FIMD IPD is just mechanically adjusted. [0044] The amount of digital IPD adjustment at the separation sub-range at or towards the minimum separation 406 (i.e. , less than point 602) is the difference 606 between the lines 604 and 408. The amount of digital IPD adjustment at the separation sub-range at or towards the maximum separation 407 (i.e., greater than point 608) is the difference 612 between the lines 610 and
408. To the right of point 608, increased eyepiece assembly separation increases the amount by which IPD is digitally adjusted, and to the left of point of point 602, decreased separation increases the (absolute) amount by which the IPD is digitally adjusted. [0045] The graph 600 therefore shows how HMD IPD may be digitally adjusted just as the eyepiece assemblies are maximally or minimally separated from one another. Between these two extremes, IPD is just mechanically adjusted in the example of FIG. 6. This is in comparison to the example of FIG. 4, in which IPD is both mechanically and digitally adjusted throughout the range of inter-eyepiece assembly separation. The example of FIG. 6 may maintain optimal HMD optical quality for the vast majority of users, while still permitting - via supplemental digital adjustment - the HMD’s IPD to match the IPDs of users that cannot be matched by mechanical adjustment alone.
[0046] FIG. 7 shows a graph 700 depicting just the example HMD IPD adjustment of FIG. 6. The x-axis 402 denotes separation between the eyepiece assemblies of an HMD, from minimum separation 406 to maximum separation 407, as in FIG. 6. The y-axis 502 denotes how much IPD is adjusted. The bold solid line 702 specifies how much the IPD is digitally adjusted as a function of inter-eyepiece assembly separation distance. The IPD of the HMD is digitally adjusted in a non-linear manner in the example of FIG. 7.
[0047] At each separation distance along the x-axis 402 between minimum separation 406 and the point 602, the line 702 has a value on the y-axis 502 representing the difference between the values of the lines 604 and 408 on the y-axis 404 in FIG. 6 at the corresponding separation distance. At each separation distance between the point 608 and maximum separation 407, the line 702 likewise has a value on the y-axis 502 representing the difference between the values of the lines 610 and 408 on the y-axis 404 in FIG. 6 at the corresponding separation distance. The line 702 has a value of zero between the points 602 and 608.
[0048] Therefore, the digital IPD adjustment of FIG. 7, consistent with FIG. 6, is non-linear in that the line 702 does not have the same slope between minimum separation 406 and maximum separation 407. However, the digital IPD adjustment between the point 602 and minimum separation 506 and the digital IPD adjustment between the point 608 and maximum separation 508 are by themselves each linear. In another implementation, though, either or both of the IPD adjustment between the point 602 and minimum separation 506 and the digital IPD adjustment between the point 608 and maximum separation 508 may be non-linear, such that line 702 is replaced by a curve in either or both of these portions.
[0049] At minimum separation 406, maximum negative digital IPD adjustment 506 occurs, and is the difference between the minimum IPD 416 realized by both mechanical and digital adjustment and the minimum IPD 410 realized by just mechanical adjustment in FIG. 4. At maximum separation 407, maximum positive digital IPD adjustment 508 occurs, and is the difference between the maximum IPD 418 realized by both mechanical and digital adjustment and the maximum IPD 412 realized by just mechanical adjustment in FIG. 4. At inter-eyepiece assembly separations between points 602 and 608, no digital IPD adjustment occurs.
[0050] FIGs. 8, 9, and 10 show an example of mechanical and digital FIMD IPD adjustment in which the digital adjustment is realized by symmetrically offsetting images displayed on the display panels 104. The images are displayed at image regions 802L and 802R of the display panels 104L and 104R, respectively. The image regions 802L and 802R are collectively referred to as the image regions 802. By comparison, no portions of the images are displayed at non-image regions 804L and 804R of the display panels 104L and 104R, respectively. The non-image regions 804L and 804R are collectively referred to as the non-image regions 804.
[0051] In FIG. 8, the display panels 104 are separated at a point between minimum and maximum separation at which no digital IPD adjustment occurs, such as in correspondence with point 422 of FIGs. 4 and 5. Therefore, the image regions 802 are centered within their respective display panels 104. The non image regions 804L to either side of the image region 802L within the display panel 104L are of equal size, as are the non-image regions 804R to either side of the image region 802R and may be close to if not zero in width in one implementation. The HMD IPD 806 is due just to mechanical adjustment and is the distance between the centers of the image regions 802, which in FIG. 8 is equal to the distance between the centers of the display panels 104 themselves. [0052] In FIG. 9, the display panels 104 are minimally separated, such as in correspondence with the minimal separation 406 of FIGs. 4 and 5. The image regions 802 have been maximally inwardly offset within their respective display panels 104 while still permitting their respective images to be displayed without cropping. The non-image regions 804 have therefore shifted to the outer sides of their respective image regions 802. The HMD IPD 806 without consideration of digital adjustment is the distance between the centers of the display panels 104. By comparison, the digitally adjusted IPD 806’ is the distance between the centers of the image regions 804 and is thus shorter than the non-digitally adjusted IPD 806 in FIG. 9. In another implementation ,the image regions 802 may be inwardly offset even further than that depicted in FIG. 9, albeit with corresponding cropping of portions of their respective images when displayed. [0053] In FIG. 10, the display panels 104 are maximally separated, such as in correspondence with the maximum separation 407 of FIGs. 4 and 5. The image regions 802 have been maximally outwardly offset within their respective display panels 104 while still permitting their respective images to be displayed without cropping. The non-image regions 804 have therefore shifted to the inner sides of their respective image regions 802. The digitally adjusted HMD IPD 806’, which is the distance between the centers of the image regions 804, is thus longer in FIG. 10 than the non-digitally adjusted IPD 806, which is the distance between the centers of the display panels 104. In another implementation, the image regions may be outwardly offset even further than that depicted in FIG. 10, albeit with corresponding cropping of portions of their respective images when displayed. [0054] The digital IPD adjustment of FIGs. 9 and 10 is symmetrical. That is, the image displayed on each display panel 104 is offset by the same (absolute) amount at a given separation distance between the display panels 104. Stated another way, the image region 802 of each display panel 104 is offset by the same amount at a given separation distance between the display panels 104. Flowever, in other implementations, digital IPD adjustment may be asymmetrical, with the images displayed on the display panels 104 offset by different (absolute) amounts at a given separation distance between the display panels 104.
[0055] FIGs. 11 and 12 show such an example of mechanical and digital FIMD IPD adjustment in which the digital adjustment is realized by asymmetrically offsetting images displayed on the display panels 104. In FIG. 11 , the display panels 104 are minimally separated, as in FIG. 9. By comparison, in FIG. 12, the display panels 104 are maximally separated, as in FIG. 10. In both figures, the image displayed on the display panel 104L is offset more than the image displayed on the display panel 104R at a given separation distance between the display panels 104.
[0056] In FIG. 11 specifically, the image region 802L has been maximally inwardly offset within the display panel 104L. Therefore, the non-image region 804L is shifted to the outer side of the image region 802L. By comparison, the image region 802R has been inwardly offset within the display panel 104R, but not maximally so. There is thus a non-image region 804R to either side of the image region 802R, with the non-image region 802R at the outer side being longer than the non-image region 802R at the inner side. The digitally adjusted HMD 806’ is shorter in FIG. 11 than the non-digitally adjusted HMD 806 but is not as short as it is in FIG. 9.
[0057] In FIG. 12 specifically, the image region 802L has been maximally outwardly offset within the display panel 104L. Therefore, the non-image region 804L is shifted to the inner side of the image region 802L. By comparison, the image region 802R has been outwardly offset within the display panel 104R, but not maximally so. There is thus a non-image region 804R to either side of the image region 802R, with the non-image region 802R at the inner side being longer than the non-image region 802R at the outer side. The digitally adjusted HMD 806’ is longer in FIG. 12 than the non-digitally adjusted HMD 806 but is not as long as it is in FIG. 10.
[0058] FIGs. 13 and 14 show an example of mechanical and digital HMD IPD adjustment in which the digital adjustment is realized by offsetting the image displayed on just one of the display panels 104, specifically the image displayed on the left panel 104L. By comparison, the image displayed on the right panel 104R is not offset. In FIG. 13, the display panels 104 are minimally separated, as in FIGs. 9 and 11. In FIG. 14, the display panels 104 are maximally separated, as in FIGs. 10 and 12. [0059] In FIG. 13 specifically, the image region 802L has been maximally inwardly offset within the display panel 104L. Therefore, the non-image region 804L is shifted to the outer side of the image region 802L. By comparison, the image region 802R has not been offset within the display panel 104R, and instead remains centered within the panel 104R as in FIG. 8. Therefore, the non image regions 804R to either side of the image region 802R are of equal size.
The digitally adjusted FIMD 806’ is shorter in FIG. 13 than the non-digitally adjusted FIMD 806 but is not as short as it is in FIG. 9.
[0060] In FIG 14 specifically, the image region 802L has been maximally outwardly offset within the display panel 104L. Therefore, the non-image region 804L is shifted to the inner side of the image region 802L. By comparison, the image region 802R has again not been offset within the display panel 104R, and instead remains centered within the panel 104R as in FIG. 8. As before, the non image regions 804R to either side of the image region 802R are of equal size. The digitally adjusted FIMD 806’ is longer in FIG. 14 than the non-digitally adjusted FIMD 806 but is not as long as it is in FIG. 10.
[0061] FIG. 15 shows an example method 1500 for mechanical and digital FIMD IPD adjustment. The method 1500 may be implemented as program code stored on a non-transitory computer-readable data storage medium and executable by a processor. The method 1500 may thus be implemented as or within the hardware logic 105 of FIGs. 1 , 2, and 3. Further, the processor may instead be part of a host computing device, such as a computer, to which the FIMD is communicatively connected. That is, the digital IPD adjustment may be performed by the HMD itself, or by the host computing device to which the HMD is communicatively connected.
[0062] The method 1500 includes mechanical adjustment of the HMD’s IPD (1502). For example, the wearer of the HMD may mechanically adjust the physical distance separating the eyepiece assemblies of the HMD, and thus the distance between the centers of the display panels within the assemblies. The wearer may manually adjust physical distance separating the eyepiece assemblies or may press a control that responsively causes a motor to adjust the physical distance between the assemblies. [0063] The method 1500 includes detecting the physical distance separating the eyepiece assemblies of the HMD (1504). For example, a sensor may detect the physical distance between the eyepiece assemblies, with the processor that is performing the method 1500 then receiving the detected distance. The method 1500 includes responsively digitally adjusting the IPD of the HMD based on the detected distance between the eyepiece assemblies (1056).
[0064] For instance, the method 1500 can include determining an offset factor of either or both eyepiece assemblies based on the detected distance between the assemblies (1508). The offset factor of an eyepiece assembly is the amount by which the image displayed on the display panel of the assembly is to be inwardly or outwardly offset or shifted, and can be a function of the detected inter-eyepiece assembly distance, such as in FIG. 5 or 7. The method 1500 can include then offsetting the image displayed within either or both eyepiece assemblies by the corresponding determined offset factor (1510).
[0065] The offset factors for the eyepiece assemblies may be different or the same. If the offset factors are different, then the images displayed on the display panels are asymmetrically offset, whereas if the offset factors are the same, then the images displayed on the panels are symmetrically offset. If just the image displayed on one eyepiece assembly is offset, then the offset factor is determined for just this assembly. The digital IPD adjustment may be linear, such as in FIG. 5, or non-linear. In the latter case, the digital IPD adjustment may occur just at sub-ranges of inter-eyepiece separation distance at the minimum and/or maximum separation distances, such as in FIG. 7.
[0066] FIG. 16 shows a block diagram of an example FIMD 100. The FIMD 100 includes a pair of eyepiece assemblies 102 adjustably separable from one another to mechanically adjust an IPD of the eyepiece assemblies and thus of the FIMD 100. The FIMD 100 includes a sensor 204 to detect the distance separating the eyepiece assemblies 102, and hardware logic 105 to digitally adjust the IPD of the eyepiece assemblies 102 based on the detected distance separating the eyepiece assemblies 102.
[0067] FIG. 17 shows an example computer-readable data storage medium 1700. The computer-readable data storage medium 1700 stores program code 1702 executable by a processor, such as the hardware logic of an FIMD or the processor of a host computing device to which the FIMD is communicatively connected, to perform processing. The processing includes detecting a distance separating a pair of eyepiece assemblies of the HMD, which have been adjustably separated from one another to mechanically adjust an IPD of the assemblies (1504). The processing includes digitally adjusting the IPD based on the detected distance separating the assemblies (1506). [0068] Techniques have been described herein for both mechanically and digitally adjusting the IPD of an HMD. As compared to just mechanically adjusting HMD IPD, additionally digitally adjusting IPD can realize a greater IPD range, so that the HMD IPD may be adjustable to match IPDs of a greater number of users. As compared to just digitally adjusting HMD IPD, combining digital IPD adjustment with mechanical IPD adjustment may provide maximum image quality. For instance, combined digital and mechanical IPD adjustment may permit even a user with a relatively large or small IPD to view the displayed images through regions of the lenses at which the lenses provide optimal quality.