Near-infrared (NIR) transparent organic light-emitting diode (OLED) display

Abstract

The micro OLED display (400) includes a substrate (420) having a coating (422) made of an IR-transparent material, such as zinc selenide or zinc sulfide, to allow a pupil tracking camera, which may include a photodiode, to be mounted directly behind the display. The coating is transparent to near-infrared (NIR) radiation but opaque to visible light.

Description

[Technical Field]

[0001] This application relates generally to near-infrared transmissive organic light-emitting diode (OLED) displays, such as head-mounted displays, for extended reality (XR) applications such as computer games. [Background technology]

[0002] As recognized herein, organic light-emitting diode (OLED) displays can be used in head-mounted displays (HMDs) or headsets to facilitate eye tracking of a wearer, for example, for the purpose of presenting augmented reality and / or virtual reality images on the display. As understood herein, for many XR applications, eye tracking of the wearer is required, and further, for optimal eye tracking, a camera is placed directly in front of the pupil. However, the present principles further recognize that eye-tracking cameras are not optimally placed. This is because, if located between the display substrate and the eye, a camera directly in front of the pupil will block the display, and, if located outside the display, an opaque coating on the display substrate that allows the display to appear black when pixels are inactive will block an image of the pupil from reaching the camera. Summary of the Invention

[0003] The microOLED display includes a substrate having a coating made of an IR-transparent material, such as zinc selenide or zinc sulfide, that allows a pupil-tracking camera, which may include a photodiode, to be mounted directly behind the display, i.e., the display is located between the pupil and the camera. The coating is transparent to near-infrared (NIR) radiation but opaque to visible light.

[0004] Thus, in one aspect, an assembly includes at least one organic light-emitting diode (OLED) display having an innermost surface and at least one substrate. A coating is on the substrate. The coating comprises an infrared (IR) transparent material that is transparent to at least near-infrared (NIR) radiation but opaque to visible light. At least one camera is configured to generate an image from IR light. The camera is positioned to receive light through the coating.

[0005] The coating may include zinc selenide and / or zinc sulfide.

[0006] In some embodiments, the OLED display includes a micro-OLED display.

[0007] In an exemplary embodiment, the at least one IR illumination lamp is configured to emit IR radiation toward the eyes of a wearer of the device.

[0008] In an exemplary embodiment, the assembly includes at least one processor configured with instructions to activate the camera or the lamp, or both the camera and the lamp, starting from the beginning of a null period between a first period and a second period for rendering a first and second frame of each of the requested images. The instructions may be executable to stop providing energy to the camera or the lamp, or both the camera and the lamp, at the end of the null period. Alternatively, the instructions may be executable to stop providing energy to the camera or the lamp, or both the camera and the lamp, at once, during a second period for rendering a second frame of the requested image.

[0009] In one embodiment, the camera is positioned on the outer surface of the substrate. In another embodiment, the camera is connected to an arm and directed to image the outer surface of the substrate. In some embodiments, the camera is an IR image sensor. In a non-limiting implementation, the IR image sensor is bonded directly to the back (outer surface) of the substrate opposite the innermost surface, and the substrate is used as a lens.

[0010] In another aspect, a method includes presenting frames of a requested image on at least one head-mounted display (HMD), the method also including generating at least one image of a pupil of a wearer of the HMD during a null period between at least a first frame and a second frame.

[0011] The method may include illuminating the pupil with infrared (IR) light during the null period. In an embodiment, the method includes generating an image of the pupil using the IR light after the IR light has passed through a layer of material that blocks visible light. The image can be used for eye tracking of the wearer.

[0012] The method can include energizing the camera only during the null period plus some but not all of the period for scanning the second frame, or the method can include energizing the camera only during the null period.

[0013] In another aspect, a head-mounted display (HMD) for generating at least one computer-simulated requested image based at least in part on tracking at least one pupil of a wearer of the HMD includes at least one organic light-emitting diode (OLED) display. The HMD also includes at least one pupil-tracking camera configured to generate images from infrared (IR) light. At least one substance is configured to pass IR light from the pupil to the camera for generation of the image by the camera and to block visible light from the camera and the OLED display, such that the at least one computer simulation engine configured to generate the requested image can do so at least in part based on the image from the camera.

[0014] The details of the present application, both as to its structure and operation, can be understood with reference to the accompanying drawings, in which like reference numerals refer to like parts. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram of an exemplary system in accordance with the present principles; [Figure 2] 1 illustrates a first embodiment of a head-mounted display (HMD) with a tracking camera. [Figure 3] 1 illustrates a second embodiment of an HMD with a tracking camera. [Figure 4] 1 illustrates an expanded view of various layers of an exemplary HMD. [Figure 5] 1 illustrates an IR light emitting diode (LED) in an exemplary configuration for illuminating the pupil. [Figure 6] 1 illustrates a first exemplary timing graph between the presentation of an active image, pause intervals between frames, and activation of a tracking camera and / or illumination LEDs. [Figure 7] 1 illustrates a schematic representation of a portion of a frame during presentation of an active image. [Figure 8] 8 illustrates a second exemplary timing graph consistent with FIG. 7 between the presentation of an active image, pause intervals between frames, and activation of a tracking camera and / or illumination LEDs. [Figure 9] Exemplary logic is illustrated in an exemplary flowchart format in accordance with the present principles. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present disclosure relates generally to computer ecosystems, including, but not limited to, aspects of consumer electronics (CE) device networks, such as computer gaming networks. Systems herein may include server and client components that may be connected via a network so that data may be exchanged between the client and server components. The client components may include one or more computing devices, including gaming consoles such as Sony PlayStation® or gaming consoles made by Microsoft, Nintendo, or other manufacturers; extended reality (XR) headsets, such as virtual reality (VR) headsets, augmented reality (AR) headsets; portable televisions (e.g., smart TVs, Internet-enabled TVs); portable computers, such as laptops and tablet computers; and other mobile devices, including smartphones and additional examples described below. These client devices may operate in a variety of operating environments. For example, some client computers may employ, for example, the Linux® operating system, a Microsoft operating system, or a Unix® operating system, or an Apple or Google operating system, or the Berkeley Software Distribution or Berkeley Standard Distribution (BSD) OS (including derivatives of BSD). These operating environments may be used to run one or more browsing programs, such as browsers created by Microsoft, Google, or Mozilla, or other browser programs that can access websites hosted by the Internet servers described below. Also, an operating environment according to present principles may be used to run one or more computer game programs.

[0017] Servers and / or gateways may be used, which may include one or more processors that execute instructions that configure the server to receive and transmit data over a network such as the Internet. Alternatively, clients and servers may be connected via a local intranet or a virtual private network. The server or controller may be instantiated by a game console such as a Sony PlayStation®, a personal computer, or the like.

[0018] Information may be exchanged between the client and the server over a network. For this purpose and for security, the server and / or client may include firewalls, load balancers, temporary storage, and proxies, as well as other network infrastructure for reliability and security. One or more servers may form an apparatus that implements a method for providing a secure community, such as an online social website or a gamer network, to network members.

[0019] The processor may be a single-chip or multi-chip processor capable of implementing logic through various wiring such as address lines, data and control lines, as well as registers and shift registers.

[0020] Components included in one embodiment may be used in other embodiments in any suitable combination. For example, any of the various components described herein and / or shown in the drawings may be combined with, interchanged with, or excluded from other embodiments.

[0021] "A system having at least one of A, B, and C" (and similarly "a system having at least one of A, B, or C" and "a system having at least one of A, B, and C") includes systems having A only, B only, C only, both A and B, both A and C, both B and C, and / or A, B, and C together.

[0022] 1 , an exemplary system 10 is shown, which may include one or more of the exemplary devices described above and further below in accordance with the present principles. A first exemplary device included in system 10 is an audio-video device (AVD) 12, such as a theater display system, which may be projector-based, or a consumer electronics (CE) device, such as an Internet-enabled TV with a TV tuner (equivalently, a set-top box controlling the TV). AVD 12 may alternatively be a computerized Internet-enabled (“smart”) phone, a tablet computer, a notebook computer, a head-mounted device (HMD) and / or headset, such as smart glasses or a VR headset, another wearable computerized device, a computerized Internet-enabled music player, computerized Internet-enabled headphones, a computerized Internet-enabled embedded device, such as an implantable skin device, or the like. Nevertheless, it should be understood that AVD 12 is configured to implement the present principles (e.g., communicate with other CE devices to implement the present principles, execute the logic described herein, and perform any other functions and / or operations described herein).

[0023] Thus, to realize these principles, AVD 12 can be established by some or all of the components shown. For example, AVD 12 can include one or more touch-enabled displays 14, which can be implemented by high-definition or ultra-high-definition "4K" or higher flat screens. Touch-enabled display(s) 14 can include, for example, a capacitive or resistive touch-sensing layer having a grid of electrodes for touch sensing consistent with the present principles.

[0024] The AVD 12 may also include one or more speakers 16 for outputting audio in accordance with the present principles and at least one additional input device 18, such as an audio receiver / microphone, for inputting audible commands to the AVD 12 to control it. The exemplary AVD 12 may also include one or more network interfaces 20 for communicating over at least one network 22, such as the Internet, a WAN, or a LAN, under the control of one or more processors 24. Thus, the interface 20 may be, but is not limited to, a Wi-Fi transceiver, which is an example of a wireless computer network interface, such as, but not limited to, a mesh network transceiver. It should be understood that the processor 24 controls the AVD 12 to implement the present principles, including other elements of the AVD 12 described herein, such as controlling the display 14 to present images thereon and receiving input from the display 14. It should further be noted that the network interface 20 may be a wired or wireless modem or router, or a wireless telephone transceiver, or other suitable interface, such as the Wi-Fi transceiver discussed above.

[0025] In addition to the above, AVD 12 may include one or more input and / or output ports 26, such as a High-Definition Multimedia Interface (HDMI®) port or a Universal Serial Bus (USB) port for physically connecting to another CE device, and / or a headphone port for connecting headphones to AVD 12 to present audio from AVD 12 to a user through the headphones. For example, input port 26 may be connected to a wired or wireless cable or satellite source 26a of audio-video content. Thus, source 26a may be a separate or integrated set-top box or satellite receiver. Alternatively, source 26a may be a game console or disc player containing content. When implemented as a game console, source 26a may include some or all of the components described below in connection with CE device 48.

[0026] AVD 12 may further include one or more computer memory / computer-readable storage media 28, such as non-transitory disk-based or solid-state storage, possibly embodied within the AVD chassis as a standalone device, or as a personal video recording device (PVR) or video disc player either internal or external to the AVD chassis for playing AV programs, or as removable memory media or a server as described below. In some embodiments, AVD 12 may also include a location or position receiver, such as, but not limited to, a cellular receiver, a GPS receiver, and / or an altimeter 30, configured to receive geographic location information from satellites or cellular towers and provide that information to processor 24 and / or to determine the altitude at which AVD 12 is disposed in conjunction with processor 24. Component 30 may also be implemented by an inertial measurement unit (IMU), which typically includes a combination of accelerometers, gyroscopes, and magnetometers for determining the location and orientation of AVD 12 in three dimensions or by event-based sensors, such as event detection sensors (EDS). An EDS consistent with the present disclosure provides an output indicative of a change in light intensity sensed by at least one pixel of the light-sensing array. For example, if the light sensed by the pixel is decreasing, the output of the EDS may be −1, and if it is increasing, the output of the EDS may be +1. No change in light intensity below a certain threshold may be indicated by an output binary signal of 0.

[0027] Continuing with the description of AVD 12, in some embodiments, AVD 12 may include one or more cameras 32, which may be a thermal imaging camera, a digital camera such as a webcam, an IR sensor, an event-based sensor, and / or a camera integrated into AVD 12 and controllable by processor 24 to collect pictures / images and / or video in accordance with present principles. Also included in AVD 12 may be a Bluetooth® transceiver 34 and other near-field communication (NFC) elements 36 for communication with other devices using Bluetooth® and / or near-field communication (NFC) technologies, respectively. An exemplary NFC element may be a radio frequency identification (RFID) element.

[0028] Continuing further, AVD 12 may include one or more auxiliary sensors 38 (e.g., pressure-sensitive sensors, motion sensors such as accelerometers, gyroscopes, cyclometers, or magnetic sensors, infrared (IR) sensors, optical sensors, speed and / or cadence sensors, event-based sensors, gesture sensors (e.g., for sensing gesture commands)) that provide input to processor 24. For example, one or more of the auxiliary sensors 38 may include one or more pressure sensors that form a layer of touch-enabled display 14 itself, and may be, without limitation, piezoelectric pressure sensors, capacitive pressure sensors, piezoresistive strain gauges, optical pressure sensors, electromagnetic pressure sensors, etc.

[0029] The AVD 12 may also include an OTA TV broadcast port 40 for receiving over-the-air TV broadcasts, which provides input to the processor 24. In addition to the above, it should be noted that the AVD 12 may also include an infrared (IR) transmitter and / or an IR receiver and / or an IR transceiver 42, such as an IR Data Association (IRDA) device. A battery (not shown) may be provided to power the AVD 12, and may also be a kinetic energy harvester that can convert kinetic energy into power to charge the battery and / or power the AVD 12. A graphics processing unit (GPU) 44 and a field programmable gate array 46 may also be included. One or more haptic / vibration generators 47 may be provided to generate haptic signals that can be sensed by a person holding or interacting with the device. Thus, the haptic generator 47 may vibrate all or a portion of the AVD 12 using an electric motor connected to an off-center and / or off-balance weight via a rotatable shaft of the motor, such that the shaft can rotate under the control of the motor (which in turn may be controlled by a processor such as processor 24) to create vibrations of various frequencies and / or amplitudes, and simulations of forces in various directions.

[0030] A light source such as a projector, such as an infrared (IR) projector, may also be included.

[0031] In addition to the AVD 12, the system 10 may include one or more other CE device types. In one embodiment, the first CE device 48 may be a computer game console that can be used to transmit computer game audio and video to the AVD 12 via commands sent directly to the AVD 12 and / or through a server, as described below, while the second CE device 50 may include similar components to the first CE device 48. In the illustrated embodiment, the second CE device 50 may be configured as a computer game controller operated by a player or a head-mounted display (HMD) worn by a player. The HMD may include a head-up see-through or non-see-through display for presenting AR / MR content or VR content (or, more generally, extended reality (XR) content), respectively. The HMD may be configured as a glasses-type display or a bulkier VR-type display sold by computer game console manufacturers.

[0032] In the illustrated embodiment, only two CE devices are shown, but it should be understood that a fewer or greater number of devices may be used. The devices herein may implement some or all of the components shown for AVD 12. Any of the components shown in the following figures may incorporate some or all of the components shown for AVD 12.

[0033] Referring now to the aforementioned at least one server 52, it includes at least one server processor 54, at least one tangible computer-readable storage medium 56, such as disk-based or solid-state storage, and at least one network interface 58 that, under the control of the server processor 54, enables communication with other illustrated devices over the network 22, and may indeed facilitate communication between the server and client devices in accordance with the present principles. It should be noted that the network interface 58 may be, for example, a wired or wireless modem or router, a Wi-Fi transceiver, or other suitable interface, such as a wireless telephone transceiver.

[0034] Thus, in some embodiments, server 52 may be an entire internet server or server "farm," and may include and perform "cloud" functions such that, in an exemplary embodiment for a network gaming application, devices of system 10 may access the "cloud" environment via server 52. Alternatively, server 52 may be implemented by one or more game consoles or other computers located in or near the same room as the other devices shown.

[0035] The components shown in the following figures may include some or all of the components shown herein. The user interfaces (UIs) described herein may be integrated and / or extended, and UI elements may be mixed and matched between UIs.

[0036] The present principles can employ various machine learning models, including deep learning models. Machine learning models consistent with the present principles can use a variety of algorithms trained using methods including supervised learning, unsupervised learning, semi-supervised learning, reinforcement learning, feature learning, self-learning, and other forms of learning. Examples of such algorithms can be implemented by computer circuits and include one or more neural networks, such as convolutional neural networks (CNNs), recurrent neural networks (RNNs), and a type of RNN known as a long-short-term memory (LSTM) network. Support vector machines (SVMs) and Bayesian networks can also be considered examples of machine learning models. In addition to the types of networks described above, the models herein may be implemented by classifiers.

[0037] Thus, as understood herein, performing machine learning may include accessing training data and then training a model on the training data so that the model can process additional data and make inferences. Thus, an artificial neural network / artificial intelligence model trained through machine learning may include an input layer, an output layer, and multiple hidden layers in between that are configured and weighted to make inferences regarding the appropriate outputs.

[0038] 2, an HMD 200, which may incorporate any or all of the components shown for any of the devices in FIG. 1, may include an outer display surface 202 on which is mounted at least one eye tracking (also referred to herein as pupil tracking) camera 204. It is noted that the size of the camera 204 shown in FIG. 2 may not be to scale. The camera 204 may be adhesively bonded to the outer display surface 202 or otherwise engaged to the surface 202 on the outer side of an IR-transmissive layer, described further below, i.e., on the side of the IR-transmissive layer opposite the eyes of the wearer of the HMD 200. The camera 204 is preferably located on the surface 202 along the nominal line of sight of the wearer's pupils when the wearer is looking straight ahead.

[0039] 3 illustrates an alternative HMD 300 in which a camera 302 is attached to the HMD by means of an arm 304 that will be positioned along the nominal line of sight 306 of the wearer's pupil when the wearer is looking straight ahead. The arm 304 may be stationary or it may be articulated to move the camera towards and away from the display.

[0040] 4 illustrates the layers of an exemplary HMD 400, with an innermost layer 402 closest to a pupil 404 of an eye 406 of a wearer of the HMD 400, which establishes the cathode. Next to the innermost layer 402 is an electron transport layer 408, then a blocking layer 410, then an emissive layer 412, which may include an organic light-emitting diode (OLED). Following the emissive layer 412, continuing outward from the innermost layer may be a hole transport layer 414, then a hole injection layer 416, and an anode 418 on a substrate 420.

[0041] As shown in FIG. 4 , an infrared coating, such as a near-infrared (NIR) coating 422, is deposited on the outer surface of substrate 420, which allows IR light to propagate through layer 422 but blocks visible light from propagating through layer 422. Coating 422 may include, for example, zinc selenide and / or zinc sulfide. In some embodiments, coating 422 may be applied to an inner layer of substrate 420. A camera 424, such as any of the cameras described herein, is juxtaposed with the outer surface of substrate 420 as described above, preferably along the line of sight of pupil 404 when the wearer is looking straight ahead, to directly image IR light reflected from the pupil. Thus, camera 424 is a camera capable of generating images from IR light.

[0042] FIG. 5 illustrates a display 500, such as any of the displays disclosed herein, including the HMD shown in FIGS. 2-4 , in which one or more (preferably multiple) IR-emitting illumination lamps 502 are arranged on an inner surface 504 of the display 500 to illuminate the pupil of a wearer's eye consistent with the principles described herein. In the example shown, the illumination lamps 502 are evenly spaced along the periphery 506 of the display 500, although it will be understood that other arrangements of illumination lamps 502 may be implemented. The illumination lamps 502 may be added to the OLED emitters in the emissive layer 412 shown in FIG. 4 after the OLEDs are formed, or they may be established by peripheral OLED emitters intrinsic to the emissive layer 412 itself, thereby performing two tasks: on the one hand, to emit light during active image formation to form part of the image presented on the display, and on the other hand, to emit IR illumination light for pupil tracking purposes consistent with the principles described herein.

[0043] Referring now to Figure 6, the OLED display in the HMD typically scans a horizontal line from top to bottom during a period "P" to present a frame of a requested image. During the period "P", a synchronization voltage V sync The voltage referred to as V is a low voltage, e.g., zero to V sync The period "P" may be, for example, two to twelve milliseconds (2 ms to 12 ms) long, and in one embodiment may be 8.5 ms, and frame refresh rates of 60 frames per second (fps), 120 fps, or 240 fps, as three examples, may be used. During the frame rendering period "P", the pupil tracking camera is not energized.

[0044] On the other hand, during frame rendering, V sync returns to low during the null period Δt, which is the period when no requested image is rendered. During the null period Δt, the tracking activation voltage graph V trackAs shown by , the pupil tracking camera described herein is activated. The length of the null period Δt can be, for example, two to six milliseconds (2 ms to 6 ms) in an exemplary implementation. Additionally, an IR illumination lamp, such as LED 502 shown in FIG. 5, is activated to emit IR light during period Δt, such that the eye is actively illuminated by IR radiation as the camera actively images the eye. Due to the timing of IR eye tracking occurring when no active frame rendering is occurring, the camera detects IR only from the eye's pupil, rather than IR that may be emitted as part of frame rendering. In the example shown in FIG. 6, the camera (and IR illuminator) is de-energized at the start of the next period "P" of frame rendering.

[0045] 7 and 8 illustrate the recognition that some pupil tracking may occur during active frame rendering under the following conditions: As shown by LED activation lines 700 on an OLED display 702, such as any of the displays described herein, line 1 is scanned first, then lines below are scanned until the Nth line directly above the pupil's nominal location 704 relative to the display is scanned, in a time during a frame rendering period "P," referred to herein as "scan time t." Lines N+1 and beyond below the Nth line are then scanned (after "scan time t") to render the frame of the requested image during period "P" to present the frame of the requested image.

[0046] 8 illustrates the present principles' understanding that the pupil may be tracked up during a portion of period "P" to present a frame of a requested image until the scanning of the Nth line shown in FIG. 7 is completed. More specifically, as in the embodiment of FIG. 6, during period "P" in FIG. 8, the synchronization voltage V sync is driven from a low voltage to a high voltage, and V syncreturns to low during the period Δt. During the period Δt, the tracking activation voltage graph V track A pupil tracking camera as described herein is activated, as indicated by Δt. Also, during the period Δt, an IR illumination lamp, such as LED 502 shown in FIG. 5, may be activated, so that the camera is actively imaging the eye and the eye is actively illuminated with IR radiation.

[0047] However, unlike in Figure 6, it will be appreciated that the pupil tracking camera (and, if necessary, the IR illumination lamp) may remain energized after the start of the next active frame rendering period "P" until "scan time t" when the next frame rendering period arrives, during which time the nominal line of sight of the pupil is not yet directed in the active frame rendering. Once "scan time t" is reached, energy supply to the pupil camera (along with the IR illumination lamp, if necessary) may be stopped until the start of the next null period Δt.

[0048] FIG. 9 illustrates example logic consistent with the disclosure herein that may be implemented by any one or more of the processors described herein. Beginning at block 900, a requested image from a computer simulation, such as a computer game, is rendered on a display, such as one of the HMDs described herein. Moving to block 902, during a frame such as that shown in FIG. 6, or from the start of a null period Δt until the “scan time t” of the next active frame rendering, such as that shown in FIGS. 7 and 8, a pupil tracking camera and, optionally, an IR illumination lamp, as described herein, are activated to generate an IR image of the wearer's pupil(s). The image is input to one or more machine learning (ML) models to derive gaze direction information from the image at block 904, and the image is output by the ML model at block 906 and input to a game engine or other source of requested image input to block 900 at block 908.

[0049] The ML model(s) used in block 904 may be trained on a ground truth set of pupil images and ground truth set gaze direction annotations.

[0050] Although particular embodiments have been shown and described in detail herein, it should be understood that the subject matter encompassed by this invention is limited only by the scope of the claims.

Claims

1. 1. An assembly comprising: at least one organic light emitting diode (OLED) display including at least one innermost surface and at least one substrate; a coating on the substrate, the coating being transparent to at least near-infrared (NIR) radiation but opaque to visible light; at least one camera configured to generate an image from IR light and positioned to receive light through said coating; at least one IR irradiating lamp configured to emit IR radiation toward the eyes of a wearer of the device; at least one processor configured with instructions to activate the camera or the lamp, or both the camera and the lamp, only during a null period between a first period and a second period of rendering a respective first and second frame of a requested image, starting from the beginning of the null period plus a portion, but not all, of a period of scanning the second frame; An assembly comprising:

2. The assembly of claim 1 , wherein the coating comprises zinc selenide.

3. The assembly of claim 1 , wherein the coating comprises zinc sulfide.

4. The assembly of claim 1 , wherein the OLED display comprises a micro OLED display.

5. The instruction:

2. The assembly of claim 1, wherein the assembly is operable to stop energy supply to the camera or the lamp, or both the camera and the lamp, at the end of the null period plus some but not all of the period for scanning the second frame.

6. The instruction:

2. The assembly of claim 1, wherein the assembly is executable to cut off the electrical supply to the camera or the lamp, or both the camera and the lamp at once, during the second period of rendering the second frame of the requested image, excluding a portion, but not all, of the period of scanning the second frame.

7. The assembly of claim 1 , wherein the camera is disposed on an outer surface of the substrate.

8. The assembly of claim 1 , wherein the camera is connected to an arm and oriented to image an outer surface of the substrate.

9. presenting frames of the requested image on at least one head mounted display (HMD); generating at least one image of a pupil of a wearer of the HMD during a null period between at least a first frame and a second frame; generating said image using an IR camera; energizing the camera during the null period only for a period that includes a portion of the second frame plus a period that includes all of the second frame; A method comprising:

10. 10. The method of claim 9, comprising illuminating the pupil with infrared (IR) light during the null period.

11. 11. The method of claim 10, comprising generating the image of the pupil using the IR light after the IR light has passed through a layer of material that blocks visible light.

12. The method of claim 9 , comprising using the image for eye tracking of the wearer.

13. 1. A head mounted display (HMD) for generating at least one computer-simulated requested image based at least in part on tracking at least one pupil of a wearer of the HMD, comprising: at least one organic light emitting diode (OLED) display; at least one pupil tracking camera configured to generate images from infrared (IR) light; at least one material configured to pass IR light from the pupil to the camera for generation of the requested image by the camera and to block visible light from the OLED display from the camera, such that at least one computer simulation engine configured to generate the requested image can do so at least in part based on images from the camera; at least one processor configured to energize the camera for at least one null period between first and second periods for scanning a first and second frame of each requested image, plus some but not all of the period for scanning the second frame; An HMD equipped with:

14. The HMD of claim 13 , wherein the substance is positioned between the pupil and the camera when the wearer is wearing the HMD.

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