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Output Devices

Output Devices. Output Devices. Visual Auditory Haptic. Visual Devices. Dimensions Stereoscopic/monoscopic Image resolution Field of view Display tech Ergonomic factors Cost. Human Eye. 126 million photoreceptors Eye-gaze technology not useful yet Calibration Error

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Output Devices

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  1. Output Devices

  2. Output Devices • Visual • Auditory • Haptic

  3. Visual Devices • Dimensions • Stereoscopic/monoscopic • Image resolution • Field of view • Display tech • Ergonomic factors • Cost

  4. Human Eye • 126 million photoreceptors • Eye-gaze technology not useful yet • Calibration • Error • Overlaying control • IPD • 53-75 mm

  5. Head-tracked Displays • Displays in which the user’s head is tracked and the image display screen is located at a fixed location in physical space. • Examples? • CRT • Virtual Workbench or ImmersaDesk • CAVE • Many large screen displays

  6. Stationary Display 3D Glasses Head Tracker CRT HTD (Fishtank VR)

  7. Standard Display Stereoscopic Display Screen User C C A A B B Stereoscopic Display

  8. 3D Glasses 3D Display 3D Object Virtual Workbench

  9. CAVE

  10. Any Projected Large Stereoscopic Screen

  11. Characteristics • Large • Projection-Based (except for Fishtank VR) • Stereoscopic • Head Tracked • Stationary Display Screen(s) • Let’s try to identify the pros and cons and application domains

  12. 3D Glasses 3D Display 3D Object

  13. Large Screen Projection • Infrastructure • Front Projection (user occlusion) • Back Projection (takes up space)

  14. Advantages Viewer not isolated Collaboration Minimal physical gear Good resolution Large field of view Disadvantages One person “sweet-spot” Real objects may occlude virtual objects Synchronization Light Reflection Bleeding Equipment footprint Alignment Large Screen Projection

  15. Head-Mounted Display

  16. Visually Coupled Systems • Operator uses natural visual and motor skills for system control • Basic Components • An immersive visual display (HMD, large screen projection (CAVE), dome projection) • Tracking system for head and/or eye motion

  17. HMD Optical System • Image Source • CRT or Flat Panel (LCD) • Video, See–Through or Video-Pass Through

  18. HMD Optical System • Image Source • CRT or Flat Panel (LCD) • Video, See–Through or Video-Pass Through

  19. Head-Mounted Displays Optical System • Mounting Apparatus • What are some factors? • Eyeglasses • Weight • Earphones • Trackers

  20. Field of View Monocular FOV is the angular subtense (usually expressed in degrees) of the displayed image as measured from the pupil of one eye. Total FOV is the total angular size of the displayed image visible to both eyes. Binocular(or stereoscopic) FOV refers to the part of the displayed image visible to both eyes. FOV may be measured horizontally, vertically or diagonally.

  21. Focal Length & Diopter Focal Length - The distance from the surface of a lens at which rays of light converge. Diopter - The power of a lens. Equal to 1/(focal length of the lens measured in meters)

  22. Ocularity Ocularity • Monocular - HMD image goes to only one eye. • Biocular - Same HMD image to both eyes. • Binocular (stereoscopic) - Different but matched images to each eye.

  23. IPD Interpupillary Distance (IPD) • IPD is the horizontal distance between a user's eyes. • IPD is the distance between the two optical axes in a binocular view system.

  24. Vignetting and Eye Relief Vignetting • The blocking or redirecting of light rays as they pass through the optical system. Eye Relief Distance • Distance from the last optical surface in the HMD optical system to the front surface of the eye.

  25. Cornea Crystalline Lens Fovea Optic Nerve Retina Basic Eye

  26. Properties of the Eye • Approximate Field of View • 120 degrees vertical • 150 degrees horizontal (one eye) • 200 degrees horizontal (both eyes) • Acuity • 30 cycles per degree (20/20 Snellen acuity).

  27. Simple Formulas • Visual Resolution in Cycles per degree (Vres) = Number of pixels /2 (FoV in degrees) Example: (1024 pixels per line)/(2*40 degrees) = Horizontal resolution of 12.8 cycles per degree • To convert to Snellen acuity (as in 20/xx) Vres = 600/xx (20/47)

  28. Optical System • Move image to a distance that can be easily accommodated by the eye. • Magnify the image

  29. Simple Magnifier HMD Design q p f Image Eye Eyepiece (one or more lenses) Display (Image Source) 1/p + 1/q = 1/f where p = object distance (distance from image source to eyepiece) q = image distance (distance of image from the lens) f = focal length of the lens

  30. Virtual Image Virtual Image Lens Display

  31. Resolution • (low) 160 x 120 color pixels per eye • (high) 1000+ x 1000+ • Note that resolution and FOV are independent • Another important factor: pixel density • Pixels per degree of FOV • How can we use the make up of the eye to better leverage resolution?

  32. Cornea Crystalline Lens Fovea Optic Nerve Retina Basic Eye

  33. LEEP Optics • Large Expanse Extra Perspective • Very wide FOV for stereoscopic images • Higher resolution in the middle of FOV • Lower resolution on the periphery • Pincushion distortion

  34. Fresnel Lens • A lens consisting of a concentric series of simple lens sections • Result is a thin lens with a short focal length and large diameter • More even resolution distribution • Less distortion • from lanternroom.com

  35. Distortion in LEEP Optics A rectangle Maps to this How would you correct this?

  36. To correct for distortion • Predistort image • This is a pixel-based distortion • Graphics rendering uses linear interpolation! • Too slow on most systems • Pixel shaders! • Render to Texture

  37. Distorted Field of View • Your computational model (computer graphics) assumes some field of view. • Scan converter may over or underscan, not all of your graphics image may appear on the screen. • Are the display screens aligned perpendicular to your optical axis?

  38. Distance along z-axis Distorted FoV (cont.)

  39. Exit Pupil Intermediate Real Image Image Relay Lens Eyepiece Compound Microscope HMD Design Relay lens produces a real image of the display image source (screen) at some intermediate location in the optical train. The eyepiece is then used to produce an observable virtual image of this intermediate image.

  40. Exit Pupil Intermediate Real Image Image Relay Lens Eyepiece Exit Pupil • The area in back of the optics from which the entire image can be seen. Important if IPD not adjustable. • Compound microscope optical systems have a real exit pupil. • Simple magnifier optical systems do not have an exit pupil.

  41. Virtual Research V8 HMD • Display • Dual 1.3” diagonal Active Matrix LCD • Resolution per eye: 640 x 480 • focal length = 1m • Optical • Field of view: 60° diagonal • Solve • What is the cycles per degree? • What is its horizontal and vertical field of view? • Pros/Cons

  42. Characteristics of HMDs • Immersive • You are inside the computer world • Can interact with real world (mouse, keyboard, people) • Mask out real world (including body) • Ergonomics • Headborn weight • Length of use • Cue conflict • accommodation vs. parallax • Perspective • Resolution and field of view • Tethered • Avatars

  43. Exercise (Part of Quiz grade)Due: March 26th (Monday) • Fill in the following table through research on the Internet:

  44. Hand Mounted Displays • Binoculars • 1280x1024 • $19900

  45. Floor Supported Displays • Articulated mechanical arm • Offload weight • 0.2 ms Latency • High accuracy • 0.1 degree orientation error • Pole in the way • Limited Space (6’ diam, 3’ hgt) • Good FOV • Good resolution (1280x1024) • Fakespace Boom3C • WindowsVR • Differences • Stereo • Tracking • Advantages

  46. Desk Supported Displays • Fishtank VR • Autostereoscopic Displays • Addresses weight fatigue • Tracking? • DTI 2018XL Virtual Window • Elsa Ecomo4D

  47. Monitor Large Volume Displays • Multiple people • Monitor Based LVD • Fishtank VR • With limited FOV, what is a possible solution? • Exaggerate tracking • More monitors (synch, bezel) • Most use active stereo (shutterglasses) • 29-32% transmittance • $100-800 • Can be used for prolonged periods

  48. Projector LVD • Workbench • CAVE • $300-500k with SGI • $100k with PC clusters • Issues? • Large wall displays

  49. Sound Displays • What are good goals for VR Sound Displays • Compare importance to: • Movies • Video Games • What role does sound play? • Interactivity • Immersion • Perceived image quality(!) • Dimensions • Mono/Stereo/”virtual sound” • Tracker • Occlusion • What does it take to uniquely place a sound source?

  50. 3D Sound • Azimuth Cues • Interaural Time Difference • head radius/(speed of sound(θ+sin θ)) • Interaural Intensity Difference • High frequency • Head shadow effect • Elevation Cues • How are ears modeled? • If simple holes what is the problem? • Pinna effects sound propagation • Frequency attenuation and amplification

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