2 Visually Coupled Systems A system that integrates the natural visual and motor skills of an operator into the system he is controlling.Basic ComponentsAn immersive visual display (HMD, large screen projection (CAVE), dome projection)A means of tracking head and/or eye motionA source of visual information that is dependent on the user's head/eye motion.
3 Head-Mounted Displays Optical SystemImage Source (CRT or Flat Panel (LCD))See–Through or Non–See–ThroughMounting ApparatusWhat are some factors?EyeglassesWeightSolutions?EarphonesPosition Tracker
4 Field of ViewMonocular 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.
5 Focal Length & DiopterFocal Length - The distance from the surface of a lens (or mirror) at which rays of light converge.Diopter - The power of a lens is measured in diopters, where the number of diopters is equal to 1/(focal length of the lens measured in meters).
6 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.
7 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.
8 Vignetting and Eye Relief The blocking or redirecting of light rays as they pass through the optical system.Eye Relief DistanceDistance from the last optical surface in the HMD optical system to the front surface of the eye.
10 The EyeAccommodation - Term used to describe the altering of the curvature of the crystalline lens by means of the ciliary muscles. Expressed in diopters.Retina - The sensory membrane that lines the back of the eye and receives the image formed by the lens of the eye.Fovea - The part of the human retina that possesses the best spatial resolution or visual acuity.CorneaCrystallineLensFoveaOpticNerveRetina
11 Properties of the Eye Approximate Field of View Acuity 120 degrees vertical150 degrees horizontal (one eye)200 degrees horizontal (both eyes)Acuity30 cycles per degree (20/20 Snellen acuity).
12 Simple FormulasVisual 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 degreeTo convert to Snellen acuity (as in 20/xx)Vres = 600/xx (20/47)
13 Optical SystemMove image to a distance that can be easily accommodated by the eye.Magnify the image
14 Simple Magnifier HMD Design qpfImageEyeEyepiece(one or more lenses)Display(Image Source)1/p + 1/q = 1/f wherep = object distance (distance from image source to eyepiece)q = image distance (distance of image from the lens)f = focal length of the lens
15 Thin Lens Equation 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 lensConventions:If the incident light comes from the object, we say it is a real object, and define the distance from the lens to it as positive. Otherwise, it is virtual and the distance is negative.If the emergent light goes toward the image, we say it is a real image, and define the distance from the lens to it as positive.f = positive for a converging lensA light ray through the center of the lens is undeflected.
17 Resolution (low) 160 x 120 color pixels per eye (high) 1000+ x 1000+ Note that resolution and FOV are independentAnother important factor: pixel densityPixels per degree of FOV
18 LEEP Optics Large Expanse Extra Perspective Give very wide field of view for stereoscopic imagesHigher resolution (more pixels) in the middle of the field of view, lower resolution on the peripheryPincushion distortion
19 Fresnel LensA lens that has a surface consisting of a concentric series of simple lens sections so that a thin lens with a short focal length and large diameter is possibleMore even resolution distributionLess distortionfrom lanternroom.com
21 Distortion in LEEP Optics A rectangleMaps to thisHow would you correct this?
22 To correct for distortion Must predistort imageThis is a pixel-based distortionGraphics rendering uses linear interpolation!Too slow on most systemsPixel shaders!Render to Texture
23 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?
25 Collimated: p=f 1/p + 1/q = 1/f q = , if p=f If the image source is placed at the focal point of the lens, then the virtual image appears at optical infinity.f
26 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.Relay LensImageIntermediateReal ImageEyepieceExitPupil
27 Exit PupilThe 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.Relay LensImageIntermediateReal ImageEyepieceExitPupil
28 Virtual Research V8 HMD Display Optical Solve Pros/Cons Dual 1.3” diagonal Active Matrix Liquid Crystal DisplaysResolution per eye: 640 x 480 (307,200 color elements)focal length = 1mOpticalField of view: 60° diagonalSolveWhat is the cycles per degree?What is its horizontal and vertical field of view?Pros/Cons
29 Characteristics of HMDs ImmersiveYou are inside the computer worldCan interact with real world (mouse, keyboard, people)Mask out real worldErgonomicsLength of use is limited, cue conflict!!! (accomodation vs. parallax, perspective, etc.)Resolution and field of viewTethered
30 Exercise (Part of Quiz grade) Due: October 20th (Thursday) Fill in the following table through research on the Internet:Virtual ResearchV8ForteVFX5DTHMD 800SonyGlasstronPLM-A351 column for best unit found for each categoryResolution (RGB pixels)FOV (d, w, h)Distance from eye to Virtual ImageStereo?PriceWeightProsCons