IR Point Tracking

IR LEDs at the screen and a camera in the gun: the Wii, Gun4IR, Samco and OpenFIRE way, with cameras, layouts and interference.

Firearms

IR Point Tracking · Deep Dive

IR Point Tracking

Four points of light are enough to know where a gun is pointing.

IR LEDs at the screen and a camera in the gun: the Wii, Gun4IR, Samco and OpenFIRE way, with cameras, layouts and interference.

Photo: A Wii Remote aimed at a television at E3 2006; the Sensor Bar's two infrared clusters show as faint purple points under the picture by Alex Hansen · CC BY 2.0

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    Volumes

    1. Vol 1 The Camera That Sees Only Dots — How a Multi-Object Tracking Sensor Works Markers at the screen and a camera in the gun: what happens on the sensor die every frame, what the Wii-class camera and the PixArt PAJ7025 actually report, how 128 pixels become 1,024 coordinates, and the frame-subtraction feature no light gun uses yet
    2. Vol 2 The Emitters — Wavelength, Radiant Intensity and the Link Budget Why the camera's filter, not preference, picks 850 or 940 nm; what sunlight and a tungsten lamp put in each band; how many milliwatts per steradian reach the gun at 1 to 5 m; why a point is a cluster of LEDs that must stay one blob; and why the wide-angle PixArt R3 collects a thirty-ninth of the R2's light
    3. Vol 3 Geometry — How Many Points, and Where to Put Them Each point fixes two numbers: two points give aim, roll and distance; four give a full perspective map of a flat screen. A simulation of the error each leaves, the Wii bar, GunCon 3 markers, square and diamond layouts read as geometry, and the layout proposed for this build
    4. Vol 4 Field of View, Distance and Screen Size — The Playing Envelope How close the player can stand before emitters leave the camera's view, square against diamond; how far before the points grow too dim, too close together or too coarse; what the wide lens and the LED beam each cost at close range; and three living rooms worked through for the Wii-class camera, the PixArt R2 and the R3
    5. Vol 5 Interference and Failure Modes — Sunlight, Lamps, Remotes, Reflections and Points That Misbehave Per pixel, a sun glint off glass outshines an emitter nine to thirty-six times, and a sunlit wall comes within a factor of five for the wide-angle R3; filament lamps, remote controls, a second gun system and glossy furniture; the ways a point merges, splits, swaps or vanishes; and a symptom-to-fix table
    6. Vol 6 Measuring It — An Optical Bench Procedure with the ADP3450 Seven tests that turn this dive's arithmetic into numbers: each emitter's intensity and match, the bar's steadiness, what the camera actually reports, centroid noise in screen millimetres, range and the dropout map, a survey of the room, and the 940 nm bar the PixArt camera should not see