A grid of light, not a layer of film
An infrared touch screen contains no sensor in its surface at all. Around the inside edge of the frame sit two facing strips: infrared LEDs on two adjacent sides, photoreceptors on the other two. The LEDs maintain a dense crosshatch of invisible beams a few millimetres above the display glass. Anything that enters that plane — finger, glove, stylus, a sleeve at the wrong moment — blocks beams on both axes, and the controller computes the interruption's centre. That is the entire mechanism, and every strength and weakness of the technology follows from it.
The 32768 × 32768 number
The frame programme in this catalogue states a sensing resolution of 32768 × 32768. There are not 32,768 physical beams per side — there cannot be, in a profile a few centimetres wide. The figure is the interpolated coordinate space: the controller measures how much each beam is occluded and interpolates position between beams to sub-beam precision. The practical consequence is real — smooth diagonal lines, accurate corners after calibration — but the number should be read as a coordinate resolution, not a beam count. Sellers who present it as physical sensors are decorating; the honest version is impressive enough.
Why IR scales and PCAP doesn't
Adding size to an IR frame adds profile length and LEDs arithmetically — the 500-inch spliced frame is the 43-inch frame's idea, repeated. Adding size to a capacitive sensor multiplies electrode area, controller channels and glass cost together, which is why the PCAP catalogue ends at 27 inches while the frame programme is effectively unbounded. The comparison guide prices the consequences.
Multi-touch from a single plane
Multiple simultaneous interruptions create a classic ambiguity — two touches define two possible diagonal pairings. Modern frame controllers resolve it by tracking touch blobs frame-to-frame at scanning rates in the millisecond class, which is how the catalogue's frames honestly support 10–64 simultaneous points. The touch points guide explains when those points matter.
The technology's real limits
Direct sunlight carries infrared and can swamp receivers; the sensing plane can be triggered by anything that crosses it, including an insect on an outdoor unit; and the frame adds a bezel profile that flush-glass designs cannot accept. Every one of those limits is manageable when declared at specification — which is the recurring theme of this site's guides, and the reason the inquiry form asks about environment before model.