ALLPCB
Overview
Surface Light Wave (SLW) is a multipoint touch technology developed by Tianshitong. It uses the propagation properties of light in a specific band together with light-emitting circuitry to form a dense surface light wave network on the touch panel. When a touch object enters this network, it disrupts the light waves and creates localized gaps in the network, a phenomenon described here as a "net break".
How it works
A signal receiving circuit detects disruptions across the surface light wave network. By analyzing the degree and pattern of these "net breaks", the system can identify multiple simultaneous touch points. SLW supports true multipoint touch, enabling 2, 10, 16, 32 or more simultaneous touch points without changing the LCD manufacturing process.
Features and advantages
- True multipoint support: SLW can scale to support more than 10 simultaneous touch points and can be expanded to 16 or 32 points as needed. Many touchscreens in the Chinese market that claim multipoint support actually only support two points and are prone to ghost points; they are not true multipoint. This SLW approach was the first in the Chinese market to support 32 simultaneous touch points.
- Shape recognition: Unlike conventional infrared touchscreens that use x-y scanning and can only return the center coordinate of an occluding object, SLW can capture the approximate contour of the object contacting the screen. This enables additional applications, such as distinguishing a palm from a finger.
- High responsiveness: response time is under 20 ms.
- Wide panel compatibility: suitable for LCDs from 19 to 100 inches. The circuit is designed as a modular unit, allowing panels within this range to be tiled or combined.
- No conductive glass or micro optical cameras required: SLW does not require a conductive glass substrate and the surface has no intervening medium. Transmittance can reach up to 92% (100% without glass), producing no measurable impact on display quality. The system is not constrained by precision instruments such as micro optical cameras.
- Contact flexibility: supports non-pressure touch with hands, pens, or any opaque object. No touch pressure is required, and electromagnetic or capacitive pens are not necessary.
Applications
Because SLW can detect multiple touch points and approximate object contours, it can be applied to a variety of interactive display scenarios that require high touch point counts, fast response, and operation without specialized touch pens or conductive overlays.
