# Differential Signal-Amplitude-Modulated Multi-Beam Remote Optical Touch Based on Grating Antenna

## TL;DR

This paper introduces a new optical touch system using grating antennas to enable accurate multi-point remote touch control.

## Contribution

A novel differential amplitude modulation scheme for grating antenna-based multi-beam optical touch is proposed.

## Key findings

- The system achieved two-point optical touch with under 3 mm position accuracy error.
- Response time was less than 7 ms at a 10 kHz modulation frequency.
- The method enables remote multi-point touch with high precision.

## Abstract

As screen sizes are becoming larger and larger, exceeding human physical limitations for direct interaction via touching, remote control is inevitable. However, among the current solutions, inertial gyroscopes are susceptible to positional inaccuracies, and gesture recognition is limited by cameras’ focus depths and viewing angles. Provided that the issue of ghost points can be effectively addressed, grating antenna light-trapping technology is an ideal candidate for multipoint inputs. Therefore, we propose a differential amplitude modulation scheme for grating antenna-based multi-beam optical touch, which can recognize different incidence points. The amplitude of the incident beams was first coded with different pulse widths. Then, following the capture of incident beams by the grating antenna and their conversion into electrical currents by the aligned detector arrays, the incident points of the individual beams were recognized and differentiated. The scheme was successfully verified on an 18-inch screen, where two-point optical touch with a position accuracy error of under 3 mm and a response time of less than 7 ms under a modulation frequency of 10 kHz on both incident beams was achieved. This work demonstrates a practical method to achieve remote multi-point touch, which can make digital mice more accurately represent the users’ pointing directions by obeying the natural three-point one-line aiming rule instantaneously.