| With the diversification of computer functions,the peripherals that can access is also varied,touch screen is one of them.As a very convenient device,touch screen is widely used recently.Because of the increasing demand of user,the complexity of operation also increases,and the technology of multi-touch emerges as the times require.According to the differences of production’s materials,touch screen is devided into resistance touch screen,capacitive touch screen,sound-wave touch screen and infrared touch screen and so on.Infrared touch screen is one of the only touch screen which can support multi-touch,so it become the important carrier of multi-touch technology.It has very important application value,which infrared touch screen can be used in all kinds of operating systems.As a bridge of hardware and software,the function of driver is very important,and it decides whether a set of equipments can work properly or not.There have been some pioneering works about the research of multi-touch,and made much successful experience.For example,the main version of Windows operating system has supported multi-touch by HID protocol.So the main research platform of this paper is the operating system which use Linux kernel.The research work has been devided into two stages.Firstly,by studying the touch device management framework in the Linux kenel,we can find out the reasons why Linux operating system except for Android can’t support multi-touch.By adding TUIO driver module based on common touch screen driver framework in Linux kernel,we can achieve the function of multi-touch coordinate’s transfer of Linux operating system,and implement the simulation of multi-touch effect by writing a application procedure.Secondly,because the touch screen is easy to generate the phenomenon of touch points "drift",namely the touch points and the display points produce larger offset,the calibration algorethm should be designed to effectively control the drift errors.This paper attempts to improve the existing acquiring sampling point methods based on affine transformation algorithm.Affine transformation algorithm is one of the most widely-used methods in the touch screen calibration field.Because the affine transformation describes linear trasformation of two dimensional coordinates,which can realize the coordinate’s translation,rotation and scaling.This characteristic determins the affine transformation is very suitable for touch screen calibration.However,in the calibration process.the requirement for touch errors of Windows 8 is ±1mm and the pass rate of sample points must reach 4%.Therefore,simply using draw-point method has been unable to meet the requirement of accuracy.This paper tries to propose two improved calibration algorithm based on affine transform,one method use drawing lines instead of marking point,the other devide the screen into a plurality of areas to use multiple calibration.This two kind of methods can effectively improve the calibration precision.And we compare the draw-points calibration,multiple calibration and draw-lines calibration from operation,.complexity and accuracy.This paper integrated the above two parts into general infrared touchscreen driver in order to achieve infrared multi-touch operation and has expected results. |
