1. Field of the Invention
The present invention relates to surface acoustic wave (SAW) touch sensitive technology, and more particularly, to apparatus and method for determining SAW touch sensitive area size.
2. Description of the Prior Art
Touch screen is an important human-machine interface of modern electronic product. It is widely adopted in various consumer electronics, such as smartphone, tablet computer, notebook computer, and etc. Touch screen can comprise but not limit to the following types: resistive, matrix resistive, capacitive, projected capacitive, electromagnetic sensing, infra-red sensing, and in-cell. The present invention relates to surface acoustic wave (SAW) touch sensitive technology, especially related to apparatus and method for determining SAW touch area size.
Usually, a touch screen comprises a display module and a sensor module stacked on the display module. User may use one part of human body such as finger or stylus to touch or approximate the sensor module. A processing device of the touch screen receives sensing information from the sensor module, accordingly. The working principle of SAW touch sensitive technology relies on the propagation of acoustic wave on the surface of object. In case another object touches the surface, the acoustic wave propagation is disrupted. The disruptive event is detected and used to determine the coordinates of touch.
The object providing surface mentioned above is usually a glass substrate such that user can see the underlying display module though the transparent glass substrate. The SAW is propagated on the surface of the glass substrate. Since the propagation speed on the surface of the glass substrate is constant, it is possible to calculate the coordinates where the object touches the surface according to the signal change measured and the constant wave propagation speed. In other words, the processing device coupled to the sensor module has to know parameters of SAW touch panel in advanced. Thus, the coordinate values can be derived accordingly.
Usually, one system vendor has more than one brand customer. Each brand customer may order more than one type of product. Each product may feature different sizes. For example, one brand may sell several All-In-One computers covering every aspect of market. They may comprise 10 to 12 inch light weight computers, 17 to 19 inch mainstream computers, and 20 inch high level computers. No matter their sizes, these products featuring different sizes of touch screen usually use a common processing device in considerations of design, purchase, manufacturing, inventory, and maintenance. The manufacture vendor of this common processing device is usually different to the system vendor and the brands. As mentioned above, the processing device coupled to different sized SAW sensor modules must be configured in order to connect these sensor modules.
From the view point of commerce, if the manufacture vendor of the processing device can provide a product which is capable of automatically detecting the size of SAW sensor module, the configuration step can be omitted accordingly. Thus, the manufacture sequence, cost, and time are also reduced as a result. Naturally, it enhances the competence of the processing device which is capable of automatic detecting the size of SAW sensor module. There is impossible to delay system integration due to configuration errors. Hence, there is a need of processing device and method for automatically detecting the size of SAW sensor module in the market in order to reduce the tool, cost, and time for parameter configuration.
From the above it is clear that prior art still has shortcomings. In order to solve these problems, efforts have long been made in vain, while ordinary products and methods offering no appropriate structures and methods. Thus, there is a need in the industry for a novel technique that solves these problems.