The characteristic appearance of Wacom's pen tablet devices is of a slim and lightweight electronic pen that has no need of an obstructive cord or battery, along with a completely non-contact-type sensor board that makes possible a wide diversity of flexible built-in processes. These devices make adept use of Wacom's originally developed EMR (Electo-Magnetic Resonance) Technology.
Most non-contact-type pen tablet devices apart from those employing EMR® Technology require some kind of internal power source to generate the signal on the pen-side circuit that enables the pen's coordinates on the tablet to be detected. These include devices powered by electricity supplied via a cord and others equipped with internal batteries. However, cords can be bothersome to use, and there is always a worry that batteries may run down at a crucial time. Moreover, the presence of cords or batteries makes it harder to optimize the pen's size, weight, shape and balance. Accordingly, these devices cannot be said to provide operational freedom without constraint.
Despite being non-contact systems, pen-input devices utilizing EMR® Technology do not require any cable or built-in battery-based power supply at all. This is because the tablet surface incorporates a sensor board that detects the pen's movement. Weak energy is induced in the pen's resonant circuit by a magnetic field generated by the sensor board surface. The pen's resonant circuit then makes use of this energy to return a magnetic signal to the sensor board surface.
By repeating this movement, the board detects information on the pen's coordinate position and angle, as well as on its general operating condition including speed and writing pressure, etc. A sensor unit is equipped at the side of the sensor board to switch the magnetic field on and off and to receive signals at high speed and detect various kinds of information. In principle, all Wacom's tablet devices are composed of this kind of sensor unit and electronic pen. In addition, the sensor unit itself consists of a sensor board and a control board.
The sensor board consists of a thin sheet manufactured from glass epoxy resin or from a polyimide and PET formed film in which a large number of overlapping loop [antenna] coils are arranged in a matrix in the x and y axis directions. On the rear side of the sensor board is a shield board installed to block out noise from other components such as the motherboard and nearby circuits. The thickness of the entire sensor board that combines these elements is only 0.6mm. Although there are slight differences according to the size of the sensor surface, in the case of a 2.2" (diagonal) sensor, the thickness of the board is only 0.25mm.
The control board discharges alternating current to selected loop coils from among the array installed in the sensor board. This excites the coils, causing them to generate magnetic fields. When the pen passes through these magnetic fields, it picks up and stores energy in its resonant circuit.
The control board first detects the pen's rough location by scanning the loop coils on the sensor board. After that, the control board scans multiple loop coils in the vicinity of the pen, and uses the information to calculate the pen's coordinate value precisely.
A W8000 series custom LSI is built into the control board. In addition to being equipped with a DSP circuit that performs at high speed the large amounts of digital processing that in conventional systems is handled by the CPU, this LSI is also designed to operate with low power consumption. Thanks to this custom LSI, the load on the control board's CPU is greatly reduced, which makes it possible to employ a low-performance, low-priced CPU.
Since Wacom's electronic pens do not require batteries and feature very simple circuitry, users have a wide range of design options in terms of thickness and lightness. Moreover, the writing pressure detected by our electronic pens can be freely set to between the standard purpose 256 steps and the maximum level of 1,024 steps, which is widely used in the professional field. We produce pen types that utilize changes in inductance and changes in capacitance.
With these technologies, we can produce electronic pens that answer a host of user demands. For example, a pen can be designed to be stored in a package such as a PDA by making it thinner, it can be finished with an easy-to-hold grip and an easy-to-hold weigh balance, and it can be equipped with an eraser function, etc.
In addition, in the case that a pen input sensor is built into an LCD (Liquid Crystal Display), the magnetic fields generated by the display's backlighting and by the transformers of the AC-DC converter must be blocked to ensure that the pen's operation is not affected.
In products that employ Wacom's Penabled Technology, magnetic field noise is reduced by a combination of altering the arrangement of installed parts, adjusting the frequencies of parts so that they don't influence the sensor board or the electronic pen, and tightly shielding parts.
Furthermore, even in cases such as where the LCD's peripheral metal frame influences the magnetic field in such a way as to cause coordination gaps around the edges of the sensor board, Wacom's Penabled Technology maintains coordination accuracy by changing the correction data memorized in the control board.