BACKGROUND OF THE INVENTION Information is provided to a computer in a number of ways. One way of providing information is by direct input from a user. The most common user interface for inputting information is the keyboard. The keyboard requires the user to type information in the same manner as a typist with a typewriter. However, this is not the only way a user can enter information.

In order to access and browse the Internet, for example, the user/browser needs a mouse or pen-input device such as a light-pen, a keyboard and the ability to perform secure transactions. For users with a personal computer (PC), today virtually every new system has a mouse and a keyboard.

Another method of interacting either with a computer video monitor or a TV video monitor relies upon the relative position of a cursor to a location on the video monitor, such as a cathode ray tube (CRT). This can be accomplished by use of a mouse, light pen or other conventional devices. A mouse is a device that rests on a pad next to the computer and generally includes a ball which responds to the movement of the mouse by the user's hand in an x-y plane.

This motion is translated onto the CRT by way of a cursor which points to a specific location. When positioned correctly, the user may depress one or more buttons on the mouse to direct the computer to perform an action dictated by the cursor's location. That action can take many forms. Three such options are: 1) to issue a command to perform some function, or; 2) request information, or; 3) select from a menu of available options.

A light pen is similar in appearance to a standard inkpen-type writing instrument. It differs from the mouse, in that the tip of the light pen when placed in close proximity with the surface of the CRT, receives light signals, via a photo detector, emanating from the illumination of the phosphorous coating as the electron gun within the CRT scans the pixels on the internal surface of the CRT. Light pens interact directly with the video monitor's screen in the manner of a touchscreen, in providing the absolute positioning and pen-type input of a digitizing tablet, but do not suffer from the confusion and ambiguity of a relative positioning mouse. For most operating systems, light pens are used as pointing devices with the same basic functional characteristics, relative to the operating system, as a mouse. Special device driver software, supplied by the light pen manufacturer, provides the light pen with these characteristics. The light pen is typically provided buttons, that allow the user to execute a number of options in a manner similar to the buttons on a mouse.

Light pens are preferred over a mouse by many users. One reason for this is that the light pen does not require a pad and thus occupies less space on a desk.

Another reason is that the use of a light pen for drawing is more comfortable, as it is closely aligned with the method by which most people learn to draw. That is, with a pen, pencil, or brush.

An increasing number of video and computer monitors are not based on CRT technology and are flat and thin. They are based on technologies such as charge-coupled displays (CCD) or thin film transistor (TFT). CCD is a semiconductor technology used to build light-sensitive electronic devices such as image scanners. Each CCD chip consists of an array of light-sensitive photocells. The photocell is sensitised by giving it an electrical charge prior to exposure. TFT is a technology for building the liquid crystal display (LCD) screens that are commonly found on laptop and palm computers, as well as cellular phones, and the upcoming 3G models combining both cellular phone and PC resident Internet browsing capabilities.

TFT screens are brighter and more readable than dual-scan LCD screens.

The light pen cannot be used on video and computer monitors that are based on non-CRT technology, since in the other technologies there is no scanning of the screen with a raster beam. Detecting the position of the raster beam enabled the light pen to detect its position on the screen.

The use of pen devices in computer applications is known, for use as a pointing device, for selection of CRT screen monitor options on a menu, for example.

In US Patent 4,656,662 to Filliman et al, there is described a pen device for use with a

CRT for generation of signature or other identification indicia by movement of the pen device on the CRT screen. Positional information is captured from the screen by the pen device, using high resolution means to provide precise positional data, and this information may be compressed and collected to form a signature which can be stored and subsequently used as a reference for identification purposes.

In US Patent 5,877,752 to Puthoff et al, there is described a light pen computer interface system, utilizing a coil located externally of the computer's CRT display monitor to sense the magnetic field which provides the raster for the CRT.

In US Patent 5,586,002 to Notarianni, an"inductive pen"is mentioned as an alternative to a light pen."The second type of pen based computer uses an inductive pen which does not need to be connected by a cable to the pen based computer." Thus, an inductive pen is known in the art, but development for specific use and refinement for emerging technologies is not known. In particular, an inductive pen is susceptible to overwhelming electronic interference, or"noise,"during the transmission of positional information.

Therefore, it would be desirable to provide an inductive pen which overcomes noise and other obstacles to a user-friendly, inexpensive and easy-to-use computer, interactive video and/or E-commerce compatible positional information transmission system.

SUMMARY OF THE INVENTION Accordingly, it is a principal object of the present invention to overcome the disadvantages associated with prior art positional information transmission systems, and to provide a simple-to-use inductive pointing device, i. e. an"inductive pen,"to allow a high level of positioning accuracy, reliability and convenience when interacting with a computer or television monitor, for example, whether or not for use over the Internet, intranet or other communication network.

The inductive pen of the present invention is wireless, and"stupidly" transmits at a constant frequency, which is received by a pair of stationary coils in a pen control unit (PCU). The PCU, in turn, is wired to a personal computer (PC), or other central processing unit (CPU), and thereby digitally transmits the positional information. When the PCU is connected to the PC, it may receive power from the PC, for example, through a separate pin of the USB port. If the PCU is not connected to the PC, it may receive its power from batteries. The PCU calculates the position of

the pen by triangulation, and then communicates the coordinates, via an infrared (IR) or radio frequency (RF) signal, or wires in the case where it is connected to the PC.

The inductive pen is used in the manner of a mouse in conjunction with a computer or TV screen, or in the case of handwriting, or drawing, the pen is used for direct entry to the system via the monitor screen. The pen provides the ability to hand-write on the screen, sign documents, etc. The inventive pen can be used as a comprehensive, effective and low cost device, and being inductive, is compatible not only with CRT, but also CCD and TFT video monitors.

The pen has an inductive coil that transmits an electromagnetic (e/m) wave.

The position of the pen relative to a two-dimensional surface, such as a video monitor, is measured as a triangulated distance from two inductive receiver coils, which may be incorporated in the two-dimensional surface. The distance of the pen from each coil is proportional to the amplitude of the received e/m wave.

The PCU may be connected to the PC using the USB. A driver in the PC receives the positional information and uses it to implement another source of positional information in parallel with the mouse.

An inductive pointing device system is disclosed for data capture of the position of the device relative to a monitor screen, while stillinall minimizing the noise inherent in the system. The system includes a pointing device comprising a casing suitable for holding in the hand of a user and an inductive coil for transmitting a signal having a single electromagnetic frquency. The system also includes at least one actuator to elicit a control signal and a pen control unit (PCU) for receiving said transmitted signal by means of at least two stationary coils. There is also an analog subsystem for analog processing of said received signal and a digital subsystem for interactivity with said analog subsystem to digitally process said signal and calculate the position of said pointing device, such that noise effects associated with said system do not interfere with the continuous accurate determination of said position of said pointing device.

A method is disclosed for the use of the inductive pointing device system for data capture of the position of the device relative to a monitor screen, while minimizing the noise inherent in the system, said method comprising a first step of pointing said device by a user in proximity to the monitor screen. Additional steps include transmitting a signal by said pointing device for reception by said at least two coils, calculating the position of the pointing device by said pen control unit (PCU) and transmitting the positional information by the PCU, such that noise effects

associated with said system do not interfere with the continuous accurate determination of said position of said pointing device.

Other features and advantages of the invention will become apparent from the following drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention with regard to the embodiments thereof, reference is made to the accompanying drawings, in which like numerals designate corresponding elements or sections throughout, and in which: Fig. la is a schematic illustration of the details of an inductive pen for use with the transaction system of the present invention; Fig. Ib is an overall schematic illustration of an integrated inductive pen, operated in an exemplary manner with a smart card reader transaction system, constructed and operated in accordance with the principles of the present invention; Fig. Ic is a schematic illustration of the use of the pen control unit for implementation of a writing pad; Fig. 2 is a block diagram of an inductive pen control unit, constructed and operated in accordance with the principles of the present invention; and Fig. 3 is a flow chart of the sequence of operation of analog signal processing by the pen control unit, constructed and operated in accordance with the principles of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The pen system of the present invention comprises a small pen device 100 for transmitting an electromagnetic reference signal and two stationary pickup sensors which receive the reference signal and feed a signal processing unit which uses the reference signal to calculate relative pen position with respect to the two sensors' physical positions. Each sensor receives the reference signal and feeds it through a signal conditioning circuit, which performs noise filtering and gain leveling on the analog signal.

Referring now to Fig. la, there is shown a schematic illustration of the details of an inductive pen 100, constructed and operated in accordance with the principles of the present invention. Inductive pen 100 has a casing 112 suitable for holding in the hand of a user. Inductive pen 100 has an inductive coil transmitter element 126 located on the top of pen 100, behind a hollow cylindrical projection, which transmits an electromagnetic wave, which is in turn received by a pen control unit. Preferably, located on the top of pen 100 is a spring-loaded micro-switch 140 that senses when the pen projection 150 is alternatively pressed directly against a video monitor screen, such as a CRT or thin-film transistor (TFT) screen, or any surface coupled to a PCU, emulating a standard left mouse button click. Micro-switch 140 is uniquely designed to allow pressing while holding pen 100 diagonally at any angle to the screen, up to 45 degrees. The plastic of the pen-top is designed in such a way to prevent scratching the video monitor screen. Pen 100 also has depressable buttons 110 and 130, which provide functions similar to the left and right buttons of a standard click-mouse device.

Thus pointing at a location on the screen, and pressing button 150, for example, provides the same result as pressing pen projection 150 against the same location on the screen.

Fig. Ib is an overall schematic illustration of an integrated inductive pen, operated in an exemplary manner with a smart card reader transaction system, constructed and operated in accordance with the principles of the present invention. In Fig. I b there is shown an exemplary embodiment of an integrated inductive pen with a smart card reader system 160, constructed and operated in accordance with the principles of the present invention. System 160 comprises an inductive pen 100, transmitting an electromagnetic (e/m) wave 165 to a smart card reader housed in a pen control unit (PCU) 200, into which has been inserted a smart card 168. Fig. Ib shows only the approximate location of the microelectronics comprising PCU 200. The

details of PCU 200 are described hereinbelow in Fig. 2. PCU 200 preferably has a pair of inductive coils for receiving e/m wave 165, and by means of a triangulation algorithm is able to determine the location of pen 100. PCU 200 is preferably attached to a PC through a USB port, wherein a CRT monitor 170, or other type of display screen is incorporated in the PC. The smart card reader housed in PCU 200 has a slot for inserting therein a smartcard 168, which may be a credit card having encrypted information for use with credit card verification protocols. Typical desktop icons 172 are shown, which may be pointed and clicked using pen 100.

Fig. lc is a schematic illustration of the use of the pen control unit for implementation of a writing pad. Figure Ic is a preferred embodiment of the present invention, incorporating both a screen 182 and a digital writing pad 184. Typically screen 182 can be part of a device such as a laptop computer 180, PC, personal digital assistant (PDA) or 3G cellular phone, for example. Digital pad 184 can be either physically connected or not physically connected to the device incorporating screen 182. Screen 182 shows an example of a handwritten transaction 190.

PCU 200 can be unconnected to the device incorporating screen 182, for example, CRT, TFT or CCD, and mounted at the top of clipboard 184, for example, in the paper holding spring-clamp mechanism 188. Preferably, there is a PCU 200 in both the device incorporating screen 182, as shown, and incorporated in spring-clamp mechanism 188 of clipboard 184. With two such PCU's 200, only the analog subsystem 202 portion of the embodiment is needed in clipboard 184, as described hereinbelow, with reference to fig. 2. infrared (IR) signals 196 from analog subsystem 202 are, therefore, transmitted to full PCU 200. Clipboard 184 typically holds a pad or sheet of writing surface 186, and is used as a digital writing pad. The writing surface may be paper or plastic or any other suitable material. Anything written on writing surface 186, appears simultaneously on screen 182. Use of pen 100 is shown in operation both with screen 182 and writing surface 186.

Block 198 is a separate depiction representing either screen 182 of device 180 dr writing surface 186 of clipboard 184. A detailed exemplary drawing application is shown in process with pen 100.

Fig. 2 is a schematic illustration of an inductive pen control unit 200 which has an analog processing subsystem 202 and a digital processing subsystem 232. The detailed sequence of operation is described hereinbelow in fig. 3. Inductive pen 100 has an inductive coil 205 that transmits an electromagnetic (e/m) wave. The position of the pen relative to a two-dimensional surface, such as the screen of a video monitor, is measured as a triangulated distance from two inductive receiver coils 210

and 220. The distance of the pen from each receiver coil is proportional to the amplitude of the received e/m wave, which has a frequency of less than 8 kh. The respective signals from receiver coils 210 and 220 are fed to amplifiers 212 and 222 respectively, and from there to low pass filters 214 and 224 respectively.

The signal from receiver coil 2 220 is also fed to a frame interference detector 230, which detects an interference spike associated with each raster frame of a video monitor. All of the above components of PCU 200 comprise analog signal processing subsystem 202.

Signals from low pass filter 1 214 and low pass filter 2 224 are fed to an analog-to-digital (A/D) converter 240, which is the first component of the digital processing subsystem 232. The digitized signal is then fed to a digital filter based on a fast Fourier transform (FFT) 250. The output of the digital filter 250 is processed by a smart statistical filter 260, which can analyze the frequency content of the signal to eliminate obvious noise components. A frame interference prognosis module 235 receives timing information from frame inerference detector 230, and thereby predicts the precise arrival time of succeeding monitor interference spikes. As a result, prognosis module 235 feeds back gain control signals to amplifier gain 1 212 and amplifier gain 2 222, so as to turn off the gain entirely so that the system is not "swamped"by the huge amplitude spike of the video monitor. The effects of such a spike, if not blocked, would be incurred beyond the length of time elapsed during the spike itself, because of the capacitative decay that would be required to be dissipated due to the enormous energy that would be built up. Finally, the useful information that is output from smart statistical filter 260 is processed by an X-Y calculation module 270, which using a triangulation algorithm to determine the precise X, Y coordintes of inductive pen 100.

Fig. 3 is a flow chart of the sequence of operation 300 of analog signal processing by the pen control unit, constructed and operated in accordance with the principles of the present invention. Input from inductive pen 100 are registered by receiving an analog signal from channel 1 305 and by receiving an analog signal from channel 2 310. If frame interference detector 230 detects impulse noise in blocks 325 and 330, then a timer delay is set until the end of the impulse in blocks 315 and 320.

The monitor impulse spike generates many frequencies over the entire frequency domain, so that simple filtering is of no avail. When the impulse has passed, the input signal is sent on to be processed by the analog/digtal converter 335. The next step involves finding the frequency bands in the signal, and applying a Discrete Fourier Transform to enable digital filtering 340, which is determined in conjunction with

statistical processing of the data 345 so as to eliminate obvious sources of noise interference. If it is determined that signal changes are needed 350, then information is sent to change the signal intensity in the analog system 355, which is done by adjusting gain 1 212 and gain 2 222. The software coeeficients are also updated 360 in the digital module for frame interference prognosis 235.

Subsequently, triangulation functions are set 365 by X-Y calculation module 270. External to transmission system 200, a general purpose microprocessor does a final check of the data 370, and sets the coordinates of the video monitor cursor position 375. General processing algorithms are also resident in the general purpose microprocessor.

The reference signal transmitted from pen 100 uses a proprietary amplitude and modulation scheme. This information is subsequently extracted from the received signal by PCU 200. The signal-processing unit of PCU 200 uses the amplitude of the signals from receiver coils 210 and 220 to calculate pen 100 position using an SLDS proprietary algorithm.

The pen transmits with a constant frequency. The modulation scheme is 50% amplitude modulation (AM) and a 50% duty cycle. The amplitude formula is given by: Y=Y1-Y2, where Y is the module amplitude, YI is full signal and Y2 is half-signal.

Since the noise amplitude is the same in YI and Y2, Y will comprise half a signal without noise.

The amplitude/distance formula is given by distance = a*b ( !/amplitude) *amplitude, where a, b and c are the coefficients of the x, y and z coordinate variables, respectively.

The triangulation formulas giving the X, Y location of pen 100 is calculated by the equations:

Y= I- ( (distance 2+base2-distance22)/2*distancel *base) 2 *distancel X= 1- ( (distancel2+base2-distance22)/2*distancel*base) 2 *distance2 where X and Y are the coordinates.

The system specifications are: Active Area 370 x 275 mm.

Resolution 0.3 mm.

Position Accuracy 0.5 mm.

Tracing velocity : On screen: >50 reports per second On desk: >100 reports per second Tilt of the pen (relatively to perpendicular) that will not result in a change of the displayed position-/+ 45 degrees.

PCU 200 may have a software driver installed, and it is available for Windows 95/98 and Windows NT Tm. The installation of the driver is fast and easy.

PCU 200, with pen 100, fully emulate the operation of a mouse pointing device, and can work with any standard program that uses a mouse.

Having described the invention with regard to certain specific embodiments, it is to be understood that the description is not meant as a limitation, since further modifications may now suggest themselves to those skilled in the art, and it is intended to cover such modifications as fall within the scope of the appended claims.