WO2007025382A1

WO2007025382A1 - Computer mouse pressure acquisition module

Info

Publication number: WO2007025382A1
Application number: PCT/CA2006/001435
Authority: WO
Inventors: Olivier Munger; Sébastien JOMPHE
Original assignee: Les Systèmes Nuax
Priority date: 2005-09-01
Filing date: 2006-09-01
Publication date: 2007-03-08

Abstract

A pressure acquisition module for a computer mouse having a button. The pressure acquisition module comprises a momentary switch, a pressure sensor, a sampler and a digital processor. The pressure sensor is operative to measure a pressure applied on the button of the computer mouse and to send a raw analog sensor signal. The sampler is operative to convert the raw analog sensor signal into a digital pressure signal. The digital processor is operative to filter out a parasitic oscillation from the digital pressure signal. The parasitic oscillation may be caused by the momentary switch being activated. The digital processor is further operative to output a corrected shaped pressure signal. In a second embodiment, there is a pressure acquisition module for a computer mouse having a button. The pressure acquisition module comprises a pressure sensor, a sampler, a transducer and a digital processor. The pressure sensor is operative to measure a pressure applied on the button of the computer mouse and to send a raw analog sensor signal. The sampler is operative to convert the raw analog sensor signal into a digital pressure signal. The transducer is operative to generate a momentary facsimile switch click. The digital processor is operative to generate a transducer signal in response to a pressure for generating a click.

Description

COMPUTER MOUSE PRESSURE ACQUISITION MODULE

FIELD OF THE INVENTION

The invention relates generally to data input devices but more particularly to a computer mouse having a module that detects a user's activation pressure.

BACKGROUND OF THE INVENTION

For the needs of visual artists, pressure sensitive tablets have been developed as an input device for a computer. Such tablets have the ability of translating all of the nuances of an artist gesture on the tablet by capturing data in 3D, that is depth is registered as pressure on the tablet. As a derivative to pressure sensitive tablets, there are pressure sensitive pens. In recent years, computer mice have also been developed that have pressure sensitive capabilities.

However, it is to be noted that the use of a computer mouse as an input device for graphic design applications is much different from that of a pressure sensitive tablet. While a computer mouse can offer pressure sensitive capabilities, the embodiment remains far from the intuitive pen design offered by graphical tablets. Indeed, graphical tablets were designed to emulate as much as possible the usage of traditional graphic tools such as pens and brushes. Using a graphical tablet requires only minimal adaptation since it offers an interface very similar to traditional drawing mediums.

Moreover, such differences are not specifically related to pressure capture capabilities: the simple act of drawing a line in a software application using a computer mouse requires a great amount of non-intuitive hand-eye coordination.

From another point of view, having a computer mouse equipped with pressure capture capabilities greatly differs from the graphical tablet domain since such an enhanced mouse can be used in a wider range of applications. The pressure sensitive mouse can be used as an input device for computer games by having the pressure variation controlling another axis of game-play, for example. As the graphical tablet appears more suitable for graphical applications, computer mice are better suited to gaming applications since they offer more intuitive controls. Beyond computer games, computer mice are known as the preferred general-purpose input device for computer applications. A pressure sensitive computer mouse could find uses in a wide variety of software applications; not being restricted to graphical applications as tablets implicitly are.

BACKGROUND ART

Human interfaces for computers have been used since the invention of the computer itself. Invented in 1964, the computer mouse has been commercialized in 1984. Nowadays, the computer mouse simply cannot be ignored when it comes to interfacing and controlling computers.

The computer mouse has been in constant evolution and even after years of operation, continues to integrate new functionalities. One objective in adding new features to such an input device is to provide the user with an improved control over the computer parameters and functions.

The idea of combining the commonly known mouse button, equipped with a momentary-On only On/Off switch, with a pressure sensor has been proposed by Brad A. Armstrong (US 6,198,473). The Armstrong mouse integrates a pressure-sensing mean which provides at least three readable states and enables the controls of functions like the scrolling speed. While such a system may be adequate for controlling functions which do not require a high level of precision and stability, it is not suited for high end applications like graphic design softwares or computer games. As a matter of fact, since the pressure variations are recorded via the same mechanical interface as the mouse button switch, the pressure measurements are distorted by the mechanical vibrations induced by the operation of the mouse button switch. When a user applies a downward pressure on a computer mouse button, the mouse button switch momentarily opposes a small inverse force. This opposition force usually varies as a function of the displacement from the steady state position due to the force coefficient of the spring embedded in the mechanical switch. Upon the reach of a mechanical threshold, the momentary switch closes and the opposed force is somewhat reduced in a brief instant. Such a rapid variation affects the pressure sensor which is mechanically connected to the mouse button and creates a measurable and unwanted distortion in the pressure capture.

Furthermore, oscillations of very small amplitude, induced by the vibration of the finger of the user, become important when the resolution of the measurement means increases. Such oscillations can be detected with a 7 bits analog-to-digital conversion, as proposed by Armstrong, and become very important when increasing the resolution to 8 bits and beyond. Those perturbations can be disregarded when controlling the scrolling speed and therefore, Armstrong's proposal does not include a mean to compensate for those sources of deterioration.

More recently, Kehlstadt et al. (US 6.879.316) proposed an invention similar to the one elaborated by Armstrong. It consists in integrating pressure- sensitive element in the buttons of a computer mouse for the sole purpose of controlling the scrolling, using the momentary switch of the assembly, and the scrolling speed, with the pressure sensitive element. The invention also proposes the use of the pressure related signal to control a zooming function or a back/forward function. The latter would be used to navigate through the pages of Web sites. As for Armstrong, Kehlstadt does not address any of the previously described perturbations for the reason that the targeted applications simply do not require a precision level which would necessitate a signal processing mean.

The functions described in prior arts require a signal with a minimal level of resolution. As will be understood by those skilled in the art, the usability of a variable scrolling speed function does not require a high level of resolution. Having 128 speed levels is suitable enough to provide the mouse user with an excellent control feeling. The same reasoning applies to the other above cited functions.

There is therefore a need for a high-resolution pressure acquisition module for a mouse that is not affected by parasitic oscillations.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a pressure acquisition module for a computer mouse that detects pressure applied by a user and which remains unaffected by parasitic oscillations.

It is another object of this invention to provide for an integrated pressure acquisition module which can be unobtrusively integrated within a mouse having a size and a shape similar to existing mice. In order to do so, the invention comprises a mechanical means to transfer applied force to pressure measuring means. The signal from the pressure measuring means is then digitized and processed by way of software to provide useful information for an end user in any given software application. The signal is treated in order to filter out any parasitic oscillations. In a preferred embodiment, the pressure measuring means is in the form of a sensor.

An aspect of the hereby proposed invention consists in the signal processing required to achieve a high precision monitoring of the applied pressure. The signal processing enables the mitigation of the distortions associated with the combining of the electromechanical switch of the standard mouse button to a pressure sensor. Signal processing provides the filtering capabilities required to compensate for all of the undesirable variations, or parasitic oscillations, in the measured pressure signal.

The signal processing means can also adjust the parameter of the analog- to-digital conversion in order to maximize the dynamic range of the converter. For example, a user typically applies a pressure which varies between two values which are not equal to the maximum and minimum of the readable range of pressure. The signal processing means can adjust the dynamic range of the converter to match the range of the applied pressure. Such an adaptation can be static, whereas the user adjusts the range in a configuration application, or dynamic, whereas the signal processing mean "learns" over a programmable amount of time the pressure habits of the user and adjusts the dynamic range of the converter automatically, falling back to a wider range whenever the user exceeds the last adjusted range.

With the use of a bidirectional mouse-computer communication link, such as that proposed by the protocol of the Universal Serial Bus (USB), the parameters of the pressure capture can be guided by the software application. For example, a graphic design software could require two different settings of the pressure sensitive apparatus to address the needs of two different graphic tools: the first requiring the maximum range of pressure measurement while the second would call for a reduced range with a higher sampling frequency. Such an adaptability may also be used to adjust the computer display so that the delay between the variations of the pressure and the display of those variations is somewhat compensated. Furthermore, the feeling of real-time control for the user is maximized by somewhat sacrificing the resolution of measurement.

More specifically, according to an aspect of the invention, there is provided a pressure acquisition module for a computer mouse having a button. The pressure acquisition module comprises a momentary switch, a pressure sensor, a sampler and a digital processor. The pressure sensor is operative to measure a pressure applied on the button of the computer mouse and to send a raw analog sensor signal. The sampler is operative to convert the raw analog sensor signal into a digital pressure signal. The digital processor is operative to filter out a parasitic oscillation from the digital pressure signal. The parasitic oscillation may be caused by the momentary switch being activated. The digital processor is further operative to output a corrected shaped pressure signal.

According to another aspect, there is provided a pressure acquisition module for a computer mouse having a button. The pressure acquisition module comprises a pressure sensor, a sampler, a transducer and a digital processor. The pressure sensor is operative to measure a pressure applied on the button of the computer mouse and to send a raw analog sensor signal. The sampler is operative to convert the raw analog sensor signal into a digital pressure signal. The transducer is operative to generate a facsimile of a momentary switch click. The digital processor is operative to generate a transducer signal in response to a pressure for generating a click. The digital filter is further operative to filter out a parasitic oscillation from the digital pressure signal and to output a corrected shaped pressure signal.

In both of the later aspects, the digital processor is operative to detect the parasitic oscillation and output an extrapolation of the digital pressure signal from a last known valid sample to an actual sample located after the parasitic oscillation. Alternatively, the digital processor is operative to detect the parasitic oscillation and start capturing the digital pressure signal from a digital pressure signal minimum following the parasitic oscillation. Another option is to have the digital processor operative to detect the parasitic oscillation and drop a number of samples substantially corresponding to the parasitic oscillation. Preferably, the digital processor detects the parasitic oscillation by monitoring an on/off signal from the momentary switch. Alternatively, the digital processor detects the parasitic oscillation by calculating an instantaneous gradient of the digital pressure signal. The number of samples may be fixed, configured by a user or adjusted by a selfmodifying algorithm. Preferably, the digital processor comprises a matched low-pass filter for filtering out high-frequency noise. More preferably, the digital processor further comprises a linearization algorithm for linearizing non-linearities in the digital pressure signal caused by the pressure sensor. Still more preferably, the linearization algorithm looks up a correspondence table to linearize the digital pressure signal.

In another aspect of the invention, there is provided a computer mouse comprising a pressure acquisition module as defined in any one of the previous embodiments. In still another aspect of the invention, there is provided a kit comprising a computer and a mouse as defined in any one of the previous embodiments.

The foregoing and other objects, features, and advantages of this invention will become more readily apparent from the following detailed description of a preferred embodiment with reference to the accompanying drawings, wherein the preferred embodiment of the invention is shown and described, by way of examples. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a top, partially cut-away view of a mouse according to an embodiment of the present invention.

Fig. 2 is a side, partially cut-away view of the mouse of Fig. 1.

Figs. 3a-3e are side views depicting a sequence of a clicking action on the pressure sensitive module of the mouse of Fig. 1.

Fig. 4 is a time graph representing the signal sent by the pressure acquisition module of Figs. 3a-e.

Fig. 5 is a block diagram of the circuit of the mouse of Fig. 1.

Fig. 6 is a top, partially cut-away view of another embodiment of a mouse according to another embodiment of the present invention.

Fig. 7 a-e are side views depicting a sequence of a clicking action on the pressure acquisition module of the mouse of Fig. 5.

Figs. 8 is a time graph representing the signal sent by the pressure acquisition module of Figs. 6a-e. Fig. 9 is an example of a time graph of the pressure applied on the mouse button according to an embodiment of the present invention.

Fig. 10 is an example of a graph of the resistance as a function of the pressure for a typical resistive pressure sensor according to an embodiment of the present invention.

Fig. 11 is a cut-away side view of a part of a mouse according to another embodiment of the present invention.

Fig. 12 is a block diagram of the circuit of the mouse of Fig. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring simultaneously to Figure 1 and Figure 2, a computer mouse 19, similar in many ways to computer mouse of the prior art, has button covers 1 having a button cover assembly 2, located on their underside and comprising a movement transfer member 9 and a pressure transfer module

10. The mouse 19 further includes a switch assembly 4 and a pressure acquisition module 5. The switch assembly 4 is made of a momentary switch

11 , having a moving part 12 and a static part 13. The pressure acquisition module 5 comprises a pressure sensor 14, an electrical interface 15, electrical wires 17 and electrical connection 16 to a PCB 18. The electrical connection 16 processes the signal for input into a computer (not shown).

Before any pressure or force is applied to any one button cover 1 equipped with the pressure sensor 14, the system is in a steady state as per Figure 3a and awaits user input. Figs. 3a-e show a linear sequence of action detailing the interaction between the mouse button 1 , the movement transfer member 9, the pressure transfer module 10, the momentary switch 12, and the pressure sensor 14.

Figure 4 is a time graph with instants 36, 37, 38, 39 and 40, showing the electrical output of both the momentary switch 11 and the pressure sensor 14. W will now refer simultaneously to Figures 3a-e and 4. When the system is idle as in Figure 3a, the momentary switch 11 is OFF and the pressure sensor 14 outputs the minimal possible value. This period corresponds to instant 36 on the time graph of Figure 4. In Figure 3b, the user begins to apply a downward force on one of the button covers 1. When the movement transfer member 9 makes contact with the moving part 12 of the momentary switch 11 , a space 28 remains between the pressure sensor 14 and the pressure transfer module 10. This space 28, which can be null, is set by the mouse designer to compensate for any mechanical displacement required to activate the momentary switch 11. This ensures that the pressure sensor 14 will not be activated until the momentary switch 11 is closed, that is to say until the mouse button 1 has "clicked". This means that, as shown at instant 37, neither the mouse button 1 nor the pressure sensor 14 are activated.

In Figure 3c, following the applied force, the movement of the mouse button 1 continues beyond the mechanical threshold of the momentary switch 11 and closes an electrical circuit. The moving part 12 of the momentary switch 11 is compressed in the ON position and the user hears and feels the well known "click". The movement transfer member 9 is then in direct contact with the pressure sensor 14. At this instant 38, the momentary switch 11 changes from OFF to ON. Between instants 38 and 40 in Figure 4, any variation in the pressure applied on the mouse button 1 will be detected by the pressure sensor 14. The pressure transfer module 10 stays in contact with the pressure sensor 14 while the user varies the amount of pressure applied to the mouse button 1. Depending on the material from which the pressure sensor 14 is made, it may either be soft, in which case the user would feel a slight movement of the mouse button 1 , or hard, which would not yield any tactile feedback. Any movement beyond the mechanical threshold cannot affect the momentary switch 11 since its moving parts allows for a wider amplitude of displacement than what is required to activate it. The moving parts will only get further down and inside the static part 13 of the momentary switch 11.

Figure 4 shows that between instants 38 and 39, the output of the pressure sensor 14 is proportional to the force applied on the mouse button 1. Notwithstanding the relationship between the electrical signal measured from the pressure sensor 14 and the applied pressure, the electrical output is not directly proportional to the downward force exerted by the movement transfer member 9 input and a signal processing algorithm is required to compensate for any non-linearities thereby introduced in the system. The pressure acquisition module 5 of the mouse 19 is totally transparent from the user's perspective. The user can use any software applications which does not required pressure sensitivity as easily as with a standard mouse. An application using the pressure sensitivity functionality will detect the enhanced computer mouse 19 and read the measured pressure values in addition to button activations but will also allow a mouse of the prior art to work as it should by only interpreting the signal from its buttons as simple On/Off signals.

Figure 5 depicts a block diagram in which the application of an actuation force on the mouse button 101 enables the system to switch from a passive state to an active state, and reversely from the active state to the passive state when the actuation force becomes null. In this embodiment, the processes associated with the mouse button switch 102 and the pressure sensor 103 respectively are achieved independently until the transmission of the information to a computer with the mouse-computer communication link 122. The computer application 127 uses the digital pressure code 119 without having the mouse button switch 102 to be activated. Although the following requirement may vary from a computer application to another, both mechanical and electronic integration should allow an extended active state for the monitoring of the pressure, or force, variations while the activation of the mouse button switch 102 is maintained. This enables, for example, to track the pressure variations while the computer mouse is being moved from a set of X Y coordinates to another, such manipulation being known as dragging. Before any pressure or force is applied on the mouse button 101 , the system is in a passive state and waits for user inputs.

The mouse button switch 102 transmits either an ON or an OFF signal 104, whichever is associated with the passive state by the system. The on/off signal 104 is converted by sampling 106 into a digital on/off signal 108 and then processed by a mouse control system 110 in order to be transmitted via a mouse data link 112 to a mouse-computer communication link 122. In the passive state, the pressure sensor 103 transmits a raw sensor signal 105 of a value associated with the passive state by the system. The raw sensor signal 105 can be, for example, of the following nature: electrical potential, electrical current, inductance, capacitance, conductance, electrical resistance, light beam, laser beam, magnetic field, electric field, electromagnetic field, etc. During the passive state, the value of the raw sensor signal 105 may correspond to the force applied on the mouse button 101 by the laying of a finger on the computer mouse. Such value may also be equal to zero. An electronic driver 107 processes the raw sensor signal 105 in order to convert its nature to an electrical pressure signal 109. The electrical pressure signal 109 is then processed by analog scaling 111 to adjust its variation range in order to maximize the dynamic range of the analog to digital conversion. The resulting scaled pressure signal 113 is converted by sampling 114 into a digital pressure signal 115 which is computed by a digital processor 116 to be filtered and linearized to compensate for any non-linearities such as, for example, those introduced by the pressure sensor 103, the mouse button switch 102 or the electronic driver 107. The digital processing could be done at different levels: analog, digital or software. However, processing the digital pressure signal 115 is preferred. The resulting shaped pressure signal 117 is submitted to an encoding means 118 to obtain a digital pressure code 119. The pressure acquisition module control system 120 transmits the digital pressure code 119 via the pressure acquisition module data link 121 to a mouse-computer communication link 122. The mouse-computer communication link 122 communicates the information relative to the mouse button switch 102 and to the pressure sensor 103 to the mouse software driver 123. Computer application 127 such as, for example, a computer operation system, a computer game, a computer graphic design application, etc. may have access to the information relative to the X Y coordinates 124, the buttons on/off status 125 and the pressure status 126 by transacting with the mouse software driver 123. When the mouse button 101 is depressed, the mouse button switch 102 is activated and it transmits an on/off signal 104, whichever is associated with the active state but usually of the opposite value than the value associated with the passive state. The on/off signal 104 is converted by sampling 106 into a digital on/off signal 108 and then processed by a mouse control system 110 in order to be transmitted via a mouse data link 112 to the mouse-computer communication link 122. The mouse-computer communication link 122 communicates the information relative to the mouse button switch 102 to the mouse software driver 123. The pressure sensor 103 simultaneously transforms the increased pressure into a raw sensor signal 105. The raw sensor signal 105 corresponds to the actuation force applied by the user on the mouse button 101 to activate the mouse button switch 102 and/or the pressure sensor 103. The value of the raw sensor signal 105 varies according to the actuation force applied by the user on the mouse button 101. An electronic driver 107 processes the raw sensor signal 105 in order to convert its nature to an electrical pressure signal 109. The electrical pressure signal 109 is then processed by analog scaling 111 to adjust its variation range in order to maximize the dynamic range of the analog to digital conversion. The resulting scaled pressure signal 113 is converted by sampling 114 into a digital pressure signal 115 which can be computed by a digital processor 116. The resulting shaped pressure signal 117 is submitted to an encoding means 118 to obtain a digital pressure code 119. The pressure acquisition module control system 120 transmits the digital pressure code 119 via the pressure acquisition module data link 121 to a mouse-computer communication link 122. Computer applications 127 such as a computer operation system, a computer game, a computer graphic design application, etc. have access to the information relative to the X Y coordinates 124, the buttons on/off status 125 and the pressure status 126 by transacting with the mouse software driver 123.

The digital processor 116 uses an algorithm that enables the mitigation of the parasitic oscillations associated with the combination of the electromechanical mouse button switch 102 of the standard mouse button 101 to the pressure sensor 103 as well as other parasitic oscillations such as those caused by a slight variation of the pressure of the user's finger resting on the mouse button or by the displacement of the mouse on its resting surface.

Three types of signal processing are required in order to reshape the digital pressure signal 115 to render it usable by a software application. All of the digital pressure signal 115 processing can be computed at different points in the system: inside the computer mouse (firmware), by the mouse software driver or by the software application.

The first process addresses the effect of the electromechanical momentary mouse button switch 102 of the mouse button 101. Such component induces a short burst of erroneous pressure readouts. Reference is now simultaneously made to Figures 5 and 9. Figure 9 illustrates the monitoring of the pressure applied on the mouse button 101 as a function of time. The pressure level ranges from 0 to 1023 levels (bits). The erroneous pressure reading period 202 is caused by the rapid variation of the mechanical resistance of the moving part of the momentary mouse button switch 102. One of the tasks of the signal processing is to identify and minimize or suppress the erroneous pressure period due specifically to this side-effect of the mechanical mouse button switch 102 on the pressure sensor 103. Such filter is called a Click-cut filter since it detects the action of clicking and removes its ill effects on the digital pressure signal 115. A plurality of strategies can be used to realize a Click-cut filter.

A first strategy is to detect the parasitic oscillation and then output an extrapolation of the digital pressure signal 115 from the last known good sample until convergence with the real digital pressure signal 115.

A second strategy is to detect the parasitic oscillation and then identify the next digital pressure signal minimum 203 and start the capture from this point. A third strategy consists in detecting the parasitic oscillation and then dropping a pre-defined number of samples. The number of samples may be fixed, or configured by the user, or adjusted by a self-learning (and/or selfmodifying) algorithm. The detection of the parasitic oscillation is achieved either by monitoring the signal of the mouse button momentary switch 102, or by calculating the instantaneous gradient of the digital pressure signal 115. Such detection means is then re-triggered either by the mouse button momentary switch 102 returning to its unclicked state, or by reading a digital pressure signal 115 lower than a specified threshold. Such a threshold may be fixed, either configured by the user, or adjusted by a self-learning algorithm.

The second process addresses the problems of noise which adds higher frequency components to the raw pressure signal 105. Such noise is of lesser amplitude and does not hinder a lower resolution system. Using a higher resolution analog-to-digital converter picks up noise 201 thereby affecting the overall quality of the signal. The use of a matched low-pass filter minimizes the effect of the noise. Such a filter offers more than one mode of operation in order to adapt the system as a function of the user's preferences (and/or habits) or to meet requirements specific to software applications or to the operating system. A first mode of operation is to use specific parameters to configure the filter of the digital processor 116. Such parameters may be fixed, adjusted by the user or specified by a software application. A second mode of operation is to use a self-learning algorithm in order to easily and rapidly adapt the parameters of the filter to achieve an optimal filtering. A third mode of operation is to stop filtering the digital pressure signal 115 by putting the filter in a standby state.

The third process addresses the problems of the non-linearities introduced by the pressure sensor 103 and/or by the electromechanical assembly. Typical pressure sensors present a partially complete, or complete, non- linear operation range. Figure 10 presents an example of a "Pressure vs. Resistance" plot for a typical resistive pressure sensor. The high proportion of non-linearities of the response of such sensors requires a linearization algorithm. To linearize the digital pressure signal 115, the digital processor 116 refers to a correspondence table from the manufacturer of the pressure sensor 103 and outputs the corrected shaped pressure signal 117.

The digital processor 116 can also adjust the parameter of the analog-to- digital conversion in order to maximize the dynamic range of the encoding means 118. For example, a user typically applies a pressure which varies between two values which are not equal to the maximum and minimum of the readable range of pressure. The digital processor 116 adjusts the dynamic range of the encoding means 118 to match the range of the applied pressure. Such an adaptation can be static, whereas the user adjusts the range in a configuration application, or dynamic, whereas the digital processor 116 "learns" over a programmable amount of time the pressure habits of the user and adjusts the dynamic range of the encoding means 118 automatically, falling back to a wider range whenever the user exceeds the last adjusted range.

With the use of a bidirectional mouse-computer communication link, such as proposed by the protocol of the Universal Serial Bus (USB), the parameters of the pressure capture can be guided by the software application. For example, a graphic design software may require two different settings of the pressure sensitive apparatus to address the needs of two different graphic tools: the first requires the maximum range of pressure measurement while the second calls for a reduced range with a higher sampling frequency. Such an adaptability is also used to adjust the computer display so that the delay between the variations of the pressure and the display of those variations is somewhat compensated. Furthermore, the feeling of real-time control for the user is maximized by somewhat sacrificing the resolution of measurement. Because of it capacity to deal with high resolution samplings of the pressure signal, the present invention is very well suited for use for graphical arts. For example, the weight of a line may be directly proportional to the pressure applied on the mouse button. Also, the color spectrum could be linked to the pressure applied on the button (i.e. from reds to violets). Alternatively, the present invention could be used with computer games where the pressure could be directly proportional to a parameter such as the strength with which a club is swung in a golf game.

Figure 6 depicts another embodiment of the invention that places the momentary switch 11 directly under the pressure sensor 14 so that only the movement transfer member 9 is required. This is known as the "serial" mode as opposed to the "parallel" mode of the previous embodiment.

Reference will now be made simultaneously to Figures 7a-e and 8. Before any pressure or force is applied to any one button equipped with a pressure acquisition module 5, the system is in a steady state (Fig. 7a) and awaits user input. Figure 8 is a time graph, that shows the electrical output of both the standard momentary switch 11 (straight line) and the pressure sensor 14 (dotted line). When the system is idle (Fig. 7a), the switch is OFF and the pressure sensor outputs the minimal possible value. This period correspond to instant 74 on the time based analysis. The user applies a downward force on the mouse button 1 and thus the mouse button 1 , the movement transfer member 9 and the pressure sensor 14 move downward accordingly. As shown by instant 75, the outputs of both the moving part 12 of the momentary switch 11 and the pressure sensor 14 remain unchanged until they contact (Fig. 7b). Since the pressure sensor 14 is a moving part connected to a non-moving part (the PCB 18), its electrical wires 17 have to be flexible. In Figure 7c, the user has not stopped applying a downward pressure as movement transfer module 9, the pressure sensor 14 and the moving part 12 of the momentary switch 11 move further down. The moving part 12 of the momentary switch 11 exerts an upward force which opposes the downward movement of the pressure sensor 14. This force induces a pressure on the pressure sensor 14 whose output then begins to increase. Figure 8 shows, between instants 76 and 77, that the output of the pressure sensor 14 (dotted line) increases while the output of the momentary switch 11 (straight line) remains unchanged. This divergence between the two outputs could to be compensated by hardware or software processing. Indeed, it might not be desirable to use the pressure information while the button 1 is still non activated (i.e. the button has not clicked yet). From this instant 76, any variation in the pressure applied on the mouse button 1 will be detected by the pressure sensor 14. Depending on the material from which the pressure sensor 14 is fabricated, it may either be soft, in which case the user would feel a slight movement of the mouse button 1 , or hard, which would not yield any tactile feedback. At Figure 7d, the force exerted by the user rises beyond the mechanical threshold of the momentary switch 11 and closes the electrical circuit. The momentary switch 11 is then in the ON position and the user hears and feels the well known "click". Figure 8 shows, at instant 77, the momentary switch's output (straight line) going from OFF to ON. However, since the pressure sensor 14 is used in combination (serial configuration) with the movement transfer member 9 to push on the momentary switch 11 , the clicking of the momentary switch 11 results in a fast variation in the pressure reading of the pressure sensor 14 as the elastic tension built up inside the momentary switch 11 is released as a result of the click. Figure 8 shows this as a brief "release" in pressure at instant 72. Again, this non linearity could be removed with hardware or software processing. Any movement beyond the mechanical threshold of the momentary switch 11 cannot affect the momentary switch 11 since its moving part 12 allows for wider amplitude of displacement than what is required to activate it. The moving part 12 will only get further down and inside the static part 13. Figure 8 shows that between instants 76 and 78, the output of the pressure sensor 14 is proportional to the force applied on the mouse button 1. Notwithstanding the relationship between the electrical signal measured from the pressure sensor 14 and the applied pressure, the electrical output is not directly proportional to the downward force exerted by the user's input and a signal processing algorithm is required to compensate for any non-linearities thereby introduced in the system. As for a standard mouse, not equipped with pressure acquisition module 5, the button release is achieved by reducing the amount of pressure applied on the button 1 to a null value. The user simply removes his finger from the mouse button 1 and the system returns to a steady state, Figure 7e, instant 78 equivalent to Figure 7a, instant 74, awaiting a new activation cycle. Figure 11 depicts another embodiment of the invention that does without the momentary switch. The mouse button 501 acts directly on the pressure sensor 502 and uses a transducer 503 (shown in Figure 12) that can be either a speaker or a piezoelectric device for generating a facsimile of a momentary switch click that can be a sound or a vibration or a combination of both.

Figure 12 depicts a block diagram of the embodiment depicted in Figure 11. The pressure sensor 502 mechanically interacts with the mouse button 501. The application of an actuation force on the mouse button 501 enables the system to switch from a passive state to an active state, and reversely from the active state to the passive state when the actuation force becomes null. In this embodiment, the mouse button switch function is emulated by the pressure sensor 502. The digital processor 516 uses a threshold in order to discriminate a « mouse button click » from the actuation force variation. That is to say that when the computer mouse user has depressed the mouse button 501 with enough force, the digital processor 516 outputs a digital on/off signal 528 equivalent to a « mouse button click » to the mouse control system 522 and to the transducer 503. The threshold could be, without being limited to, a constant value known by the system or a user defined value, adjusted in a computer application 527. Moreover, the computer application 527 could generate an audio feedback, hearable by the computer mouse user through the computer's audio system or by audio module directly embedded inside the computer mouse, which indicates the completion of a « mouse button click ». In this embodiment, the computer application 527 can use the pressure status 526 independently from a mouse button switch activation since both information, pressure status 526 and buttons on/off status 525 are generated by the same digital processor 516. While this embodiment is shown with mouse control system 522, it could be applied with any other control means.

The present invention has been described with regard to preferred embodiments. The description as much as the drawings were intended to help the understanding of the invention, rather than to limit its scope. It will be apparent to one skilled in the art that various modifications may be made to the invention without departing from the scope of the invention as described herein, and such modifications are intended to be covered by the present description.

Claims

1. A pressure acquisition module for a computer mouse having a button, the pressure acquisition module comprising: a momentary switch; a pressure sensor operative to measure a pressure applied on the button of the computer mouse and to send a raw analog sensor signal; a sampler for converting said raw analog sensor signal into a digital pressure signal; a digital processor for filtering out a parasitic oscillation from said digital pressure signal, said parasitic oscillation being caused by said momentary switch being activated, said digital processor being operative to output a corrected shaped pressure signal.

2. A pressure acquisition module as defined in claim 1 wherein said digital processor is operative to detect said parasitic oscillation and output an extrapolation of said digital pressure signal from a last known valid sample to an actual sample located after said parasitic oscillation.

3. A pressure acquisition module as defined in claim 1 wherein said digital processor is operative to detect said parasitic oscillation and start capturing said digital pressure signal from a digital pressure signal minimum following said parasitic oscillation.

4. A pressure acquisition module as defined in claim 1 wherein said digital processor is operative to detect said parasitic oscillation and drop a number of samples substantially corresponding to said parasitic oscillation.

5. A pressure acquisition module as defined in any one of claims 2 to 4 wherein said digital processor detects said parasitic oscillation by monitoring an on/off signal from said momentary switch.

6. A pressure acquisition module as defined in any one of claims 2 to 4 wherein said digital processor detects said parasitic oscillation by calculating an instantaneous gradient of said digital pressure signal.

7. A pressure acquisition module as defined in claim 4 wherein said number of samples is fixed.

8. A pressure acquisition module as defined in claim 4 wherein said number of samples is configured by a user.

9. A pressure acquisition module as defined in claim 4 wherein said number of samples is adjusted by a self-modifying algorithm.

10. A pressure acquisition module as defined in claim 1 wherein said digital processor further comprises a matched low-pass filter for filtering out high-frequency noise.

11. A pressure acquisition module as defined in claim 10 wherein said digital processor further comprises a linearization algorithm for linearizing non-linearities in said digital pressure signal caused by said pressure sensor.

12. A pressure acquisition module as defined in claim 11 wherein said linearization algorithm looks up a correspondence table to linearize said digital pressure signal.

13. A computer mouse comprising a pressure acquisition module as defined in claim 1.

14. A kit comprising a computer and a mouse as defined in claim 13.

15. A pressure acquisition module for a computer mouse having a button, the pressure acquisition module comprising: a pressure sensor operative to measure a pressure applied on the button of the computer mouse and to send a raw analog sensor signal; a sampler for converting said raw analog sensor signal into a digital pressure signal; a transducer for generating a facsimile of a momentary switch click; and a digital processor for generating a transducer signal fed to said transducer in response to a pressure for generating a click.

16. A pressure acquisition module as defined in claim 15 wherein said digital filter is further operative to filter out a parasitic oscillation from said digital pressure signal, said digital processor being operative to output a corrected shaped pressure signal

17. A pressure acquisition module as defined in claim 16 wherein said digital processor is operative to detect said parasitic oscillation and output an extrapolation of said digital pressure signal from a last known valid sample to an actual sample located after said parasitic oscillation.

18. A pressure acquisition module as defined in claim 16 wherein said digital processor is operative to detect said parasitic oscillation and start capturing said digital pressure signal from a digital pressure signal minimum following said parasitic oscillation.

19. A pressure acquisition module as defined in claim 16 wherein said digital processor is operative to detect said parasitic oscillation and drop a number of samples substantially corresponding to said parasitic oscillation.

20. A pressure acquisition module as defined in any one of claims 17 to 19 wherein said digital processor detects said parasitic oscillation by monitoring an on/off signal from said momentary switch.

21. A pressure acquisition module as defined in any one of claims 17 to 19 wherein said digital processor detects said parasitic oscillation by calculating an instantaneous gradient of said digital pressure signal.

22. A pressure acquisition module as defined in claim 19 wherein said number of samples is fixed.

23. A pressure acquisition module as defined in claim 19 wherein said number of samples is configured by a user.

24. A pressure acquisition module as defined in claim 19 wherein said number of samples is adjusted by a self-modifying algorithm.

25. A pressure acquisition module as defined in claim 16 wherein said digital processor further comprises a matched low-pass filter for filtering out high-frequency noise.

26. A pressure acquisition module as defined in claim 25 wherein said digital processor further comprises a linearization algorithm for linearizing non-linearities in said digital pressure signal caused by said pressure sensor.

27. A pressure acquisition module as defined in claim 26 wherein said linearization algorithm looks up a correspondence table to linearize said digital pressure signal.

28. A computer mouse comprising a pressure acquisition module as defined in claim 16.

29. A kit comprising a computer and a mouse as defined in claim 28.