FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to detection with a capacitive based digitizer sensor and, more particularly, but not exclusively, to noise suppression methods for detection with a capacitive based digitizer sensor.

Capacitive based digitizer sensors are known to be used in various human interface devices. Typically, capacitive based digitizer sensors use human body capacitance such as from a fingertip as input. Some capacitive based digitizer sensors are integrated with a display screen. The detected position of a finger or another body part provides input to a computing device associated with the display, and is interpreted by the computing device as commands or input to commands. Examples of such devices include Personal Computers (PCs) including tablet PCs, pen enabled laptop computers, personal digital assistants (PDAs) or any hand held devices such as digital audio players and mobile phones.

Capacitive based digitizer sensors are subject to picking up noise from the surrounding environment for example due to magnetic and/or electric fields generated by LCD screen, fluorescent lighting, power suppliers and/or other sources.

U.S. Pat. No. 5,691,512 entitled “Position Transducer, and method for eliminating noise therefore,” the content of which is incorporated herein by reference, describes a position transducer, and a noise elimination method for eliminating a noise component included in a received signal of the position transducer. The position transducer is provided with a subtraction means which extracts an amplitude level corresponding to the signal developed in the loop coil resulting only from the electromagnetic interaction, for each loop coil, by subtracting a noise level obtained from a signal received when a transmission means interrupts transmission, from a signal received when the transmission means carries out transmission.

U.S. Pat. No. 7,843,439, entitled “Touch Detection for a Digitizer” assigned to N-Trig Ltd., the contents of which is incorporated herein by reference, describes a digitizing system including a transparent digitizer sensor overlaid on a flat panel display (FPD). The transparent digitizing sensor includes a matrix of vertical and horizontal conductive lines for sensing location of one or more of a stylus and/or a finger. Input to the digitizer sensor includes one or more of electromagnetic (EM) transmission from the stylus touching the sensing surface and capacitive coupling due to a conductive object such as a finger touching the screen. Location of a finger is detected by triggering one conductive line at a time along one axis of the grid and detecting output in response to each signal applied from a plurality of conductive lines along the other axis. A tabulation of capacitance values detected at each junction while no finger or stylus is present is stored and used to correct readings at each conductor during detection. The digitizing system is capable of detecting position of simultaneous occurrences of multiple styluses and/or multiple finger touches.

U.S. Patent Application Publication No. 20130027361 entitled “Noise reduction in digitizer system,” assigned to N-Trig Ltd., the content of which is incorporated herein by reference, describes a method for noise reduction in a digitizer that is operative to detect both an electromagnetic signal as from a stylus and finger touch. The method includes determining a location of a stylus with a known frequency of emission over a first sampling period, sampling output from a plurality of detecting elements over a second sampling period, identifying detecting elements with sampled output in the second sampling period above a defined threshold in a selected frequency, the selected frequency being close to but different than the known frequency of the stylus, selecting as a candidate carrier of mere noise a detecting element from the detecting elements identified that is spaced away from the determined location of the stylus, and reducing values of output sampled over the second sampling period from at least one other detecting element, in accordance with the output sampled over the second sampling period from the detecting element selected as the candidate carrier of mere noise.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention there is provided a method for detecting noise signals picked up by a capacitive based digitizer sensor during fingertip detection or the like, and using the detected noise signal to suppress a noise component in a concurrently sampled second signal including information for the fingertip detection or the like, e.g. a detection signal. According to some embodiments of the present invention, the noise signal is detected on a same conductive line as the concurrently sampled second signal. According to some embodiments of the present invention, time domain multiplexing is used to alternate between sampling the noise signal and the second signal.

According to an aspect of some embodiments of the present invention there is provided a method for reducing the number of iterations required for scanning a capacitive based digitizer sensor that is operated for mutual capacitive sensing. According to some embodiments of the present invention, a plurality of conductive lines are simultaneously triggered with sections of triggering and/or drive pulses that are interlaced so that only one drive pulse from the plurality excites the digitizer sensor at any given point in time. According to some embodiments of the present invention, time domain multiplexing is used to obtain output responsive to triggering each of the plurality of conductive lines. Optionally, at least a portion of the plurality of conductive lines is simultaneously triggered with different frequency signals and frequency domain multiplexing is applied to separate output responsive to the different frequency signals.

An aspect of some embodiments of the present invention provides for a method for capacitive based detection with a digitizer sensor including a plurality of conductive elements that are capacitively coupled, the method comprising: generating a drive signal including transient sections separated in time by flat sections; providing the drive signal generated to at least one conductive element of the digitizer sensor; and sampling outputs transferred to a second conductive element that is capacitively coupled to the at least one conductive element in response to providing the signal generated to the at least one conductive element, wherein the sampling events of the sampling are timed to take place both in response to the transient sections of the drive signal and to the flat sections of the drive signal.

Optionally, the method includes using outputs sampled in response to the flat sections to suppress noise in outputs sampled in response to the transient sections.

Optionally, the method includes subtracting amplitudes of outputs sampled in response to the flat sections from amplitudes of outputs sampled in response to the transient sections of the drive signal.

Optionally, the subtracting is performed between pairs of contiguous outputs.

Optionally, the noise is a signal emitted by a stylus interacting with the digitizer sensor.

Optionally, the method includes timing the sampling events occurring in response to the flat sections to occur after responses of the second conductive element to previous transient sections of the drive signal have faded.

Optionally, the method includes timing the sampling events occurring in response to the flat sections to occur substantially at an onset of the transient sections of the drive signal.

Optionally, the method includes timing the sampling events of the sampling to alternate between occurring in response to the transient sections of the drive signal and occurring in response to the flat sections of the drive signal.

Optionally, the method includes timing the sampling events of the sampling to alternate between occurring twice in response to each of a plurality of the transient sections of the drive signal and occurring once in response to each of a plurality of the flat sections of the drive signal.

Optionally, durations of the flat sections in the drive signal are defined to be irregular.

Optionally, the drive signal is an oscillating signal that is periodically interrupted by a flat signal.

Optionally, the oscillating signal is a sinusoidal signal with frequency lower than a frequency of occurrences of the flat sections.

Optionally, the method includes generating a plurality of drive signals, wherein each drive signal includes transient sections separated in time by flat sections; and applying time domain multiplexing for sampling the outputs in response the plurality of drive signals on the second conductive element.

Optionally, each of the plurality of drive signals includes an oscillating signal that is periodically interrupted by a flat signal.

Optionally, a same oscillating frequency of the oscillating signal is use to generate each the drive signals.

Optionally, at least two drive signals have an oscillating signal with different oscillating frequency.

Optionally, the digitizer sensor includes a first set of parallel conductive lines and second set of parallel conductive lines, the first and second set of conductive lines arranged in a grid pattern.

Optionally, the at least one conductive element is a conductive line from the first set of parallel conductive lines and second conductive element is a conductive line from the second set of parallel conductive lines.

Optionally, the method includes sampling output on all the conductive lines from the second set of parallel conductive lines in response to providing the drive signal.

As aspect of some embodiments of the present invention provides a method for capacitive based detection with a digitizer sensor including a plurality of conductive elements that are capacitively coupled, the method comprising: generating a plurality of drive signals, wherein each drive signal of the plurality of drive signals includes an oscillating signal that is intermittently interrupted by flat segments; simultaneously providing the plurality of drive signals to a plurality of conductive elements, wherein each drive signal of the plurality is provided to a different conductive element of the plurality of conductive elements; and applying time division multiplexing for sampling outputs on a second conductive element in response to transient periods of each of the plurality of drive signals.

Optionally, the oscillating frequency of the oscillating signals of each of the drive signals is the same.

Optionally, the oscillating signal includes more than one oscillating frequency.

Optionally, the oscillating frequency of at least two oscillating signals are orthogonal frequencies.

Optionally, the method includes applying frequency domain multiplexing for sampling outputs on the second conductive element in response to transient periods of the at least two drive signals occurring simultaneously.

Optionally, the digitizer sensor includes a first set of parallel conductive lines and second set of parallel conductive lines, the first and second set of conductive lines arranged in a grid pattern.

Optionally, the plurality of conductive elements are a plurality of conductive lines from the first set of parallel conductive lines and the second conductive element is a conductive line from the second set of parallel conductive lines.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

