Classifications

• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
  • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
  • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
  • G06V40/12—Fingerprints or palmprints
  • G06V40/13—Sensors therefor
  • G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F21/00—Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
  • G06F21/30—Authentication, i.e. establishing the identity or authorisation of security principals
  • G06F21/31—User authentication
  • G06F21/32—User authentication using biometric data, e.g. fingerprints, iris scans or voiceprints
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
  • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
  • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
  • G06V40/12—Fingerprints or palmprints
  • G06V40/13—Sensors therefor
  • G06V40/1329—Protecting the fingerprint sensor against damage caused by the finger

Definitions

• the invention is generally related to electronic sensing devices, and, more particularly, to sensors for sensing objects located near or about the sensor.
• sensors for sensing objects at a given location.
• Such sensors are configured to sense electronic characteristics of an object in order to sense presence of an object near or about the sensor, physical characteristics of the object, shapes, textures on surfaces of an object, material composition, biological information, and other features and characteristics of an object being sensed.
• Sensors may be configured to passively detect characteristics of an object, by measuring such as temperature, weight, or various emissions such as photonic, magnetic or atomic, of an object in close proximity or contact with the sensor, or other characteristic.
• An example of this is a non-contact infrared thermometer that detects the black body radiation spectra emitted from an object, from which its temperature can be computed.
• Other sensors work by directly exciting an object with a stimulus such as voltage or current, then using the resultant signal to determine the physical or electrical characteristics of an object.
• a stimulus such as voltage or current
• An example of this is a fluid detector consisting of two terminals, one that excites the medium with a voltage source, while the second measures the current flow to determine the presence of a conductive fluid such as water.
• a two dimensional array of impedance may be created by moving a line sensing array over the surface of an object and then doing a line by line reconstruction of a two dimensional image like a fax machine does.
• An example of this is a swiped capacitive fingerprint sensor that measures differences in capacitance between fingerprint ridges and valleys as a finger is dragged across it. Such sensors reconstruct a two dimensional fingerprint image after the fact using individual line information.
• a simpler way to obtain a two dimensional image is to create a two dimensional sensing array.
• Such sensors however can be prohibitive in cost due to the large number of sensing points needed in the array.
• An example of this is a two dimensional capacitive fingerprint sensor. A number of these are currently manufactured but use 150mm 2 or more of silicon area and are therefore cost prohibitive for many applications.
• biometric sensors for measuring biological features and characteristics of people such as fingerprints
• medical applications such as medical monitoring devices, fluid measuring monitors, and many other sensor applications.
• the sensing elements of the various devices are connected to a processor configured to process object information and to enable interpretations for object features and characteristics.
• Fingerprint sensors for example, have been in existence for many years and used in many environments to verify identification, to provide access to restricted areas and information, and many other uses.
• These placement sensors may be configured to sense objects placed near or about the sensor, such as a fingerprint placement sensor that is configured to capture a full image of a fingerprint from a user's finger and compare the captured image with a stored image for authentication.
• sensors may be configured to sense the dynamic movement of an object about the sensor, such as a fingerprint swipe sensor that captures partial images of a fingerprint, reconstructs the fingerprint image, and compares the captured image to a stored image for authentication.
• the placement sensor a two-dimensional grid of sensors that senses a fingerprint image from a user's fingerprint surface all at once, was the obvious choice, and its many designs have become standard in most applications. Once the fingerprint image is sensed and
• fingerprint sensors have been finding their way into portable devices such as laptop computers, hand held devices, cellular telephones, and other devices. Though accuracy and reliability are still important, cost of the system components is very important.
• the conventional placement sensors were and still are very expensive for one primary reason: they all used silicon sensor surfaces. These surfaces are very expensive, as the silicon material is as expensive as the material to make a computer chip. Computer chips, of course, have become smaller over the years to reduce their cost and improve their performance. The reason the fingerprint silicon could not be made smaller: they need to remain the size of the average fingerprint, and the requirement for full scanning of the users' fingerprints simply cannot be compromised. The full print is required for adequate security in authentication.
• swipe sensors need much less silicon, only enough to configure a line sensor with an array of pixel sensors. The width is still fixed based on the average fingerprint width, but the depth is substantially smaller compared to the placement sensor.
• Some swipe sensors are capacitive sensors, where capacitance of the fingerprint surface is measured and recorded line by line.
• the first generation sensors were constructed with direct current (DC) switched capacitor technology (for example US Patent No. 6,011,859).
• DC direct current
• This approach required using two plates per pixel forming a capacitor between them, allowing the local presence of a finger ridge to change the value of that capacitor relative to air.
• These DC capacitive configurations took images from the fingerprint surface, and did not penetrate below the finger surface. Thus, they were easy to spoof, or fake a fingerprint with different deceptive techniques, and they also had poor performance when a user had dry fingers.
• RF (Radio Frequency) sensors were later introduced, because some were able to read past the surface and into inner layers of a user's finger to sense a fingerprint. Different radio frequencies have been utilized by various devices along with different forms of detection including amplitude modulation (AM) and, phase modulation (PM). There are also differing
• one type for example US Patent No. 5,963,679
• another type for example US Patent No. 7,099,496
• circuit board via pitch is on the order of 200um, vs. the 50um pitch of the sensor array itself. Additionally, the added process steps required to form vias between layers of a circuit board significantly increase the tolerances for the minimum pitch of traces on each of the layers.
• Single-sided circuits may be readily fabricated with high yield with line pitch as low as 35um, whereas double sided circuits require a minimum line pitch on the order of 60um or more, which is too coarse to implement a full 500dpi sensor array.
• One further consideration is that at similar line densities, double-sided circuits with vias are several times more expensive per unit area than single sided, making high-density double sided circuits too expensive for low cost sensor applications.
• Swipe Sensors being cheaper, they take up less real estate in a host device, whether it is a laptop or a smaller device, such as a cellular phone or personal data device.
• touchpad and touch screen devices consist of arrays of drive and sense traces and distinct sense electrodes, they are incapable of resolutions below a few hundred microns, making this technology unsuitable for detailed imaging applications. These devices are capable of detecting finger contact or proximity, but they provide neither the spatial resolution nor the gray-scale resolution within the body of the object being sensed necessary to detect fine features such as ridges or valleys.
• Figures 1 depicts a diagrammatic view of one embodiment of the invention showing the drive and pickup plate structures with an insulating dielectric layer separating the drive and pickup lines.
• Figure 2 depicts a basic diagrammatic view of one embodiment of the invention showing the basic electrical field operation without an object in close proximity to the drive and pickup plate structures with one drive plate excited by a voltage source.
• Figure 3 depicts a basic diagrammatic view of one embodiment of the invention showing the basic electrical field operation with an object in close proximity to the drive and pickup plate structures with one drive plate excited by a voltage source.
• Figure 4 depicts a basic diagrammatic view of one embodiment of the sensor showing the differences in field intensity with and without an object in close proximity to the drive and pickup plate structures with one drive plate excited by a voltage source.
• Figure 5 depicts a basic diagrammatic view of one embodiment of the invention showing the basic electrical field operation with an object in close proximity of the drive and pickup plate structures with the selected pickup plate amplified and all inactive drive and pickup plates grounded.
• Figure 6a depicts a basic diagrammatic view of one embodiment of the invention showing the basic electrical field operation with a finger or object containing a ridge surface feature in close proximity to the active electrode pair.
• Figure 6b depicts a basic diagrammatic view of one embodiment of the invention showing the basic electrical field operation with a finger or object containing a valley surface feature in close proximity to the active electrode pair.
• Figure 7 depicts a diagrammatic view of an x-y grid of plate rows and columns depicted by lumped circuit components that represent the electric field couplings of the sensor at each drive/pickup crossover.
• Figure 8 depicts an example of an embodiment of the placement invention using a differential amplifier to take the signal from the selected pickup plate and subtract it from a reference signal plate for noise reduction purposes.
• Figure 9a depicts the drive and sense multiplexing circuitry of an embodiment of the invention which incorporates a tank circuit to compensate for input loading effects.
• Figure 9b depicts the drive and sense multiplexing circuitry of an embodiment of the invention which incorporates cascaded buffers to minimize input loading effects.
• Figure 9c depicts the drive and sense multiplexing circuitry of an embodiment of the invention which incorporates dedicated buffers for each sense to minimize loading effects.
• Figure 10 depicts an embodiment of the invention which incorporates an analog receiver to process the sensed signal, and processing circuitry to perform the drive and sense line scanning function.
• Figure 11 depicts an embodiment of the invention which incorporates a direct digital conversion receiver to process the sensed signal, and processing circuitry to perform the drive and sense line scanning function.
• Figure 12 depicts the layout of the drive and sense traces for an embodiment of the invention which incorporates the folded aspect of the invention laid out flat prior to folding.
• Figure 13a depicts the layer stack-up of an embodiment of the invention which incorporates the folding aspect subsequent to folding.
• Figure 13b depicts an embodiment of the invention which incorporates the folding aspect subsequent to folding and assembly into a rigid module.
• Figure 14 depicts a sensor system configured according to the invention for the purpose of sensing features of an object.
• Figure 15 depicts a diagrammatic view of the sensing of a fingerprint features utilizing the invention.
• Figure 16 depicts the process flow steps required to collect a 2-dimensional image with a sensor system configured according to the invention.
• Figure 17a depicts the process flow steps required to authenticate a user with a fingerprint sensor system configured according to the invention.
• Figure 17b depicts the process of template extraction from a fingerprint image typically utilized in user authentication applications. Detailed description
• the invention provides a broad solution to shortcomings in the prior art for many applications.
• the invention is directed to a two-dimensional sensor having sensor lines located on a substrate, such as a flexible substrate for example, that can be folded over on itself to form a grid array with separate sensor lines orthogonal to each other, where the crossover locations of different sensor lines create sensing locations for gathering information of the features and/or characteristics of an object.
• the drive lines and pickup lines are not electrically intersecting or connected in a manner in which they would conduct with each other, they form an impedance sensing electrode pair with a separation that allows the drive lines to project an electrical field hand the pickup lines to receive an electrical field, eliminating the need for distinct electrode structures.
• the two lines crossing with interspersed dielectric intrinsically creates an impedance sensing electrode pair.
• the sensor is configured to activate two one- dimensional sensor lines to obtain one pixel of information that indentifies features and/or characteristics of an object.
• a sensor configured according to the invention provides a two dimensional grid that is capable of capturing multiple pixels of information from an object by activating individual pairs of drive and pickup lines and capturing the resultant signal.
• This signal can be processed with logic or processor circuitry to define features and/or characteristics of an object.
• the information may be used to produce renderings of an object, such as a fingerprint, and compare the renderings to secured information for authentication.
• a device can utilize the intrinsic impedance sensing electrode pair formed at the crossings between the drive and pickup lines.
• the electric fields may be further focused by grounding drive and pickup lines near or about the area being sensed by the particular crossover location at one time. This prevents interference that may occur if other drive and pickup lines were sensing electric fields simultaneously. More than one electrode pair may be sensed simultaneously. However, where resolution is an important factor, it may be preferred to avoid sensing electrode pairs that are too close to each other to avoid interference and maintain accuracy in sensing object features at a particular resolution.
• intrinsic electrode pair refers to the use of the impedance sensing electrode pairs that are formed at each of the drive and pickup line crossover locations. Due to the fact that the invention uses each the intrinsic electrode pair at each crossover as a sensing element, no differentiating geometric features exist at individual sensing nodes to distinguish them from the interconnect lines. As a result, the alignment between the drive layers and sense layers is non-critical, which significantly simplifies the manufacturing process.
• the sensor lines may consist of drive lines on one layer and pickup lines on another layer, where the layers are located over each other in a manner that allows the separate sensor lines, the drive and pickup lines, to cross over each other to form impedance sensing electrode pairs at each crossover location.
• These crossover locations provide individually focused electrical pickup locations or pixels, or electrode pairs where a number of individual data points of features and/or characteristics of an object can be captured.
• the high degree of field focus is due to the small size of the intrinsic electrode pairs, as well as the high density of the neighboring ground provided by the inactive plates.
• the flexible substrate may have a second substrate configured with logic or processor circuitry for sending and receiving signals with the sensor lines to electronically capture information related to the object.
• a drive line is activated, with a current source for example, and a pickup line is connected to a receiving circuit, such as an amplifier/buffer circuit, so that the resulting electric field can be captured.
• An electric field extends from the drive line to the pickup line through the intermediate dielectric insulating layer. If an object is present, some or all of the electric field may be absorbed by the object, changing the manner in which the electric field is received by the pickup line. This changes the resulting signal that is captured and processed by the pickup line and receiving circuit, and thus is indicative of the presence of an object, and the features and characteristics of the object may be sensed and identified by processing the signal. This processing may be done by some form of logic or processing circuitry.
• the signal driving the drive line may be a complex signal, may be a varying frequency and/or amplitude, or other signal. This would enable a sensor to analyze the features and/or characteristics of an object from different perspectives utilizing a varying or complex signal.
• the signal may include simultaneous signals of different frequencies and/or amplitudes that would produce resultant signals that vary in different manners after being partially or fully absorbed by the object, indicating different features and characteristics of the object.
• the signal may include different tones, signals configured as chirp ramps, and other signals. Processing or logic circuitry may then be used to disseminate various information and data points from the resultant signal.
• the varying or complex signal may be applied to the drive line, and the pickup line would receive the resulting electric field to be processed.
• Logic or processing circuitry may be configured to process the resulting signal, such as separating out different frequencies if simultaneous signals are used, so that features and/or characteristics of the object may be obtained from different perspectives.
• each pixel may be captured in a number of ways.
• a drive line may be activated, and pickup lines may be turned on and off in a sequence to capture a line of pixels.
• This sequencing may operate as a scanning sequence.
• a first drive line is activated by connecting it to a signal source, and then one pickup line is connected to amplifier/buffer circuitry at a time, the information from the pixel formed at the crossing of the two lines is captured, and then disconnected. Then, a next pixel is processed in sequence, then another, then another, until the entire array of pickup lines is processed.
• the drive line is then deactivated, and another drive line is activated, and the pickup lines are again scanned with this active drive line. These may be done one at a time in sequence, several non-adjacent pixels may be processed simultaneously, or other variations are possible for a given application. After the grid of pixels is processed, then a rendering of object information will be possible.
• pickup lines or top plates 102a[m], 102b[m+l] are located on a insulating dielectric substrate layer 104 and configured to transmit a signal into a surface of an object located in close proximity to the sensor lines.
• Drive lines or bottom plates 106a[n], 106b[n+l] are juxtaposed and substantially perpendicular to the drive lines or plates and are located on an opposite side of the a insulating dielectric substrate to form a type of a grid.
• the pickup lines are configured to receive the transmitted electromagnetic fields modified by the impedance characteristics on an object placed within the range of those electric fields.
• FIG. 2 a diagrammatic view of a sensor 200 is shown having pickup lines or top plates 202a, 202b and insulating layer 204, and drive lines or bottom plates 206a, 206b.
• the Figure further illustrates how electromagnetic fields 208a, 208b extend between the drive lines and pickup plates through the substrate. Without an object within proximity, the electric field lines are uniform within the sensor structure and between the different lines. When an object is present, a portion of the electric field lines are absorbed by the object and do not return to the pickup plates through the insulating layer.
• an object 310 is illustrated proximate the sensor 300.
• the sensor 300 has pickup lines or top plates 302a, 302b, an insulating dielectric layer 304, and drive lines or bottom plates 306a, 306b.
• the drive lines and pickup lines of this device example may be individually activated, where a drive line/pickup line pair is activated to produce an active circuit.
• the result is a circuit that transmits electric field from active drive plate 316 into the combined dielectric of the insulating layer 304 and object 310 via electric field lines, 306a, 306b, and received by the active pickup plate.
• some of the field lines are captured by the object when it is placed about the active electrode pair.
• the variations in an object can be detected and captured electronically by capturing and recording the resulting electric field variations occurring at different crossover locations of the drive and pickup lines. Similar to common capacitance based placement sensors, the sensor can capture a type of image of the object surface electronically, and generate a representation of the features and characteristics of an object, such as the features and characteristics of a fingerprint in the fingerprint sensor example described below.
• the invention is not limited to this particular configuration, where one single electrode pair, several electrode pairs, or even all electrode pairs may be active at one time for different operations. In practice, it may be desirable for less than all of the electrode pairs to be active at a given time, so that any interference that may occur between close-by pixels would be minimized.
• a drive line may be activated, and the pickup lines may be scanned one or more at a time so that a line of pixels can be captured along the drive line and pickup lines as they are paired along a line at the crossover locations. This is discussed in more detail below in connection with Figure 5.
• each area over which a particular drive line overlaps a pickup line with a separation of the a insulating dielectric substrate is an area that can capture and establish a sensing location that defines characteristics or features of a nearby object about that area. Since there exist multiple sensing locations over the area of the sensor grid, multiple data points defining features or characteristics of a nearby object can be captured by the sensor configuration.
• the sensor can operate as a planar two-dimensional sensor, where objects located on or about the sensor can be detected and their features and characteristics determined.
• a sensor device includes drive lines located on or about an insulating dielectric substrate and configured to transmit a signal onto a surface of an object being sensed.
• Pickup lines are located near or about the drive lines and configured to receive the transmitted signal from the surface of an object.
• the substrate may act as an insulating dielectric or spacing layer.
• the substrate may be for example a flexible polymer based substrate.
• KaptonTM tape is widely used in flexible circuits such as those used in printer cartridges and other devices.
• the package may include such a flexible substrate, where the drive lines may be located on one side of the substrate, and the pickup lines may be located on an opposite side of the substrate.
• the drive lines may be orthogonal in direction with respect to the pickup lines, and may be substantially perpendicular to the pickup lines.
• a device may be configured with drive lines and pickup lines located on or about opposite sides of an insulating dielectric substrate, where the combination of these three components provides capacitive properties.
• the drive lines may be activated to drive an electric field onto, into or about an object.
• the pickup lines can receive electronic fields that originated from the drive lines, and these electronic fields can be interpreted by processing or logic circuitry to interpret features or characteristics of the object being sensed.
• the layer separating the drive lines from the pickup lines can provide a capacitive property to the assembly. If some or all of the drive lines are
• a grid may be formed.
• the drive lines are located and oriented substantially in parallel with respect to each other about a first plane.
• One surface of the substrate is located about the drive lines in a second plane that is substantially parallel relative to the drive lines.
• the pickup lines are located and oriented substantially in parallel with respect to each other about a third plane that is substantially parallel to the first and second planes and also located about another substrate surface that is opposite that of the drive lines, such that the substrate is located substantially between the drive lines and the pickup lines.
• the invention is directed to a sensor configured with plurality of drive and pickup lines that generally cross over each other at a pixel location and are configured to detect presence and other features and characteristics of a nearby object
• the invention is not limited to any particular configuration or orientation, but is only limited to the appended claims, their equivalents, and also future claims submitted in this and related applications and their equivalents.
• orientation of the planes (which may be deformable, and thus may be sheets separated by a substantially uniform distance) of groups of components (such as drive lines or pickup lines for example) or substrates may vary in different applications without departing from the spirit and scope of the invention.
• a plurality of drive lines are juxtaposed on one surface of a generally planar substrate, and a plurality of pickup lines are juxtaposed on an opposite surface of the planar substrate.
• the drive lines are substantially orthogonal to the pickup lines, and may be described as substantially perpendicular to the pickup lines.
• the distance between the drive lines and pickup lines may be filled with a substrate or insulating material that will provide for a capacitive configuration.
• the drive lines on one side of the substrate forms one capacitive plate, and the pickup lines on an opposite side for the corresponding capacitive plate.
• sensor lines such as sensor drive lines and sensor pickup lines
• substantially parallel drive lines These drive lines are intended to be described as parallel conductive lines made up of a conductive material formed, etched, deposited or printed onto the surface such as copper, tin, silver and gold.
• conductive lines are seldom "perfect” in nature, and are thus not exactly parallel in practice. Therefore, they are described as "substantially parallel”.
• Different applications may configure some of the drive lines even non-parallel, such that the lines may occur parallel for a portion of the line, and the line may necessarily deviate from parallel in order to connect with other components for the device to operate, or in order to be routed on or about the substrate on which it is formed or traced.
• the separate array of lines may be described as orthogonal or perpendicular, where the drive lines are substantially orthogonal or perpendicular to the pickup lines.
• the various lines may not be perfectly perpendicular to each other, and they may be configured to be off-perpendicular or otherwise crossed-over in different angles in particular applications.
• They also may be partially perpendicular, where portions of drive lines may be substantially perpendicular to corresponding portions of pickup lines, and other portions of the different lines may deviate from perpendicular in order to be routed on or about the substrate or to be connected to other components for the device to operate.
• the drive lines can transmit an electromagnetic field toward an object that is proximal to the device.
• the pickup lines may receive a signal originating from the drive lines and then transmitted through the object and through the substrate and onto the pickup lines.
• the pickup lines may alternatively receive a signal originating from the drive lines that were then transmitted through the substrate and onto the pickup lines without passing through the object.
• This electric field can vary at different locations on the grid, giving a resultant signal that can be interpreted by some type of logic or processor circuitry to define features and/or characteristics of an object that is proximate the assembly.
• the drive lines and pickup lines may be controlled by one or more processors to enable the transmission of the signal to an object via the drive lines, to receive a resultant signal from an object via the pickup lines, and to process the resultant signal to define an object image.
• One or more processors may be connected in one monolithic component, where the drive lines and pickup lines are incorporated in a package that includes the processor.
• the drive lines, pickup lines and substrate may be assembled in a package by itself, where the package can be connected to a system processor that controls general system functions. This way, the package can be made part of the system by connecting with a system's input/output connections in order to communicate with the system.
• the senor can be connected as a stand-alone component that communicates with the system processor to perform sensor operations in concert with the system processor.
• a sensor may be configured to drive signals at different frequencies since the impedance of most objects, especially human tissue and organs, will greatly vary with frequency.
• the receiver In order to measure complex impedance at one or more frequencies of a sensed object, the receiver must be able also to measure phase as well as amplitude.
• the resulting signal generated from a given impedance sensing electrode pair may result from varying frequencies, known in the art as frequency hoping, where the receiver is designed to track a random, pseudo-random or non-random sequence of frequencies.
• a variation of this embodiment could be a linear or non- linear frequency sweep known as a chip. In such an embodiment one could measure the impedance of a continuous range frequencies very efficiently.
• a grid sensor as described above may be configured to also operate as a pointing device.
• Such a device could perform such functions as well known touch pads, track balls or mice used in desktops and laptop computers.
• a two dimensional impedance sensor that can measure the ridges and valleys of a finger tip may be configured to track the motion of the fingerprint patterns.
• Prior art swiped fingerprint sensors can perform this function, but due to the physical asymmetry of the array and the need to speed correct, or "reconstruct" the image in real time make these implementations awkward at best.
• the sensor could also double as both a fingerprint sensor and a high quality pointing device.
• One device configured according to the invention includes a first array of sensor lines on a flexible substrate, and a second array of sensor lines on a fiexible substrate, and also a processor configured to process fingerprint data from the first and second arrays of sensor lines.
• a processor configured to process fingerprint data from the first and second arrays of sensor lines.
• the separate sensor lines When folded upon itself in the case of a single flexible substrate or when juxtaposed in the case of separate substrates, the separate sensor lines cross each other without electrically shorting to form a grid with cross-over locations that act as pixels from which fingerprint features can be sensed.
• an array of substantially parallel sensor drive lines is located on a surface of the flexible substrate. These drive lines are configured to sequentially transmit signal into a surface of a user's finger activating a line at a time.
• a second array of sensor lines is similar to the first, consisting of substantially parallel sensor pickup lines that are substantially perpendicular to the drive lines. These pickup lines are configured to pick up the signal transmitted from the first.
• the fiexible substrate is further configured to be folded onto itself to form a dual layer configuration.
• the first array of sensor drive lines becomes substantially perpendicular to the second array of pickup sensor lines when the flexible substrate is folded onto itself.
• This folding process creates crossover locations between these separate arrays of sensor lines - though they must not make direct electrical contact so that they operate independently.
• These crossover locations represent impedance sensing electrode pairs configured to sense pixels of an object and its sub-features juxtaposed relative to a surface of the flexible substrate. The scanning of these pixels is accomplished by activating individual rows and columns sequentially.
• the perpendicular pickup rows are scanned one at a time over the entire length of the selected driver. Only one row is electrically active (high impedance) at a time, the non active rows are either shorted to ground or multiplexed to a state where they do not cross couple signal.
• a finger ridge is placed above an array crossover location that is active, it interrupts a portion of the electric field that otherwise would be radiated through the surface film from the active drive column to the selected row pickup.
• the placement of an object's sub feature, such as a ridge or valley in the case of a fingerprint sensor, over an impedance sensing electrode pair results in a net signal decrease since some of the electric field is conducted to ground through the human body.
• the valley affects the radiation of electric field from the selected drive line to the selected pickup line much less than a ridge would.
• the senor can be configured to detect the presence of a finger surface located proximate to the sensor surface, where the drive lines can drive an active electromagnetic field onto the finger surface, and the pickup lines can receive a resulting electromagnetic field signal from the pickup lines.
• the drive lines can generate an electric field that is passed onto the surface of the finger, and the different features of the fingerprint, such as ridges and valleys of the fingerprint surface and possibly human skin characteristics, would cause the resulting signal to change, providing a basis to interpret the signals to produce information related to the fingerprint features.
• a flexible substrate is used as the insulating dielectric layer 104, to allow for beneficial properties of durability, low cost, and flexibility.
• the drive lines or plates 106a, 106b are located on the flexible substrate and configured to transmit a signal into a surface of a user's fingerprint features and structures, such as ridges and valleys, placed on or about the sensor lines.
• the pickup lines 102a, 102b are configured to receive the transmitted signal from the user's finger surface.
• a processor (not shown) can be configured to collect and store a fingerprint image based on the received signal from the pickup lines.
• Figure 4 illustrates the field interactions of a basic sensor cell.
• FIG. 4 an example a sensor 400 configured as an object sensor, where the top plates or pickup lines 402a, 402b, ..., 402n are located on one side of insulating dielectric layer or substrate 404. Bottom plates or pickup lines 406a, 406b, ..., 406n are located on an opposite side of the substrate 404. Electric fields 408a, 408b extend from bottom plates or drive lines 406a, 406b through the insulating layer or substrate 404 and onto active top plate 402a.
• these drive lines may be activated one at a time to reduce any interference effects, but the electric field results illustrated here are intended to illustrate a contrast between electric fields that are partially or fully absorbed by the object with electric fields that are not absorbed the object at all.
• This information may be collected from drive and pickup plate electrode pairs at each crossover location to sense features and characteristics of the object that is proximate the sensor lines.
• Partially covered top plate or pickup line 402b is connected to voltmeter 417, and uncovered top plate 402a is connected to voltmeter 418.
• Active drive line or bottom plate 406b is connected is connected to AC signal source 416, causing an electric field to radiate from active plate 406b.
• the number of drive lines and pickup lines can vary depending on the application, and it may depend on the cost and resolution desired.
• the electric field lines 408a is partially captured by the drive lines 402a and 402b, and part is captured by the object, in this case finger 410.
• volt meter 417 illustrates the response to the top plate or drive line 402b
• voltmeter 418 illustrates the response of top plate or drive line 402a.
• the difference in the deflections of voltmeter 417 in comparison 418 show the delta in electric field intensity between the two electrode pair locations, one with a finger present the other without.
• FIG. 5 another example of a sensor configured according to the invention is illustrated the Drive and pickup configuration when detecting the presence of an object.
• the sensor 500 is illustrated, where the top plates or pickup lines 502a, 502b, ..., 502n are located on one side of insulating layer or substrate 504, and bottom plates or drive lines 506a, 506b, ..., 506n are located on an opposite side of the substrate 504.
• the pickup lines are shown on the layer closest to the object being sensed for maximum sensitivity, and the drive lines shown on the opposite side of the substrate.
• Electric fields 508a, 508b extend from bottom plates or drive lines 506a, 506b through the insulating layer or substrate 504 and onto active top plate 502b.
• Other configurations are possible, perhaps having drive plates on the top, and pickup plates on the bottom.
• the invention is not limited to any particular configuration that is insubstantially different than the examples and embodiments disclosed and claimed herein.
• Figure 5 further shows a snapshot of one selected individual electrode pair located at the crossover of pickup line 502b and drive line 506b, where the remaining pickup and drive lines are not active, shown grounded in Figure 5.
• Drive line 506b is connected to AC voltage source 516
• pickup line 502b is connected to amplifier/buffer 514.
• electric field lines 508a, 508b are generated, and they radiate from drive line 506b and are sensed by pickup line 502b, sending the resultant signal into amplifier/buffer 514, and are later processed by analog and digital circuit functions.
• Grounding the inactive adjacent drive and pickup lines focuses the electric fields 508a and 508b at the crossover location between the active the drive and pickup plates, limiting crosstalk from adjacent areas on the object being sensed.
• different drive line/pickup line crossover pairings may be activated to capture different pixels of information from the object.
• an object sensor it can capture information on the shape of the object, and, if the electrical characteristics are non-uniform across its surface, it's composition.
• the invention is not limited to this particular configuration, where one single electrode pair, several electrode pairs, or even all electrode pairs may be active at one time for different operations.
• a drive line may be activated, and the pickup lines may be scanned one or more at a time so that a line of pixels can be captured along the drive line and pickup lines as they are paired along a line at the crossover locations.
• the AC voltage source 516 may remain connected to drive line 506b, and the connection of the amplifier/buffer 516 may cycle or scan over to sequential pickup lines, so that another pixel of information can be captured from another pickup line crossover paired with drive line 506b.
• drive line 506b can be deactivated, than another drive line in sequence can be activated with the AC voltage source, and a new scanning can commence through the pickup lines.
• a two dimensional image or rendering of the object features and characteristics can be made, such as a rendering of the shape of the object, and potentially a composition map.
• a reduced cost fingerprint swipe sensor could be configured using the same innovation provided by the invention.
• a reduced number of pickup lines could be configured with a full number of orthogonal drive lines.
• Such a configuration would create a multi-line swipe sensor that would take the form of pseudo two-dimensional sensor, and when a finger was swiped over it would create a mosaic of partial images or slices. The benefit of this would be to reduce the complexity of image reconstruction task, which is problematic for current non-contact silicon sensors that rely on one full image line and a second partial one to do speed detection.
• Figures 6a and 6b illustrate the operation of the sensor when detecting surface features of an object such as fingerprint ridges and valleys.
• the sensor is configured identically to the previous example in Figure 5, but in this case is interacting with a textured surface such as a fingerprint.
• FIG. 6a and b another example of a sensor configured according to the invention is illustrated.
• the sensor 600 is illustrated, where the top plates or pickup lines 602a-n are located on one side of insulating layer or substrate 604, and bottom plates or drive lines 606a-n are located on an opposite side of the substrate 604.
• For maximum sensitivity pickup lines are shown on the layer closest to the object being sensed, and the drive lines shown on the opposite side of the substrate.
• Figure 6a shows electric field lines 620 as they interact with a proximally located object's valley and Figure 6b shows electric field lines 621 as the interact with a proximally located object's peaks, extending from bottom plate drive line 606b through the insulating layer or substrate 604 and onto active drive line 606b.
• the corresponding ridges and valleys over the fingerprint surface can be captured by the grid of drive line/pickup line crossover points, and the resulting data can be used to render an image of the fingerprint.
• a stored fingerprint can then be compared to the captured fingerprint, and they can be compared for authentication. This is accomplished using any one of many fingerprint matching algorithms which are available from vendors as stand alone products. Such vendors include Digital Persona, BioKey, and Cogent Systems, to name just a few.
• FIG. 6a and b Also illustrated in Figures 6a and b, is the individual sensor line pairing of pickup line 602b and drive line 606b. Their crossover forms the active electrode pair, and the remaining pickup and drive lines are not active, and will nominally be grounded by electronic switches.
• Drive line 606b is connected to AC voltage source 616, and pickup line 602b is connected to amplifier/buffer 605.
• electric field lines 620 and 621 are created as shown in Figures 6a and 6b respectively, and they emanate between the drive line 606b and pickup line 602b, sending a resultant signal that is radiated onto pickup line 602b and connected to amplifier/buffer 605, and later processed by analog and digital processing circuitry.
• different drive line/pickup line crossover pairs may be activated to capture different pixels of information from the object.
• a fingerprint it can capture information on different features and characteristics of the fingerprint and even the body of the finger itself.
• the invention is not limited to this particular configuration, where one electrode pair, several electrode pairs, or even all electrode pairs may be active at one time for different operations. In practice, it may be preferable for less than all of the electrode pairs to be active at a given time, so that any interference that may occur between close-by pixels would be minimized.
• a drive line may be activated, and the pickup lines may be scanned one or more at a time so that a line of pixels can be captured along the drive line and pickup lines as they are paired along a line at the crossover points.
• the voltage source 616 may remain connected to drive line 606b, and the connection to buffer/amplifier 605 may cycle or scan over to another pickup line, so that another pixel of information can be captured from another electrode pair using drive line 606b.
• AC signal source 616 until an entire column of pixels is scanned, while unused drive plates (606a,c-n etc.), are switched to ground for isolation purposes. Likewise, in one embodiment only one pickup plate is active at a time and some or substantially all other pickup plates are switched to ground to minimize crosstalk.
• the two conductive layers Drive layer 606 and Pickup layer 602 are separated by an electrically insulating layer 604.
• This insulating layer 604 has high DC resistance and has a dielectric constant greater than one to allow the transmission of high frequency electric fields through it.
• this layer 602 is created by folding a single sided flexible printed circuit board back onto itself. In another embodiment it is created by placing a dielectric layer between two electrically active layers to form a double sided circuit board.
• Figure 7 shows an example of an x-y grid of plate rows and columns depicted by lumped circuit components that represent the electric field couplings of the sensor at each drive/pickup crossover.
• FIG. 7 shows a scan snapshot where one drive switch 740b in the on condition connecting the corresponding plate to the signal source. This activates one entire row 740b with AC signal over the entire length of the plate which is equal to the sensor width in one dimension.
• each column plate 703a,b,c etc. will pickup up AC signal through insulating layer 704 and coupling capacitors 761a,b,c ...n. Only one pickup plate at a time is active being switched into the buffer amplifier 716.
• Top Plate 702b is shown as the active plate in Figure 7, while all or substantially all other pickups are shorted to ground via switch matrix 730a-n, thus the information from one x-y pixel is captured.
• a single row remains active only as long as it takes the entire number of pickup plates/columns to be scanned.
• Scan time per pixel will depend on the frequency of operation and the settling time of the detection electronics, but there is no need to scan unduly fast as is typical with prior art swipe sensors.
• prior art swipe sensors must scan at a very high pixel rate in order not to lose information due to undersampling relative to the finger speed which can be greater than 20cm/sec. This reduction in capture speed relative to a swipe sensor relaxes the requirements of the analog electronics and greatly reduces the data rate that a host processor must capture in real time. This not only reduces system cost but allows operation by a host device with much less CPU power and memory. This is critical especially for mobile devices.
• the amount of signal that is coupled into the buffer amplifier 716 is a function of how much capacitance is formed by the insulating layer and the finger ridge or valley in close proximity.
• the detailed operation of how these electric fields radiate is shown in Figures 6a and b.
• the total coupling capacitance is a series combination of the insulating layer capacitance 704 which is fixed for a given thickness, and the variable topological capacitance of the object being sensed.
• the variable portion of this is shown in Figure 7 as a series of variable capacitors numbered 760a-n, 761a-n, 762a-n etc., forming a two dimensional array.
• Figure 8 shows an example of an embodiment of the placement sensor using a differential amplifier 880 to take the signal from the selected pickup plate (802a-n), and subtract it from the reference signal of plate 805.
• the electrical subtraction of these signals performs several functions: first wide band common mode is subtracted out; second, subtracting against reference plate 805 provides a relative reference signal equivalent to an ideal ridge valley; third, common mode carrier signal that couples into both plates other than through a finger is also subtracted out.
• First order carrier cancellation of etch variation in the pickup plates also occurs when we subtract out carrier that is coupled in by other means than through fingers placed on the sensor. This is critical for high volume manufacturing at a low cost.
• Reference plate 805 is intentionally located outside of the finger contact area of the sensor, separated from pickup plates 802a-n by Gap 885, Gap 885 is much larger that the nominal gap between the pickup plates which is typically 50um. In a real world embodiment plate 805 would be positioned under the plastic of a bezel to prevent finger contact, placing it at least 500um apart from the other pickup plates.
• Each one of the pickup plates 802a-n is scanned sequentially being switched through pickup switches 830a-n connecting them to Differential Amplifier 880. During the scanning process of an entire pickup row, the positive leg of the differential amplifier remains connected to reference plate 805 to provide the same signal reference for all of the pickup plates.
• Figure 9a shows a circuit diagram of an example of a front end for the placement sensor in a topology that uses a bank of Single Pole Double Throw Switches or SPDTs to scan the pickup plate rows and a bank of Single Pole Single Throw switches to multiplex the pickup plate columns.
• SPDTs Single Pole Double Throw Switches
• Each SPDT has a Parasitic Capacitance 945, due to the fact that real world switches to not give perfect isolation. In fact the amount of isolation decreases with frequency, typically modeled by a parallel capacitor across the switch poles.
• a SPDT switch we can shunt this capacitance to ground when an individual plate is not active. Since there is a large array of switches equal to the number of pickup plates, typically 200 for a 500dpi sensor, the effective shunt capacitance to ground is multiplied by that number. So if a given switch has 0.5 picofarads of parasitic capacitance and there where 200 pickups, that would add up to 100 picofarads of total shunt capacitance.
• a compensating circuit In order to prevent this large capacitance from diverting most of the received signal from the active pickup to ground, it is desirable in this example to use a compensating circuit. This is accomplished by using resonating inductor 939, forming a classic bandpass filter circuit in conjunction with parasitic capacitors 945 (one per switch) and tuning capacitors 934 and 937. A two step null & peak tuning calibration procedure is used where tuning capacitor 934 and 937 are individually tuned with inductor 939 using the same drive signal on both the plus and minus inputs to differential amplifier 980. The two bandpass filters formed with inductor 1039 and resonating capacitors 934, and 937 respectively, will be tuned to the same center frequency when there is zero signal out of differential amplifier 980.
• capacitors 934 and 937 and inductor 939 are tuned together using a differential input signal with opposite 180 degrees phases on the plus and minus inputs to the differential amplifier 980. They are incremented in lock step until the exact drive carrier frequency is reached, this occurs when the output of differential amplifier 980 is at its peak, making the center frequency equal to the exact frequency of the carrier drive signal 916.
• a calibration routine would be performed before each fingerprint scan to minimize drift of this filter with time and temperature.
• the resonating inductor 939 needs to have a Q or Quality Factor of at least 10 to give the filter the proper bandwidth characteristics necessary to optimize the signal to noise ratio.
• Figure 9b shows an alternate example of a device employing multiple banks of plates grouped together, each with their own differential amplifiers.
• voltage or current differential amplifier 980a has any plate signal conducted into it
• voltage or current differential amplifiers 980b -980n have both their positive and negative inputs shorted to ground through their respective switches 945 a-n and 945r, preventing any signal from those banks making a contribution to the overall output.
• Each of the differential amplifiers 980a -980n are summed through resistors 987a-
• Figure 9c illustrates another example of a front end circuit using individual plate buffers that are multiplexed into a second stage differential amplifier.
• Buffers 982a through 982n as illustrated are special buffers that are designed to have very low input capacitance.
• these buffers could be configured as single stage cascoded amplifiers in order to minimize drain-to-gate Miller capacitance and die area.
• two sets of switches could be used for each input.
• Analog switches 930a-930n are included in this example to multiplex each selected buffer into differential amplifier 980. Switches 932 are included to shut down the power simultaneously to all the other input buffers that are not selected. This effectively puts them at ground potential. An alternate embodiment would be to put input analog switches in front of each amplifier to allow a short of the unused plates directly to ground. One effect of this approach may be an increase in input load capacitance for each plate.
• Figure 9c shows a snapshot of the scanning process where top plate 902a is being sensed though buffer 982a which has power supplied to it through switch 932a.
• Analog switch 930a is closed, routing it to differential amplifier 980. All other buffer outputs are disconnected from the differential amplifier 980 via analog switches 930b-n and power switches 982b-n
• differential amplifier 980 The positive input to differential amplifier 980 is always connected to the reference plate 902r, providing an "air" signal reference to the amp.
• the differential amplifier 980 serves to subtract out noise and common mode carrier signal in addition to providing a "air" reference carrier value.
• Figure 10 shows a particular embodiment of a placement sensor implemented with traditional analog receiver technology.
• the analog front end begins with Differential Amplifier 1080 where selected Pickup Plate 1002a-n is subtracted from Reference Plate 1005, which is located outside the finger contact area providing a reference signal equivalent to an ideal finger valley.
• a programmable gain stage or PGA 1090 follows the Differential Amplifier 1090, but could be integrated into the same block providing both gain an subtraction in a single stage.
• PGA 1090 is designed to have a gain range wide enough to compensate for production variations in plate etching and solder mask thickness between the layers.
• Control processor 1030 orchestrates the scanning of the two dimensional sensor plate array.
• Drive plates/columns 1002a - 1002n are scanned sequentially by the Drive Plate Scanning Logic 1040 in the Control Processor 1030.
• a selected drive plate is activated it is connected to carrier signal source 1016. All inactive drive plates are connected to ground.
• Analog mixer 1074 multiplies the gained up plate signal against the reference carrier 1013. The result is a classic spectrum of base band plus harmonic products at multiples of the carrier frequency.
• An analog low pass filter 1025 is employed to filter out the unwanted harmonics and must have a sharp enough roll of to attenuate the information associated with of the second harmonic without loosing base band information.
• A/D Converter 1074 Following the low pass filter is an A/D Converter 1074 that must sample at a least twice the pixel rate to satisfy the Nyquist criteria.
• Memory buffer 1032 stores the A/D samples locally with sufficient size to keep up with the worst case latency of the host controller.
• the A/D Sample Control Line 1078 provides a sample clock for the converter to acquire the sequential pixel information that is created by the sequencing of the plate rows and columns.
• Figure 11 shows an example of one embodiment of a placement sensor implemented with direct digital conversion receiver technology.
• the analog front end begins with Differential Amplifier 1180 where selected Pickup Plate 1102a-n is subtracted from Reference Plate 1105, which is located outside the finger contact area providing a reference signal equivalent to an ideal finger valley.
• the electrical subtraction of these signals performs several functions: first wide band common mode is subtracted out; second, subtracting against reference plate 1105 provides a relative reference signal equivalent to an ideal ridge valley; third, common mode carrier signal that couples into both plates other than through a finger is also subtracted out. Elimination of common mode is particularly important in high RF noise environments. First order carrier cancellation of etch variation in the pickup plates also occurs when we subtract out carrier that is coupled in by other means than through fingers placed on the sensor. This is critical for high volume manufacturing at a low cost.
• a programmable gain stage or PGA 1190 follows the Differential Amplifier , which could easily be combined into a single differential amplifier including programmable gain as is commonly done in modern integrated circuit design PGA 1190 is designed to have a gain range wide enough to compensate for production variations in plate etching and solder mask thickness between the layers.
• Control processor 1130 orchestrates the scanning of the two dimensional sensor plate array.
• Drive plates/columns 1102a - 1102n are scanned sequentially by the Drive Plate Scanning Logic 1140 in the Control Processor 1130.
• a selected drive plate When a selected drive plate is activated it is connected to carrier signal source 1116. All inactive drive plates are connected to ground. Before activating the next drive plate in the sequence the active drive plate remains on long enough for the entire row of Pickup Plates 1102a-n to scanned by Pickup Plate Logic 1145 and captured by the A/D converter 1125.
• the A/D Converter 1125 is sampled at a rate of at least twice the carrier frequency to satisfy the Nyquist criteria.
• the A/D Sample Control Line 1107 provides a sample clock for the converter to acquire the sequential pixel information that is created by the sequencing of the plate rows and columns.
• A/D output which is at the carrier frequency against the reference carrier generated by the Digitally Controlled Oscillator 1110. The result is that the signal is down converted to the base band with the carrier removed. There are other unwanted spectral components created by this process, namely a double time carrier side band, but these can easily be filtered out.
• a combination decimator and digital filter 1120 follows the Digital Mixer 1118.
• the digital filter would typically include a Cascaded Integrator Comb, or CIC filter, which removes the unwanted spectral byproducts of mixing as well as improving the receiver signal to noise.
• a CIC filter provides a highly efficient way to create a narrow passband filter after mixing the signal down to baseband with the digital mixer.
• the CIC filter may be followed by a FIR filter running at the slower decimated rate to correct passband droop.
• Processor Buffer (1132) could be used to capture and entire fingerprint. For example a 200x200 array producing 40k pixels could be stored in a 40kb buffer. This is in contrast to a swipe sensor which must scan the partial image frames at a rate fast enough to keep up with the fastest allowable swipe speed, usually around 200ms. At the same time, a slow swipe of two seconds must also be accommodated, requiring ten times the amount of memory as the fastest one.
• Chip on Flex is a configuration where a processor chip is attached to a flexible substrate, such as KaptonTM tape, and that is electrically connected to conductive lines and possibly other components located on the flexible substrate.
• the example shown illustrates an integrated circuit 1210, which may be a logic circuit formed on a silicon substrate, a microprocessor, or other circuit for processing pixel information captured from a sensor circuit.
• the top layer 1220 is formed by an array of pickup lines connected directly to integrated circuit 1210. This may be a flip chip mounted directly to the flex substrate without bond wires.
• the bottom layer is formed by folding the single layer back onto itself along the folding axis 1230 to create double layer active sensor area 1255.
• the drive lines fold to create the bottom layer 1225.
• the drive lines in this example are split into left and right groups 1240 and 1242 respectively for the sake of layout balance, but could be all on the left or right side of the sensing area.
• the left drive plate bundles 1240, and right drive plate bundles 1242 are inter-digitated with alternating left and right feeds to form a continuous line array on bottom layer 1225.
• Flexible substrate based connector 1235 routes power, ground and interface signals out to an external host or onto another substrate that contains system level components, such as those illustrated in Figure 16 and described below. These components may include but are not limited to a processor with memory, logic enabling imbedded matching algorithm(s) and encrypting/decrypting functions.
• connector 1235 may be attached to the host substrate using conductive adhesive otherwise known as anisotropic conductive film (ACF attach), which may be labeled as "high density" in some products.
• ACF attach anisotropic conductive film
• the flex layer structure 1300 includes an imaging area 1350, in which drive lines form crossover locations with pickup lines, where the crossover locations are formed by folding the top layer 1370 over bottom layer 1372, folding the flexible substrate upon itself about flex bend radius 1374.
• the top flex 1364 is layered over top soldermask 1362, which is layered upon top copper or pickup lines 1360.
• Bottom layer solder mask 1370 is folded under top copper 1360, and bottom copper 1372 is formed under solder mask 1370 and over bottom flex 1375.
• FIG. 13b an example of a module structure 1301 is shown for mounting the flex layer structure 1300 of Figure 13 a.
• the example structure 1301 includes rigid substrate 1330 that receives the flex top layer 1370 on its top layer with flex locating pins or plastic frame 1337 configured to ensure alignment of the drive plates with the pickup plates.
• the x-y alignment tolerance requirements may be on the order of several pixels, rather than the sub-pixel alignment tolerances that would be required if there were features to be matched between the two layers.
• the four mounting holes (1337) on each layer are sufficient to ensure angular and x-y alignment. Also illustrated is driver chip 1310 and imaging area 1350.
• FIG. 14 an illustration is provided of an example system 1400 incorporating a sensor system 1402 generally configured according to the invention.
• a sensor device may be incorporated into a system, or may be configured as a stand-alone product.
• the sensor components may be encased in a housing (not shown), and electrical connections exposed for connection to a device or system that would utilize such a device.
• a housing not shown
• a sensor configured according to the invention as described herein can be incorporated into a housings that are widely used in different industry sectors.
• the mechanical connections, designs and structures may necessarily vary according to a particular application.
• FIG. 14 illustrates a diagrammatic representation of a system 1400 that incorporates a sensor 1402 configured according to the invention with the folded flexible or rigid substrate 1404 having a top layer 1406 and a bottom layer 1408, and each having either pickup lines or plates and drive lines or plates respectively depending on the application, though not shown here.
• the two-dimensional sensing area 1411 is shown with an object 1410 on top, which may be a finger in the case of a fingerprint sensor, or another object in another application.
• the top layer's pickup plates or lines (not shown) communicate with top plate processing circuitry 1410 via communication link 1412 to send resultant signals received.
• Drive lines or plates are located but not shown here on bottom layer 1408, and receive drive signals from bottom plate processing circuitry 1414 via communication line 1416.
• the top plate processing circuitry 1410 includes front end buffers and amplifiers 1416 configured to receive, amplify and/or buffer or store a resultant signal received from the pickup plates or lines.
• a switch array 1418 such as that illustrated in Figure 9 is configured to receive the signal from the front end 1416 and send the switched signal to analog to digital (A/D) converter 1420 for conversion to a digital signal.
• Digital signal processor (DSP) 1422 is configured to receive the digital signal from A/D converter 1420 and process the signal for transmission.
• Bottom plate processing circuitry 1414 is configured to produce a drive signal for use by drive plates or lines located on the bottom layer 1408 of the sensor substrate 1404, and includes drivers and scanning logic 1424 for producing the signal, and programmable frequency generate 1426 for programmable setting the frequency in which the drive signal is set.
• the bottom plate processing circuitry 1414 includes communication link 1428, likewise, top plate circuitry has communication link 1420 for communicating with system buss 1432 for sending and receiving communications among the system, such as to processors, memory modules, and other components.
• System buss 1432 communicates with persistent memory 1434 via communication link 1436 for storing algorithms 1428, application software 1440, templates 1442, and other code for persistent and frequent use by processor 1444.
• Processor 1444 includes processor logic having logic and other circuitry for processing signals received from the system buss and originating from the sensor 1402, and also includes arithmetic logic unit 1450 configured with logical circuits for performing basic and complex arithmetic operations in conjunction with the processor.
• Processor memory 1452 is configured for local storage for the processor 1444, for example for storing results of calculations and retrieval for further calculations.
• drive signals are controlled by processor 1444, and parameters for the drive signals originating from bottom plate processing circuitry 1414 are set in the bottom plate processing circuitry 1414 by the processor 1444.
• Drive signals are generated by logic 1424 within the parameters set in generator 1426 and sent to bottom plate 1408 via communication link 1416. These signals generate electromagnetic fields that extend to pickup lines on top layer 1406 about the sensing area 1411. These signals are cycled through different pixel electrode pairs on the sensor grid (not shown here, but described above.), and some of these
• the resultant signal is picked up by the pickup plates or lines located on top layer 1406 about the sensing area (not shown here, but described above.).
• the resultant signal is then transmitted to top plate processing circuitry 1410 via communication line 1412, and the signal is processed and transmitted to storage or processor 1444 for further processing.
• the image may be a fingerprint image that can be compared to a stored fingerprint image, and, if there is a match, it can be used to validate a user.
• Figure 15 Illustrates how a device configured according to the invention may be applied to a fingerprint sensing application.
• a user places a finger with fingerprint (1510) over the sensor grid, which is formed by the crossover locations of the drive plates (1506a-1506n) and the pickup plates (1502a- 1502m).
• Image pixel 1561a senses the fingerprint area above the electrode pair of drive plate 1506a and pickup plate 1502a
• pixel 1561a senses the crossover of drive 1506n and pickup 1502a
• pixel 1562n senses the area above the crossover of drive 1506n and pickup 1502m
• Figure 16 illustrates the steps required to collect the fingerprint image as shown in
• Image capture begins at step 1601.
• a row counter is initialized to 1 at step 1602.
• Step 1603 is the beginning of a row scan sequence.
• a column counter is set to 1 at step 1603.
• the top plate scanning logic 1145 activates the appropriate analog switch (one of 1103a through 1103n) for the selected row.
• Step 1605 the sense of an individual pixel begins when the bottom plate scanning logic 1140 activates the appropriate drive plate (one of 1106a through 1106n) with the carrier signal 1116.
• the signal from differential amplifier 1180 is sampled repeatedly by A/D converter 1125 after processing through programmable gain amplifier 1190.
• Digital mixer 11 18 mixes the samples down to the baseband frequency set by digital oscillator 1110.
• the baseband signal is then filtered by digital decimating filter 1120 to produce a signal level value for the current pixel.
• the functions performed for this step in the embodiment of Fig 11 could alternatively be performed by the corresponding analog receiver shown in Fig 10, or other functionally similar arrangements.
• step 1607 the signal level value derived in step 1606 is stored in the appropriate position in memory buffer 1132 which corresponds to the currently selected row and column.
• step 1608 the column number is incremented, and in step 1609 the column number is tested to determine whether the current row collection has been completed. If the row has not been completed, we return to step 1605 to collect the next pixel in the row.
• step 1610 we proceed to step 1610 and increment the row number.
• step 1611 we test the row number to determine if all the rows have been scanned. If not, flow returns to 1603 to start the next row back at the first column. Once all the rows have been scanned, image capture is complete, and we proceed to step 1612, at which point the image is ready for further processing or transfer to long term storage.
• row and column scanning order may not correspond directly to physical position in the array, as some implementations may more optimally be sampled in interleaved fashions.
• FIG 17 an example of the example as shown in Figure 14 in a user authentication application.
• a system level application 1440 on processor 1444 requires user authentication.
• the user is prompted to provide a finger for verification.
• the system waits for finger presence to be detected in step 1703. This can be performed by collecting a reduced size image as described in Figure 16 and testing for finger image, or via other dedicated hardware. Once finger presence is detected, a complete image is collected in step 1704, using the method described in fig 16 or other substantially similar method.
• step 1705 This image is then stored and in step 1705 converted into a template 1712 as shown in Figure 17B, typically consisting of a map of minutia point locations and types (such as bifurcations 1710, and terminations 1711), or possibly of ridge frequency and orientation, or some combination of both.
• the template is then compared against one or more enrollment templates that were retrieved from persistent template storage 1142 in step 1706. If a match is found, the user is authenticated in step 1708 and granted access to the application. If no match is found, the user is rejected in step 1709, and access is denied.
• the invention has application in many areas, particularly in biometric sensors. Fingerprint sensors, for example, and other biometric sensors are gaining increasing acceptance for use in a wide variety of applications for security and convenience reasons.
• Devices, systems and methods configured according to the invention will have improved security of the biometric verification process without increasing the cost of the system. Furthermore, the invention may extend to devices, systems and methods that would benefit from validation of components. As discussed above, the invention includes the ability for the host and sensor to include any combination or subset of the above components, which may be arranged and configured in the manner most appropriate for the system's intended application. Those skilled in the art will understand that different combinations and permutations of the components described herein are possible within the spirit and scope of the invention, which is defined by the appended Claims, their equivalents, and also Claims presented in related applications in the future and their equivalents.
• the invention may also involve a number of functions to be performed by a computer processor, such as a microprocessor.
• the microprocessor may be a specialized or dedicated microprocessor that is configured to perform particular tasks according to the invention, by executing machine-readable software code that defines the particular tasks embodied by the invention.
• the microprocessor may also be configured to operate and communicate with other devices such as direct memory access modules, memory storage devices, Internet related hardware, and other devices that relate to the transmission of data in accordance with the invention.
• the software code may be configured using software formats such as Java, C++, XML (Extensible Mark-up Language) and other languages that may be used to define functions that relate to operations of devices required to carry out the functional operations related to the invention.
• the code may be written in different forms and styles, many of which are known to those skilled in the art. Different code formats, code configurations, styles and forms of software programs and other means of configuring code to define the operations of a microprocessor in accordance with the invention will not depart from the spirit and scope of the invention.
• Cache memory devices are often included in such computers for use by the central processing unit as a convenient storage location for information that is frequently stored and retrieved.
• a persistent memory is also frequently used with such computers for maintaining information that is frequently retrieved by the central processing unit, but that is not often altered within the persistent memory, unlike the cache memory.
• Main memory is also usually included for storing and retrieving larger amounts of information such as data and software applications configured to perform functions according to the invention when executed by the central processing unit.
• RAM random access memory
• SRAM static random access memory
• DRAM dynamic random access memory
• flash memory and other memory storage devices that may be accessed by a central processing unit to store and retrieve information.
• RAM random access memory
• SRAM static random access memory
• DRAM dynamic random access memory
• flash memory and other memory storage devices that may be accessed by a central processing unit to store and retrieve information.
• RAM random access memory
• SRAM static random access memory
• DRAM dynamic random access memory
• flash memory and other memory storage devices that may be accessed by a central processing unit to store and retrieve information.
• RAM random access memory
• SRAM static random access memory
• DRAM dynamic random access memory
• flash memory and other memory storage devices that may be accessed by a central processing unit to store and retrieve information.
• RAM random access memory
• SRAM static random access memory
• DRAM dynamic random access memory
• machine-readable medium should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions.
• the term “machine-readable medium” shall also be taken to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by the machine and that causes the machine to perform any one or more of the methodologies of the present invention.
• the machine -readable medium includes any mechanism that provides (i.e., stores and/or transmits) information in a form readable by a machine (e.g., a computer, PDA, cellular telephone, etc.).
• a machine-readable medium includes memory (such as described above); magnetic disk storage media; optical storage media; flash memory devices; biological electrical, mechanical systems; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.).
• the device or machine-readable medium may include a micro- electromechanical system (MEMS), nanotechnology devices, organic, holographic, solid-state memory device and/or a rotating magnetic or optical disk.
• MEMS micro- electromechanical system
• the device or machine-readable medium may be distributed when partitions of instructions have been separated into different machines, such as across an interconnection of computers or as different virtual machines.
• the methods, systems and devices include improved security operations and configurations with a novel approach to biometric systems. Such systems would greatly benefit from increased security features, particularly in financial transactions.
• this embodiment is described and illustrated in the context of devices, systems and related methods of validating biometric devices such as fingerprint sensors, the scope of the invention extends to other applications where such functions are useful.
• biometric devices such as fingerprint sensors
• the scope of the invention extends to other applications where such functions are useful.
• the foregoing description has been with reference to particular embodiments of the invention, it will be appreciated that these are only illustrative of the invention and that changes may be made to those embodiments without departing from the principles of the invention, the scope of which is defined by the appended Claims and their equivalents.

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• Computer Security & Cryptography (AREA)
• Computer Hardware Design (AREA)
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• General Engineering & Computer Science (AREA)
• Image Input (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
• Transmission And Conversion Of Sensor Element Output (AREA)
• Position Input By Displaying (AREA)

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