CN111585560A

CN111585560A - Non-contact keyboard capacitance sensor and input method

Info

Publication number: CN111585560A
Application number: CN202010346417.9A
Authority: CN
Inventors: 孙滕谌; 张大华; 庄玮
Original assignee: Beijing Tashan Technology Co ltd
Current assignee: Beijing Tashan Technology Co ltd
Priority date: 2020-04-27
Filing date: 2020-04-27
Publication date: 2020-08-25
Anticipated expiration: 2040-04-27
Also published as: CN111585560B

Abstract

A non-contact keyboard capacitance sensor and key position input method, including power circuit, capacitance sensor, capacitance digital conversion circuit, control module, state feedback control circuit and indicator, communication circuit; the capacitance sensor comprises a first electrode arranged on the outer side of the periphery of the key position, a second electrode arranged on the periphery of the key position and a third electrode arranged in the center of the key position; any electrode is at least double-key, and the third electrode sinks 0.8-3.5mm lower than the second electrode; according to the detection of the self-capacitance of each electrode, the three-dimensional position of the finger on the keyboard is determined, and thus the three-state response of the finger pointing to the key position is provided through a feedback control circuit and input; the application provides structural design is reasonable, and resolution ratio is high, effectively resists various interference, and the low cost and the ripe CDC chip technique of make full use of electric capacity detection provide the commercialization non-contact input solution that can popularize for the health is sensitive.

Description

Non-contact keyboard capacitance sensor and input method

Technical Field

The application relates to a non-contact keyboard capacitive sensor and an input method, which are suitable for keyboard buttons of public health, in particular to sensing buttons considering hygiene sensitivity, such as an entrance guard keyboard, a POS (point of sale) keyboard, an ATM (automatic teller machine) keyboard and the like.

Background

The emergence of new coronary pneumonia epidemic situation, and the circumstances such as seasonal influenza present, to the disinfection of elevator etc. especially button switch's disinfection, face huge work load, even it is difficult to realize the disinfection processing of virus, for this reason the demand to the proximity sensing button appears in the society, because the button switch of direct contact public area, for example the button of elevator floor selection and switch door, the bath switch of bathroom, public drinking water switch etc. lead to infecting the communicable disease easily, and non-contact button can avoid such risk.

For the approach of human body, especially the approach of fingers operating elevator buttons, there are many technical solutions that can be adopted, including camera, infrared or radio frequency technologies, such as chinese patent No. 201480079328.5; capacitive sensing is the least costly of the various sensing schemes.

Chinese patent 201480079328 discloses a technical scheme for controlling an elevator by using gestures, and in the specification, technologies like camera shooting are mentioned to record gestures, including preset gestures, and the main technical constitution is that the gestures are recorded or even customized, the data of the gestures are recorded in a system to form a gesture library, and then after a gesture command is detected, the gesture library is compared with the gesture library to judge the meaning of the gestures, which is somewhat similar to the existing technology of identifying human faces which are already popularized; the technology needs a lot of hardware equipment and is expensive, on the other hand, customization of a user is very difficult, because human gestures and action modes are strange, the technology has a considerable challenge in two contradictions of accurate judgment, identification and interference resistance, and the difficulty of the technology is indirectly explained by the product which does not appear in the market at present.

Application No. 201610551225.5, which proposes a capacitive proximity button with a groove, the capacitive proximity button is arranged at the bottom of the groove, and the proximity button can be triggered by the finger of the designer who has to extend into the groove through the threshold value, the application does not disclose a specific capacitance measurement method of the capacitive proximity button, the proposal has the defect that the finger of the user can easily touch the inner wall of the groove when extending into the groove, especially in the environment of elevator with relatively dim light and possibly crowded personnel, and meanwhile, the gesture-sensing user is unlikely to ensure that the finger of the action can be completely controlled without shaking, otherwise the significance of sanitation sensitivity is lost; on the other hand, the patent cannot avoid the influence of environmental factors such as temperature and humidity on the set threshold.

US7498822 discloses a capacitance sensing approach scheme for human fingers, and a similar concave-designed capacitance electrode is adopted, and the above problems are also existed, if trying to avoid the above problems, according to our experiments, the distance between the finger and the switch wall is required to be more than 2cm as the design basis, then the switch arranged on the concave electrode needs the inner diameter design of 5cm at least, so that the arrangement of a plurality of switch buttons of the elevator becomes a challenge; in addition, the patent discloses a technical scheme of measuring the capacitance by a simple analog circuit, and further, in order to eliminate mutual crosstalk, an equipotential method and a differential amplifier are specially adopted, but through repeated experiments, capacitance value change which can be generated by a human finger is about 10ff magnitude under a safe distance for preventing unintentional touch on one electrode designed under an elevator environment, a good effect is difficult to obtain between measurement and elimination of environmental influence by the simple analog circuit, and the required device cost is also high. In addition, the structure of the concave electrode arrangement will increase the complexity of the forming of the hovering button structure, cause the increase of the processing cost and affect the aesthetic appearance of the hovering button and the cleaning and disinfection work of the elevator in future. The US7498822 patent only adopts a method of measuring self capacitance, but excludes a method of measuring mutual capacitance, does not utilize the advantage of strong anti-interference capability of the mutual capacitance, improves the performance of the hover button, and in addition, the patent can cause confusion and inconvenience for an operator to use the hover button due to the absence of an acousto-optic feedback system necessary for the hover button.

In a capacitance digital conversion circuit (CDC) of the prior art, such as DAI7142 and ADI7147, a delta-sigma modulation method is adopted to directly convert a measured capacitance value into a digital value by charging and discharging the measured capacitance for a plurality of times and comparing the measured capacitance value with a reference capacitance (see US patent number: 5,134,401), so that the measurement sensitivity of the capacitance can be improved to 1ff level, the requirement of a measurement system on the measurement sensitivity of the capacitance under a safe distance can be easily met, and particularly, the design of chips has a plurality of channels, so that the circuit design is simple and convenient, and the cost and the installation difficulty are effectively reduced.

Compared with technologies such as a camera, infrared or radio frequency and the like, in the aspect of detecting human body approach, the capacitance detection technology has the characteristics of simple circuit structure, low cost and the like, but has the high requirement on detection resolution due to small capacitance change, and the capacitance detection is very easily influenced by the environment.

Generally, the self-capacitance formed by the capacitance electrodes and the mutual capacitance formed by the electrodes are influenced by approaching fingers, the influence is effectively utilized, different characteristics of self-capacitance measurement and mutual capacitance measurement are considered at the same time to detect the approach degree of the fingers, and the influence of other parts of a body, misoperation and environment on the electrode capacitance measurement is synchronously eliminated, so that the influence is not easy at present.

For the hovering button adopting the capacitor to sense the approach of the human fingers, different sensing habits of a user need to be fully considered, meanwhile, the accurate judgment needs to be made by preventing the sensing of other parts of the body and the false triggering caused by the action of a cleaner during cleaning, and under the environment of an elevator, the accurate judgment is quite difficult, so that no commercialized product is found so far.

Based on the problems of these prior art, we have developed a hovering capacitive sensor and applied for a patent, application No. 202010287562.4, and the product is also put into mass production preparation.

However, for the small keyboard with about ten keys of entrance guard and vending machine, especially POS and ATM machine, because the size of each key is very small, even its layout is solidified, it is quite difficult to make a separate electrode for each key in this small size space, which can judge that the finger is close to but not in contact with, so despite the cost advantage of the capacitance sensor, although the capacitance-to-digital conversion circuit used in the capacitance sensor is quite mature, there is no non-contact commercial application in the small keyboard product with solidified size, and the requirement of hygiene sensitivity is more and more strong.

Chinese patent 201710893997 establishes four sensing electrodes around the display screen to detect the three-dimensional positioning of the fingers under non-contact, and although electronic means such as additional shielding electrodes and equipotential are adopted, in practice, the influence of the fingers and the palm behind the fingers on the electrodes and the influence of different angles of pointing actions of the human fingers are caused, so that the technical scheme cannot accurately position the fingers and cannot realize commercial application.

Chinese patent 201110130539 discloses a non-contact technical solution for a small keyboard with USB interface, which does not disclose how to construct the capacitive electrodes, but only discloses that a capacitive sensor is used to employ an induction sensor chip MC34940 of ciscail, which has 7 channels for measuring capacitance, and obviously cannot meet the requirement of at least ten numeric keypads for inputting passwords and the like.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, create a capacitive sensor especially suitable for a non-contact keyboard button, and match with a mature capacitance-to-digital conversion technology, fully utilize the immunity characteristic of a CDC circuit to stray distributed capacitance, adopt a measurement method combining self capacitance and mutual capacitance, and add a tri-state feedback indicating circuit, consider the characteristic of human finger approach, avoid various interferences, accurately judge the approach action of the finger to trigger the button, and easily accept the whole cost by commercialization.

The application discloses a non-contact keyboard capacitance sensor, which comprises a power circuit, a capacitance sensor, a capacitance digital conversion circuit, a control module, a state feedback control circuit, an indicator and a communication circuit, wherein the capacitance sensor is connected with the power circuit;

the capacitance sensor comprises a first electrode arranged on the outer side of the periphery of the key position, a second electrode arranged on the periphery of the key position and a third electrode arranged in the center of the key position;

the first electrodes comprise full-key-position transverse electrodes arranged up and down outside the peripheries of the key positions and at least two-key-position vertical electrodes arranged left and right outside the keyboard;

the second electrodes comprise at least two-key vertical electrodes at the left and right of the keyboard position and two-key electrodes transversely arranged up and down of the keyboard, and all the second electrodes are positioned in the same plane;

the third electrode is a central electrode of the keyboard center which forms a height difference of 0.8-3.5mm with the second electrode in the height direction;

the capacitance digital conversion circuit comprises a capacitance excitation signal circuit, and the capacitance excitation signal circuit generates a high-frequency square wave excitation signal;

each electrode is connected with a capacitance digital conversion circuit, and the capacitance digital conversion circuit is connected with the control module; the control module is connected with the state feedback control circuit and the indicators, and the indicators are positioned on the corresponding key positions;

the control module

Outputting a trigger signal of the key button according to the fact that a human finger points to a quick trigger area above a certain key position and exceeds a specified time;

or outputting the triggering signal of the key button according to the fact that the residence time of the human finger pointing to the effective triggering area above a certain key position exceeds the set time and/or the virtual clicking action of the human finger in the effective triggering area above the certain key position.

Still further, the center electrode is a square or circular ring electrode occupying the 2 x 2 terminus.

Or the central electrode is composed of electrodes occupying at least two key positions and distributed left and right or distributed up and down.

The first electrode and the second electrode are in the same plane.

Or the first electrodes are all obliquely arranged and lean against the upper part of the central electrode.

The first electrode further comprises another all-bonded electrode positioned at a lower position.

And an active shielding electrode is arranged below the first electrode, the second electrode and the third electrode, and the area of the active shielding electrode is not smaller than the orthographic projection area of the first electrode, the second electrode and the third electrode.

The method of the patent comprises the following steps: the input method of the non-contact keyboard comprises the capacitance sensor, and the self-capacitance values formed by all the electrodes of the first electrode, the second electrode and the third electrode and the fingers are periodically detected in a time-sharing manner along with the movement of the fingers above each key position of the keyboard;

in the determination of the key position pointed by the finger in the transverse direction, judging according to whether the ratio of two capacitance values is smaller than the transverse preset value of the key position, wherein the two capacitance values are used as the ratio of the capacitance value of the first electrode at the transverse farthest position to the capacitance value of the first electrode or the second electrode at the transverse closest position of the key position on the opposite side;

in the determination of the key position pointed by the finger in the longitudinal direction, the judgment is also carried out according to whether the ratio of two capacitance values is smaller than the longitudinal preset value of the key position, wherein the two capacitances are used as the ratio of the capacitance value of the first electrode which is farthest in the longitudinal direction to the capacitance value of the first electrode or the second electrode which is closest to the key position in the longitudinal direction on the opposite side;

judging whether the finger enters the effective triggering area or not according to whether the capacitance of the second electrode closest to the key position on the capacitance ratio of the central electrode is smaller than the height preset value of the key position or whether the capacitance ratio of the second electrode where the key position is located on the capacitance ratio of the central electrode is smaller than the height preset value or not;

if the finger is closer to the second electrode plane than the minimum of the effective trigger area, the user is considered to enter a fast trigger state: according to the key positions determined transversely and longitudinally, the controller lights the key position of the finger position to enter a pre-triggering state, continues to detect and calculate the self-capacitance value of each electrode, delays to judge whether the finger is still at the position, lights the confirming state if the finger is still at the position, and outputs a triggering signal of the key position;

otherwise, if the finger enters the active trigger area: according to the determined key position transversely and longitudinally, the controller controls the state feedback control circuit to light the indicator pre-triggered by the key position; once the finger leaves a certain key position and enters the next key position, the controller controls the state feedback control circuit to close the pre-triggered indicator of the left key position and light the indicator of the next key position where the finger enters; detecting and calculating the residence time of human finger pointing to the effective trigger area on the key position, judging whether the residence time exceeds the set time, and/or detecting and calculating the self-capacitance change of the electrode required by the finger key position to determine the transverse and longitudinal positions, judging that the finger has click action on the key position, and outputting the trigger signal of the key position by the controller.

In particular, the electrode arrangement and the operating method of the present application also have the following advantages: firstly, each key position adopts at least two key position electrode structure design, and the sensitivity in the vertical direction is improved by at least one time by improving the area of the key position electrode by at least one time, thereby effectively improving the minimum safety distance. The risk of virus propagation caused by the contact of fingers with key positions is fundamentally avoided; secondly, by a method of calculating the ratio of the transversely and longitudinally nearest adjacent second electrode to the farthest first or second electrode corresponding to each key position, the spatial resolution in the horizontal direction is effectively improved, so that the false triggering rate of the adjacent key positions of the keypad is greatly reduced, and the method is particularly suitable for the keypad transformation of the existing stock equipment; thirdly, the virtual click triggering method provided by the invention does not need to delay to wait for reaching the hovering time threshold, thereby effectively improving the hovering keypad input efficiency; fourthly, when the password is input, a method of combined input of quick triggering or hovering triggering and virtual click triggering can be adopted, so that the safety is greatly improved, and even an anti-peeping cover arranged on an ATM keyboard for safety reasons can be removed, and the inconvenience of searching for keys caused by the cover is reduced;

the control module may adopt an MCU, and with the continuous development of electronic technology, a chip combining a capacitance-to-digital conversion circuit CDC and a control module MCU appears, such as a PSoC 4100S Plus series of CYPRESS, but the functional composition is so.

Drawings

FIG. 1-1 shows one embodiment of a center electrode in phantom; FIGS. 1-2 show, in phantom, a center electrode of another embodiment; 1-3 and FIGS. 1-4 again show circular and annular center electrode schemes; FIGS. 1-5 show schematic views of an arrangement in which the first electrode is arranged obliquely; FIGS. 1-6 disclose schematic diagrams of alternative arrangements of a first electrode having a total of two full key positions below;

FIG. 2 is a key layout corresponding to FIG. 1 in the present application;

FIG. 3 is a schematic diagram of the input of the present application with a finger pointing to a key;

FIG. 4 is a schematic diagram of the active and fast triggering regions of the present application located above the key locations;

FIG. 5 is a logic diagram of the method of the present application;

fig. 6 is a schematic circuit diagram of the present application.

FIG. 7-1 is a schematic view of a finger above key No. 6, and FIG. 7-2 is a schematic view of a longitudinal cross-section of the finger entering the effective triggering area of key No. 6; FIG. 7-3 is a schematic diagram in transverse section of the effective triggering area of key No. 6 entered by finger;

FIG. 8 is a graph of capacitance change produced by a finger clicking within the active trigger area above the key location;

FIG. 9 is a schematic view of a structure for mounting an active shielding electrode;

FIG. 10 is a schematic diagram of a structure according to an embodiment.

Detailed Description

The keyboard for entrance guard, ATM, etc. basically solidifies structure and size, and because it may involve the requirement of cipher code input, at least ten digital keys 0-9, sometimes a confirmation key, and for bank, it may need double zero "00" key, so that in general, 12 keys of

3X

4 or 16 keys of 4X 4 need to be developed, and when 16 keys are not used, some keys are combined, and two keys are combined into one key, and in view of this situation, the technical characteristics of the invention will be described in detail by using the technical scheme of 16 keys in the schematic diagram.

Referring to fig. 1 and 2, regarding the arrangement of the key positions, fig. 2 shows 16 key positions, labeled with numerals 1-16, and also shows the arrangement of the electrodes corresponding to the key positions, and for the electrodes, referring mainly to fig. 1, the non-contact keyboard capacitance sensor of the invention comprises a power circuit, a capacitance sensor, a capacitance-to-numeral conversion circuit, a control module, a state feedback control circuit, an indicator and a communication circuit; wherein:

the capacitance sensor comprises a first electrode A-1/A-2/A-3/A-4/A-5/A-6 arranged outside the periphery of the key, a second electrode A-7/A-8/A-9/A-10/A-11/A-12 arranged around the key and a third electrode B-1 arranged in the center of the key;

the first electrode comprises full-key-position transverse electrodes A-1 and A-2 which are arranged up and down outside the key position periphery, and at least two-key-position vertical electrodes A-3/A-4 and A-5/A-6 which are arranged left and right outside the keyboard;

the second electrodes comprise at least two key position vertical electrodes A-7/A-8 and A-9/A-10 at the left and right of the keyboard position, and two key position electrodes A-11 and A-12 which are transversely arranged up and down the keyboard, and all the second electrodes are positioned in the same plane;

the third electrode B-1 is a central electrode of the keyboard center which forms a height difference of 0.8-3.5mm with the second electrode in the height direction;

with reference to the schematic diagram of fig. 6, the capacitance-to-digital conversion circuit CDC itself comprises a capacitance excitation signal circuit that generates a high-frequency square wave excitation signal;

the electrodes a-1 to a-12 and B-1 are divided into a first electrode 1 (electrodes a-1 to a-6), a second electrode 2 (electrodes a-7 to a-12) and a third electrode 3 (electrode B-1), and are connected to a capacitance digital conversion circuit CDC, and the capacitance digital conversion circuit CDC is connected to the control module, in the industry, the control module may adopt MCU, and with the continuous development of electronic technology, a chip 6 combining the capacitance digital conversion circuit CDC and the control module MCU into one appears, such as PSoC 4100S Plus series of CYPRESS, but the functional composition is so.

The control module is connected with the state feedback control circuit 5-3 and the indicator, the indicator is positioned on each corresponding key position, the indicator is not shown in the figure, and in the prior art, the best proposal is to install LED lamps which display two states or three states and different colors in the key position or nearby;

referring to fig. 3 to 7, the control module MCU

Outputting a trigger signal of the key button according to that a human finger points to a quick trigger area 2-2 above a certain key position and exceeds a specified time;

or, the triggering signal of the key button is output according to the fact that the residence time of the human finger pointing to the effective triggering area 2-1 on the upper part of a certain key position exceeds the set time and/or the virtual clicking action of the human finger in the effective triggering area 2-1 above the certain key position, namely, the certain key position input by the user in a non-contact way is output to the equipment needing to be controlled, such as an entrance guard or an ATM machine, and the requirements of continuously inputting passwords and the like are met. FIG. 4 schematically shows the upper sensing area of the keyboard divided into an active triggering area 2-1 and a fast triggering area 2-2, i.e. closer to the surface of the keys than to the active triggering area, even to the point of risk of viral infection; the effective triggering area is a height range which is set according to the requirement of the keyboard and is away from the surface of the keyboard, for example, a height layer which is 6-35mm away from the surface of the second electrode, the elimination of the virus infection risk is mainly considered, and the habit that a user can control the movement of the finger of the user is set according to factors such as the resolution of the electrode sensing finger movement.

Referring to the various schematic views in fig. 1, the center electrode B-1 may be a square electrode (fig. 1-1) or a circular (fig. 1-3) or circular (fig. 1-4) electrode occupying 2 x 2 of the bond; the central electrode B-1 may also be composed of two electrodes distributed left and right, as shown in fig. 1-2, but of course, the central electrode may also be composed of electrodes distributed up and down and occupying at least two key positions.

In general, the first electrodes A-1 to A-6 are in the same plane as the second electrodes A-7 to A-12, but for better detection of a finger above each key position, the first electrodes A-1 to A-6 are all obliquely mounted toward the top of the central electrode, see FIGS. 1-5.

Because the size of the keyboard is solidified or limited, and the resolution requirement of the capacitance sensor to human fingers is considered, the invention adopts at least two-key electrode arrangement besides arranging the first electrode except the key position and the third electrode sinking for a certain distance, can meet the requirement of resolution, and then considers the influence of the palm of the finger on the position of the finger detected by the capacitance sensor and the general use habit of the user, adopts the topological arrangement of the key position electrodes as shown in figure 1, because the user generally stretches out the finger to not contact each key position of the keyboard, the human body part with the palm located below, sometimes much larger than the fingers, poses a challenge to the first electrode a-2 below, for which purpose, in order to effectively detect and eliminate the effect of the palm, an electrode C-1 (see FIGS. 1-6) is additionally provided at the lower portion of the first electrode A-2.

When the capacitance sensor composed of the first, the second and the third electrodes is installed at a required place, the installed structural member is a huge metal shell, for example, the ATM machine of the bank needing safety protection, the sensitivity of the capacitance sensor for detecting the position of the human finger and the possible interference can be influenced by the existence of the metal shell, for this purpose, the invention can also arrange an active shielding electrode 4 under the electrode, the area of the active shielding electrode is not less than the sum of the orthographic projection areas of the first electrode, the second electrode and the third electrode, referring to fig. 9, the active shielding electrodes 4 are all connected to the CDC, the CDC periodically measures the self-capacitance of each electrode plate in a time-sharing manner, and the voltage follower is formed by using the operational amplifier in the CDC, so that the active shielding electrodes 4 and each electrode plate included in the first electrode 1, the second electrode 2, and the third electrode 3 form an equipotential to achieve the effect of active shielding.

For the input method of the non-contact keyboard, based on the capacitance sensor formed by the electrodes of various schemes introduced above, the self-capacitance values formed by all the electrodes of the first, second and third electrodes and the fingers are periodically detected in a time-sharing manner along with the movement of the fingers above the key positions of the keyboard; referring to fig. 7, when a human finger is located above the number 6 key and enters the effective trigger area 2-1 of the number 6 key, the finger is periodically scanned in a time-sharing manner to enter the effective trigger area, and the position of the finger in the X, Y axis direction in the keyboard can be found from the threshold table by calculating the self-capacitance ratio of each electrode plate of the first electrode, the second electrode and the third electrode. 7-2, and 7-3, the ratio of the self-capacitance C5 formed by the finger and the first electrode A-5 farthest in the X-axis direction (transverse direction) to the self-capacitance C7 formed by the first or second electrode A-7 nearest in the opposite direction meets the requirement in the threshold table, and the ratio of the self-capacitance C2 formed by the finger and the first capacitor plate A-2 farthest in the Y-axis direction (longitudinal direction) to the self-capacitance C11 formed by the first or second electrode A-11 nearest in the opposite direction meets the requirement in the threshold table, so that the finger can be determined to be located at the X-axis and Y-axis positions of the keyboard, i.e., the finger can be determined to be located at key position No. 6.

Therefore, in the keyboard of the building, in the determination of the key position pointed by the finger in the transverse direction, the judgment is carried out according to whether the ratio of two capacitance values is smaller than the transverse threshold value of the key position, wherein the two capacitance values are used as the ratio of the capacitance value of the first electrode farthest in the transverse direction to the capacitance value of the first electrode or the second electrode closest to the key position in the transverse direction on the opposite side;

if the finger is closer to the second electrode plane than the minimum of the effective trigger area, it is considered that the user enters the fast trigger area 2-2 and needs to enter the fast trigger state: according to the key positions determined transversely and longitudinally, the controller lights the key position of the finger position to enter a pre-triggering state, continues to detect and calculate the self-capacitance value of each electrode, delays to judge whether the finger is still at the position, lights the confirming state if the finger is still at the position, and outputs a triggering signal of the key position;

otherwise, if the finger enters the active trigger area 2-1: according to the determined key position transversely and longitudinally, the controller controls the state feedback control circuit to light the indicator pre-triggered by the key position; once the finger leaves a certain key position and enters the next key position, the controller controls the state feedback control circuit to close the pre-triggered indicator of the left key position and light the indicator of the next key position where the finger enters; detecting and calculating the residence time of a human finger pointing to an effective trigger area on the upper part of a certain key position, judging whether the residence time exceeds the set time, and/or detecting and calculating the self-capacitance change of an electrode required by the finger at least for determining the transverse longitudinal position of the key position, judging that the finger has a clicking action on the certain key position, outputting trigger signals of the key position by a controller, and judging according to the trigger of the finger after the finger is determined to be in an X/Y/Z three-dimensional space on a keyboard, and referring to a flow chart of fig. 5.

In fig. 7-2 and 7-3, not only the height difference Δ d between the second electrode and the third electrode B-1 is shown, but also the height d1 of the finger from the second electrode, the height d2 of the finger from the third electrode, the minimum height dmin of the effective levitation region, the maximum height dmax of the levitation region, and the minimum safety distance dsaf. In the elevation direction, below the distance dmin is a fast trigger region, and the range between dmax and dmin is a valid trigger region.

In addition to the fact that the CDC in the prior art can measure the self-capacitance of each electrode after being connected into the electrodes, the CDC can also measure the mutual capacitance formed between the two electrodes, and because the mutual capacitance is relatively difficult to be interfered by factors such as the environment and the like, the height d1 of a finger on a keyboard can be accurately measured, and only the measurement range is relatively limited.

After the finger is determined to be above the key position, the key position is triggered by three schemes, one scheme is that the finger enters a quick trigger area to trigger, the other scheme is that the finger hovers for a certain set time in an effective trigger area to trigger, the general hovering time is set between 0.5 and 2 seconds, and the optimal hovering time is 0.5 to 1 second; the third is that the finger performs one-time clicking action in the effective triggering area, namely triggering by virtual clicking of the key position.

The control module is connected with a feedback control circuit, the feedback control circuit controls an indicator to be in three states of no trigger, pre-trigger and trigger, and the indicator can be sound or an LED indicator lamp arranged on a keyboard or around each key position of the keyboard.

The non-contact keyboard can be made into a reverse-buckled concave structure as shown in figure 10, wherein the keyboard panel 6-1 can be made of hard acrylic or transparent PC, the first electrode 1, the second electrode 2 and the third electrode 3 are made of ito, PEdot and other transparent conductive materials to be made into a transparent key film (6-3) and extruded by a light guide plate 6-5 at the back of the transparent key film to form a transparent keyboard module, the transparent keyboard module is integrally clamped and connected onto the non-transparent support 5-2 through a clamping structure, the transparent keyboard module is connected onto a control board 6-4 hidden in the non-transparent support 5-2 through an FPC (flexible printed circuit) flat cable 6-3, an LED feedback module 6-6 is arranged on the control board 6-4, and the LED feedback module 6-6 feeds back the keyboard operation result to each corresponding key position through a light guide structure 6-5 in states of lightening, extinguishing and the like. The floating keyboard is fixed on the existing mechanical keyboard shell 6-8 through the non-transparent support 6-2, and the transparent keyboard module is perpendicular to the existing mechanical keys 6-7, so that the existing mechanical keyboard can be seen through the transparent keyboard, namely, the key position display of the existing mechanical keyboard is adopted as the key position display of the transparent keyboard. And finally, the communication line of the transparent keyboard is merged into the communication port of the existing mechanical keyboard, so that the existing equipment can be controlled by the non-contact keyboard. The additional installation scheme can not only not damage the structure of the existing mechanical keyboard, but also utilize the key position of the existing mechanical keyboard as the key position display of the non-contact keyboard, and has convenient installation, low cost and strong applicability. If the existing mechanical keyboard needs to be completely replaced, the non-contact keyboard can be realized only by adopting the light-transmitting ink silk-screen key position indication icons on the back surface of the non-contact keyboard panel 6-1, forming holes on the corresponding equipment shell 6-8, sinking the non-contact keyboard into the equipment shell 6-8, directly connecting the communication cable into the equipment to be controlled, and enabling other structures to be consistent with the front additional installation scheme.

In general, 16 of the above-mentioned key positions may have surplus, then can compound two key positions into one; for the scheme that only 12 keys are enough, the electrode design is the same as that of the figure 1-1, and only the

keys

9, 10, 11 and 12 in the figure 2 are vacant, namely the third row is vacant, so that the detection of the fourth row of the first row, the second row and the fourth row is more accurate.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present application, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A non-contact keyboard capacitance sensor comprises a power circuit, a capacitance sensor, a capacitance-to-digital conversion circuit, a control module, a state feedback control circuit, an indicator and a communication circuit; the method is characterized in that:

the control module

2. The non-contact keyboard capacitive sensor of claim 1, wherein: the central electrode is a square or circular ring electrode occupying 2 x 2 key positions.

3. The non-contact keyboard capacitive sensor of claim 1, wherein: the central electrode is composed of electrodes occupying at least two key positions and distributed left and right or up and down.

4. The non-contact keyboard capacitive sensor of claim 1, wherein: the first electrode and the second electrode are in the same plane.

5. The non-contact keyboard capacitive sensor of claim 1, wherein: the first electrodes are all obliquely arranged towards the upper part of the central electrode.

6. The non-contact keyboard capacitive sensor of claim 1, wherein: the first electrode further comprises another all-bonded electrode positioned at a lower position.

7. The non-contact keyboard capacitive sensor of claim 1, wherein: and an active shielding electrode is arranged below the first electrode, the second electrode and the third electrode, and the area of the active shielding electrode is not less than the sum of the orthographic projection areas of the first electrode, the second electrode and the third electrode.

8. A non-contact keyboard input method, which comprises the capacitance sensor of any one of claims 1-7, and is characterized in that the self-capacitance value formed by all the electrodes of the first, second and third electrodes and the finger is periodically detected in a time-sharing manner along with the movement of the finger above each key position of the keyboard;

if the distance of the finger from the second electrode plane is closer to the electrode plane than the minimum value of the effective trigger area, it is considered that the user enters the fast trigger area and needs to enter the fast trigger state: according to the key positions determined transversely and longitudinally, the controller lights the key position of the finger position to enter a pre-triggering state, continues to detect and calculate the self-capacitance value of each electrode, delays to judge whether the finger is still at the position, lights the confirming state if the finger is still at the position, and outputs a triggering signal of the key position;

9. The input method according to claim 8, characterized in that: the capacitance-to-digital conversion circuit detects the mutual capacitance between the central electrode and the second electrode where the key position is located, and is used for judging whether the human finger enters the quick triggering area.

10. The input method according to claim 8, characterized in that: the hover time is between 0.5 and 2 seconds, with an optimal hover time of 0.5-1 second.

11. The input method according to claim 8, characterized in that: the control module is connected with a feedback control circuit, and the feedback control circuit controls the indicator to be in three states of no trigger, pre-trigger and trigger.