DE202020005521U1 - Device for contactless optical imaging of a selected surface area of a hand - Google Patents

Abstract

Device for contactless optical imaging of a selected surface area of a hand of a user, with
- A housing (4) in which an image acquisition unit (1) containing a main camera (1.1) with an optical axis (1.0) and an illumination unit (2) is accommodated,
- a control and computing unit (3),
- an output unit (7),
- A frame (5) arranged outside the housing (4) and connected to the housing (4) via a frame (8), with edges (5.1) delimiting a recess (6) that is open on one side and facing a user position of the user is open and in which the surface area, occupying an actual position, is to be positioned by the user, an object plane (1.3) of the main camera (1.1) with a depth of field (1.2) being arranged within the frame (5), in which a target position for the surface area is located, characterized in that
- Either a first active means for localizing the actual position in the axial direction of the optical axis (1.0) and a second active means for localizing the actual position in the radial direction of the optical axis (1.0)
- or a universal active means for localizing the actual position in the axial and radial direction of the optical axis (1.0) are available in order to localize the actual position in relation to the optical axis (1.0) in the axial direction and in the radial direction, to guide the user iteratively by means of the output unit (7) to move the surface area in the axial and radial direction from the actual position to the target position, so that at least one image of the surface area in the target position can be recorded by the main camera (1.1) is.

Description

The outbreak of the corona virus (SARS-CoV-2) at the end of 2019 / beginning of 2020 triggered a global crisis. The virus is extremely contagious and can be transmitted via droplet and smear infections. The hubs for virus transmission include international airports. For some time now, more and more fingerprint scanners have been used to identify passengers. The first generation of fingerprint scanners were contact-based devices in which one hand, individual fingers, all fingers, one or both thumbs (biometric object) were placed on a transparent user interface. In order to avoid smear infections when using such devices in a virologically uncertain time, the user interface must be cleaned by each user after use, which requires the permanent cooperation of another user. In the case of devices that have automated interactive user guidance, no other person needs to be present to use the device properly, so that the need for regular cleaning of the user interface means that additional workers are required.

In the case of a new, contactless generation of optical fingerprint scanners based on structured lighting, the biometric object is no longer placed, but is arranged in a virtual object area of the optical system of the device.

The term fingerprint scanner has become a generic term for devices in which biometric objects, in the sense of skin structures of fingers, hereinafter referred to as surface areas, are optically captured. It does not matter whether the device in question is designed for all of the above-mentioned biometric objects or for only one or a part of them. It also does not matter how the captured image of the biometric object is generated, e.g. B. in which the object is scanned or mapped as a whole. The term imprint is historically justified. It stands for every type of image of the biometric object, regardless of whether the object is pressed onto a user interface during acquisition or is arranged in a contactless manner in a virtual object area (often also called a scan area).

The greatest challenge with the contactless fingerprint scanners is to position the hand correctly in the virtual object area so that a high resolution image can be generated. The user should be guided automatically and interactively.

In the US 2018/0330142 A1 describes a device for capturing fingerprints, with a capturing zone through which a hand of the user is moved. The device has a transparent top surface and a projection surface arranged parallel to this at a distance of a few centimeters, between which the detection zone is located. The detection zone is open frontally and laterally to the position intended for the user, so that the user can comfortably move his hand horizontally through the detection zone in front of the body. The object field of a static line camera is located within the detection zone. The camera sensor has an image recording speed that is sufficiently high to be able to record a clear image of the fingers from the individual image recordings of “lines” of the hand at a common speed of movement of the hand.

From the US 2015/0208059 A1 a device is known with which 3D coordinates, for example of a finger, are determined from a large number of images, from which a 2D representation comparable to a fingerprint, which is generated by rolling an inked finger. For this purpose, the device has a projector with structured lighting with which one or more light patterns are projected onto the three-dimensional surface of the finger, the light pattern or patterns being deformed characteristic of the biometric structure of the finger surface. One or more images of the deformed light pattern or patterns are recorded by means of a camera or several cameras. The finger surface is here arranged at a predetermined distance from the projector and the camera or cameras in a virtual plane.

To position the hand, the device has a slot in which the right or left hand is inserted. The slot encloses a scan volume in which the hand is positioned in front of a background that acts as a reference plane. At this reference plane there are positioning pins which support the correct positioning of the hand within the scan volume, so that the finger surface is positioned at the specified distance from the projector and the camera or cameras in an object plane. The arrangement of the positioning pins is decisive for the target position of the hand.

It is in the aforementioned US 2015/0208059 A1 also discloses user guidance that guides the user in positioning the hand. After the hand has been inserted into the slot, low-resolution sample images are generated, with the user being able to recognize the position of his hand in relation to the positioning pins in the sample images and thus to the correct position of the hand to be led. Additionally or alternatively, the user can be guided by automated voice information or by instructions from a person.

A particular disadvantage of the device disclosed here is that the hand is positioned by bringing it into contact with the positioning pins. A method in which the finger surface is held in a virtual plane in a non-contact manner and is optically detected can be used particularly where and then advantageously where skin contact is undesirable. By positioning the hand on the positioning pins, the advantage of the contact-free detection of the finger surface for the user, namely that he does not come into contact with anything and therefore has no skin contact with any surfaces, is nullified.

From the US 2020/0202101 A1 Another acquisition device for contactless acquisition of biometric data such as fingerprints and handprints is known.

The detection device comprises an electronics compartment in which all hardware components including a light source and a camera are accommodated and a housing guide which includes an image detection area. An object, e.g. a hand, which is positioned exactly in the image capture area can be recorded by the camera with the highest quality. Various designs for the housing guide are specified, with which an exact positioning is made possible without the object to be positioned coming into contact with the housing guide. Basically, a collar is formed on the housing guide, which surrounds the image capture area except for an entry gap. The collar represents a visual indicator for rough positioning. This means that the user who puts his hand into the image capture area will move his hand from the right direction and into a narrow space around the image capture area. The housing guide should advantageously contain a space indicator. The place indicator can have a sensor for detecting the position of the object and an output for signaling the correct position of the object to be imaged. From the disclosure that the hand can be localized with at least one IR sensor, it can be deduced that the correct position can only be meant here in relation to an axial direction. The output can e.g. B. be a flashing colored light, the color or flashing frequency can change. The output can also be the display of a suitable icon that provides the user with visual instructions for each step of the image capture. The icon can e.g. B. first show a right hand, then a left hand, and then the user's thumbs. The output can also be an audio signal change. The space indicator can also be a graphic display device that displays images and / or moving images. The images can be texts, symbols or other graphic elements. The space indicator can be connected to one or more infrared sensors present in the electronics compartment. The IR radiation reflected back on the object is used to determine whether an object has entered the image capture area, which takes place via a vertical movement within the collar. If the signal formed by the reflected radiation exceeds a predetermined threshold value, the hand has reached the image capture area and the control in the electronics compartment triggers the light source and the camera. The infrared sensor is deactivated during image acquisition in order to avoid the influence of extraneous light during image acquisition.

Disadvantageous in a detection device according to the aforementioned US 2020/0202101 A1 is that active guidance only takes place in the axial direction of the imaging system. The radial alignment of the hand is determined exclusively by the entry gap of the collar. Since the radial position of the hand is specified exclusively by the entry gap of the collar, the entry gap may only be insignificantly wider than a broad hand is. As a result, there is an increased risk that it will come into contact with the collar when it is inserted into the collar and that the radial positioning will take place with different degrees of accuracy for hands of different sizes.

The object of the invention is to create a device which is suitable for localizing the hand of a user held in a frame in an actual position and actively guiding the user until his hand is not only axially but also radially in a desired position arrives.

Advantageously, not only should at least one image of a surface area of the hand be recorded in the desired position, but it should also be recognized whether the hand is a natural hand.

The object is for a device for the optical imaging of a selected surface area of a hand of a user, with a housing in which an image acquisition unit containing a main camera with an optical axis and a lighting unit is accommodated, a control and computing unit, an output unit, an outside the housing arranged, via a frame with the housing connected frame with edges that limit a recess open on one side, which is open frontally to a user position of the user and in which the surface area is positioned by the user, an actual position occupying, with an object plane of the main camera with a depth of field in which a target position for the surface area is located is arranged within the frame.

It is essential to the invention that there is a first active means for localizing the actual position in the axial direction of the optical axis and a second active means for localizing the actual position in the radial direction of the optical axis, or that a universal active means for localizing the Actual position is present in the axial and radial directions of the optical axis. In that active localization also takes place in the radial direction, active guidance can also take place in the radial direction into the desired position. The frame is therefore only used for rough positioning, which is why the recess can be made significantly larger than the object field of the main camera, which means that contact with the frame is reliably avoided and the object field does not have to be made larger than a broad hand, which is beneficial for fast image processing.

The universal active means advantageously contains an auxiliary camera which, compared to the main camera, has a larger object field and a lower resolution, the object field of the auxiliary camera and the object field of the main camera being in the object plane of the main camera.

Alternatively, it is advantageous if the second active means contains at least one first distance sensor that emits parallel to the object plane, or the universal active means contains at least one first distance sensor and at least one second distance sensor that is at an angle not equal to 0 ° to the at least one first distance sensor emits, contains.

It is also advantageous if the second active means contains two first light barriers that form a first pair of light beams and emit in or parallel to the object plane, enclosing an angle not equal to zero with one another, mirror-symmetrical to a parallel running through the optical axis to an insertion direction of the hand are arranged.

The second active means or the universal active means can each advantageously also be a projector which is arranged on a side of the object plane facing away from the main camera and projects a pattern into the recess.

The output unit is preferably a display.

The output unit can expediently contain an ultrasound transmitter which is suitable for generating haptically perceptible pressure points on a virtual plane, which corresponds to the nominal position in the axial direction, or contain a compressed air transmitter with a planar arrangement of nozzles which are directed into the recess .

For the optical imaging of a selected surface area of a hand of a user, in which the selected surface area is positioned in a predetermined target position within a depth of field around an object plane of a main camera with an optical axis, the user enclosing the surface area to be recorded in a depth of field Frame and the surface area assumes an actual position, the actual position is localized in the axial direction in relation to the optical axis and the user is guided iteratively by means of an output unit in order to change the actual position of the hand and to increase the surface area in the axial direction to move the predetermined target position in which at least one image of the surface area is generated with the main camera. It is essential to the invention that the actual position is also localized in the radial direction in relation to the optical axis and the user, guided iteratively, moves the surface area also in the radial direction into the specified target position.

The actual position is advantageously localized repeatedly in the axial and radial directions by evaluating a large number of consecutive images of an auxiliary camera, the images of the auxiliary camera being created with a lower resolution than the at least one image recorded with the main camera. The images recorded one after the other with a lower resolution are advantageously compared with one another and analyzed to determine whether the movement towards the target position is superimposed by trembling movements or the pulsation of blood vessels in order to distinguish a real hand from a fake hand.

It is advantageous if the user is given instructions via the output unit to change the hand position in order to infer a natural hand from the course of the change in hand position.

Alternatively, the images from the auxiliary camera are advantageously analyzed for discontinuities or gradients that are untypical for a natural hand, in order, if necessary, to infer an artificial hand.

It is also advantageous to irradiate the surface area with light of at least one wavelength or to direct a measuring beam with the at least one wavelength onto the surface area. In doing so, the light is drawn in through blood vessels absorbed by the hand, with light with only one wavelength a spatial structuring in the image according to the blood vessel structure is created and with light with more than one wavelength the reflected wavelength spectrum or the amount of light reflected on the surface area is analyzed in order to identify a natural hand if necessary close.

In order to infer an artificial hand, if necessary, it is also advantageous to analyze the at least one image from the main camera for atypical distances from mountains and valleys in a papillary structure of the surface area.

For iterative guidance, a two-dimensional pattern can advantageously be projected into the recess, and the user moves the hand within the frame until the pattern is completely and sharply depicted on the back of the hand.

It is advantageous if the image of the pattern is changed in its color or in its resolution depending on the proximity to the target position.

The iterative guidance can advantageously also be supported by means of haptically perceptible pressure points on the surface area generated by ultrasound or air pressure. Additionally or alternatively, by means of the haptically perceptible pressure points generated by ultrasound or compressed air, the user can be animated to make movements that can only be perceived and executed by a natural hand in order to recognize such.

• 1 eine Vorrichtung in allgemeingültiger Darstellung für die verschiedenen Ausfüh ru ngsbeispiele,
• 2a-b eine Vorrichtung mit einem universalen aktiven Mittel, enthaltend eine Hilfskamera, zur Lokalisierung der Ist-Position in axialer und in radialer Richtung,
• 3 eine Vorrichtung mit einem zweiten aktiven Mittel, enthaltend zwei Abstandssensoren, zur Lokalisierung der Ist-Position in radialer Richtung,
• 4a-b eine Vorrichtung mit einem zweiten aktiven Mittel, enthaltend zwei Lichtschrankenpaare, zur Lokalisierung der Ist-Position in radialer Richtung,
• 5 eine Vorrichtung mit einem universalen aktiven Mittel, enthaltend einen Projektor zur Lokalisierung der Ist-Position in axialer und in radialer Richtung und
• 6 eine Vorrichtung mit einem Ultraschallgeber, zur aktiven Führung in axialer Richtung.

The invention is to be explained in more detail below with reference to drawings. Here show:

• 1 a device in a generally applicable representation for the various exemplary embodiments,
• 2a-b a device with a universal active means, containing an auxiliary camera, for localizing the actual position in the axial and in the radial direction,
• 3 a device with a second active means, containing two distance sensors, for localizing the actual position in the radial direction,
• 4a-b a device with a second active means, containing two pairs of light barriers, for localizing the actual position in the radial direction,
• 5 a device with a universal active means, containing a projector for localizing the actual position in the axial and in the radial direction and
• 6th a device with an ultrasonic transmitter for active guidance in the axial direction.

A device according to the invention is used for the optical imaging of a selected surface area, more precisely the papillary structure of a selected surface area of four fingers of a hand of a user. The surface area can, however, also be given only by individual fingers or a single or both thumbs. In the case of people with more than 4 fingers on one hand (excluding thumbs) or more than one thumb on one hand, which occurs in rare cases, the surface area can also be given by correspondingly more fingers or thumbs per hand.

The device is in 1 shown as a schematic diagram and basically contains an image acquisition unit 1 containing a main camera 1.1 with an optical axis 1.0 and a lighting unit 2 which is able to display spatially structured images in one or more colors, a computing and control unit 3 , a housing 4th , an output unit 7th , a frame 5 , and a first and second active means or a universal active means (not shown here), the first active means for determining the localization of the actual position in the axial direction, the second active means for determining the localization of the actual position in the radial direction Direction, and the universal active means for localizing the actual position in the axial and radial direction, to the optical axis 1.0 suitable is.

The frame 5 is to the image capture unit 1 arranged so that one object plane 1.3 the main camera 1.1 and correspondingly a depth of field 1.2 to the object level 1.3 , within a recess 6th of the frame 5 lies. The depth of field 1.2 and the object field OF ₁ the main camera 1.1 , please refer 2 B that is smaller than the recess 6th limit the image capture area. A surface area arranged in the image acquisition area is considered to be a surface area arranged in a desired position and is imaged in focus. The center of the image capture area is at the intersection of the optical axis 1.0 and the object level 1.3 . The frame 5 is at a distance above the housing 4th in a preferred operating position of the device aligned horizontally and with the housing 4th arranged in a fixed relative position to each other.

The output unit 7th is on the housing 4th arranged, but can also be arranged freely in the room detached from this. Especially when the output unit 7th is of a visual nature, it is related to those in an operating position Device advantageous above the frame 5 attached at eye level of the user. In the device according to the invention, the focus is on well-being and intuitive operation by the user, and any contact with the device should be avoided.

The frame 5 is over a rack 8th with the case 4th rigidly connected and has edges 5.1 on which the recess is open on one side 6th that is open frontally to a user position of a user. The edges 5.1 are advantageously set off in color in order to be perceived intuitively by the user, but can also be equipped with controllable colored lighting in order to correctly or incorrectly position the hand in the recess 6th to acknowledge in color or the attention of the user to himself or the object level 1.3 to pull. The frame 5 with the recess 6th is a means for the rough positioning of the surface area in the axial and radial directions to the optical axis 1.0 . With controllable lighting, it can also be used as the output unit 7th , serve to provide feedback to the user, or in addition to the output unit 7th , serve to inform the user. By allowing the user to use all four fingers of one hand, or even just individual fingers or his thumb, in one direction of insertion R. inserts into the frame, it positions the surface area in an actual position, which as a rule does not correspond to the target position, but is roughly close to it.

In addition to a significantly wider design of the recess 6th Compared to a wide hand, there is enough space between the housing to avoid touching the device 4th , in which the image acquisition unit 1 located, and the frame 5 where the surface area will be placed is provided.

It is essential to the invention that the device, in addition to the frame 5 , for coarse positioning for intuitive guidance of the surface area in the target position, in addition to the first active means for determining the localization of the actual position in the axial direction of the optical axis 1.0 , a second active means for localizing the actual position in the radial direction of the optical axis 1.0 , or, instead, has a universal active means which is used to determine the localization of the actual position in the axial direction and in the radial direction of the optical axis 1.0 suitable is.

It is essential to the invention for the use of the device according to the invention that the random spatial position of a surface area of the hand of a user in a frame 5 as the actual position in the axial and radial position, based on an optical axis 1.0 a main camera 1.1 an image capture unit 1 , is detected, and the user is guided iteratively, changing the actual position until the surface area has arrived in a target position that corresponds to a predetermined spatial position of the surface area. For this purpose, the user guides the surface area to be captured into a preferably horizontally aligned depth of field area that is open to the user 1.2 enclosing frame 5 on. The surface area assumes an actual position there and is iteratively guided by the user in the axial and radial directions into the target position, where at least one image of the surface area is taken with the main camera 1 is produced. In particular in the radial direction, the actual position can deviate very greatly from the target position because the recess 6th to safely avoid contact is made much larger than the breadth of a hand. In order to guide the surface area iteratively from the actual position to the target position, the respective actual position of the surface area is localized at the same time, and the results of the localization are used to control the output unit 7th used.

According to a first embodiment of a device according to the invention, shown in FIG 2a and 2 B , the universal active agent includes an auxiliary camera 9 in a known position relative to the main camera 1.1 is arranged. It forms one in the object level 1.3 larger object field OF ₉ with a lower resolution than the main camera 1.2 an object field OF ₁ images with a higher resolution. The auxiliary camera 9 as well as the main camera 1.1 , Images in an optical 3D process, with which the spatial position of the surface area in the radial and axial direction relative to the target position can be derived from the images. Here is the object field OF ₉ the auxiliary camera 9 preferably in a size of at least 90% of the size of the recess 6th of the frame 5 so that the auxiliary camera also has a broad hand in every possible actual position 9 is mapped. The resolution of the auxiliary camera 9 is advantageously only so large that the localization of the surface area can be deduced from the image. Should the auxiliary camera 9 in addition to fulfilling further functions for localization, it may be that it advantageously has a higher resolution, but that in each case is lower than that of the main camera 1.1 . This is used to process images with the auxiliary camera 9 in any case faster than that of the main camera 1.1 . A depth of field is also advantageous 9.2 the auxiliary camera 9 larger than the depth of field 1.2 the main camera 1.1 .

Depending on the spatial location, which in each case represents an actual position as a function of time during the active guidance, the user is informed via the output unit 7th iteratively guided.

Technically, the localization takes place in the axial and radial direction of the optical axis 1.0 with an auxiliary camera 9 by creating optical images of the surface area one after the other, from which an actual position of the surface area within the edges given at the time the optical image was created 5.1 of the frame 5 can be derived in the axial and radial directions. The respective actual position is compared with the target position and, depending on the comparison result, the user is guided iteratively until the selected surface area has reached the target position and with the main camera 1.1 Pictures are taken. Images can also be recorded if only parts of the surface area are in the target position. A large number of images are then created in which different parts of the surface area are in the target position. From the large number of images, an overall image is then created that represents a sharp image of the entire surface area.

The use of the auxiliary camera 9 Compared to all of the second or first modified means specified below, it has the advantage that with it the actual position of the surface area can be detected very precisely, which is determined by the position of the hand in the recess 6th and the hand posture (hand curvature) is determined. The detection of the hand position results in the advantage of optimized user guidance with detailed specifications for improved mapping of the surface area with the main camera 1.1 . For example, if the hand is too slanted, by 90 ° or even by 180 ° (back of the hand looks towards the main camera) to the target position in the frame 5 held, an adapted user guidance can take place, which informs the user that he has to turn his hand accordingly for a successful image. The same applies to an inclined hand positioning within the plane of the recess.

The same applies to the presentation of curved fingers, which makes optimal imaging of the entire surface area difficult, and the auxiliary camera 9 is recognized. There is an advantage with the auxiliary camera 9 also the possibility of differentiating between an artificial hand or a natural hand provided with a coating and a natural hand.

Thus, in a first embodiment of the device, the detection can take place via an approach analysis. The successively recorded images are analyzed and compared with one another to determine whether the movement led to the target position is superimposed by a trembling movement that is characteristic of a real natural hand.

In addition or in a second embodiment, the user receives from the output unit 7th Instructions to change the hand position through certain movements, for example bending the fingers or moving individual fingers, which an artificial hand cannot do, at least in a natural way, whereby it is recognized as a forgery.

Instructions can be given on the output unit 7th For example, an image of the user's hand executing the specified movement can be displayed in the form of a display. In addition, the user can be given feedback via symbols. Alternatively, for example, a virtual hand can be shown on the display in a real environment, the virtual hand specifying the movement for the real hand and assuming a predefined position and hand posture.

By requesting gestures such as "curve hand", "outstretched index finger" or "hand straight", an artificial hand, such as a rubber hand, can be recognized because it is not able to comply with the request.

An artificial hand, such as a full-volume rubber hand, cannot follow the request for a certain sequence of movements when taking the picture, such as first inserting the right hand, then the left hand and finally the two thumbs into the frame, as it is individual Can't move the phalanges of the fingers independently of each other.

In a third embodiment, the auxiliary camera 9 or the main camera 1.1 If necessary, points of discontinuity or gradients that are untypical for natural hands, in particular sharp demarcations or edges, are found, which typically arise with overcoats or 2D forgeries placed on the finger.

For further embodiments of the device, it is proposed to illuminate the hand with light of at least one wavelength, which is absorbed by the blood in the blood vessels, so that these can be recognized in the image of a real hand. In the case of light with more than one wavelength, the spectrum of the reflected light component can be analyzed. On the one hand, it can be assumed that an artificial hand does not have the same spectral properties as a natural hand and, on the other hand, that an artificial hand does not have any vascular structures.

As an alternative or in addition, the presence of a pulse can be determined via regular microstructure changes over time in the images.

The main camera is used to detect thin covers for the entire hand, usually made of rubber 1.1 The recorded images are analyzed for the typical distances between the mountains and valleys of the papillary structure shown. A cover that is provided with an artificial papillary structure is stretched differently when pulled onto a natural hand in different parts of the hand, which leads to locally different distances.

According to a second exemplary embodiment of a device according to the invention, not shown in the drawings, the second active means contains at least one first distance sensor 10. The at least one first distance sensor 10.1 is in the frame 5 arranged and aligned so that a measuring beam emanating from it is parallel to the object plane 1.3 into the recess 6th is directed.

Alternatively, the universal active agent contains, as in 3 shown, in addition to the at least one first distance sensor 10.1 , at least one second distance sensor 10.2 from the side of the main camera 1.1 , preferably in the housing 4th arranged on the object level 1.3 is directed. There can be further first and / or in particular second distance sensors 10.1 , 10.2 to be available. This enables more precise localization in the radial direction, for example with two second distance sensors radiating in the opposite sense of direction 10.2 , possible, as in 3 shown. If the measured distances to the hand are the same, it can be concluded that the hand is in the radial direction in the middle of the recess 6th is arranged.

Via several second distance sensors 10.2 the inclination or curvature of the hand (hand position) can also be recorded.

From a procedural point of view, knowledge of the spatial arrangement of the respective first and second distance sensors 10.1 , 10.2 and the measured distance values each form differences, and via the output unit 7th Instructions are issued, compliance with which leads to a reduction in the differences.

The instructions can advantageously be acoustic in nature by z. B. a tone is changed in its frequency. Thus, a user intuitively understands the increase in frequency as approaching a goal, such as the target position, and the transition to a continuous tone as reaching the goal. It is advantageous in the at least one of the distance sensors 10.1 , 10.2 A color detector is integrated, with which the measuring beam reflected back from the skin or the forgery is color-analyzed in order to determine whether its spectrum can actually be traced back to the reflection of the measuring beam on a natural hand.

According to a third embodiment of the device according to the invention, not shown in the drawings, the second active means contains two first light barriers 11.1 that are a first pair of light rays 11 form. You are in the frame 5 , advantageous in the object level 1.3 radiating and mirror-symmetrical to one through the optical axis 1.0 running parallels to the insertion direction of the hand are arranged so that the light barriers 11.1 radiated light rays converge.

Will one hand in the direction of insertion into the recess 6th The first two light barriers are inserted in the middle 11.1 interrupted at almost the same moment. A time difference results from the different lengths of the little finger and index finger. Knowing this typical difference, which is not significantly different for the two hands of a user, is advantageous, as in FIG 4a and 4b shown, a second pair of light barriers 12th , with second light barriers 12.1 that are parallel to the first two light barriers 11.1 radiate and to the first pair of light barriers 11 are arranged offset in the insertion direction. When the left or right hand is introduced, a different pair of light barriers is activated 11 , 12th switched active, with which the light barriers 11.1 , 12.1 interrupted with a shorter time interval, provided the hand was inserted exactly in the middle.

In terms of the process, the user repeatedly guides his hand in the direction of insertion into the frame 5 one to the light beams at the activated light barrier 11.1 , 12.1 are interrupted. The light beams can be interrupted again and again by a slight forward and backward movement, whereby the time interval between the interruptions approaches a minimum due to a simultaneous lateral movement. Reaching the minimum indicates that the target position has been reached in the radial direction.

In principle, it is advantageous if the output unit 7th , regardless of the implementation of the first and second active means or the universal active means, is a display. Instructions such as intuitive guidance, specific feedback in the event of error detection and other information can be conveyed to the user in a pleasant manner via the display.

For example, feedback about the correct hand posture and hand position can be given via a display with a very low latency or the user can be given symbolic instructions on this be granted. Furthermore, a correct hand posture can be shown on the display by a 3D target hand in order to animate the user to bring his hand, the image of which is also preferably shown in different colors in 3D, into spatial correspondence with the 3D target hand. If it is difficult for the user to see how well the image of his hand is positioned, the color of the image of his hand or the 3D target hand can also be continuously changed, e.g. B. from orange to green. The remaining deviation from the correct positioning and hand posture, the target position, can also be displayed. As an alternative to such a 3D user guidance, pictograms can also be used for user guidance.

According to a fourth exemplary embodiment of a device according to the invention, the universal active means contains a projector 13th , please refer 5 that is on one of the main cameras 1.1 facing away from the object plane 1.3 is arranged and a two-dimensional pattern in the direction of the recess 6th projected. The pattern is like this in the recess 6th projects that, when the selected surface area is in the target position, it is completely and sharply imaged on the hand. A sharp image is understood here to mean an image quality which deteriorates in each case with an axial movement of the hand in an opposite sense of direction. The pattern can advantageously be formed by lines that are visible to the user in the middle of the fingers when the hand is held correctly. Instead of lines, symbols such as smileys, for example, can be projected onto the fingers, which, for example, change color when the correct position is reached, when the fingers are in the target position. With a simple projection of a two-dimensional pattern, a radial and an axial guidance can take place and at the same time it can be shown to the user whether the fingers are already in the desired position, whereby the pattern also functions as the output unit 7th , to provide feedback about the respective actual position of the hand.

According to a fifth exemplary embodiment of a device according to the invention, this contains, as in FIG 6th shown an ultrasonic transducer 14th , which has noticeable pressure points within the frame 5 a contactless haptic is generated that suggests a virtual surface to the user on which he places his hand in order to position it in the target position. The ultrasonic transducer 14th is at an angle below the object level 1.3 arranged to create an effective non-contact feel under the surface area to be recorded. Additional ultrasonic transducers can be used as an option 14th above the object level 1.3 and / or in the frame 5 be arranged integrated. The at least one ultrasonic transducer 14th consists of an array of several individually controllable ultrasonic wave generators 14.1 that, where they interfere with each other, generate noticeable haptic feedback in the room. The first and second active means or the universal active means, for example the auxiliary camera, are used for control 9 is, the respective actual position is determined, to the computing and control unit 3 and the at least one ultrasonic transducer is guided as a function of the detected actual position 14th controlled accordingly.

With the integration of a haptically perceptible, virtual surface in the room, the target position for the surface area to be recorded can be reproduced in the axial and radial directions. If the surface area leaves the target position, the at least one ultrasonic transducer can 14th The pressure exerted on the surface area can be increased in order to intuitively move the user back into the target position.

The haptic feedback can also be presented to the user selectively. If he holds his hand curved during the image acquisition, more pressure can be generated on the downward-facing parts of the hand (e.g. fingertips and palm), with which the user intuitively extends the hand.

By increasing the number of pressure points per area on the surface area, it can be suggested to the user that the hand is approaching the target position.

Optionally, the non-contact haptics can scan the surface area with a specific, changing frequency. The noticeable pressure points then scan the fingertips or the palm of the hand with the changing frequency, the frequency changing depending on the deviation from the target position. For example, the fingertips or the palm of the hand can feel a pressure point through the ultrasound array every second. If the hand approaches the target position, the frequency increases, for example the palm is then scanned with 10 pressure points per second. Approach feedback to the user is thus implemented.

The haptic feedback can also be coordinated with a feedback on a display as an output unit. A rotating clock can, for example via the display and / or symbols projected onto the hand, visually suggest that the image of the surface area is currently being recorded by the main camera 1.1 runs. At the same time, circling, non-contact haptics on the surface area can support this effect and thus make the status of the image recording clear to the user, for example “image recording not yet started”, “current Image acquisition in progress ”or“ Image acquisition is finished ”. This visual representation can alternatively also be made by means of the projector instead of on the display 13th can be displayed directly on the hand.

When using an ultrasonic transducer 14th , the effect of the creation of a slight pressure on the surface area can advantageously also be used to increase the image quality. By indenting the surface area in an individually adapted manner, the 3D shape of the surface area given by the papillary structure is reshaped in the 2D direction, which, especially when the depth of field is only narrow 1.2 , larger areas of the surface area are in the target position and can be recorded, since a finger can be pressed flat, for example. The conversion into a final 2D image can also be done more quickly. In order to select the correct point in time for the image acquisition, the 3D image acquisition is correspondingly synchronized with the ultrasonic pulse generation.

The ultrasonic transducer can also 14th can be used advantageously for counterfeit detection. If a forgery is suspected, various pressure points and / or pressure areas are generated which would trigger a certain action in a human or natural surface area, since the person feels the pressure point. If a counterfeit is on the surface area or if a counterfeit cover is worn over the hand, the haptic feedback is not perceived. Recognition is conceivable via an interaction via the display by asking how many pressure points can be felt, or whether a pressure point moves clockwise or counterclockwise, or whether it moves to the left / right or up / down to determine whether a fake one or natural surface area is presented to the device for image acquisition of 3D skin impressions. As a particularly advantageous intuitive interaction option, it is proposed that the user should move his hand or fingers away from the direction from which the pressure points act. In this case, the perception of the pressure is checked in that the user reacts to the signal in a defined time window after it has been generated.

The at least one ultrasonic transducer 14th is below the object level 1.3 arranged. More ultrasonic transducers 14th can be above or inside the frame 5 be arranged. Several ultrasound transmitters are advantageous 14th in space to the recess 6th distributed, arranged so that pressure can be exerted on the hand from different sides.

According to a sixth exemplary embodiment of a device according to the invention, not shown in the drawings, is comparable to that of the ultrasonic transducer 14th functions, a compressed air generator with a large number of controllable nozzles is available. Through the targeted control of the individual nozzles, the hand can be guided or motivated to move, which may prove that it is a natural hand.

List of reference symbols

1

Image capture unit

1.0

optical axis

1.1

Main camera

1.2

Depth of field

1.3

Object level

2

Lighting unit

3

Computing and control unit

4th

casing

5

frame

5.1

edge

6th

Recess

7th

Output unit

8th

frame

9

Auxiliary camera

9.2

Depth of field of the auxiliary camera

OF1

Object field of the main camera

OF9

Object field of the auxiliary camera

10.1

first distance sensor

10.2

second distance sensor

11

first pair of photocells

11.1

first light barrier

12th

second pair of light barriers

12.1

second light barrier

13th

projector

14th

Ultrasonic transducer

14.1

Ultrasonic wave generator

R.

Direction of insertion

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 2018/0330142 A1 [0005]
• US 2015/0208059 A1 [0006, 0008]
• US 2020/0202101 A1 [0010, 0012]

Claims (8)

Device for contactless optical imaging of a selected surface area of a hand of a user, with - a housing (4) in which an image acquisition unit (1) containing a main camera (1.1) with an optical axis (1.0) and a lighting unit (2) is accommodated - a control and computing unit (3), - an output unit (7), - a frame (5) arranged outside the housing (4) and connected to the housing (4) via a frame (8), with edges (5.1 ) which delimit a recess (6) open on one side, which is open frontally to a user position of the user and in which the surface area, occupying an actual position, is to be positioned by the user, with an object plane (1.3 ) the main camera (1.1) is arranged with a depth of field (1.2) in which there is a target position for the surface area, characterized in that - either a first active means for localizing the Actual position in the axial direction of the optical axis (1.0) and a second active means for localizing the actual position in the radial direction of the optical axis (1.0) - or a universal active means for localizing the actual position in the axial and radial directions the optical axis (1.0) are present in order to localize the actual position in relation to the optical axis (1.0) in the axial direction and in the radial direction, to guide the user iteratively by means of the output unit (7), the surface area in the axial and radial directions To move the direction from the actual position to the target position, so that at least one image of the surface area in the target position can be recorded by means of the main camera (1.1). Device according to Claim 1 , characterized in that - the universal active means contains an auxiliary camera (9) which, compared to the main camera (1.1), has a larger object field (OF ₉ ) and a lower resolution in order to compare and analyze images of low resolution taken one after the other whether the movement towards the target position is superimposed by trembling movements or pulsation of blood vessels, so that a real hand can be distinguished from an unreal hand, whereby - the object field (OF ₉ ) of the auxiliary camera (9) and the object field (OF ₁₀ ) of the Main camera (1.1) lie in the object plane (1.3) of the main camera (1.1). Device according to Claim 1 , characterized in that - either the second active agent contains at least one first distance sensor (10.1) which emits parallel to the object plane (1.3), - or the universal active agent contains at least one first distance sensor (10.1) and at least one second distance sensor (10.2) which emits at an angle not equal to 0 ° to the at least one first distance sensor (10.1), in order to irradiate the surface area with light of at least one wavelength or to direct a measuring beam with at least one wavelength onto the surface area and one from the surface area as a result of the light absorption to analyze the light component reflected by blood vessels for a spatial structuring of one wavelength or light with more than one wavelength or for the amount of the reflected light component. Device according to Claim 1 , characterized in that the second active means contains two first light barriers (11.1) which form a first pair of light beams (11) and, emitting in or parallel to the object plane (1.3), enclosing an angle not equal to zero with one another, mirror-symmetrical to one through the Optical axis (1.0) running parallels to an insertion direction (R) of the hand are arranged in order to irradiate the surface area with light of at least one wavelength or to direct a measuring beam with at least one wavelength onto the surface area and one reflected from the surface area as a result of the light absorption by blood vessels To analyze the light component for a spatial structuring of one wavelength or light with more than one wavelength or for the amount of the reflected light component. Device according to one of the Claims 1 until 4th , characterized in that the output unit (7) is a display. Device according to Claim 1 , characterized in that the second active agent or the universal active agent is a projector (13) which is arranged on a side of the object plane (1.3) facing away from the main camera (1.1) in order to create a pattern in the recess (6) project that the pattern on the back of the user's hand - either completely and sharply depicted - or that the pattern is changed in its color or its resolution when the user moves the hand within the frame into the desired position. Device according to one of the Claims 1 until 4th , characterized in that the output unit (7) contains an ultrasound transducer (14) which is suitable for generating haptically perceptible pressure points on a virtual plane which corresponds to the nominal position in the axial direction. Device according to Claim 1 , characterized in that the output unit (7) contains a compressed air generator with a planar arrangement of nozzles which are directed into the recess (6).

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