WO2001099042A1

WO2001099042A1 - Device for biometric applications

Info

Publication number: WO2001099042A1
Application number: PCT/SE2001/001393
Authority: WO
Inventors: Alf Larsson
Original assignee: Precise Biometrics Ab
Priority date: 2000-06-20
Filing date: 2001-06-20
Publication date: 2001-12-27
Also published as: SE0002298L; SE523463C2; AU2001266473A1; SE0002298D0

Abstract

A printed board assembly for biometric applications, comprising a sensor (12) and a printed circuit board (11), which has two parallel flat sides, of which one constitutes a carrying surface (14) which is adapted to carry electronic components (16). The printed board assembly is characterised in that the sensor (12) is arranged on an edge surface (13) of the printed circuit board (11) between the two parallel flat sides, the extent of the sensor (12) at right angles to the carrying surface (14) being comparable as to size with the thickness of the printed circuit board (11).

Description

DEVICE FOR BIOMETRIC APPLICATIONS

Field of the Invention

This invention concerns a printed board assembly for biometriσ applications and a fingerprint reader which has such a printed board assembly. Background Art

Fingerprints can be inputted automatically in a number of different ways, for instance by using optical, thermal or capacitive sensors. Since the optical ones only record a two-dimensional image of an object, in this case the fingertip, it is easy to deceive these fingerprint readers . Sometimes this can be done by simply placing an image of a fingerprint over the sensor, which in most cases is a CCD camera, and then this image is recorded as the current fingerprint. It is considerably more difficult to deceive capacitive or thermal sensors, i.e. sensors measuring the capacitance or the temperature of the object that is placed over it. A requirement to obtain good reading is that the finger comes into close contact with the sensor. It must be pressed against the active surface of the sensor to result in as good a recording as possible. Since the sensor therefore must be accessible from the outside, through the casing which accommodates the fingerprint reader, this places certain demands on the mounting of the reader in the casing. The reader must be arranged in immediate connection with the surface through which the sensor is to be accessible.

For reasons of cost and space, the sensor is in most cases mounted on a printed circuit board which also carries electronics for inputting and processing of data from the sensor. For the casing to be sufficiently close to the sensor to allow it to be easily accessible through the casing, the sensor must either be raised from the remaining electronics, or the remaining electronics must be lowered into the printed circuit board. Making a socket or the like to raise the sensor is costly and requires space and is thus most undesirable. It is also expensive to lower the electronics into the printed circuit board. Moreover, the fact that the sensor must be accessible through the casing places demands on the location of the board that carries the sensor. Since most electrical appliances must be easy to handle and not be bulky, it is therefore in most cases difficult to determine how and which means are to be made accessible through the casing, so that the final product will be as convenient and inexpensive as possible. In most cases different standard components are mounted on different printed circuit boards, and since the printed circuit boards frequently conceal each other's components when, according to prior art, they are mounted adjacent to each other and one above the other in casings, this results in expensive, specially designed printed circuit boards. Other problems associated with sensors that are mounted in openings according to prior art are, for instance, that it is difficult to prevent radiation through the opening, which may disturb the surroundings and also interfere with the components of the device accommodated in the casing. Moreover, dirt and particles of various kinds may easily enter through the opening, which may jeopardise the function of the device.

There is thus a need for an improved carrier of electronic components, such as sensors, and a device in which sensors are mounted, which solve the problems that have been described above.

Summary of the Invention

An object of this invention is to provide a printed board assembly carrying a sensor, which is easy to mount in a casing, so that the sensor will be easily accessible through the casing in a manner that eliminates the problems described above. Another object of this invention is to provide a device for fingerprint reading which does not suffer from the above problems.

One more object of this invention is to provide a device for fingerprint reading, which enables better screening of radiation through the opening in the casing through which the sensor is accessible.

A further object of this invention is to provide a device for fingerprint reading which easily allows minor variations in reading of one and the same finger on different occasions.

These objects are achieved by a printed board assembly and a device for fingerprint reading according to the appended claims . According to one aspect of this invention, a printed board assembly for biometric applications is provided, comprising a printed circuit board having two parallel flat sides, of which at least one constitutes a carrying surface which is adapted to carry electronic components, and a sensor. The printed board assembly according to the invention is characterised in that the sensor is arranged on an edge surface of the printed circuit board between said two parallel flat sides, the extent of the sensor perpendicular to the carrying surface being comparable as to size with the thickness of the printed circuit board. Such a printed circuit board can easily be mounted in a casing, so that the narrow sensor can easily protrude through, for instance, a slot in the side of the casing. The designers then need not pay much attention to the order in which the printed circuit board is arranged in relation to other printed circuit boards. The entire construction can be made flatter and more compact since such a printed circuit board can be arranged closer to other printed circuit boards and casings than the print- ed circuit boards which according to prior art have the sensor on the carrying surface . Preferably the sensor is designed so that its width is up to twice its thickness. This gives the advantage that the sensor can easily be mounted on the edge of the printed circuit board. Preferably the active surface of the sensor is arranged at right angles to the carrying surface. This gives the advantage that the sensor can easily be made accessible through an opening in a casing.

The printed circuit board has preferably a projec- tion on which the sensor is mounted. Such a projection makes it easier to insert the sensor in a slot or opening in the casing and also to close the opening round the sensor so that dirt and the like cannot penetrate into the casing. Moreover, screening of the printed circuit board against radiation is facilitated, and it will also be easier for the designers when designing the casing and planning how the printed circuit boards are to be arranged in the casing since the main part of the printed circuit board need not be quite close to the casing. Preferably, the printed circuit board also carries components for processing of data from the sensor, resulting in saving of space, lines and contact means which are expensive.

Alternatively, the sensor can be mounted on a print- ed circuit board, which is often smaller and which does not carry a considerable amount of logics, but the printed circuit board is connected to a second main board which carries the necessary electronics for processing of data from the sensor. This gives the advantage that the sensor can be mounted on a smaller printed circuit board which in some cases is easier to place in a casing when high demands are placed on the design of the casing or the device .

Preferably, also image processing is included in the processing of the sensor data. In this manner, additional printed circuit boards which have image processing means can be avoided, thus lowering the total cost of appli- ances that use printed board assemblies with sensors for biometric fields of application according to the invention.

According to one aspect of the invention, a device for fingerprint reading is provided, comprising a casing which accommodates a sensor and a printed circuit board which has two parallel flat sides, of which at least one flat side is a carrying surface which is adapted to carry electronic components for processing of sensor data. The device is characterised in that the sensor is mounted on an edge surface of the printed circuit board between the two parallel flat sides.

This gives the advantage that the device can be made narrower and the construction and planning for the device will be easier since less importance need be attached to the location of the printed circuit boards included. This reduces the cost of the device.

Preferably, the sensor is arranged in an opening in the casing, which opening is comparable as to size with the sensor. This makes it easier to let, for instance, strips fit tight round the sensor, thus preventing dirt and other particles from penetrating into the device.

Preferably, at least one route is arranged, i.e. an electric conductor extending through the printed circuit board between said parallel flat sides at the opening. These routes serve as a screening grating for radiation through the casing. /

The arrangement of routes at the opening is advantageously combined with a projection on the printed cir- cuit board.

This gives the advantage that it will easier to arrange the routes without affecting the other electronics of the printed circuit board, and that the routes will be closer to the opening. The casing is preferably formed with a depression round the opening for the sensor. This depression can then be used to guide a person's finger over the sensor, which facilitates the fingerprint reading to a considerable extent since the variations in the location of the finger in connection with different readings of the same finger will be reduced. In order to further improve the fitting round the sensor, the casing is preferably formed in at least two parts. Since these two parts can be clamped round the printed circuit board, a more accurate fitting can be made, which results in better protection against dirt and also facilitates screening of radiation through the opening since it is possible to squeeze the printed circuit board between the two parts of the casing, so that the opening will thus be well adjusted to the printed circuit board. Preferably, the carrying surface carries electronic components for processing of sensor data.

This gives the advantage that a smaller number of printed circuit boards is required in the device, which reduces the cost of the device. For reasons of handling, the sensor is advantageously arranged on a support, for instance a small intermediate board, when the sensor is very small or brittle. The support is arranged according to the invention on an edge surface of a printed circuit board or some other carrier.

It will be appreciated that the invention may be used also in other fields of application, in particular biometric fields, where similar requirements are placed on the device and on the screening of sensors . Of course, the above features can be combined in the same embodiment . Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings, in which Fig. 1 is a schematic view of a printed circuit board which carries a sensor according to prior art, Fig. 2 is a schematic view of a printed board assembly which carries a sensor according to an embodiment of this invention,

Fig. 3 is a schematic view of a printed board assem- bly which carries a sensor according to an alternative embodiment of this invention,

Fig. 4 is a schematic perspective view of a device for fingerprint reading according to a preferred embodiment of the invention, and Fig. 5 is an enlargement, seen from above on a level with the upper edge of the sensor, of a device according to Fig. 4.

Detailed Description of Embodiments according to this Invention Fig. 1 shows a printed circuit board 1 which carries a sensor 2 according to prior art. The sensor 2 is a capacitive sensor and its active surface 5 is fairly large (typically about 100 mm²) and thus occupies a great part of the carrying surface 4 of the printed circuit board 1. The sensor is mounted on a base 3 which is arranged on the carrying surface 4 of the printed circuit board 1. The function of the base 3 is to raise the sensor 2 so that its active surface 5 is on a level above the other components 6 which are carried by the printed circuit board 1 so as to make the sensor accessible through an opening in a casing (not shown) .

If a printed circuit board of the type described above is mounted in a casing with an opening for the sensor, the opening must be fairly large. Through this opening, electromagnetic radiation can radiate into and out of the casing.

It will be appreciated that also other types of sensor can be used and that they cause similar problems. Fig. 2 illustrates a printed board assembly accord- ing to the invention which has a printed circuit board 11 which on an edge surface 13 has a projection 17 supporting a narrow, thermal sensor 12. The width of the sensor is 0.4 mm (typically between 0.4 mm and 1.5 mm) and thus fits on the projection which typically is 1.2 mm in width. Since the sensor is so narrow, it is, for reasons of handling, mounted on a small intermediate board 18. The active surface 15 of the sensor is arranged at right angles to a carrying surface 14 which carries electronic components 16 for image processing of data supplied from the sensor. The arrangement of the sensor makes it easier for designers to place the printed circuit board in a casing since now the printed circuit board need not be arranged in a certain position, i.e. uppermost, for the sensor to be accessible from the outside of the casing. Moreover, the order between different printed circuit boards in a device which uses a printed board assembly according to the invention is not as important, since the sensor is now arranged on the side of a printed circuit board and is not concealed by another printed circuit board which is arranged according to prior art technique adjacent to the printed circuit board 11. It will be appreciated that the printed board assembly described above can also be formed without the projection 17 and/or without the intermediate board 18.

Fig. 3 illustrates an alternative embodiment of this invention. The sensor 22 is mounted on a projection 23 on a first printed circuit board 21 which can be very small (down to smaller than 1 cm²) . This first printed circuit board 21, which below will be referred to as daughter board, does not carry any electronic components in addition to the sensor and a flat cable 28, or some other connecting means such as a contact, which connects the sensor 22 on the daughter board 21 with electronic components on a second printed circuit board 29. The second printed circuit board 29, below referred to as the main board, carries the other electronic components 26 for processing of data supplied from the sensor 22 to the components 26 via the flat cable 28. As mentioned above, the daughter board 21 can be considerably smaller than the main board 29 and its main purpose is to be a carrier for the sensor 22 and facilitate mounting of the sensor 22 in spaces for which the main board 29 is too large but which can accommodate the daughter board 21. It will appreciated that the components 26 for processing of data from the sensor can perform image processing for fingerprint recognition, conversion of the data before transmission to other equipment or similar tasks . It will also be appreciated that the sensor can be of a type other than thermal as long as it has such an extent as to be suitable for mounting on the edge surface of a printed circuit board or some other carrier of electronic components, i.e. comparable as to size (the sen- sor is up to four times as wide as the thickness of the printed circuit board) .

Fig. 4 illustrates a device according to this invention for fingerprint reading which has a printed circuit board 31 on which components 36 for image processing are arranged. The printed circuit board 31 has a projection

33 on one of its edge surfaces, on which a narrow sensor 32 is mounted, which has an active surface 35. The sensor 32 is arranged in an opening 41 in a casing 40. The casing, which consists of two parts 40a and 40b, encloses the printed circuit board and protects it from dirt and also radiation. The casing 40 also screens the surroundings from radiation from the components that are mounted on the printed circuit board 31.

It will be appreciated that this casing 40 can also be the casing of e.g. a mobile phone, a laptop, a locking device such as locking and unlocking devices for cars, door locks, activation and deactivation units for alarms, a "set top box" for e.g. TV access or other devices for verification of a person liable for payment or a pur- chaser, and other handheld units.

The casing 40 is formed with a depression 42 at the opening 41, which depression is adapted to guide a per-

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It will be appreciated that many variations and modifications of the embodiments described above are feasible within the scope of the invention. It will also be appreciated that mounting of a sensor on the edge of a carrier is not restricted to mounting sensors for fingerprint reading, but can also be applied in other technical fields, especially in biometric applications.

Claims

1. A printed board assembly for biometric applica- tions, comprising a printed circuit board (11) having two parallel flat sides, of which at least one constitutes a carrying surface (14) which is adapted to carry electronic components (16) , and a sensor (12) , c arac t e r i s e d in that the sensor (12) is arranged on an edge surface (13) of the printed circuit board (11) between said two parallel flat sides, the extent of the sensor (12) at right angles to the carrying surface (14) being comparable as to size with the thickness of the printed circuit board.

2. A printed board assembly as claimed in claim 1, wherein the active surface (15) of the sensor (12) is arranged essentially at right angles to the carrying surface (14) .

3. A printed board assembly as claimed in claim 1 or 2, wherein the extent of the sensor (12) at right angles to the carrying surface (14) is at most four times as great as the thickness of the printed circuit board.

4. A printed board assembly as claimed in any one of the preceding claims, wherein the printed circuit board (11) has a projection (17) on an edge surface (13) , and the sensor (12) is mounted on an edge surface of the projection (13) .

5. A printed board assembly as claimed in any one of the preceding claims, wherein an electronic component (16) , which is intended for processing of sensor data, is arranged on the printed circuit board (11) .

6. A printed board assembly as claimed in claim 1,

2, 3 or 4 , which also comprises a main board (29), wherein the printed circuit board (11) is a daughter board (21) which with the aid of contact means (28) or a line

(28) is connected to the main board (29) which carries an electronic component (26) for processing of sensor data.

7. A printed board assembly as claimed in claim 5 or 6, wherein the electronic component (16, 26) is intended for image processing.

8. A device (50) for fingerprint reading, compris- ing a casing (40) accommodating a sensor (32) and a printed circuit board (31) which has two parallel flat sides, of which at least one flat side is a carrying surface (34) which is adapted to carry electronic components, c h a r a c t e r i s e d in that the sensor (32) is mounted on an edge surface of the printed circuit board (31) between the two parallel flat sides.

9. A device (50) as claimed in claim 8, wherein the sensor (32) is arranged in an opening (41) in the casing (40) , and the opening (41) of the casing (40) is compar- able as to size with the active surface (35) of the sensor.

10. A device (50) as claimed in claim 8 or 9, wherein at least one electric conductor (55) is arranged through the printed circuit board (51) between said parallel flat sides at the opening (41, 61) of the casing (40, 60) for screening of radiation through the opening (41, 61) .

11. A device (50) as claimed in any one of claims 8-10, wherein the outside of the casing (40, 60) is form- ed with a depression (42) at the opening (41, 61) for guiding a person's finger.

12. A device (50) as claimed in any one of claims 8-11, wherein the casing (40, 60) has at least two parts (40a and 40b, 60a and 60b) , of which at least one is formed with a recess at an edge, said recess constituting at least part of the opening (41, 61) .

13. A device (50) as claimed in any one of claims 8-12, wherein the carrying surface (34) carries electronic components which are intended for image processing of data from the sensor (32) .

14. A device (50) for fingerprint reading, comprising a casing (40) which accommodates a sensor (32) and a printed circuit board (31) which has two parallel flat sides, of which at least one flat side is a carrying surface (34) which is adapted to carry electronic components, c h a r a c t e r i s e d in that the sensor (32) is mounted on an edge surface of the printed circuit board (31) between the two parallel flat sides, and that the casing (40, 60) has at least two parts (40a and 40b, 60a and 60b) , of which at least one is formed with a recess at an edge, said recess constituting at least part of the opening (41, 61) .

15. A device (50) for fingerprint reading, comprising a casing (40) which accommodates a sensor (32) and a printed circuit board (31) which has two parallel flat sides, of which at least one flat side is a carrying surface (34) which is adapted to carry electronic components, c h a r a c t e r i s e d in that the sensor (32) is mounted on an edge surface of the printed circuit board (31) between the two parallel flat sides, the sensor (32) being arranged in an opening (41) in the casing (40) , and that the opening (41) of the casing (40) is comparable as to size with the active surface (35) of the sensor.