WO2013178789A1 - Portable optical document reading device - Google Patents

Description

 PORTABLE OPTICAL DOCUMENT READING DEVICE

FIELD OF THE INVENTION

 The present invention relates to a portable optical reading device.

 It finds particularly advantageous application for the optical reading of images or characters on a secure document, such as an identity document.

STATE OF THE ART

 Optical reading devices are conventionally known, in particular bar code readers, which are portable.

 The optical reading of images or characters on a document supposes that one has a clear enough image of it to allow the recognition of the characters which it carries.

 It is therefore necessary to be able to correctly position the document in the depth of field of the optical reading device.

 One solution to achieve this is to use autofocus cameras, which provide a clear image for a large range of acquisition range. Such a camera with automatic focus is sometimes associated with a sighting system with projection of a single line or a rectangle or cross that allows to frame the area to be acquired in the field of the camera.

 Another solution is also to use a video return on a screen, so as to allow the user to correctly frame the document. The user then uses the information displayed on the screen to adjust the distance of the device vis-à-vis the document carrying the characters to acquire.

 Such solutions, however, correspond to expensive and sometimes cumbersome technologies.

Yet another solution is to equip such a reading device with an image processing which detects in real time the presence of a document at the good depth of field. The responsiveness and ergonomics of such a device is, however, very limited.

 Devices are also known, for example that described in patent US Pat. No. 5,598,007, comprising a pair of optical sources producing light beams which intersect at a defined distance from the object so as to form an image indicating to the user that the detector is positioned at a suitable distance from the object. Such a device makes it possible to indicate to the user that the detector is at the focal length of the document. On the other hand, when the detector is not at the focal distance of the document but close to it, it does not indicate to the user whether the device is positioned in the depth of field of the detector.

 SUMMARY OF THE INVENTION

A general object of the invention is to provide a portable optical reading device which does not have these disadvantages.

 In particular, the invention provides a portable type of optical reading device, which allows the user to adjust by itself, easily, the relative position of the document to read and the optical reading device.

 More specifically, the invention proposes a portable optical reading device for the optical acquisition of images or characters appearing on a document, comprising:

 a gripping support by which it is held during an acquisition and

an image acquisition system integrated into said support, this device furthermore comprises two non-divergent narrow light beam emission sources, said sources being arranged on the portable support so that there is at least one point of intersection said beams in the depth of field of the image acquisition system. The user can then adjust the position of the device relative to the document carrying the characters according to the relative position of the beam projection figures emitted by the light emitting devices on the document.

DESCRIPTION OF THE FIGURES

Other objectives, characteristics and advantages will come out of the detailed description which follows with reference to the drawings given by way of non-limiting illustration, among which:

 FIG. 1 illustrates an example of a portable remote optical acquisition device for images or characters according to the invention arranged facing a security document according to the invention;

 FIGS. 2a, 2b, 2c are three-quarter views of another example of a device according to the invention arranged facing a security document according to the invention;

 FIG. 2d schematically represents the optical and geometrical parameters of an optical reading system according to the invention;

 Figures 3 and 4 illustrate two embodiments corresponding to two possible variants for the device of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE EMBODIMENTS In the exemplary embodiment described in FIGS. 1 to 4, a portable reading device 1 makes it possible to read images or characters carried by a document 2 which is for example a document security, such as an identity card or a passport, or a badge giving access to one or more secure areas. The device 1 is in the form of a cock 3 of a parallelepipedal format easily manipulated manually by a user, for example a shell of a plastic material of a format similar to that of a mobile phone.

 This shell 3 is for the device 1 a gripping support. It incorporates an image acquisition system 4, consisting for example of a matrix detector and an input / output optics. The format of the cock 3 allows the user to easily orient the axis of the image acquisition system 4.

 The shell 3 also includes two sources 5 of light beams. These beams are narrow non divergent beams. The wavelength or wavelengths of the two sources are (or are) preferentially in the visible range.

 The emission sources 5 are arranged on the support 3 for gripping so that there is at least one point of intersection of said beams in the depth of field of the image acquisition system 4.

 The orientations of the sources 5 are in particular chosen so that the projection patterns of the beams on the document 2 overlap when the document 2 and the image acquisition system 4 are at a distance allowing the acquisition of the image or characters in document 2.

 These orientations are in particular advantageously chosen so that the point or line of intersection of the light beams is located at the focal length of the image acquisition system 4. In this way, the projection patterns of the beams on the document 2 are superimposed only when the image acquisition system 4 is at a distance from the document 2 allowing an optimal acquisition of the characters carried by the document 2.

In the example of the figures, the beam emission sources 5 are arranged symmetrically on the support 3 on either side of the optical axis AO of the image acquisition system 4. The light beams form an angle of between 3 ° and 10 °, and preferably between 8 ° and 9 ° with respect to the optical axis A0 of the image acquisition system 4. The distance between two sources 5 is between 20 and 70 mm and preferably between 55 and 60 mm. In this way, the two beams coming from the sources 5 intersect at a distance from the image acquisition device 4 which is the focal length of the system 4 and which is 200 mm. Note that such a distance is perfectly compatible with the fact that the user can hold the device 1 with one hand and the document 2 with the other.

 The emission sources are, for example, laser diodes or light-emitting diodes which are robust and inexpensive elements.

 They can be punctual. They can also emit each, as shown in the figures, a beam whose projection along a plane transverse to its direction of propagation is a line segment. For this purpose, the reading device 1 comprises, in front of the sources 5, diffractive means, in particular slots having a width of the order of magnitude of the wavelength of the radiation emitted by the sources.

 In this case, the slots of the two sources may be parallel to each other, so that said segments are parallel to each other.

 Furthermore, these slots may be parallel or perpendicular to the main direction in which the support extends so that the segments of the projected light beams are parallel or perpendicular to the main direction in which the support extends.

 The projection lines of the sources on the document 2 then also allow the user to adjust the parallelism of the document 2 with respect to the device 1.

Document 2 itself comprises, in addition to a reading zone 21 where the characters to be read by the device are located, a marking 22, comprising for example two parallel lines, defining an identification zone 23 which includes the zone of 21. Alternatively, the marking may be a rectangle surrounding the zone 21. The zone 23 for identifying the reading zone advantageously has a band shape. The height h and width I of the identification zone 23 are adapted to the quantity of characters to be read, for example approximately 20 mm and 120 mm, respectively.

With reference to FIGS. 2b to 2d, the identification zone 23 defined by the two lines 22 constitutes the zone in which the points or lines of projection of the light beams emitted by the sources 5 must be located so that the acquisition can take place. with enough sharpness of images. When these points or projection lines are in this band, it means that the document 2 is correctly positioned with respect to the optics of the acquisition system, that is to say that the document is located in the depth of field of the acquisition system, ie at a distance from the acquisition system lying between the limits of said depth of field, delimited by two extreme distances corresponding to the first (distance d _m in, FIG. 2c) and last (distance d max, FIG. 2b) net plans that the system 4 can acquire.

 As indicated above, the projection patterns of the light beams according to a plane orthogonal to their propagation are advantageously parallel lines, these lines being merged with the focal length df of the acquisition device.

 In this case, when on document 2, the parallel lines formed by the projection sources 5 are merged, this indicates to the user that the document is in an optimal position with respect to the acquisition system, that is, ie parallel to it and in its focal plane.

 If the parallel lines are distinct but both in the marking band, this means that the document is close to the focal plane of the acquisition system, in the depth of field of the acquisition system, making it possible to acquire an image net of characters.

These properties are obtained by adapting the angle of inclination of the light beams with respect to the optical axis AO of the acquisition system 4, and the height h of the identification zone 23 on the document as a function of the optical characteristics and the geometric configuration of the acquisition system.

The optical characteristics include the depth of field, and more specifically the distances d _m in and d _ma x net first and last planes compared to the acquisition system, and the focal length f of the system.

By way of non-limiting example, using an acquisition system whose focal length is about 170 mm from the device, and the distances d _m in and d _ma x are respectively about 150 and 200 mm from the system.

 The geometrical configuration of the reading device notably comprises the positions of the light beam emission sources with respect to the acquisition system. For example, the sources 5 are located on either side of the system, at a distance e thereof of between 25 and 30 mm.

 With reference to FIG. 2b, there is in this case the following relation:

 e

 tan a = -

 df

 With the values given as examples, an angle advantageously between 8 and 9 ° is thus obtained.

 Concerning the identification zone 23, its height h indicates to the user the maximum spacing of the projection patterns of the light beams so that the acquired image is clear. Therefore this spacing - and therefore the height h - must be less than or equal to the spacing of the light beams when the document is placed at the first and last net planes that the acquisition system must acquire, as shown in Figures 2b and 2c.

 In a particular case (limit case), the height h corresponds to the spacing of the projection patterns of the light beams when the document is placed at the first and last net planes that the acquisition system must acquire.

 We then obtain the following relations:

 h h

 tan a =

21 df d _m i _n | 21 d _max df \ With the values given as examples, the height of the identification zone 23 is advantageously between 8 and 9 mm.

 However, in order not to force the user to position the device 1 in a very specific manner, the chiller of the system advantageously extends beyond the limit positions of the document for which the spacing of the FIGS. projection of the beams is equal to the height of the identification zone 23.

 When the emission is in the visible range, the operator can trigger the acquisition himself, when he sees the points or lines of the beam in the band 23, for example by pressure or contact on a trigger button 6 (Figure 3).

 It should be noted that the sensors of the image acquisition system 4 can be chosen to be sensitive to wavelengths different from those of the source radiation, so that the projection patterns of the sources 5 on the document are not detected by the image acquisition system 4.

 The device 1 may then comprise (FIG. 4) a second image acquisition device 7 which, unlike the first image acquisition device 4, is sensitive to the radiation emitted by the sources 5. This second device 7 of FIG. acquisition of images acquires continuously or periodically an image of the document 2 and automatically triggers the acquisition of the first image acquisition device 4 when it detects the presence of the source projection figures 5 on a defined area 23 of the document 2 containing the zone 21 of machine readable information.

 Such a device is used, for example, as follows.

 The user holds the shell 3 of the device 1 in his hand as he would hold for example the shell of a mobile phone.

It can thus easily orient the optical axis AO of the image acquisition system 4. It then directs the device 1 opposite the document 2 by positioning the optics of the system 4 in front of the information zone 21 to bind on the document 2.

 The beams emitted by the sources 5 are then incident on the document 2. The user can then adjust the distance between the document 2 and the device 1 so as to adapt the position of the projection figures of the different incident beams relative to the zone 21 of document 2.

 In particular, it positions the reading device 1 with respect to the document 2 so that the points or projection lines of the beams are found in the zone 23 identified by the markings 22 on the document 2.

 Advantageously, it positions the reading device 1 with respect to the document 2 so that the points or projection lines are merged in the zone 23, this corresponding to the optimal positioning of the document 2.

 When he finds that this adjustment is made, the user triggers the image acquisition device 4 by actuating the control button 6.

 In the case of the embodiment of FIG. 4, it is the acquisition by the device 7 sensitive to the radiation emitted by the sources 5, of an image in which the points or projection lines of the sources 5 appear in the zone 23 of document 2 which automatically triggers the image taken by the system 4.

Claims

1. Optical image or character reading system, comprising a portable optical reading device (1) comprising - a gripping support (3) by which it is held during an acquisition and - an image acquisition system (4) integrated into said support (3), two sources (5) for emitting narrow, non-diverging light beams, said sources (5) being arranged on the portable support (3) so that there is at least one point of intersection of said beams in the depth of field of the image acquisition system; the system being characterized in that it further comprises a document (2) to be analyzed comprising a machine-readable information zone (21), and a marking (22) identifying a zone (23) comprising said information zone information, and in which the projection figures of the beams of the reading device must be located so that the image acquired by the device of said information is clear. 2. System according to claim 1, in which the point of intersection of the light beams is located at the focal distance of the image acquisition system (4). 3. System according to one of claims 1 or 2, in which the inclination of the light beam emission sources relative to the optical axis (AO) of the image acquisition system (4), and the height of the zone (23) identified by the marking (22) are configured so that the height of said zone is less than or equal to the spacing of the projection figures of the light beams on the document (2) when it This is at the first and last sharp plane of the depth of field of the image acquisition system (4). System according to one of claims 1 to 3, in which a light beam forms an angle of between 3° and 10° relative to the optical axis AO of the image acquisition system (4). System according to one of the preceding claims, characterized in that the emission sources (5) each emit a beam whose projection along a plane transverse to its direction of propagation is a point, a segment or a straight line. System according to claim 5, characterized in that the straight lines or segments resulting from the projection of the beams emitted by the light sources (5) along a plane transverse to their direction of propagation are parallel to each other. System according to one of claims 5 or 6, characterized in that said straight lines or segments are parallel or perpendicular to the main direction in which the support (3) extends. System according to the preceding claims, characterized in that the sources (5) comprise laser diodes or light-emitting diodes. System according to the preceding claim, characterized in that the sources (5) emit radiation in the visible range to which the image acquisition device (4) is not sensitive. 10. System according to the preceding claim characterized in that the device (1) further comprises a second image acquisition device (7) sensitive to the radiation emitted by the sources (5) and capable of detecting the presence of the figures of projection of the sources (5) onto the document (2) and triggering the acquisition of the first image acquisition device (4). 1 1. Method for remotely acquiring images or characters of a document, implemented by a system according to one of the preceding claims, according to which: - the optical reading device (1) of the system is positioned facing a machine-readable type information zone of the document (2) of said system, so that the beams emitted by the device (1) are incident on the document (2) and the image acquisition system (4) faces the machine-readable type information zone, - the distance between the document (2) and the device (1) is adjusted so that the projection figures of the beams are arranged in the area of the document (2) to be analyzed in which they must be located for the acquired image said information is clear, and - when this adjustment is made, the image acquisition device (4) is triggered, the device being held by its gripping support (3) during all of these steps. 12. Optical reading device (1) for the optical acquisition of images or characters appearing on a document (2), comprising: - a gripping support (3) by which it is held during an acquisition and - an image acquisition system (4) integrated into said support (3), - two sources (5) for emitting narrow, non-diverging light beams, said sources (5) being arranged on the portable support (3) so that there is at least one point of intersection of said beams in the depth of field of the image acquisition system; characterized in that it is suitable for implementing the method according to claim 1 1. 13. Security document (2), characterized in that it is adapted to the implementation of the method according to claim 1 1 and bears a marking identifying the zone in which the projection figures of the beams must be found so that the The acquired image of said information is clear, this area integrating the machine-readable information area.