CN217486531U

CN217486531U - Planar scanner for implementing photometric stereo technology

Info

Publication number: CN217486531U
Application number: CN202220946413.9U
Authority: CN
Inventors: 西尔维亚·科拉格兰德; 马西莫·科拉格兰德; 洛伦佐·科拉格兰德
Original assignee: Luo LunzuoKelagelande; Ma XimoKelagelande; Xi ErweiyaKelagelande
Current assignee: Luo LunzuoKelagelande; Ma XimoKelagelande; Xi ErweiyaKelagelande
Priority date: 2021-10-28
Filing date: 2022-04-22
Publication date: 2022-09-23
Anticipated expiration: 2032-04-22
Also published as: DE202022100250U1; IT202100005123U1

Abstract

The utility model discloses a plane scanner (100), configured to implement luminosity stereo technology, include: scanning surface on which an object (O) to be scanned can be positioned

And an acquisition device (1) provided with a sensor (1a) for linear images, the sensor (1a) being configured to acquire an image of an object "O" along a scanning surface

A portion of the upper scan line (L) placement. The planar scanner (100) further includes a first pair of light sources extending parallel to the scanning line (L) and a second pair of light sources extending parallel to the scanning line (L). For each light source of the first and second pairs of light sources, the planar scanner (100) comprises an illumination unit (3) comprising a plurality of LED lamps (5) and a plurality of asymmetric lenses (3a) each associated with a respective LED lamp (5). The illumination unit (3) is configured for redirecting the light beam emitted by the light source on the scanning surface with a predetermined redirection angle.

Description

Planar scanner for implementing photometric stereo technology

Technical Field

The present invention relates to a planar scanner configured to implement photometric stereo techniques. In particular, the flat panel scanner according to the present invention is widely used in the field of image acquisition.

Background

It is known that photometric stereo techniques allow 3D information to be obtained starting from a set of color or grayscale images. Since this technique is particularly suitable for capturing fine details of mainly two-dimensional surfaces (such as, for example, paintings, bas-reliefs, marble slabs, etc.), while on the other hand, it is not possible to capture the shape of complex three-dimensional objects (such as, for example, bowls), it is designed to be implemented in scanners for planar images, in order to scan materials and surfaces, while returning color and 3D digital information.

It is known that photometric stereo techniques are implemented by illuminating an object located on a scanning surface with a plurality of light sources that can be selectively activated and acquiring an image representative of the object at each activation.

In order to implement photometric stereo techniques, use is generally made of a planar scanner comprising a scanning surface on which the object is located and a plurality of light sources in such a way that the object is illuminated from different directions.

The prior art scanner includes: an image sensor configured for acquiring an image about the object; and an optical system disposed between the image sensor and the scanning surface and aligned with the image sensor along a vertical axis perpendicular to the scanning surface.

In the above scanner, the light sources are switched on one at a time, and the image sensor acquires an image of the object and/or of a part of the object at each switching on.

Although photometric stereo techniques, unlike other 3D image acquisition techniques, do not require the use of dedicated 3D devices (such as, for example, confocal lasers, etc.) but allow information to be obtained in color and at a high level of detail, for optimal results it is necessary to arrange the light sources inside the scanner in such a way as to obtain at least four illumination directions that are sufficiently different from each other, and in such a way that the light generated by each light source can illuminate the object to be scanned in a uniform manner.

An example of a prior art scanner is provided in patent document EP 3210370, which shows a planar scanner comprising an optical system, a linear image sensor (that is to say a sensor capable of acquiring an image relating to a portion of an object placed along a scan line defined by a scanning surface), and first and second light sources located on either side of and extending parallel to the scan line.

In this case, to scan the object, the object is positioned on the scanning surface and the first light source is switched on. An image representing the object is then acquired. At the end of this operation, the first light source is switched off, while the second light source is switched on and the acquisition operation is repeated.

Since it is known that the higher the number of different directions in which the object is illuminated, the better the result, in prior art scanners with only two light sources the object is repositioned on the scanning surface in such a way that it is rotated by 90 ° with respect to the front direction. In this case, the irradiation operation by the first light source and the second light source and the corresponding acquisition and movement operations are repeated.

In this way, images of the object can be acquired when the object is illuminated from four different directions without increasing the number of light sources (and therefore the overall size of the scanner).

Disadvantageously, such scanners have several disadvantages. Alignment and processing of images acquired before and after a 90 ° rotation of the object is difficult. Furthermore, by rotating the object by 90 °, it is always possible to exceed the size of the scanning surface, thus requiring additional acquisition and subsequent operations to stitch the images.

Another drawback also derives from the fact that the object must be rotated manually, which makes the use of the scanner particularly inconvenient.

A partial solution to this problem is provided by a planar scanner having at least two light sources to which a light deflector can be removably applied in such a way as to redirect the direction of light emission at a predetermined angle.

In this case, a deflector is mounted on the light source in such a way as to deflect (or redirect) the light emitted by the light source. Then, the switching on of the light source and the corresponding operations for acquiring the image and for moving are alternately performed.

At the end of these operations, the deflector is removed, rotated and applied to the light source again in such a way as to flip with respect to the previous one. In this case, the switching on of the light source, the movement of the object over the scanning surface and the acquisition of the image are repeated.

By mounting the deflector on the light source (first oriented in one direction and then in the opposite direction), illumination of the object from at least four different directions can be obtained.

Disadvantageously, such scanners also have the disadvantage of requiring manual intervention to obtain different illumination directions. In this case, the scanner is particularly awkward and rather fragile, since there is a risk of breaking the deflector during removal and/or application of the deflector to the two light sources.

There are also prior art planar or planetary scanners, such as for example the scanner shown in patent document EP 3210370, in order to illuminate the object to be scanned from several different directions.

These scanners include first and second pairs of light sources, an optical system, and a linear image sensor. In this case, the light sources are switched on one at a time, and images of the portions of the object lying along the scan lines are acquired one at a time. Subsequently, the object (or, on the other hand, the optical system, the image sensor and the light source as a whole) is moved in such a way that: adjacent sections are placed step by step along the scan line and are thus acquired.

In these prior art scanners, the first pair of light sources are typically located on either side of and extend parallel to the scan line. The second pair of light sources is located substantially at the end of the scan line and extends in a direction transverse to the scan line.

Disadvantageously, in this case, even if the scanning surface is illuminated from four different directions, the second pair of light sources cannot illuminate the scanning line with a beam of light rays having a uniform angle of incidence on the scanning line and thus on a portion of the object placed there. The incident angle of the light ray striking the end of the scanning line closest to the light source that is turned on is larger than the incident angle of the light ray striking the end of the scanning line opposite to the light source.

This results in low quality of the acquired images and therefore poor scanning accuracy and poor accuracy of the digital reconstruction of the scanned object.

To overcome this drawback, planar scanners are known in which a second pair of light sources is located at the end of the scan line and extends along the scan line. In these scanners, the scan line to be illuminated is limited to a few centimeters, greatly simplifying the problem of how to illuminate uniformly from the end of the scan line. The first pair of light sources and the second pair of light sources are arranged substantially in a cross-like arrangement over the scanning surface. This type of scanner employs an unconventional telecentric optical system and x, y acquisition maps. In this case, a large object is scanned by acquiring adjacent sections (strips), which then have to be joined or coupled by software.

Disadvantageously, these scanners are expensive and complex to construct, and require very long acquisition times to acquire large format objects, especially when compared to conventional scanners based on conventional optics and large scan lines.

SUMMERY OF THE UTILITY MODEL

Therefore, it is an object of the present invention to provide a flat bed scanner that can overcome the drawbacks of the prior art.

Therefore, it is an object of the present invention to provide a planar scanner that can simplify the problems associated with the positioning and arrangement of light sources and at the same time can provide a high quality scanner using photometric stereo techniques.

It is another object of the present invention to provide a compact flat bed scanner.

Another object of the present invention is to provide a flat bed scanner which has strict structural constraints to obtain a good scan, but at the same time has flexibility in such a way that the scanner can adapt to various requirements.

The technical purpose indicated and the aims specified are substantially achieved by a flat-bed scanner comprising the technical features described in one or more of the appended claims. The dependent claims correspond to possible embodiments of the invention.

Drawings

Other features and advantages of the present invention will become more apparent in the following non-limiting description of non-exclusive embodiments of the planar scanner.

The following description is made with reference to the accompanying drawings, which are provided for illustrative purposes only and do not limit the scope of the present invention, and in which:

fig. 1 is a perspective view of a planar scanner according to the present invention;

FIG. 2 is a front view of the planar scanner of FIG. 1;

FIG. 2A is an enlarged view of a detail of FIG. 2;

FIG. 3 is a top view of the planar scanner of FIG. 1;

fig. 4A to 4D show an operation sequence of the flat panel scanner according to the present invention;

FIGS. 5A and 5B show enlarged views of other embodiments of the flat panel scanner;

fig. 6 is a side view of the illumination unit forming part of the present invention.

Detailed Description

Referring to the drawings, reference numeral 100 denotes a planar scanner configured to implement photometric stereo techniques.

The plane scanner 100 includes a scanning surface γ on which an object "O" to be scanned can be positioned.

The expression "planar scanner" is used to denote a scanner in which the acquisition of an image representative of the object "O" is performed by scanning different individual portions of the scanning surface γ and thus different portions of the object "O" placed thereon.

According to the present invention, the plane scanner 100 includes the collecting device 1.

The acquisition device 1 is positioned along the vertical optical axis "Y" and perpendicular to the scanning surface γ.

The acquisition device 1 is configured for acquiring at least one image of an object "O" to be scanned or an image of a portion of the object "O", in particular of a portion placed in a portion of the scanning surface γ located below the acquisition device 1.

Preferably, the acquisition device 1 is configured for acquiring a series of images representative of an object "O" to be scanned, in such a way as to obtain a faithful and complete digital reconstruction of the object "O" according to a procedure that will be described in detail below.

According to a preferred embodiment, the acquisition means 1 comprise an image sensor 1a of the linear type, the image sensor 1a of the linear type being configured to acquire at least one image relating to a portion of the object "O" placed along a scanning line "L" on the scanning surface γ.

In more detail, the image sensor 1a of the linear type performs scanning of the object "O", thereby gradually acquiring images related to portions of the object "O" which are gradually placed along the scanning line "L", as described in detail below.

As shown in fig. 1, the scanning line "L" divides the scanning surface γ into a first half plane γ 1 and a second half plane γ 2.

According to the present invention, the planar scanner 100 further comprises a first pair of

light sources

2a, 2b positioned above the first half-plane γ 1 and extending parallel to the scanning line "L".

According to a preferred embodiment, the light sources of the first pair of

light sources

2a, 2b are positioned substantially one above the other.

The planar scanner 100 further comprises a second pair of

light sources

2c, 2d positioned above the second half-plane γ 2 and extending parallel to the scanning line "L".

The light sources of the second pair of

light sources

2c, 2d are positioned substantially one above the other.

As shown in fig. 1 and 2, the first pair of

light sources

2a, 2b and the second pair of

light sources

2c, 2d are positioned symmetrically with respect to the scanning line "L".

Each light source of the first pair of

light sources

2a, 2b and the second pair of

light sources

2c, 2d can be selectively activated for emitting a light beam "F" on the scanning surface γ.

In more detail, the scanner 100 comprises a control unit (not shown) configured for selectively activating the light sources of the first pair of

light sources

2a, 2b and the second pair of

light sources

2c, 2d in such a way that: the

light sources

2a, 2b, 2c, 2d emit respective light beams "F" on the scanning surface γ.

The control unit is also configured for selectively activating the light sources also if other light sources are present, such as in the case shown in the figures.

The activation of a particular

light source

2a, 2b, 2c, 2d and the corresponding deactivation of other light sources may occur in two ways.

In a first way, the activation of the

light sources

2a, 2b, 2c, 2d occurs in a synchronized manner with the acquisition of the image sensor 1a, that is to say the direction of illumination varies in synchronization with the acquisition by the image sensor 1a of the portion of the object "O" lying along the scanning line "L". In this case, the illumination direction is changed for each subsequent acquisition of scan line "L" such that at the end of the acquisition, all illumination directions are acquired, as described in detail below.

On the other hand, in the second way, the activation of one of the

light sources

2a, 2b, 2c, 2d occurs in an asynchronous manner. In this case, the acquisition is repeated a plurality of times, changing the irradiation direction between one acquisition and the next.

In more detail, in one case, each successive portion of the object "O" placed on the scan line "L" is acquired by activating a different

light source

2a, 2b, 2c, 2d (that is, successively cycling all light sources). In this way, in a single acquisition, all the irradiation directions are obtained in a manner mixed in a single image of the mentioned portion placed on the scanning line "L". In another case, a specific

light source

2a, 2b, 2c, 2d is activated and all parts of the object "O" (that is, the parts placed step by step on the scanning line "L") are acquired using the same

light source

2a, 2b, 2c, 2 d. In this case, the

light sources

2a, 2b, 2c, 2d irradiate the object "O", and the whole of the object "O" is acquired by continuously scanning the portion placed on the scanning line "L". After the acquisition has been completed, a first image is obtained. Then, the

light sources

2a, 2b, 2c, 2d are switched off and the other

light source

2a, 2b, 2c, 2d is switched on. In this case, the process for acquiring the entire object "O" is repeated, in such a way as to obtain the second image. The on/off and collection operations are repeated for each different desired direction of light.

As shown in fig. 2A, for each light source of the first and second pairs of

light sources

2A, 2b, 2c, 2d, the planar scanner 100 further comprises an illumination unit 3, the illumination unit 3 comprising a plurality of LED lamps 5 (not visible in fig. 2A) and a plurality of asymmetric lenses 3a each associated with a respective LED lamp 5.

The illumination unit 3 is configured to redirect the light beam "F" emitted by the

light sources

2a, 2b, 2c, 2d on the scanning surface γ at a predetermined redirection angle.

In other words, the light beam "F" emitted by the

light sources

2a, 2b, 2c, 2d, by the plurality of LEDs 5, is redirected at a predetermined redirection angle through the asymmetric lens 3a, in such a way as to illuminate the scanning surface γ with the light beam "F" having a predetermined direction.

As shown in fig. 6, each asymmetric lens 3a is positioned above the respective LED lamp 5 in such a way that the light emitted by the LED lamp 5 passes through the asymmetric lens 3a and is redirected, in such a way as to obtain a light beam "F" that is angled and well directed.

According to a possible embodiment, each illumination unit 3 is configured to redirect the corresponding light beam "F" by a redirection angle that is different from the redirection angles of the other illumination units 3 of the scanner 100, and in any case in such a way as to illuminate the scanning surface γ from directions that are very different from each other.

According to a preferred embodiment, the lighting units 3 associated with the first pair of

light sources

2a, 2b are configured for redirecting the respective light beams "F" by a redirection angle equal to +45 ° and-45 °. The lighting units 3 associated with the second pair of

light sources

2c, 2d are configured for redirecting the respective light beams "F" by redirection angles of +45 ° and-45 °. In this case, since the first pair of

light sources

2a, 2b and the second pair of

light sources

2c, 2d are symmetrical with respect to the scanning line "L", the fact that the scanning surface γ is irradiated from a very different direction is guaranteed, as shown in fig. 3.

In this case, the scanning surface γ is irradiated with light beams "F" having four directions each different from each other, emitted by the

respective light sources

2a, 2b, 2c, 2d (fig. 3).

In other words, for the purpose of optimally implementing the photometric stereo technique, the different illumination directions are mainly determined by the redirection angles applied to the light beam "F" emitted by the

light sources

2a, 2b, 2c, 2d by the lighting unit 3 (in particular the asymmetric lens 3a) applied to each of the

light sources

2a, 2b, 2c, 2d (in particular the LED lamp 5).

According to a preferred embodiment of the invention, the lighting units 3 associated with the light sources of the first pair of

light sources

2a, 2b are configured for redirecting the corresponding light beams "F" by redirection angles opposite to each other.

In other words, the lighting unit 3 associated with the first light source 2a of the first pair of

light sources

2a, 2b redirects the light beam "F" by a redirection angle which is opposite to the redirection angle by which the lighting unit 3 associated with the second light source 2b of the first pair of

light sources

2a, 2b redirects the respective light beam "F".

In this case, for example, if the lighting unit 3 associated with the first light source 2a of the first pair of

light sources

2a, 2b redirects the light beam "F" by an angle of +45 °, the lighting unit 3 associated with the second light source 2b of the first pair of

light sources

2a, 2b redirects the light beam "F" by an angle of-45 °.

According to a preferred embodiment of the invention, the lighting units 3 associated with the light sources of the second pair of

light sources

2c, 2d are configured for redirecting the corresponding light beams "F" at redirection angles opposite to each other.

As shown in fig. 2A, for example, if the lighting unit 3 associated with the first light source 2c of the second pair of

light sources

2c, 2d redirects the light beam "F" by an angle of +45 °, the lighting unit 3 associated with the second light source 2d of the second pair of

light sources

2c, 2d redirects the light beam "F" by an angle of-45 °.

In other words, as shown in fig. 3, the first pair of

light sources

2a, 2b illuminates the scanning surface γ with light beams "F" having redirection angles (and thus opposite illumination directions) opposite to each other, and the second pair of

light sources

2c, 2d illuminates the scanning surface γ with light beams "F" having redirection angles (and thus opposite illumination directions) opposite to each other.

In this case, the scanning surface γ is irradiated from four directions different from each other, ensuring optimal execution of the photometric stereo technique.

Advantageously, the fact that, for each

light source

2a, 2b, 2c, 2d, the respective lighting unit 3 is introduced in such a way that the respective light beam "F" emitted has a different direction makes it possible to illuminate the scanning surface γ from at least four different directions, obtaining the best scanning results.

According to an aspect of the invention, the predetermined redirection angle is between 30 ° and 60 °.

Preferably, the predetermined redirection angle is equal to 45 °.

According to an aspect of the present invention, the LED lamps of the plurality of LED lamps of each

light source

2A, 2b, 2c, 2d are arranged along the arrangement direction "a" parallel to the scanning line "L" (fig. 2A).

According to another possible embodiment, the LED lamps of the plurality of LED lamps 5 of each

light source

2a, 2B, 2c, 2d are offset with respect to the arrangement direction "a" parallel to the scanning line "L" (fig. 5A and 5B). According to this embodiment, the LED lamps and the corresponding asymmetric lenses 3a associated with a pair of

light sources

2a, 2b, 2c, 2d are positioned in an offset (or checkerboard) manner with respect to the LED lamps and the corresponding asymmetric lenses 3a of the other

light sources

2a, 2b, 2c, 2d of the pair.

According to an aspect of the invention, for example as shown in fig. 2A and 6, for each LED lamp 5 of one of the light sources of the second pair of

light sources

2c, 2d, the corresponding lighting unit 3 comprises an asymmetric lens 3 a. Likewise, for each LED lamp 5 of the other one of the light sources of the

second pair

2c, 2d, the corresponding lighting unit 3 comprises an asymmetric lens 3 a.

Preferably, the asymmetric lenses 3a associated with the LED lamps of the same

light source

2A, 2b, 2c, 2d are configured for redirecting the respective light beam "F" according to the same predetermined redirection angle (fig. 2A).

According to an aspect of the invention, lighting unit 3 can be applied to corresponding

light source

2a, 2b, 2c, 2d according to first installation orientation, and at first installation orientation, lighting unit 3 makes light beam "F" emitted by

light source

2a, 2b, 2c, 2d redirect first angle of redirection. Alternatively, the lighting unit 3 may be applied to the respective

light source

2a, 2b, 2c, 2d according to a second mounting orientation in which the lighting unit 3 redirects the light beam "F" emitted by said

light source

2a, 2b, 2c, 2d by a second redirection angle. The second redirection angle is opposite the first redirection angle.

This aspect is particularly advantageous for obtaining different directivities of the light beam "F" of each of the light sources of the first pair of

light sources

2a, 2b and/or of the second pair of

light sources

2c, 2d in a convenient and fast manner. In this case, in fact, the directionality of the light beam "F" emitted by the lighting unit 3 can be changed simply by changing the assembly orientation of the latter on the

light sources

2a, 2b, 2c, 2 d.

The possibility of mounting the lighting unit 3 according to two different mounting orientations is clearly shown in fig. 2A. In this case, one lighting unit 3 has a first mounting orientation, while the other lighting unit 3 has a second mounting orientation.

According to an aspect of the invention, as shown in the figures, the plurality of asymmetric lenses 3a of the same lighting unit 3 have the same orientation. This aspect can also be clearly seen from fig. 2A, where all asymmetric lenses 3a of the lighting unit 3 are oriented in the same direction.

According to the embodiment shown in the figures, the planar scanner 100 may comprise, in addition to the first pair of

light sources

2a, 2b, one or more further light sources provided with respective illumination units 3.

Preferably, the further light source extends parallel to the scanning line "L".

According to an embodiment, the planar scanner 100 may comprise, in addition to the second pair of

light sources

2c, 2d, one or more further light sources provided with respective illumination units 3.

Preferably, the further light source extends parallel to the scanning line "L".

According to an aspect of the invention, the planar scanner 100 further comprises at least one auxiliary light source 4, the at least one auxiliary light source 4 being configured for illuminating the scanning surface γ.

Preferably, the auxiliary light source 4 extends parallel to the scanning line "L".

Even more preferably, the auxiliary light source 4 is not provided with a lighting unit 3.

According to a preferred embodiment, the planar scanner 100 has a first auxiliary light source 4 positioned close to the first pair of

light sources

2a, 2b and a second auxiliary light source 4 positioned close to the second pair of

light sources

2c, 2 d.

In use, in order to obtain a reconstruction of the object "O" using the planar scanner 100, according to the present invention, the first pair of

light sources

2a, 2b and the second pair of

light sources

2c, 2d are positioned parallel to the scanning line "L" in symmetrical positions with respect to the scanning line "L" (fig. 4A).

In this case, the first pair of

light sources

2a, 2b is located in a position above the first half-plane γ 1, while the second pair of

light sources

2c, 2d is located in a position above the second half-plane γ 2.

Each of the

light sources

2a, 2b, 2c, 2d is operatively associated with a respective lighting unit 3 in such a way that the emitted light beam "F" is redirected.

In more detail, the predetermined redirection angle of the asymmetric lens 3a of the lighting unit 3 associated with one of the light sources of the first pair of

light sources

2a, 2b is opposite to the predetermined redirection angle of the asymmetric lens 3a of the lighting unit 3 associated with the other of the light sources of the first pair of

light sources

2a, 2 b.

Similarly, the predetermined redirection angle of the asymmetric lens 3a of the lighting unit 3 associated with one of the light sources of the second pair of

light sources

2c, 2d is opposite to the predetermined redirection angle of the asymmetric lens 3a of the lighting unit 3 associated with the other of the light sources of the second pair of

light sources

2c, 2 d.

After positioning the

light sources

2a, 2b, 2c, 2d and the illumination unit 3, the object "O" to be scanned is positioned on the scanning surface γ under the acquisition device 1.

Subsequently, the first light source in those first and second pairs of

light sources

2a, 2b, 2c, 2d is activated to illuminate the object "O" in such a way. In this case, the light beam "F" emitted by the light source is redirected by the corresponding illumination unit 3, thereby illuminating the scanning surface γ (fig. 4A). In this way, the portion of the object "O" placed along the scanning line "L" is irradiated in a predetermined direction. In this case, the light beam "F" redirected by the illumination unit 3 and incident on the object "O" is reflected towards the acquisition device 1, where the image sensor 1a performs the actual acquisition of the image.

The acquired image substantially corresponds to an image representing a portion (substantially having a bar shape) of the object "O" placed on the scanning line "L".

Subsequently, the first light sources are switched off in favor of activating the second light source of those first pair of light sources 2a, 2B and second pair of

light sources

2c, 2d (fig. 4B).

According to an embodiment (illustrated in fig. 4A to 4D), the light sources of one of the first pair of

light sources

2a, 2b and the second pair of light sources 2c, 2D are selectively switched on first, and subsequently the light sources of the other of the first pair of

light sources

2a, 2b and the second pair of light sources 2c, 2D are selectively switched on.

Alternatively, the

light sources

2a, 2b, 2c, 2d are selectively switched on in such a way that when a light source in the first pair of

light sources

2a, 2b is switched on, a light source in the second pair of

light sources

2c, 2d is switched on, etc.

When the second

light source

2a, 2b, 2c, 2d is turned on, it illuminates the object "O" from another direction because it is provided with the lighting unit 3 configured to redirect the emitted light beam "F" at a predetermined redirection angle (which is different from the predetermined redirection angle of the lighting unit 3 of the first

light source

2a, 2b, 2c, 2 d). In this case, the light beam "F" emitted by the other

light source

2a, 2b, 2c, 2d is irradiated onto the scanning surface γ, thereby being irradiated to the portion of the object "O" placed on the scanning line "L". Subsequently, the light beam "F" is reflected towards the acquisition means 1 in such a way that the image sensor 1a acquires the corresponding image.

The process for switching on the

light sources

2a, 2b, 2c, 2D and for acquiring images is repeated until all light sources of the first pair of

light sources

2a, 2b and the second pair of light sources 2c, 2D have been activated (fig. 4A to 4D).

When all the

light sources

2a, 2b, 2c, 2d have been turned on, and when the linear image sensor 1a has acquired an image representing a portion of the object "O" placed on the scanning line "L" at each turn on, the acquisition device 1 moves in such a way as to allow another portion of the object "O" placed on the scanning line "L" to be illuminated and acquired.

According to a possible embodiment, the planar scanner 100 comprises a movement system (not shown) configured for moving the acquisition device 1 while the scanning surface γ is stationary. In this case, the acquisition device 1 moves according to the individual positions, in such a way as to acquire an image of the object "O" for each individual position.

In this case, an image representing a portion of the object "O" placed on the scanning line "L" is acquired each time the

light sources

2a, 2b, 2c, 2d are turned on. When all the

light sources

2a, 2b, 2c, 2d of the planar scanner 100 have been turned on, the acquisition apparatus 1 is moved so that a new portion of the object "O" (adjacent to the portion just acquired) is placed on the scan line "L". In this case, the

light sources

2a, 2b, 2c, 2d of the planar scanner 100 are again switched on in an alternating manner in such a way that, at each switching on, an image of the portion of the object "O" lying along the scanning line "L" can be acquired.

In another possible embodiment, the scanner 100 comprises a movement system (not shown) configured for moving the scanning surface γ with respect to the acquisition device 1.

Preferably, the movement system moves the scanning surface γ in a horizontal cartesian direction (indicated by the arrow in fig. 1).

Even more preferably, the movement system moves the object "O" at a plurality of individual positions, so that the acquisition means 1, in particular the image sensor 1a, acquires an image for each individual position.

Alternatively, the movement system can move the scanning surface γ and the acquisition device 1 simultaneously.

In other words, for each activation of a light source in the first and second pairs of

light sources

2a, 2b, 2c, 2d, when an image is acquired relating to a portion of the object "O" placed on the scan line "L", the movement system enables a new portion of the object "O" to be scanned while placed on the scan line "L". In this case, the

light sources

2a, 2b, 2c, 2d are again selectively activated, so that also in this case an image relating to another part of the object "O" is acquired during each activation of a light source.

The operations for actuating the movement system, for activating the

light sources

2a, 2b, 2c, 2d and for acquiring the images are repeated continuously until all parts of the object "O" have been scanned.

According to a preferred embodiment, the acquired images are sent to a control unit configured to acquire and process data related to the continuous scanning of the object "O".

Using this data, the control unit is able to digitally reconstruct the scanned object "O" in a highly faithful manner.

The present invention provides an overall solution to the problem of how to position and arrange light sources in a scanner 100 designed to implement photometric stereo techniques in an optimal manner. In particular, the present invention introduces a concept that makes it possible to construct a scanner 100 with a large number of light sources in such a way as to guarantee a good differentiation of the irradiation directionality of the object to be scanned.

Claims

1. A planar scanner (100) configured to implement photometric stereo techniques, the planar scanner (100) comprising:

scanning a surface

An object (O) to be scanned can be positioned on the scanning surface

The above step (1);

an acquisition device (1) positioned along a vertical optical axis (Y) and perpendicular to the scanning surface

The acquisition device (1) comprises a sensor (1a) for images of a linear type, the sensor (1a) being configured to acquire an image of the object (O) along the scanning surface

At least one image relating to a portion on which a scanning line (L) is placed, said scanning line (L) being intended to scan said surface

Is divided into a first half plane

And a second half plane

A first pair of light sources (2a, 2b) positioned in said first half-plane

Extends above and parallel to the scanning line (L);

a second pair of light sources (2c, 2d) positioned in said second half-plane

Extending above and parallel to the scanning line (L), the first pair of light sources (2a, 2b) and the second pair of light sources (2c, 2d) being positioned symmetrically with respect to the scanning line (L);

characterized in that, for each light source of said first pair of light sources (2a, 2b) and said second pair of light sources (2c, 2d), said planar scanner (100) comprises an illumination unit (3), said illumination unit (3) comprising a plurality of LED lamps (5) and a plurality of asymmetric lenses (3a), said plurality of asymmetric lenses (3a) being each associated with a respective LED lamp (5) of said plurality of LED lamps (5), said illumination unit (3) being configured for causing emission by said light source (2a, 2b, 2c, 2d) at said scanning surface

Figure DEST_PATH_FDA00037868364600000110

The light beam (F) is redirected at a predetermined redirection angle.

2. The planar scanner (100) according to claim 1, characterized in that a plurality of the illumination units (3) associated with a plurality of the light sources of the first pair of light sources (2a, 2b) are configured to redirect the corresponding light beams (F) with mutually opposite redirection angles.

3. The planar scanner (100) according to claim 1, wherein a plurality of the illumination units (3) associated with a plurality of light sources of the second pair of light sources (2c, 2d) are configured to redirect the corresponding light beams (F) with mutually opposite redirection angles.

4. The planar scanner (100) according to claim 1, characterized in that each illumination unit (3) of the planar scanner (100) is configured to redirect the corresponding light beam (F) with a redirection angle different from the redirection angles of the other illumination units of the scanner (100).

5. The planar scanner (100) according to claim 1, characterized in that the redirection angle is between 30 ° and 60 °.

6. The planar scanner (100) according to claim 5, characterized in that the redirection angle is equal to 45 °.

7. The planar scanner (100) according to claim 1, wherein the LED lamps (5) of the plurality of LED lamps are arranged in an arrangement direction parallel to the scanning line (L).

8. The planar scanner (100) according to claim 1, wherein the LED lamps (5) of the plurality of LED lamps are offset with respect to an alignment direction parallel to the scanning line (L).

9. The planar scanner (100) according to claim 1, characterized in that the planar scanner (100) comprises a movement system configured to cause the scanning surface to scan

Is moved relative to the acquisition device (1).

10. The planar scanner (100) according to claim 9, wherein the moving system is configured to move the object (O) to a plurality of individual positions, and wherein the acquisition arrangement (1) acquires an image for each individual position.

11. The planar scanner (100) according to claim 1, characterized in that the planar scanner (100) comprises a movement system configured to move the acquisition device (1) with respect to the scanning surface

And (4) moving.

12. The planar scanner (100) according to claim 1, wherein the planar scanner (100) comprises a control unit configured to:

such that light sources (2a, 2b, 2c, 2d) of said first and second pairs emit collimated light on said scanning surface

Selectively activating said light sources (2a, 2b, 2c, 2d) in the manner of respective light beams (F);

data relating to successive scans of the object (O) are acquired and processed.

13. The planar scanner (100) according to claim 1, characterized in that the planar scanner (100) comprises at least one auxiliary light source (4), the at least one auxiliary light source (4) being configured to illuminate the scanning surface