CN217486531U - Flat scanner for implementing photometric stereo techniques - Google Patents

Abstract

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

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

A portion of the scan line (L) placed on the at least one image is related. The flatbed scanner (100) also includes a first pair of light sources extending parallel to the scan line (L) and a second pair of light sources extending parallel to the scan line (L). For each light source of the first pair of light sources and the second pair of light sources, the flatbed scanner (100) comprises an illumination unit (3) comprising a plurality of LED lamps (5) and respective LED lamps (5) Associated multiple asymmetric lenses (3a). The illumination unit (3) is configured for redirecting the light beam emitted by the light source on the scanning surface at a predetermined redirection angle.

Description

Flat scanner for implementing photometric stereo techniques

technical field

The utility model relates to a plane scanner configured to implement photometric stereo technology. In particular, the flat scanner according to the present invention is widely used in the field of image acquisition.

Background technique

As is well known, photometric stereo technology allows obtaining 3D information starting from a set of color or grayscale images. Since this technique is particularly suitable for capturing fine details of primarily two-dimensional surfaces (such as, for example, paintings, bas-reliefs, marble slabs, etc.), and on the other hand, cannot capture the shape of complex three-dimensional objects (such as, for example, bowls), the The technology is designed to be implemented in scanners for flat images in order to scan materials and surfaces while returning color and 3D digital information.

As is well known, 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 with each activation.

In order to implement the photometric stereo technique, a planar scanner is usually used, which comprises a scanning surface and a plurality of light sources on which the object is located, in such a way that the object is illuminated from different directions.

Prior art scanners include: an image sensor configured to capture an image about the object; and an optical system interposed between the image sensor and the scanning surface and aligned with the image along a vertical axis perpendicular to the scanning surface sensor alignment.

In the above scanner, one light source is turned on at a time, and each time it is turned on, the image sensor captures an image of the object and/or an image of a portion of the object.

Although, unlike other 3D image acquisition techniques, photometric stereo does not require the use of dedicated 3D devices (such as, for example, confocal lasers, etc.) and allows information to be obtained in color and a high level of detail, for best results, the light sources need to be arranged Inside the scanner, at least four illumination directions that are sufficiently different from each other are obtained 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 scanner of the prior art is provided in the patent document EP 3210370, which shows a planar scanner comprising an optical system, a linear image sensor (that is to say, capable of capturing an edge along an object). A sensor that scans a portion of the associated image placed by a scan line defined by the surface) and a first light source and a second light source located on either side of the scan line 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 turned off, while the second light source is turned on and the acquisition operation is repeated.

Since it is known that the greater the number of different directions in which the object is illuminated, the better the result, so in prior art scanners with only two light sources, the object is repositioned on the scanning surface in such a way that relative to Rotate 90° from the previous orientation. 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 objects can be captured when illuminated from four different directions without increasing the number of light sources (and thus the overall size of the scanner).

On the downside, this scanner has several drawbacks. 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 scanned surface, thus requiring additional acquisition and subsequent operations to stitch the images.

Another disadvantage also comes from the fact that the object has to 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 light deflectors can be removably applied, in such a way that the direction of light emission is changed by a predetermined angle Towards.

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

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

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

Disadvantageously, this scanner also has the disadvantage of requiring manual intervention to obtain different illumination directions. In this case, the scanner is particularly clumsy 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.

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

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

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

Disadvantageously, in this case, even if the scanning surface is illuminated from four different directions, the second pair of light sources cannot be used for rays with a uniform angle of incidence on the scan line and thus on the part of the object placed there The beam illuminates the scan line. The angle of incidence of the light ray hitting the end of the scan line closest to the turned-on light source is greater than the incident angle of the light ray hitting the end of the scan line opposite the light source.

This results in a 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 disadvantage, planar scanners are known in which a second pair of light sources is located at the ends 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 ends of the scan line. The first pair of light sources and the second pair of light sources are arranged substantially above the scanning surface in a cross-like arrangement. This type of scanner uses an unconventional telecentric optical system and an x and y type of acquisition map. In this case, large objects are scanned by acquiring adjacent sections (strips), which must then 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 traditional optics and large scan lines.

Utility model content

Therefore, the technical purpose of the present invention is to provide a plane scanner that can overcome the defects of the prior art.

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

Another object of the present invention is to provide a compact plane scanner.

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

The technical objects indicated and specified objects are substantially achieved by a flat surface scanner comprising the technical features recited in one or more of the appended claims. The dependent claims correspond to possible embodiments of the invention.

Description of drawings

Other features and advantages of the present invention will become apparent from the following non-limiting description of non-exclusive embodiments of flat surface scanners.

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

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

Fig. 2 is the front view of the plane scanner of Fig. 1;

Figure 2A is an enlarged view of the detail of Figure 2;

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

4A to 4D illustrate the operation sequence of the planar scanner according to the present invention;

Figures 5A and 5B show enlarged views of other embodiments of a planar scanner;

6 is a side view of the lighting unit forming portion of the present invention.

Detailed ways

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

The planar 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 representing an object "O" is by scanning different individual parts of the scanning surface γ and thus scanning the placement of the object "O" thereon different parts of the implementation.

According to the present invention, the plane scanner 100 includes the acquisition 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 the object "O" to be scanned or an image of a part of the object "O", in particular of the part placed in the part of the scanning surface γ that lies below the acquisition device 1 .

Preferably, the acquisition device 1 is configured for acquiring a series of images representing the object "O" to be scanned, in such a way that a faithful and complete digital reconstruction of the object "O" is obtained according to a process to be described in detail below.

According to a preferred embodiment, the acquisition device 1 comprises an image sensor 1a of a linear type configured to acquire at least a portion of the object "O" placed along a scan line "L" on the scan surface γ an image.

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

As shown in FIG. 1, scan line "L" divides the scan surface γ into a first half-plane γ1 and a second half-plane γ2.

According to the present invention, the planar scanner 100 also includes a first pair of light sources 2a, 2b positioned above the first half-plane γ1 and extending parallel to the scan 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 flatbed scanner 100 also includes a second pair of light sources 2c, 2d positioned above the second half-plane γ2 and extending parallel to the scan line "L".

The light sources of the second pair of light sources 2c, 2d are substantially positioned one above the other.

As shown in Figures 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 scan line "L".

Each 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 includes a control unit (not shown) configured to selectively activate 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: The light sources 2a, 2b, 2c, 2d emit corresponding light beams "F" on the scanning surface γ.

If other light sources are present, such as in the case shown in the figures, the control unit is also configured to also selectively activate these light sources.

Activation of specific light sources 2a, 2b, 2c, 2d and corresponding deactivation of other light sources can occur in two ways.

In the first way, the activation of the light sources 2a, 2b, 2c, 2d occurs in synchronization with the acquisition of the image sensor 1a, that is, the illumination direction is the same as that of the image sensor 1a for the object "O" along the scan line" The acquisition of the section where the L" is placed changes synchronously. In this case, the illumination direction is changed for each subsequent acquisition of scan line "L" so 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 multiple times, changing the direction of illumination between one acquisition and the next.

In more detail, in one case, by activating a different light source 2a, 2b, 2c, 2d (that is, continuously cycling all light sources) for each of the objects "O" placed on the scan line "L" Consecutive sections were collected. In this way, in a single acquisition, all illumination directions are obtained in a manner that is blended into a single image of the mentioned portion placed on scan line "L". In another case, a specific light source 2a, 2b, 2c, 2d is activated and the same light source 2a, 2b, 2c, 2d is used for all parts of the object "O" (that is, gradually placed on the scan line part above "L") for acquisition. In this case, the light sources 2a, 2b, 2c, 2d illuminate the object "O", and the whole of the object "O" is acquired by successively scanning the parts placed on the scan 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 sources 2a, 2b, 2c, 2d are switched on. In this case, the process for acquiring the entire object "O" is repeated in such a way that the second image is obtained. Repeat on/off and acquisition operations for each desired light in a different direction.

As shown in FIG. 2A, for each of the first pair of light sources 2a, 2b and the second pair of light sources 2c, 2d, the flat scanner 100 further includes an illumination unit 3 including a plurality of LED lamps 5 ( not visible in FIG. 2A ) and a plurality of asymmetric lenses 3 a each associated with a respective LED lamp 5 .

The lighting unit 3 is configured to redirect the light beam "F" emitted by the light sources 2a, 2b, 2c, 2d on the scanning surface γ by a predetermined redirection angle.

In other words, through the asymmetric lens 3a, the light beams "F" emitted by the light sources 2a, 2b, 2c, 2d, by the plurality of LEDs 5 are redirected at a predetermined redirection angle, in such a way to utilize the light beams having the predetermined direction "F" illuminates the scanning surface γ.

As shown in Fig. 6, each asymmetric lens 3a is positioned above the corresponding 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, obtained in such a way Angled and well directed beam "F".

According to a possible embodiment, each lighting unit 3 is configured to redirect the corresponding light beam "F" by a redirection angle, which is different from the redirection angle of the other lighting units 3 of the scanner 100, and in any In this way the scanning surface γ is irradiated from very different directions from each other.

According to a preferred embodiment, the lighting unit 3 associated with the first pair of light sources 2a, 2b is configured for redirecting the respective light beams "F" by redirection angles equal to +45° and -45°. The lighting unit 3 associated with the second pair of light sources 2c, 2d is configured for redirecting the respective light beams "F" by redirection angles of +45° and -45°. In this case, the fact that the scanning surface γ is illuminated from very different directions is guaranteed due to the symmetry of the first pair of light sources 2a, 2b and the second pair of light sources 2c, 2d with respect to the scanning line "L", as in Fig. 3 shown.

In this case, the scanning surface γ is irradiated by light beams "F" having four directions which are all 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 illumination unit 3 (especially the asymmetric lens 3a) applied to each of the light sources 2a, 2b, 2c, 2d (especially the LED lamps 5). ) applied to the redirection angle of the light beam "F" emitted by the light sources 2a, 2b, 2c, 2d is determined.

According to a preferred embodiment of the present 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" at mutually opposite redirection angles.

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 that is the same as the second light source of the first pair of light sources 2a, 2b 2b The associated lighting unit 3 reverses the redirection angle of the corresponding 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" to an angle of +45°, then 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" to an angle of +45°. The associated lighting unit 3 of the second light source 2b redirects the light beam "F" to an angle of -45°.

According to a preferred embodiment of the present 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 mutually opposite redirection angles.

As shown in Figure 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" to an angle of +45°, the The lighting unit 3 associated with the second light source 2d of 2d redirects the light beam "F" to an angle of -45°.

In other words, as shown in Fig. 3, the first pair of light sources 2a, 2b illuminate the scanning surface γ with beams "F" having mutually opposite redirection angles (and thus opposite illumination directions), the second pair of light sources 2c, 2d Scanning surface γ is irradiated with beams "F" having mutually opposite redirection angles (and thus opposite illumination directions).

In this case, the scanning surface γ is illuminated from four directions that are different from each other, guaranteeing the best execution of the photometric stereo technique.

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

According to an aspect of the present 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 an arrangement direction "A" parallel to the scan 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 scan line "L" (FIG. 5A and Figure 5B). According to this embodiment, the LED lamps and corresponding asymmetric lenses 3a associated with the pair of light sources 2a, 2b, 2c, 2d are relative to the LED lamps and corresponding non-symmetrical lenses 3a of the other pairs of light sources 2a, 2b, 2c, 2d The symmetrical lenses 3a are positioned in an offset (or checkerboard) fashion.

According to an aspect of the present invention, for example as shown in Figures 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 3a . Likewise, for each LED lamp 5 of the other of the light sources of the second pair of light sources 2c, 2d, the corresponding lighting unit 3 comprises an asymmetric lens 3a.

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 beam "F" according to the same predetermined redirection angle (Fig. 2A).

According to an aspect of the present invention, the lighting unit 3 can be applied to the respective light sources 2a, 2b, 2c, 2d according to a first installation orientation in which the lighting unit 3 causes the light sources 2a, 2b, 2c, 2d to emit light The beam "F" is redirected to the first redirection angle. Alternatively, the lighting unit 3 may be applied to the respective light sources 2a, 2b, 2c, 2d according to a second installation orientation in which the lighting unit 3 causes the light beams emitted by said light sources 2a, 2b, 2c, 2d "F" redirects to the second redirection angle. The second redirection angle is opposite to the first redirection angle.

This aspect is particularly advantageous to obtain the different directivity of the light beam "F" of each of the light sources of the first pair of light sources 2a, 2b and/or of the light sources of the second pair of light sources 2c, 2d in a convenient and fast manner. Indeed, in this case, the directivity of the light beam "F" emitted by the lighting unit 3 can be changed simply by changing the orientation of its assembly on the light sources 2a, 2b, 2c, 2d.

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 installation orientation and the other lighting unit 3 has a second installation orientation.

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

According to the embodiment shown in the figures, in addition to the first pair of light sources 2a, 2b, the flatbed scanner 100 may also comprise one or more further light sources provided with corresponding lighting units 3 .

Preferably, the additional light source extends parallel to scan line "L".

According to an embodiment, in addition to the second pair of light sources 2c, 2d, the flatbed scanner 100 may also comprise one or more further light sources provided with corresponding lighting units 3 .

Preferably, the additional light source extends parallel to scan line "L".

According to an aspect of the present invention, the plane scanner 100 further comprises at least one auxiliary light source 4 configured to illuminate the scanning surface γ.

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

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

According to a preferred embodiment, the flatbed scanner 100 has a first auxiliary light source 4 located close to the first pair of light sources 2a, 2b and a second auxiliary light source 4 located close to the second pair of light sources 2c, 2d.

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 scan line "L" relative to the Symmetrical position of scan line "L" (FIG. 4A).

In this case, the first pair of light sources 2a, 2b is located above the first half-plane γ1 and the second pair of light sources 2c, 2d is located above the second half-plane γ2.

Each of the light sources 2a, 2b, 2c, 2d is operatively associated with the 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 and the other of the light sources of the first pair of light sources 2a, 2b The predetermined redirection angle of the asymmetric lens 3a of the associated lighting unit 3 is opposite.

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 and the other of the light sources of the second pair of light sources 2c, 2d The predetermined redirection angles of the asymmetric lenses 3a of the associated lighting units 3 are opposite.

After positioning the light sources 2a, 2b, 2c, 2d and the lighting unit 3, the object "O" to be scanned is positioned on the scanning surface γ below the acquisition device 1 .

Subsequently, the first light source of those first pair of light sources 2a, 2b and the second pair of light sources 2c, 2d is activated in such a way that the object "O" is illuminated. In this case, the light beam "F" emitted by the light source is redirected by the corresponding lighting unit 3 so as to illuminate the scanning surface γ ( FIG. 4A ). In this way, the portion of the object "O" placed along the scan line "L" is illuminated in a predetermined direction. In this case, the light beam "F" redirected by the lighting 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 the image representing the portion (substantially in the shape of a bar) of the object "O" placed on the scan line "L".

Subsequently, the first light source is switched off to facilitate activation of the second light source of those first pair of light sources 2a, 2b and the second pair of light sources 2c, 2d (Fig. 4B).

According to an embodiment (shown in Figures 4A-4D), the light source of one of the first pair of light sources 2a, 2b and the second pair of light sources 2c, 2d is first selectively switched on, and then the first The light source of the other of the light sources 2a, 2b and the second pair of light sources 2c, 2d is selectively turned on.

Alternatively, the light sources 2a, 2b, 2c, 2d are selectively selected in such a way that when the light source of the first pair of light sources 2a, 2b is turned on, the light source of the second pair of light sources 2c, 2d is turned on, etc. ground connection.

When the second light source 2a, 2b, 2c, 2d is switched on, because it is provided with a beam "F" that is configured to emit light at a predetermined redirection angle (which is different from the first light source 2a) , 2b, 2c, 2d of the predetermined redirection angle of the lighting unit 3) redirected lighting unit 3, so it illuminates the object "O" from the other direction. In this case, the beam "F" emitted by the other light sources 2a, 2b, 2c, 2d strikes the scanning surface γ, thereby impinging on the part of the object "O" placed on the scanning line "L". Subsequently, the light beam "F" is reflected towards the acquisition device 1 in such a way that the image sensor 1a acquires a corresponding image.

The process for switching on the light sources 2a, 2b, 2c, 2d and for acquiring images is repeated until all the 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 Fig. 4D) .

When all the light sources 2a, 2b, 2c, 2d have been switched on, and when the linear image sensor 1a has acquired an image representing the part of the object "O" placed on the scan line "L" each time it is switched on , the acquisition device 1 is moved in such a way as to allow illumination and acquisition of another part of the object "O" placed on the scan line "L".

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

In this case, each time the light sources 2a, 2b, 2c, 2d are turned on, an image representing the portion of the object "O" placed on the scan line "L" is acquired. When all the light sources 2a, 2b, 2c, 2d of the planar scanner 100 have been switched on, the acquisition device 1 is moved so that a new part of the object "O" (adjacent to the part just acquired) is placed on the scan line "L" "superior. In this case, the light sources 2a, 2b, 2c, 2d of the flat panel scanner 100 are again switched on in an alternating manner in such a way that at each switching on, an edge scan of the object "O" can be acquired Image of the part where the line "L" is placed.

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

Preferably, the movement system moves the scanning surface γ in a horizontal Cartesian direction (indicated by the arrows in FIG. 1 ).

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

Alternatively, the moving 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 pair of light sources 2a, 2b and the second pair of light sources 2c, 2d, when an image is acquired related to the portion of the object "O" placed on the scan line "L", The movement system allows a new portion of object "O" to be scanned if placed on scan line "L". In this case, the light sources 2a, 2b, 2c, 2d are selectively activated again, so that also in this case, during each activation of the light sources, images relating to another part of the object "O" are acquired.

The operations for actuating the movement system, for activating the light sources 2a, 2b, 2c, 2d and for acquiring 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, which is configured to acquire and process data related to successive scans 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 a general solution to the problem of how to place and arrange light sources in a scanner 100 designed to best implement photometric stereo technology. In particular, the present invention introduces an idea to configure the scanner 100 with a large number of light sources in such a way as to ensure good differentiation of the illumination directionality of the object to be scanned.

Claims (13)

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

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

Images