LIKE MATERIAL

DESCRIPTION Field of the Invention

The present invention relates to the field of production and sale of stone products and more specifically relates to an apparatus for the capture of high resolution images of a slab of stone-like material such as for example slabs of marble, granite and natural stone in general .

Background Art

The slabs obtained from the cutting of blocks of stone-like material are generally leant against each other in a substantially vertical position to form compact groups known as "packs" . Each pack is made up of a certain number of slabs and is stored in a warehouse, ready to be sold.

The slab inspection by potential buyers is not however easy. Their grouping together in packs allows inspection of the first and last slab, leaving all the others inaccessible for observation. Therefore, in order to enable a complete view thereof, the only solution is to break up the pack, moving all the individual slabs, and then group them back together again, once inspection by the buyer has ended.

Given the considerable dimensions (for example 300cm x 200cm) and the high weight (some hundred kilos) that a natural stone slab may have, this operation can only be performed with fork-lift trucks or shunters, making it therefore extremely slow and expensive. Moreover all the necessary movements entail a considerable risk of possible

damage or breakage of the same slabs.

A possible solution of this problem is to create a paper or digital photo collection of the single slabs stored in the warehouse and to this end all the slabs need to be photographed before being grouped into packs . The buyer can therefore inspect the various slabs, even from a remote point, without requiring their complicated and burdensome movements. The evident simplicity and practicality of this solution is offset by the fact that the different boundary conditions relating to each photographic shot (distance from the slab, natural or artificial light, exposure, size of the slab, etc.) do not allow a true and detailed representation of colours and shading, or possible defects, of each slab. All this is further worsened by the grain effect due to the printing in an enlarged format. It should also be noted that the reproduction of the whole slab in a single photograph requires either an appropriate focal distance, which does not however allow detailed reproduction, or the use of a wide angle lens, which however tends to distort the border of the image unacceptably . For these reasons the reproduction of a slab must be divided into several photos, complicating however the inspection thereof.

The uneven quality of the various photographs moreover does not enable comparisons between slabs to be made or, in the case of digital photographs, a software analysis to be carried out to check their differences in quality and in colour components. Summary of the Invention The object of the present invention is to provide an apparatus by which to obtain images of slabs of stone-like material that avoids the need to move them when it is

necessary to assess their characteristics at the time of purchase, without however posing the limitations and disadvantages of the photographic system mentioned above.

Another object of the present invention is to provide an apparatus of the type mentioned above that allows automatic scanning of the slabs in a stone material in a simple and quick way and ensuring high resolution of the images produced thereby.

A further object of the present invention is to provide an apparatus of the type mentioned above that also allows measurement of the thickness of the slab and of other geometric features.

These and other objects are achieved with the apparatus for performing high resolution scanning of a slab of stone material according to the present invention, comprising : slide means for moving the slab and fitted with encoder means to generate a number of pulses in proportion to the forward movement of the slab; - optical scanning means aimed at said slide means for capturing the image of the slab moving forwards thereon;

- means for detecting the presence of the slab at the optical scanning means;

- means for processing signals from the encoder and from the detecting means to perform the acquisition of images formed by successive adjacent portions of the slab via the optical scanning means, and for comparing values provided by the encoder with a preset value indicating the forward movement necessary to present a new portion of the slab to be scanned to the optical scanning means . Brief description of the drawings The features and the advantages of the process and

of the apparatus for high resolution scanning of a slab in stone material according to the present invention will be made clearer by the following description of one of its embodiments, given by way of a non-limiting example with reference to the accompanying drawings, in which:

- Figure 1 shows a schematic overall side view of the apparatus according to the invention with a slab of marble positioned for scanning;

- Figure 2 shows a schematic perspective view of a bridge-like frame of the apparatus according to Figure 1 ;

- Figures 3 and 4 show front views of transmission and reception photoelectric panels, respectively;

Figure 5 is an enlarged schematic view of the apparatus according to the invention, with functional connections to processing and control units;

- Figure 6 shows a top plan view of a portion of the slide means of the apparatus according to Figure 1 ;

- Figure 7 shows a flow diagram of a process for performing a scan of a slab according to the invention; - Figures 8 and 9 are respectively a block diagram and a flow diagram relating to a pulse controller connected to the slide means.

Detailed description of the Invention

Referring to Figures 1 to 5 , the apparatus according to the invention, denoted generally by 1, comprises a frame 2, bridging a slide bench 3 or roller assembly of a conventional type, designed to translate a slab L linearly in a direction of forward movement F. The frame 2 comprises a box structure 4, positioned transversally over the bench 3 and containing the optical and electronic parts for scanning the slab L. The box structure 4, whose length is greater than the usual heights of slabs, is

supported by two uprights 5 of the frame 2, as shown in particular in Figure 2, each one ending on the ground with a base 6.

A transmission photoelectric panel 7a and a reception photoelectric panel 7b, shown in detail in Figures 3 and 4, are placed on the uprights 5 faced one towards the other at the same height. Both panels are equipped with photoelectric cells 8 and their height can be adjusted, starting from a base position flush with the bench 3.

The panels 7a and 7b, whose working height is greater than the possible thicknesses of the slabs that can be produced, are positioned in such a way that the respective photoelectric cells 8 are mutually corresponding. Whereas in the panel 7a the photoelectric cells 8 are arranged in a compact array, in the panel 7b they are arranged on two columns spaced at a certain distance and centred in relation to a slit 9 formed along a face of the box structure 4 turned towards the bench 3. In the box structure 4 a sensor 10 is placed, consisting of a colour CCD linear video camera, arranged horizontally with the optics turned upwards in the present embodiment. The sensor 10 receives the image of the slab in order to scan it through the slit 9 which substantially extends over the whole length of the box structure 4 and is a few centimetres wide (four centimetres in the present embodiment) . This width allows phenomena of interference to be prevented and, at the same time, allows filtering of the quantity of light required by the sensor 10. Between the slit 9 and the sensor 10 a set of mirrors 11 is arranged (five in the example illustrated) , all tilted at 45° , collimated one with the other and housed in the box

structure 4, the first mirror being placed on the vertical line of the sensor 10, while the last mirror is aligned with the slit 9. The lengthening of the optical path obtained with the set of mirrors 11 allows the image to be moved away, reducing its dimension to a level compatible with the sensor, which is a few centimetres wide. In this way the dimension of the mirrors can also be gradually reduced from the mirror closest to the slit 9 to the one closest to the sensor 10. On the face of the box structure 4 turned towards the bench 3 a light source 12, is placed for a proper illumination of the slab L so that the mirrors 11 can reflect its image and the optical sensor 10 perform scanning thereof . The bench 3 extends longitudinally under the frame

2, perpendicularly to the box structure 4 and between the two uprights 5. It has a width larger than the usual width

(or height) of the slabs, and between its longitudinal walls 13 a plurality of motorised shafts 14 extend, supporting rubber (or rubber-coated) rollers 15 that project from the upper edge of the walls 13.

A coloured bar 16 also extends between the walls 13 in a perpendicular way thereto and therefore parallel to the shafts 14, projecting from the walls to a lesser extent in relation to the rollers 15. The bar 16 has a length greater than the usual width of the slabs .

The bench 3 is arranged in relation to the frame 2 in such a way that the bar 16 and the slit 9 of the frame 2 are in a position of perfect coplanarity on a vertical plane, and more particularly are in a central position with respect to the two columns of photoelectric cells 8 of the panel 7b, as shown in Figure 5.

Due to the rotation of the shafts 14, the slab L moves linearly along the bench 3. A conventional digital encoder (not shown) is attached to any one of the drive shafts 14, and is designed to generate a number of pulses corresponding to the extent of rotation of the same shaft. In this way by counting the pulses it is possible to measure the linear displacement of the slab L and learn of its position on the bench 3, as well as the speed and the direction of movement at any time. By translating on rollers 15, the slab arrives under the box structure 4, where it is illuminated by the light source 12 and passes between the two photoelectric panels 7a and 7b. Some of the relative photoelectric cells 8 are covered by the profile of the slab L, and this provides a signal for the start of the passage of the slab at the slit 9 and the bar 16. The two panels 7a and 7b are also able to indicate in this way the thickness of the slab L.

The image that the slit 9 of the box structure 4 enables to be captured comprises a transverse portion, four centimetres wide, of the slab L wherefrom the coloured ends of the bar 16 project laterally. The successive reflections that the image undergoes, denoted by a broken line and the numeral 17, are necessary for concentrating the image on the optical sensor 10. At the end of the reflections the image reaches the sensor 10 considerably reduced in size thanks to the lengthening of the optical path produced with the same reflections. The sensor 10 scans the image by capturing a very thin portion only of the whole, reflected and reduced image, whose width is a function of the CCD used and of the distance between the CCD sensor and the slab, for example of the order of 0.2 mm. The series of images of the portions

acquired by the sensor 10 are then composed, as will be explained herein below, so as to obtain a unique image of the entire slab L, which will appear as if it were placed over a supporting plane having the same colour as the bar 16.

As shown in figure 5, the encoder connected to one of the drive shafts 14 is interfaced with a pulse controller (CI) denoted by 18. The pulse controller 18, the photoelectric panels 7a and 7b, the light source 12 and the optical sensor 10 are in turn connected with a high speed digital interface to a central processing unit

(CPU) denoted by 19. On the basis of the data continually acquired, the CPU 19 controls the components of the apparatus 1 with which it interfaces so as to carry out scanning of the slab L, as will be explained herein below. Figure 7 shows in particular the flow diagram of a process followed by the CPU 19 to carry out the scan of a slab L.

As soon as the slab L intercepts the first column of photoelectric cells 8 of the panel 7b, the latter measures its thickness (denoted by BFH) and simultaneously sends to the CPU a signal of the presence of the slab L between the photoelectric cells 8 of the same panels (first essential condition for scanning and denoted in the diagram by BFH>0) . The CPU acquires the information and immediately generates a RESET command sent to the CI 18, which in turn retransmits it to the encoder of the drive shaft 14. With the reset command the number of pulses counted by the encoder and the maximum value measured by the same encoder and stored by the CI 18 (value denoted by RMV in Figures 8 and 9) are deleted. The maximum value register (RMV) represents the value of the most advanced position reached

by the slab and indicated by the encoder during a scanning step. Sending of the reset signal indicates the starting moment of the actual scanning operations (denoted by IS) by the apparatus 1. From this moment, while the CI 18 continues to signal, as explained in greater detail below, a forward movement useful for scanning of the slab L (second essential condition and denoted in the diagram with "CI on?"), the optical sensor 10 continues to perform (command denoted by GRAB) scans of successive portions of the same slab. When the whole slab L has passed under the slit 9, the CI 18 continues to send to the CPU 19 signals of forward movement useful for scanning, while the slab is still between the panels 7a and 7b that continue to signal the presence thereof (BFH>0) . Only when the slab has passed fully beyond the area between the two panels 7a and 7b does the CPU 19 interrupt sending of the signals of new scans of portions of slab to the sensor 10 and the scan ends (FS) . Referring now also to Figures 8 and 9, as already mentioned, when the panels 7a and 7b signal the presence of the slab L in the working area between the photoelectric cells 8, the CPU 19 sends a reset signal that clears the RMV value stored in the CI 18, and which also clears the count of the pulses performed by the encoder.

The encoder is equipped with a 48 bit digital indicator, denoted by the term POS and used to represent the position of the same encoder in relation to the zero position assumed at reset. As soon as the encoder detects a new advance in the count of the pulses, the corresponding position is stored in place of the old RMV

value that has been cleared. A microprocessor 20, contained in the CI 18 and operating according to the flow diagram shown in Figure 9, compares the continually detected value of the POS with the RMV value stored according to the disequation POS>RMV and, when the first exceeds the second, the microprocessor 20 stores its relative value in place of the RMV value. In this way the most advanced position achieved by the slab is held in the memory. It may effectively be the case that the slab is subjected to movements in a direction opposite to the natural one of forward movement. In this case the count of the number of pulses measured by the encoder comes back, yet the RMV value remains the one relating to the last forward movement by the slab L. Having performed this operation, the microprocessor 20 compares the rest of the division between the value of the POS stored in place of the old RMV value and a IPS value set by the manufacturer

(described in greater detail hereinbelow) with the value 0

(denoted in the diagram by POS%IPS=0) . When this condition is met, the microprocessor 20 sends a pulse (SC) to the CPU 19, corresponding to the scanning start signal of a portion. At this point the microprocessor 20 starts a new cycle of the flow diagram of Figure 9.

The CPU 19, having received the pulse SC from the controller 18, stores the first scan of the image of the portion of slab L present under the slit 9 with the optical sensor 10.

The sending of successive pulses SC to continue scanning automatically is commanded by the forward movement of the slab L. The microprocessor 20 in fact stores a IPS (pulses per beat) value which indicates the number of pulses corresponding to the forward movement of

the slab L on the bench 3 for a distance equal to the width of a pixel captured by the sensor 10 of the linear

CCD video camera. This is the forward movement necessary for bringing a new portion of slab L that has yet to be scanned in correspondence of the bar 16 and the slit 9.

Then, as soon as the slab moves forward by a distance

(beat) which, converted into pulses, equals the IPS value, the microprocessor 20 sends a new SC signal to the CPU 19, corresponding to the command to the sensor 10 for the scanning of the new portion of slab L. In this way, with the gradual forward movement of the slab L, the sensor 10 automatically performs scanning of the successive portions of slab L which succeed under the slit 9.

The CPU 19 performs the additional function of orderly recomposing in a single image, in a manner per se known, of the sequence of the various images of scanned slab portions. The image obtained in this way can be sent to a computer (not shown) wherein it can be stored in a special file equivalent to the warehouse for storage of packs and, if required, printed or sent by e-mail.

The solution adopted allows the performance of high resolution scanning of slabs whose maximum width is 220 cm. This limit is a result of current needs of the market for the processing of natural stones, in that most of the polishing machines in use cannot operate with slab widths greater than 210 cm. Obviously any special needs due to slabs of larger size can be solved rapidly by moving the optical sensor 10 away by means of mechanical or optical actions . Table 1 shows the technical data of the resolution of the optical sensor 10, as well as their variation as the thickness of the slab L increases. It can be seen how,

with greater thicknesses, there is a corresponding decrease in the maximum width that can be scanned and a slight increase in the resolution of the image scanned

(denoted by DPI and equivalent to the number of pixels per inch) .

This is due to the fact that the number of pixels of the optical sensor is set at 10,000 pixels per portion scanned. By decreasing the scannable width, with the number of pixels remaining however unchanged, there is an obvious increase in the DPI resolution.

The solution implemented in the invention allows a row of 10,000 pixels to be scanned in approximately 3 milliseconds. This implies a maximum scanning speed of 333 rows approximately per second, equivalent to 420 cm per minute. This speed allows correct scanning of the slabs of natural stone that slide over the roller assembly 3, ensuring a final image of considerable quality.

For example, in the case of a slab measuring 200 cm x 300 cm, the final image is composed of 10,000 by 15,000 pixels, equivalent to as many as 150 total mega pixels and scanning of the entire slab requires approximately 43 seconds .

The above clearly shows that, thanks to the apparatus for the high resolution scanning of a slab in

stone-like material according to the invention, it is possible to overcome the problems stated above in full. The apparatus described above allows the slabs not to be moved further once grouped into packs and stored in the warehouse. This allows a considerable time and money saving, and the risk of possible damage or breakage of the slabs during the successive handling phases is avoided.

The homogeneity of the exposure conditions entails the obtaining of final images of the slabs, all equally featured by high quality and reproduction accuracy, and perfectly visible in all their details. A very detailed and complete comparison between the various slabs is also possible, allowing a more accurate choice thereof.

Finally the possibility of obtaining high quality scans also allows the performance of a software analysis to check on their quality and colour differences.

In a simplified embodiment of the invention the detection means may consist of a pair of microswitches to detect the presence of a slab. In this case it is, however, not possible to measure the height of the slab, but this may be not an inconvenience in a plant handling stone-like slabs of homogeneous height.

Variations and/or modifications may be made to the process and apparatus for high resolution scanning of a slab of stone-like material according to the present invention without thereby departing from the scope of the invention as set forth in the following claims .