The present invention relates to an optical detection apparatus, i.e., a sensor, for detecting, and in particular counting, the seeds that transit in a seeding tube of a seeder, adapted to be installed along a seeding tube of any seeder of a known type.

Currently, in the field of precision seeding and of row seeding, the most widespread sensors are those based on infrared optical technology, capable of detecting the passage of the seed by barrier effect, or blocking: the seed that transits inside the seeding tube generates an interruption of the infrared beam that is detected by the photodetectors.

The simplest systems are constituted by one or more emitter LEDs located on one side, and by one or more photodetectors (photodiodes or phototransistors) located on the opposite side of the seeding tube.

This solution has some drawbacks, first and foremost the adaptability of the sensor to seeds of different sizes belonging to the various sowable crops (typically from 1 to 7-8 mm in diameter). The choice of the type and number of emitters and receivers is very delicate and in any case does not allow to achieve optimal performance over the entire range of seeds. In fact, a small number of emitters and receivers (typically 3 + 3) does not ensure detection of smaller seeds, which might transit in regions not covered by the beam of the emitters or by the sensitive cone of the receivers.

Vice versa, use of a larger number of emitter LEDs and of more compact photodetectors (up to 4, 6, 8 pairs) allows to reduce the regions that are not covered and to detect smaller seeds, but higher sensitivity when sowing larger seeds is also obtained, with the result that even any small debris can be counted as seeds. In fact, in cheaper sensors of the known type, the signals of the receivers are connected in series and processed with analog electronics to provide a square-wave signal as output. More advanced and expensive systems use a microcontroller that analyzes the signals of the photodetectors individually.

One known system for reducing the regions that are not covered is to increase the characteristic angle of the emitters and receivers. This angle is the one at which the residual luminous intensity/detection sensitivity are 50% of the maximum value. For example, in the case of three light emitters facing three detectors, the central detector receives a normalized amount of light equal to 1.5: 100% of the luminous intensity from the corresponding central emitter (factor 1) plus 50% from each of the two lateral emitters, with an angle at which the sensitivity of the receiver itself is 50% (factor 0.25 x 2). Therefore, a first seed that transits in front of the central emitter interrupting the direct beam generates a dimming equal to a factor of 1, while a second seed that transits laterally interrupting only the diagonal beam generates a dimming equal to a factor of 0.25. Clearly, to take advantage of the diagonal beams as well, it is necessary to increase the sensitivity of the system, with the risk of detecting and counting even small impurities or debris as seeds.

Another drawback arising from the characteristic angles of discrete emitters and receivers is the fact that the shadow generated by the passage of the seed depends on the falling position in the tube: clearly, the seed that falls close to the emitters (thus at the base of the light beam cone) generates a much greater dimming than the same seed that falls proximate to the receivers, where it dims the light beam only partially. The result is that a small piece of debris can be mistaken for a seed and vice versa.

EP3135090A1 describes a sensor which uses a system for shielding the emitter LEDs to reduce their emission cone and limit the effects described above. This disadvantageously entails a loss of total luminous intensity of the emitters and the presence of regions that are not covered between one emitter and the other.

US2015/0293257A1 describes a sensor which uses three emitter LEDs arranged in a vertical direction, whose light is reflected and deflected at 90° inside the seeding tube by an optical element. The receiver element is constituted by a high-resolution linear sensor (photodiodes, CCD or CMOS) which covers the entire width of the tube. The shielding of the emitter LEDs and the shape of the optical element allow to obtain parallel light beams of equal intensity that illuminate the entire cross- section of the tube. The shadow generated by the seed is thus independent of the fall point and the high resolution of the photodetector allows a more accurate analysis of the shape of the seed and of its recognition.

However, with a constant acquisition frequency of the linear sensor, the vertical size of the seed detected by the system turns out to be dependent on the falling speed of said seed. A same object transiting at different speeds (e.g., a seed rebounding inside the tube) generates more or less elongated shapes in the fall direction.

Moreover, the latter is a more expensive system with respect to sensors based on discrete photodetectors, due both to the presence of the linear sensor and to the acquisition electronics. Moreover, mechanically shielding the flux only at its central part produces a loss of total luminous intensity and efficiency.

WO2013/103937A1 describes various configurations and methods that can be applied to precision seeding sensors. In particular, a series of individually driven emitter LEDs is used to achieve a variable light emission profile. The receiver is constituted by a single photodetector that extends beyond the useful section of the tube, or alternatively by an optical element, again of the full-width type, that concentrates the radiating beam onto a single photodetector of reduced size.

This allows to detect seeds anywhere in the tube, to detect the possible passage of overlapping seeds, and to discriminate debris from seeds.

However, in this system shape detection is not possible, and with a single photodetector it is difficult to discriminate two objects that fall at the same instant in two different points of the tube. Moreover, this system cannot discriminate small seeds with respect to dirt that can produce the same overall dimming.

The aim of the present invention is to provide an optical detection apparatus for detecting the seeds that transit in a seeding tube that is capable of solving the problems and overcoming the limitations of the background art described above.

Within this aim, an object of the present invention is to provide an optical detection apparatus for detecting the seeds that transit in a seeding tube that is more accurate and reliable than the background art.

Another object of the invention is to provide an optical detection apparatus for detecting the seeds that transit in a seeding tube that is more versatile than the background art.

Another object of the invention is to provide an optical detection apparatus for detecting the seeds that transit in a seeding tube that is capable of discriminating two or more objects that are transiting simultaneously.

A further object of the invention is to provide an optical detection apparatus for detecting the seeds that transit in a seeding tube that ensures better resolution in discriminating even very small seeds.

Still another object of the invention is to provide an optical detection apparatus for detecting the seeds that transit in a seeding tube that allows to avoid the presence of dark regions where seed passage is not detected and to achieve accurate detection regardless of the fall position of the seeds.

Not least object of the invention is to provide an optical detection apparatus for detecting the seeds that transit in a seeding tube that is easy to provide and economically competitive.

This aim, as well as the objects mentioned and others that will become better apparent hereinafter, are achieved by an optical detection apparatus for detecting seeds according to claim 1.

Further characteristics and advantages of the invention will become better apparent from the description of preferred but not exclusive embodiments of an optical detection apparatus for seed detection, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic view of some main elements of an optical detection apparatus for seed detection, according to the invention, in the configuration for use;

Figure 2A is a schematic sectional view, taken along a vertical plane, of a possible embodiment of an optical detection apparatus for seed detection, according to the invention, in the operating condition for use;

Figure 2B is a top view of the apparatus of Figure 2 A, in which the tube is sectioned along a horizontal plane;

Figure 3 is a perspective view of the optical emission unit of the apparatus of Figure 2 A;

Figure 4 is a sectional view, taken along a vertical centerline plane, of the optical emission unit of Figure 3;

Figure 5 is a perspective view of the receiving unit of the apparatus of Figure 2 A;

Figure 6 is a sectional view, taken along a vertical centerline plane, of the receiving unit of Figure 5;

Figure 7 is a view of an example of a seeder equipped with an optical detection apparatus according to the invention, during use.

With reference to the figures, the optical detection apparatus, generally designated by the reference numeral 1, is used for detecting and in particular for counting the seeds S that transit in a seeding tube 12 of a seeder 200.

In practice, the optical detection apparatus 1 is a sensor of the type commonly known as a photocell (capable of detecting the passage of a seed by barrier effect), adapted to be installed along a seeding tube 12 in an operating condition for use in which it is capable of detecting the seeds S that transit in the seeding tube 12, 120. Advantageously, the optical detection apparatus 1 can be installed in any existing seeding tube 12, 120, both in a single-seed precision seeder and in a row seeder.

The optical detection apparatus 1 comprises an optical emission unit 2, which in turn comprises a light- emitting device 21 configured to emit a light beam 9. The light beam 9 is preferably of the laser type. Even more preferably, the light beam 9 is infrared. In the preferred embodiments, the optical emission unit 2 comprises a single light- emitting device 21.

Preferably, the optical emission unit 2 is configured to emit a collimated beam of light 9, with substantially parallel rays. Advantageously, for example by means of the combined use of a laser emitter 21 and of an optical collimation element 23, the light beam 9 emitted by the optical emission unit 2 is collimated in both directions perpendicular to the propagation direction, so as to have a definite and fixed width and height along the entire propagation path. It is therefore advantageously possible to emit, from the optical emission unit 2, a light beam 9 having a transverse cross-section (along the propagation front) that is substantially rectangular, as shown in Figure 1.

In the preferred embodiments, in fact, the light-emitting device 21 comprises a preferably infrared laser source, which is associated with an optical collimation element 23, such as a lens, that collimates the laser light beam 9 emitted by the laser source.

In greater detail, the optical collimation element 23 can be a lens constituted by a body made of a material that is at least partially transparent to the light emitted by the light-emitting device 21, such as a plastic material or glass. The optical collimation element is therefore positioned in front of the light-emitting device 21 so as to collect and collimate its emitted light.

According to an optimal solution, which is particularly advantageous from the optical point of view because - in combination with the other optical elements described - it allows to obtain a particularly uniform and well-collimated beam of light 9, the light- emitting device 21 is a VCSEL (Vertical Cavity Surface Emitting Laser) laser.

The optical detection apparatus 1 further comprises a receiving unit 3 adapted to receive said beam of light 9, i.e., to be irradiated by it in order to detect it and detect any variations thereof (e.g., the presence of shadow regions) caused by the passage of one or more seeds S.

According to the invention, the receiving unit 3 comprises a holographic film 35 (provided with microroughness on its surface) configured to be irradiated by the light beam 9 so that a projection of the light beam 9 is produced thereon. For this purpose, the holographic film 35 is preferably arranged planar along a projection plane y which, in the operating condition for use, is perpendicular to the direction of propagation of the light beam 9.

During use, i.e., in the operating condition for use, this projection created on the holographic film 35 comprises the shadow of one or more seeds S when they cross the light beam 9.

Essentially, the projection on the holographic film 35 works in a manner that is similar to what occurs in image projection screens of the known type: the microroughness of the holographic film 35 allows to display thereon the projection (i.e., a two-dimensional image) of the incident beam 9, including any shadows.

According to the invention, the receiving unit 3 further comprises an (preferably digital) optical matrix sensor 31 configured to acquire a two- dimensional image of said projection produced on the holographic film 35.

The optical matrix sensor 31 to which reference is being made is a sensor of the known type comprising a set of photosensitive elements (termed active pixels) capable of converting incident light into an electrical signal, such as for example a CCD (Charge-Coupled Device) or CMOS (Complementary metal-oxide-semiconductor) sensor; commonly, said active elements are arranged according to a rectangular matrix whose dimensions may vary as required.

In the preferred embodiments, the optical matrix sensor 31 is a CMOS sensor.

In the operating condition for use, the optical emission unit 2 and the receiving unit 3 are located at two opposite sides of the seeding tube 12 (as shown for example in Figure 2A), so that the light beam 9 emitted by the optical emission unit 2 passes through the section of the seeding tube 12 before reaching the receiving unit 3; in this way, the seeds S that pass through the seeding tube 12, 120 shield part of the light beam 9 emitted by the optical emission unit 2, changing the amount and distribution of the light detected by the receiving unit 3, which can be connected, in a known way, to an electronic control unit which, as a function of the detections made by the receiving unit 3, obtains information regarding the seeds S that transit through the seeding tube 12, 120 (e.g., number, passage frequency, size, shape, etc.) by means of known algorithms. In particular, due to the particularities of the invention, it is also possible to process the detections made by the receiving unit 3 by means of imaging algorithms to perform recognition of the seed S based on the actual shape and size thereof, in particular by analyzing the shadow of said seed projected onto the holographic film 35.

Conveniently, the light-emitting device 21 is arranged along an emission plane a (which in the operating condition for use is arranged substantially parallel to the axis Y of the seeding tube 12 and to the projection plane y).

Conveniently, the optical matrix sensor 31 is arranged along a detection plane 0 (which in the operating condition for use is arranged substantially parallel to the axis Y of the seeding tube 12 and to the projection plane y).

In the preferred embodiments, the receiving unit 3 comprises a support and protection element 38 (which is preferably planar, such as a transparent panel made of glass or plastic material or the like) that is at least partially transparent to the light beam 9 and on which the holographic film 35 is fixed.

In the embodiment shown, the holographic film 35 is fixed to an internal face (i.e., directed toward the matrix sensor 31) of the support and protection element 38.

Preferably, an optical focusing element 33, configured to focus the image of said projection onto the optical matrix sensor 31, is positioned between the holographic film 35 and the optical matrix sensor 31.

This optical focusing element 33 is in practice a lens, or group of lenses, that allows the matrix sensor 31 to acquire the image projected onto the holographic film 35 by transferring it thereon while keeping the conjugate points fixed, such as for example a relay lens.

In some embodiments, including the one shown in Figures 2 to 6, the optical emission unit 2 comprises a containment body 20 (e.g., a box-like body) that includes the light- emitting device 21 and comprises an emission window 29 that is crossed by the light beam 9 emitted by the light-emitting device 21, in output from the optical collimation element 23 when present.

Optionally, the emission window 29 is closed by a transparent protective panel 28.

In some embodiments, including the one shown in Figures 2 to 6, the receiving unit 3 comprises a protective body 30 in which the optical matrix sensor 31 is accommodated and which comprises a reception window 39 for the passage of the light beam 9 toward the holographic film 35.

Preferably, the reception window 39 is at least partially occluded by the support and protection element 38.

Advantageously, the holographic film 35 can be extended over the entire width d' of the seeding tube 12, and the optical emission unit 2 can be configured to emit a beam of light 9 that covers the entire width d' of the seeding tube 12, so as to obtain a continuous light emission over the entire width of the passage section d, d' in which the seeds S transit.

In some embodiments, such as the one in Figures 2-6, the optical emission unit 2 and the receiving unit 3 are two separate and independent elements (not mechanically coupled) so that they can each be fixed to one of two opposite sides of an existing seeding tube 12 so as to face its interior, for example through adapted openings 13 A, 13B in the wall of the tube 12 (typically circular openings with a diameter of 18 mm).

For this purpose, it should be noted that the box-like bodies 20 and 30 are provided with protruding circular portions or flanges 27, 37 adapted to be inserted in the openings 13 A, 13B in the wall of the tube 12.

The optical detection apparatus 1 can therefore be configured in an operating condition of use (shown in Figure 2 A) in which the optical emission unit 2 and the receiving unit 3 face the interior of a seeding tube 12 so that the light beam 9 emitted by the optical emission unit 2 reaches the receiving unit 3 by crossing the seeding tube 12 transversely.

In this condition, the holographic film 35 preferably extends over the entire width of the passage section d' of the seeding tube 12, and the lightemitting device 21 is configured to emit a light beam 9 that extends transversely across the entire width of the passage section d' of the seeding tube 12, so that the light beam 9, in propagating from the light-emitting device 21 to the holographic film 35, covers the entire width d' of the passage section of the seeding tube through which the seeds S pass.

Preferably, in the operating condition for use, the emission window 29 and the reception window 39 extend across the entire width of the passage section d' of the seeding tube 12.

The operation of the optical detection apparatus 1 for detecting the seeds that transit in a seeding tube is clear and evident from what has been described.

Advantageously, in the optical detection apparatus 1 according to the invention the projections of the shadows generated (on the holographic film 35) by the passage of the seeds S through the seeding tube 12 (and detected by the matrix sensor 31) are found to be well-defined and with a size that is independent of the fall, even in the case of multiple seeds S passing through the light beam 9 at the same time.

By virtue of the described particularities, the optical detection apparatus 1 is able to acquire the actual shape of the seed S without alterations caused by the speed of its passage (as occurs in systems with discrete and linear receivers). Shape recognition thus allows to discriminate any debris from seeds S and to discriminate particular situations in which two or more seeds S transit overlapping each other.

The optical detection apparatus 1, according to the invention, can be installed in any seeder 200 comprising at least one seeding tube 12, 120 through which the seeds S to be sown transit, arranged along said seeding tube 12, 120.

For example, Figure 12 shows a seeder 200 of a known type, comprising a hopper 271 for feeding the seeds S, a blower 272 for generating an air flow for conveying the seeds S, in which along at least one of the seeding tubes 120 (only one is visible in the figure, but there may be a plurality) an optical detection apparatus 1 according to the invention is positioned.

In practice it has been found that the optical detection apparatus for detecting the seeds that transit in a seeding tube, according to the present invention, achieves the intended aim and objects, since it is more accurate and reliable, as well as more versatile, than that the background art.

Another advantage of the optical detection apparatus according to the invention resides in that it is able to discriminate two or more objects that are transiting at the same time.

A further advantage of the optical detection apparatus according to the invention is that it provides better resolution in discriminating even very small seeds. Another advantage of the optical detection apparatus according to the invention resides in that it avoids the presence of dark regions in which the passage of the seeds is not detected and it achieves accurate detection regardless of the fall position of the seeds.

Still another advantage of the optical detection apparatus according to the invention resides in that it is easy to provide and economically competitive.

The optical detection apparatus for counting the seeds that transit in a seeding tube thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the accompanying claims.

All the details may furthermore be replaced with other technically equivalent elements.

The disclosures in Italian Patent Application No. 102021000032771, from which this application claims priority, are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.