NL1015994C2 - Mechanical sorting and division of plants using artificial light and matrix of light-sensitive elements to determine root development - Google Patents

Abstract

Plants are carried on a belt (3) into an enlosure (8) illuminated by monochromatic light. A matrix of light-sensitive (e.g. CCD) elements produces a two-dimensional image and detects gradation of light or wavelength on a scale varying from zero for white and 256 for black. Sensitivity is adjustable to distinguish the contrast between roots and the band background.

Description

Title: Machine plant sorter as well as machine plant sorter method. Firstly, the invention relates to a machine, especially automatic plant sorter, and a machine, especially automatic plant sorting method, in particular, but not exclusively, for sorting perennials, such as dicentra, lupine, astilbe, hosta, etc. In particular, the invention is suitable for sorting divisible perennials. As a rule, such perennials, after being grown to a large size, are divided into two or more viable clods for further cultivation or sale to the consumer. The term "perennial" therefore means in this connection in particular a plant belonging to the type whose root ball is divisible into viable parts.

A manual plant sorter is known, in which clods are sorted manually with the aid of a number of persons, the sorting being carried out on the basis of the number of crop sprouts, also called "noses". A nose is an above-ground growth core from which a new above-ground fruit (eg leaves and / or flower stems) can develop. This sorting method is laborious and of varying quality. In addition, the inventor has determined that sorting by the number of noses provides a large volume spread for the individual plants within one sort. In other words, plants sorted by the same number of noses can range from very large to very small. 30 These large dimensional differences within the same sorting lead to problems with handling after sorting, such as packaging, storage and offering for sale, for example by retailers to the consumer.

The object of the invention is a method and apparatus with which the sorting of plants, in particular perennial plant types, can take place quickly and with constant quality.

To this end, it is proposed to use an image recording device which makes an image recording of the 40 plant to be sorted and sends image signals relevant to the image recording to 1015994 2 a processing device which processes those image signals into sorting signals which can be passed on to a control device which is suitable for ensures that the plant concerned arrives at a location corresponding to the sorting. Preferably, an area value of the plant is determined by means of the image recording, more in particular of a specific characteristic of the plant, such as the surface occupied by certain roots of the plant. The inventor has discovered that the size of certain roots is representative of the plant's sizing size. The inventor has also discovered that these roots lend themselves particularly well to automatic detection by taking an image. In this way, the sorting becomes at least less dependent on disturbing influences such as the amount of adhering sand, clod shape, etc.

The signals are machine-readable and therefore electronic or magnetic in nature. The signal processing is preferably digital and can take place with a computer with CPU, working memory (RAM) and permanent memory (ROM, optionally extended with external memory, such as a magnetic disc or a so-called compact disc). The computer communicates through one or more communication ports, such as buses with peripherals, such as keyboard, image pick-up device, monitor, printer, plant path control. That communication may be wireless.

The image recording device may contain a CCD-type sensor, ie a sensor consisting of a predetermined two-dimensional pattern of a large number of photosensitive elements (the CCD elements) arranged side by side, each of which has a light intensity and / or - received by that element. wavelength 30 output corresponding signal. By "light" here is meant both the electromagnetic spectrum visible to the human eye and the spectra on either side just outside (infrared and ultraviolet region). Preferably, the sensor is sensitive only to differences in brightness, so that the signals from the image recording represent a combination of gray tones, varying between all white and all black.

Preferably, the image signal processing is arranged to determine the number of CCD elements receiving light within a predetermined strength and / or wavelength range. In a further development, that number is determined for at least two different such areas. These numbers can be used as a measure for sorting or in further data processing. For example, those numbers concern the all-white and all-black grays, which together represent, for example, the total area of at least a part of the plant, while the value obtained by dividing the number of black grays by that total area, the sort value proposes. Preferably, with the aid of adjusting means, the boundary is adjustable between the at least two different regions, in order to be able to adapt the system sensitivity to the processing of different plant species. For example, one plant species has darker colored roots than the other. In the current state of the art for digital processing of image recordings, a distinction is made between 256 gray values, the extreme values of which are those of the colors white (no. 0) and black (no. 256). The light color that a photosensitive element of the image pick-up device receives from the plant and / or conveyor belt determines the rank 20 within the grayscale system. The system sensitivity can be set so that, for example, all grayscale from No. 128 represents wave energy from the plant, while grayscale No. 0 to 127 represents wave energy from the subsurface. Counting all 25 grayscale # 128 and above gives a measure for the plant. For another plant type, the limit can be set to a higher or lower gray value than No. 128, for example, using a hand-turned potentiometer connected to a suitable input on the computer.

Preferably, the image is taken in an artificially lit environment, preferably with as much light of the same color as possible. An example of a light source that can provide this is the commercially available OSRAM DULUX EL reflector energy saving lamp. Thus, the exposure 35 can be made independent of varying conditions, such as caused by, for example, a sun-sliding cloud. In particular, the image recording is made in an at least substantially light-tight housing of preferably compact size. The exposure means are preferably 1015994 4 high-frequency type lamps operating at a supply voltage higher than 60Hz, in order to ensure the most uniform illumination possible.

The image recording is preferably made with a high contrast 5, which is preferably done by taking preferably highly overexposed images. It has been found that a characteristic of the appearance of the plant, which is representative of the sorting, such as certain roots, in particular the main roots, can therefore be clearly distinguished in terms of equipment. When working with a light surface (such as a white conveyor belt) on which a plant with light roots lies, it is preferable to allow so much light into the image pick-up device (for example by opening the diaphragm further or less) that the root is so dark as possible and the background as white as possible is registered by the image recording device. This creates a hard contrast, as a result of which the system operation is less sensitive to brightness and / or color differences of the substrate (for example caused by contamination), while not every hair root has an influence on the result. Moreover, it is preferable that one image recording is made with high image sharpness, for which purpose a focusing lens with variable focal length can be used.

For example, instead of making the image recordings with large image contrast, it is also possible, based on the image contrast recorded by the image recording device, to adjust the image contrast to a desired level in software. For example, the shutter speed, brightness and aperture size of the camera are such that an image is taken with normal exposure, which is then processed with suitable software into an overexposed image. Incidentally, bringing the image contrast to a different level requires a relatively large amount of computer memory and computer operations, which places high demands on the equipment to be used and thus entails high costs.

The invention is further elucidated hereinbelow on the basis of a non-limiting exemplary embodiment and with reference to the appended drawing. Figure 3 shows a schematic top view and Figure 4 shows a schematic side view of the automatic plant sorting device. This comprises a feed path for the plants, formed by an endless conveyor belt guided round roller with top and bottom part, one of the return rollers being driven by a speed motor which is infinitely variable (not visible). Along its length, the conveyor belt includes a plurality of at least substantially fixed pitch detection points which cooperate with a fixed position proximity switch (not visible), the operation of which is explained below. The device further comprises a camera housing, a blower (not visible) and four chutes. Inside the camera housing are one or more lamps and a camera (not visible). The lamps are aimed at the part of the upper part located inside the camera housing, so that at least the surface thereof on which the plant to be sorted lies at the moment the image is taken is illuminated as uniformly as possible. The camera contains a CCD chip, a shutter with an adjustable shutter speed, an adjustable aperture 20 and a lens and is arranged in such a way that at least the homogeneously illuminated upper part (or a part thereof; preferably at least the part thereof on which the plant lies on the moment of image capture) and preferably an area up to 10 cm above the upper part is sharply imaged on the CCD chip.

In a practical test, the shutter speed was 1ms, the light intensity on the plant was more than 5000 Lux, and the light intensity on the lens was 3000 Lux.

Peripherals and control equipment, such as computer, control panel, monitor, etc., are not shown.

During normal operation, the upper part moves in the direction from left to right in the drawing of fig. 4 and a plant lying on the upper part successively passes through the camera housing and one by one the chutes.

Below the conveyor belt is a plant feed belt, which is wider than the conveyor belt and, like the conveyor belt, is a belt guided in an endless, elongated loop, which, as is usual with this type of conveyor belt, at the end ends around a respective turning roller . The. 1015994 6 upper parts of the conveyor belt and the plant supply belt move in the same direction. Perennials are supplied to the upper part, each of which is taken up successively by an operator. The operator ensures that one plant is placed in the correct position each time. Preferably, the plant is laid down in such a way that it is level with a detection point. This simplifies the adjustment of the machine: if the image recording of the image recording device is made to contain the detection point 10, it will also contain the paint. Alternatively, a plant can then be placed between two consecutive detection points of the conveyor belt in the direction of travel. At the downstream end of the plant supply belt there is a receptacle for dirt, such as sand and soil, remaining on that belt 15.

The operation is now as follows: According to the position of the detection points, exactly one plant is placed on the conveyor belt for each detection point. As soon as a detection point reaches the proximity switch, the former activates the latter and sends a detection signal to the computer which, in response to receiving that detection signal, in turn sends a control signal to the camera, which in response opens the shutter for a predetermined time for exposing its CCD sensor during a predetermined shutter speed, so that an image is made of the above-mentioned part of the upper part inside the camera housing. The opening of the shutter can immediately, or with a predetermined time delay, follow the release of the detection signal. Optionally, the proximity switch can send its detection signal directly to the camera, which opens the shutter in response to receipt of that signal. The camera can further pass on the detection signal, or a signal derived therefrom, to the computer, so that in that case the computer is not directly connected to the proximity switch. Detection points and proximity switch thus form a plant position detecting means, which ensures that an image of one plant is made at a time, whereby the image of the whole plant is made. An alternative embodiment of the plant position detecting means is also within the scope of this invention.

Optionally, it is reasonable that from detection of the detection point a time related to the belt speed of the conveyor belt 5 (for example proportional thereto) elapses before the image recording is made. To this end, the computer can receive signals from a pulse generator rotating with one of the return rollers, for instance, and the time course is determined by the time required for the pulse generator to deliver a predetermined number of pulses. In this alternative embodiment it can be avoided that during start-up with an empty conveyor belt a number of images are taken in succession of successive parts of the conveyor belt on which no plants are yet lying.

15 On the basis of the image recording, the computer calculates to which sorting the plant concerned belongs.

In the meantime, the conveyor belt has transported the plant further downstream so that the plant passes through the larynxes. Depending on the grading assigned to the 20 plant, it is placed in one of the four chutes. This is done with the blower. In a manner not shown in more detail, this comprises four individually closable nozzles, each of which is oriented such that they can blow a plant into a chute belonging to the relevant nozzle. The computer now only opens the nozzle at the right time, which belongs to the chute in which the plant in question must end up. Incidentally, this may mean that more than one blow nozzle is open simultaneously because, because of the sorting, a downstream plant must be placed in a downstream chute and at the same time a plant located upstream in an upstream chute.

It will be clear to a person skilled in the art how, based on the detection signal from the proximity switch and the movement speed of the upper part and the location of the relevant chute, the computer can determine the time at which the operating means (in this embodiment the nozzle). must be energized in order to bring the plant into the relevant receiving member (in this embodiment the chute).

1015994 8

It will also be clear to those skilled in the art that under the chute a crate or the like. can be placed in which the sorted plant is collected. The computer can also count the number of plants placed in a given chute and make a decision accordingly, for example, close the chute when a predetermined number of plants have been placed therein, so that the crate placed underneath must first be replaced by an empty one before opening the chute again. With a suitable signal, operating personnel can be made aware of the fullness of the crate. While the chute is closed, it becomes filled with plants when the device remains in operation. If the crate is not changed quickly enough, the computer can then conclude that the chute is overfilling and accordingly issue an alarm or even stop the device. As such, the chute has both the function of sorting guide means and storage means.

For example, the following 20 grades can be used with four chutes: Grade A (less than 15000); grade B (less than 20000); grading C (less than 26000) and grading D (from 26000). The unit of measurement can be the measured number of pixels of a given gray scale or "blackening" area.

The conveying surface of the conveyor belt preferably has a light colored, such as white, surface. Preferably, during start-up, the conveyor belt is first inspected with the camera (initialization) for local color or brightness deviation, for example caused by dirt. If the color or brightness homogeneity and / or the color or brightness of the conveyor belt deviates too much from the desired value, the sorting result may be affected, in particular when the sorting is based on measured brightness differences. Then the transport surface will first be treated, as must be cleaned. It is possible that the device may give an error message in this connection and only start sorting when it has determined that the measured value of the conveyor belt with regard to the color and / or brightness has entered the prescribed desired area • J0 15994 9. During this initialization, in the same manner as described above, the camera can take successive areas of the upper part to take images that the computer evaluates for brightness and / or color to decide, once all consecutive areas of the upper part have been sampled, whether the conveyor belt is clean enough.

Preferably, the level (standard value) of the desired brightness or color and / or the homogeneity of the conveyor belt is adjustable with the aid of adjusting means, such as a manually operated potentiometer connected to a suitable input of the computer, so that, for example, depending on the type of plant being sorted, the system operation can be set more or less sensitive to contamination of the transport surface. Thus, for a plant whose color of the roots is more similar to that of the transport surface, the sensitivity of the system to contamination of the transport surface will be greater and thus the norm value will be higher and the pollution limit correspondingly lower. A large number of basic settings is preferably stored in memory means, for instance for each plant type expected to be processed with the device. Preferably for at least five, more preferably for at least ten, most preferably for at least twenty different plant species, the relevant basic setting is stored in machine memory means, such as the permissible contamination limit of the conveyor belt, the height of the threshold by which the system distinguishes between a pixel belonging to the conveyor belt or to the plant. The memory means can also store data from a completely clean conveyor belt. This allows the system to evaluate the degree of contamination of the conveyor belt. On this basis, the system can automatically indicate that the conveyor belt must be cleaned, even if the degree of contamination has not yet reached the permissible limit.

A plant treatment plant, such as a plant sharing plant, or a plant washing plant or a vibrating plant to pass the plants over a vibrating sieve bed, remove excess sand and soil from this sorting device.

1015994 10

EXPERIMENTS

In a first experiment, a number of black and white images were taken with the system of the invention of the root ball of the variety astilbe (dark roots) on a white background with three running away from a central point under the plant in star shape black lines. Fig. IA shows the display of the image recording in 256 shades of gray with the correct exposure. Fig. 1B shows the image recording of FIG. 1A after processing in which all grays below 128 are set to value 0 and all 10 grays from 128 to value 256. The computationally disruptive details, such as hair roots and soil debris, have essentially disappeared, and the main shape and size of the root ball are preserved. Fig. 1C shows a representation according to FIG. 1B, but with too much overexposure. Disturbing details disappear even more, but also important details of the root ball. Insufficient reproducibility is guaranteed. Fig. 1D shows a view according to FIG. 1B, but with underexposure. Disturbing details strongly affect the desired result.

In a second experiment, the variety dicentra was used and otherwise proceeded as in the first experiment. Fig. 2A is a view similar to FIG. 1A, FIG. 2B is a representation according to FIG. IB. Fig. 2C is a representation according to FIG. 1C. The same conclusions as in Fig. 1 can be drawn.

LIST OF REFERENCE FIGURES IN THE DRAWING 1 detection point 2 blower 3 conveyor 4 dirt trap 30 5 chute 6 monitor 7 control panel 8 camera + lamp housing 1015994

Claims (5)

Device for automatically sorting plants, comprising a conveyor track (3) along which plants 5 to be sorted are successively advanced in a flow; two or more outlets (5) with selection means for optionally guiding a plant from the conveyor path to one of the outlets; upstream of those drains an at least substantially light-tight housing (8) 10 through which the conveyor path extends, with an assembly of artificial light source with at least substantially one color light and image pick-up device with CCD sensor within the housing, directed at the conveyor track, so that within that housing a recording 15 can be made with said CCD sensor of said image recording device of a plant moving along said transport path and illuminated by said artificial light source; an electronic digital data processing device coupled in a data-transmissive sense to the image pick-up device which receives therefrom electronic or electromagnetic image signals 20 for processing on a gray scale basis into a value representative of the area occupied by the roots of the plant, on the basis of the number exposed by the image recording CCD elements of the image pick-up device to which a gray value is attributable, belonging to a predetermined area, such as above a predetermined value between 0 and 256, and, depending on that number, to transmit a corresponding electronic or electromagnetic signal to the selection means around the plant to lead to the drain corresponding to the determined size; and upstream of the housing a station for successively laying plants on the conveyor track with mutual spacing. Apparatus according to claim 1, wherein the settings of artificial light source, image pickup device and data processing unit are such that the image contrast is great. Device as claimed in claim 2, wherein for the purpose of the greatest possible image contrast the transport path is at least substantially white in color. A method of operating the device according to claim 1, 2 or 3, wherein the roots of plants to be sorted along the 1015994 conveyor conveyor, belonging to one of the following species: dicentra, lupine, astilbe, hosta, are imaged made inside the light-tight housing, preferably at an adjustment of artificial light source 5 and image pickup device such that a highly overexposed image shot of the plants is made. 5. A method according to claim 4, wherein such a large amount of light is admitted to the image recording device that the root is as dark as possible and the transport path is registered as white as possible by the image recording device. 1015994