Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR SORTING OBJECTS BY SHAPE
AND APPARATUS FOR THE IMPLEMENTATION THEREOF
Description
Technical field
This invention relates to a method and an apparatus for sorting different
objects into limited number of the classes according to their shape. The
present
invention may be specifically applied to processes of sorting (grading)
gemstones, particularly raw diamonds, by their shape, and in apparatuses for
sorting (grading) gemstones.
Prior art
Known methods for sorting objects by their shape and other
characteristics are based on the following general principles: transporting
plurality of the objects one by one through a viewing zone by a special means,
illuminating individually each of the objects passed through the viewing zone,
capturing an image of the object shape or registering an object response to
illuminating in a sensing detection means, preprocessing and converting the
captured image (signal) to the digital form, analyzing of an information
received
by such way in a calculating means for assessing complains with or not the
predetermined set of parameters which identifying belongings of the objects to
the particular class, making a decision and then generating a command to an
actuator for dispensing the object in a corresponding collecting bin of the
objects of one of the classes according to the selected classification..
There is a known apparatus for automatic classifying crystal objects (for
example, rough diamonds) by color or purity (US Patent 4,951,825, IPC BO7C
5/342, BO7C 5/36, published on 28.08.1990), where a feed system is configured
as a combination of a vibratory bowl feeder and a rotary wheel structure with
a
system of suction ports. The apparatus has an illuminating ¨ viewing zone,
comprised illuminators and detection means, and further a collecting bin for
the
objects with the number of outlets according to the selected classification.
The
apparatus operates as follows. The vibratory feeder lines up the objects from
an
unclassified mass along a feed path. The rotary wheel structure feeds objects
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by objects to be classified to the illuminating ¨ viewing zone where receiving
the
information for making a decision about the classification is provided by
means
of the illuminators and the detectors of a light being passed (reflected)
through
(from) the objects. Then said rotary wheel structure feeds the object to a
sorting
apparatus provided to direct the object by a command of a calculating means to
outlet bin according to the object class. The above-mentioned invention has
obvious drawbacks in case the classification characteristic is the object
shape,
for example, the shape of a rough diamond crystal. The complete analysis of
the shape would require increasing number of the registered devices (cameras)
in the viewing zone while part of the objects being in the suction ports
cannot be
viewed completely.
In an sorting apparatus (Patent RU 2016672, IPC BO7C 5/342, GO1N
21/87, published on 30.07.1994) it was attempt to complicate the construction
of
the vacuum rotary conveyer in order to the maximum part of surface of the
object can be viewed by means of rotation of the object (crystal) around its
axis
during passing the view zone of an optical measurement system. Said
apparatus may be used in sorting objects by their shape. However this
invention
has the critical drawback of the transport system, based on the rotary
conveyer,
- part of the object in the suction port still cannot be viewed.
Other drawback of the described inventions and methods implemented
by them is low performance, less than 5 ¨ 10 objects per second.
A prior art apparatus for sorting diamond crystals (Patent RU 2424859,
IPC BO7C 5/342, published on 27.07.2011) comprising an assembly configured
to feed the crystals one by one and a horizontal bowl feeder. This apparatus
consists of the means for illuminating and viewing, a control and calculating
means and an executing sorting means to direct the crystals to bins according
to the classification criteria. Illuminating the object and receiving the
information
about its shape is performed on the horizontal bowl feeder. The control and
calculating means processes the received information and issues to the sorting
means a command for directing the crystal to the bin according to its
determined shape. The drawbacks of this invention are follows: the low
performance, an incomplete visibility of a crystal on the surface of feeder, a
possible irregularity in feeding the crystals to the viewing zone.
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A technical solution, provided to obtain the high performance and
complete viewing the object, is analysis of its shape in the freefall phase.
The
prior art discloses a method and a device for shape sorting. (US Patent
5,184,732, IPC BO7C 5/342, published on 09.02.1993). According to the
method each object to be classified is fed to the viewing zone in the freefall
phase. The image of the object profile (silhouette) is registered
simultaneously
by plurality of illuminators and viewers which are arranged in the viewing
zone
in one plane around the viewing zone and normally at 900 to the direction of
feed of the objects. A calculating means based on the hierarchic algorithm
ascertains the shape classes of the object while the object falls from the
viewing
zone to a sorting zone positioned below. For example, for row diamonds it may
be 16 different classes.
The above-mentioned invention also discloses a sorting machine for
classifying a succession of objects according to shape comprising the viewing
zone through which the objects freefall. In this zone the illuminators and
viewers
for further processing according to the hierarchic algorithm in order to
ascertain
the shape class of the objects passed through the viewing zone are located.
The machine is provided a sorting assembly to dispense the objects classified
by the shape into the collecting bins according to each shape class. The
performance of the machine achieves ten crystals per second and more, till
twenty crystals per second. In addition the quality of sorting, defined as
percent
of the crystals to be subject to manual sorting after passing through the
machine from their total quantity, is low, about 30% for crystals with size
from
1/15 to 4 carats.
The main drawback of said method and machine is the relatively high
percent of the crystals unclassified automatically and must be subject to
manual
sorting. The misclassifications are determined both by a hardware
implementation of the method and the algorithm of an identification process of
the shape class implemented by the calculating means. However positioning of
the illuminators and registered cameras in one plane and processing of the
image of the object as it falls where the image has been received
simultaneously for each registered devices, substantially can not exclude the
identification mistake as result of an unpredictable random variation of
position
of the object during falling at the moment of registering the silhouette
shape.
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Increasing the number of the illuminators and registered devices (cameras)
positioned coaxially with the illuminators is limited by a construction and
doesn't
result in a proportional reduction of a probability of the identification
mistakes,
also because of increasing a data massive to be processed.
The prior art contents an apparatus and method for inspecting
gemstones (application PCT/EP2013/055165 "GEMSTONE INSPECTION",
applicant DE BEERS CENTENARY AG, priority date 16.03.2012). The
apparatus comprises a vacuum nozzle for picking up gemstones from a supply
of gemstones, wherein the vacuum nozzle comprises a central bore for
supplying a vacuum, said bore is made from transparent material for
measurement of the stone optical properties and also is configured to be
manipulated for changing the orientation of the gemstone; a transport
mechanism configured to rotate around a hub and comprises an array of the
nozzles for transporting the gemstone that is held by latter to a measurement
location; a measurement system; a control system, operatively coupled to the
vacuum nozzle and measurement system and configured so that the gemstone
arrives at the measurement location at the predetermined time; a positive
pressure application system is provided for releasing the gemstone from the
nozzle at an ejection location.
The method for inspecting gemstones comprises the steps of picking up
the crystal objects from a supply means of objects; performing measurement of
the gemstone properties while the gemstone being conveyed and held on the
moving vacuum nozzle in one or more measurement points or while gemstone
freely falls; releasing the gemstone into a bin selected from plurality of the
bins
in dependence on the measured properties of the gemstone.
In the proposed method for sorting gemstones one of measurement
device includes a collimated light source and viewing means arranged so that
gemstones on the nozzle passes between the light source and the viewing
means so as to obtain a series of silhouette images of each gemstone with
further reconstructing in computer a 3D model of the shape of each stone from
the series of images. The image is captured at the different angles with the
light
source. The drawback of said method is present of catchlights in the viewing
means and, correspondingly, obtaining the nondistinct image of the stone
because of position of the light source and the viewing means, and
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simultaneous capturing the image by each of the measurement device that
results in increasing number of the mistakes in identification of the gemstone
shape and increasing the percent of unclassified objects.
In another embodiment of above-mentioned invention the measurement
device includes a diffuse light source and an array of cameras at the
different
locations as well below stone and also a means for rotating the nozzles
holding
the gemstone around its axis for identifying the color of the stone.
One of the measurement devices comprises a spectrometer to determine
a photoluminescence spectrum of the gemstone.
All apparatuses and methods implemented by their according to above-
mentioned invention determine the classification characteristics of the
gemstone
held on the nozzle and, correspondingly, have the same drawbacks, indicated
above, that is the lack of possibility to obtain the complete image of the
object
shape and the increased percent incorrectly classified crystals. In the
description of the invention a method and an apparatus mentioned but not
disclosed properly, for determining the classified characteristics of
gemstones,
for example, the shape, in which determining is performed during the freefall
phase. So the described method and the apparatus would still have the main
drawback - the low performance of sorting.
The prior art discloses a sorting apparatus for sorting rough gemstones
"Sorting aggregate material" (International application PCT/EP2013/055240,
applicant: DE BEERS CENTENARY AG", priority date 16.03.2012, published on
19.09.2013) which have been chosen as the prototype. This apparatus includes
a transport system for individually transporting a crystal object to a
measurement location comprising a rotatable carousel which the stone is being
held on by a vacuum nozzle; a measurement system configured to determine
the properties of the object, in general, diamonds, being held by the vacuum
nozzle, that is one or more of: identification of the diamond, quality of the
diamond and its shape; a dispenser system configured to dispense the
gemstone from the transport system to one of a plurality of locations in
dependence on the determination of the measuring system.
The measurement system is configured to determine the shape of
gemstones comprising the plurality of cameras arranged in a circular array in
one plane or in a spherical array in relation to the measurement location
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(viewing location). The transport system is designed to feed and rotate the
gemstone to be classified to the measurement location (viewing location).
The transport system is configured to move the gemstone from the
measurement location (viewing location) at the second level, on which the
stone
is being released in a particular cell by a multi-way carousel of the first
and
second level in dependence on the made classification decision.
In this method for sorting crystal objects (gemstones) by the shape, the
object is held by nozzle while the measurements is being performed that
essentially may result in the mistakes in identifying the shape as the
gemstones
silhouette is not completely viewed, and also limit a sorting rate of the
objects
by the shape.
The above indicated problems may be solved by the proposed invention.
Disclosure of the invention
The object of the present invention is to propose method and apparatus
provided the high performance of sorting objects by the shape.
The technical effect is to provide the high performance of method for
sorting objects by the shape classes and simultaneously reduce the percent of
misclassifications expressed in the quantity of objects to be subjects for re-
sorting or manual sorting.
The technical effect of the present invention is achieved by that the
proposed method for sorting objects according their shape comprising the step
of feeding objects one by one to an illuminating - viewing zone in the
freefall
phase, capturing images of the objects in the emission of illuminators by at
least
eight electronic image capture devices; processing the captured images by a
calculating means to classify the object shape according to one of the
predetermined shape classes; generating a command to be issued to a sorting
actuator configured to dispense the object into a collecting bin corresponding
to
its shape; further comprises the following step ¨ sequential activating each
individual pair of "illuminator - image capture device", from the first pair
till the
eighth pair, while the object is on the freefall trajectory in the
illuminating ¨
viewing zone to capture the images of its shape.
In the preferred embodiment of the present invention high-speed
electronic cameras configured to pre-process the image to derive a profile of
the
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object shape directly in a camera processor may be used as the image capture
devices.
The technical effect is also achieved by that in the apparatus for
implementation of the method for sorting objects by the shape comprises an
assembly configured to form succession of the objects and feed the objects, an
illuminating ¨ viewing zone, a sorting zone and the calculating means
processing the images of the objects being classified as they passes through
the viewing zone, furthermore there is special positioning of pairs
"illuminator ¨
image capture device": at least eight pairs "illuminator ¨ image capture
device"
are positioned in different planes and equally spaced on the sphere around the
intersection point of the freefall trajectory of the object and the optical
axes of
pairs "illuminator¨ image capture device"
A process of capturing the images starts at the command of the first
sensor arranged at the point of arrival of the object to the illuminating ¨
viewing
zone when said sensor signals arrival of the object to the illuminating ¨
viewing
zone. The object is in the freefall phase. Then each individual pair of
"illuminator - image capture device", from the first pair till the last pair,
is
sequentially activated while the object is in the illuminating ¨ viewing zone.
At least eight pairs of "illuminator - image capture device" is used during
capturing images. The illuminators and the image capture devices are
synchronized by pairs. The illuminators are configured to emit the infra-red
light
for providing maximum contrast of the images.
Digital preprocessing of the captured images of the object profile in the
electron image capture devices is carried out in order to increase the
contrast of
the images.
The apparatus for sorting objects by the shape consists of an assembly
configured to feed the objects to the free fall trajectory one by one,
comprising a
vacuum rotary transporter and two vibratory feeders, an illuminating ¨ viewing
zone, a sorting zone with the collecting bins and the calculating means for
processing the captured images of the object. In addition the sorting zone
includes a buffer carousel with pockets intended for temporary storage of the
objects until they will be classified and dispensed by the air blast means
into the
collecting bins according to the objects shape class.
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The apparatus for sorting objects by the shape is characterized that the
illuminators and the image capture devices are arranged in the different
planes
around a part of the freefall trajectory of the object and at the different
angles to said
trajectory that provide to obtain the most complete information about the
object, form
the images of the object and reduce the number of misclassifications. In
addition,
capturing the images of each object being passed is carried out by the
sequential
activation of each individual pair of "illuminator - image capture device" as
the object
is in the viewing zone, such activation allows to prevent catchlights on the
cameras
from the surrounding illuminators, optimize time of processing the captured
images
that also can reduce the number of misclassifications and, correspondingly,
improve
the performance of the sorting process.
Brief description of the drawings
Fig. 1 is a block diagram of the apparatus according to the present invention.
1 ¨ a vacuum rotary feeding transporter;
2 ¨ a big vibratory feeder configured to form a succession of objects;
3 ¨ a small vibratory feeder;
4 ¨ a sensor of arrival of object to the illuminating ¨ viewing zone;
¨ image capture devices (cameras);
6 ¨ LED illuminators;
7 - a sensor of arrival of an object to a sorting zone;
8 ¨ a buffer carousel with pockets;
9 ¨ a collecting bin according to classes of the object shape;
¨ air blast means dispensing the objects into collecting bin corresponding
their shape.
Description of the preferred embodiment
The method for sorting objects by the shape comprises the steps of feeding
the objects to the freefall trajectory, passing by the object the illuminating
¨
viewing zone, sequential activating of each individual pair "illuminator ¨
image
capture device", capturing the object images, processing
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the images of the object shapes being captured by the calculating means,
passing through the sorting zone with the collecting bins.
The apparatus for implementation of the proposed method comprises an
assembly configured to feed the objects to the freefall trajectory one by one,
consisting of the vacuum rotary transporter 1 configured to feed the objects
and
two vibratory feeders configured to form succession of the objects ¨ the big
vibratory feeder 2 and the small vibratory feeder 3, that provide an uniform
variable reproduced feeding the objects to the illuminating ¨ viewing zone
along
the freefall trajectory. First optoelectronic sensor of arrival of the object
to the
illuminating ¨ viewing zone 4 is mounted in the point of arrival of the object
to
the said zone and designed to activate a synchronized process of sequential
capturing the images of the object by each of cameras 5. Illuminating the
object
is performed by the LED illuminators 6 in the infrared band of spectra in
order to
provide the maximum contrast of the images. The LED illuminators 6 provide to
obtain the images of the high quality by the cameras 5 in the point of the
freefall
trajectory of the object in the illuminating ¨ viewing zone and are activated
sequentially and synchronously. Sequential capturing the images provides both
to optimize the time for processing and avoid catchlights from surrounded
cameras distorting the image. Also a microprocessor of the electron cameras
performs digital preprocessing of the captured image of the profile object in
order to increase the contrast. A loading of this preprocessed information
about
the object shape as the digital images to the calculating means begins from
the
moment of receiving the information from the first camera and ends after
receiving the information from the last camera. Then the object is identified
by
the predetermined shape class or the decision about inability of
identification of
the object shape is made. After passing the second optoelectronic sensor of
arrival of the object to the sorting zone 7 the object falls into one of the
pockets
of the buffer carousel 8, number of which is send to the calculating means. By
the moment when the pocket achieves a coverage area of the air blast means
10, the calculating means determines the shape class of the object and then
the
object is dispensed by a pneumatic impulse of the air blast means 10 into the
collecting bin 9 according to the determined shape of the object.
The distinctive features of the described method for sorting objects by the
shape, particularly, sequential capturing the images of the shape of the
object
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as it passes the illuminating ¨ viewing zone and positioning the illuminators
and
the registered cameras on sphere, provide to reduce the percent of
unclassified
objects from their total quantity as a result of reducing the probability of
misclassifications. The sequential transmission of the captured images of the
object as the object is in the illuminating ¨ viewing zone provides to achieve
the
high performance and simultaneously keep the percent of unclassified objects
being less than (5 ¨ 10) % from their total quantity.
The examples of implementation of the method and the apparatus
The invention and the method may be implemented in the sorting
machines ASA-2 for sorting rough diamonds by the shape. Industrial PCs with
proprietary software applies as calculating means in these sorting machines.
This apparatuses are used for sorting the rough diamonds in the industrial
conditions. Testing of the apparatus for sorting by ten classes of the shape
of
the rough diamond of size (-6+1,5) mm showed the performance of ten crystals
per second. Furthermore the percent of unclassified crystals for re-sorting
was
less than 10% from the total quantity of the sorted crystals.
Industrial applicability
The method for sorting objects by the shape and the apparatus for its
implementation provides to achieve the high performance of sorting objects by
the shape classes, reduce the number of misclassifications and also can be
used for sorting (grading) the gemstones by their shape. Some of the above
mention sorting machines are used in the United Selling Organization (USO) of
ALROSA in Moscow (Russia).
