FR2459472A1 - APPARATUS FOR SCANNING MOVING OBJECTS BY ELECTROMAGNETIC RADIATION - Google Patents

Abstract

THE INVENTION RELATES TO A SCANNING APPARATUS RECEIVING ELECTROMAGNETIC RADIATION EMITTED OR REFLECTED BY MOBILE OBJECTS. ACCORDING TO THE INVENTION, THE RADIATIONS FROM A MOBILE OBJECT 11 ARE FOCUSED BY A LENS 17 AT THE LEVEL OF A FIXED OPENING 19, BUT A MOBILE ORGAN 22 HAS OPENINGS WHICH COME TO SWEEP THE FIXED OPENING 19 SO ALTHOUGH THE SENSOR PHOTOELECTRIC 28 RECEIVES LIGHT CORRESPONDING TO A SCAN OF THE OBJECT 11. APPLICATION TO AUTOMATIC ORE SORTING DEVICES.

Description

The present invention relates to scanning sets of an object

  mobile, intended to receive electromagnetic radiation emitted or reflected by such an object. It applies in particular but not exclusively to scanning sets of the type used in an automatic ore sorting machine. In an automatic ore sorting machine, all the rocks of a current must be

  characterized by the presence or ab-

  sence of a chosen property. The property chosen as a sorting criterion depends on the nature of the ore processed, but there are ores that can be sorted based on an assessment of the electromagnetic radiation emitted or reflected by the rocks.

  who are moving. For example, certain minerals

  Fluorescence luminescence when exposed to ultraviolet radiation, and these minerals can be detected when moving rocks

  are bathed in electromagnetic radiation, by

  layering of these irradiated rocks using a device

  which detects the light emitted by the fluorescent

  this minerals to select. Other minerals may

  can be detected from a color contrast, by

  reflection of visible light towards a set of

optical yage.

  In such an optical scanning assembly,

  used in an automatic sorting machine

  the light reflected or emitted by a moving rock is focused by an objective on a fixed aperture, and the light transmitted by this opening falls on a photoelectric device which

  forms electrical signals. The opening is in general

  It is an elongated slit, transverse to the direction of movement of the ore rocks, and long enough to define an observation zone wider than each rock passing through the scanning apparatus. When a rock

  passes in front of this device, the camera-

  electric forms electrical signals representing

  of light from a segment or

  transverse band of the surface of the rock, corres-

  laying at the observation area of the opening. Radiation may be due to a single source.

  placed in the observation area or at a

  a number of smaller sources, and the whole can not make a clear distinction between the intense sources and the continuous background. In addition, there is no indication of the precise location of the individual sources placed in the area.

observation.

  The invention relates to a scanning apparatus which allows a much better distinction between

  continuous background and the signals due to the sources to be detected.

  They also allow the more precise determination of

  positions of individual sources, and this characteristic

  As described in more detail below, this is particularly advantageous in the case of

  ore sorting apparatus in the form of

  any orientation in which the rocks

  successive stages do not necessarily follow

before the same journey.

  The invention thus relates to an apparatus for scanning a moving object, intended to receive electromagnetic radiation emitted or reflected by this object, this apparatus comprising a device comprising a lens and intended to receive radiation from the moving object and to to put them in the form of a beam, a detector intended to receive the radiation of the beam, a movable member intended to intercept the beam and comprising at least one opening which,

  during the displacement of the movable member, ensures a

  periodic cross-sectional drawing of the section of the

ceau, and

  a device for moving the movable member

bile at set speed.

  The apparatus may include a fixed member having an opening in the path of the beam, and the opening of the movable member may move in front of

  the opening of the fixed organ. In this case, the modern organ

  bile can be arranged to intercept the

  before the opening formed in the fixed member.

  The opening of the movable member may be part of a series of spaced apertures along the movable member, in the direction of displacement of

  this one, so that each opening sweeps periodically

the beam section.

  The movable member may be of rotary type, the openings being spaced circumferentially around its axis of rotation. More precisely, he

  may be a rotating disk and the openings may

  circumferentially separated by

  equal in the vicinity of the outer periphery.

  Alternatively, the movable member may be in the form of an elongated belt that moves rectilinearly across the beam and has longitudinally spaced apart openings. Specifically, the openings of the belt can

  be in the form of transverse slits.

  The radiation detector may comprise a photoelectric device intended to form

  electrical signals as a function of electrical radiation

  incident tromagnetic transmitted by the opening

of the mobile organ.

  A device can ensure the distribution of

  radiation transmitted by the opening to several

  ceaux having different wavelength ranges,

  and the photoelectric device may comprise in

  several photoelectric sensors arranged so that the separated beams reach each

  on one of the corresponding photoelectric sensors.

  Other features and benefits of

  the invention will emerge more clearly from the description which

  will follow, with reference to the accompanying drawings in which: - Figure 1 is a schematic section of a scanning apparatus according to the invention; FIG. 2 is a diagrammatic plan view of part of the scanning apparatus;

  FIG. 3 represents a part of an application

  sort of sorting an orientational ore stream

  any one, with a series of scanning devices

  ge of the type shown in Figures 1 and 2; FIG. 4 is a diagrammatic elevation of a part of a sorting apparatus of any orientation current, the apparatus comprising a series of scanning apparatus according to a variant of the invention; and - Figure 5 is a schematic section through

  the plane indicated by line 5-5 in Figure 4.

  Figure 1 shows a rock 11 of mine-

  rai, moving as indicated by the arrow,

  below an optical scanning apparatus with the general reference 12. In an exemplary machine for

  sorting of minerals, the rock is part of a

  of projected rocks in the form of a current

  coming from the end of a conveyor belt moving at high speed so that the rock is

  in free flight in front of the scanning device. Ha-

  usually, an additional apparatus identical to the apparatus 12 but returned, is placed under the path of the rocks so that it sweeps the underside of the

  rocks when the upper apparatus sweeps the surface

périeure.

  The scanning apparatus 12 bathes the superficial face

  the rock's rays of ultraviolet rays as well as mineral springs embedded in the rock

  exhibit luminescence due to fluorescence.

  The device sweeps the rock and detects the visible light.

  fluorescence, as well as reflected ultraviolet rays that can be used as an indication

the dimension of the rock.

  The scanning device 12 comprises a body 10 housing two lamps 13 with mercury vapor,

  equipped with reflectors 14, 15 for collimation and

  very transparent to ultraviolet rays and having a small bandwidth. These filters form two beams of ultraviolet rays that converge on

  rock and bathing the upper face of that

  This is caused by intense ultraviolet rays so that mineral sources present in the rock emit fluorescence.

  The body 10 is mounted at a first end.

  mite of a cylindrical column 20 provided with a lens 17 and a plate 18 fixed in the focal plane of the lens 17. The plate 18 has a main aperture 19 and a secondary aperture 21. As shown in FIG. the main fixed opening 19 is

  in the form of an elongated slot arranged diametrically

  relative to the fixed plate 18 and transverse

  the direction of movement of the rock. The or-

  fixed secondary 21 is in the form of a small

  rectangular hole distant from the main opening.

  Radiations reflected and emitted by the upper surface

  rock 11 can pass between the reflections

  14 mercury lamps so that they can

  on the lens 17 which focuses them in the form of an image at the aperture 19 of the fixed plate 18. Given the size reduction of the image due to the lens 18 and which may for example correspond to a ratio of 3/1, the opening 19 a

  sufficient field of vision to cover all

the width of the rock.

  In the known assemblies, the scanning is carried out simply by moving the rock in the field of view associated with a fixed aperture such as

  that the opening 19, the radiation transmitted by the

  lens on a single photoelectric sensor and forming electrical signals representative of the accumulation of visible light received over any

  the width of the field of vision. According to the invention, this

  during, scanning is more efficient because an organ is

  moving quickly to openings that sweep away

  the intersecting apertures delimit a much smaller field of vision which moves rapidly along the length of the slot 19 and therefore transversely with respect to

the rock.

  In the scanning apparatus shown, the

  gane mobile is in the form of a rotating disk 22 which

  in column 20 so that its peripheral margin

  that external cuts the beam of radiation, before the fixed opening 19. The disk is mounted on a pin

  23 which is rapidly rotated at a distance of

  speed regulated by an electric servomotor 24, the dis-

  that and the engine being housed in a housing 30 placed

on one side of column 20.

  As shown in Fig. 2, the disk 22 has a series of eight scan slots in the form of radial slots formed in the outer peripheral margin of the disk with constant circumferential spacing. When the disc 22 rotates, the openings successively scan the fixed opening 19 of a

  end of it to the other. When each

  ture scans the fixed aperture 19, it defines, with this latter opening, a reduced field of vision that moves quickly from one end of the slot 19 to

  the other. During, the short time interval required

  for the mobile opening to sweep the opening

  stationary from one end to the other, the rock has advanced a short distance so that it is swept over a segment of its surface which is not perpendicular to the direction of movement of the rock but which is

  slightly inclined relative to this direction. Lors-

  that the number of sweep openings and the speed

  If the rotational segments of the disk are suitably selected, the successive segments swept on the surface of the rock during the sweeps of the successive openings 25 may be contiguous in the direction of movement of the rock or may even overlap slightly so that the the entire surface of the rock is

swept.

  The electromagnetic radiation transmitted through the apertures 19 falls on a plate 26 which is placed obliquely in the column 20 and which reflects the ultraviolet rays but which transmits practically the visible light. Visible light transmitted by the

  plate 26 passes through a plate 27 of a filter which

  retorts the residual ultraviolet rays and arrives at a photoelectric sensor 28 which creates electrical signals representative of the amount of visible light received in the field of view delimited by

  the intersection of the fixed aperture 19 and the opening

  corresponding sweep. A field lens 40 may be mounted in the column 20 so that it allows the remote arrangement of the sensor

  photoelectricity and the optimal use of

  photosensitive face of this sensor and that the dark current of the sensor is reduced. The position and

  the focal length of the field lens are chosen

  so that the image and dimension are appropriate for

  the detector. The field lens can be advantageously

  a convergent Fresnel lens because it

  it is not essential that it gives a particular image

sharply clean.

  The ultraviolet rays reflected by the

  plate 26 reach a second photoelectric sensor

  29 which creates electrical signals representing

  of the amount of ultraviolet rays

of the field of vision.

  The photoelectric sensors 28 and 29 can

  be connected to a suitable electronic circuit

  to transmit sequences of signals

  During the course of time, the signals from the sensor 28 indicate the presence and location of fluorescent sources in the rock while the sensor signals 29 indicate the extent of the surface of the rock. The number of important sources per unit

  of rock surface can thus be evaluated immediately

is lying.

  The use of the rotating disc 22 also allows

  if using a continuous calibration device

  of the photoelectric sensor 28, with respect to

  standard color reference standards. This provision

  tif may comprise two bundles 31 of optical fibers

  from the collimation reflectors

  and reach the rotating disk. A first

  mite 32 of each beam protrudes from the reflector 15 and cooperates with a fluorescent material giving a reference color, for example a reference of

  White. The other ends 33 of the

  are collected and presented on the rotating disk

  just opposite the fixed secondary opening 21

formed in the plate 18.

  The disc 22 has a series of eight small openings 34 arranged so that they pass successively between the ends 33 of the bundles

  fiber and the secondary opening 21. Each opening

  Figure 34 is associated with a scan aperture.

  More specifically, the openings 34 are disposed inwardly relative to the openings 25, and the secondary opening 21 of the plate 18 is arranged so that each opening 34 passes in front of

  the fixed aperture 21 just before the opening cor-

  Sweeping responder reaches the main fixed aperture 19, taking into account the direction of rotation of the disk. Thus, just before each scan, the photoelectric sensor 28 receives a color reference beam from the fiber optic bundles and

fixed secondary opening 21.

  Since the scanning apparatus shown in FIGS. 1 and 2 gives precise indications of the position of the detected sources as well as the position of the rocks, a series of such devices can be used for scanning a stream of rocks. any orientation. FIG. 3 corresponds to this characteristic and schematically represents a line of apparatus 112 for scanning a stream of rocks 111 of an ore, having any orientation. The positions of the fixed openings 119

  in the form of slits are indicated in broken lines.

  Given the optical magnification of the devices, the slots have overlapping fields of view and form a continuous line of sweeping across the entire

width of the stream of rocks.

  In a variant, the rotary disk 22 can

  replaced by a belt with trans-

  versales and moving rectilinearly

  the beam of radiation. Figures 4 and 5 represent

  feel this embodiment, comprising a series of apparatus 212 for scanning a stream of ore rocks of any orientation, on a conveyor belt 210. The fixed apertures of the scanning apparatus are identified by the reference 219 and the secondary fixed openings by the reference 221. An endless belt 222 has transverse scanning slots 225 and secondary openings 234. The belt is carried by pulleys 240 of which at least one is conducted so that the belt travels at high speed in the beams of radiation of

  all scanners and slots 225 ba

  the fixed openings 219, the openings se-

  at appropriate moments in front of the fixed secondary openings 221. This provision

  removes the problem of synchronizing

  tesses of several separate scanning disks.

  The apparatus shown has only been described for illustrative purposes and allows variations

  important. For example, in many applications

  cations, a measure of the surface of the rocks is

  superfluous and, in this case, the second photo-

  electric 29 can be eliminated, a single sensor 28

  measuring visible light formed by fluorescence.

  In an embodiment comprising two

  scanning devices, placed one above the other

  a single belt similar to that

  shown in Figures 4 and 5 can form a vertical loop so that it passes over the opening

  of the upper apparatus in a higher

  top of the loop, and on the fixed opening of the lower unit, at a lower part of the loop. It should be noted that, in the embodiment of FIGS. 1 and 2, the cross section of the scanning aperture formed by the intersection of the aperture

  mobile and fixed opening varies when the opening

  The mobile track progresses from one end of the fixed aperture to the other due to the varying inclination of the movable slot relative to the fixed slot. In most applications, this feature

  does not matter but, where appropriate, a correction

  the appropriate time can be made by variation of

  the width of the opening fixes over its length.

  In an important variant, the fixed plate 18 is completely removed and the sweeping is simply ensured by the displacement of the openings

  scanning the movable member. In this case, the

  scanning vertices can be reduced to holes

  rectangular or relatively small squares, replacing

  with long slits. This arrangement ensures a sweeping of a curved path so that the rocks are

  scanned following a series of festoons.

  Scanning openings can also

  be used for the transmission of normal

  - colored reference markers, instead of opening

  separate secondary courses. This characteristic

  puts genuine standardization and compensation of

  small differences between the dimensions of the openings

res and other parameters.

  It is understood that the invention has not been

  described and shown only as a preferred example

  and we can provide any technical equivalence

  in its constituent elements without

get out of his frame.

Claims (10)

  1. Apparatus for scanning a mobile object transmitting   or reflecting electromagnetic radiation, said apparatus being of the type which comprises a lens device for receiving radiation from the moving object and forming it in the form of a beam, and a detector for receiving beam radiation, said apparatus being characterized in that it comprises a movable member (22) for intercepting the beam   and having at least one opening (25) which, when   placement of the movable member periodically scans the section of the beam in the transverse direction, and a device (24) for moving the movable member at set speed.   2. Apparatus according to claim 1, of the type which comprises a fixed member having a placed opening   on the path of the beam, said apparatus being   characterized in that the opening (25) of the movable member   sweeps the opening (19) of the fixed member (18).   3. Apparatus according to claim 2, characterized   in that the movable member (22) is disposed of   that it intercepts the beam before it   come to the opening (19) of the fixed member (18).   4. Apparatus according to any one of the   1 to 3, characterized in that the opening (25)   of the mobile organ is part of a series of   spaced along the movable member (22) in the   direction of movement of the latter so that each   one of the openings periodically sweeps the section beam.   5. Apparatus according to claim 4, characterized   in that the movable member is a rotary member   (22) having circumferentially spaced apertures (25)   around its axis of rotation.   6. Apparatus according to claim 4, characterized   that the mobile organ is in the form of a cour-   elongated web (222) moving transversely to the beam in a rectilinear motion and having   openings (225) spaced longitudinally.   Apparatus according to claim 6, characterized   in that the openings (225) formed in the belt are in the form of transverse slots.   8. Apparatus according to any one of the   1 to 7, characterized in that the radiation detector comprises a photoelectric device   (28) for creating electrical signals in   incident electromagnetic radiation,   transmitted by the opening of the movable member.   9. Apparatus according to claim 8, characterized   in that it further comprises a device (26)   intended to separate the radiation transmitted by the   plurality of beams (19) having different wavelength ranges, and the device   photoelectric sensor comprises a number of photo   electric (28, 29) equal to the number of beams,   arranged so that the separated beams arrive   each on a separate photoelectric sensor.   Apparatus according to claim 8, characterized   characterized in that it comprises a device (13) for illuminating a moving object to be scanned, and a calibration device for transmitting   normalized color radiation to the photo-   electrical device (28) so that it is calibrated, the calibrating device including at least one optical fiber light guide (31) having one end   exposed to the light of the illuminating device (13)   and is lined with a material which, when   receives this light, forms a beam of a color   reference transmitted along the light guide, the   the end of the latter being arranged in such a way that it transmits the reference color beam to the photoelectric device (28) along a path which is intercepted by the movable member (22) whose movement causes the periodic exposure of the device   photoelectric at the reference color beam.