Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
  • B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
  • B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
  • B07C5/34—Sorting according to other particular properties
  • B07C5/342—Sorting according to other particular properties according to optical properties, e.g. colour

Definitions

• the invention relates to a device for optically checking and sorting objects, in particular foodstuffs, which are guided serially in free fall through a test zone, around which a plurality of light sources and at least one reflected light receiver are circumferentially arranged, the light signals of which are opto-electrically converted in a control device Predetermined limit values are compared, if they are exceeded or undershot, a control signal is generated in a microprocessor, which acts on a sorting switch, which is arranged below the test zone.
• Such a device is known from DE 36 14 400 Cl, in which in particular agricultural products such as peas, beans or the like are occasionally bypassed an optical test device, the product error detection signal of which controls a downstream product switch, whereby defective objects are driven.
• the optical test device the isolated objects are illuminated by light sources distributed around the circumference of the transport path. The light reflected from the test objects is picked up by assigned light receivers and converted electrically with regard to impermissible signal folc ; i evaluated.
• the incandescent lamps used for lighting provide global lighting for the objects and the light receivers likewise capture the object as a whole with respect to a background adapted to the average object, so that the received signals only provide a global statement about the optical properties of a product, which is only sufficient for a rough assessment, for example a degree of maturity.
• this device does not display an approximately punctiform damaged area, for example a worming sting, a mold patch, etc., which means that its area of use is very limited.
• the device is only suitable for the optical assessment of dry objects, since moist surfaces, depending on their angular position to the light source and the light receiver, supply strongly fluctuating signals due to the different reflections.
• an optical inspection and sorting device is known from the brochure of Key Technology Inc., USA, Opti Sort, 8/89, in which the individual objects are each inclined from above with several electronic cameras with electro-optical line converters, so-called CCD Arrays, scanned at high speed and whose signals are evaluated with respect to predetermined limit values.
• CCD Arrays electro-optical line converters
• the camera devices and the evaluation electronics are very complex and expensive.
• DE 30 222 750 AI discloses an optical scanning device for illuminated objects carried on a band, a bundle of the radiation reflected from the object being guided via a focusing and scanning optical-mechanical arrangement to a plurality of reflected light receivers which are sensitive to different light wavelengths is.
• part of the reflected light is taken up by optical fibers, one end of which is arranged around the evaluated light beam and coated with a reference fluorescent paint, and the other ends of which are guided to a reference photocell, the signal of which serves as a color reference signal for evaluating the signals of the other light receivers.
• This device is only suitable for scanning an object side and requires a high mechanical and optical effort as well as several photo sensors; nevertheless, only the reflected light from one direction is detected.
• the light sources are each formed by a laser scanner, the deflection planes of which are essentially perpendicular to an object drop direction, and these laser light sources cyclically sequentially detect an object circumferential sector for approximately one deflection period
• the light receivers are optical fibers Are fiber optic bundles, the ends of which are fed to an opto-electric reflected light converter, the output signal, the reflected light signal, of which is fed to the control device for comparison with the limit values and a further evaluation, and that a direct light receiver is arranged on all sides around the test zone at such a height, that the laser scanner beams always hit it when they do not hit an object, and that this direct light receiver leads to an opto-electrical direct light converter whose direct light signal is fed to the control device.
• the light receiver device which consists of a large number of light guide ends oriented at different angles to the object surface and to the laser beams and which bundle the received light to an electro-optical converter, permits the evaluation of dry and moist-glossy surfaces, since the so caused averaging of the reflected light over many radiation directions eliminates disturbing gloss effects.
• the assessment of objects of different sizes is facilitated by the fact that the control of the signal evaluation takes place in such a way that direct laser light, which occurs on the opposite side of the laser when the object is not present, is detected with separate light receiver means and the evaluation of the reflected light with respect to the evaluation time and the evaluation threshold is controlled as a function of the signals of the light detected in this way.
• the opto-electrical converters each consist of one photodiode, so that a very simple serial signal evaluation of the two photodiode signals is possible.
• the high speed of modern electronic means enables the lasers, each of which encompasses an angular segment area of the object circumferentially, to be activated cyclically one after the other, so that overlap of reflected light from different laser beams does not occur during the evaluation and only a single evaluation electronics channel for the successively occurring line segment signals which the individual lasers generate one after the other is required.
• the evaluation of the reflected light of a test object is carried out by multiple analysis of the signal sequences obtained, which can be assigned to an object.
• the following parameters are to be specified in each case according to the conditions:
• a defect on the object results in a signal outside the permissible brightness limit values during the line scan, that is, a defect signal.
• Fig. 1 shows a potato peeling system with a testing and sorting system in the circuit
• Fig. 2 shows the testing and sorting device, partially opened
• Fig. 3 shows a section of the test device
• Fig. 4 shows an enlargement of a cross section of an optical fiber for direct light detection with a beam path scheme
• Fig. 5 shows a cross section of a light guide tape, • 'enlarged
• FIG. 7 shows a block diagram of the signal evaluation device.
• Figure 2 shows the testing and sorting device (2) partially opened and cut.
• a flat, ring-shaped housing (6, 61, 62) is arranged around the test zone (PZ), on the outer ring wall (6) of which a plurality of laser scanners (4) are arranged, equally distributed over the circumference, the alternating laser beams (Eil, E12 , E2, E3) enter the ring interior through narrow slits (40) and cover the central area in the test zone (PZ) in a fan-like manner, sweep horizontally so that the test specimens (B) are scanned on all sides.
• the end faces (3) of light guides are arranged radially all around on the ring wall (6).
• the light guides are guided to the outside and run together to form a photo bundle (30) in an evaluation and control device (ST).
• a light guide flat band (9) is arranged all around along the ring wall (6), which is arranged so that the Laser light bundle (Eil, E12, E2, E3) falls directly on it when there is no test object (B) in the beam path, i.e. when there is no test object in the test zone (PZ) or the laser beam is just so far laterally deflected that he runs past the test object just present, as is always the case with the laser beam (Eil, E12), which is deflected to the edge of the fan.
• the flat ribbon light guide (9) is also combined at the end to form a light guide bundle (90) and fed to the control device (ST).
• the control device (ST) in turn controls the laser scanners (4) cyclically and it controls the valves (50) of the blowing nozzles (5) fed with compressed air (P).
• FIG 3 shows an enlarged section of the test device, partially opened.
• the Lasersca ⁇ ner (4) consists of a laser diode (7), the laser beam (El), deflected by an electromagnetically controlled periodically pivoted mirror (8), enters the annular space through a horizontal slot (40) in the ring wall (6).
• the annular space is largely closed by a base plate (62) and a cover plate (61), and there are only openings in it for the serial passage of the test objects.
• the ring wall (6) has internal steps (63, 64) on the front, in which the top and bottom plates (61, 62) are held centered.
• the ring wall (6) has a circumferential groove on the outside
• the light guide strip (9) is arranged all round above the light guide ends (3).
• the light guides of the band (9) are arranged so close to one another and have such a small diameter that the laser beam always hits at least one light guide of the band (9) when it does not hit a test object.
• Figure 4 shows the schematic beam path in an optical fiber (91) of the optical fiber ribbon.
• the laser beam (E) penetrates the optical fiber (91) from the side and is focused by its cylindrical lens effect.
• the focus (F) is on the other side of the fiber (91) on the ring wall (6).
• this is roughened by a bevel (S), so that light incident there from inside is scattered there as scattered light (ES) and light coming back from the reflecting ring wall (6) as scattered light (ES ) is distributed in the optical fiber (91).
• Figure 5 shows a section of the light guide tape (9), enlarged, in cross section with the schematic useful beam profiles of the laser beam (E).
• the individual optical fibers (91, 92, 93, 94) are through narrow retaining webs . (95) connected to each other and thus held at a defined short distance from each other.
• Figure 6 shows a plan view of the light guide tape (9), enlarged, with the useful beam path.
• the incident Laser light (E) and the light reflected from the ring wall (6) is partly scattered as flat by the cut (S) of the fiber as scattered light (SL) into the
• Fiber released that the angle of the total reflection on the fiber wall is undershot and light is guided to the ends of the light guide (91), where the light arriving there is evaluated.
• FIG. 7 shows the control device (ST) in a block diagram.
• This consists of a program-controlled microprocessor (MP), which controls electrical circuits via an address bus (AB) and supplies the respective controlled circuit with data or receives data from it via a data bus (DB).
• MP program-controlled microprocessor
• the circuits external to the microprocessor (MP) are to be provided at the processing speeds which are customary today in order to achieve a sufficient processing speed which can be achieved with a thorough inspection of freely falling objects (B). If faster microprocessors (MP) are available at affordable prices, the functions of the external circuits can also be carried out in whole or in part directly in such processors.
• the timing of the function sequence in the control device (ST) is carried out by an electronic clock generator (CD. This controls a time counter (CT), the upper digits of which control the four lasers (L1-L4) one after the other via a decoder (DI).
• CD electronic clock generator
• CT time counter
• DI decoder
• the direct laser light is picked up by the light guide band (9) and by the light guide bundle (90) emanating therefrom onto a direct light receiver (DL) conducted and there converted opto-electrically and amplified in a first amplifier (VI).
• the direct light signal (DL) obtained in this way is evaluated in a first threshold value comparator (S1), which emits gap signals (L1, L2) when the direct light is absent, which signals the presence of an object (B) in the laser beam path.
• reflected light is generated, which is collected via the light guide bundle (30) and fed to the reflected light receiver (RL), whose opto-electrically converted signal is amplified in a second amplifier (V2) and then to one second threshold comparator (S2) is compared with a predetermined upper and a lower threshold (SO, SU).
• These respective threshold values (SO, SU) to be specified are successively given by the microprocessor (MP) via the data bus (DB) to a digital-to-analog converter, the analog output signals of which are stored in two holding circuits (HI, H2), and from there the second threshold comparator
• the output signal of the second comparator (S2) is a defect signal (SF) which indicates that the permissible brightness range between the predetermined limit values (SO, SU) is under or exceeded.
• a counting process is released in a counter (CT1), the counter content (Z) of which is therefore a measure of the size of the defects.
• the counter content (Z) is controlled by the microprocessor (MP) and compared via a computer unit (ALU) with predetermined comparison values stored in a register block (R1). If the limit value is exceeded the microprocessor (MP) gives control signals to the switch controller (50).
• this circuit arrangement can also be carried out with presettable counters instead of with a computer unit (ALU) and a register block (Rl), which are loaded with the upper limit values in some cases and which, after counting down during the fault signal at a zero crossing, are activated by the microprocessor (MP) deliver interrogable signal.
• ALU computer unit
• Rl register block
• the direct light detection and the scattered light detection can also be carried out in each case with similar optical fiber devices, in particular with an optical fiber tape. Since the direct light produces a higher light yield at the receiver than the scattered light, the gap signal can also compensate Receiver signal such as the defect signal can be obtained by the receiver signal is fed to a further threshold switch with a high threshold voltage. As a result, only an optical fiber ribbon and an opto-electrical converter are required.
• the entire scope of the object can be scanned with a reduced number of laser scanners if a mirror is arranged in a partial area of the scanner deflection which lies next to the test zone and directs the laser beam onto another peripheral segment of the object.
• Deflecting mirrors can also be arranged on both sides of the test zone, so that the object is scanned in a fan-like manner from three different basic directions during a scanner deflection cycle.
• the scanner deflection mirrors are preferably controlled with linearly rising and falling currents in galvanometer coils, so that there is an approximately linear relationship between the duration of a defect signal and the extent of a defect. Accordingly, the counting of the time pulses during the duration of a defect signal yields a count result that corresponds directly to the defect size. If a linear deflection is chosen instead of a sinusoidal one, it is advisable to limit the linearity error so far that only the middle, somewhat linear, area cuts through the test zone.
• the deflection speed is expediently chosen so that an all-round object scanning, that is, the entire cyclical sequence of all laser scans takes place at a time in which the test object has traveled the falling distance in the test zone by a load beam thickness.
• the scanning strips adjoin one another.
• they can also be switched at the clock frequency, so that a punctiform scanning takes place all around, the points of a laser being spatially adjacent to one another if the deflection path corresponds approximately to the laser beam diameter during a laser follow-up cycle.
• This type of laser control requires a slower beam deflection frequency, which increases the life of the scanner.
• the fault location signals are then evaluated in the time-division multiplex in the counters assigned to the individual lasers. The counter contents obtained in this way are then evaluated in the manner described above.
• the device can also be easily configured in a professional manner in such a way that rolling objects are optically completely scanned by arranging at least two laser arrangements one behind the other in the direction of movement of the objects, offset by about half the object circumference.
• the light receivers or at least the optoelectrical transducers are advantageously used in common for both arrangements, which is why all the lasers are controlled in succession and the light guides are brought together.
• the scanning arrangements and the light detections enclose only a partial circle of a little over 180 °.

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• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)

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• 1991
  • 1991-12-09 DE DE19914140513 patent/DE4140513C1/de not_active Expired - Fee Related
• 1992
  • 1992-12-05 EP EP19920924671 patent/EP0570558A1/de not_active Withdrawn
  • 1992-12-05 AU AU30853/92A patent/AU3085392A/en not_active Abandoned
  • 1992-12-05 WO PCT/EP1992/002812 patent/WO1993011882A1/de not_active Application Discontinuation

Non-Patent Citations (1)

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