JP2005326220A - Foreign matter inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foreign matter inspection device of a simple structure realized at a low cost and easily maintained. <P>SOLUTION: This device is equipped with: an optical system (objective lens system) equipped with an infrared light source (straight-pipe infrared lamp) for uniformly illuminating the whole of a conveyor in its width direction by near-infrared light including specific wavelengths and a deflection mechanism (polygon mirror) for optically scanning an illuminated area on the conveyor by the near-infrared light in the width direction of the conveyor in order to partially view an illuminated area by the infrared-light; and a light detection element for detecting, via the optical system, the intensity of reflected light of the specific wavelength by raw material placed on the conveyor and/or by foreign matter getting mixed in the raw material. The optical system for guiding reflected light reflected from an inspecting object to the detection element is separated from an illumination system for illuminating the inspecting object by light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a simple and suitable for optically detecting foreign matter mixed in a raw material placed and conveyed on a conveyor, for example, same-colored foreign matter such as rubber mixed in tobacco engraving. The present invention relates to a foreign matter inspection apparatus having a structure.

  Foreign matter inspection devices used to inspect foreign materials in tobacco raw materials such as cigarettes, bones, and lamina, and to eliminate such foreign matter, exclusively detect foreign matter by focusing on the color of the inspection object. . Specifically, the color component of the color image obtained by imaging the inspection object is obtained, and the color component is a normal color component possessed by the inspection object, or there is a foreign substance that may be mixed into the inspection object. Foreign matter detection is performed by determining whether each is an abnormal color component (see, for example, Patent Document 1).

However, tobacco leaves (cigarette raw materials) are agricultural products, and have various color components depending on the variety, production area, production time, and the like. In addition, foreign materials mixed in tobacco materials usually include packaging materials and strings used for packing tobacco leaves. Among them, rubber and petroleum-based foreign materials that generate gas harmful to the human body are the same color components as tobacco materials. I often have. For this reason, it is difficult to reliably detect foreign matter from the color image described above. Therefore, it has been proposed that when the inspection object is irradiated with infrared rays, the foreign object inspection is performed by paying attention to the fact that the intensity of the specific wavelength in the reflected light differs depending on the tobacco raw material and the foreign object (for example, see Patent Document 2). .
JP 2000-3532 A Pamphlet of International Publication No. WO00 / 74504A1

  However, when an object to be inspected by irradiating an inspection object with infrared light of a specific wavelength and detecting the intensity of the reflected light, for example, when an inspection object is imaged using a camera, an expensive infrared camera or the like is required. Therefore, there is a problem that the configuration becomes large. In addition, when the infrared ray is irradiated while optically scanning the inspection object using a polygon mirror, and the reflected light from the inspection object is detected by tracing back the irradiation light path of the infrared ray, For example, since a laser beam with a sharp directivity is used or a large lens system for narrowing the light into a beam shape is required, the configuration of the entire apparatus cannot be denied. In addition, there is a problem that adjustment and maintenance for aligning the optical axes of the light irradiation system (light projection system) and the light receiving system via the polygon mirror become complicated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a foreign substance inspection apparatus that can be realized at a low cost with a simple configuration and that is easy to maintain.

The present invention relates to a conventional general foreign matter inspection apparatus that optically detects foreign matter mixed in a raw material that is placed on a conveyor and transported. It is focused on the fact that the maintenance complexity is mainly due to the configuration in which the reflected light is detected while optically scanning the light irradiated on the inspection object.
Therefore, the foreign matter inspection apparatus according to the present invention is intended to achieve the above-described object.
<a> An infrared light source that uniformly irradiates near infrared light including a specific wavelength over the entire width direction of the conveyor;
<b> An optical system that includes a deflection mechanism that optically scans the irradiation region of the near infrared light on the conveyor in the width direction of the conveyor, and locally views the irradiation region of the near infrared light;
<c> A light detection element for detecting the intensity of a specific wavelength of reflected light caused by a raw material placed on the conveyor and / or a foreign substance mixed in the raw material via the optical system. It is a feature.

That is, the foreign matter inspection apparatus according to the present invention uses an infrared light source that uniformly irradiates near infrared light including a specific wavelength over the entire width direction of the conveyor, such as a straight tube type infrared lamp, For example, it is not necessary to perform processing such as deflecting high-power laser light to optically scan, or narrowing the light irradiated to the inspection object into a beam,
On the other hand, an area in which the near-infrared light irradiation area on the conveyor is viewed locally on the conveyor via an optical system provided with a deflection mechanism is optically scanned in the width direction of the conveyor. The intensity of a specific wavelength of the reflected light caused by the raw material placed on the conveyor and / or the foreign matter mixed in the raw material is detected using a light detection element such as a photodiode through an optical system. It is characterized by that.

  Preferably, the optical system includes an objective lens system that is provided facing the conveyor and limits a viewing angle, and an imaging lens system that adjusts an image focus on the light detection element. Built. The deflection mechanism is a movable mirror that is inserted between the objective lens system and the imaging lens system and deflects the field of view of the light detection element formed by the objective lens system, for example, a polygon mirror that is rotationally driven. And realized as a galvanometer mirror.

  According to a third aspect of the present invention, the optical system is provided with a spectroscope that splits reflected light obtained by viewing the conveyor, and the light detection is performed in a plurality of optical paths dispersed by the spectroscope. It is also useful to provide each element so that the reflected light intensities of a plurality of different specific wavelengths are individually detected. In this case, the spectroscope is not only a device that simply branches the reflected light into a plurality of optical paths, but also has a function as a demultiplexer that demultiplexes the reflected light into a plurality of optical paths according to the wavelength. It may be.

  According to the foreign substance inspection apparatus having the above-described configuration, for example, an infrared light source such as a straight tube type infrared lamp is used to uniformly irradiate near infrared light including a specific wavelength over the entire width direction of the conveyor. Therefore, there is no need for a large-scale and complicated optical system for deflecting high-power laser light and optically scanning it, or narrowing light to be irradiated onto an inspection object into a beam shape. Then, the optical system is simply configured because the region to be locally viewed on the conveyor is optically scanned in the width direction of the conveyor via an optical system having a deflection mechanism such as a polygon mirror. it can. Furthermore, it is only necessary to detect the intensity of the reflected light from the above-mentioned region viewed locally, using a photodetection element such as a photodiode, so that inexpensive optical components (lenses, etc.) and electrical components (light The detection system of the reflected light can be easily configured using the detection element.

  In addition, as in the conventional foreign matter inspection apparatus having the above-described configuration, for example, an irradiation system (light projection system) for irradiating light to the inspection object and reflected light from the inspection object as a light detection element Therefore, it is not necessary to align the optical axis with the light receiving system for guiding to the light source, so that the adjustment and maintenance can be greatly facilitated.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings by taking, as an example, a foreign matter inspection apparatus that detects foreign matters such as paper pieces mixed in a cigarette (raw material).
FIG. 1 is a schematic diagram of a waist part of a foreign substance inspection apparatus according to this embodiment, and reference numeral 1 denotes a belt conveyor on which a tobacco stamp (not shown) as an inspection object is placed and conveyed. A straight tube type infrared lamp that irradiates near-infrared light including a specific wavelength, which will be described later, toward an inspection object (tobacco engraving) placed and transported on the belt conveyor 1 above the belt conveyor 1 (Infrared light source) 2 is provided. In particular, the straight tube type infrared lamp 2 is provided so as to cross the belt conveyor 1 in the width direction, and uniformly irradiates the near infrared light over the entire width direction of the belt conveyor 1. It has become. As a result, the inspection object (cigarette engraving) placed on the belt conveyor 1 is conveyed through the irradiation region of the near-infrared light from the infrared lamp 2 over the entire width of the belt conveyor 1. Yes.

  An optical filter (heat cut filter) 3 that transmits only near infrared rays is provided between the infrared lamp 2 and the belt conveyor 1, and the inspection object is detected by far infrared rays emitted from the infrared lamp 2. It has been devised so that the cigarette is not heated. Although not specifically shown, the infrared lamp 2 is provided with a cooling device, and heat generated by the infrared lamp 2 itself is suppressed by the cooling device so that the heat is applied to the inspection object (cigarette). There are no considerations.

  On the other hand, an objective lens system 10 is provided at an upper position of the belt conveyor 1 so as to face the irradiation region of the near infrared light, and further, the near lens on the belt conveyor 1 is interposed via the objective lens system 10. A polygon mirror (movable mirror) 11 is provided at a position for viewing the irradiation region of the infrared light. As the polygon mirror 11 rotates, the opposing angle of the plurality of mirrors formed on the outer peripheral surface of the polygon mirror 11 with respect to the belt conveyor 1 is sequentially changed, so that the light detection element 20 can be viewed through the imaging lens system 30 described later. It plays a role as a deflection mechanism for optically scanning a local area on the belt conveyor 1 in the width direction of the belt conveyor 1.

  In addition, the infrared lamp 2 mentioned above conveys the said belt conveyor 1 so that the visual field area of the objective lens system 10 may be illuminated from diagonally upward, for example so that the visual field of the belt conveyor 1 by the said objective lens system 10 may not be disturbed. The position is slightly shifted in the direction. As a result, the optical arrangement is set so that the objective lens system 10 can view the entire area in the width direction of the belt conveyor 1 in the near infrared irradiation region from the infrared lamp 2 on the belt conveyor 1. ing.

  In addition, the objective lens system 10 incorporates a correction lens system (not shown) for correcting a change in optical path length and the like associated with optical deflection scanning of the visual field region of the light detection element 20 by the polygon mirror 11. . For example, even when the deflection angular velocity by the polygon mirror 11 is constant, the correction lens system corrects the deflection scanning speed of the visual field region on the belt conveyor 1 to be constant. Further, the size of the field area of the light detection element 20 through the imaging lens system 30 on the belt conveyor 1 is kept constant by the correction lens system regardless of the deflection scanning of the field area by the polygon mirror 11, for example. It is.

  The light detection element 20 is composed of a photodiode (photoelectric conversion element) using a compound semiconductor such as GaAs or InGaAs, and an electric signal (voltage or current) corresponding to the intensity of light incident (received) on the light receiving surface. ) Is output from the so-called single function element. The imaging lens system 30 is provided so as to face the light receiving surface of the photodetecting element 20 so as to limit the viewing angle of the photodetecting element 20, for example, a beam shape incident along the optical center axis thereof. It plays a role of guiding only the light to the light detecting element 20.

  In particular, the imaging lens system 30 is determined such that the optical axis center thereof is always at a fixed position with respect to the polygon mirror (movable mirror) 11 described above. For example, the polygon mirror 11 is at a predetermined rotational angle position. At this time, the central position in the width direction of the belt conveyor 1 is set to be viewed locally through the reflecting surface of the polygon mirror 11. By rotating the polygon mirror 11 and changing the angle of the reflecting surface with respect to the optical axis center of the imaging lens system 30, the imaging lens system 30 can be viewed through the reflecting surface of the polygon mirror 11. Is deflected. As a result, the direction in which the imaging lens system 30 is viewed with the imaging lens system 30 being optically fixed, that is, the direction in which the light detection element 20 is viewed through the imaging lens system 30 is the belt. Deflection scanning is continuously performed in the width direction of the conveyor 1, particularly over the entire width direction.

  In this embodiment, three light detection elements 20 are provided, and three sets of imaging lens systems 30 corresponding to each of the three light detection elements 20 (20a, 20b, 20c). (30a, 30b, 30c) are provided. Then, the reflected light from the belt conveyor 1 received from the objective lens system 10 via the polygon mirror 11 is split (divided) into two optical paths via the first dichroic mirror 31 and split. The other reflected light is further split (demultiplexed) into two optical paths via the second dichroic mirror 32, so that it is split (demultiplexed) into a total of three optical paths. Then, the reflected light separated (demultiplexed) through the first and second dichroic mirrors 31 and 32 is converted into three photodetectors through the condenser lens system 30 (30a, 30b, and 30c), respectively. 20 (20a, 20b, 20c) is guided and received.

  In the example shown in FIG. 1, the reflected light guided from the polygon mirror 11 is guided to the first dichroic mirror 31 via the total reflection mirror 33, and the first and second dichroic mirrors 31, 32 are used for the spectroscopic analysis. The optical system is set so that the reflected light is guided to the photodetecting elements 20a and 20c through the (demultiplexed) total reflection mirrors 34 and 35, respectively. However, the optical system set by turning back the optical axis using the total reflection mirrors 33, 34, and 35 is the above-described photodetector 20 (20a, 20b, 20c) and imaging lens system 30 (30a, 30b, 30c). The arrangement (layout) is taken into consideration in order to reduce the size, and is not always necessary.

  In other words, in the optical system described above, the optical paths formed by the respective imaging lens systems 30 (30a, 30b, 30c), that is, the visual field regions of the respective light detection elements 20a, 20b, 20c, are divided into two dichroic mirrors 31, This is combined into a single optical path (viewing field region) whose optical axes coincide with each other through 32. Therefore, in any of the light detection elements 20a, 20b, and 20c, the same area on the belt conveyor 1 is locally viewed. The field of view is deflected and scanned over the entire width of the belt conveyor 1 by the rotation of the polygon mirror 11, so that the reflected light from the local field of view is reflected by each of the light detection elements 20a, 20b, 20c. Each receives light.

  Now, the three photodetectors 20a, 20b, and 20c provided as described above receive reflected light of specific wavelengths different from each other, for example, 800 nm, 1450 nm, and 1950 nm, as shown in FIG. Configured to detect its intensity. Such wavelength selectivity is given by, for example, the light transmission / reflection characteristics of the dichroic mirrors 31 and 32 described above, and further by the optical filters 21a, 21b, and 21c inserted in the respective optical paths.

  Incidentally, the characteristics shown in FIG. 2 are shown by comparing the difference in absorbance (index of reflected light amount) with respect to the wavelength of near-infrared rays of two kinds of raw materials and foreign matters mixed in the raw materials. From the characteristics shown in FIG. 2, the absorbance of foreign materials is higher than that of raw materials for near-infrared light in the 800 nm band, and compared to the absorbance of raw materials for near-infrared light in the 1450 nm band and 1950 nm band. It shows that there is a property that the extinction coefficient of the foreign matter is low. In order to inspect the foreign matter using the difference in the light absorbency (reflectance) between the raw material and the foreign matter with respect to the wavelength of the near infrared light, in this foreign matter inspection apparatus, the above-described three photodetectors 20a, 20b, The intensity of the reflected light at each of the specific wavelengths described above is detected using 20c, and foreign matter determination is performed based on the detection result.

  Specifically, in the signal processing unit 40 realized by a microprocessor or the like, the reflected light intensity at a specific wavelength in the reflected light is detected from the output of each of the light detection elements 20a, 20b, and 20c (intensity detection means). 41) The reflected light from the region on the belt conveyor 1 viewed locally by the light detection elements 20a, 20b, and 20c is due to the raw material by comparing the detection results with each other, or in the raw material It is determined whether it is due to foreign matter mixed in (foreign matter determination means 42). If it is determined that the reflected light is due to foreign matter, the position of the field of view that is optically deflected and scanned on the belt conveyor 1 according to the rotation angle of the polygon mirror 11, that is, the belt The position in the width direction of the conveyor 1 is specified (position detection means 43), and an exclusion command is issued to exclude foreign substances present at the position.

  The removal of foreign matter based on this command is performed, for example, by detecting the detection position with respect to the inspection object dispensed from the end of the belt conveyor 1 in synchronization with the conveyance of the inspection object (raw material and mixed foreign matter) by the belt conveyor 1. This is done by blowing the compressed air locally toward the part specified in (1), thereby removing foreign substances detected as described above and some raw materials existing around the foreign substance from the conveying path. Regarding the removal (blowing off) of foreign matters by blowing compressed air, for example, a plurality of compressed air blowing nozzles are arranged at a predetermined pitch along the width direction at the end of the belt conveyor 1, for example. The compressed air may be alternatively blown from the blowing nozzle according to the position information detected as described above.

  Thus, according to the foreign substance inspection apparatus configured as described above, the straight tube type infrared lamp 2 is used for the inspection object (the raw material and the foreign substance mixed in the raw material) carried on the belt conveyor 1. Since the near-infrared light is only uniformly irradiated over the entire width direction of the belt conveyor 1, the construction of the illumination light source is very simple. In particular, unlike the case of illuminating the belt conveyor 1 using laser light, the near-infrared light can be easily irradiated on the inspection object without using a large-scale apparatus or optical system. In addition, since the irradiation site (region) of near infrared light is not scanned, the configuration of the irradiation system can be greatly simplified.

  Incidentally, when the laser beam is deflected and scanned to irradiate the inspection target with the laser beam, the irradiation is performed, for example, at the central portion of the belt conveyor 1 and its both end edges due to the change in the optical path length accompanying the deflection scanning. Since there is a difference in the amount of light, it is necessary to correct this. However, according to the present apparatus, the irradiation light is not scanned, and as described above, the straight line type infrared lamp 1 is used to irradiate the belt conveyor 1 uniformly over the entire width direction. There are advantages such as non-uniformity in the amount of irradiation light.

  When detecting the reflected light from the inspection object irradiated with near-infrared light, it is only necessary to optically deflect and scan the local visual field region by the light detection element 20 in the width direction of the belt conveyor 1, The optical system can be simplified. In addition, as described above, there is no need to deflect and scan the near-infrared light irradiation area in conjunction with the deflection scanning of the visual field area. For example, the near-infrared light irradiation optical system and the reflected light detection optical system are conventionally used. Need not be realized as one optical system. In addition, it is not necessary to adjust the optical axes of the irradiation optical system and the reflected light detection optical system with high accuracy, and further, a device for separating the irradiation optical system and the reflected light detection optical system is also required. Absent.

  In other words, when the irradiation optical system and the reflected light detection optical system are combined to construct one optical system, for example, the optical path is set so that the light from the irradiation optical system does not enter the reflected light detection optical system. It is necessary to insert an optical element such as an optical circulator or a half mirror inside. However, according to the foreign object detection apparatus configured as described above, it is only necessary to configure an optical system for detecting reflected light independently of the near-infrared light irradiation system. And it can be built simply. In addition, effects such as adjustment and maintenance of the optical system can be achieved.

  The present invention is not limited to the embodiment described above. For example, the straight tube type infrared lamp 2 is provided on the upstream side and the downstream side of the belt conveyor 1 with the objective lens system 10 therebetween, and the field area of the light detection element 20 that is deflected and scanned via the polygon mirror 11. May be irradiated with near-infrared light from the upper positions on the upstream side and the downstream side of the belt conveyor 1, respectively. Further, for the objective lens system 10, if the optical system is set so that the size of the area on the belt conveyor 1 where the light detection element 20 views is reduced to about 1 mm in diameter, the detection resolution can be obtained. Can be increased sufficiently.

  Furthermore, if the infrared lamp 2 that emits only near-infrared light is used, the heat source cut filter 3 described above can be omitted. Further, the wavelength of the reflected light detected using the light detection element 20 may be determined according to the characteristics of the detection target, and the light detection element 20 having the detection characteristics corresponding to the wavelength is selected. A specific wavelength may be selected using an optical filter. Further, instead of the dichroic mirrors 31 and 32 described above, a half mirror may be used to split the reflected light from the inspection object. However, in this case, since it is unavoidable that the light amount is reduced due to spectroscopy, it is necessary to take measures such as correcting the amount of received light in the signal processing unit 40. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The principal part schematic block diagram of the foreign material inspection apparatus which concerns on one Embodiment of this invention. The figure which contrasts and shows the difference of the light absorbency with respect to the wavelength of the irradiation light of the raw material contained in a test target object and a foreign material.

Explanation of symbols

1 Belt conveyor 2 Straight tube type infrared lamp (infrared light source)
3 Heat source cut filter 10 Objective lens system 11 Polygon mirror (deflection mechanism)
DESCRIPTION OF SYMBOLS 20 Photodetector 21 Optical filter 30 Imaging lens system 31,32 Dichroic mirror 40 Signal processing part

Claims (3)

A foreign matter inspection apparatus for optically detecting foreign matter mixed in a raw material placed and conveyed on a conveyor;
An infrared light source that uniformly irradiates near-infrared light including a specific wavelength over the entire width direction of the conveyor;
An optical system that locally includes a deflection mechanism that optically scans the irradiation area of the near infrared light on the conveyor in the width direction of the conveyor; and
And a light detection element for detecting the intensity of a specific wavelength of the reflected light caused by the raw material placed on the conveyor and / or the foreign matter mixed in the raw material via the optical system. Foreign matter inspection device. The optical system is constructed to include an objective lens system that is provided opposite to the conveyor to limit a viewing angle and an imaging lens system that adjusts an image focus on the light detection element,
2. The foreign object according to claim 1, wherein the deflection mechanism includes a movable mirror that is interposed between the objective lens system and the imaging lens system and deflects the field of view of the light detection element formed by the objective lens system. Inspection device. The optical system includes a spectroscope that splits reflected light obtained by viewing the conveyor.
The foreign object inspection according to claim 1, wherein the light detection element is provided in each of a plurality of optical paths separated by the spectroscope and individually detects reflected light intensities having a plurality of different specific wavelengths. apparatus.

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