Image capturing unit and inspection system

An image capturing unit in an inspection system for performing an inspection target appearance inspection, the image capturing unit comprising, an image capture unit, an illumination unit arranged in a periphery of the image capture unit, and a protective unit covering the image capture unit and the illumination unit, wherein the protective unit includes a plate-like member configured by a first planar portion and a second planar portion being connected through a bent portion bent in a dog leg shape, and the image capture unit is located on a back side of the first planar portion.

BACKGROUND OF THE INVENTION

Technical Field

The invention relates to an image capturing unit in an inspection target appearance inspection system, and an inspection system.

Background Art

There are inspection systems that capture images of the appearance of inspection targets while causing the inspection targets to fall, and, from the captured images, determine and sort unsuitable inspection targets (refer to Japanese Patent No. 4915129).

Image capturing conditions affect determination accuracy in inspection systems.

SUMMARY OF INVENTION

Accordingly, an image capturing unit having a configuration that makes it possible to further improve determination accuracy and an inspection system using the image capturing unit is provided.

One aspect of embodiments relates to an image capturing unit in an inspection system for performing an inspection target appearance inspection, the image capturing unit comprising: an image capture unit; an illumination unit arranged in a periphery of the image capture unit; and a protective unit covering the image capture unit and the illumination unit, wherein the protective unit includes a plate-like member configured by a first planar portion and a second planar portion being connected through a bent portion bent in a dog leg shape, and the image capture unit is located on a back side of the first planar portion.

Another aspect of embodiments relates to an inspection system for performing inspection target appearance inspection, the system comprising: a first image capturing unit described above; a second image capturing unit described above; and a processing apparatus that controls operation of the first image capturing unit and the second image capturing unit, and determines an inspection target to be sorted out from among inspection targets based on images captured by the first image capturing unit and the second image capturing unit, wherein the first image capturing unit and the second image capturing unit are arranged to face each other through a region through which the inspection target passes, at an orientation in which the first planar portion of the first image capturing unit and the first planar portion of the second image capturing unit are respectively arranged on a top side.

DESCRIPTION OF THE EMBODIMENTS

First, with reference toFIG.1, an external configuration of the inspection system10for performing an inspection target appearance inspection will be described.FIG.1is a view illustrating an example of the external configuration of the inspection system10corresponding to the embodiment. Referring toFIG.1, the inspection system10may be configured to include image capturing units101A and101B, a belt conveyor102, a discharge unit103, or the like or the like. Inspection targets in the present embodiment include grains such as rice and barley, other grains, granules such as seeds or raw materials for processing, as well as industrial products such as tablets, screws, nuts, buttons, rubber products, and also food products such as vegetables, meats, fried or frozen foods, or the like.

In the present embodiment, in accordance with control by an external information processing apparatus (the information processing apparatus206illustrated inFIG.2A), while the inspection target conveyed by the belt conveyor102falls between the image capturing units101A and101B, the image capturing units101A and101B capture images of the appearance of the inspection target. The captured images are provided to the information processing apparatus206, the discharge unit103is caused to operate in a case where an inspection target determined to be unsuitable, such as when a shape or color does not meet a certain standard, is discovered, to discharge air and sort out the inspection target determined to be unsuitable.

FIG.2Ais a block diagram illustrating an example of a functional configuration of the inspection system10corresponding to the embodiment. In the inspection system10as illustrated inFIG.2A, the information processing apparatus206controls the operation of an image capture unit201, an illumination unit202, a discharge unit203, a conveyance unit204, and a target object supply unit205.

The image capture unit201is configured to include a two-dimensional area sensor, an AD converter or the like, and it is possible to use an image capturing element such as a CCD or a CMOS therefor. By using a two-dimensional area sensor, as compared with a line sensor which has been widely used in conventional sorting apparatuses, the angle of view is wider, and also by capturing an image of the inspection target a plurality of times, it is possible to substantially increase the inspectable area.

The number of pixels of the area sensor may be several million pixels as an example, but is not limited thereto. The number of pixels depends on the size of the inspection target and the criteria to be discriminated by inspection. For example, as long as the size of external features of the inspection target for determining whether criteria are met is equal to or greater than a certain amount, VGA image quality or the like need only be ensured; on the other hand, when it is necessary to determine detailed features, it is possible to use an image capturing element that is of a high resolution such as4K. The image capture unit201may include a hood arranged on a light receiving surface side of the image capturing element so that light from the outside does not enter the image capturing element.

The image capture unit201can perform image capturing at a frame rate of from 20 to 35 frames per second by the control of the information processing apparatus206. The frame rates indicated here are examples and a higher frame rate is possible. In the present embodiment, the image capturing is described illustratively as being performed at 30 frames per second.

The illumination unit202is arranged in the periphery of the image capture unit201so as to surround the image capture unit201, and includes a plurality of LEDs arranged in a matrix. As an arrangement pattern of the illumination unit202, arrangement at the top, bottom, left, and right of the image capture unit201can be considered. Further, the illumination unit202may be arranged only on the top and bottom, and it may be arranged only on the left and right. Alternatively, the illumination unit202may be arranged only in whichever of the top and the bottom has better light directivity, or may be arranged only in whichever of the left and the right has better light directivity. The illumination unit202irradiates light onto the inspection target at the time of image capturing by the image capture unit201.

The image capturing units101A and101B are configured to include a camera unit combining the image capture unit201and the illumination unit202; there may be a plurality of camera units arranged in each of the image capturing units101A and101B.

The discharge unit203corresponds to the discharge unit103and is a mechanism for discharging air; for example, the discharge unit203is configured as a mechanism for blowing air by releasing compressed air by an electromagnetic valve, a flap drive mechanism, or a fan including a fan and a motor. By operating the discharge unit203, it is possible to send out the air within the space in which the inspection target is dropped. The operation of the discharge unit203is controlled by the information processing apparatus206, and when an inspection target whose image is captured by the image capture unit201is determined to be unsuitable, the discharge unit203may be operated to sort out the inspection target.

The conveyance unit204corresponds to the belt conveyor102, conveys the inspection target, and supplies the inspection target into the inspection space where the image capturing units101A and101B perform image capturing. A mechanism for conveying an inspected target object may also be included. The target object supply unit205is a mechanism for discharging the inspection target from a holding portion in which the inspection target is held to supply it to the conveyance unit204. Operation of the conveyance unit204and the target object supply unit205is controlled by the information processing apparatus206. Operation of the conveyance unit204and the target object supply unit205may be controlled by a control apparatus other than the information processing apparatus206. In such a case, the information processing apparatus206can cooperate with the control apparatus.

The information processing apparatus206is an apparatus for controlling operation of the image capture unit201, the illumination unit202, the discharge unit203, the conveyance unit204, and the target object supply unit205, and, for example, is configured in a personal computer or the like. In the information processing apparatus206, by processing images acquired from the image capture unit201, it is determined whether an inspection target which is the target of image capturing meets certain criteria, and when it is determined that the criteria are not met, the air is sent out by controlling the discharge unit203to operate the fan, for example, to thereby sort out the unsuitable inspection target.

Next, with reference toFIG.2B, an example of a hardware configuration of the information processing apparatus206will be described. InFIG.2B, a processor261executes an OS and various application programs or the like, which are stored in a hard disk (HD)263, the application programs being for controlling the operations of the image capture unit201, the illumination unit202, the discharge unit203, the conveyance unit204, and the target object supply unit205, and performs control for temporarily storing in the RAM262information, files, or the like necessary for executing the programs. The processor261includes a CPU, a GPU, an FPGA, an ASIC or the like. The RAM262functions as a main memory, a work area, or the like of the processor261. The HD263stores application programs, driver programs, an OS, control programs, and processing programs for executing processing corresponding to the present embodiment.

A display264is a display means for displaying a command inputted from an operation unit269or information or the like acquired from the outside. An interface (hereinafter, referred to as an I/F)265is a communication interface for connecting to an external device such as the image capturing unit101or a network. A ROM266stores programs such as a basic I/O program. An external storage drive267may load programs or the like stored in media268into a computer system. The media268is a recording medium and stores predetermined programs and associated data. The operation unit269is a user interface for allowing an operator of the apparatus to input an instruction, and is composed of a keyboard and a mouse. A system bus270controls the flow of data within the device.

Referring now toFIGS.3A and3B, an external configuration of the image capturing units101A and101B (hereinafter, simply referred to as the image capturing unit101) will be described.

FIG.3Ais a view illustrating an example of an external configuration of a windshield301of the image capturing unit101when viewed from the front side. InFIG.3A, the windshield (cover)301is attached to the image capturing unit101so that dust or the like does not enter the camera lens. The windshield301is attached to a frame302, and has a configuration where it is bent in a dog leg shape at the bent portion indicated by reference numeral301a. The windshield301and the frame302constitute a protective unit that covers and protects the image capturing unit101from dust. The windshield301is a colorless transparent acrylic and has a configuration that does not block light from entering the image capture unit201or block light emitted from the illumination unit202. Note that the windshield301may be made of resin such as glass or polycarbonate rather than acrylic. The frame302on the other hand is a structure made of, for example, metal or plastic and does not transmit light. On the back side of the windshield301, camera units310and320which are combinations of the image capture unit201and the illumination unit202are arranged.

The camera units310and320are basically of a common structure, and the components illustrated by the reference numerals31X and32X in the following explanation are common components. Thus, the description with reference to31X applies similarly to32X. Further, the same number of camera units310and320are arranged in the image capturing units101A and101B, respectively; in the case of distinguishing the image capturing unit in the description, a capital letter symbol A or B will be added as a suffix. Components to which an A symbol is added are components of the image capturing unit101A, and components to which a B symbol is added are components of the image capturing unit101B. The difference in the symbol is only to which image capturing unit the component belongs to, and the basic configuration is the same, as indicated by31X and32X.

FIG.3Billustrates a state in which the windshield301inFIG.3Ahas been removed and illustrates an example of a configuration of the camera units310and320. The LED illumination units311,313,314, and315are arranged in the camera unit310; the region where the image capturing element (not illustrated) is arranged is surrounded by the respective LED illumination units; and a hood312is arranged above the image capturing element. Incidentally, an arrangement of top, bottom, left, and right LED illumination units is given only as an example, and any combination of these may be used. The hood312is cut diagonally to allow contact with the windshield301. The material of the hood312may be, for example, silicon, resin, metal, rubber, wood, glass, or the like. It is possible to reduce the reflection of a flare or the like by mounting the hood312so that it is sufficiently close to the windshield301in this way. Further, a lens for the internal image capturing element may be arranged inside the hood312.

Similarly, the LED illumination units321,323,324, and325are arranged for the camera unit320, and a hood322is arranged to be surrounded by the LED illumination units. The hood322is cut diagonally to allow contact with the windshield301. Further, a lens for the internal image capturing element may be arranged inside the hood322.

A plurality of camera units310may be arranged laterally inFIG.3B, and the windshield301and the frame302are configured to have a width proportional to the number of camera units310that can be arranged.

Referring now toFIGS.4A and4B, the external configuration of the image capturing unit101will be further described.FIG.4Ais a view illustrating an example of an external configuration of the image capturing unit101when viewed from the side. The configurations illustrated inFIG.3AandFIG.3Bare also illustrated inFIG.4A.FIG.4Aillustrates that a heatsink is attached to the back of the LED illumination units311,313, and315. This is a cooling configuration for cooling the heat from each LED illumination unit. The cooling mechanism may be something that uses forced cooling by a fan or water cooling. Further, a control unit400which is connected to the LED illumination unit311and the image capturing element (not illustrated) is arranged. The control unit400includes mechanisms400A,400B, and400C for controlling the LEDs and the mechanism400B for controlling an image capturing element (not illustrated), and is connected to the information processing apparatus206by a cable401.

FIG.4Bis a view illustrating an example of a cross-sectional structure of a position indicated by an A-A line inFIG.3A.FIG.4Billustrates a cross-sectional structure of the windshield301in addition to the arrangements described above. Further, an image capturing element316is illustrated on the inside of the hood312.

Next, referring toFIG.5, a positional relation between the image capturing units101A and101B will be described. In the inspection system10, the image capturing unit101A and the image capturing unit101B are arranged to face each other through a region through which the inspection target passes, in the same orientation in which the image capturing element316is positioned more to the top side than the bent portion301aof the windshield301.

Hatched region501inFIG.5illustrates the angle of view of the image capturing element316B of the image capturing unit101B. Also, arrows502and503indicate the normal direction of the installation surface of the LED illumination units321A and325A of the image capturing unit101A, and indicate exemplary illumination directions. Arrow504indicates the direction in which the inspection target passes. Here, the light from the LED illumination units321A and325A has a diffuse component, but for the component that travels straight, the traveling direction of the light is parallel to the LED illumination units321A and325A, or perpendicular to or intersecting the plane of the windshield301arranged alongside the illumination units321A and325A. Therefore, the light from the LED illumination units321A and325A travels through the windshield301. Then, the light irradiated from the LED illumination units321A and325A, as indicated by arrows502and503, deviates from the angle of view of the image capturing element316B illustrated by the region501.

On the other hand, light from the LED illumination units321A and325A that is reflected when it strikes the inspection target is received by the image capturing element326A, and is visualized as an image. Therefore, it is desirable that the directions of installation of the LED illumination units321A and325A, in other words the directions in which the light is irradiated, be defined as the directions in which the light reflected from the inspection target is supplied most to the image capturing element326A. Further, since the intersection of the arrows502and503is set to be at a position or in a range through which the inspection target passes, the most light is irradiated onto the inspection target. Thus, it is possible to maintain the quality of the captured image because the amount of information of the inspection target can be maximized.

The positional relation between the image capturing units101A and101B, for example, can be decided in accordance with the size of the inspection target, the illumination angle of the LED illumination units, mechanical interference, or the like.

Further, there is a possibility that the illumination light from the LED illumination unit321A or the like will enter the facing image capturing element326B of the image capturing unit101B. Accordingly, it is possible to expose the image capturing elements326of the image capturing units101A and101B at staggered timings rather than exposing them at the same timing.

FIG.6is a view illustrating a relationship between the timing of the respective exposures in the image capturing units101and the light emission timing of the LED illumination units. InFIG.6, the control timing of the image capturing unit101A and the LED illumination units (311A,313A,314A,315A,321A,323A,324A, and325A) of the image capturing unit101A on the top side is illustrated. In the image capturing unit101A, image capturing is performed using the frame rate as 30 frames per second. A pulse601indicates the time over which the image capturing unit101A is exposed. The interval of the pulse601is approximately 33 milliseconds.

The LED illumination units of the image capturing unit101operate to cause the LEDs to emit light during the time of the exposure in the image capturing unit101A. However, if the light is turned on at the same rate of 30 frames per second as the image capturing unit101A, there is a possibility that flashing will be perceived by the human eye. Accordingly, it is possible to increase the number of times of lighting per unit time, to be more than the number of image captures per unit time. For example, when the number of image captures is 30 per unit time, the number of lightings may be 60 per unit time, or may be 90 per unit time. This makes it impossible for the human eye to perceive flashing.FIG.6illustrates the case of 90.

InFIG.6, the control timing of the image capturing unit101B and the LED illumination units (311A,313A,314A,315A,321A,323A,324A, and325A) of the image capturing unit101B on the bottom side is illustrated. In the image capturing unit101B, image capturing is performed using a frame rate of 30 frames per second. However, the position of the pulse603indicating the exposure timing of the image capturing unit101B is temporally staggered from the position of the pulse601and is also temporally staggered from the pulse602of the LED illumination units for the image capturing unit101.

Thus, in a duration in which the image capturing unit101B performs image capturing, the LED illumination units of the image capturing unit101A are turned off, and therefore the quality of the image captured by the image capturing unit101B does not deteriorate due to light from the LED illumination units of the image capturing unit101A. Similarly, in a duration in which the image capturing unit101A performs image capturing, the LED illumination units of the image capturing unit101B are turned off, and therefore the quality of the image captured by the image capturing unit101A does not deteriorate due to light from the LED illumination units of the image capturing unit101B.

Next, with reference toFIG.7, a relationship between the light receiving plane of the windshield301and the image capturing element316will be described.FIG.7is a view illustrating an exemplary cross-sectional structure for explaining the installation angle of the windshield301with respect to the light receiving plane of the image capturing element316.

As illustrated inFIG.7, the windshield301in present embodiment is configured as a plate-like member bent in a dog leg shape. More specifically, the configuration is such that a first planar portion301b, on the back side of which the image capturing element316, the hood312, and the LED illumination unit311are arranged, and a second planar portion301c, on the back side of which an LED illumination unit315is arranged, are connected via the bent portion301a. The LED illumination unit311is arranged alongside the first planar portion301bon the back side of the first planar portion301b, the LED illumination unit315is arranged alongside the second planar portion301con the back side of the second planar portion301c. Although not illustrated inFIG.7, the LED illumination units313and314are arranged on the back side of the first planar portion301b.

InFIG.7, the image capturing plane of the image capturing element316is represented by a dotted line701. A dotted line702indicates a plane parallel to the image capturing plane indicated by the dotted line701and is set to be in contact with the bent portion301aof the windshield301. Letting the angle of the first planar portion301bwith respect to the dotted line702be θ1, and the angle of the second planar portion301cwith respect to the dotted line702be θ2, θ2≥θ1. Regarding the magnitudes of θ1 and θ2, for example, the lower limit of θ1 may be about 16 degrees, the lower limit of θ2 may be about 26 degrees. However, these numerical values are merely examples; angles that are larger than an angle θ min at which the reflection image from the facing image capturing unit101does not enter the angle of view may be selected as the values of θ1 and θ2 having calculated the reflection from the windshield301or the like based on at least any of the angle of view of the image capture unit201of the image capturing unit101, the expected distance to the inspection target at the time of image capturing, the angle of installation, arrangement, irradiation angle, and angle with respect to the facing image capturing unit of the illumination unit202, or the like.

Incidentally, the angle with respect to the facing image capturing unit, for example, can be obtained as an intersection angle of the normal of the image capturing plane of each image capturing unit101. InFIG.5, the intersection angle is 0 degrees because the image capturing elements326A and316B of the image capturing units101A and101B facing each other are facing each other directly, but the intersection angle may be non-zero. Further, by also adding a101C to the image capturing units101A and101B, since a non-zero intersection angle is set in case of image capturing from three directions, it is possible to set values of θ1 and θ2 in accordance with the intersection angle.

FIG.8is a view illustrating an example of the external configuration of the hood312. The hood312may be made of, for example, a silicon material, and is brought into close contact with the back surface of the windshield301. The hood312takes a form in which a first cylindrical portion312aof the bottom side and a second portion312bthat is inversely tapered on the top side are connected. The second portion312bis provided from the middle of the first portion312ain this way to prevent interference with the angle of view of the image capturing element316—that is, in a case of an inversely tapered shape from the base, the diameter of the base is too small, and it interferes with the lens; also it impairs assembly efficiency—so it is to avoid these. If the height of the hood312can be made shorter, the first portion312amay be omitted.

Further, an opening portion of the second portion312bon the top side of the hood312, is cut in accordance with the inclination of the windshield301. The inclination angle of the opening surface corresponds to θ1 with respect to the horizontal plane, as illustrated inFIG.7. Thus by providing the hood312at an appropriate angle to the windshield301and bringing it into close contact with the windshield301, it is possible to prevent ghosting and flare due to noise other than specular reflection.

According to the present embodiment described above, by using a two-dimensional area sensor in the image capture unit in the image capturing unit in the inspection system for performing an appearance inspection of an inspection target, it is possible to widen the angle of view, and, it is possible to increase the inspectable area by capturing images a plurality of times. Further, because the positional relationship between the inspection target subject and the illumination at the image capturing timing changes when capturing images a plurality of times, since it is possible to acquire images in which the appearance of shadows and highlights differs, even the same subject can be inspected multiple times with different expressions, and it is possible to reduce the risk of overlooking the subject.

Further, by arranging a windshield that is bent in a dog leg shape in the image capturing unit, it is possible to avoid a plane being formed directly in front of the image capturing unit. Since it is possible to almost eliminate specular reflection with the configuration of the windshield, it is possible to avoid a situation in which image capturing quality is greatly reduced by the illumination at the time of image capturing being reflected by the windshield of the facing image capturing unit and appearing in the image.

Furthermore, by attaching the hood so as to be sufficiently close to the windshield, it is possible to reduce the reflection of flare or the like due to noise other than specular reflection. Further, since the hood can be brought into close contact with the windshield, it is possible to ensure the noise reduction effect more reliably.

It is possible to provide an image capturing unit having a configuration that makes it possible to further improve determination accuracy and an inspection system using the image capturing unit.

Summary of Embodiments

The above embodiments disclose at least the following image capturing unit and inspection system.

(1) An image capturing unit in an inspection system for performing an inspection target appearance inspection, the image capturing unit comprising:an image capture unit;an illumination unit arranged in a periphery of the image capture unit; anda protective unit covering the image capture unit and the illumination unit, whereinthe protective unit includes a plate-like member configured by a first planar portion and a second planar portion being connected through a bent portion bent in a dog leg shape, andthe image capture unit is located on a back side of the first planar portion.

(2) The image capturing unit according to (1), wherein the first planar portion has an inclination of a first angle in relation to an image capturing plane of an image capturing element that the image capture unit has,the second planar portion has an inclination of a second angle in relation to the image capturing plane of the image capturing element,and the second angle is equal to or greater than the first angle.

(3) The image capturing unit according to (2), wherein the illumination unit comprising,a first illumination unit positioned on the back side of the first planar portion and arranged alongside the first planar portion.

(4) The image capturing unit according to (2) or (3), wherein the illumination unit comprising,a second illumination unit positioned on the back side of the second planar portion and arranged alongside the second planar portion.

(5) The image capturing unit according to any one of (2) to (4), wherein the illumination unit further comprising,a third illumination unit positioned on the back side of the first planar portion and arranged parallel to the image capturing plane of the image capturing element.

(6) The image capturing unit according to any one of (2) to (5), wherein the image capture unit further comprises a hood for the image capturing element,and the hood has an opening portion that contacts a back surface of the first planar portion and that is cut at an inclination corresponding to an inclination of the first planar portion.

(7) The image capturing unit according to claim6, wherein the hood is configured by a cylindrical first portion and an inversely tapered second portion being connected,and the second portion contacts the back surface of the first planar portion.

(8) The image capturing unit according to any one of (2) to (7), wherein the image capture unit includes a two-dimensional area sensor.

(9) The image capturing unit according to any one of claims2to8, comprising a plurality of image capture units and a plurality of illumination units,wherein the protective unit covers the plurality of image capture units and the plurality of illumination units.

(10) An inspection system for performing an inspection target appearance inspection, the system comprising:a first image capturing unit according to any one of (2) to (9);a second image capturing unit according to any one of (2) to (9); anda processing apparatus that controls operation of the first image capturing unit and the second image capturing unit, and determines an inspection target to be sorted out from among inspection targets based on images captured by the first image capturing unit and the second image capturing unit, whereinthe first image capturing unit and the second image capturing unit are arranged to face each other through a region through which the inspection target passes, at an orientation in which the first planar portion of the first image capturing unit and the first planar portion of the second image capturing unit are respectively arranged on a top side.

(11) The inspection system according to claim10, wherein for the first image capturing unit and the second image capturing unit,the first angle and the second angle are calculated based on at least any of the angle of view of the image capture unit, an expected distance to the inspection target at the time of image capturing, an angle at which the illumination unit is installed, an arrangement and irradiation angle, and angle with respect to a facing image capturing unit, and the first angle and the second angle are set to be larger than a minimum angle at which a reflection image due to the plate-like member of one image capturing unit does not enter the angle of view of the other image capturing unit.

(12) The inspection system according to (10) or (11), wherein the processing apparatus controls the first image capturing unit and the second image capturing unit so that image capturing by the first image capturing unit and the second image capturing unit is executed temporally alternating.

(13) The inspection system according to (12), wherein the processing apparatus controls each of the illumination units so that an illumination by the illumination unit of the first image capturing unit and an illumination by the illumination unit of the second image capturing unit are executed temporally alternating in correspondence with the timing of image capturing by the first image capturing unit and the second image capturing unit.

(14) The inspection system according to any one of (10) to (13), wherein the processing apparatus makes the number of times the illumination unit is caused to emit light per unit time more than the number of times the first image capturing unit and the second image capturing unit capture images per unit time.