INSPECTION SYSTEM FOR QUALITY ANALYSIS OF A PRODUCT TO BE INSPECTED

Abstract

The invention relates to an inspection system for quality analysis of a food product, comprising conveyance means for moving it to an inspection area, a lighting device consisting of LEDs that emit a light sequence directed towards the inspection area to light up the product by transmission, a linear camera with at least one line of pixels for collecting a plurality of images in each light sequence of the lighting device, and focusing means for focusing the beam emitted by the lighting device. Advantageously, the lighting device is activated in a pulsed manner, generating a light sequence with at least two different illuminations, at least one of which is a transmission-pulsed illumination. The lighting device is aligned on the axis formed by the product to be inspected and the linear camera.

Claims

1. An inspection system for quality analysis of a translucent product (2) to be inspected, comprising: conveyance means (1) for moving the product (2) to be inspected through an inspection area (5), generating the movement thereof by means of forward advancement, a lighting device (3) consisting of LEDs (4) that emit a light sequence directed towards the inspection area (5), such that a light beam emitted by the LEDs (4) lights up the product (2) in the inspection area (5), a linear camera (6) with at least one line of pixels (6′) and being configured for collecting a plurality of images in each light sequence of the lighting device (3), the images being obtained by transmission of the light beam emitted by the lighting device (3) upon passage of the translucent product (2) to be inspected, focusing means for focusing the beam emitted by the LEDs (4), wherein the lighting device (3) is configured to be activated in a pulsed manner, generating a light sequence, partially lighting up the product (2) with at least two different illuminations, at least one of which is a pulsed illumination going through the translucent product, with the pulsed illumination being focused on a forward advancement direction of the conveyance means (1); wherein the linear camera (6) is configured to scan the lighted-up product (2) in the inspection area (5) such that the linear camera (6) acquires more than one image of a pixel of the product (2) for each forward advancement; and wherein the lighting device (3) is aligned on an axis formed by the product (2) to be inspected and the linear camera (6), with the lighting device (3) and the linear camera (6) being arranged on opposite sides of the product (2).

2. The inspection system for quality analysis of a translucent product to be inspected according to claim 1, wherein the conveyance means is translucent and wherein the LEDs (4) of the lighting device (3) are arranged below the translucent conveyance means (1), lighting up the inspection area (5) through which the product (2) passes.

3. The inspection system for quality analysis of a translucent product to be inspected according to claim 2, wherein the light beam which lights up the inspection area (5) comprises a width of less than 2 mm.

4. The inspection system for quality analysis of a translucent product to be inspected according to claim 2, wherein the focusing means for focusing the beam emitted by the LEDs consist of a single cylindrical lens (7).

5. The inspection system for quality analysis of a translucent product to be inspected according to claim 2, wherein the focusing means for focusing the beam emitted by the LEDs consist of independent lenses (7′) for each LED (4), such that the system is provided with as many independent lenses (7′) as LEDs (4) comprised in the lighting device (3), such that the illumination is focused in two dimensions, one dimension being in a transverse direction with respect to a forward advancement direction of the conveying means and the other dimension being in the forward advancement direction of the conveying means.

6. The inspection system for quality analysis of a translucent product to be inspected according to claim 1, further comprising collimating means for the narrowing of the light beam.

7. The inspection system for quality analysis of a translucent product to be inspected according to claim 1, wherein the LEDs comprised in the lighting device emit in at least two different wavelengths focused on a forward advancement direction of the conveyance means (1) and lighting up in an alternating manner.

8. The inspection system for quality analysis of a translucent product to be inspected according to claim 1, further comprising an ejection device (9) to allow sorting the product to be inspected.

9. The inspection system for quality analysis of a translucent product to be inspected according to claim 1, wherein the linear camera has a sensor of more than one line of pixels.

10. The inspection system for quality analysis of a translucent product to be inspected according to claim 1, wherein the lighting device (3) is configured to light up in one and the same wavelength and is activated in parts, in an alternating manner in the light sequence.

11. The inspection system for quality analysis of a translucent product to be inspected according to claim 1, wherein the lighting device is configured to emit a pulsed illumination with more than one wavelength, wherein at least one of the emitted wavelengths comprises a range of 650˜690 nm.

12. The inspection system for quality analysis of a translucent product to be inspected according to claim 1, further comprising an x-ray camera arranged close to the inspection area, with the linear camera obtaining images of the product to be inspected by transmission and the x-ray camera obtaining x-ray attenuation images.

Description

DESCRIPTION OF THE DRAWINGS

[0026] To complement the description made below and for the purpose of aiding to better understand the features of the invention according to a preferred practical embodiment thereof, a set of drawings is attached as an integral part of said description, wherein the following is depicted in an illustrative and non-limiting manner:

[0027] FIG. 1 shows a schematic perspective view of the inspection system for quality analysis of a product to be inspected, according to the description of the present invention.

[0028] FIG. 2 shows a view and a detail of the cross-section of the inspection area of the system depicted in FIG. 1, in which the lighting device and how the light goes through or is reflected on the product to be inspected are further observed.

[0029] FIG. 3 shows a view and a detail of the cross-section of the inspection area of the inspection system according to the description of the present invention, in which an optical element is included for focusing the beam emitted by the lighting device in the forward advancement direction.

[0030] FIG. 4 shows a view and a detail of the cross-section of the inspection area of the inspection system according to the description of the present invention, in which an optical element is included for focusing the beam emitted by the lighting device in two directions.

[0031] FIG. 5 shows a view and a detail of the cross-section of the inspection area of the inspection system, in which the LEDs lighted up at different times of the light sequence are depicted.

[0032] FIG. 6 shows the images obtained by LED transmission at 850 nm (detail A), 660 nm (detail B), and the chlorophyll index (detail C) calculated based on images A and B above.

PREFERRED EMBODIMENT OF THE INVENTION

[0033] FIG. 1 shown herein allows observing a general depiction of the inspection system object of the invention. Specifically, the inspection system for quality analysis of a product consists of the following elements: [0034] Conveyance means (1) for moving the product (2) to be inspected to an inspection area (5). Specifically, the conveyance means (1), preferably a translucent belt, generate the movement of the product (2) by means of a continuous movement by forward advancement. The presence of a translucent belt enables the light beam which goes through the product to be analyzed to go through said belt. [0035] A lighting device (3) consisting of LEDs (4) that emit a light sequence directed towards the inspection area (5), such that the light beam emitted by the LEDs (4) lights up the product (2) in the inspection area (5) by transmission. [0036] A linear camera (6) with at least one line of pixels (6′) for collecting a plurality of images in each light sequence of the lighting device (3). [0037] Focusing means for focusing the beam emitted by the lighting device (3) and advantageously lighting up only a narrow line and prevent the presence of light reflected on the product which may reach the linear camera (6).

[0038] As seen in FIGS. 2 to 5, the light sequence is generated by the lighting device (3) where the LEDs (4) comprised in the lighting device (3) are arranged, preferably below the inspection area (5). In this way, the product (2) to be inspected advances forward along the belt (1) until reaching the inspection area (5) and the light beam emitted by the LEDs (4) lights up the product (2) by transmission precisely when the product goes through the inspection area (5).

[0039] The illumination is activated in a pulsed manner to light up the product (2) to be inspected. The light sequence can further include front illumination.

[0040] Specifically, the product (2) is lighted up with at least two different illuminations, at least one of which is by transmission, with the illumination being focused on the forward advancement direction of the conveyance means (1).

[0041] As shown in FIG. 1, when the product (2) to be inspected reaches the inspection area (5), the product (2) is lighted up by the lighting device (3) and the linear camera (6) scans the lighted-up product (2).

[0042] Therefore, in the continuous forward advancement of the belt, the linear camera captures product images line by line, by way of scanning. A light sequence consists of as many images as different illuminations there are. For example, in the case of a system with illumination at 850 nm and 660 nm, a light sequence in which illumination at 850 nm is first activated, acquiring a product image from one line, and in which illumination at 660 nm is subsequently activated, acquiring another product image from one line, is obtained. This action is performed for each forward advancement of the product flow corresponding to the size of one pixel.

[0043] That is, the linear camera (6) acquires more than one image of a pixel of the product (2) to be inspected for each forward advancement, specifically one image per illumination.

[0044] The images collected by the linear camera are sent to an automaton, and after analyzing the obtained images, the software sorts the product into a quality category.

[0045] Optionally, if the final inspected product (2) is not of the required quality, the automaton sends an order to an ejection device (9) which is installed downstream of the belt and enables products which do not meet the required quality to be rejected.

[0046] As seen in FIG. 2, the lighting device (3) is necessarily aligned on the imaginary axis formed by the product (2) to be inspected and the linear camera (6).

[0047] Detail C of FIG. 2 shows a case in which the light beam emitted by the LEDs (4) goes through the product (2) to be analyzed, said product being located in the ideal location for the linear camera (6) to capture its images, offering reliable results of the quality of the inspected product (2).

[0048] However, detail B of FIG. 2 depicts a case in which the product (2) is partially lighted up laterally, that is, the light beam emitted by the LEDs (4) does not go through the product (2), but rather is reflected directly towards the camera. This situation affects the precision of the analysis and must be avoided, given that the light which has gone through the product is not being analyzed in this case, producing an incorrect reading of the quality of the inspected product. Furthermore, it should be noted that this reflected illumination has a greater density than the illumination which has gone through the product, severely distorting quality analysis.

[0049] In the embodiment of the invention depicted in FIG. 3, the focusing means consist of a single cylindrical lens (7). Advantageously, since the system is configured with a single cylindrical lens (7), the light beam is focused on the forward advancement direction of the product (2), such that the cylindrical lens (7) takes in the light beam emitted by the LEDs (4) of the lighting system (3), focusing in one dimension, forming a straight narrow line that is aligned with the inspection area (5), as seen in section C of FIG. 3.

[0050] Preferably, the straight narrow line of focused illumination must have a width of less than 5 mm. Advantageously, by lighting up a smaller area of the product to be analyzed, more accurate information about the product is obtained.

[0051] For example, if the product to be analyzed comprises an area of one square centimeter and has a defect measuring 2×2 mm in the lower part, it means that the defect is located on the surface of the translucent product on the illumination side. Therefore, if the entire area of the product is lighted up, the amount of light which has gone through the defect is only 4%, but if a narrow area measuring 1 mm in width, with the help of a single cylindrical lens, is lighted up, the amount of light going through the defect will be 20%, thereby facilitating defect detection.

[0052] In another embodiment of the invention depicted in FIG. 4, the focusing means consist of a plurality of independent lenses (7′) for each LED (4). In this way, the inspection system of the invention is provided with as many independent lenses (7′) as LEDs (4) comprised in the lighting device (3).

[0053] In this embodiment, since the focusing means consist of a plurality of independent lenses (7′), the light beam from the LEDs (4) is focused in two dimensions, one dimension being in a transverse direction with respect to the forward advancement direction of the belt (X) and the other dimension being in the forward advancement direction of the belt (Y).

[0054] Focusing the illumination in two directions by means of independent lenses (7′) prevents the presence of light directly reflected on one side of the product to be inspected towards the camera (6).

[0055] In the embodiment depicted in both FIG. 2 and FIG. 3, the mentioned focusing means are arranged between the lighting device (3) and the inspection area (5) through which the product (2) to be inspected moves. In this way, focusing takes place before the light beam emitted by the LEDs (4) strikes the product (2).

[0056] Moreover, it should be indicated that the system of the invention may optionally comprise collimating means, preferably, by way of slits, not depicted in the figures. In this sense, in another embodiment of the invention, the inspection system first allows focusing the light beam emitted by the lighting device (3), and then collimation takes place by means of the slits, thereby achieving the narrowing of the beam which strikes the product (2) to be inspected and analyzed.

[0057] It should be noted that the lighting system is less efficient if the light beam is collimated, but not focused.

[0058] Moreover, the lighting devices (3) can be programmed, lighting up in groups at different times. Therefore, as depicted in FIG. 5, the LEDs (4) of the lighting device (3) light up by transmission in one and the same wavelength and are activated partially, i.e., in parts, in a transiently alternating manner in a light sequence; in other words, not all the LEDs (4) are activated at the same time.

[0059] For example, only even-numbered LEDs (4) would be activated and not odd-numbered LEDs (4) so as not to produce direct reflected light. The odd-numbered LEDs (4) would be activated later. In this way, a sequence with two illuminations by transmission, where each of them lights up a part of the inspection area, would be obtained. The analysis algorithm of the image would then recompose the image of the product to be inspected using, from both illuminations, only that part in which the illumination was activated, thereby obtaining the complete image by transmission. Therefore, reflected light can be avoided without having to use individual lenses. The same scheme can be repeated by activating, for example, one LED out of every three or four LEDs, whereby less reflected light would still be obtained with a sequence of three or four illuminations.

[0060] The advantage of activating the LEDs (4) in an alternating manner is to prevent the generation of direct reflected light.

[0061] Moreover, FIG. 6 allows verifying the results obtained with the inspection system of the invention when the lighting device emits a pulsed illumination with more than one wavelength, wherein at least one of the emitted wavelengths comprises a range of 650˜690 nm and the other one is in the range of 800˜940 nm. Advantageously, this configuration and emission in a range of 650-690 nm allows measuring the absorption of chlorophyll present in the product to be inspected. In this way, when the product has a leaf adhered thereto or is more unripe, the presence of the leaf or unripeness can be detected since the wavelength of 650˜690 nm going through the product at that point (with leaves or unripened area) will be more attenuated in comparation with the length of 800˜940 than a product that comprises no leaves or is ripe. The different signal attenuation of the wavelength of 650˜690 nm is due to the absorption generated by chlorophyll.

[0062] Therefore, FIG. 6 shows the images of a plurality of pieces of fruit which have been obtained by transmission of the LED beam emitted at a wavelength of 850 nm (detail A) and 660 nm (detail B).

[0063] The chlorophyll index obtained in detail C is calculated based on details A and B. In this sense, FIG. 6 clearly shows in detail C the products and/or product parts containing chlorophyll, corresponding to those elements that are lighted up the most. Meanwhile, those products and/or product parts not comprising chlorophyll are darkened in detail C.

[0064] Lastly, it should be indicated that for any preferred embodiment of the invention, the inspection system includes an ejection device (9) to allow sorting, wherein the ejection device (9) receives the order according to the instructions sent by the automaton.