BACKGROUND

The invention relates to the processing of raw shrimps, including the automated visual inspection of a continuous stream of shrimps and the diversion of rejects. In the shrimp-processing industry, raw shrimps are peeled by machine and the shells discarded. But some of the shrimps exit the peeling machine with residual shell. Other of the shrimps are damaged in the peeling machine and broken into bits. Shrimp bits and shrimps with residual shell are undesirable in the final product.

SUMMARY A shrimp processing system embodying features of the invention comprises an imaging chamber and a conveyor conveying a stream of shrimps from an infeed end to a discharge end through the imaging chamber. The imaging chamber includes a UV source continuously subjecting an exposure region of the conveyor in the imaging chamber to ultraviolet radiation, a white-light source turned on and off periodically to subject the exposure region to white light only when the white-light source is turned on, and a camera imaging the exposure region to take a first image of the shrimps on the conveyor when the white-light source is turned on and a second image when the white-light source is turned off. A controller turns the white-light source on and off and processes the first and second images to identify shrimps to be rejected as rejects. A method for processing shrimps comprises: a) conveying shrimps through an imaging chamber; b) illuminating the imaging chamber continuously with ultraviolet radiation; c) turning a white-light source on to illuminate shrimps being conveyed through an exposure region; d) taking a white-light image of the shrimps in the exposure region; e) turning the white-light source off after the white-light image is taken; f) taking an ultraviolet image of the shrimps in the exposure region; and g) repeating steps c) through f) periodically.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view from above of the imaging and inspection portion of a shrimp processing system embodying features of the invention. FIG. 2 is a side elevation view of the shrimp processing system of FIG. 1 with the facing side open.

FIG. 3 is an enlarged view of a portion of the shrimp processing system of FIG. 2.

FIG. 4 is a further enlarged view of the lighting system of the shrimp processing system of FIG. 3.

FIG. 5 is a flowchart exemplifying the operation of the imaging and inspection portion of the shrimp processing system of FIG. 1.

FIG. 6 is a block diagram of a control for a shrimp processing system as in FIG. 1.

DETAILED DESCRIPTION

The imaging and inspection portion of a shrimp processing system is shown in FIG. 1. The shrimp processing system 10 in this example version receives raw shrimps peeled in a water-filled tank 12 separated into two halves by a divider 14. But in other versions, the tank 12 need not be water-filled or have a divider. The shrimps are peeled by one or more automated peeling machines upstream of the tank 12. The shrimps are distributed in uniform layers on inclined conveyor belts 16 by reciprocating paddles 18. The bottom upstream ends of the belts 16 are in the tank 12. The shrimps on the inclined conveyor belts 16 drop off upper ends onto another conveyor 20 at its upstream infeed end 22. The drop helps separate the shrimps from one another. The conveyor 20, such as a belt conveyor, is normally run at a greater speed than the inclined belts 16 to further separate the shrimps. Although, in this example, two inclined conveyor belts 16 are used, a single conveyor belt or even another kind of infeed could be used to deliver shrimps to the conveyor 20.

The conveyor 20 conveys the stream of generally separated shrimps through an imaging chamber 24 that prevents outside ambient light from entering. The shrimps on the conveyor 20 are imaged under visible light, such as white light, and under ultraviolet (UV) radiation in the imaging chamber. From the white-light and UV images, a visual inspection system identifies rejects— (a) shrimps with residual shell and (b) bits, i.e., shrimp pieces smaller than a predetermined or user-settable size— and their positions on the conveyor. A controller uses the identification and positional information from the visual inspection system to control air-jet nozzles in an ejector module 26 to blow rejects of a first kind, e.g., shrimps with residual shell, from the stream of shrimps to a first reject destination 28, shown in FIG. 1 as a flume, and to blow rejects of a second kind, e.g., bits, to a second reject destination 30, also shown as a flume. Conveyance means other than flumes, such as belt conveyors, tubes, or chutes, can be used instead. The residual-shell rejects are carried by the first flume 28 back to the upstream peeling machine for re-peeling to detach residual shell. The rejected bits are carried by the second flume 30 to be collected as animal feed or for other uses. Shrimps not rejected are not diverted from the stream and fall off a discharge end of the conveyor 20 onto a discharge conveyor for further processing, such as deveining and inspection.

More details of the imaging and sorting portion of the shrimp processing system are shown in FIG. 2. Shrimps conveyed out of the tank 12 on the inclined conveyor belts 16 drop onto the infeed end 22 of the belt conveyor 20. The belt conveyor 20 is driven by a motor- driven drive shaft and sprocket set 32 in the belt's lower return run. The upper run of the belt conveyor 20 is supported in a carryway 34 that extends from the infeed end 22 to an opposite discharge end 23. The conveyor 20 conveys the stream of shrimps continuously through the imaging chamber 24 from an entrance 36 to an exit 37.

Housed in the imaging chamber 24 are a white-light source 38, such as arrays of light-emitting diodes, and a UV source 40. In the examples of FIG. 2, the sources 38, 40 are mounted on leading and trailing plates 42, 43 angled downward away from a central plate 44 and extending across the width of the belt conveyor 20. The central plate includes an opening through which a camera in a visual inspection system 46 captures an image from an exposure region 48 on the belt conveyor 20. (One example of a visual inspection system is the SiftAI® system sold by Smart Vision Works of Orem, Utah, U.S.A.) A temperature control system 50, e.g., an air conditioner, including a temperature sensor adjacent the UV source 40, maintains the temperature of the air around the UV source generally constant at a temperature within a predetermined range, e.g., between 0°F and 150°F, to prevent the intensity of the UV radiation from varying more than is acceptable.

The belt conveyor 20 conveys the shrimps off its discharge end 23. As the shrimps fall from the conveyor 20, air-jet nozzles in the ejector module 26 arranged in two rows 52,

53 are individually and selectively actuated to blow rejects of the first kind and rejects of the second kind from the stream of falling shrimps into the first and second reject destinations 28, 30. The rest of the falling shrimps drop onto a discharge conveyor (not shown) for further processing.

As shown in FIGS. 3 and 4, the lighting system 54 comprises three plates 42, 43, 44 above the belt conveyor 20. The central plate 44, which is parallel to the plane of the belt conveyor 20, has a window 56 through which a camera 58 in the visual inspection system 46 images the exposure region 48 on the conveyor 20. The two flanking plates 42, 43 are mirror images of each other. Each plate 42, 43 supports two sets 60, 61 of white-light sources 38, such as light-emitting diode (LED) arrays. Between the white-light sources 60, 61 in each flanking plate 42, 43 is a UV source 40, such as a pair of UVc tubes 62. The flanking plates 42, 43 include cutouts for diffusers 64, 65 for the LED arrays and for bandpass filters 66 for the UV tubes 62. The bandpass filters confine the UVc energy illuminating the exposure region 48 to a narrow frequency band. The diffusers 64, 65 diffuse the white LED light shining on the exposure region 48. Other arrangements of the white-light sources 60, 61 and the UV tubes 62 are possible.

Also housed in the imaging chamber 24 are ballasts 68 for the UV tubes 62, air filters and a compressor 70 (generally) for the air-jet nozzles, and circuit boards 72 for the controller, power supplies, and other support circuitry. An air duct 73 directs cooled air from the temperature control system 50 to the UV sources 40 to maintain their temperature. A temperature sensor 69 near each UV source 40 provides temperature feedback to the closed-loop temperature control system. Because the UV tubes are relatively slow to power up, the UV source is left on continuously rather than turned off and on to ensure a consistent radiation intensity for imaging.

The ejector module 26 houses two arrays of valves 74, 75 that are controlled by the controller to selectively supply bursts of air to corresponding air-jet nozzles 52, 53 to divert rejects from the stream of shrimps exiting the belt conveyor 20.

A block diagram of a control for the imaging and inspection system is shown in FIG. 6. A controller 76, such as a programmable logic controller or other programmable processor executing program steps in a program memory, controls the timing and receives imaging information from the visual inspection system 46. The controller 76 also turns on and off the white-light source 60, 61 for the white-light imaging. The controller 76 activates each of the air-jet valves 74, 75 over control lines 78, 79. A flowchart of an example implementation of one cycle of the imaging, inspection, and sorting process is shown in FIG. 5. First, the controller turns the white-light source on. Then the controller commands the visual inspection system to take the white-light images of the exposure region on the conveyor. The controller then turns the white-light source off. Although the UV source is on continuously, its intensity level is enough below the intensity of the white light that it does not affect the white-light image. After the white-light image is taken, the visual inspection system identifies the boundaries of objects in the exposure region of the conveyor. If the object boundaries enclose an area of less than a predetermined or user-settable number of pixels, the object is considered too small to be a significant piece of shrimp meat and is ignored.

All objects whose boundaries exceed that number of pixels are considered pieces of shrimp meat and their position in the exposure region of the conveyor saved. If no objects large enough to be considered pieces of shrimp meat are in the image, the inspection cycle is ended. If any objects in the white-light image are large enough, the visual inspection system takes a UV image with the white-light source turned off. Any shell present on a shrimp fluoresces under the UVc radiation and is detected in the UV image captured by the visual inspection system. The detected shell is associated with an object detected in the white-light image. The position of the shrimp with residual shell is sent to the controller by the visual inspection system so that the controller can eject that object to a first reject flume to be recirculated back through the upstream peeling machine.

If a large object has no detected shell, the visual inspection system further processes the object's white-light image to determine if the object is a shrimp bit (a piece of shrimp meat whose boundary encloses an area smaller than an area corresponding to a predetermined minimum shrimp size), a clump of shrimps (multiple overlapping shrimps whose combined size defines a boundary enclosing an area that exceeds an area corresponding to a maximum shrimp size), or an acceptable shrimp. If an object is classified as a clump, it is not treated as a reject. A bit, on the other hand, is treated as a reject of a second kind destined for ejection to a second reject flume. Acceptable shrimp and clumps are both allowed to pass through without diversion to a discharge conveyor for further downstream processing. The visual inspection system sends image information that includes the position of rejects of the first kind (shrimps with residual shell) and of the second kind (bits) to the controller. The controller, with knowledge of the conveyor speed and the rejects' positions on the conveyor, controls the air-jet valves to eject rejects of the first kind to the first flume and rejects of the second kind to the second flume. The visual inspection system also sends counts of the number of bits, the number of clumps, the number of shrimps with residual shell, and the number of acceptable shrimps to the controller for statistical analysis.

Although the shrimp processing system has been described in detail with respect to an exemplary version, other versions are possible. For example, characteristics other than bits and residual shell could be classified as defects, and objects with those characteristics diverted from the stream of acceptable shrimps. Clumps are one example. Other examples are objects recognized as small fish, pieces of debris, and unrecognized objects. So as these examples suggest, the claims are not meant to be limited to the details of the exemplary version.