Abstract:
A device for the recording of number and size classification of objects, wherein the objects pass between a light source (1) and an objective (3)/CCD-line camera (2) further transmitting data to a signal processing card (4). The signal processing card (4) is connected to a PC-card (5) which executes calculations of the measured data for the determination of the number of objects as well as size classification. When classifying by size, the PC-card (5) also gives signals to an actuator (7) controlling flaps (8) guiding the objects to appropriate channel/chute.

Description:
TECHNICAL FIELD 
     The current invention comprises a method and a device for the recording of the number and size classification of objects, particularly live fish. 
     PRIOR ART 
     Intensive production of fish (breeding of fish) is a rapidly growing trade. It is anticipated that its importance still will grow strongly in extent. In connection with the intensive production of fish, the recording of number of fish and the size classification of fish are frequently required. 
     Sale of live fish is usually done on the basis of number and, as a sale may comprise several hundreds of thousands, the execution of a rapid and accurate recording of fish number becomes of great importance. In order to achieve the largest possible growth, it is important regularly to carry out size classification of the fish such that the size variation in the different storage vessels is kept at a limited amount. The individual fishes grow with varying speed, and larger fish restrict the growth of smaller fish kept in the same vessel. 
     There are several methods for the counting and size classification of live fish. Usually, the counting of fish is performed manually. However, several devices for the automatic recording of number have emerged recently. These automatic counting devices are characterized in that they require a distance between adjacent objects, in order to achieve an accurate recording of number. This requirement restricts the capacity of the devices substantially. For the size classification of live fish, a series of different methods are used, e.g. using rotary rollers having an uniformly ascending slot, or using several gratings having varying slot widths. Common to these methods is that the size classification occurs on the basis of the thickness of the fish. A number of fish species, such as e.g. turbot, halibut and other flounders, exhibit great variations in the proportion between thickness and size/weight. 
     Both when recording the fish number and when classifying fish by size, the fish have to be treated as non-injuriously as possible. 
     DESCRIPTION OF THE INVENTION 
     The object of the current invention is to provide a method and a device of the kind mentioned above, which is accurate, non-injurious to the fish, a minimum time of residence in air, and which has a high capacity. 
    
    
     The single FIGURE of the drawing shows one embodiment of the device and method of the present invention. 
    
    
     According to the invention, its objects are achieved through measuring the area of the fish when they are falling freely. Each fish falls between a light source (1) and a CCD-line camera (2) associated with an objective lens (3), and the fish will then form a shadow area which is conceived by the CCD-camera. A signal processing card (4) records and stores data conceived by the CCD-line camera. These recorded data are further read by a computing-card (5) which executes calculations. The area recorded is influenced both through the size of the object and its speed at the time of recording. In order that objects having the same size shall be recordedwith the same shadow area, it is necessary that the objects have the same speed. According to the invention, this is achieved in that the objects fall freely from a certain height. In case several objects pass the lens simultaneously, e.g. laterally of each other, the computer-card will calculate the number of objects on the basis of a recorded mean value of single objects. In contrast with other known principles of counting, this principle does not require a distance between adjacent objects. 
     Prior to using the device for counting, the user decides a probable mean value through executing test measurements of individual objects or throughthe use of stored and already known values, and what permissible variation on either side of this value that is to be estimated as individual objects. This tolerance is determined on the basis of the existing variation by size for objects to be recorded. If the objects have the samesize, then the tolerance is determined to be approximately equal to zero. In connection with the counting of fishes wherein the sizes of the individual fishes vary, the tolerance values should vary about 30% on either side of the mean value. Objects smaller or larger than this interval will be estimated as noise (the recording is rejected) or as two or more objects, respectively. For each individual object recorded, i.e. the area recorded is within the specified tolerance values, the mean valuewill be corrected. All recorded areas of objects determined to be single objects, are continuously accumulated and divided by the number of the individual objects recorded. Thus, the mean value calculated when the counting is terminated, will be most correct--more correct the more singleobjects being recorded. This ultimate calculated mean value is then used inorder to calculate the number of fish recorded to be &#34;consecutive&#34;. These &#34;consecutive&#34; areas are accumulated in order to calculate the number on the basis of this ultimate recorded mean value. Number of fish incorporated into this accumulated &#34;consecutive&#34; area, is calculated on the basis of the last calculated mean value. 
     Thus, the total number of fish is the sum of the number of individual fish and estimated number of &#34;consecutive&#34; fish. As the device performs calculation of the number of objects also in the case of &#34;consecutive&#34; objects wherein e.g. two &#34;consecutive&#34; objects form a shadow area which isapproximately the double of the area recorded for individual objects, spacing between adjacent objects is not required for the achievement of anaccurate recording of the number. In order to obtain the best accuracy possible, the method requires that the objects fall facing the same side toward the objective lens/CCD-line camera. In the case of recording the number of fish, this means that the fish falls facing the belly/back or profile toward the objective lens/CCD-line camera. Through the mounting ofsoft brush ledges (6) in the slot wherein the objects are recorded, the narrower side of the objects will always face in the direction of fall andthe widest toward the objective lens/CCD-line camera. 
     As the device according to the invention makes the recording of the area ofthe objects, these data would give a description of the size of the objects--a small object will be recorded with a smaller area than a largerobject. These data describing the area of the object are, as previously mentioned, transmitted to the computer-card which, moreover, transmits an off/on-signal to one or more actuators (7). The actuator controls one or more flaps (8), so that objects of the same size group are guided to the same outlet. The specified limits for the various size groups are stored in the computer-card. In the case of classification of objects, the methodrequires a spacing between the objects. Spacing between the objects is achieved through accelerating the objects in a uniformly sloping chute (9). 
     The described invention is in no way limited to the embodiments shown, but may be realised in various ways without departing from the main idea described above.