Process and device for detecting foreign bodies in a liquid

Claim 1

The process for detecting foreign bodies, particularly solids, in a liquid contained in at least one recipient transparent to a certain light, whereby the liquid is placed in movement and is illuminated so that an image thereof produced by reflection, diffraction or attenuation, corresponding substantially to all the continuous apparent surface of the liquid contained in said recipient, is formed on a light sensitive surface, wherein, at an initial instant, a first image of said apparent surface as formed on said light sensitive surface is analyzed point by point, and the analog values of the results of this analysis are digitalized and memorized; at a subsequent instant, a second image is analyzed point by point, the analog values of the results of the second analysis are digitalized and compared by digital subtraction point by point from the memorized results of the first analysis, and the numerical value of each of said digital differences is compared with at least one pre-established digital numerical threshold indicative of foreign bodies considered as inadmissible, wherein the value of said threshold significant of comparison varies as a function of time to take into account the slowing down of the movement of said liquid in the recipient and to obtain a substantially constant threshold of detection of the inadmissable foreign bodies, and wherein the difference of illumination taken into account on two different images, of which at least one is memorized, is compared with said varied threshold of detection.

Claim 7

A device for detecting foreign objects, particularly solids, in a liquid, comprising a source of light for illuminating at least one recipient containing said liquid and a detector assembly including an optical system and a photosensitive surface in which the direction of the light illuminating the recipient is substantially perpendicular to the optical axis of the detector assembly, wherein said device comprises: a light sensitive surface comprising a plurality of microphotoreceivers in the form of a matrix of adjacent receiving and read cells, defined mechanically and electrically, excitable and readable independently of one another, the surface of said matrix being greater than the image of the apparent surface of the liquid contained in the recipient, defined by the width of the recipient and the height of the liquid therein, said matrix of photosensitve cells being connected to an integrated opto-electronic circuit, of which the output is connected by a serial analog channel to the input of an analog-digital converter, of which the output is connected to the input of a memory whose minimum capacity corresponds to the digitalized representation of an image, a first comparison member providing, by subtraction, the differences between two images of which at least the first has been memorized, for constituting a reference, and a second comparison member comparing said differences with at least one pre-established significant threshold and delivering a signal when at least one of said differences is greater than said significant threshold.

Claim 8

A device for detecting foreign objects, particularly solids, in a liquid, comprising a source of light for illuminating at least one recipient containing said liquid and a detector assembly including an optical system and a photosensitive surface in which the direction of the light illuminating the recipient is substantially perpendicular to the optical axis of the detector assembly, wherein said device comprises: a light sensitive surface comprising a plurality of microphotoreceivers in the form of a matrix of adjacent receiving and read cells, defined mechanically and electrically, excitable and readable independently of one another, the surface of said matrix being greater than the image of the apparent surface of the liquid contained in the recipient, defined by the width of the recipient and the height of the liquid therein, said matrix of photosensitve cells being connected to an integrated opto-electronic circuit, of which the output is connected by a serial analog channel to the input of an analog-digital converter, of which the output is connected to the input of a memory whose minimum capacity corresponds to the digitalized representation of an image, a first comparison member providing, by subtraction, the differences between two images of which at least the first has been memorized, for constituting a reference, and a second comparison member comparing said differences with at least one pre-established significant threshold and delivering a signal when at least one of said differences is greater than said significant threshold.