Optic Closure inspection with two cameras

Introduction

The optic closure inspection is the most modern, comprehensive and satisfactory way to control closures’ status, its only disadvantages being cost and complexity, as seen by the user side. It is devoted to detection of cocked (inclined) closures, broken TE (tamper evident) bands, closures applied too high or absent at all. Factors implying contamination of the product and extremal risks for Consumers. The basic operation principle implies a single CCD or CMOS-camera, allowing a partial coverage, < 180º, of the closure external lateral surface. The optic system includes 3 mirrors to increase the focal length, minimising optic aberrations due to parallax error. The optic axe is centred on the neck ring.

Why 2 cameras

This optic arrangement presents evident limits when trying to detect broken Tamper Evident Rings. That’s why 2-cameras systems, like in the figure at left side, are mandatory to prevent this occurrence. Also, with two cameras it results possible to check nearly 360º of the cap external surface. Whatever the model, a strobo flasher, today low-voltage model or IR LED matricial model, illuminates the bottle’ external sidewall, neck and closure. In case of low-voltage strobo flashes, em energy amounts to a few tens of joule, irradiated along approximately 0.1 m. With so short illumination times, also images of fast moving objects results crisp and frozen. Be a similar system composed of 1 or 2 cameras, the detection ratio results however relatively poor with respect to the modern final inspection systems. These last adopt 2 - 4 cameras and mirrors in an improved optic diagram, to precisely image the neck and cap area of the bottle.

Broken Tamper Evident Rings, missing and inclined cap, cap too high or too low are the controls most commonly performed by mean visual cap camera systems. Double camera systems present images of the same neck as seen by two opposite sides

The broken Tamper Evident Ring of a sport cap. The defect is macroscopic and surely assured detected at nearly 100% but the situation worsen rapidly for defects ~6 times smaller. In these cases, a double camera system reveals its superior detection ratio

Malpositioned Caps and Broken Tamper Evident Rings detected by mean of a couple of cameras anti-parallel oriented. Image shot by our staff at Font Salem, Valencia, Spain; a Company part of Grupo Damm

Links to other Closure controls:

Crown-Cork, Threaded Cap or LidUltrasound Inner Pressure Inspection IntroductionIn these web pages we have frequently remarked the necessity to answer the fundamental question:…is it safe, can be sold that bottle?

Plastic Cap Visual Check with 1 Camera. The optic closure inspection is the most modern, comprehensive and satisfactory way to control closures’ status, its only disadvantages being cost and complexity, as seen by the user side. It is devoted to detection of cocked (inclined) closures, broken TE (tamper evident) bands, closures applied too high or absent at all. All these factors implying contamination of the product and extremal risks for Consumers.

The basic operation principle implies a single CCD or CMOS-camera, allowing a partial coverage, < 180º, of the closure external lateral surface. The optic system includes 3 mirrors to increase the focal length, minimising optic aberrations due to parallax error.

Broken Tamper Evident Rings, missing and inclined cap, cap too high or too low are the controls most commonly performed by mean visual cap camera systems Links to other Closure controls pages:…

Links to other Closure controls: Contact

Optic Closure Presence inspection, with analog photosensorsIntroductionThe optic closure inspection, with analog photosensor, is one of the simplest inspections existing. It adopts an analog photosensor, with a projector irradiating passing closures by the top and a receiver giving out to an operational amplifier a signal whose extension, the duration counted in encoder pulses, is proportional to the reflection. …

Laser check of Closure InclinationLinks to other pages about Closure Inspection: The added value to apply a LASER slantedcap inspection to a Vision cap check Two different configurations exist for the LASER check of slanted caps:…

Inductive Closure or Lid Presence Inspection 4096x3079@1x. Introduction

The simplest and cheapest way to check for the closing status of a container, where the closure is metallic, is the inductive-digital. The sensor is then an inductive one, its output an NPN polarity, on-off signal.

The one figured on side shows an example of this basic solution, where the cap sensor is referred to a Trigger photosensor obscured by the container along its passage, before it starts to be detected by the inductive sensor. Disadvantages

The system is very cheap but it presents a relevant disadvantage.

It can be detected only:

cap presence;
cap absence;
metal caps (e.g., aluminium, steel or tin).
This meaning that a container capped by, i.e. a cap inclined 45º, then a container surely open, shall be considered correctly closed and passed to the Market.

The signal outcoming by these sensors is normally a quite fluctuating one: impossible to act on the signal duration, when trying to detect mal-positioned closures. Advantages

However simple, this system has however several important advantages:

capable to reach also the highest production speed, typically > 140000 cph;
economy; a sensor like the one partially visible in the image (Pepperl+Fuchs®) or one of the many equivalent by different Vendors, is very cheap (<100 $);
is always available wherever in the World.

IntroductionThe simplest and cheapest way to check for the closing status of a container, where the closure is metallic, is the inductive-digital. The sensor is then an inductive one, its output an NPN polarity, on-off signal. …

Inner Pressure Inspectionby InductionOscillograms deriving by the induction analog measurements of two different lids. Each oscillogram composed by the sequence of hundredths of individual samplings operated by a single-channel analog sensor. …

Ultrasonic fobbing systemsWhy the ultrasonic fobbing systems ?Common disadvantages of the closure optic inspection systems: Optic, with 1, 2, or 3 CCD-camerasTamper evidence band Missing closure, inclined and high closure…

3-D cap colour space. To perceive the rationale for the inspection of the caps’ colour, we recommended to see the video below. It has been filmed in a PepsiCo plant and in a beverage Bottling Line where, at the time of the film our staff commissioned twelve different formats, personalized by twelve different colours for the cap.

In this conditions the production face the risk of:

Operators errors in the special sort bottle + cap: entire cartons of wrong caps reaching the Capper;
caps of the wrong colour mixed in the lot of the caps of the correct colour. A solution pass thru the control of the colour of each one cap applied by the Capper Machine. Colour control made illuminating with a source of known spectrum (a halogen lamp) the cap. Part of the light reflected by the cap enters the lens of a trichromatic detector. This is a device with three separate channels, referred to the familiar fundamental colours red, green and blue.

The signal in the outfeed of each one channel is separately amplified and later digitised and processed, comparing the digitised value with upper and lower limits set during the commissioning.

The signals incoming by three separate channels, each one corresponding to a fundamental colour, are processed to deduce the cap colour. The couple of yellow colour vertical lines are the inspection window, the range of distances measured in millimetres equivalent to Encoder pulses. In the vertical axe of the diagram they appear, digitized in a scale of 4096 bits, the signals’ amplitudes. In the example shown, a cap has been measured thru all three channels with approximately the same amplitude ~1380 bits. The image setup in the meantime specifying a “good colour 1” implies that all caps whose chromatic mix similar to this one shall be considered correctly coloured. Where “correctly” means their colour is coherent with the currect production

As an example, refer to the graphic on right side:

a couple of yellow colour vertical lines represents the inspection window, the range of distances in the Inspector's Shifting-Register, where the three chromatic channels are evaluated;
red colour the red chroma signal, whose grey level is normalized (0 - 4096);
blue colour the blue chroma signal amplitude, whose grey level is normalized (0 - 4096);
green colour the green chroma signal, whose grey level is normalized (0 - 4096);
white colour their superimposed amplitude, whose grey level is normalized (0 - 4096).

Caps whose tri-chromatic mix is out of each one of the three allowed ranges, shall be rejected. In the example, a cap has been measured thru all three channels with approximately the same amplitude ~1380 bits. The image setup in the meantime specifying a “good colour 1” implies that all caps whose chromatic mix similar to this one shall be considered correctly coloured. Where “correctly” means their colour is coherent with the currect production

In the video above it is visible ad addition to the standard configuration of this kind of devices, namely a stainless steel curved screen, opposite to the source of light and trichromatic sensor.

The Sun in some special times of the day, gets into that PepsiCo Bottling Hall, infeeding the thrichromatic sensor. Knowingly, Sun’s spectrum is continous and centred on yellow colour. The screen allow to overwhelm these phases, preventing Electronic Inspector’s systematic errors: huge false rejects stopping the entire 50000 bph PET Bottling Line.

Caps' Colour InspectionTo perceive the rationale for the inspection of the Caps’ Colour, we recommended to see the video below. It has been filmed in a PepsiCo plant and in a beverage Bottling Line where, at the time of the film our staff commissioned twelve different formats, personalized by twelve different colours for the cap. …

Dewatering systemsRefer to the figure on right side, where a green colour scanning line intercepted a water drop scanning, and measured its distance to the bottle’s plastic, greater than toward the closure top surface: a wrong distance. …

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