GB2261505A

GB2261505A - Optical monitoring of container filling

Info

Publication number: GB2261505A
Application number: GB9222013A
Authority: GB
Inventors: Hans P Friedrich
Original assignee: HANS P FRIEDRICH ELEKTRONIK GM
Current assignee: HANS P FRIEDRICH ELEKTRONIK GM
Priority date: 1991-11-15
Filing date: 1992-10-20
Publication date: 1993-05-19
Anticipated expiration: 2012-10-20
Also published as: ITMI920991V0; IT226990Y1; DE9114260U1; ITMI920991U1; GB9222013D0; GB2261505B; FR2683791A3; FR2683791B3

Abstract

Apparatus for optically monitoring the filling of an open and/or transparent container (6), e.g. a blister pack, having rows of depressions or cavities for receiving articles. e.g. tablets or capsules, is characterized in that the container is movable relative to a detector, that the detector is constituted by a line sensor (4) positioned transversely to the movement direction and parallel to the container, and that a light source (1) is provided for the reflective or transmissive illumination of the container (6). Electronics are provided for the comparison of an intensity distribution of the reflected or transmitted light measured with the line sensor (4) with a nominal value distribution and for emitting a control signal dependent on the comparison. A circuit is provided for synchronizing the scan by the line sensor (4) or the evaluation with the relative movement. <IMAGE>

Description

Apparatus for optical filled article control.

The invention relates to an apparatus for the optical filled article or product control in the case of an open and/or transparent container with depressions or cavities arranged in multirow manner for receiving the filled article or product.

Such apparatuses are e.g. used for the control or inspection of blister packs with tablets, capsules, etc. A check is made to establish whether each depression or cavity has been filled with the article and optionally the filled article is checked for breakage.

If cameras are used for optical filled article control purposes, a surface to be monitored must be imaged with the aid of a lens on the quasi-punctiform photosensitive part of the camera. It is considered disadvantageous in the case of large monitoring widths that a spatial extension along the optical axis is necessary, that distortions and light decrease can occur at the edge and that the photosensitivity is low.

The problem of the invention is consequently to provide an apparatus for filled article control whilst avoiding the aforementioned disadvantages, which is simple and inexpensive to manufacture and provides an improved resolution.

According to the invention this problem is solved by an apparatus for the optical filled article control in the case of an open and/or transparent container with depressions or cavities arranged in multirow manner for the reception of the filled article, characterized in that the container is movable relative to a detector, that the detector is constituted by a line sensor arranged parallel to the container and transversely to the movement direction, that a light source is provided for the reflective or transmitting illumination of the container, that an evaluation electronics is provided for the comparison of the intensity distribution of the reflected or transmitted light measured with the line sensor with a nominal value distribution and for emitting a control signal dependent on the comparison and that a circuit is provided for synchronizing the scanning by the line sensor or the evaluation with the relative movement.

The idea on which the invention is based is to use a line sensor, such as is known from fax equipment. The line sensor operates with an imaging scale of 1:1, so that no reducing optics are required and consequently there is an extremely low overall height of the apparatus in the direction of the optical axis. Thus, there are no distortions in the marginal area and an excellent photosensitivity is obtained.

Moreover, such a sensor is inexpensively available. As desired and as a function of the particular application, the line sensor detects reflected light of a correspondingly arranged light source when the container is opaque and transmitted light thereof when the container is transparent. The line sensor forms a one-dimensional intensity distribution of the reflected or transmitted light transversely to the movement direction. The measured light intensity varies through filled articles located in the optical path and thus, by comparison with a nominal value distribution a decision is made as to whether all the intended areas have been correctly filled with articles and a corresponding control signal is emitted.By a synchronization of the scan with the relative movement of the container to the line sensor, it is ensured that only the intended areas of the container are checked for complete filling with the articles.

A preferred embodiment of such a filled article control apparatus in the case of a deep-drawn film or foil, which is moved over a guide plate with longitudinal grooves for receiving deep-drawn depressions, is characterized in that an illuminating slit extending transversely to the movement direction is provided in the guide plate, that the light source is positioned parallel to the illuminating slit on one side of the guide plate and that the line sensor is positioned parallel to the illuminating slit on the other side of the guide plate for the detection of the light traversing the film or foil.

This leads to an extremely compact construction, because the line sensor is quasi-directly arranged on the film or the guide plate.

The illuminating slit substantially reduces the influences of stray or extraneous light. In the case of the present transillumination of the film a particularly good resolution is obtained, so that it is in particular possible to detect any breakage with respect to the filled article.

The influence of extraneous light is significantly introduced by an IR-light source and an IR-filter positioned upstream of the line sensor.

In order to ensure a sharp imaging and therefore high resolution, a lens array is positioned upstream of the line sensor. In particular, the lens array uses cylindrical lenses with a refractive index varying over the radial extension thereof. Such lens arrays are used in fax equipment and scanners (SLA-Selfoc Lens Array), so that they are inexpensively available. They are characterized by a very compact construction and favourable optical characteristics. The photosensitivity of the apparatus is increased by the use of the lens array.

Preferably there is a serial processing of an electrical signal of the line sensor corresponding to the intensity distribution of the light. Thus, the requirements made on the hardware are limited and allow simple, inexpensive production. Even in the case when there are large numbers of image points, a processing speed adequate for the monitoring of conventional manufacturing processes is obtained.

In particular digital signal processing is provided.

An embodiment is characterized by an integrator unit for the summation of several line sensor signals prior to the comparison with a nominal value distribution. Thus, e.g. a complete blister pack can be checked in the case of a predetermined line screening, without having to take account of gaps located between the filled articles in the movement direction. This also permits a checking of the projected surface content of individual filled articles and therefore a breakage detection.

An advantageous embodiment is characterized by a circuit for reading masters or originals and a memory unit for storing one or more nominal value distributions. Thus, very simple nominal value distributions can be inputed and replaced as a function of the product to be monitored.

For setting the sensitivity there is an inputable tolerance range for the comparison of an optionally summated sensor signal distribution with a nominal value distribution.

In order to obtain a particularly simple embodiment, use is made of a rotor wheel with angular momentum generator for recording the relative movement for the synchronization.

The invention is described in greater detail hereinafter relative to the drawings, wherein show: Fig. 1 a diagrammatic sketch of an inventive apparatus in section.

Fig. 2 a section II-II according to fig. 1.

Fig. 3 the signal of a line sensor.

Fig. 4 a diagrammatic sketch of a line screening.

An inventive apparatus according to fig. 1 has an IR-light source 1, a lens array 2, an IR-filter 3 and a line sensor 4 with a plurality of photodiodes. In the embodiment light beams 5 from the light source 1 traverse a container 6, which is here formed by a film 7 with deepdrawn depressions 8 for receiving filled articles 9, such as tablets.

The film or foil 7 is placed on a guide plate 10 with longitudinal grooves 11 for guiding the depressions 8. The light source 1 is positioned transversely to the longitudinal grooves 11 on the underside of the guide plate 10 and extends over the entire width of the film 7. Correspondingly the lens array 2, the filter 3 and the line sensor 4 are located above the guide plate 10.

It can be gathered from the section according to fig. 2 that the guide plate 10 has an illuminating slit 12, which extends transversely to the longitudinal grooves 11.

Through the illuminating slit 22 the light 5 strikes the back of the film 7, passes through the latter and after traversing the lens array 2 and the filter 3 is detected by the line sensor 4, if no filled article 9 is located in the optical path. Thus, in the embodiment according to fig. 1 an intensity distribution I as a function of the locus r shown in fig. 3 is obtained on the line sensor 4. The signal path I(r) reveals gaps 13 caused by filled articles 9 interrupting the optical path. The width of the gaps 13 is correlated with the spatial transverse extension of the filled articles 9. Thus, a damaged filled article 9', i.e. in this case a fragment of a tablet, leads to a gap 13' of reduced width.Thus, a not shown evaluation electronics by means of the intensity distribution I(r) measured by the line sensor 4 can establish whether the depressions 8 are in each case filled with filled articles 9 and can optionally carry out a breakage control with respect to the latter.

An arrow 14 in fig. 2 shows how the film 7 is moved in the direction of the longitudinal grooves 11. In the embodiment the relative speed of the film 7 to the line sensor 4 is synchronized with the scanning rate in order to obtain a uniform line screening 15, as sketched in fig. 4. This makes it possible to summate in the signal path I(r) the gaps 13 successively occurring in the vicinity of a longitudinal groove 7, so that there is a representative value for the projection surface of the filled articles 9, which is compared with a nominal value for breakage control purposes. As a result of a uniform line screening 15 it is also possible in the case of separated blister packs to summate over each row, i.e. all the filled articles 9 of a longitudinal groove 11 of a pack, the resulting gap widths and subsequently carry out a nominal value comparison.Thus, in this way there is an overall check of each individual blister pack and optionally the individual "row values" can be summated, so that the decision as to whether a blister pack has been completely filled is reduced to the comparison of two numbers (sum of the row values and the nominal value).

The synchronization of the film advance rate with the scanning rate takes place in the present embodiment with the aid of a rotor wheel on the film 7, an angular momentum generator connected thereto and a circuit correlating the scan with the generator pulses - said parts not being shown in the drawing.

For inputting a desired nominal value distribution preferably a master or original is measured and the data obtained are stored together with all the necessary format details. In this way a nominal value input can very easily and rapidly take place. Moreover, by recalling a specific nominal value distribution from a plurality of stored distributions in the case of production changes it is possible to achieve a simple adaptation of the apparatus to the filling article control on the existing product.

The line sensor 4 provided can evaluate up to 4800 image points with a scan width of up to 295 mm, so that a very good resolution is obtained.

The resulting one-dimensional signals are sharply imaged on the line sensor 4 by the lens array 2 (SLA optics), so that there is a very good resolution and high photosensitivity.

The photosensitivity is on the one hand (slightly) dependent on the film material used and on the other hand (strongly) on the pixel surface of the sensor. Thus, the high photosensitivity is mainly obtained by the line sensor. The pixel size of the line sensor is approximately 60 pm x 60 pm = 3.6 10 mm and the pixel size of standard sensors for reducing optics are approximately 14 pm x 14 pm = 1.96 10-4mm (i.e. surface factor approximately 18). The SLA optics improves the photosensitivity of the sensor system compared with a reducing system by a factor of 1 to 8 (typically 2), as a function of the optics.

As a result of the IR-filter provided and the use of an IR-light source, there is a considerable reduction in the influence of extraneous light, so that there is also a significant reduction in the shielding expenditure with respect to extraneous light.

The signals of the line sensor 4 are read out in serial manner and evaluated. Preferably the necessary function such as evaluation, synchronization and sequential control are carried out with the aid of a microprocessor circuit.

Claims

1. Apparatus for the optical filled article control in the case of an open and/or transparent container (6) with depressions or cavities arranged in multirow manner for the reception of the filled article, characterized in that the container is mov able relative to a detector, that the detector is constituted by a line sensor (4) arranged parallel to the container and transversely to the movement direction, that a light source (1) is provided for the reflective or transmitting illumination of the container (6), that an evaluation electronics is provided for the comparison of the intensity distribution of the reflected or transmitted light measured with the line sensor (4) with a nominal value distribution and for emitting a control signal dependent on the comparison and that a circuit is provided for synchronizing the scanning by the line sensor or the evaluation with the relative movement.

2. Apparatus according to claim 1 for the filled article control in the case of a deep-drawn, transparent or opaque film, which is moved over a guide plate with longitudinal grooves for recep tion of deep-drawn depressions of the film, characterized in that an illuminating slit (12) extending transversely to the movement direction is provided in the guide plate (10), that the light source (1) is positioned parallel to the illuminating slit (12) on one side of the guide plate (10) and that the line sensor (4) is positioned parallel to the illuminating slit (12) on the other side of the guide plate for the detection of the light (5) traversing the film (7).

3. Apparatus according to claims 1 or 2, characterized by an IR light source (1) and an IR filter (3) positioned upstream of the line sensor (4).

4. Apparatus according to one of the preceding claims, characterized by a lens array (2) upstream of the line sensor (4).

5. Apparatus according to claim 4, characterized in that the lens array (2) has cylindrical lenses with a refractive index varying over the radial extension thereof.

6. Apparatus according to one of the preceding claims, characterized by a serial processing of an electrical signal of the line sensor (4) corresponding to an intensity distribution I(r) of the light (5).

7. Apparatus according to one of the preceding claims, characterized by a digital signal processing.

8. Apparatus according to one of the preceding claims, characterized by an integrator unit for the summation of several line sensor signals prior to the comparison with a nominal value distribu tion.

9. Apparatus according to one of the preceding claims, characterized by a circuit for reading in masters and a storage unit for stor ing one or more nominal value distributions.

10. Apparatus according to one of the preceding claims, characterized by an inputable tolerance range for the comparison of an option ally summated sensor signal distribution with a nominal value distribution.

11. Apparatus according to one of the preceding claims, characterized by a rotor wheel with angular momentum generator for recording the relative movement for the synchronization.