EP1599844B1 - Method and device for testing coins - Google Patents

Abstract

Disclosed is a method and device for testing coins which are placed in a coin acceptor unit and which are displaced in front of an image sensor consisting of lines and columns, whereby said image sensor records an image of the coins that are to be tested. At least one of the front columns in the direction of movement of said coins and/or at least one line of the image sensor captures parameters, which in conjunction with the temporal detection information, are used to provide information on the movement of said coins. It is determined independently from said parameters when the coin will appear in a desired overlap area for recording, whereby the image sensor is shifted into an activation mode of the columns and lines of the overlap area and recording is triggered.

Description

The invention relates to a method and a device for testing coins, in which the image of the coin is detected with an image sensor.

In the coin coinage detection, it is known to use photographic image sensors which typically have pixels arranged in columns and rows. It is necessary to determine the right time of the recording of the moving object, ie the coin (here also tokens or tokens or the like should fall under the term coin). A problem is to capture the coin in the unrestrained movement and to monitor the course of the coins only with the existing image recording system or the image sensor. The dynamic behavior of a coin passing past an image sensor and the creation of an image by the optical image sensor must be made with accurate consideration of the sweep times through the imaging area and the pick-up speed of the sensor. It is crucial to determine the right amount of exposure time and time of capture. Although it is possible in special cases, it is not to be expected that the coin moves through the receiving area of the image sensor at a constant speed and certainly does not stay in it for a short time. Four time ranges are to be investigated, namely the entry of the coin into the sensor area, the recording / exposure time, the data transfer or transfer for image processing in an evaluation device and the image processing, analysis and evaluation. While no fixed time dimension is specified for the fourth period, with the exception of the maximum time of the overall process, the first three time segments are extremely time-critical.

Infeed times have been found for selected coins, the break-in time being defined here from the dipping of the coin edge into the receiving area of the image sensor until the coin has been fully captured by this receiving area. The measured break-in period was between 4.5 and 9.9 ms and that of 0.01, 0.10, 1 and 2 euro coins at 4.9; 5.9; 6.99 and 7.71 ms. The desired diameter range of the coins to be measured is between 15 mm and 33 mm. Measurements in real coin validators showed a maximum coin speed of 3 m / s. Given the time relationships, it is unthinkable to track the coin run to the proper position of the shot through a cyclic scan of the image. In addition, in such a case, the data transfer times from the image sensor to processors to be processed are much too long.

The publication JP 2001 230977 A discloses a token validation method in which a position of a token entered into a corresponding validator is detected, and an image sensor is activated in response to that position, but the token has a known diameter and passes through the reviewer at a known constant speed becomes.

The invention has for its object to provide a method and apparatus for testing coins with an image sensor for receiving an image of the coin to be tested, in which the time of recording the image of the coin or the location of the recording is reliably determined and with which the data transmission times are minimized from the image sensor to the evaluation.

This object is achieved by the features of the main claim and the independent device claim. The measures specified in the dependent claims advantageous refinements and improvements are possible.

In the invention, the property of image sensors is used to be able to read only partial areas. Since the scanning speed of the individual pixels is independent of their number, the transmission time can be almost in proportion to the number of dots to be read. Characterized in that only at least one of the front in the direction of movement of the coin columns and at least one line of the image sensor capture parameters of the coin, which together with the temporal information of the detection of a To provide information about the movement of the coin, and that is determined depending on these parameters and the temporal information, when the coin is immersed in a desired for recording cover area of the image sensor, the image sensor switched to an activation of the columns and rows of the coverage area and the recording is triggered, it is possible to monitor the movement of the coin and accurately calculate the time of the actual taking of the image of the coin, due to the activation of only the coverage area the coin with the image sensor is reduced the time for reading the image data.

By detecting the vertex of the coin through the at least one column in the direction of movement, the diameter of the coin is determined by which a statement about the height and width of the overlapping area can be made.

By scanning the front edge and the apex of the coin and the time information of the scan and the diameter of the coin can be calculated in a simple manner, the speed of the coin, especially for small, slow running coins, this speed information is already sufficient to the time of Specify recording because the recording area of the image sensor is much larger than the coin area and thus an uncontrolled leakage from the sensor area is unlikely.

It is particularly advantageous that according to the invention, after detection of the vertex of the coin at least one line of the image sensor is activated at the height of half the diameter to repeatedly scan the front edge of the coin, since depending on the sampling times and distances traveled, the speed and / or Acceleration of the coin can be calculated exactly. Thus, the recording time can be accurately determined, even if the coin undergoes a delay or acceleration in the course of their run-in.

It is advantageous that when passing through the coin through the at least one column of the height profile of the coin is detected and evaluated, are recognized in the presence of discontinuities in the course of altitude ripples.

Advantageously, a lighting device is provided, which is activated in a pulse-like manner at the time of recording, as a result of the determination of the time of recording, a good illumination can be achieved, wherein the duration of the illumination can be determined depending on the speed of the coin.

Fign. 1 - 4

unterschiedliche Bewegungszustände der Münze in Bezug auf einen Bildsensor und

Fign. 5 und 6

eine schematische Darstellung der Abtastung von Münzen mit Riffeln.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it

FIGS. 1 - 4

different states of movement of the coin with respect to an image sensor and

FIGS. 5 and 6

a schematic representation of the sampling of coins with corrugations.

The device according to the invention is installed in a coin validator, preferably in the coin channel, in which the other measuring systems of the coin validator are likewise present, and the device described can be designed as a subsystem of the coin validator control. The device has an image sensor, wherein the image sensor is to be understood as meaning the entire recording device with optics. In addition, a lighting device is arranged, which is assigned to the image sensor and which has a flash function, ie generates a pulsed illumination of the coin surface.

In Fig. 1 schematically, a device according to the invention is shown and it has arranged in the region of a coin track 1 image sensor 2 with appropriate optics and an evaluation unit 3, which is part of the Münzprüfersteuerung and a lighting assembly 4. The receiving device embodied as the image sensor 2 is set with the optics so that a specific field of view and a specific focus range are predetermined, wherein a coin 5 to be photographed should be arranged in this area so that no optical distortion or darkening occurs. The image sensor 2, whose representation indicates the coverage area, is provided with a plurality of columns and rows of pixels, which are connected to the evaluation unit 3 and which individually or in areas of the evaluation unit 3 for their initialization and activation for the readout of the data can be controlled from the sensor and for the actual recording. The recording is the process of "electronic fixation" of the optical image, ie with an electronic "shutter" the optical function is taken as a charge carrier. This happens in a possible short period of time to avoid motion blur. While the data is being read from the sensor, the coin is already moving. With the control of the rows and columns for recording the lighting device 4 is also controlled.

Thus, a usable recording of a coin 5 can be achieved, based on the movement parameters of the incoming coin 5, the time of Recording can be determined via the evaluation unit 3 at the desired measuring position or at the desired recording location. For this purpose, in the preferred embodiment, only the first column 7 of the image sensor 2 activated in the direction of movement 6 of an incoming coin 5 is activated at the beginning of acquisition, the pixels of this first column 7 being continuously read out by the evaluation unit 3 and the coin infeed being awaited. When the coin 5 enters the image sensor, the front edge is detected by the column 7 and detected by the evaluation unit 3, which activates a height control which is intended to detect the vertex of the coin.

Upon reaching the vertex accordingly Fig. 2 determines the evaluation unit 3, the diameter of the coin 5, which is stored as a first measurement of the system. From the diameter of the desired coverage area is set.

At this time, a first estimation of the coin infeed speed is possible because a speed can be calculated from the time of the front edge scan, the time of the vertex scan, and the diameter. In the simplest case, ie if certain blurs are allowed, this information is already sufficient to fix the time of the recording, which can be calculated from the speed and the desired measuring position. This is especially true for small, slow running coins, since the desired receiving area shown in dashed lines 8 covers in this case a multiple of the coin area and thus an uncontrolled leakage from the sensor area is unlikely. However, if you expect the speed changes on arrival, an additional control of the passage of the coin is necessary.

For this additional control of the run will open Fig. 3 referred to, in which a pixel line 9 is activated on the center line with respect to the diameter of the coin 5. This activation is carried out by activation of the evaluation unit 3 after detecting the diameter of the coin 5. In this case, the first scan line 7 can be deactivated. The scanning of the leading edge of coin 5 on the centerline continuously provides the progress of the coin's passage through the system. With the temporal information of the scanning of the front edges and the distances covered in each case, the respective speed and, if desired, the respective acceleration can be determined, which then serve to determine the time of arrival of the coin at the measuring position. Depending on this temporal prediction and / or when the coin 5 has completely arrived in the designated receiving area 8, the rows and columns of the image sensor in the height and width predetermined by the diameter of the coin 5 are initialized by the evaluation unit 3 as coverage area at the receiving location and triggered at the predicted time. This is in Fig. 4 shown in which the coin is shown in the desired coverage area 10 with the image sensor. The overlap area of the image sensor 2 to be recorded can be optimally selected by the previously determined diameter of the coin and the time determined at the measuring position from the speed or accelerations or accelerations.

Depending on the coin size becomes the overlap or recording area limited by the control of the rows and columns by the evaluation unit 3, whereby the time for reading the image data is reduced to a minimum. If the evaluation of the data is adjusted to this, even areas outside the circular image of the overlapping area 10 located outside the circular image can be suppressed to save space, ie these areas are not forwarded by the evaluation unit 3 with regard to their signals.

When recording accordingly Fig. 4 At the same time the lighting arrangement 4 is triggered by the evaluation unit 3, which likewise determines the exposure time from the previous information about the speed and the diameter. For a reproducible as possible shadowless illumination of the coin surface during recording a diffuse, uniform and bright as possible illumination of the coin is required. This is activated as already mentioned and because of the high power consumption pulsed only at the time of recording.

The illumination for the recording can be formed for example by a plurality of annularly arranged light-emitting diodes with a diffuse reflector.

According to existing findings, an exposure control of the recording must be carried out with the aid of a targeted control of the lighting. This is necessary because circulating coins have a significantly large spectrum of contamination and oxidation and thus reflectivity. Furthermore, for reasons of cost usually a lens with fixed aperture is used.

Due to the expected high running speed of the coin, an exposure control by the exposure time is to be excluded if possible. Exposure must be as short as possible to avoid blurring. There remains the possibility of controlling the supply current of the lighting elements or a gain control of the image sensor.

In addition to the lighting for the actual recording lighting is needed for the control of the coin inlet, which can be designed as a point or line lighting with lower light intensity or energy than the main lighting in the area.

Regardless of the requirements for the illumination for the reception of the coin, other illumination techniques can therefore be used in the lead-in area with which further measured quantities can be determined, e.g. flat bundled to determine with the shadowing embossing depths, multi-colored lighting to the detection of two-color coins, colored lighting to detect the material.

It should also be noted that the infeed control lighting must be activated several times, if not continuously, throughout the coin infeed period.

Of course, this lighting is also controlled to run-in control of the evaluation unit 3, which basically monitors the inlet. It can also determine the average brightness of the coin used for the exposure control.

In addition, a column within the scanning area 8 can be scanned in support of the run-in control in the first column. The timing of this position can then be used in determining the velocity along with the spacing of the columns.

There are also image sensors that do not allow freely positionable reading of image data, but make a blockwise reading of pixels or a downshift to a multiple smaller resolution possible. Also in these cases, the aforementioned sampling can be performed by means of columns and possibly lines, the columns and rows then having a reduced pixel number.

In Fig. 5 and Fig. 6 a so-called Riffelprüfung is shown, which is feasible with the preferred embodiment. The entry of the coin into the image sensor or the measuring system is monitored by the fast scanning of the first column and the vertex of the coin, ie their diameter, as mentioned, determined. When checking the height gradient, discontinuities can be rated as ripples. With appropriate mathematical correlation, the detection of polygonal coins is possible.

As in Fig. 5 is shown, an enlargement of the upper Münzrandes 11 when passing through the first column 7 of the image sensor 2 is shown. In the simplest case, only one column is scanned and the repeated change of the uppermost pixel during the passage of the vertex is recognized as corrugation. With knowledge of the coin speed can be concluded so on the corrugation width.

An extended shape with two adjacent columns 7, 12 simplifies the detection of a corrugation, since then two adjacent pixels each provide two negated signals. Their change indicates the presence of corrugation on the edge of the coin 11. For simplicity, was in Fig. 6 assumed a corrugation depth of the dimensions of a pixel of the image sensor. Depending on the resolution of the image sensor, the corrugation depth can also be several pixels. Then the corrugation depth becomes a measurable feature of the coin.

Claims (11)

1. Method for testing coins (5) which are inserted into a coin checker and run past an image sensor (2) which has lines and columns and which records an image of the coin (5) to be checked, at least one of the front columns (7) in the direction of movement (6) of the coin of the image sensor (2) scanning a front edge of the coin (5) and detecting parameters, which together with the temporal detection information provide information about the movement of the coin (5), and wherein as a function of these parameters it is determined when the coin (5) will appear in a coverage area (10) of the image sensor 2) which is desired for recording, the image sensor (2) being switched into activation of the columns and lines of the coverage area (10) and recording being triggered,
   characterised in that
   also the apex of the coin (5) is scanned by the at least one front column (7) in the direction of movement (6) and that the diameter of the coin (5) is determined from the scanning of the apex, wherein after detection of the apex of the coin (5), at least one line of the image sensor (2) is activated at the level of half the diameter.
2. Method according to claim 1, characterised in that the speed of the coin (5) is calculated as a function of the moments of scanning the front edge and the apex as well as of the diameter.
3. Method according to one of the claims 1 or 2, characterised in that in each case the front edge of the coin (5) is scanned during run-in and the speeds and/or accelerations of the coins (5) are calculated as a function of the scanning moments and distances covered.
4. Method according to one of the claims 1 to 3, characterised in that the time and/or the position of the coin (5) for the recording is determined as a function of the speed and/or the acceleration.
5. Method according to claim 4, characterised in that the front edge of the coin (5) is scanned by an additional column (12), which is arranged in the direction of movement (6) of the coin (5) offset to the at least one front column (7), and in that the speed is calculated as a function of the times of scanning the front edge and the distance between the columns (7, 12).
6. Method according to one of the claims 1 to 5, characterised in that, as the coin (5) runs through, the height pattern of the coin is detected and evaluated by the at least one column (7), and discontinuities in the height pattern are evaluated as grooves.
7. Method according to claim 6, characterised in that the groove width is determined once the coin speed is known.
8. Method according to one of claims 1 to 7, characterised in that an illumination device for illuminating the coin (5) is activated in a pulsed manner at the time of recording.
9. Device for testing coins which are inserted into a coin checker, said device having an image sensor (2) which has lines and columns for recording an image of the coin (5) to be checked and passing the image sensor (2), and an evaluation device (3) connected to the image sensor (2), at least one of the front columns (7) in the direction of movement (6) of the coin (5) of the image sensor (2) being activated to detect parts of the coin (5), and the evaluation device (3) determining the desired coverage area (10) from the signals of the image sensor (2) and associated temporal information and triggering the image sensor to record, the lines and columns of which may be activated independently of one another and/or in areas, characterised in that the evaluation device (3) is arranged for determining the apex and thus the diameter of the coin (5) from the signals of the at least one front column and to activate, after detection of the apex of the coin (5), at least one line of the image sensor (2) at the level of half the diameter.
10. Device according to claim 9, characterised in that an illumination device is connected to the evaluation unit (3) for pulsed illumination of the image sensor (2) at the time of recording.
11. Device according to one of the claims 9 or 10, characterised in that an additional illumination device is provided to illuminate the coin (5) for its run-in check.

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