GB2378799A

GB2378799A - Object identification apparatus

Info

Publication number: GB2378799A
Application number: GB0129168A
Authority: GB
Inventors: Graham John St Clair Assinder
Original assignee: Roke Manor Research Ltd
Current assignee: Roke Manor Research Ltd
Priority date: 2001-08-16
Filing date: 2001-12-06
Publication date: 2003-02-19
Anticipated expiration: 2021-12-06
Also published as: GB0129168D0; GB2378799B; GB0119930D0

Abstract

An object identification apparatus comprises excitation means such as an anvil to cause an object to be identified such as a coin 3 to emit sound, a microphone 5 to detect the sound, a filter 8 comprising a first input coupled to the microphone 5 to filter the output of the microphone 5, a delay line 8b coupled to the microphone 5 and to a second input of the filter 8 to provide thereto a delayed output. The filter 8 is adaptable to minimise the difference between the first and second inputs and wherein the filter 8 includes an output for producing an indication of the parameters of the filter 8 required to minimise the difference and an identifier 9 to identify the object 3 from the output filter parameters. The filter 8 may comprise a digital signal processor. The apparatus may also have a weighbridge 6 to weigh the object 3. There is also disclosed a method for object identification. The object identification apparatus may be used in a vending machine which provides goods and services. The vending machine may refuse to provide goods and services on the basis of the object identification.

Description

Object Identification Apparatus and Method This invention relates to object identification apparatus and a method for identifying an object. The invention is particularly, but not exclusively, applicable where the object is a metal token such as a coin to be validated in a vending machine or payphone or the like.

In one known type of coin validation apparatus, a coin inserted into a payphone is directed downward along a slot to fall edge-on to a metal surface called an"anvil". The impact is sufficient to cause the coin to audibly"ring"and the acoustic spectrum so generated is characteristic of the coin. The spectrum is then used to identify the coin. Examples of this type of system are disclosed in GB 2251111, GB 2215505, GB2222903 the teachings of which are incorporated herein by reference.

These prior art systems perform an analysis on the sound emitted by the coin. This is done by amplifying and then filtering the sound emitted by the coin and performing a fast Fourier transform on the filtered output to characterise the sound in a number of so-called filter bins. The bins are indicative of the energy in various parts of the sound and are characteristic of the coin.

The analysis applied to the bins requires processing time and the present invention arose from a realisation by the inventor that at least some of this processing time could be saved to render the identification process more efficient, expedient and more accurate in terms of distinguishing between objects having similar characteristics.

According to the invention there is provided object identification apparatus comprising excitation means to cause an object to be identified to emit sound, a microphone to detect the sound, a filter comprising a first input coupled to the microphone to filter the output of the microphone, a delay line coupled to the microphone and to a second input of the filter to provide thereto a delayed output wherein the filter is adaptable to minimise the difference between the first and second inputs and wherein the filter includes an output for producing an indication of the parameters of the filter required to minimise the difference and an identifier to identify the object from the output filter parameters.

By determining the parameters of the filter required to minimise the difference between the output of the microphone and a delayed version of the output less processing is required than would be the case if a filtered output were processed.

A further advantage of this arrangement is that it is less susceptible to noise than prior art arrangements because the noise present on the first input tends to cancel noise present on the second input.

The excitation means in the described embodiment is a metal surface referred to as an"anvil"against which the object is made to strike. (The object being in that case a coin falling in a coin slot to hit the anvil under the action of gravity. ) In other arrangements the object could be struck by the excitation means instead of the object being arranged to strike the excitation means. Non-contact means of excitation may be used such as exposure to sound or ultra-sound emitted by a sound generator or the application of a magnetic field to cause the object to vibrate.

The object can be any object that may be made to produce sound. In the described embodiment, the object is a coin but other types of financial tokens or other objects may be used. The coin is used to pay for goods or services provided by a vending machine in which the apparatus is incorporated. Of course, in alternative arrangements the apparatus may be used for the reason of identifying the object, for example, in order to distinguish it from other such objects. For example, the same apparatus could be used to identify objects on a production line. The apparatus may be used to identify faulty components because faulty components, for example, castings having cracks or other imperfections will produce sounds when struck which are different to the sounds produced by perfect castings.

Whilst in the described embodiment the sound produced by the object is audible to the human ear, the sound may be of or include components beyond the range of hearing. In the described embodiment the sound is classified on components in the range 60- 70KHz.

The invention also provides a method for identifying an object and for a transaction using the method or apparatus.

A specific embodiment of the invention will now be described, by way of example only, in which Figure 1 is a cross-section of a coin slot of a coin slot vending machine in accordance with the invention; and Figures 2 and 3 are a schematic block diagrams.

With reference to Figure 1, there is shown a schematic crosssection of a coin slot machine 1 in accordance with the invention. The machine includes a narrow slot 2 to maintain coins inserted into it in an edgewise orientation, that is to say the major face of the coin 3 is in the plane of the paper.

The slot 2 has located within it, an anvil 4. The anvil 4 is located at an elbow of the slot formed by a more or less vertical part of the slot and a sloping part of the slot. Adjacent the anvil is a microphone 5 and located in the sloping part of the slot is a weighbridge 6.

The coin 3 when inserted in the slot firstly falls under gravity to strike the anvil 4. The impact causes the coin 3 to vibrate acoustically. The acoustic vibrations are captured by the microphone 5 and passed to the novel detection circuitry to be described later.

The coin 3 then travels on passing over the weighbridge 6. The weighbridge 6 provides an additional detecting method to weigh the coin and also to detect the series of impacts produced by a coin which has a facetted edge (such as the British twenty pence piece coin shown in the figure).

The microphone 5 is connected to an analogue to digital converter 7, as is shown in Figure 2. The converter 7 converts the analogue signals generated by the microphone 5 as it detects sound produced by the coin 3 into digital representations of the sound. The digital signals are passed to a filter 8. The function of the filter 8 will be elaborated on later. An output of the filter 8 is coupled to a coin identifier 9. This in turn provides an output which is coupled to a coin accept or reject mechanism 10.

Figure 3 shows the circuitry in more detail. The filter 8 is furnished with an input which has two branches. A first branch, which leads directly to an adaptive filter 8a, and a second branch, which leads to a delay line 8b. The output of the delay line 8b is coupled to a reference input of the adaptive filter 8a.

The output of the adaptive filter 8a is coupled to an input of the coin identifier 9. The coin identifier 9 includes a processor 9a and a memory 9b. The processor 9a is programmed to operate in a manner which will be described in greater detail later to provide a coin reject or accept signal to the coin accept or reject mechanism 10.

The coin accept or reject mechanism 10 is of a form well known to the person skilled in the art and operates to direct an accepted coin to coin box (not shown) within the vending machine or to return the coin to the person using the machine in the event that the coin is rejected.

The filter 8 is configured as a digital signal processor (DSP) programmed to perform the delay and the adaptive filter function. The parameters of the filter 8a are varied in order to minimise the differences between the signal passed directly to it along the first branch and the delayed version of the signal input at the reference input. The parameters are then output to the coin identifier 9. It should be noted that it is the parameters necessary to achieve the minimisation rather than a filtered signal that is passed to the coin identifier 9.

The coin identifier 9 compares the input filter parameters with a pre-stored table of values for valid coinage in the frequency range 60

70KHz. The coin is accepted or rejected on the basis of the resultant match. The coin accept or reject mechanism 10 is then signaled to accept or reject the coin accordingly, and the services or goods provided or refused as appropriate.

Claims

Claims 1. Object identification apparatus comprising excitation means to cause an object to be identified to emit sound, a microphone to detect the sound, a filter comprising a first input coupled to the microphone to filter the output of the microphone, a delay line coupled to the microphone and to a second input of the filter to provide thereto a delayed output wherein the fil ! er is adaptable to minimise the difference between the first and second inputs and wherein the filter includes an output for producing an indication of the parameters of the filter required to minimise the difference and an identifier to identify the object from the output filter parameters.
2. Apparatus as claimed in claim 1 wherein the filter comprises a digital signal processor.
3. Apparatus as claimed in claim 1 or claim 2 wherein the excitation means comprises an anvil against which the object is struck.
4. Apparatus as claimed in any one of claims 1,2 or 3 wherein the object is a financial token.
5. Apparatus as claimed in claim 4 wherein the financial token is a coin.
6. Object identification apparatus substantially as hereinbefore described with reference to an as illustrated by the drawings.

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7. A vending machine for the provision of goods or services comprising object identification apparatus as claimed in any preceding claim.
8. A method for object identification comprising the steps of: causing the object to emit sound; detecting and producing signals representative of the emitted sound; in a filter minimising the difference between the signals and delayed versions of the signals by varying parameters of the filter ; comparing the parameters necessary to minimise the difference with stored parameters; and identifying the object on the basis of the comparison.
9. A method as claimed in claim 8 wherein the object is a financial token.
10. A method as claimed in claim 9 wherein the financial token is a coin.
11. A method of providing goods or services comprising a method of object identification as claimed in any one of claims 8 to 10 and the further step of providing or refusing to provide the goods and services on the basis of the object identification.
12. Goods or services as provided by a method as claimed in claim 11.
13. A transaction comprising a method as claimed in any preceding claim.