Device for reading an elongate magnetic data carrier

Details Device for reading an elongate magnetic data carrier Device for reading an elongate magnetic data carrier

2002-07-01

2003-07-29

Strecker, Gerard R. (Department: 2862)

Electricity: measuring and testing

Magnetic

With means to create magnetic field to test material

C324S236000, C194S317000, C194S320000, C235S449000

Reexamination Certificate

active

06600313

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a device for reading an elongate magnetic data carrier attached to or embedded in an article. It relates particularly to active read heads of the type described in GB 2035659A for permanently structured magnetic tape such as WATERMARK (Registered Trade Mark), which is commercially obtainable from Thorn Secure Science Limited, Swindon, England.
BACKGROUND OF THE INVENTION
Active read heads of the above type provide an a/c energising electromagnetic field, and a detection circuit which is capable of reading data on data carriers such as for example printed magnetic patterns or WATERMARK tape. However, a disadvantage of such active read heads is that the detected signal falls off rapidly with distance if the spacing between the data carrier and the read head is increased.
FIG. 1
shows experimental data indicating how the signal varies with spacing. This variation makes it difficult to read data when the spacing to the data carrier is uncertain, or known to vary. For example, some bank notes have magnetic threads embedded in them, as disclosed in WO 9819866A, the threads being exposed on the surface in some areas (windows) and buried under the surface in other areas. The present UK £20 note is an example of a banknote with a security thread embedded in this fashion, so as to be exposed in spaced windows. Since a banknote is approximately 100 microns thick, the variable spacing can cause detection problems when used with a read head which operates as shown in FIG.
1
.
A second disadvantage of existing active read head systems for reading the type of narrow magnetic thread used for banknotes arises from the variable positioning of the threads. In the case of banknotes, this variability is introduced intentionally since perfectly aligned threads make it difficult for automated machinery to handle a stack of banknotes. For this reason a mechanised magnetic reader cannot readily pre-align the head with the thread, whilst a swipe reader may have difficulty in tracking a buried thread, which is difficult to see. Known active read heads have a track width of typically 1.4 mm, which can be difficult to align to a 2 mm wide thread. It is an object of the present invention to mitigate the above disadvantages.
SUMMARY OF THE INVENTION
According to the present invention there is provided a device for reading an elongate magnetic data carrier attached to or embedded in an article. The device comprises an active read head adapted to have a track width having a lateral extent greater than the width of the data carrier. The magnetic field produced by the read head in use results in a signal detected by the read head from said data carrier, which signal has an amplitude which varies by less than 50% for head to data carrier spacings of from 0 to 60 microns. The signal can have an amplitude which varies by less than 25% for head to data carrier spacings of from 0 to 60 microns. The present invention also relates to a swipe reader for magnetic data carriers (such as cards or documents) that include such a device.
A passive read head having similarities to the present invention is disclosed in U.S. Pat. No. 3,753,255. However, in this device the wide read head is simply employed to make overlap easier, as passive heads do not respond to a threshold signal level.


REFERENCES:
patent: 3753255 (1973-08-01), Di Veto
patent: 4328519 (1982-05-01), Way
patent: 4518919 (1985-05-01), Ishida
patent: 5096038 (1992-03-01), Potter et al.
patent: 5512822 (1996-04-01), Masuda
patent: 6073845 (2000-06-01), Kawase
patent: 6127034 (2000-10-01), Chorley
patent: 6310475 (2001-10-01), Kawase et al.
patent: 2049934 (1991-08-01), None
patent: 2035659 (1980-06-01), None
patent: 2098768 (1982-11-01), None

Affiliated with

Also associated with

Rating

Device for reading an elongate magnetic data carrier does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Device for reading an elongate magnetic data carrier, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for reading an elongate magnetic data carrier will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3021370