Dynamic magnetic information storage or retrieval – Recording on or reproducing from an element of diverse utility
Patent
1997-09-10
2000-09-26
Loomis, Paul
Dynamic magnetic information storage or retrieval
Recording on or reproducing from an element of diverse utility
360 46, 360 65, 396319, G11B 500, G11B 509, G11B 5035, G03B 1724
Patent
active
061249912
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is a process and a device for reading out binary information magnetically stored on a transparent magnetic layer. Transparent magnetic layers have recently become well known in photographic films, where they are used to record information for illumination and/or processing of photographic films according to the invention and to maintain data for access in devices used in processing. Because of the requirement that photographic films can not be altered essentially in their capacity to store images and thus in their transparency, these magnetic layers can contain only very little material. The magnetic fields of recorded signals are correspondingly weak; they may be lower by a factor of 200 than fields for customary sound and data recordings on nontransparent magnetic tapes or disks designed exclusively for that purpose.
Special measures must thus be taken for capturing and processing magnetic signals which make up the kind of magnetic code as, for example, described in the U.S. Pat. No. 4,987,439. Special amplification and means for evaluation have been developed as, for example, disclosed in the U.S. Pat. No. 4,964,139 for processing weak signals produced by magnetic heads. There a circuit with a single filter 18 is described whose purpose is to eliminate interference signals like the intrinsic noise of a pre-amplifier. It is extraordinarily difficult to tune a filter to multiple interference frequencies caused by various different recording speeds or densities.
SUMMARY OF THE INVENTION
The purpose of the invention is therefore to create an evaluation device suitable for the evaluation of extremely weak and/or varying magnetic signals.
This task is solved by
A process comprising the steps of filtering the preamplified signals at different filter frequency ranges, and differentiating the filter signals, such that those signals of the different filter frequency ranges which have the most plausible sequence of extreme values may be selected for further process.
Through development of the evaluation device according to the invention it is no longer necessary to separate the signal read out by the magnetic head and amplified by the amplifier with a single frequency filter from interference signals. Now the signal read-out and amplified signal are subjected to filtering through a number of various frequency filters and the preferred impulses are selected as bits on the basis of plausibility considerations and agreement from the different filtered signal sequences. Useful configurations of the invention bear on the kind of filtering sequence and differentiation, suppression of interference signals, as well as a device for carrying out the process.
Details concerning the embodiment of the invention are described in detail in Figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 a total schematic of the construction of the circuit for signal amplification and evaluation;
FIG. 2 the transmission characteristics of the frequency filters used;
FIG. 3 the configuration for time delay of filtered signals;
FIG. 4 the principle of differential subtraction of original and delayed signals;
FIG. 5 examples of the route of differently filtered and differentiated signals as well as for testing established extreme values and their digitization into bits.
FIG. 6 Examples of the evaluation of bit values as bit lengths in filtered and differentiated signals according to FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, a photographic film strip with a very thin magnetic layer is designated as 1. It is led past a magnetic read head 3 with a coil 4 in the direction of the arrow 2 in a film processing apparatus, for example a photographic printing machine. Coil 4, connected on one side to ground, is connected on its other end with the negative input 5a of an operational amplifier 5. Its output 5c is connected with the input 5a by a feedback resistance 6, which has a very high resistance of some ten M.OMEGA.. Operational amplifier 5 has a very high no-load amplification A.sub.0
REFERENCES:
patent: 5055938 (1991-10-01), Misumi et al.
patent: 5237464 (1993-08-01), Cronch et al.
patent: 5270875 (1993-12-01), Shah et al.
patent: 5490018 (1996-02-01), Yamashita
patent: 5519462 (1996-05-01), Spencer et al.
Agfa Gavaert Aktiengesellschaft
Loomis Paul
Neal Regina Y.
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