« PreviousContinue »
United States Patent  [ii] Patent Number: 5,886,789
Roller et al.  Date of Patent: Mar. 23, 1999
 OPTICAL SURFACE TESTING MEANS FOR LINEARLY MOVING, TAPE-LIKE MATERIALS
 Inventors. Albrecht Koller; Bernd Scholtysik,
both of Miinchen, Germany
 Assignee: EMTEC Magnetics GmbH,
 Appl. No.: 802,909
 Filed: Feb. 20, 1997
 Foreign Application Priority Data
Mar. 1, 1996 [DE] Germany 196 07 793.1
 Int. CI.6 G01N 21/84
 U.S. CI 356/430; 356/238; 356/431;
 Field of Search 356/429-430,
356/238, 431; 250/559.4, 559.44, 559.45,
 References Cited
U.S. PATENT DOCUMENTS
3,584,225 6/1971 Linemann 365/238
3,972,624 8/1976 Klein et al 356/200
4,595,840 6/1986 Puumalainen 250/572
5,047,652 9/1991 Lisnyansky et al 356/429
5,118,195 6/1992 Dobbie 356/430
5,130,555 7/1992 Suzuki et al 250/559
5,283,623 2/1994 Muhlberg et al 356/238
5,357,335 10/1994 Sparks et al 356/237
5,461,481 10/1995 Bowen et al 356/430
FOREIGN PATENT DOCUMENTS
306 742 3/1989 European Pat. Off. .
32 12 438 4/1982 Germany .
1103491 2/1968 United Kingdom .
Primary Examiner—Robert Kim
Attorney, Agent, or Firm—Keil & Weinkauf
A surface testing device, operating by reflection, for linearly moving, tape-like materials, for example paper or polymer films, is suitable for automatic online registration of linear irregularities transverse to the direction of movement. The testing device includes a suitable test distance, at least two optical inspection units and at least one electronic circuit arrangement for detecting both the individual signals of the inspection units and the coincidence signals. In addition, a magnetic information medium wound in the form of a roll on a hub is tested by the surface testing device and carries a machine-readable and/or visually readable quality identification.
11 Claims, 2 Drawing Sheets
OPTICAL SURFACE TESTING MEANS FOR
LINEARLY MOVING, TAPE-LIKE
BACKGROUND OF THE INVENTION 5
1. Field of the Invention
The present invention relates to a surface testing means, operating by reflection, for linearly moving, tape-like materials, in particular for an information-carrying tape 1Q coated with a magnetic recording layer.
2. Description of the Related Art
When tape-like materials of this type are used, they have to meet high requirements with regard to freedom from errors. In particular, linear surface irregularities transverse to 15 the running direction of the tape are undesirable. These form in particular as a result of creasing during their production in a tape coating machine. In this procedure, a tape-like substrate is unwound from a roll, transported in its running direction through the machine by means of positively driven 20 rollers, coated and finally wound onto a second roll under tension.
It is known that transverse creases can form in the outer wound layer, for example as a result of brief changes in the winding speed or in the tension, and are included in the roll 25 during further winding. As a result of the action of the tension of subsequent wound layers, this leads to permanent, linear deformations of the tape surface. These may render the relevant roll useless. Since such creasing cannot be completely avoided with the conventional winding means, 30 there is a need for suitable surface testing means for detecting the creases or the linear deformations of the tape-like material which are caused by creasing.
An appropriate optical testing means is disclosed, for example, in U.S. Pat. No. 5,130,555. According to this, a pattern of linear, parallel stripes is projected onto the surface of a continuously moving tape-like material and the line pattern reflected by the surface is electronically evaluated. A crease is detected if the reflected pattern deviates from the original with regard to linearity. The tape crease can then be eliminated by a suitable tape guide means.
This technical procedure is, however, very expensive because, for example, a complex test system comprising video camera, video processor and subsequent electronic 45 data processing is required.
This is true particularly when a plurality of tape strips of the tape-like material are to be tested simultaneously, for example on a longitudinal slitting machine for magnetic information media. It is also possible that very fine linear 50 irregularities will not be detected, owing to the limited optical resolution of the imaging system and the digitizing of the reflected pattern. U.S. Pat. No. 5,357,335 and DE-C 32 12 438, too, are not completely satisfactory with respect to reliable registration of fine, linear irregularities of the tape 55 surface. These documents merely provide optical evidence of large, local layer defects on a coated tape, having, for example, a defect diameter greater than 0.5 mm.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved surface testing means which is simply and economically constructed, has a high probability of detecting fine linear irregularities of the tape surface and is suitable for automatic online inspection of the tape surface. The means 65 should furthermore be just as suitable for the simultaneous testing of a plurality of tape strips as for the inspection of a
single tape strip. We have found that this object is achieved by surface testing means, operated by reflection, for linearly moving, tape-like materials for automatic online registration of linear irregularities (6) transverse to the direction of movement on the tape, comprising:
a) tape guide means consisting of at least two stationary rods (1,1') and intended for stabilizing the tape running along at least one test distance (2), the rod axes being oriented perpendicular to the direction of movement,
b) at least two optical inspection units (3, 3') which scan the same surface of the tape-like material and are assigned to spatially separated test areas of the test distance and each of which contains optical transmitting means (4, 4') and receiving means (5, 5') and
c) at least one electronic circuit arrangement for registering error signals, the individual analog signals Ex and E2 of the receiving means (5, 5') being compared with a first, settable trigger threshold Sj and first error signals F1 or F2 being registered therefrom if Et or E2 exceeds the threshold St, and pairs of individual signals Ej, E2 being tested for coincidence in a coincidence circuit having a settable time window At and, if coincidence is present, second error signals F12 being registered if both coincident individual signals Et and E2 exceed a second, settable trigger threshold S2, S2 being more critical than Sj.
Also included are further advantageous practical embodiments of the invention. A magnetic information medium which is tested by the novel testing means and carries an appropriate identification is also novel. Embodiments of the invention are contained in the description below and in the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,
FIG. la shows a testing means for a single tape according to the present invention.
FIG. lb shows a testing means for two spatially separated tapes (2a, 2b) according to the present invention.
FIG. 2 shows the electronic circuit arrangement belonging to two inspection units (3, 3') according to the present invention.
DETAILED DESCRIPTION OF THE
The invention comprises a suitable test distance (2) of the tape-like material moving continuously in the running direction, which test distance is bounded by at least two stationary tape guide rods (1, 1'), with at least two spatially fixed inspection units (3, 3') which scan the same surface of the tape-like material without contact and at least one electronic circuit arrangement for evaluating the receiver signals (5,5'), and for doing so both as individual signals for registering local defects and in coincidence for registering linear irregularities (6) transverse to the direction of movement. All three components cooperate synergistically, resulting in a considerably increased sensitivity of detection. The use of a microcomputer which gathers the error signals and outputs test documents for each individual tested tape strip is advantageous.
For the purposes of the present invention, the test distance (2) may comprise either only a single web (FIG. la) or at least two separate webs (FIG. lb). In the case of FIG. lb, the webs (2a, 2b) originate from the same original roll and are formed therefrom by longitudinal slitting on a slitting