SUTURE INSPECTION AND GAUGING SYSTEM

Abstract: The process of detecting faults in filamentary suture materials, such as braided polyglycolic acid and other synthetic polymer suture materials, is automated to allow an operator to continuously select upper and lower limits of acceptable suture diameters as well as frayed material with the assistance, if desired, of both an audible alarm and appropriate electronic pulses responsive to deviations from specified limits. A projected silhouette (34), obtained by coherent illumination (22) of continuously fed suture mate­ rial (12), is measured as it falls upon a self-scanned array of photosensitive detector elements (32) from which an output is received sequentially from adjacent detectors and where each output level is proportional to illumination of the corresponding detector in the array. A single output signal can be used to indicate the presence of a fault. In addition, three individual outputs, one each for each type of suture fault, for example, oversize, undersize and frayed material, may be utilized. The system may also include signals which provide continuous suture size information and the informa­ tion may be updated rapidly, such as 1000 times per second, enabling high suture feed rates.

Description: BACKGROUND OF THE INVENTION This invention relates to the inspection and gauging of surgical suture material and, particularly, to a method and system for monitoring the diameter of continuously moving braided surgical suture filamentary material and identifying and locating flaws, such as frays, in the material during the manufacturing process. Current inspection of filamentary suture material, such as braided polyglycolic acid yarn which is to be made into sutures such of the type sold under the trademark Dexon, is carried out using a combination of machine testing and manual inspection. Thus, gross defects in suture material are presently ascertained by apparatus relying upon interupted illumination and an out of specification sensor followed by running the braided material through the fingers of inspectors to determine minor defects. Such procedures are time consuming and labor intensive. Neverthless, suture manufacture requires quality control inspection of the product and could benefit from a fully automated inspection method and system including continuous feed of suture material through an inspection station and a highly reliable means of recognizing faulty material. The testing of opaque work pieces utilizing a light source projecting a beam of light on the work piece to generate a shadow image, projection of the image and beam on a screen where photoelectric sensors can compare characteristics of the shadow image and generate output signals to measure differences in dimensions or orientation are known in the art. U.S. Patent No. 3,851,180 discloses an apparatus for measuring the diameter of a fine wire of 100 microns wherein parallel laser beams are projected upon the wire to form a Fraunhofer diffraction image. The spacing between the peak bright spots of the diffraction image is counted, an optical filter makes the signal level equal to that of a predetermined number of diffractions while a photoelectric transducer, responsive to signals, and appropriate circuits and counters determine the distance between the centers of two signals enabling measurement of the wire diameter. U.S. Patent No. 3,947,129 discloses an apparatus for measuring the diameter of a moving wire in which the wire is illuminated by a light beam which then passes through a cylindrical lens and a slit aperture for projection of the wire contours on an optoelectrical member, such as a photodiode array combined with read out electronic devices, to obtain signals to trigger a fault indicator if dimensions of the wire depart in either direction from certain pre-specified values. The light source can be a lamp emitting visible light or a radiation source emitting ultra-violet or infrared light. U.S. Patent No. 4,171,161 discloses a method and apparatus to test individual elongated opaque work pieces with respect to orientation, size and material integrity in which a light source, preferably an electric flashtube, generates a beam of light which is collimated. A work piece to be tested is placed in the beam to generate a shadow image projected on a screen, with intervening optical enlargement, in which photoelectric sensors are located. Outputs from the sensors are compared with each other or a reference to determine relative shadow image characteristics and hence the properties to be measured. U.S. Patent No. 4,260,260 discloses a process and apparatus for checking the dimensions of manufactured parts by projecting the profile of the part, by illumination with a parallel beam, on an optical receiver including protoelectric cells. The part is continuously moved perpendicular to the beam and the areas of the illuminated surfaces of the cells are measured and compared with reference values to enable determination of the dimension. Methods and systems of the above described type, while perhaps suitable for the specific parts discussed as being measured, are not the most advantageous for inspection and gauging of filamentary braided suture material. For example, only extremely small diameter wires yield useful Fraunhofer diffraction patterns and systems relying thereon would not be applicable to suture thickness filaments. Other systems do not truly gauge but merely measure out-of-specification conditions. Yet..others, when applied to rapidly moving filaments, are susceptible to vibrations because of the limited detectors employed and the light sources utilized. Thus, there exists a need for a fully automated suture inspection method and system which can be utilized in the manufacturing environment and includes the ability to feed suture material continuously through an inspection station with recognition or marking of faulty segments for quality control. SUMMARY OF THE INVENTION The present invention provides a method and system by which the process of detecting faults in filamentary suture materials, such as braided polyglycolic acid and other synthetic polymer suture materials, is automated to allow an operator to continuously select upper and lower limits of acceptable suture diameters as well as frayed material with the assistance, if desired, of both an audible alarm and appropriate electronic pulses responsive to deviations from specified limits. The foregoing is achieved, according to the invention, through the provision of a method and system which measures a projected silhouette, obtained by coherent illumination of the suture material, as it falls upon a selfscanned array of photosensitive detector elements from which an output is received sequentially from adjacent detectors and where each output level is proportional to illumination of the corresponding detector in the array. Thus, an object of the present invention is the provision of a method and system for automatically inspecting filamentary material, such as suture material, continuously for the determination of deviation from predetermined dimensions and the ascertainment of faults. The method and system of the invention may utilize a single output signal indicating the presence of a fault. In addition, three individual outputs, one each for each type of suture fault, for example, oversize, undersize and frayed material, may be utilized. The system may also include signals which provide continuous suture size information. The information may be updated rapidly, such as 1000 times per second, enabling high suture feed rates. The suture product is continuously transported past the source of illumination and its silhouette projected, through an optical system, on the detector. The detector is scanned rapidly, such as in 0.5 milliseconds with another 0.5 milliseconds used to determine whether the suture segment scanned is acceptable. Thus, a further object of this invention is the provision of a method and system providing suture inspection, fault enumeration and continuous, nearly instantaneous, suture gauging. The system of the present invention meets the important criteria desirable for suture inspection. The suture material is illuminated in a manner such that the irradiance falling upon the detector array is sufficient to overcome ambient light in a manufacturing facility and provide a contrast between the suture and background. The system is relatively insensitive to motion perpendicular to the optical axis, an important advantage that eliminates the drawbacks normally associated with vibrations occuring during continuous monitoring of a moving material, and the magnification is easily adjustable. The assembly of components utilized in the system is sturdy and durable and well suited for use in a manufacturing environment. Accordingly, yet a further object of this invention is the provision of a system for inspecting continuously moving filamentary material which is capable of use in a manufacturing environment by providing the necessary illumination, ease of projection and optical stability. The foregoing and other objects, features and advantages of the invention will be further apparent from the following description thereof, taken with reference to the drawings, and the claims appended hereto. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic illustration of a suture inspection and gauging system according to an embodiment of the invention; FIGURE 2 is a side view, partly in section, of a detail of the system of FIGURE 1 illustrating the illumination of the suture and its projected silhouette on the detector array; and FIGURE 3 is a block diagram schematically illustrating the functional electronics of a suture inspection and gauging method and system according to an embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGURE 1, there is shown a suture inspection and gauging system indicated generally at 10. The filamentary material 12, in this case braided synthetic polymer material which has been melt spun, is fed from a pay out spool 14 under and over guide rollers 16 to a take up spool 18. As the suture material 12 is continuously fed from the pay out spool 14 to the take up spool 18 it is illuminated by a beam of coherent light, referred to at 20, which is produced by a helium neon laser 22* The laser 22 produces a narrow beam of collimated monochromatic light which passes through the lens 26 by which it is focused to the point 28 from whence it diverges away from the focal line. The diverging beam 30 is intercepted by a multi-element detector array 32, As illustrated in greater detail in FIGURE 2, the filamentary suture material 12, shown there as being comprised of individual fibers in braided form, passes between the laser light source 22 and the lens 26. As a result, the suture material 12 blocks some of the collimated laser radiation 20 from reaching the lens 28. Be cause the laser source emits parallel rays of light, as shown, the suture 12 projects a silhouette, referred to at 24, on the lens 28 which in turn projects it on the multielement detector array 32 which is mounted on the board 36. The magnification of the silhouette, on the multi-element detector array 32, indicated generally at 34, changes with position, Thus, as the detector board 36 holding the multi-element detector array 32 is moved away from the focal point 28 of the lens 26 the silhouette 34 of the suture 12 becomes larger. Consequently, the magnification is a linear function of position and is adjusted without the need to change lenses. Yet, it is important to note that the distance between the suture 12 and the lens 26 need not be maintained and that even if the suture were closer to or farther from the lens 26, its silhouette, 24 will be projected faithfully on the lens, A similar effect exists on the image side of the optics with the silhouette of the suture remaining well defined regardless of the position of the plane of the detector board 36* Thus neither suture-to-lens nor lens-to-detector board distances need be maintained to achieve high levels of accuracy making the system particularly adapted for convenient use in a manufacturing environment. The laser may advantageously be a 0,5 milliwatt laser operating at 632.8 nm. The lens 26 may advantageously be a 25 mm focal length standard Cannon T.V. lens. The lens 26 may also comprise a system of lenses. A product silhouette magnified to a size of approximately 50 percent of the height of the detector array 32 has proven satisfactory. The desired durability and required optical stability may be obtained by mounting the components on carriages, such as those available under the designation X-95, from Klinger Scientific Corp,, Jamaica New York, which in turn are mounted on rails from the same source. The multi-element detector array 32 is a photodiode array, such as that available under the designation EG & G RL-128G from Reticon, Division of E.G. & G, Inc., Sunnyvale, California, mounted on an evaluation board available from the same source under the designation RC301. Such an array is comprised of a series of 128 light sensors, each less than 0.001 inch in width, mounted on 0.0Q1 inches centers. All of the 128 detector chips are deposited on a single silicon substrate and take up a total of 1/8 inch in length. When the detector array 32 is appropriately energized, a video-like signal is available on one of the detector chip pins (not illustrated). On this pin appears successively a voltage proportional to the amount of light falling on the successive detector elements. This continues for approximately 0.5 m sec, during which time each of the 128 elements has its signal multiplexed to an output pin. After a pause of 0.5 m sec, the process is repeated. Although the signal from each element is only a microsecond in duration, all of the irradiation falling upon the detector array 32 is sensed because silicon photodiodes integrate the light over the interval between samplings. The system electronics referred to generally at 40 in FIGURE 1 represents the provision of various functions including the supply of power to the detector array 32 and to displays in integrated circuits described in greater detail below. In addition, the block 40 represents the electronics used to examine the video signals generated by the detector array 32. These include an adjustable threshold Schmitt trigger circuit to convert the analog video signal to a digitized light-present/lightabsent signal, circuits to determine how many elements of the detector array are blocked from receiving light by the suture 12 being inspected, that is, a determination of the suture silhouette 34, and a display to indicate the count of the same, circuitry to compare suture size to pre-selectable upper and lower limits as well as circuitry to detect a fray in the suture. In addition, in order to provide meaningful data to an operator, the electronics may include an electrical voltage level change from 0 volts to +5 volts when a defect is sensed and an audible alarm, capable of being turned off, to indicate a defect, electrical outputs for each type of defect such as undersize, oversize or fray and a display to indicate the presence of a fray. A schematic illustration, in functional block form, of the electronics represented by block 40 is illustrated in FIGURE 3. The multi-element detector array 32, previously discussed, generates a video signal 42 which is taken by the analog comparator 44 which compares the magnitude of the video signal voltage with the magnitude of the voltage of a signal 45 from a threshold adjust 46. The output generated by the analog comparator 44 is a binary video signal 48. This signal is high in those instances when the video signal voltage is higher than the threshold signal voltage from the threshold adjust 46. At all other times the binary video signal voltage is low. The multi-element detector array 32 utilizes a clock signal 50 from the clock 52 to determine the timing of the video signal 42. Also available from the detector array 32 is a start-of-scan signal 54 and an end-of-scan signal 56. A counter 58 counts pulses 60 from the clock 52 when the binary video signal 42 is low and only between the start-of-scan signal 54 and the end-of-scan signal 56. After the end-of-scan signal 56, a count display 62 and digital comparators 64 and 66 are enabled for a period of time which ends prior to the next start of scan signal 54. The upper limit of acceptable counts is sent via an upper limit adjust 68 and the lower limit is set via a lower limit adjust 70. If the count exceeds the upper limit or is below the lower limit, the comparator 64 or 66, as appropriate, respectively will indicate an exceeded limit. Anon gate 72 provides, as an output, a flow signal 74 which is indicative of out of specification suture material. A third counter 76 enumerates the number of times that the signal 65 from the upper level limit comparator 64 goes positive. A fourth counter 78 enumerates the number of times that the signal 67 from the lower limit comparator 66 goes positive. The count can be considered indicative of suture width and displayed, as is known, on a panel for an operator to visually scan the digits to determine if the readings are within limits. At 1000 times per second counts it is necessary for comparators to test the three digit number for upper and lower limits, which limits may be selected by the operator with appropriate thumb wheel or other switches which may also be mounted on an operations panel. In most instances, a fray in the suture material will yield an increased count and thereby by indicative of an oversized area of the suture. It is also possible for a suture to part in such a way as to leave the total measured width within limits but to have this total made up of two parts. Such a condition may be sensed by counting the number of +5 volt to 0 volt transitions of the video envelope. Such a two component measurement is deemed a fray and is rejected. The flaw signal from the OR gate 72 may be used to indicate a fault regardless of its source. An audible alarm-may be wired into the system, as is known in the art, such that a short high frequency tone may sound at the time when a faulty segment passes through the suture in spection and gauging system. The alarm can be operator disabled. A visual display, such as a standard output connector mounted on a panel to indicate a voltage level change from 0 to 5 volts occuring at the instant of fault detection, may be provided. The individual electronic components themselves are standard elements commercially availably and their assembly with the required circuitry is known to those skilled in-the art and need not be further described. While the inspection and gauging system has been described with particular reference to suture material, it should be understood that it is applicable to similar filamentary products.

Claims: CLAIMS: 1. A system (12) for continuously inspecting and gauging filamentary suture material characterized by a source of coherent illumination (22), means (14,16) to feed the suture material (12) past the source of coherent illumination, an array of photosensitive detector elements (32) positioned with respect to the illumination source and suture material to receive a projected silhouette (34) therefrom, means to self-scan the detector array to generate output signals (42) sequentially from adjacent detectors at a level proportional to illumination of the corresponding detector in the array, means (44) to compare the detector generated illiininaticn levels with preselected values, and output signal means to signal results of the comparison as indicative of suture characteristics. 2. A system for continuously inspecting and gauging filamentary suture material as claimed in Claim 1 wherein the illumination level comparison means is characterized by a comparator (44) which generates a binary signal (48) and the output-signal means is characterized by a clock means (52) to dictate pulse timing of the binary signal and counter means (58) to count the binary signal pulses. 3. A system for continuously inspecting and gauging filamentary suture material as claimed in Claim 1 wherein the means for providing the preselected values of illumination level is characterized by a threshold adjust (46). 4. A system for continuously inspecting and gauging filamentary suture material as claimed in Claim 2 wherein the counter means is characterized by a plurality of counters (76,78,58) to indicate, sequentially, the number of times count limits are exceeded for upper limit and lower limits as well as the presence of a low count. 5. A system for continuously inspecting and gauging filamentary suture material as claimed in Claims 1 or 4 further characterized by means to provide a visual display (621 or aural alarm indicative of the output signal 6. A system for continuously inspecting and gauging filamentary suture material characterized by a light source means (22) for providing a narrow beam of collimated monochromatic light, an array of photosensitive detector elements (32) positioned to receive the beam of light on its surface, means (14,16) to feed filamentary suture material past the light source and between the light source and detector array, means (26) to project a silhouette of the suture material on the detector array, each of the detector elements generating a scanning proportional to the light falling therein, threshold adjust means (46) for selecting illumination level values, and analog comparator means (44) for receiving and comparing the generated illumination levels with the preselected values and generating a voltage output signal in relation thereto. 7. A system for continously inspecting and gauging filamentary suture material as claimed in Claim 6 further characterized by a clock means (52) to determine the pulse timing of the output signals, counter means (76, 78) to count the pulses and digital comparator means (64, 66) to indicate an exceeded limit relating to suture material characteristics. 8. A system for continuously inspecting and gauging filamentary suture material as claimed in Claims 6 or 7 wherein the counter means is further characterized by counter means (58) to count voltage transitions in the analog comparator means and indicate a count greater than two to indicate the presence of a fray in the suture material. 9. A method for continuously inspecting and gauging filamentary suture material characterized by illuminating filamentary suture material with coherent illumination to provide a silhouette, projecting the silhouette on an array of photosensitive detector elements, self-scanning the detector array to generate output signals sequentially from adjacent detectors at levels proportional to the illumination of the corresponding detector, and comparing the generated illumination levels with preselected values to provide an indication of the suture material characteristics. 10. A method for continuously inspecting and gauging filamentary suture material as claimed in Claim 9 further characterized by generating an output signal, by counting pulses generated by signals obtained by comparing the illumination levels, of at least three signals each indicative of an undersize suture material, an oversize suture material or a fray in the suture material.

Inventors: ZOLTAN, BART JOSEPH
Applicants: AMERICAN CYANAMID COMPANY
Application year: 1983
Main classification: G01B11
IPC codes: G01B11