Electro-optical scanning system with gyrating scan head

What is claimed is:

1. An optical scanning system comprising:

a light source;

a gyrating scan head;

an optical element coupled to said gyrating scan head for receiving light from said light source and directing light toward a target; and

a photoelectric converter for receiving light from a target and producing electrical signals which are responsive to received light.

2. An optical scanning system according to claim 1, wherein said light source is a laser.

3. An optical scanning system according to claim 1, wherein said gyrating scan head produces gyrations of said optical element having components of motion in two perpendicular directions.

4. An optical scanning system according to claim 1, further including a scan head controller for controlling the motion of said scan head.

5. An optical scanning system according to claim 4, wherein said scan head controller comprises a waveform generator.

6. An optical scanning system according to claim 1, further including a motor coupled to said scan head for rotating said scan head.

7. An optical scanning system according to claim 6, further including a motor controller for controlling the rotation of said motor.

8. An optical scanning system according to claim 1, wherein said light source, scan head, optical element, and photoelectric converter comprise an optical data acquisition system which further includes a communication system for interchanging information between said data acquisition system and a remote location.

9. An optical scanning system according to claim 8, wherein said communication system is a wireless communication system.

10. An optical scanning system according to claim 9, wherein said wireless communication system is an ultrasonic communication system.

11. An optical scanning system according to claim 9, wherein said wireless communication system is an infrared communication system.

12. An optical scanning system according to claim 9, wherein said wireless communication system is a radio frequency communication system.

13. An optical scanning system according to claim 8, further comprising a data processing system in said remote location for receiving and processing optical scanning information from said communication system.

14. An optical scanning system according to claim 13, wherein said data processing system includes means for communicating control information to said data acquisition system via said communication system.

15. An optical scanning system according to claim 8, wherein said communication system includes an electrical or optical cable.

16. An optical scanning system according to claim 1, further comprising a battery for supplying power to said system.

17. An optical scanning system according to claim 1, further comprising beam shaping means for directing light from said source to provide a spot or narrow beam of light in the direction of said target.

18. An optical scanning system according to claim 17, wherein said beam shaping means produces a narrow beam of light near said scanning system, which beam rapidly diverges beyond a certain distance from said scanning system.

19. An optical scanning system according to claim 18, wherein said beam shaping means comprises a conical lens.

20. An optical scanning system according to claim 18, wherein said beam shaping means comprises a hologram.

21. An optical scanning system according to claim 17, wherein said beam shaping means comprises a movable optical element.

22. An optical scanning system according to claim 21, wherein said beam shaping means comprises an electrically focusable lens.

23. An optical scanning system according to claim 22, wherein said beam shaping means comprises a positive lens, a resilient lens suspension permitting axial movement of said lens, a coil, and a magnetic circuit coupled to said suspension for producing axial movement of said lens in response to a change in current in said coil.

24. An optical scanning system according to claim 1, further comprising a light collector for concentrating light from a target on said photoelectric converter.

25. An optical scanning system according to claim 24, wherein said light collector concentrates light by total internal reflection within a transparent solid medium.

26. An optical scanning system according to claim 25, wherein said transparent solid medium is transparent primarily at wavelengths of light emitted by said source.

27. An optical scanning system according to claim 25, wherein said light collector comprises a truncated cylindrical shell.

28. An optical scanning system according to claim 27, wherein said cylindrical shell includes an end face having the shape of a portion of a toroid.

29. An optical scanning system according to claim 1, further including a housing in which said source, scan head, optical element, and photoelectric converter are disposed.

30. An optical scanning system according to claim 29, wherein said housing is dimensioned so as to be hand holdable.

31. An optical scanning system according to claim 30, wherein said housing is generally cylindrical.

32. An optical scanning system according to claim 30, wherein said housing has a generally cylindrical shape and directs a scanning light beam generally along the axis of said cylinder.

33. An optical scanning system according to claim 30, wherein said housing includes a switch for initiating operation of said scanning system.

34. An optical scanning system according to claim 33, wherein said switch provides both intermittent and continuous operation of said scanning system.

35. An optical scanning system according to claim 29, wherein said system includes means in said housing for wireless interchange of scanning information with apparatus at a remote location.

36. An optical scanning system according to claim 29, wherein said housing comprises means for mounting said system to a ceiling above an area to be scanned.

37. An optical scanning system according to claim 29, wherein said housing is mounted to a flexible goose-neck member.

38. An optical scanning system according to claim 1, further including means for actuating said scanning system.

39. An optical scanning system according to claim 38, wherein said actuating means includes means for automatically detecting the presence of objects in a target area and actuating said scanning system in response to such detection.

40. A method of optically scanning a target comprising the steps of:

mounting a moveable member to a fixed member at a pair of locations defining an axis;

mounting an optical element to said moveable member;

directing a beam of light at said optical element, whereby the light beam is redirected by said optical element toward a target area; and

moving said moveable member with respect to said fixed member so that points on said moveable member have a component of motion in a first plane including said axis, whereby said optical element is moved by said moveable member and said redirected beam provides a scanning beam in said target area.

41. A method according to claim 40, wherein said moving step includes moving said moveable member with respect to said fixed member so that points on said moving member also have a component of motion, in a second plane which includes said axis and is perpendicular to said first plane.

42. A method according to claim 40, further comprising the step of rotating said fixed member, thereby rotating said moveable member, said optical element, and said scanning beam.

43. A method according to claim 40, wherein said moving step includes applying an electromagnetic force between said fixed member and said moveable member.

44. A method according to claim 43, wherein said electromagnetic force applying step includes applying an electrical waveform to a coil secured to said fixed member or to said moveable member.

45. A method according to claim 40, further comprising the step of shaping said beam of light.

46. A method according to claim 45, wherein said light beam shaping step provides a light beam which is narrow over a certain distance near said optical element and which rapidly diverges beyond said certain distance.

47. A method according to claim 46, wherein said light beam shaping step includes passing said light beam through a conical lens.

48. A method according to claim 46, wherein said light beam shaping step includes passing said light beam through a hologram.

49. A method according to claim 45, wherein said light beam shaping step includes passing said light beam through a focusable lens and focusing said lens.

50. A method according to claim 40, further including the steps of:

receiving light from said target field including any reflections of said light beam from a target in said target field, and

converting the received light into electrical signals responsive to said received light.

51. A method according to claim 50, wherein said light receiving step is performed in a substantially annular area surrounding said redirected beam.

52. A method according to claim 50, further including the step of concentrating received light in a nonimaging collector.

53. A method according to claim 52, wherein said concentrating step includes totally internally reflecting received light in a transparent solid medium.

54. A method according to claim 53, further including the step of filtering received light in said transparent solid medium.

55. A method according to claim 50, further including the step of transmitting said electrical signals to a remote location.

56. A method according to claim 40, wherein said component of motion comprises an arc centered at a point on said axis.

57. An optical scanning system comprising:

a scan head having a fixed member, a moveable member mounted at a pair of locations to said fixed member for movement with respect to said fixed member from an equilibrium position, said locations defining at said equilibrium position an axis, and means for inducing an oscillating motion of said moveable member from said equilibrium position with respect to said fixed member, said oscillating motion having a component of motion in a first plane which includes said axis;

an optical element coupled to said moveable member for movement therewith;

a light source for directing a light beam at said optical element, whereby said optical element redirects said light beam toward a target area and provides a scanning beam in the target area in response to movement of said optical element; and

means for receiving light from said target area and for producing electrical signals which are responsive to the received light.

58. A system according to claim 57, wherein said oscillating motion also has a component in a second plane which includes said axis and is perpendicular to said first plane.

59. A system according to claim 57, further including a motor having a shaft coupled to said scan head for rotation thereof.

60. A system according to claim 57 wherein said oscillating motion inducing means includes an electromagnetic motor coupled to said fixed member and to said moveable member.

61. A system according to claim 57, further including means disposed in the path of said light beam for shaping said light beam to provide a light beam which is narrow over a certain distance near said system and which rapidly diverges beyond said certain distance.

62. A system according to claim 61, wherein said light beam shaping means includes a conical lens.

63. A system according to claim 61, wherein said light beam shaping means includes a hologram.

64. A system according to claim 57, further including an electrically focusable lens disposed in the path of said light beam.

65. A system according to claim 57, wherein said light receiving means includes a nonimaging light collector.

Description Submit all comments and votes

FIELD OF THE INVENTION

The present invention relates to providing a means of scanning a light beam in one or more dimensions to read information from the field scanned and to methods of scanning, detecting, and reading information, including barcode, alphanumeric code and pattern recognition.

More particularly the invention relates to a scanning device which is useful where it is desirable to cover an area with high density scan patterns which may be rotated in order to read information therein without having to first orient the material to be read.

In various embodiments the invention is useful in factory, point of sale, and hand held applications as a component in information gathering equipment and systems. Barcode scanning, reading and decoding of printed codes and other information, and pattern recognition are a few of the useful applications of this invention. It is particularly suited where low cost, compactness, ease of mounting, and light weight are desired.

BACKGROUND OF THE INVENTION

The field of beam scanning for the purpose of gathering information is rapidly advancing. The commercial application and importance of barcode reading is well known and is now becoming more sophisticated with the introduction of two dimensional barcodes. Code 49 is only one example of a new barcode standard that contains information in a two dimensional array. As information density increases, scanning with high speed dense scan patterns becomes necessary in order to read it rapidly.

In addition to barcode reading, the ability to read alphanumeric information is also of great commercial value. Other types of encoded information are being devised, and object recognition requiring scanning readout equipment is also of commercial importance.

The problem of having to orient barcodes with respect to the barcode reading equipment at merchandise check out counters is well known. However, automatic information reading is required in many areas where it may not be convenient for humans to orient the information to be read. Conveyor lines where barcode labels on airline luggage must be read is such an example. Besides the fixed mount scanners found on conveyor lines and under the counter point of sale terminals, portable hand held barcode scanners are also popular today. One common portable scanner which is packaged as a wand of about one half inch in diameter contains a light emitting diode (LED) and photo detector (PD). A hard transparent spherical tip is brought into contact with the barcode to be scanned and smoothly passed across the code. Light transmitted through the spherical tip from the LED is reflected off the bar code creating a modulated reflection which is transmitted back through the tip whereupon it is detected by the PD, and processed as information. The shortcomings of this system are that it requires direct contact with the code, mutual orientation of the code and direction of the stroke across all bars of the code, and a relatively non jerky pass.

Another type of portable scanner uses a laser instead of an LED in order to project a narrow light beam a considerable distance ranging from a few inches to a few feet. In this type of scanner some means of uniformly sweeping the light beam is provided, usually by reflecting it off a moving mirror. Inexpensive small motors have been adapted to oscillate or rotate such mirrors creating a scan in essentially a straight line. Stepper motors have been quite popular for this function but they are prone to causing the beam to move in a jerky fashion (non linear motion). Non linear scanning produces poor decode results.

Some of the best portable laser scanners can read information at distances of several yards and are useful for reading barcode labels where they are out of reach. But again these labels may be affixed with random orientations requiring the user of the scanning equipment to carefully orient and aim the scanner to successfully read them.

In order to read these forms of information it is beneficial to rapidly scan a light beam over the information to be read and at the same time to cover the scan area with a dense scan pattern consisting of many closely spaced scan lines. A scan line typically consists of a fast moving laser generated spot. By scanning at many different angles simultaneously or in rapid succession, the probability of successfully reading randomly oriented coded information is improved so much that the process requires no tedious aiming.

In general, in order to derive information from a scanned object, light is directed at the object, and scanned across it at a known rate. As this light is reflected or scattered back by the object, its intensity will vary when observed from a particular vantage point. This scattered light coming back from the object is essentially amplitude modulated by the absorption and reflection from the surface of the object and thus contains spatial information about the object. This information bearing signal may be detected and decoded or interpreted based upon the known direction and velocity of the scanned spot.

Numerous patents describe methods of generating multiple scan lines of various orientations and kinds but none are known for generating these with only one single optical component such as a mirror and only one moving part. Moreover, most devices for generating scan patterns are best suited for making only one type of pattern and major design modifications are required to make different scan patterns. Furthermore none of the known methods of generating high speed multiple scan lines at significant scan angles achieve this result with a single self-contained miniature low profile component which may be mounted simply with the only alignment required being to reflect a beam off its mirror.

Although some devices use mirrors mounted on a spinning motor as a component to generate beam motion, none are as compact and amenable to packaging in spaces as small as the present invention, nor are any known to be capable of generating such sophisticated scan functions as spinning rasters or spinning lissajous figures for example.

Other scan devices may use numerous holograms on a plate which mimic lenses of various focal lengths to focus a beam at different distances thereby increasing the depth of field of the scanner. At the same time the plate is rotated by a motor which causes the beam to scan. U.S. Pat. No. 4,794,237 describes such a device. U.S. Pat. No. 4,639,070 describes a plurality of rotating holograms, mirrors, prisms and gear systems to achieve scans at various angles and rotations. Separate designs with different multiple combinations of these parts are required to produce different patterns.

In U.S. Pat. No. 4,387,297 individual stepper type motors are used with mirrors attached to their shafts and positioned orthogonally so a laser beam reflects off each mirror in succession making possible the production of a raster pattern or lissajous figures, but these cannot be rotated unless the whole product is rotated.

U.S. Pat. No. 4,797,551 describes a method for producing nine fixed scan lines arranged in groups of three parallel lines at three different angles, but the optical system is complex with many mirrors all carefully aligned with many parts and it is so bulky that it would not be practical for hand held applications.

U.S. Pat. No. 4,041,322 describes the generation of polyphase patterns that look like sinusoidial waves all phase shifted with respect to one another. But this also requires multiple mirrors mounted on a spinning polygon as well as an oscillating mirror. This device cannot rotate the scan patterns nor is it portable enough for convenient hand held applications or mounting in tight spaces.

U.S. Pat. No. 4,794,237 describes a multidirectional holographic scanner which can produce scan lines at many angles. This however requires as many as five mirrors and numerous holograms all mounted on a disk which is rotated by a motor.

U.S. Pat. No. 4,409,469 describes a scanning device which includes a mirror mounted on a wedge. The wedge is spun by a motor causing a beam reflected from it to reflect off multiple mirrors mounted in a circle around the spinning mirror.

None of the known two dimensional scan devices can generate multiple scan lines at different orientations with only one mirror, none are single component items, none have a great palette of possible scan patterns while at the same time are practical to mount in a thin tubular housing small enough to be held in a person's hand and none have a single beam shaping device capable of producing a scanning spot of essentially the same small size over great distances.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a means of electronically controlling the orientation of scan patterns rather than orienting the target material which may be bulky and randomly presented.

It is another object of this invention to move the scanning spot with great consistency, that is, without jerking it and at a uniform speed or at least at a speed that is very predictable.

It is yet another object of this invention to achieve multiline or omnidirectional scanning action by means of as few component parts as possible.

It is a further object of the invention to provide a means of generating omnidirectional scanning capability with only one single optical scan component such as a mirror set in motion by only one small moving device which may be made as a single component.

Another object of this invention is to provide a very compact reading device, which may be housed in a thin flashlight style housing while providing for sophisticated high speed omnidirectional scan capabilities heretofore found only in large nonportable equipment.

Another object is to do away with the need for dangling wires and cables from the equipment thereby making it easier to handle or install.

Yet another object of this invention is to provide a miniature low mass high speed scanning device, capable of scanning wide angles in one or more dimensions with independent control.

It is a further object of this invention to provide a means of generating oscillating scan lines by a device which has intrinsically long life by eliminating bearings in the device.

In accordance with the foregoing objects, the scanning system of the present invention include one or more of the following: a novel gyrating scanning head which can produce linear or multidirectional scanning patterns from a single fixed light source using a single optical element; a novel light concentrator which concentrates light by means of total internal reflection in a solid transparent medium; an electronically focusable light source; a light beam shaping device which produces a narrow beam near the scanning device and a rapidly diverging beam far from the scanning source; and a communication system for communicating scanning information from the scanner to a remote location. Such scanning systems are mountable in small hand-holdable flashlight-style housings, or at fixed locations near the area to be scanned. Other objects and features of the invention will become apparent upon review of the drawings, the following description thereof, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of the principal component of a scanning system.

FIG. 2 is an exploded view of a first embodiment of a scan head according to the present invention.

FIG. 3 is an illustration of a coil and core showing the gyrating motion produced by the scan heads of the present invention.

FIG. 4 is a more detailed exploded view of the first embodiment of the invention, illustrating the core suspension in greater detail.

FIG. 5 is an exploded view of a second embodiment of a scan head according to the present invention, which permits gyration in two perpendicular directions.

FIG. 6 illustrates a scan head according to the invention which is mounted to a motor for producing rotating scan patterns.

FIG. 7 illustrates a scan head according to the invention which is adapted for fixed mounting and which includes a modified suspension.

FIG. 8 illustrates a scan head according to the present invention which incorporates a modified suspension and which is adapted to be mounted to a motor shaft for rotation.

FIG. 9 is a partially cut away view of a scanning system according to the present invention mounted in a flashlight-style housing.

FIG. 10a is an illustration of person using a hand-held scanner in accordance with the present invention in order to scan randomly oriented information.

FIG. 10b is a cutaway view of a self powered hand-held scanner with means for wireless communication of scanned information to a remote location.

FIG. 10c is a partially cutaway view of a hand-held scanner which receives power from and communicates scanned information to a remote location over a cable.

FIG. 11a is a partially cutaway perspective view of a light collector in accordance with the present invention.

FIG. 11b is an illustration of a scanning system including the novel light collector of FIG. 11a.

FIG. 12a illustrates a first scan pattern which may be produced by a scanning system in accordance with the present invention.

FIG. 12b illustrates a second scan pattern which may be produced by a scanning system in accordance with the present invention.

FIG. 12c illustrates a third scan pattern which may be produced by a scanning system in accordance with the present invention.

FIG. 12d illustrates a fourth scan pattern which may be produced by a scanning system in accordance with the present invention.

FIG. 12e illustrates a fifth scan pattern which may be produced by a scanning system in accordance with the present invention.

FIG. 12f illustrates a sixth scan pattern which may be produced by a scanning system in accordance with the present invention.

FIG. 13 illustrates a means of flexibly mounting a scan head.

FIG. 14 illustrates a point of sale system utilizing a ceiling mounted scanning system.

FIG. 15 illustrates a beam shaping system for producing a narrow beam near the scanner which rapidly diverges beyond a certain distance from the scanner.

FIG. 16 is a cross-section of an electrical focusing system.

FIG. 17 is a schematic diagram illustrating the general features of a gyrating scan head according to the present invention.

FIG. 18a illustrates a first suspension spring which may be used in the scan heads of the present invention.

FIG. 18b illustrates a second suspension spring which may be used in the scan heads of the present invention.

FIG. 18c illustrates a third suspension spring which may be used in the scan heads of the present invention.

FIG. 19 is an exploded illustration of a third gyrating scan head according to the present invention which uses a gyrating coil.

FIG. 20 is an exploded illustration of a fourth embodiment of a scan head according to the present invention, which uses a gyrating coil and a magnetic frame.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic drawing of the principal components of a scanning system according to the invention. As illustrated, the system includes into an optical scanning data acquisition system 11 which communicates acquired data via a communication channel to a data processing system 19, which processes the acquired data as required by the application. These subsystems may be physically integrated or separated; for instance, certain point of sale systems use a self contained system under a checkout counter, whereas other such systems include a hand-held data acquisition system coupled by a cable to a point of sale terminal.

The data acquisition system 11 includes a light source such as a semiconductor laser 13 powered by laser power supply 17. The light source produces a light beam which is shaped and focused in an optical system 10. The focus of optical system 10 may be varied by control element 18, for instance to automatically focus the beam. The shaped beam from the focus element 10 is directed at an optical element such as a mirror 9 which redirects the beam 27 toward the target area located at 12. The beam is shaped and focused by the optical system 10 so that the spot is of sufficiently small diameter where it encounters the target to be scanned in order to resolve the information therein. The position and motion of mirror 9 are controlled by a device typically referred to as a "scan head" to produce the desired scan pattern of beam 27 at location 12. Scan head 14 is powered by a scan head power supply and control unit 7, which typically includes a waveform generator. Aperture 25 may be provided to clip unwanted nonlinear fringes of the scan pattern. The scan head power supply and control unit 7 may produce more than one set of independent waveforms in order to drive the scan head 14 to produce motion of the mirror in independent dimensions making possible the generation of desirable two dimensional scan patterns. A motor 24 mechanically coupled to scan head 14 and electrically coupled to motor power supply and control unit 8 may be provided in order to permit orientation or rotation of the scan head 14 and thereby to position, rotate and/or dither the scan pattern produced by the system. Light from the target area is supplied to a photoelectric converter which converts the light signals into electrical signals of a desired form for further processing. In FIG. 1, the photoelectric converter comprises light detector 3, amplifier 4, digitizer 5, and buffer 20. A light detector 3 such as a photo diode transforms the collected light into electrical signals which are typically amplified by amplifier 4 and then digitized by the digitizer 5, making them suitable for digital processing. A signal buffer 20 may be used to store information from the digitizer 5 so that it may be transmitted at a suitable rate to an information processing device 16 such as a computer in data processing system

A light collector or concentrator 1 may be provided to collect and concentrate the diffusely reflected light from the scanned target at 12 on the light detector 3, and the collected light typically passes through a filter 2 to, remove unwanted ambient and stray light not of the wavelength produced by the light source 13. The light collector 1 may be constructed so that it is made from a material that filters the diffusely reflected information bearing light signal, thereby eliminating the need for a physically separate filter component.

FIG. 1 shows two alternatives which may be used to transmit information between the data acquisition and the data processing portions of the scanning system. One alternative is a solid or closed communication channel 29, such as a cable comprising electrical conductors or fiber optics. Such a channel may be used, together with any necessary signal conversion electronics, where an electrical or optical cable between the data processing system 19 and the optical data acquisition system 11 is not a substantial disadvantage. In many circumstances, however, it will be desirable to have a portable or otherwise remote data acquisition system 11 communicate by wireless means with a data processing system 19. To facilitate such communication, transmitters 6 and 23 may communicate with receivers 15 and 22 over an RF, infrared, ultrasonic, or other such wireless communication channel.

A controller 21 may be provided to control the elements of the scanning data acquisition system such as by turning the laser power supply 18 on and off, adjusting the focus of the optical system 10, controlling the motor drive 8 and the scan drive 7. Controller 21 may also receive information from data processing system 19 via receiver 22 in order to initiate, continue and stop the scanning sequence.

FIG. 17 is a schematic diagram illustrating the general features of a gyrating scanning component or scan head in accordance with several embodiments of the present invention. The scan head is adapted to move an optical element 524 so that an incident beam directed at the optical element from a fixed light source is redirected to provide a positionable spot or a moving spot, i.e. a scan line, in a target area. Typically, optical element 524 is a flat mirror but it may also include other types of reflective elements or refractive elements. An electromagnetic source 504 is provided, which is mechanically coupled to a frame 500 by a suspension comprising suspension members 514 and 516 and by mounting members 506 and 508 affixed to source 504. As used herein, an electromagnetic source is a device producing an electric and/or magnetic field and which is capable of interacting with an electric and/or magnetic field produced by another device so as to provide a force between such devices. Such sources include permanent magnets and conductors such as coils which carry a current. Mounting members 506 and 508 may be separate physical components or may be fabricated as integral parts of source 504. Source 504 and mounting members 506 and 508 form an assembly 502, which may be referred to herein as a gyrating member or gyrator because of its motion as described below, and which may be referred to in specific embodiments as a core assembly when electromagnetic source 504 is embodied as a magnetic core.

Suspension members 514 and 516 are coupled to gyrating member 502 at mounting points or locations 510 and 512, respectively. Mounting points 510 and 512 define an axis labelled the Z axis in FIG. 17. Suspension members 514 and 516 suspend gyrator 502 so that the Z axis has a particular orientation with respect to frame 500 in the absence of electromagnetic force upon source 504, i.e. an equilibrium orientation and an equilibrium positioning of mounting points 510 and 512. At least one of the suspension members, member 516, is resilient; that is, if mounting point 512 is displaced from its equilibrium position, suspension member 516 provides a restoring force urging mounting point 512 toward its equilibrium position. Suspension member 514 may maintain mounting point 510 fixed at its equilibrium position, or may be resilient as described above with respect to suspension member 516. Thus suspension members 514 and 516 permit core assembly 502, or at least a portion thereof, to move in at least one direction perpendicular to the Z axis, for instance in the X or Y directions indicated. Such movement is in an arc about some center of rotation on the Z axis, which center is determined by the suspension. For instance, if suspension member 514 maintains mounting point 510 fixed with respect to frame 500, all points other than 510 on or rigidly coupled to core assembly 502 will move in arcs centered on mounting point 510. If suspensions 514 and 516 are equally resilient, all points on gyrating member 502 may move in arcs centered at a point midway between mounting locations 510 and 512. For points on the Z axis, such motion is perpendicular to the Z axis and has components in the X and/or Y directions indicated. Such motion in an arc about a point on the Z axis is referred to herein as "gyration", a member undergoing such movement is referred to as a "gyrator", and the Z axis is referred to as the axis of gyration of the gyrator. Such gyrating motion is to be distinguished herein from rotation about the Z axis. As will be seen, several embodiments of the invention also provide or permit