Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
  • G02B26/10—Scanning systems
  • G02B26/105—Scanning systems with one or more pivoting mirrors or galvano-mirrors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
  • F16D3/00—Yielding couplings, i.e. with means permitting movement between the connected parts during the drive
  • F16D3/80—Yielding couplings, i.e. with means permitting movement between the connected parts during the drive in which a fluid is used
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
  • F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
  • F16F15/023—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using fluid means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
  • F16F15/10—Suppression of vibrations in rotating systems by making use of members moving with the system
  • F16F15/12—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon
  • F16F15/1202—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon the damping action being at least partially controlled by centrifugal masses
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
  • F16F15/10—Suppression of vibrations in rotating systems by making use of members moving with the system
  • F16F15/16—Suppression of vibrations in rotating systems by making use of members moving with the system using a fluid or pasty material
  • F16F15/161—Suppression of vibrations in rotating systems by making use of members moving with the system using a fluid or pasty material characterised by the fluid damping devices, e.g. passages, orifices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F7/00—Vibration-dampers; Shock-absorbers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F7/00—Vibration-dampers; Shock-absorbers
  • F16F7/01—Vibration-dampers; Shock-absorbers using friction between loose particles, e.g. sand
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
  • G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
  • G02B7/182—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors
  • G02B7/1821—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors for mirrors for rotating or oscillating mirrors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F2222/00—Special physical effects, e.g. nature of damping effects
  • F16F2222/04—Friction
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F2222/00—Special physical effects, e.g. nature of damping effects
  • F16F2222/08—Inertia

Definitions

• the present invention generally relates to vibration reduction systems in limited rotation motor systems, and relates in particular to mirrors for use with high speed limited rotation motor systems such as galvanometer scanning systems.
• a mirror is mounted to the output shaft of a limited rotation motor and the limited rotation motor is controlled by a control loop that seeks to cause the rotor of the motor, and therefore the mirror, to follow a position and velocity command waveform with arbitrarily high fidelity.
• the acceleration of the mirror within the system is limited by the rate of rise of current in the motor windings.
• the positional precision is limited by the signal to noise ratio of the feedback method.
• the bandwidth of the system (which is its ability to move from position A to position B at a desired high velocity and to then settle at position B precisely in the shortest possible time), is limited primarily by vibrations in the moving parts. The bandwidth of the system will nominally be Vi the first torsional resonance in the moving structure.
• the invention provides a mirror for use in a limited rotation motor system, wherein the mirror includes a body, an aperture within the body, and a high density material within the aperture.
• the body formed of one or more materials, has an exposed mirror surface and is mountable with the limited rotation motor system for rotation with respect to an axis of mirror rotation.
• the aperture is positioned at least proximate to a portion of the axis of mirror rotation.
• the high density material is provided within the aperture such that it is capable of movement within the aperture, and the high density material has a density that is greater than a density of the material of the body of the mirror.
• the invention provides a scanning system including a limited rotation motor coupled to a mirror.
• the limited rotation motor includes a rotor shaft, and the mirror includes a body and a high density material within an aperture in the body.
• the body includes an exposed mirror surface and is coupled to the rotor shaft for rotation with respect to an axis of mirror rotation.
• the high density material is capable of movement within said aperture with respect to the body of the mirror, and the high density material has a density that is greater than a density of the body of the mirror.
• the invention provides a method of damping vibrations in a scanning system that includes a limited rotation motor including a rotor shaft, and includes a mirror that is coupled to the rotor shaft.
• the method includes the steps of rotating the mirror about an axis of mirror rotation through application of a torque applied to the mirror by the limited rotation motor via the rotor shaft; and accelerating a high density material within the mirror due to vibrations in the movement of the mirror, whereby the acceleration of the high density material within the mirror absorbs energy from the vibrations thereby damping vibrations in the scanning system.
• Figure 1 shows an illustrative diagrammatic view of a mirror in accordance with an embodiment of the invention
• Figure 2 shows an illustrative diagrammatic view of a limited rotation motor system employing the mirror of Figure 1 ;
• Figure 3 shows an illustrative diagrammatic sectional view of the mirror of Figure 1 taken along line 3 - 3 thereof;
• Figures 4A and 4B show illustrative diagrammatic enlarged cross-sectional views of a portion of the mirror of Figure 1 prior to and after a torque motion is applied to the mirror;
• Figure 5 shows an illustrative diagrammatic enlarged cross-sectional view of the top portion of the mirror of Figure 1;
• Figure 6 shows an illustrative diagrammatic enlarged cross-sectional view of a top portion of a mirror in accordance with another embodiment of the invention;
• Figure 7 shows an illustrative diagrammatic enlarged cross-sectional view of a top portion of a mirror in accordance with a further embodiment of the invention.
• Figures 8A - D show illustrative diagrammatic views of target processing variations from an intended target for four scanning step sizes using a system without damping;
• Figures 9A - 9D show illustrative diagrammatic views of target processing variations from the same intended target as in Figures 8A - 8D for four scanning step sizes using a system in accordance with an embodiment of the invention
• Figure 10 shows an illustrative graphical representation of wobble oscillations in a mirror of the prior art following a non-zero acceleration, as well as comparative wobble oscillations in a mirror in accordance with an embodiment of the invention
• Figure 11 shows an illustrative graphical representation of a voltage applied to a limited rotation motor to move a mirror from point A to point B;
• Figure 12 shows an illustrative graphical representation of the associated current in stator windings in a limited rotation motor responsive to the voltage of Figure 11 ;
• Figure 13 shows an illustrative graphical representation of a response of a limited rotation motor system using a damped mirror in accordance with an embodiment of the invention.
• Figure 14 shows an illustrative graphical representation of a response of a limited rotation motor system using an un-damped mirror. The drawings are shown for illustrative purposes only.
• a damped mirror 10 in accordance with an embodiment of the invention includes a reflective surface 12 and a mounting base 14 for coupling to a limited rotation motor system (as further shown in Figure 2).
• the mirror 10 also includes a cylindrical aperture 16 within the body 8 of the mirror 12, and an exposed cap 18 that seals the aperture from the environment.
• the aperture 16 contains high density material that is permitted to move within the aperture 16 of the mirror 10.
• a small diameter hole is drilled either part way or most of the length of the mirror along the nominal axis of rotation to form the aperture 16.
• the diameter of the hole may for example, be between about 100 microns and about 5000 microns, and preferably may be between about 500 and 2000 microns, and more preferably may be about 1000 microns.
• This aperture 16 is filled loosely with high-density particles, preferably made of Tungsten, Depleted Uranium, Molybdenum, Lead, Bismuth, or similar high density material.
• the high-density particles may have a density of greater than about 9.0 g/cm 3 , and in further embodiments, the high density particles may have a density of greater than about 12.0 g/cm J
• the exposed end of the aperture 16 is then closed by the cap 18 to retain the high density material.
• a scanner assembly including a scanner motor 20 having a rotatable rotor coupled to a shaft on which is mounted the mirror 10.
• the scanner assembly also includes a transducer 22 for monitoring the position of the shaft attached to one end of the rotor.
• the mirror 10 and the position transducer 22 may each be attached to the rotor at the same end thereof.
• the system also includes a feedback control system 24 that provides a command signal 26 to the motor 22 responsive to an input command signal from an input node 28 and a feedback signal 30 from the position transducer 22 to control the speed and/or position of the motor.
• the mirror 10 may be coupled to the motor shaft via any of a variety of conventional techniques known to those skilled in the art.
• the motor When the mirror is driven so as to cause a laser beam that is reflected by the surface 12 toward a work-surface to move from a first position (e.g., point A on the work- surface) to a second position (e.g., point B on the work- surface), the motor must first overcome the inertia of the mirror (e.g., from a stand still), rotate the mirror very quickly, and then stop the movement of the mirror very quickly at the second position so that laser processing at point B may begin. Manufacturing variations and imperfections in the mirrors may cause resonances to occur at various frequencies that may cause the positioning of the laser to be compromised.
• the aperture may be filled with damping material comprising high density particles 32, of for example, Tungsten, Depleted Uranium, Molybdenum, Lead and Bismuth, and having a particle size of about 0.1 micron to about 100 microns, and preferably from about 1 micron to 10 microns, and more preferably about 3 microns.
• the body 8 of the mirror 10 may be formed of one or more low density materials such as any of aluminum, steel, glass, semiconductor material such as silicon and/or germanium, carbon, titanium and beryllium as well as combinations thereof.
• the low density body material may have a density of less than about 9.0 g/cm 3 , and in further embodiments, the low density body material may have a density of less than about 5 g/cm 3 . Because the damping material is at or very near the center of rotation of the mirror (A R ), it adds little inertia in spite of its high density. During acceleration of the mirror by the motor, the damping material is shifted away from the center of rotation by centrifugal reaction. When there is no vibration, the material 32 should pack along the walls of the hole 16 in a stable uniform layer, leaving a small area gap along the axis of rotation as shown in Figure 4A.
• the aperture 16 may be filled with the particles 32 such that little or no space exists between the particles 32 and the inner surface of the end cap 18.
• the particles 32 may be packed into the aperture or may settle into the aperture by subjecting the entire mirror 10 to ultrasonic vibration. This prevents the high density material from undergoing too much movement during use that might alter the center of mass of the mirror, which may cause significant imbalances and therefore vibrations.
• an aperture 46 in a body 48 of a mirror may be filed with high-density particulates 50 (such as for example, any of Tungsten, Depleted Uranium, Molybdenum, Lead and Bismuth, and having a particle size of about 0.1 micron to about 100 microns, and preferably from about 1 microns to 5 microns) that are mixed within an elastomeric material 52 and retained by a cap 54.
• high-density particulates 50 such as for example, any of Tungsten, Depleted Uranium, Molybdenum, Lead and Bismuth, and having a particle size of about 0.1 micron to about 100 microns, and preferably from about 1 microns to 5 microns
• the chosen elastomeric material 52 (such as for example, any common elastomeric material such as rubber, silicone, viton, polyurethane and the like serves to retain the particles and acts as a spring to tune the response of the damper to a desired frequency or range of frequencies.
• the mirror may be designed to reduce vibrations at a particular frequency or range of frequencies due to the movement of the particles being limited by the elastomeric material.
• an aperture 66 within a mirror 68 may includes a high-density fluid 70 (such as Mercury), which dissipates the energy as heat in friction with itself and with the walls.
• a high-density fluid 70 such as Mercury
• the high-density fluid may have a density of greater than about 9.0 g/cm 3
• the high-density fluid may have a density of greater than about 12.0 g/cm .
• a cap 72 seals the high density fluid within the aperture such that only a small amount of movement is permitted.
• the distance from point A to point B is the variable, increasing in each step d0 to dl to d2 to d3 to d4.
• the overall size of the scatter map in the x and the y directions respectively is a measure of the error of the system in achieving the desired motion between point A and point B.
• the accelerating current impulse at time t ⁇ causes a vibration in both systems, as discussed in more detail below.
• the vibration dies out before the reverse direction acceleration pulse is applied (as discussed further below with reference to Figure 13).
• the vibration persists (as discussed further below with reference to Figure 14).
• the reverse direction impulse is applied to the un-damped system the impulse adds geometrically with the phase of the original vibration, and is in principle unlimited in amplitude.
• the new amplitude is approximately 10 times the original amplitude, and under these conditions will persist at an obnoxious amplitude for many milliseconds after the end of the position change command pulse.
• Figures 8 A - 8D and 9A - 9D are intended to show that using the same imperfect mirror, both with ( Figures 9A - 9D) and without the additional high density material ( Figures 8 A - 8D), improvements may be obtained in target processing for all step sizes d ⁇ , d.2, d. 3 , and d.4. These drawings are shown for illustrative purposes only.
• Figure 10 shows an illustrative view of wobble oscillations in a prior art mirror as well as a mirror in accordance with an embodiment of the invention.
• a prior art mirror oscillates significantly for more than 0.25 seconds (2.5 x 10 "2 ), and in fact experiences the greatest amplitude of oscillation (as shown at 102) after the motor has stopped (at 0.00).
• a mirror in accordance with an embodiment of the invention begins to reduce the amplitude of oscillations immediately after the motor stops (at 0.00), and significantly reduces the oscillations after only 0.01 seconds (1.00 x 10 "2 ) as shown at 106.
• the damped response of a system of the invention therefore, never reaches the peak amplitude of motion of the un-damped system, and further by 5 x 10 "3 seconds after the end of command the vibration is already below that of the un-damped system at 2.5 x 10 "2 seconds, providing a gain of a factor of 5 in settling time.
• the movement of the mirror due to a control signal to that drives a mirror from a first position (providing a first laser point A) to a second position (providing a second laser point B) is as follows.
• Figure 14 shows movement vibrations of an un-damped mirror on a time scale common with the voltage across the motor, (as shown in Figure 11), current through the motor, (as shown in Figure 12).
• Figure 13 shows the damped response of the system on the same time scale.
• the accelerating current impulse at time ti causes a vibration in both systems as shown in Figures 13 and 14.
• the vibration dies out before the reverse direction acceleration pulse is applied as shown in Figure 13.
• the vibration persists as shown in Figure 14.
• Figure 13 shows that a voltage to a stator of a limited rotation motor is initially increased to a +v voltage and the voltage potential on the stator quickly ramps up to this voltage during time tj to t 2 as shown at 110.
• the voltage is then ceased at time I 2 , and then at time I 3 , a negative voltage is applied to stop the rotor as shown at 112.
• the current ramps up from time t ⁇ to time t 2 as shown at 120, then falls off until time t 3 .
• time I 3 to time I 4 a negative current is applied to stop the movement of the mirror as shown at 122. The current then again falls off until time t 5 when the mirror stops.
• the movement of a damped mirror in accordance with an embodiment of the invention has some initial oscillations (as shown at 130) when the positive current is first applied at time t ls but these oscillations quickly die out long before the negative current (reverse direction acceleration pulse) is applied at time t 3 .
• the mirror has some initial oscillations (as shown at 132) that quickly die out long before the mirror reaches the desired position at time t$.
• the mirror when using an undamped mirror, the mirror has some initial oscillations (as shown at 140) when the positive current is first applied at time tj, but these oscillations do not die out prior to time t3, at which point they are amplified (as shown at 142 and 144). Although these oscillations do reduce prior to time t$, some oscillations remain (as shown at 146), and these oscillations will negatively impact the accuracy of any laser processing that occurs at time t 5 .
• the reverse direction impulse is applied to the un-damped system the impulse adds geometrically with the phase of the original vibration, and is in principle unlimited in amplitude. As shown in Figure 14 the new amplitude is approximately 10 times the original amplitude, and under these conditions the vibration will persist at an obnoxious amplitude for many milliseconds after the end of the position change command pulse.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Acoustics & Sound (AREA)
• Aviation & Aerospace Engineering (AREA)
• Mechanical Optical Scanning Systems (AREA)
• Optical Elements Other Than Lenses (AREA)
• Mounting And Adjusting Of Optical Elements (AREA)

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• 2010
  • 2010-04-21 KR KR1020117024774A patent/KR101757277B1/ko active Active
  • 2010-04-21 CN CN201080018344.5A patent/CN102422195B/zh active Active
  • 2010-04-21 US US12/764,392 patent/US8284470B2/en active Active
  • 2010-04-21 EP EP10719467.2A patent/EP2422234B1/en active Active
  • 2010-04-21 JP JP2012507343A patent/JP5693564B2/ja not_active Expired - Fee Related
  • 2010-04-21 WO PCT/US2010/031875 patent/WO2010123977A1/en not_active Ceased

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