Abstract:
A light-emitting apparatus, such as a laser pointer, for enabling a spot of light to be projected on a desired target located a distance away such that the spot is projected on the desired target without any or substantially any undesired movement. The apparatus may include a housing, a light generating device located within the housing and operable to generate a beam of light, a sensing device or devices for sensing an undesired action of the housing, a control circuit operable to provide a control signal corresponding to the sensed undesired action, and a drive device operable to counter act all or at least some of the undesired action of said housing in accordance with said control signal.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to light-emitting devices and particularly to those devices intended to produce a beam in a selected direction such as toward a target of interest. The invention provides motion-compensation technology suitable for use with such light-emitting devices, which may dampen and/or substantially eliminate the effect of unintentional motion, vibration, or movements, such as angular movements, caused by mechanical vibrations, hand tremors, and so forth.  
         [0002]     Light-emitting devices, such as laser diode devices, are used in a variety of consumer, computer, business, medical, scientific, military, outdoor, telecommunication and industrial products, including but not limited to compact disk (CD) players and computer CD-ROM drives, digital video disk (DVD) players and DVD-ROM drives, laser printers, laser pointers, barcode scanners, measurement devices, rangefinders, scopes, industrial material processing devices, marking and cutting systems, medical equipment, fiber optic transmission systems, satellite communications, and digital printing presses. Many of these applications require precision accuracy for successful implementation. However, conventional light-emitting devices may be affected by unintentional angular movements (e.g., fine vibrations from the machine in which a laser is encased, fine tremors from a shaking hand holding a laser, etc.) and, as a result, generate an unsteady column of light—producing an effect that may cause inferior performance.  
         [0003]     There are known in the art devices for example binoculars and cameras that contain lenses designed to capture a wide spectrum of light and focus them on the eyes of a user in a manner that eliminates the appearance of motion to the user. However, the present invention is directed to solving a different and more challenging problem. Specifically, these known devices work to eliminate the movement or shake of a user&#39;s hands by selective focusing of the beam of the received light, this light emanates a wide angle of sources and is collected by the lenses. During collection of the wide angle of received light, the beam is focused so that it appears to not to shake when the user views an object through the binoculars. In contrast, a light emitting apparatus presents a unique problem because a light emitting device has a known and relatively narrow point source of light. The point source of light must be controlled in a manner to ensure that the light beam impacts on the desired target some distance away from the point source despite movements of the point source.  
         [0004]     An example of the above mentioned effect will now be described with reference to a laser pointer. Fine tremors of the human hand, when holding even a lightweight laser pointer (or other pointing device), have been measured at a frequency range of 1 to 5 Hz. These unwanted vibrations are often amplified when the person maneuvering the device is nervous. The resulting deviation of the projected spot from the intended target point to the actual point is proportional to the distance from the pointing device to the target object (e.g., a point on a screen). This deviation may be approximately equal to the product of the sine or the tangent of the angle and the distance to the projected spot. In other words, for small angular movements (such as less than 10 degrees), the movement of the projected spot is approximately equal to the product of the distance to the target and the angle of the movement (in radians). For instance, small angular movements of +/−1 degree of a laser pointing device may result in movements of approximately +/−2 cm of the projected spot on a target 1 meter away; and, these angular movements will result in a 10-fold larger projected spot movement (approximately +/−20 cm) for a target 10 meters away (which may be typical of large lecture halls). In contrast to angular movements, translational movements (sideways movements of the hand) are not amplified by the distance from the light-emitting device to the target object. That is, if the hand holding a laser pointer is moved sideways by 1 cm, the spot on the target is also moved sideways by 1 cm irrespective of how far the target is from the hand. Thus, only the angular changes (particularly those in the 1 to 5 Hz frequency region, typical for a hand tremor) cause the undesirable movements of the projected light on the target.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention provides a motion-compensating light-emitting apparatus which enables a steady beam of light to be projected onto a desired target even if subjected to undesired unsteady conditions by automatically redirecting or compensating for unintentional, off-target angular movements. The present apparatus may use miniature gyroscopes and/or accelerometers and/or other sensing type devices and an optical system including light-refracting elements arranged within the apparatus.  
         [0006]     The present apparatus may be lightweight, portable, compact, inexpensive to manufacture and easy to assemble.  
         [0007]     In one embodiment of the present invention, a motion-compensating light-emitting device is provided which utilizes two miniature gyroscopes (for example, microelectromechanical system (“MEMS”) such as model ADXRS150 manufactured by Analog Devices, Inc.) arranged to measure vertical and horizontal angular movements (i.e., pitch and yaw) of the device. These gyros may have a relatively small volume (such as less than 0.15 cm 3 ), low weight (such as less than 500 mg), and small size (such as 7 mm×7 mm×3 mm or less).  
         [0008]     In another embodiment of the present invention, a motion-compensating light-emitting device is provided which utilizes two or three miniature accelerometers (for example, MEMS, such as model ADXL203 manufactured by Analog Devices, Inc) arranged to measure acceleration and changes of the gravity vector (changes in acceleration) or relative tilts with respect to the vertical axis in two orthogonal directions (i.e., yaw and pitch) and to obtain from this information the relative vertical and horizontal angular movements. These accelerometers may have a relatively small volume 0.05 cm 3  (with dimensions of 0.5 cm×0.5 cm×0.2 cm). Additionally, the accelerometers may be provided in a hermetically sealed package.  
         [0009]     In the present invention, the sensing device(s) (such as the two gyros or accelerometers) may be arranged so as to interact with an optical apparatus to cause the exiting light rays to be refracted in a compensating or opposite direction to a measured undesired angular movement or motion. For instance, if one of the gyros measures a downward tilt or undesired angular movement of the light-emitting device, then the light rays may be refracted in a proportional amount in the upward direction so as to cancel the effects of the undesired angular movement or vibration. As is to be appreciated, a similar result may also be obtained for undesired angular movements or motions in the left and/or right direction.  
         [0010]     In the present invention, the compensating refraction may be accomplished by manipulating or sliding one or more miniature lenses into the light rays before they exit the device. In this regard, as light rays encounter the lens or lenses, they are refracted wherein the exit vergence is a function of the angle of incidence with the respective lens, the thickness and radius of curvature of such lens, and the various indices of refraction through which the light passes.  
         [0011]     As an alternative to the above-described movable lens or lenses, two plates, which may be fabricated from glass or an equivalent type material, may be joined or arranged with a bellows and the space between the plates filled with a transparent liquid having a desired refractive index. Such arrangement may serve to refract the light rays. Here, instead of sliding a lens, the bellows may be contracted or expanded to change the angle of refraction of the light rays.  
         [0012]     Another embodiment of the instant invention is a light-emitting apparatus using a magnetic compensator to compensate for undesired movement so that a beam of light is projected on a target substantially without any undesired movement. The apparatus includes a light generator, a movement sensor for detecting the undesired movement, and a controller. The controller provides a control signal corresponding to the sensed undesired movement to the magnetic compensator. The magnetic compensator preferably includes one or more permanent magnets and one or more electrical coils, the controlled interaction thereof compensating for the sensed undesired movement and maintaining the location of the beam of light.  
         [0013]     Yet a further aspect of the present invention is a laser pointer or light-emitting apparatus that enables a spot of light to be projected on a desired target. The pointer includes a housing, a light generator located within the housing, and sensor for sensing an undesired movement of the housing. The laser pointer also includes a controller which generates a control signal corresponding to the sensed undesired movement and provides this control signal to a magnetic compensator. The magnetic compensator counteracts the undesired movement of the housing so that the spot is projected on the desired target without any undesired movement.  
         [0014]     Yet another aspect of the instant invention is a light-emitting apparatus. The apparatus includes a light generator for generating a beam of light and a sensor for detecting any undesired movement of the apparatus. The apparatus also includes a controller which provides a control signal corresponding to the sensed undesired action to a compensator. The compensator compensates for the undesired movement of the apparatus to counter act the undesired movement of the apparatus. The compensator includes at least two mirrors and a driver which positions the at least two mirrors so as to compensate for the undesired movement. The driver moves the mirrors in response to the control signal so that the beam of light is projected on a desired target without any or substantially any undesired movement.  
         [0015]     The circuitry utilized to drive the lens, bellows, magnetic compensator, or mirror may be relatively simple. For example, two inverting amplifiers may be arranged to amplify the analog outputs from the MEMS gyros which may be used to form a drive signal for causing the lens, the bellows, the magnetic compensator, or the mirror to be moved in the appropriate direction. It should be noted that while MEMS gyros are described, use of accelerometers or other appropriate movement sensors would be equally applicable and are considered within the scope of the present invention. The present invention is described in more complete detail below with reference being made to the drawing figures, which are also identified below and in which corresponding components are identified by the same reference numerals. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a diagram of a motion-compensating light-emitting apparatus according to an embodiment of the present invention;  
         [0017]      FIG. 2  is a diagram of the motion-compensating light-emitting apparatus of  FIG. 1  to which reference is made in explaining the operation thereof;  
         [0018]      FIG. 3  is a diagram of a motion-compensating light-emitting apparatus according to another embodiment of the present invention;  
         [0019]      FIG. 4  is a diagram of the motion-compensating light-emitting apparatus of  FIG. 3  to which reference is made in explaining the operation thereof;  
         [0020]      FIG. 5  is a diagram to which reference is made in explaining the operation of one aspect of the present invention;  
         [0021]      FIG. 6  is a diagram of a motion-compensating light-emitting apparatus according to another embodiment of the present invention;  
         [0022]      FIG. 7  is a diagram of a motion-compensating light-emitting apparatus according to another embodiment of the present invention;  
         [0023]      FIG. 8  is a diagram of the motion-compensating light-emitting apparatus of  FIG. 7  to which reference is made in explaining the operation thereof;  
         [0024]      FIG. 9  is a diagram of a motion-compensating light-emitting apparatus according to another embodiment of the present invention; and  
         [0025]      FIG. 10  is a diagram of the motion-compensating light-emitting apparatus of  FIG. 9  to which reference will be made in explaining the operation thereof. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]      FIG. 1  is a diagram of a laser diode pointer  100  which includes vibration or motion compensation circuitry in accordance with an embodiment of the invention. A visible laser diode  110 , or other appropriate light-emitting element, is used as the light source. There are several ways of implementing the vibration compensation scheme. In accordance with an embodiment of the invention, two angular velocity sensors (gyros)  120  and  125  are aligned in orthogonal directions and used to measure the angular movements in the pitch and yaw axis (also referred to as the X and Y axis). The output of gyros  120  and  125  are amplified by two amplifiers  131  and  132  respectively and/or sampled by an A/D converter  133  in anti-vibration control circuit  130 . The sampled signal is preferably passed to a band frequency filter  134  where the portion of the signal associated with the rapid, unwanted angular motions of the pointer in this example, typically that portion between 1 and 5 Hz, is extracted. Although a band frequency filter having a range of 1 to 5 Hz is described, a variable frequency filter may be used to set the desired band of frequencies. The range of frequencies may be adjusted by utilizing an adjustment type device such as a variable resistor or digital switches.  
         [0027]     The filtered signal is then integrated by an integrating processor circuit  135 . Because gyros  120  and  125  measure angular velocity, the signal received by integrating processor circuit  135  is integrated to obtain angular information from which an angular difference may be obtained. Although the embodiment of  FIG. 1  utilizes gyros  120  and  125  that measure angular velocity, gyros  120  and  125  may measure an angular difference. In such instance, integrating processor circuit  135  need not be included in the anti-vibration control circuit  130 .  
         [0028]     The integrated rate output or angular difference (proportional to the angle of the unwanted angular motion) is conditioned by a correction amount normalization circuit  136  (which may include amplifying the signal by a necessary or predetermined amount) and supplied as an input for motors  140  and  150 , which are connected to a movable lens  160  (which is located between the laser diode  110  and a focusing lens  170 ). Movable lens  160  and focusing lens  170  are each preferably constructed from one or more convex lenses and/or concave lenses, or a combination of convex and concave lenses, or one or more convex/concave type lenses, or any combination thereof. The signals are conditioned so that the feedback loops provide an input signal to the motion correction mechanisms such that the resulting circuits are stable in the region of interest. The conditioning may include adjusting the gain of the signal as well as adjusting for the null of the circuit and the zero offset of the gyros. Thus, if the integrated rate output measured is equal to 1 degree, the amplified signal has to equal a voltage (or current) that will produce a motor movement required to move the compensating lens for a one degree of motion.  
         [0029]     The anti-vibration control circuit  130  may be part of a microprocessor or microcomputer, or could be constructed out of individual analog and digital elements depending on the cost, size and power consumption of each implementation. Additionally, an on/off switch may be provided in laser diode pointer  100  which may enable a user to turn off the anti-vibration control circuit if the user does not want to use the motion compensating function.  
         [0030]      FIG. 2  is a diagram of a laser diode pointer  100  when it is tilted down. The gyros  120  and  125  measure the angular velocity of the tilt, and their output signals (which may be in analog form) are proportional to the angular rate of the motion. Such signals are then preferably amplified, digitized and passed to the band pass frequency filter  134 . The band frequency filter  134  extracts the portion of the signal(s) associated with rapid unwanted angular motion (e.g. unwanted hand tremors which may be in the 1 to 5 Hz range). The filtered signals are then integrated by the integrating processor circuit  135 . The normalizing and conditioning circuit  136  receives the integrated signal and, in accordance therewith, generates a voltage or current signal having a value or magnitude corresponding to the necessary compensation, and cause the same to be supplied to compensating element(s) (such as motors  140  and  150 ). In response thereto, the motors  140  and  150  cause the corrective lens  160  to move in a direction such that an exiting beam continues to exit the laser pointer  100  in a horizontal or a substantially horizontal direction. Without the movement of this corrective movable lens  160  the beam would exit at a downward angle. The motors  140  and  150  may alternatively comprise an electro-motor, an electro-magnetic motor, a piezo-electric motor or any other type of actuator suited for this application.  
         [0031]     Although not shown in this diagram, laser pointer  100  (which includes the gyros and the anti-vibration circuit) is preferably powered by a power source such as two 1.5V batteries connected in series as used for ordinary laser pointers. To save on power usage, the motion-compensation technology may be activated only upon activation of the laser pointer.  
         [0032]     Although  FIG. 2  depicts a laser diode pointer  100  tilted on one axis and its resulting compensation, tilting on the other axis would be compensated similarly (and independently) and is not illustrated in order to keep the drawings simple and easy to follow.  
         [0033]     In another embodiment of the invention, and as shown in  FIG. 3 , a laser diode pointer  200  employs a movable bellows  210  filled with a high refractive index solution or material  220  instead of corrective movable lens  160 . The refractive index of the high refractive index solution or material  220  is preferably approximately 1.33 or higher. The high refractive index solution or material  220  may be stored between two sheets of glass  230  and  240  such that the portion of the high refractive index solution in the path of the optical beam is adjusted (by squeezing or spreading the bellows) based on the angular rates measured by the two angular velocity sensors or gyros  120  and  125 . Instead of moving an optical lens to change the direction of the exiting beam the bellows filled with high refractive index solution may be contracted on one end and expanded on the other end so as to bend the exiting light beam in a direction opposite to the unwanted motion.  FIG. 4  shows how such a change in the thickness or arrangement of the bellows causes the beam to bend so as to compensate for the unwanted motion. As in the previously described laser pointer having a movable lens, the laser pointer  200  may be powered by a power source such as a number of batteries arranged in a predetermined manner. Additionally,  FIGS. 3 and 4  indicate how motion in the pitch or X axis is compensated; however, motion in the yaw or Y axis are compensated for similarly (and independently) and is not illustrated in order to keep the drawings simple and easy to follow.  
         [0034]      FIG. 5  is a flow chart describing how a laser pointer in accordance with an embodiment of the present invention compensates for unwanted motion. The process starts in step S 100  where the laser pointer is turned on by pressing a button or the like. During operation of the laser pointer, a sensing means, which may include gyros or accelerometers or a combination thereof, measures movement and output a signal which is processed by the anti-vibration control circuit. Such processing includes the analog to digital conversion performed by the A/D converter  133 . Processing then proceeds to step S 120  wherein the signal is supplied through a band pass filter so as to effectively detect and extract signals corresponding to the unwanted motion of the laser pointer (unwanted motion may be in the 1 to 5 Hz range). If the sensing means does not detect unwanted motion, and therefore the inquiry at step  120  is answered in the negative, the method proceeds to step S 130  where the correcting lens or bellows is not moved and the beam exits the laser pointer with out any redirection. If there is unwanted motion detected by the sensing means and therefore the inquiry at step  120  is answered in the affirmative, the method proceeds to step S 140  where the processed signal is integrated and/or amplified. A voltage or current corresponding to the processed and/or amplified signal is applied to the drive motors in step S 150 , which in turn, move the prism or the bellows in step S 160 . In step S 170 , the beam is redirected in the direction opposite the direction of the hand tremor.  
         [0035]      FIG. 6  is a diagram of another embodiment of the laser diode pointer  300  wherein accelerometers are utilized instead of gyroscopes. Three angular velocity sensors (accelerometers)  310 ,  320 , and  330 , which are aligned in orthogonal directions, measure the angular movements in the pitch, yaw and roll axis (also referred to as the X, Y and Z axis) respectively. The output of accelerometers  310 ,  320 , and  330  are respectively amplified by three amplifiers  340 ,  350 , and  360 , and then sampled by A/D converter  133  in the anti-vibration control circuit  330 . The portion of the signal associated with rapid unwanted angular motions of the pointer (e.g., an unwanted hand tremor in the 1-5 Hz range) is extracted by band pass filter  134  and integrated by integrating processor circuit  135 . Movements (tilts) of the laser pointer are measured by comparing the measured acceleration to a gravity vector (g acceleration) as the laser pointer is tilting and/or computing the motions from the three orthogonal measurements of the acceleration.  
         [0036]     The computed integrated rate output from the integrating processor circuit  135 , which is typically proportional to the angle of the unwanted angular motion may be conditioned, including for example amplifying the signal by a necessary or predetermined amount, and/or used as the input for motors  140  and  150  coupled to movable lens  160  and located between the laser diode  110  and the focusing lens  170 . The anti-vibration circuit  330  may be included in a microprocessor or microcomputer or may be constructed out of individual analog and/or digital elements depending on the cost, size and power consumption requirements.  
         [0037]     In another embodiment of the present invention, instead of using only a compensating device in front of the light emitting device, the light emitting device itself can be made to tilt in opposite direction to the undesired angular movement that is measured by the gyros or accelerometers. Thus, the light emitting device (such as a laser diode) is anchored in the center of a two axis gimbaled configuration. Movement of the gimbaled light emitting device is accomplished by means of two electro-coils (or two motors) that are now part of the light emitting device system. Two permanent magnets placed on both sides as well as above and below the light emitting device (four (4) magnets in total) form the complete system enabling a tilt of the light emitting device when current flows through the coils. In this configuration a current in one direction through the coils causes a tilt of the light emitting device to one side (e.g., up) while a current in the opposite direction through the coil causes a tilt of the electro coil to the other side (e.g., down).  
         [0038]     In all embodiments, an optical system such as lenses, bellows or mirrors may be used to further refract the light as it exits the device.  
         [0039]      FIG. 7  is a diagram of a further embodiment of a motion compensating light emitting device constructed in accordance with the invention. In this example a visible laser diode  110  is used as the light source. Two angular velocity sensors (gyros)  120  and  125  aligned in orthogonal directions are used to measure the angular movements in the pitch and yaw axis (also referred to as the X and Y axis). The output of these gyros is amplified by two amplifiers  131  and  132  and then sampled by an A/D converter  133  in the anti vibration control circuit  130 . The frequency portion of the signal, which is associated with rapid unwanted angular motions of the pointer in this example, is then integrated by an integrating processor  135  and produces an integrated rate output. The integrated rate output (proportional to the angle of the unwanted angular motion) is then conditioned (amplified by the required amount) and used as the input for the two electro coils  220  that are wound around the laser diode module  110 . The interconnection of the integrating circuit  135  and the electrical coils  220  is not shown in  FIG. 7 . There are four permanent magnets  210 ,  211 ,  230 , and  231  situated to the left, right, up and down positions around the laser diode module. In this example the up and down magnets  230  and  231  are in front of the laser diode module  110  where the laser beam exits while the left and right magnets  210  and  211  are behind the exiting beam area of laser diode module  110 . These magnets cause the electro-coils  220  to deflect the laser diode module  110  when current is allowed to flow through the electro-coils  220 . Current through an electro-coil causes the formation of a magnetic field and if the magnetic field is of opposite polarity of the nearby permanent magnet then the laser diode module  110  will deflect as the magnetized portions try to move closer to each other. The laser diode module  110  is mounted with one or more mechanical springs  200  connected to the laser diode housing  180  so that without any electrical current to the electro-coils the laser diode module  110  is not deflected to either side or up and down.  
         [0040]      FIG. 8  shows the effect on the light emitting device of  FIG. 7  when, for example, rapid motion of a hand tremor causes the light emitting device to tilt down. The gyros  120  and  125  measure the angular velocity of the tilt and their (analog) output is proportional to the angular rate of the motion. The signal is then amplified, digitized and if the angular motion (tilting up) is very rapid caused for example by an unwanted tremor in the 1-5 Hz range, the signal is then passed through the high frequency filter  134  and integrated by the integrating circuit  135 . The normalizing and conditioning circuit  136  then sends a signal to the electro-coil drivers  141  and  151  to move the laser diode module  110 , as shown in  FIG. 8  this is movement in the direction of the positive magnet  230 , so that the exiting beam continues in a horizontal direction even though the housing  180  was tilted downward by the unwanted hand tremor. Without the movement of this corrective motion, caused by the attraction of the magnetized coil to the magnet, the beam would exit at a downward angle.  
         [0041]     One of skill in the art will appreciate that  FIGS. 7 and 8  are simplified drawings and do not depict certain features such as for example the power supply connections to the gyros and the anti-vibration circuit. As an example, for use in a handheld laser pointer, a power supply may consist of two 1.5V batteries connected in series as used for ordinary laser pointers, to power the laser diodes.  
         [0042]     The forgoing examples indicate how motion in one axis, here the Y axis or pitch which is in the plane of the paper is measured and compensated. However, the invention is not so limited and motion in the X axis or Yaw can also be compensated by the present invention.  
         [0043]      FIG. 9  depicts another embodiment of a motion compensating light emitting device, with motion compensation accomplished by a system employing movable mirrors. Vibration compensation can also be accomplished by means of MEMS micro-mirrors where single axis (or two axis) beam steering can be accomplished using surface micro-machined technology. Recent developments in this area have produced 2 axis micro-mirrors where two orthogonal motions in one device are achieved over angles greater than 10 degrees making such a motion compensation device very compact, using very simple circuitry and very little power. (An example of such devices can be found at Aksyuk V. A. et al., Optical Fiber Conference OFC 2002 Post Deadline Paper1).  
         [0044]     In accordance with one embodiment of the invention a visible laser diode module  110  is used as the light source. A vibration compensation technique, in accordance with the invention, employing two angular velocity sensors gyros  120  and  125  are aligned in orthogonal directions and are used to measure the angular movements in the pitch and yaw axis (also referred to as the X and Y axis, respectively). One of skill in the art will readily appreciate that although described here in conjunction with MEMS gyros, accelerometers can also be used instead of gyros, further, the use of other appropriate movement sensors are also considered within the scope of the instant invention. The output of these gyros  120  and  125  is amplified by two amplifiers  131  and  132  and sampled by an A/D converter  133  in the anti-vibration control circuit  130 . The frequency portion of the signal (associated with rapid unwanted angular motions of the pointer in this example) is then integrated by an integrating processor. This integrated rate output, which is preferably proportional to the angle of the unwanted angular motion is then conditioned by the correction amount normalization circuit  136 , amplified by a predetermined amount and used as the input for the two mirrors drivers  142  and  152  that drive the two movable mirrors  230  and  240 . Mirror motion can be accompanied by means of electromechanical devices such as those commonly used for vibrating galvanometric mirrors. In this arrangement a small mirror  240  is mounted on the axis of an electro-motor. If current is applied to the windings of the motor, the motor will turn thus causing the mirror to rotate and change the deflection of the incident beam.  
         [0045]     Vibration compensation occurs as shown in  FIG. 10 , where a light emitting device, for example a laser pointer is tilted down. The gyros  120  and  125  measure the angular velocity of the tilt and their (analog) output is proportional to the angular rate of the motion. The signal is then amplified by amplifiers  131  and  132 , digitized by and A/D converter  133  and if the angular motion is very rapid, as for example caused by an unwanted tremor in the 1-5 Hz range, the signal is then passed through the high frequency filter  134  and integrated by the integrating circuit  135 . The normalizing and conditioning circuit  136  then sends a signal to the motor  142  and  152  to move the mirrors  230  and  240 . The mirrors  230  and  240  are attached to the shafts of the motors  142  and  152  and rotate in their respective directions so that the first reflected beam continues in a vertical direction, and the second reflected beam continues in a horizontal direction even though the laser diode  110  was tilted downward by the unwanted hand tremor. Though discussed herein with respect to compensation for movement in the Y direction, the present invention is not so limited and may be used to compensate for movement in the X, Y, and Z directions.  
         [0046]     Although the above embodiments describe laser pointers that may utilize specific combinations of gyroscopes or accelerometers, the present invention is not so limited. For example, the present invention may also utilize other types of sensing devices or may utilize a different number of gyroscopes or accelerometers or may utilize a combination of gyroscopes and accelerometers to sense unwanted motion. Further, although preferred embodiments of the present invention and modifications thereof have been described in detail herein, it is to be understood that this invention is not limited to those precise embodiments and modifications, and that other modifications and variations may be effected by one skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.