Abstract:
A mechanical nanomover for optical elements alignment comprises a platform; a front supporting block and a rear supporting block; a left metal sheet and a right metal sheet installed between the two supporting blocks; a movable block installed between the two metal sheets; a weak spring and a strong spring which are interacted with the movable block. A translation stage serves to drive the weak spring to drive the movable block. The elastic coefficient of the strong spring is much greater than that of the weak spring so that the larger displacement of the weak spring will induce only a small displacement of the movable block due to the interaction of the strong spring. No electric power is needed to drive the structure of the nanomover. The mechanical nanometer can provide a sufficient precision to the operation, while it is very inexpensive.

Description:
FIELD OF THE INVENTION 
     The present invention relates to alignment of optical elements; and particularly to a mechanical nanomover for optical elements alignment; in that no electric power is needed to drive the nanomover of the present invention. The moving extent of a weak spring is so large so that the user&#39;s hand is sufficient to control a movable block to move only a small sub-micrometer displacement so that the mechanical nanomover of the present invention can provide a sufficient precision to the operation, while it is very cost effective. 
     BACKGROUND OF THE INVENTION 
     A nanomover is a device serving to move an object through a very small range, such as several sub-micrometers, or several nanometers, which is especially used in the alignment of optical elements. 
     With the growth in the optical communication and many other optical applications, optical elements alignment has become the focus of much industrial attention. This is a key production process because the connection efficiency of the optical elements greatly influences the overall production rates and the quality of the connected optical elements for the products used in optical communication. 
     For example, optical fiber alignment is necessary when two optical fibers are connected, when an optical fiber is connected to a photo diode or a light emission diode and when an optical fiber array is connected to an optical wave guide. 
     Metallic wire connection is relatively easy because an electric current will flow as long as the two wires are in contact. The connection between two optical elements, such as optical fibers, however, requires much greater precision, in the order of sub-micro-meters. Therefore, experienced technicians are needed for optical elements alignment, but as such technicians are limited in supply, this causes a bottleneck to the mass production of components for optical communications. 
     Automatic alignment system can shift slightly the light axes of two optical elements, such as optical fibers to minimize transmission loss. Once alignment is complete, the light axes are fixed by laser processing or a setting resin.  FIG. 10  shows the organization of the typical alignment system. The system consists of a light source, alignment stages, a stage controller, a power meter to measure the light intensity, and a controlling PC. The alignment stage moves the tip of one optical fiber with sub-micrometer precision using step motors. The PC controller receives information from the power meter and feedbacks the information to the stage controller to control the alignment stage. The control signals are generated by the PC where the alignment is executed. 
     In above structure, the step motor can be replaced by a piezoelectric element which can convert electric energy into mechanic action so as to drive the clamp arm with a V groove locating an optical fiber. 
     Above mentioned structures are driven electrically and can achieve a desired precision for moving the clamp arm with a minor distance in sub-micrometer ranges. However this device is very expensive and must be driven electrically. Thus, there is an eager demand for a novel design which can improve the above mentioned disadvantages. 
     SUMMARY OF THE INVENTION 
     Accordingly, the primary object of the present invention is to provide a mechanical nanomover for optical elements alignment; in this device, no electric power is needed to drive the structure of the nanomover. The moving extent of a weak spring is so large so that the user&#39;s hand is sufficient to control a movable block to only move through a small displacement. Thus the mechanical nanomover can provide a sufficient precision to the operation, while it is very cost effective. 
     To achieve above objects, the present invention provides a mechanical nanomover for optical elements alignment which comprises a platform; a front supporting block and a rear supporting block placed upon the platform; a left metal sheet and a right metal sheet installed between the two supporting blocks; a movable block installed between the two metal sheets; a weak spring and a strong spring which are interacted with the movable block. A translation stage serves to drive the weak spring to drive the movable block. Other than the front supporting block and the rear supporting block, all the elements are located not to contact the platform so as to provide a frictionless system in operation. The elastic coefficient of the strong spring is much greater than that of the weak spring so that the larger displacement of the weak spring will induce only a small displacement of the movable block due to the interaction of the strong spring. The mechanical nanomover can provide a sufficient precision to the operation, while it is very cheap. 
     In the present invention, the weak spring  601  is an elastic reed and the strong spring  602  is another elastic reed. Furthermore, the driving unit  700  is a translation stage which has an axle; one end of the axle is connected to the weak spring and another end of the axle is threaded to a casing of the translation stage. The front supporting block  201  and the rear supporting block  202  are rigid bodies. 
     Moreover, in the present invention, a preload is added to the moveable block. In an assembly state, the strong spring is compressed with a very little extent so as to apply a predetermined preload to the moveable block and thus the right metal sheet  301  and left metal sheet  302  will also deform with the same extent experienced by the moveable block  400 . 
     The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view showing the elements of the present invention in the first embodiment of the present invention. 
         FIG. 2  shows an assembly view of the present invention. 
         FIG. 3  is a partial perspective view of the present invention in the first embodiment of the present invention, where the elements  202  and  302  are removed for showing the interior of the structure of the present invention. 
         FIG. 4  is another partial perspective view of the present invention in the first embodiment of the present invention, where the elements  201  and  301  are removed for showing the interior of the structure of the present invention. 
         FIG. 5  shows a cross sectional view about the assembled state of the present invention. 
         FIG. 6  shows another cross sectional view about the assembled state of the present invention, which is viewed from a side vertical to the side shown in  FIG. 5 . 
         FIGS. 7-1 ,  7 - 2  are perspective views showing the second embodiment of the present invention. 
         FIG. 8  shows the experimental result according to the device of the present invention. 
         FIG. 9  is a linear approximation of the results in  FIG. 8 . 
         FIG. 10  shows the prior art optical elements alignment structures. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In order that those skilled in the art can further understand the present invention, a description will be provided in the following in details. However, these descriptions and the appended drawings are only used to cause those skilled in the art to understand the objects, features, and characteristics of the present invention, but not to be used to confine the scope and spirit of the present invention defined in the appended claims. 
     With referring to  FIGS. 1 ,  2 ,  3 ,  4 ,  5  and  6 , where  FIG. 1  is an exploded perspective view showing the elements of the present invention in the first embodiment of the present invention.  FIG. 2  shows an assembly view of the present invention.  FIG. 3  is a partial perspective view of view of the present invention.  FIG. 3  is a partial perspective view of the present invention in the first embodiment of the present invention, where the elements  202  and  302  are removed for showing the interior of the structure of the present invention.  FIG. 4  is another partial perspective view of the present invention in the first embodiment of the present invention, where the elements  201  and  301  are removed for showing the interior of the structure of the present invention.  FIG. 5  shows a cross sectional view about the assembled state of the present invention.  FIG. 6  shows another cross sectional view about the assembled state of the present invention, which is viewed from a side vertical to the side shown in  FIG. 5 . The elements of the present invention will be described in the following. 
     A platform  100  has an upper surface  101  and a lower surface  102 . Preferably, the upper surface  101  is a flat surface. 
     A front supporting block  201  and a rear supporting block  202  are firmly installed upon the upper surface  101  of the platform  100 . For example, the front supporting block  201  and the rear supporting block  202  can be embedded into, or screwed to or locked to the upper surface  101  of the platform  100 . In the drawing, the screw connection is illustrated. The front supporting block  201  and the rear supporting block  202  are retained with a distance for receiving other elements of the present invention. In the present invention, the front supporting block  201  and the rear supporting block  202  are rigid bodies and thus are difficult to deform in the operation of the device of the present invention. 
     A right metal sheet  301  and a left metal sheet  302  are arranged between and firmly secured to the front supporting block  201  and the rear supporting block  202 . The right metal sheet  301  is spaced from the left metal sheet  302 . The right metal sheet  301  and the left metal sheet  302  are suspended between the front supporting block  201  and rear supporting block  202  and are not contact with any surface of the platform  100 . The right metal sheet  301  and left metal sheet  302  are made of flexible material. That is to say, the right metal sheet  301  and left metal sheet  302  are slightly elastic and thus deformable within a slight extent. 
     A movable block  400  is arranged between the right metal sheet  301  and left metal sheet  302  and is firmly secured thereto. A lower surface  401  of the movable block  400  is spaced from the upper surface  101  of the platform  100 . In the present invention, for example the movable block  400  is screwed to the right metal sheet  301  and left metal sheet  302  so that the movable block  400 , right metal sheet  301  and left metal sheet  302  are formed as a rigid structure, that is, no relative movement between the movable block  400  and the left metal sheet  302  and between the movable block  400  and the right metal sheet  301 . As the movable block  400  moves, the left metal sheet  302  and right metal sheet  301  are also moved with the same extent. No relative movement exists therebetween. 
     In operation, the optical element for alignment can be placed upon the moveable block  400 , for example, if the optical element is an optical fiber, than a clamp arm is located upon an upper surface  402  of the moveable block  400 . The clamp arm has a V shape groove for locating an optical fiber. In alignment of two optical fibers, it is necessary to fine-adjust the moveable block  400  so as to drive the clamp arm to align with another one. However the core of a fiber is very tiny, generally, it has a size of micrometers. Thus the movement of the optical fiber is just a few micrometers. Therefore, it is needed to have a design which cause the moveable block  400  to move several micrometers in many steps with each step in the range of several sub-micrometers, while these minor steps must be controllable by the operation. The following elements of the present invention cause this idea could be realized, while electric power is unnecessary. 
     A first rod  501  is connected to the lower surface  401  of the movable block  400 , while do not contact the upper surface  101  of the platform  100 . 
     A weak spring  601  has a middle section connected to the first rod  501 . The weak spring  601  has a small elastic coefficient K 1 . 
     A strong spring  602  has two ends which are firmly secured (or exampled screwed) to the front supporting block  201  and rear supporting block  202 . The middle section of the strong spring  602  is contact to the right metal sheet. The strong spring  602  has a large elastic coefficient K 2 . The large elastic coefficient K 2  is much greater than the small elastic coefficient K 1 . For example the large elastic coefficient K 2  is 50 times or 100 times of the small elastic coefficient K 1 . 
     In the present invention, it is preferable, that the weak spring  601  and the strong spring  602  are elastic reeds which could provide a steady operation which is a main concern in the present invention. Generally, elastic reeds are preferred than helical springs. However all elastic springs are suitably used in the present invention after they are especially selected and designed, and thus all these are within the scope of the present invention. 
     A translation stage  700  is connected to the weak spring  601 . Adjustment of the translation stage  700  will release or tighten the weak spring  601 . However the main design of the translation stage  700  is to tighten (and thus compress) the weak spring  601  or extend (and thus prolong) the weak spring  601 , that is to adjust the length of the weak spring  601 . 
     Thus, other structure suitable for above mentioned function is permissible to be used in the present invention. As illustrated in the drawing, we depict that the translation stage  700  is protruded out from a lower side of the right metal sheet  301 , but this is not confined to confine the scope of the present invention. Other design suiting for the operation of the translation stage  700  is permissible in the present invention. 
     In the present invention, other driving apparatus which can compress or expand the weak spring  601  is also within the scope of the present invention. 
     In the present invention, the translation stage  700  serves to convert screwing operation into linear operation. In the drawing, it is illustrated that the translation stage  700  has a screwing head  701  for driving the plate  702  to move along a base  703 . The retaining block  704  is locked to the plate  702 . Two ends of the weak spring  601  are locked to the retaining block  704 . In operation, screwing the head  701  will cause that weak spring  601  to move forwards or backwards. 
     Operation of the present invention will be described herein. Initially, the structure of the present invention is at a wholly released state. That is to say, the weak spring  601  is completely released without compression or extension. Then the translation stage  700  is screwed forwards to push the weak spring  601  forwards. The movement of the weak spring  601  will drive the first rod  501  also moves forwards. As a result, the movable block  400  will move leftwards to drive the left metal sheet  302  and right metal sheet  301  to also move leftwards. However the movement of the moveable block  400  is interacted with the strong spring  602  through the right metal sheet  301 , while the strong spring  602  has a large elastic coefficient K 2  which is far greater than that of weak spring  601 . For example, herein we assume that the large elastic coefficient K 2  is 100 times of the small elastic coefficient K 1 . Thus the strong spring  602  will strongly retain the moveable block  400  not to move, while the weak spring  601  tries to move the moveable block  400  with a greater extend. As a result, the moveable block  400  only moves through a little distance. From physical calculation, the movement of the moveable block  400  is only K 1 /K 2  of the movement of the weak spring  601 . In this example, the movement of the moveable block  400  is only 1/100 of the movement of the weak spring  601 . Thus as the weak spring  601  moves through 10 μm (micrometer), the moveable block  400  will move through 0.1 μm. Thus, the moveable block  400  is fine-adjusted. 
     Furthermore, in the present invention, to reduce the vibration of the whole structure, a preload is added to the moveable block  400 . That is, in an assembly state, the strong spring  602  is deformed with a predetermined extent so as to apply a load to the moveable block  400  and thus the right metal sheet  301  and left metal sheet  302  will also deform with the same extent experienced by the moveable block  400 . The deformations of the right metal sheet  301  and the left metal sheet  302  are along a direction counter to that of the pushing forward direction of the weak spring  601 . This preload will cause that the structure of the present invention has the ability to prevent from vibration. 
     Moreover, it should emphasize that the present invention can prevent from the interference of friction force, that is, it is frictionless. In the present invention, the moveable block  400 , left metal sheet  302  and right metal sheet  301  are suspended and spaced from the upper surface  101 . They do not contact with the upper surface  101  of the platform  100 . In the driving operation of the weak spring  601 , the moveable block  400 , right metal sheet  301  and left metal sheet  302  are formed as a rigid body. No relative movement occurs between any two elements and thus no friction generates. The frictionless property is helpful to the precision of the system. As known in the art, the friction will reduce the precision due to the transfer of force is ineffective and the operator can not precisely estimate the effect of the friction. As a result, the precision of system is reduced. However the tricked design of the present invention has greatly reduced the effect of friction force. 
     In the second embodiment, as illustrated in  FIG. 7 , in this embodiment, those identical to the above embodiment will not be further described herein. Only those different from above embodiment are described. However all the elements of the second embodiment are identical to those in the first embodiment, only that no first rod  501  is used. The weak spring  601  is directly applied to the left metal sheet  302 . This also has the same effect as above said and thus the details will not be further described herein. 
     Referring to  FIGS. 8 and 9 , the effect of the present invention is illustrated. In  FIG. 8 , the data in first and second lines (viewed from left side) show the individual moving distance and the accumulated distance in each adjusting step by rotating the translation stage. The third lines shows a linear approximation of the data in the second line. The data in fourth line shows the differences between the second and third lines. In the second line of  FIG. 8 , it shows that each moving step will cause a movement of the moveable block  400  to move through about 66 nanometers. This is suitable for the adjustment of optical elements. For example, a diameter of a core of a fiber is about 10 micrometers. Thus 66 nanometers is 1/150 of the diameter of the core. The step is small enough so that the optical element (optical fiber) can be precisely aligned. 
     The present invention is thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.