A NANOPOSITIONER FOR MOVING AN OBJECT IN NANOMETER RESOLUTION AND METHOD THEREOF

FIELD OF THE INVENTION The present invention relates to the fiexural nanopositioning technology with nanometer resolution without four bar mechanism design. The main crux of the invention is to avoid a few parasitic errors like perpendicular deflections and arcuate motions with out using four bar mechanism design as generally followed so as. The present invention in particular relates to a nanopositioner for moving an object in nanometer resolution in desired direction without any parasitic displacement with translational movement and method thereof.

BACKGROUND OF THE INVENTION AND PRIOR ART

Positioning objects such as lenses, fibers, tools, sensors etc., with respect to the nanometer resolution is a challenging one. With the advent of the technology in various fields such as photonics, optics, semiconductor, microscopy etc., the requirement for precise positioning with nanometer resolution is inevitable.

Parallelogram is a 4 bar mechanism which is followed generally to design the fiexural

Nanopositioning stage. It has its own advantages and disadvantages. The advantages are simple in design and manufacturing. The disadvantages are it requires compensating designs to reduce arcuate motion and out of plane movements.

When objects are moved in a nanometer range, there would be additional displacements from undesired axes, which are known as parasitic errors. These errors prevent the objects from moving in a straight line and results in deviation from the desired targets. These also prevent the system from moving to the full range of displacement. Out — of

— plane movement, Perpendicular deflection and arcuate motion are the common errors occurring in any nanopositioners. Controlling the design / manufacturing processes, out

- of - plane movement can be minimized. By integrating two parallelograms in perpendicular direction, the second error can be reduced. However, out - of - plane movement and Perpendicular deflection are occurring in a straight line whereas the arcuate motion causes objects to move in a curved path.

The stage (4) which is to be moved in linear direction is controlled by two identical turning arms (1) either side. The turning arms (1) are connected to the stage (4) via a

revolute pair (2). The actuator is placed common to the both turning arms. On actuation, both the turning arms are rotating in opposite direction either pushing or pulling the revolute pair connected stage.

The paper titled "Designing Springs for Parallel Motion" by George H. Neugebauer, Machine Design, August 7, 1980, pp 1 19 - 120, indicates that actuation at the mid way along the slotted spring provides parallel motion.

Advantages: The arcuate motion is completely eliminated and out of plane movement is also absent (depending on the tolerance and range of displacement) in this design. Need for central actuation is not required in this design that is location of load is not the concern here.

Disadvantages: The identical turning arms are critical and the similarity in parameters including tolerance should be maintained properly.

OBJECTS OF THE INVENTION

The primary objective of the present invention is to provide nanopositioners with pure translational movement without providing any error compensation.

Yet another object of the present invention is to design linear stage without parallelogram concept. still another object of the present invention is to utilize two bar mechanism.

Still another objective of the present invention is to avoid parasitic errors like perpendicular deflections and arcuate motions.

Still another object of the present invention is to make use of the instant technology in various fields like astronomy, data storage, medical, metrology, micro machining, microscopy, photonics, precision machining, semi conductors etc.

STATEMENT OF THE INVENTION

Accordingly, the present invention provides for a nanopositioner for moving an object in nanometer resolution in desired direction without any parasitic displacement with translational movement, said nanopositioner comprises, pair of turning arms/rotary

flexures (1) connected to an actuator through amplifier lever (3) to push apart and pull the flexures (1); and a moving stage (4) connected to the turning arms/ rotary flexures (1) through a revolute pair (2); also a method for moving an object in nanometer resolution in desired direction without any parasitic displacement with translational movement, said method comprising steps of; energizing actuation points by an actuator to rotate turning arms/rotary flexures (1) in opposite direction; and transferring the energy from the rotating flexures (1) onto a moving stage (4) through a revolute pair (2) to move the object in nanometer resolution in desired direction; and also a method of constructing a nanopositioner for moving an object in nanometer resolution in desired direction without any parasitic displacement with pure translational, said method comprises; connecting pair of rotating arms/rotary flexures (1) and an actuator by means of amplifier lever (3) to push apart and pull the flexures (1); connecting a moving stage (4) with the turning arms/ rotary flexures (1) using a revolute pair (2) to construct the nanopositioner;

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

Figure Ia shows a Parallelogram

Figure Ib shows Deflection of a Parallelogram When actuated other than at the center of the parallelogram length- The angular deflection of the moving stage - ARCUATE MOTION

Figure Ic shows Deflection of the parallelogram when actuated at the center of the parallelogram length- Arcuate motion is corrected but PERPENDICULAR DEFLECTION still exists Figure 2 shows nanopositioner assembly showing the various parts of the assembly showing their positioners.

Figure 3 shows side view of nanopositioner. Figure 4 shows outline view of nanopositioner. Figure 5 shows simulation of working of nanopositioner. Figure 6 shows the mesh diagram of nanopositioner.

DETAILED DESCRIPTION OF THE INVENTION

The primary embodiment of the present invention is a nanopositioner for moving an object in nanometer resolution in desired direction without any parasitic displacement

with translational movement, said nanopositioner comprises, pair of turning arms/rotary flexures (1) connected to an actuator through amplifier lever (3) to push apart and pull the flexures (1); and a moving stage (4) connected to the turning arms/ rotary flexures

(1) through a revolute pair (2); In yet another embodiment of the present invention, either side of the moving stage (4) is controlled by two identical turning arms/rotary flexures (1).

In still another embodiment of the present invention, the actuator is placed common to both the turning arms/rotary flexures (1).

In still another embodiment of the present invention, the turning arms/ rotary flexures (1) rotate in opposite direction either pushing or pulling the revolute pair (2) which is connected to the moving stage (4).

In still another embodiment of the present invention, center of rotation of the turning arms/rotary flexures (1) are connected by a bar.

In still another embodiment of the present invention, the nanopositioner is a monolithic structure.

In still another embodiment of the present invention is a method for moving an object in nanometer resolution in desired direction without any parasitic displacement with translational movement, said method comprising steps of; energizing actuation points by an actuator to rotate turning arms/rotary flexures (1) in opposite direction; and transferring the energy from the rotating flexures (1) onto a moving stage (4) through a revolute pair (2) to move the object in nanometer resolution in desired direction.

In still another embodiment of the present invention, the turning arms/rotary flexures

(1) are turned in opposite direction with equal force.

In still another embodiment of the present invention, the object moves in linear direction

In still another embodiment of the present invention is a method of constructing a nanopositioner for moving an object in nanometer resolution in desired direction without any parasitic displacement with pure translational, said method comprises; connecting pair of rotating arms/rotary flexures (1) and an actuator by means of amplifier lever (3) to push apart and pull the flexures (1); connecting a moving stage

(4) with the turning arms/ rotary flexures (1) using a revolute pair (2) to construct the nanopositioner;'

In still another embodiment of the present invention, center of rotation of the turning arms/rotary flexures (1) are connected by a bar.

The concept explanation of parallelogram is illustrated I figures Ia, Ib and Ic.

According to the paper titled, "Some Parasitic Deflexions in Parallel Spring

Movements", by Prof. R V Jones and I R Young, theoretically the arcuate motion can be determined as follows,

Arcuate motion = [2(L - 2a) t ² ] (x) / D ² I ² ] -> Eq. (1)

Where L = length of the parallelogram column length a = height of actuation t = thickness of the flexure b = inter-column length x = displacement

When the height of actuation become halve the length of the parallelogram height (Figure 3), a = L/2

Thus the arcuate motion becomes zero theoretically.

The errors can be compensated by providing inverted parallelogram and adjusting the actuation point as per the equation provided above. Since this is adding more complexity and expensive, Rotary Balance Linear Stage is one of the solution here by added.

Couple of rotary flexures or tuning arms (1) is used here in place of four bar mechanism which is prone to introduce arcuate and perpendicular displacement called parasitic errors. When the turning arms or rotary flexures (1) are turned in opposite direction with equal force, they push or pull the arm attached to it linearly at the intersection. At this point the stage (4) is carved in order to achieve the linear displacement as shown in the following paragraph.

The present invention shall now be fully described with reference to the accompanying drawings in which, Figure 2 is a nanopositioner assembly showing the various parts of the assembly showing their positioners.

An identical turning arms or rotary flexures (1) are connected either of an actuator. The actuators .are not shown in figure. When the actuator expands and contracts, it pushes apart and pulls flexures with it. The amplifier levers (3) are used to connect the actuator and rotary / turning arms (1). The centers of the rotation of both the arms (1) are again connected by a bar (not shown in figures).

When the turning arms (1) rotate the bar will experience force at the center of the bar trying to push or pull. At this point a stage (4) is introduced connecting by means of flexures, which allows the stage (4) to move with push or pull force in linear direction as shown in skeleton diagram 2.

ANALYSIS OF ROTO-BALANCED

The model is made as per the figures 2-5 shown below. When torques over two circles or moment about the center of circles are applied at both the circular plates one in clockwise & other in anti clockwise directions, the blue plate shown below moves exactly in straight line. This is more controlled one than the four bar mechanisms.

The mesh diagram as depicted in figure 6 shows that the block moves exactly in straight line

Advantages of the Invention

• Error compensation designs are eliminated

• Perfect linear movement can be obtained.

• No additional actuator to counterbalance errors are required

• Entire systems forms a monolithic structure and hence manufacturing process is relatively simple.

Applications of the invention