Changes

==Sub-Micron Precision Using Dial Indicators==

==Sub-Micron Precision Using Dial Indicators==

[[Image:iso2.png|center|thumb|300px|Figure: Rendering of ablation setup showing position of dial indicator used to locate the x-translation stage.]]

[[Image:iso2.png|center|thumb|300px|Figure 16: Rendering of ablation setup showing position of dial indicator used to locate the x-translation stage.]]

As shown in the figure above the ablation chamber is mounted on two orthogonal translation stages, both with bidirectional repeatability of <1.5 µm and minimum achievable incremental movement of 0.05 µm/. The x-stage moves the diamond in the horizontal plane with respect to the lab floor. The y-stage increments at a 45◦ angle to the lab floor which is in the same plane as the diamond. Digital dial indicators with sub-micron resolution were installed to measure the positions of the x and y translation stage and were used in a study to measure the non-linearity of the y-translation stage motor. Non-linearity (movement in the lead-screw of the translation stage which does not place the stage at the requested position) of the y-stage is critical due to the row-by-row rastering sequence used to deferentially ablate the diamond sample. Each row has a unique sequence of laser pulses that correspond to an exact position on the diamond and the control of the ablation rate relies on the overlap between these rows. The dial indicator shown in Figure 11 is placed at a 45◦ angle and makes contact with an aluminum extension mounted to the y-stage. The dial indicator has a rolling bearing attached to its end so that it rides along the extension as the x-translation stage moves back and forth. The ablation chamber was moved to a series of y coordinates and the difference between the desired displacement and the displacement measured by the dial indicator was taken and is shown in Figure 12a.

As shown in the figure above the ablation chamber is mounted on two orthogonal translation stages, both with bidirectional repeatability of <1.5 µm and minimum achievable incremental movement of 0.05 µm/. The x-stage moves the diamond in the horizontal plane with respect to the lab floor. The y-stage increments at a 45◦ angle to the lab floor which is in the same plane as the diamond. Digital dial indicators with sub-micron resolution were installed to measure the positions of the x and y translation stage and were used in a study to measure the non-linearity of the y-translation stage motor. Non-linearity (movement in the lead-screw of the translation stage which does not place the stage at the requested position) of the y-stage is critical due to the row-by-row rastering sequence used to deferentially ablate the diamond sample. Each row has a unique sequence of laser pulses that correspond to an exact position on the diamond and the control of the ablation rate relies on the overlap between these rows. The dial indicator shown in Figure 16 is placed at a 45◦ angle and makes contact with an aluminum extension mounted to the y-stage. The dial indicator has a rolling bearing attached to its end so that it rides along the extension as the x-translation stage moves back and forth. The ablation chamber was moved to a series of y coordinates and the difference between the desired displacement and the displacement measured by the dial indicator was taken and is shown in Figure 17a.

The same study was conducted again, but the dial indicator was used to 17 require that the y-translation stage fall within 1 µm of the desired position. This was accomplished by creating an internal loop within the LabView software responsible for the movement of the translation stages. At the beginning of the sequence, the y-stage is homed and brought to an origin position. The reading of the dial indicator at this origin is recorded and all subsequent moves in the y-stage coordinate system are translated into the dial indicator coordinate system using this value. After the y-stage moves to the provided coordinate, the LabView software queries the dial indicator for a position. If the dial indicator value matches the expected value to within a micron, the sequence continues, if not the y-stage is moved by the dial indicator difference in position and the dial indicator is queried again until the 1 micron condition is satisfied. Figure 12b illustrates the improvement made to the y-stage which now has the accuracy of 1 micron. The study concluded that position of the diamond relative to the focal spot would be determined by the sub-micron dial indicators in both the x and y axis.

The same study was conducted again, but the dial indicator was used to 17 require that the y-translation stage fall within 1 µm of the desired position. This was accomplished by creating an internal loop within the LabView software responsible for the movement of the translation stages. At the beginning of the sequence, the y-stage is homed and brought to an origin position. The reading of the dial indicator at this origin is recorded and all subsequent moves in the y-stage coordinate system are translated into the dial indicator coordinate system using this value. After the y-stage moves to the provided coordinate, the LabView software queries the dial indicator for a position. If the dial indicator value matches the expected value to within a micron, the sequence continues, if not the y-stage is moved by the dial indicator difference in position and the dial indicator is queried again until the 1 micron condition is satisfied. Figure 17b illustrates the improvement made to the y-stage which now has the accuracy of 1 micron. The study concluded that position of the diamond relative to the focal spot would be determined by the sub-micron dial indicators in both the x and y axis.

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| [[Image:deltay_bad.png|left|thumb|300px|Figure: The histogram shown in Figure 11a displays the difference between the position reported by the y-stage and the position measured by the dial indicator. The wide RMS suggests a large non-linearity in the motor.]] || &nbsp; ||  

| [[Image:deltay_bad.png|left|thumb|300px|Figure 17a: The histogram shown in Figure 17a displays the difference between the position reported by the y-stage and the position measured by the dial indicator. The wide RMS suggests a large non-linearity in the motor.]] || &nbsp; ||  

  [[Image:deltay_good.png|right|thumb|300px|Figure: R The histogram in Figure 11b shows the same difference after the dial indicator was used to correct for the non-linearity in the y-stage.]]

  [[Image:deltay_good.png|right|thumb|300px|Figure 17b: R The histogram in Figure 17b shows the same difference after the dial indicator was used to correct for the non-linearity in the y-stage.]]

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