JP2017058174A - Linear gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear gauge in which pressing force of a gage head can be adjusted in accordance with a surface shape of an object to be measured or quality of material thereof.SOLUTION: A linear gauge 1 comprises: a shaft 11 that is coupled to a gage head 10; an air slider 12 that supports a lateral surface 110 of the shaft 11 by surrounding the lateral surface, and enables the shaft 11 to move in its axis direction (± Z-directions); movement means 13 that causes the shaft 11 to move in its axis direction; a scale 14 that includes measuring marks 140; a case 2 that houses the shaft 11, the air slider 12, the scale 14 and the movement means 13; an emission port 16 that causes air to be emitted to an interior of the case 2 from the air slider 12 to be emitted outside the case 2; and a throttle valve 17 that adjusts an amount of emission of the air to be emitted from the emission port 16. A pressure of an internal space of the case 2 is adjusted by the throttle valve 17, which in turn pressing force of the gage head 10 is adjusted in accordance with a surface shape of a an object to be measured or quality of material thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a linear gauge for measuring the thickness of an object to be measured.

  A grinding apparatus for grinding a workpiece such as a wafer includes at least a chuck table having a holding surface for holding the workpiece and a grinding means having a grinding wheel for grinding the workpiece held on the chuck table. The upper surface of the workpiece is ground to a predetermined thickness by the grinding means while holding the workpiece on the chuck table.

  When grinding a workpiece, it is necessary to monitor the thickness of the workpiece. For example, the thickness of the workpiece is measured using two linear gauges. Specifically, the upper surface height of the chuck table is measured with one linear gauge, the upper surface height of the workpiece is measured with the other linear gauge, and the difference between the measured values measured with each linear gauge is measured. The thickness is calculated as the thickness of the workpiece (for example, see Patent Document 1 below). When the workpiece reaches a predetermined thickness, the grinding is finished.

  Examples of the linear gauge include a direct-acting linear gauge and a lever-type linear gauge. When measuring the thickness of a workpiece being processed using a linear linear gauge, when the shaft with the probe connected to one end moves directly, grinding water containing grinding debris enters the linear gauge mechanism. There is a problem that grinding scraps get caught in the support means for supporting the shaft, and a lever-type linear gauge may be used.

  On the other hand, when measuring the thickness of a workpiece using a lever type linear gauge, it is necessary to correct the measurement value according to the distance between the fulcrum and the measurement point, which is troublesome. In that respect, if it is a linear motion type linear gauge, the thickness of the workpiece can be easily detected by simply reading the scale scale that moves linearly with the shaft (see, for example, Patent Document 2 below).

JP 2008-073785 A JP 2011-123022 A

  However, in the linear gauge as described above, since the pressing force for pressing the measuring element against the object to be measured cannot be adjusted, the pressing force cannot be adjusted according to the surface shape or material of the object to be measured. Therefore, for example, when the surface of the object to be measured before grinding is uneven, it is necessary to strongly press the measuring element so that the measuring element does not jump on the uneven surface. Further, when measuring the thickness of an object to be measured made of a soft material, it is necessary to press the measuring element weakly so that the measuring element is not buried in the soft object to be measured.

  The present invention has been made in view of the above circumstances, and there is a problem to be solved by enabling the pressing force of the probe to be adjusted according to the surface shape and material of the object to be measured.

  The present invention relates to a linear gauge for measuring the displacement of the surface of an object to be measured, a measuring element whose tip is brought into contact with the surface of the object to be measured, a shaft connected to the measuring element, and a cylinder accommodating the shaft. The inner support surface of the shaft faces the side surface of the shaft, air is blown from the support surface toward the side surface of the shaft, air is interposed between the side surface of the shaft and the support surface, and the cylinder is supported. An air slider that discharges air from above and below the shaft to allow the shaft to move in the axial direction, a scale connected to the shaft for detecting the axial position of the shaft, and the shaft in the axial direction A moving means for moving the shaft, an air slider, the scale, and the moving means, and an exhaust port for exhausting air exhausted from the air slider into the case. Comprising a valve for adjusting the amount of exhaust gas exhausted from the exhaust port, the.

  The moving means is composed of a cylinder and a piston, and a first force for moving the piston in a direction protruding from the cylinder and moving the shaft in a direction away from the object to be measured; By adjusting the amount of air exhausted to the outside of the case, the pressure difference between the second force that adjusts the pressure in the case and moves the shaft in the direction of projecting the shaft is measured. An adjustment function for adjusting the pressing force of the measuring element is provided.

  The linear gauge according to the present invention enables a movement of the shaft in the axial direction by surrounding and supporting the measuring element whose tip is in contact with the surface of the object to be measured, the shaft connected to the measuring element, and the side surface of the shaft. An air slider, a moving means for moving the shaft in its axial direction, a scale connected to the shaft for detecting the axial position of the shaft, a case for housing the shaft, the air slider, the scale, and the moving means, Since it has an exhaust port for exhausting the air exhausted from the air slider into the case to the outside of the case and a valve for adjusting the exhaust amount of the air exhausted from the exhaust port, by adjusting the pressure in the case by the valve The axial movement of the shaft can be adjusted. Thereby, the pressing force of the measuring element with respect to the object to be measured can be adjusted.

  In the linear gauge, the moving means includes a cylinder and a piston, and a first force for moving the piston in a direction protruding from the cylinder and moving the shaft in a direction away from the object to be measured; By adjusting the amount of air exhausted from the inside of the case to the outside of the case, the difference in force between the second force that moves the shaft in the direction of protruding the shaft by adjusting the pressure inside the case is Since it has an adjustment function to adjust the pressing force of the probe, it can be pressed against the object by adjusting the pressing force of the probe according to the surface shape and material of the object to be measured. Can be measured accurately.

It is a perspective view which shows the structure of a linear gauge. It is sectional drawing which shows the state which adjusts the pressure in a case by adjusting the pressure in a case by opening and closing of a throttle valve. It is sectional drawing which shows the state which raises a shaft by a moving means and raises a measuring element from a to-be-measured object while opening a throttle valve. It is sectional drawing which shows the state which adjusts the pressure setting in a case with a regulator and adjusts the pressing force of a measuring element. It is sectional drawing which shows the state which adjusts the pressure setting in a case with a regulator, raises a shaft with a moving means, and retracts a measuring element from to-be-measured object. It is sectional drawing which shows the state which the measuring element raised by the compression spring. It is sectional drawing which shows the state which expands and contracts a compression spring and adjusts the pressing force of a measuring element. It is sectional drawing which shows the state which the measuring element raised by the tension spring. It is sectional drawing which shows the state which expands / contracts a tension spring and adjusts the pressing force of a measuring element.

  The linear gauge 1 shown in FIG. 1 is an example of a linear motion type linear gauge that measures the displacement of the surface of the object to be measured. The linear gauge 1 includes a measuring element 10 that brings the tip 10a into contact with the surface of the object to be measured, and one end connected to the measuring element 10 and the other end connected to the connecting member 3 so as to extend in the vertical direction (Z-axis direction). An existing shaft 11, an air slider 12 that surrounds and supports the side surface 110 of the shaft 11 and enables movement of the shaft 11 in the axial direction (± Z direction), and moving means 13 that moves the shaft 11 in the axial direction. And a scale 14 having a scale 140 connected to the shaft 11 via the connecting member 3 and extending in a direction parallel to the axial direction of the shaft 11, the shaft 11, the air slider 12, the scale 14, and the moving means 13. Detect the position of the shaft 11 that moves in the direction parallel to the axial direction of the shaft 11 and the shaft 11 that reads the scale 140 of the scale 14 and moves in the vertical direction. Means 15, an exhaust port 16 for exhausting the air exhausted from the air slider 12 into the case 2 to the outside of the case 2, and a throttle valve 17 for adjusting the exhaust amount of the air exhausted from the exhaust port 16. Yes.

  A case 2 constituting the linear gauge 1 is supported from below by a mounting table 4 shown in FIG. The shaft 11 is formed in a quadrangular prism shape, penetrates the case 2, and the measuring element 10 connected to one end of the shaft 11 protrudes downward from the lower surface of the case 2.

  The shape of the shaft 11 is not limited to a rectangular column shape, and may be a shape that does not rotate, that is, a shape that is not a cylinder. Therefore, it may be a polygonal column or an elliptical column. Further, a columnar shape in which only one of the side surfaces 110 of the shaft 11 is formed into a flat surface and the other surface is formed into a curved surface may be used. Thus, if at least one of the side surfaces 110 of the shaft 11 is formed as a flat surface, the shaft 11 can be restricted from moving in the rotational direction.

  The air slider 12 includes a cylinder 120 that accommodates the shaft 11, and the cylinder 120 is disposed on the placement surface 2 a inside the case 2. The cylinder 120 is formed with a hole having a rectangular cross section for accommodating the shaft 11 corresponding to the shape of the shaft 11, and the shaft 11 can be inserted into the hole to support the periphery of the shaft 11. It has become. Further, as shown in FIG. 2, the cylinder 120 is provided with an inner support surface 121 that faces the side surface 110 at an equal interval from the side surface 110 of the shaft 11, and toward the side surface 110 of the shaft 11 from the support surface 121. A plurality of jet ports 122 for blowing air, an inflow port 123 connected to an air supply source (not shown), and a flow path 124 for communicating the inflow port 123 with each of the jet ports 122 are provided. The support surface 121 is composed of four planar surfaces corresponding to the shape of the shaft 11.

  In the air slider 12, with the support surface 121 of the cylinder 120 facing the side surface 110 of the shaft 11, air is blown from each jet port 122 of the support surface 121 toward the side surface 110 of the shaft 11 to thereby support the side surface 110 and the support surface. The shaft 11 can be supported by interposing air between the shaft 121 and the shaft 11 by discharging the air flowing into the tube 120 from the upper exhaust port 125 and the lower exhaust port 126 of the tube 120. It can be moved in the direction (± Z direction).

  The moving means 13 is disposed in the vicinity of the shaft 11 and on the placement surface 2 a of the case 2. The moving means 13 includes at least a cylinder 130, a piston 131 that moves in a direction parallel to the axial direction of the shaft 11 inside the cylinder 130, and inflow ports 132 and 133 that allow air to flow into the cylinder 130. The shaft 11 can be moved linearly in the axial direction.

  Here, when the shaft 11 is lifted in the direction away from the object to be measured by the moving means 13, an air supply source (not shown) flows air into the inflow port 132 and supplies air into the cylinder 130. The piston 131 is raised inside 130. Then, after bringing the piston 131 into contact with the connecting member 3, the piston 131 is further raised to raise the connecting member 3, thereby raising the shaft 11 connected to the connecting member 3.

  On the other hand, when the shaft 11 is lowered in the direction approaching the object to be measured by the moving means 13, it is regulated by an air supply source (not shown) flowing air into the inlet 133 and supplying air into the cylinder 130. By lowering the piston 131 at a high speed, the speed at which the shaft 11 is lowered by the dead weight of the shaft 11 and the connecting member 3 connected to the shaft 11 can be limited. Then, the shaft 11 is lowered until the tip portion 10a of the probe 10 contacts the upper surface of the object to be measured.

  As shown in FIG. 2, the scale 14 hangs from the end of the connecting member 3 and is disposed in parallel with the extending direction of the shaft 11. The detection means 15 includes a support plate 150 connected to the end of the case 2 and extending in the Z-axis direction, and a detection unit 151 disposed at the tip of the support plate 150, and a scale 140 of the scale 14. The detection unit 151 is facing.

  The exhaust port 16 is disposed on the upper side of the case 2. The exhaust port 16 can exhaust the air exhausted into the case 2 from the upper exhaust port 125 and the lower exhaust port 126 of the cylinder 120 to the outside of the case 2. A throttle valve 17 is connected to the exhaust port 16 as an example of a valve that adjusts the amount of air exhausted from the exhaust port 16. In addition, the arrangement | positioning position of the exhaust port 16 is not limited to the position shown to this embodiment.

  By restricting the throttle valve 17, the amount of air exhausted from the exhaust port 16 can be reduced to increase the pressure in the case 2. By opening the throttle valve 17, the air exhausted from the exhaust port 16 The pressure in the case 2 can be lowered by increasing the amount of exhaust. Thus, by adjusting the pressure in the internal space 7 of the case 2, the axial movement of the shaft 11 can be adjusted to adjust the pressing pressure of the probe 10 against the object to be measured. The linear gauge 1 configured as described above is used by being mounted on a device that performs grinding on an object to be measured such as a grinding device.

  Next, an operation example for measuring the thickness of the DUT 6 shown in FIG. 2 using the linear gauge 1 will be described. The measurement object 6 is an example of a workpiece such as a wafer, and is not particularly limited. For example, when the workpiece 6 is ground in the grinding apparatus, the workpiece 6 is held on the holding table 5 and the workpiece 6 is ground to a desired thickness by a grinding means (not shown). While the workpiece 6 is being ground, the thickness of the workpiece 6 is always measured using the linear gauge 1 to monitor the change in thickness. Grinding includes rough grinding that roughly grinds the object to be measured and finish grinding that finishes the roughly ground object to be measured. Below, the thickness of the object to be measured during rough grinding is measured. The case where it does is explained in full detail.

  First, as shown in FIG. 2, the linear gauge 1 is positioned above the DUT 6 held on the holding table 5. Next, the moving means 13 lowers the shaft 11 in the −Z direction approaching the DUT 6. At this time, air is blown toward the side surface 110 of the shaft 11 from each jet port 122 of the air slider 12 so that air is interposed between the side surface 110 of the shaft 11 and the support surface 121 of the cylinder 120 to support the shaft 11. In addition, the movement of the shaft 11 in the rotational direction is regulated by the side surface 110.

  In the linear gauge 1, the pressing force of the probe 10 against the measurement object 6 is adjusted according to the surface shape and material of the measurement object 6. As shown in FIG. 2, this adjustment is performed by moving the piston 131 in a direction (+ Z direction) protruding upward from the cylinder 130 and moving the shaft 11 away from the DUT 6 in the direction of arrow A, When adjusting the pressure of the internal space 7 of the case 2 by adjusting the amount of air exhausted from the inside of the case 2, the arrow moves when the shaft 11 is moved downward (−Z direction) from the lower surface of the case 2. This is done by controlling the force difference P with the second force acting in the B direction. That is, the force difference P has an adjustment function for adjusting the strength of the pressing force of the measuring element 10. As the force difference P is increased, the shaft 11 is pushed down so that the measuring element 10 can be pressed more strongly against the object 6 to be measured. As the force difference P is decreased, the measuring element 10 is pressed more weakly against the object 6 to be measured. be able to.

  Here, for example, when the surface of the object 6 to be measured is an uneven surface, the pressing force of the probe 10 is increased by the linear gauge 1 as shown in FIG. Specifically, the throttle valve 17 is throttled to reduce the amount of air exhausted from the case 2 through the exhaust port 16 and increase the pressure in the internal space 7 of the case 2. As the pressure in the internal space 7 increases, the second force acting in the direction of arrow B becomes stronger than the first force acting in the direction of arrow A. Using the force difference P generated in this way, the shaft 11 can be lowered together with the connecting member 3, and the probe 10 can be strongly pressed against the object 6 to be measured. At this time, the tip 10 a of the probe 10 does not jump on the uneven surface of the object 6 to be measured. Further, when the probe 10 is strongly pressed against the object 6 to be measured, the air supplied into the cylinder 130 is shut off, and the piston 131 is lowered to be separated from the connecting member 3, thereby increasing the internal space 7. The probe 10 can be strongly pressed against the object 6 by pressure.

  On the other hand, for example, when the DUT 6 is made of a soft material, the pressing force of the probe 10 is weakened by the linear gauge 1. Specifically, by opening the throttle valve 17, the amount of air exhausted in the case 2 exhausted from the exhaust port 16 is increased, and the pressure in the internal space 7 of the case 2 is lowered. As the pressure in the internal space 7 decreases, the force difference P decreases. Accordingly, the measuring element 10 can be pressed weakly against the object 6 to be measured. At this time, the tip portion 10a of the measuring element 10 is not buried in the surface of the measurement object 6 made of a soft material.

  In this way, when the pressing force of the measuring element 10 is adjusted by the linear gauge 1 according to the surface shape and material of the measuring object 6 and the measuring object 10 is pressed against the measuring object 6 by the tip 10a, at this time The detecting unit 151 reads the scale 140 of the scale 14, and detects the thickness of the DUT 6 based on the read position.

  After the thickness of the DUT 6 reaches a predetermined value and the measurement is completed, the moving means 13 raises the shaft 11 in the upward direction (+ Z direction) away from the DUT 6 as shown in FIG. Specifically, the throttle valve 17 is opened, and an air supply source causes a predetermined air to flow into the inflow port 132 to supply air into the cylinder 130, whereby the first force in the direction of arrow A is applied in the direction of arrow B. The piston 131 is raised in the + Z direction inside the cylinder 130 by making it larger than the second force. The tip 131 a of the probe 10 is retracted from the object to be measured 6 by bringing the piston 131 into contact with the connecting member 3 and further pushing up the connecting member 3 to raise the shaft 11 in the + Z direction.

  As described above, the linear gauge 1 according to the present invention surrounds and supports the shaft 11 connected to the probe 10 and the side surface 110 of the shaft 11 and enables the shaft 11 to move in the axial direction (± Z direction). The air slider 12, the moving means 13 for moving the shaft 11 in the axial direction thereof, the scale 14 having the scale 140, the case 2 housing the shaft 11, the air slider 12, the scale 14, and the moving means 13, and the air Since the exhaust port 16 for exhausting the air exhausted from the slider 12 into the case 2 from the case 2 and the throttle valve 17 for adjusting the exhaust amount of the air exhausted from the exhaust port 16 are provided, the throttle valve 17 causes the case 2 to be exhausted. By adjusting the pressure in the internal space 7, the movement of the shaft 11 in the axial direction (± Z direction) can be adjusted. That is, the first force acting in the direction of arrow A that projects the piston 131 from the cylinder 130 and the second force acting in the direction of arrow B that projects the shaft 11 from the lower surface of the case 2 by adjusting the internal pressure of the case 2 with the throttle valve 17. The pressing force of the probe 10 against the object to be measured 6 can be adjusted using the difference P between the force and the force P. Thereby, the measuring element 10 can be pressed against the measured object 6 with a pressing force corresponding to the surface shape and material of the measured object 6, and the thickness of the measured object 6 can be measured accurately.

  A linear gauge 1a shown in FIGS. 4 and 5 is a modified example of the linear gauge, and a regulator 18 with a relief valve is attached to the exhaust port 16. In the linear gauge 1a, the internal space 7 of the case 2 can be set to a desired pressure by the regulator 18, and the air in the case 2 can be exhausted from the exhaust port 16 through the relief valve. The linear gauge 1a has the same configuration as that of the linear gauge 1 except that a regulator 18 is provided instead of the throttle valve 17.

  For example, when the surface of the DUT 6 is uneven, the pressing force of the probe 10 is increased by the linear gauge 1a as shown in FIG. Specifically, the pressure of the internal space 7 is set higher by reducing the amount of air exhausted from the exhaust port 16 through the relief valve by the regulator 18. When the pressure in the internal space 7 of the case 2 is increased according to the setting of the regulator 18, the second force acting in the arrow B direction becomes stronger than the first force acting in the arrow A direction. The shaft 11 can be lowered together with the connecting member 3 by using the force difference P caused by this, and the probe 10 can be strongly pressed against the object 6 to be measured.

  On the other hand, for example, when the DUT 6 is made of a soft material, the pressing force of the probe 10 is weakened by the linear gauge 1a. Specifically, the amount of air exhausted from the exhaust port 16 through the relief valve is increased by the regulator 18 to set the pressure in the internal space 7 low. When the pressure in the internal space 7 of the case 2 is lowered according to the setting of the regulator 18, the force difference P becomes small and the probe 10 can be pressed weakly against the object 6 to be measured.

  The operation of measuring the thickness of the DUT 6 using the linear gauge 1a and the operation of moving the probe 10 up and down by the moving means 13 are the same as those of the linear gauge 1. That is, the scale 14 when the linear gauge 1a is pressed against the measurement object 6 with the tip 10a of the measurement element 10 while adjusting the pressing force of the measurement element 10 according to the surface shape or material of the measurement object 6. The detection unit 151 reads the scale 140 and detects the thickness of the DUT 6. After the thickness of the DUT 6 reaches a predetermined value and the measurement is completed, as shown in FIG. 5, the regulator 18 adjusts the pressure in the internal space 7 of the case 2 to be low, and the moving means 13 The tip 10 a of the probe 10 is retreated from the object to be measured 6 by being raised upward (in the + Z direction) away from the object to be measured 6.

  Thus, since the linear gauge 1a includes the regulator 18 that adjusts the exhaust amount of air exhausted from the exhaust port 16, the regulator 18 sets the pressure of the internal space 7 of the case 2 to a desired pressure setting, The movement of the shaft 11 in the axial direction (± Z direction) can be adjusted. Therefore, similarly to the linear gauge 1, the measuring element 10 can be pressed against the measured object 6 with a pressing force according to the surface shape and material of the measured object 6, and the thickness of the measured object 6 is accurately measured. be able to.

  The moving means 13 shown in the present embodiment is configured to raise the piston 131 by bringing air into the cylinder 130 to contact the connecting member 3 and raise the measuring element 10. However, the moving means 13 is limited to this configuration. Instead, for example, like the linear gauge 1 b shown in FIG. 6, a moving means 19 constituted by a compression spring 190 fixed to the mounting surface 2 a of the case 2 and a piston 191 connected to the compression spring 190 is provided. It may be used. In the moving means 19, when the internal space 7 of the case 2 is at normal pressure, the probe 191 is pushed up by the repulsive force of the compression spring 190 and the probe 10 is constantly raised. When the pressure in the internal space 7 becomes stronger than the repulsive force of the compression spring 190 by increasing the pressure in the internal space 7 of the case 2 by the regulator 18, the compression spring 190 is compressed as shown in FIG. 3, the shaft 11 can be lowered and the probe 10 can be strongly pressed against the object 6 to be measured. When the probe 10 is pressed weakly against the object 6 to be measured, the pressure in the internal space 7 of the case 2 is adjusted to be low by the regulator 18 so that the repulsive force of the compression spring 190 is increased.

  Further, for example, a moving means 20 having a tension spring 200 may be used like a linear gauge 1c shown in FIG. The moving means 20 has a configuration in which one end of the tension spring 200 is connected to the connecting member 3 and the other end of the tension spring 200 is connected to the inside of the case 2. In the moving means 20, when the internal space 7 of the case 2 is at normal pressure, the connecting member 3 is pulled up by the repulsive force of the tension spring 200, and the measuring element 10 is constantly raised. When the pressure in the internal space 7 becomes stronger than the repulsive force of the tension spring 200 by increasing the pressure in the internal space 7 of the case 2 by the regulator 18, the tension spring 200 is pulled and the connecting member as shown in FIG. 9. 3, the shaft 11 can be lowered and the probe 10 can be strongly pressed against the object 6 to be measured. When pressing the probe 10 weakly against the object 6 to be measured, the regulator 18 may be adjusted so that the pressure in the internal space 7 of the case 2 is lowered so that the repulsive force of the tension spring 200 becomes stronger.

  In the present embodiment, the case where the thickness of the workpiece 6 during rough grinding is measured has been described. However, when finish grinding is performed, the tip 10a of the probe 10 on the surface of the workpiece 6 after finish grinding is provided. In order not to leave a mark, it is preferable to adjust the pressing force of the measuring element 10 against the object 6 to be measured with a linear gauge 1, 1a, 1b or 1c.

DESCRIPTION OF SYMBOLS 1, 1a, 1b, 1c: Linear gauge 2: Case 2a: Mounting surface 3: Connecting member 4: Mounting base 5: Holding table 6: Measuring object 7: Internal space 10: Measuring element 10a: Tip part 11: Shaft 110: Side surface 12: Air slider 120: Tube 121: Support surface 122: Jet outlet 123: Inlet 124: Flow path 125: Upper exhaust port 126: Lower exhaust port 13 130: Cylinder 131: Piston 132, 133: Inlet port 14: Scale 140: Scale 15: Detection means 150: Support plate 151: Detection section 16: Exhaust port 17: Throttle valve 18: Regulator 19: Movement means 190: Compression spring 191: Piston 20: Movement means 200: Tension spring

Claims (2)

A linear gauge that measures the displacement of the surface of the object to be measured,
A probe that contacts the surface of the object to be measured;
A shaft coupled to the probe;
The inner support surface of the cylinder accommodating the shaft faces the side surface of the shaft, air is blown from the support surface toward the side surface of the shaft, and air is interposed between the side surface of the shaft and the support surface. An air slider that supports the shaft and discharges air from above and below the cylinder to allow axial movement of the shaft;
A scale connected to the shaft for detecting the axial position of the shaft;
Moving means for moving the shaft in the axial direction;
A case for housing the shaft, the air slider, the scale, and the moving means;
An exhaust port for exhausting air exhausted from the air slider into the case to the outside of the case;
A linear gauge comprising: a valve for adjusting an exhaust amount exhausted from the exhaust port. The moving means includes a cylinder and a piston,
A first force for moving the piston in a direction protruding from the cylinder and moving the shaft in a direction away from the object to be measured;
The difference in force between the second force that moves the shaft in the direction of projecting the shaft by adjusting the pressure in the case by adjusting the amount of air exhausted from the case to the outside of the case is measured. The linear gauge according to claim 1, wherein the linear gauge has an adjustment function of adjusting a pressing force of the probe on the shaft against the shaft.

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