JP4712464B2 - Shape measuring instruments - Google Patents

Description

  The present invention relates to a shape measuring machine having a contact sensor.

  In recent years, many shape measuring machines that measure the shape of an optical element (measurement object) such as a lens by using a contact probe provided at the tip of an operating shaft are known. Among these shape measuring machines, those having an operating shaft supported so as to be reciprocally movable in the axial direction and a probe provided at the tip of the operating shaft have been introduced (see Patent Document 1). .

  In this shape measuring machine, the probe is brought into contact with the object to be measured with the operating shaft biased toward the tip. From this state, when the object to be measured is moved in a direction perpendicular to the axial direction of the operating axis, the contact point between the object to be measured and the probe sequentially moves, and the probe follows the surface of the object to be measured. Move in the axial direction. At this time, the amount of displacement of the probe in the axial direction and the amount of displacement in the orthogonal direction are detected by a displacement amount detection means, and a predetermined calculation is performed based on the detection results, thereby providing a surface of the object to be measured. The shape is measured. And the surface shape of a to-be-measured object can be measured with high precision by improving the resolution of a displacement amount detection means.

Here, in order to detect the apex position at the maximum height or the minimum height in the axial direction of the surface of the object to be measured, the displacement amount of the probe is displayed as a numerical value on the application screen, and the object to be measured and the probe are displayed. In general, the maximum value or the minimum value of the numerical values is searched for while scanning the two.
JP 07-260471 A

  However, in the shape measuring machine as described above, as the resolution of the displacement detection means is increased, the numerical value on the application screen changes instantaneously according to the scanning of the object to be measured and the probe. There is a problem that it is difficult to find the maximum value or the minimum value by visually observing the numerical value. Therefore, there is a case where the display resolution of the application screen is lowered or a high frequency component is removed by a filter. However, if the display resolution is lowered, the dead zone region where the numerical value does not change even when scanned is expanded. An error in vertex detection occurs in that region.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a shape measuring machine capable of easily and accurately detecting the vertex position of an object to be measured.

In order to solve the above problems, the present invention provides the following means.
The shape measuring machine according to the present invention relatively scans the object to be measured and the stylus sensor while the stylus sensor is in contact with the surface of the object to be measured, and the object to be measured during this scan a form measuring instrument for measuring the surface shape of the object to be measured by the displacement amount of the stylus sensor in the height direction to be measured of the object to measure the amount of displacement in the height direction to be the measurement of the stylus sensor a Lissajous waveform generating means for generating based rather Lissajous waveform into a displacement amount measuring means for outputting a measurement signal, the measurement signal the is shift measuring means or RaIzuru force Te, electrical said Lissajous waveform generating means The Lissajous waveform generated by the Lissajous waveform generating means is input, and based on the Lissajous waveform, a predetermined origin is centered according to the movement of the stylus sensor relative to the object to be measured. Display means for displaying the trajectory of a point image to the rolling movement, and the point image in which the stylus sensor to scan the surface of the object to be measured is displayed on the display means and passing through the vertex of the object to be measured The rotation direction is reverse rotation .

In this shape measuring machine, when the object to be measured and the stylus sensor are relatively scanned while the stylus sensor is in contact with the surface of the object to be measured, the stylus sensor is placed on the surface of the object to be measured. Therefore, it is displaced in the height direction. For example, when detecting the apex position at the maximum height such as a convex lens, the touch point between the surface of the object to be measured and the stylus sensor moves from the scanning start point toward the apex position. The needle sensor is displaced in a direction away from the object to be measured. On the other hand, when the contact point reaches the vertex position and approaches the scanning end point, the displacement direction of the stylus sensor is switched to the opposite direction, that is, the direction approaching the object to be measured. In addition, when detecting a vertex position at the minimum height such as a concave lens, it is displaced in the opposite direction. Then, the displacement amount at the time of scanning is measured by the displacement amount measuring means, and the measurement results are sequentially output. Based on this output signal, the Lissajous waveform generation means sequentially generates Lissajous waveforms. When the stylus sensor is displaced in one direction, the Lissajous waveform is drawn in an arc shape in one direction. However, if the displacement of the stylus sensor is switched in the other direction, the direction in which the Lissajous waveform is drawn is also switched. Change.
Therefore, by looking at the change in the Lissajous waveform, it is possible to easily grasp the timing at which the direction of displacement of the stylus sensor switches to the opposite direction.
Here, the height direction is not uniquely determined from the shape of the surface to be measured, but means the direction in which the shape is desired to be measured. Specifically, the axial direction for supporting the stylus sensor is often referred to as the optical axis direction when the object to be measured is an optical element or its mold.

Further, in the shape measuring instrument, the Lissajous waveform generated by the Lissajous waveform generating means is displayed by the display means.
Thereby, the appearance of the Lissajous waveform can be easily observed, and the vertex position can be detected with high accuracy.

  According to the present invention, it is possible to easily grasp the timing at which the direction of displacement of the stylus sensor switches to the opposite direction by observing the change in the Lissajous waveform. Can be detected.

(Embodiment)
Hereinafter, a shape measuring machine according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a state in which a workpiece (measurement object) made of, for example, a convex lens is attached to a shape measuring machine as an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a shape measuring machine, and reference numeral W denotes a workpiece.
The shape measuring machine 1 includes a measuring unit 2 that measures the workpiece W and a holding unit 3 that holds the workpiece W. The measuring unit 2 and the holding unit 3 face each other on the base 6. Has been placed.

The holding part 3 is provided with an attachment part (not shown). When the work W is attached to the attachment part, the work W and the measurement part 2 are arranged to face each other.
The measurement unit 2 includes a drive stage 7 installed on a base 6 and a measurement unit 8 for measuring the workpiece W.
The measurement unit 8 includes an operation shaft 11 formed in a column shape, and a hydrostatic bearing 12 that supports the operation shaft 11 in a state parallel to the base 6 toward the holding unit 3. The hydrostatic bearing 12 supports the operation shaft 11 in a non-contact manner by ejecting air, and biases the operation shaft 11 toward the tip side by adjusting the air ejection direction. It is supposed to be.

The operating shaft 11 is supported by the hydrostatic bearing 12 as described above, so that the operating shaft 11 reciprocates in the direction approaching / separating from the holding portion 3 (front-rear direction), that is, in the direction of the axis L. . A probe (stylus sensor) 13 made of a precision ruby ball is provided at the tip of the operating shaft 11.
Such a measurement unit 8 is installed on the drive stage 7. The drive stage 7 moves the measurement unit 8 in the X axis direction and the Y axis direction. Note that the X-axis direction is a direction orthogonal to the axis L direction and extending along the base 6. The Y-axis direction refers to a direction orthogonal to the extending direction of the base 6, that is, a direction orthogonal to the axis L and the X axis. The axis L direction is the Z-axis direction.

Further, a Z-axis direction detection unit (displacement amount measuring means) 16 for detecting the position coordinates of the operating shaft 11 in the Z-axis direction is provided on the drive stage 7. The Z-axis direction detection unit 16 outputs the result of detecting the position of the operating shaft 11 as a laser length measurement signal.
The position coordinates of the drive stage 7 in the X axis direction and the Y axis direction are detected by an XY axis direction detection unit 17 provided in the vicinity of the drive stage 7.

Further, the shape measuring machine 1 in the present embodiment includes a displacement meter amplifier (Lissajous waveform generating means, signal generating means) 18 connected to the Z-axis direction detecting unit 16. A laser length measurement signal having a wavelength λ is input to the displacement meter amplifier 18 from the Z-axis direction detector 16. The displacement meter amplifier 18 converts the input laser measurement signal as a sine wave signal and a cosine wave signal of analog voltage, and outputs each as an analog wave signal. The analog wave signals at this time are Vsinθ and Vcosθ, respectively. Here, V represents the amplitude voltage [V], and θ represents the phase of both waveforms. θ is represented by θ = 4πh / λ, where h is the position coordinate of the operating shaft 11 detected by the Z-axis direction detector 16. These analog wave signals are input to an A-D conversion circuit (analog / digital conversion circuit) 21. The A-D conversion circuit 21 converts the input analog wave signal into a digital signal and outputs it as a digital wave signal. That is, the A-D conversion circuit 21 functions as a Lissajous waveform generation unit and an A-D conversion unit.

  Further, the A-D conversion circuit 21 is connected to a computer 22 having a control unit (Lissajous waveform generating means, processing means) 23 for performing various controls and a monitor (display means) 26 for displaying waveforms and the like. The digital wave signal from the A / D conversion circuit 21 is input to the control unit 23. The control unit 23 performs two-dimensional display processing of the input digital wave signal as a Lissajous waveform, and inputs it to the monitor 26 as an image signal. The monitor 26 receives the image signal and displays a Lissajous waveform (shown in FIG. 4) corresponding to the displacement amount of the probe 13 with the horizontal coordinate X = V · sin θ and the vertical coordinate Y = V · cos θ. It has become.

Next, the operation of the shape measuring instrument 1 in the present embodiment configured as described above will be described.
First, the workpiece W to be measured is attached to the holding portion 3 via the attachment portion. Then, as will be described later, when the probe 13 is scanned in the Y-axis direction and viewed from the Y-axis direction, the position where the workpiece W protrudes most in the Z-axis direction toward the measurement unit 2, that is, from the Y-axis direction. The vertex position P at the maximum height in the Z-axis direction when viewed is detected. Then, the probe 13 is scanned in the X-axis direction so as to pass through the vertex position P. During this scanning, the coordinate position of the working shaft 11 in the Z-axis direction, that is, the displacement amount of the probe 13 in the Z-axis direction is measured. At the same time, the amount of displacement of the probe 13 in the X-axis direction is measured by the XY-axis direction detection unit 17. Thereby, the surface shape of the workpiece | work W is measured.

Here, the vertex position P is detected as follows.
That is, after the work W is attached to the holding unit 3, the drive stage 7 is driven, and the measurement unit 8 is placed below the optical axis C passing through the apex position P (on the base 6 side) as shown in FIG. Move to a predetermined position. At this time, the probe 13 is also disposed below the optical axis C. The direction in which the optical axis C faces is the height direction in which the workpiece W is to be measured when held by the holding unit 3. Then, air is ejected from the hydrostatic bearing 12 in a predetermined direction, and the operating shaft 11 is urged in the distal direction. Thereby, the operating shaft 11 moves in the forward direction, and the probe 13 contacts the surface of the workpiece W at a certain timing. The first contact point between the probe 13 and the workpiece W is referred to as an initial contact point. In the state of contact, the drive unit 7 moves the measurement unit 8 upward in the Y-axis direction. Then, the contact point between the probe 13 and the workpiece W sequentially moves toward the vertex position P, and the probe 13 moves along the surface of the workpiece W.

  At this time, the operating shaft 11 moves in a direction (backward direction) away from the workpiece W via the probe 13. Then, the coordinate position of the operating shaft 11 is sequentially detected by the Z-axis direction detection unit 16, and laser length measurement signals are sequentially input to the displacement meter amplifier 18. Then, as described above, the analog wave signal is sequentially input to the A / D conversion circuit 21 by the displacement meter amplifier 18, and the digital wave signal is sequentially input to the control unit 23 by the A / D conversion circuit 21. Further, an image signal from the control unit 23 is input to the monitor 26, and a Lissajous waveform 27 is displayed on the monitor 26 as shown in FIG.

The Lissajous waveform 27 is drawn as an arc-shaped trajectory by the point image rotating around the origin 28 according to the movement of the probe 13 in the Z-axis direction. The direction of rotation will change. Further, the rotational speed of the point image forming the Lissajous waveform 27 is proportional to the displacement increasing speed of the probe 13, and when the probe 13 is moving on a slope with a gradual change of the workpiece W surface, The rotational speed of the point image is low, while the rotational speed is high when moving on a steep slope. This is due to the following circumstances. As described above, the phase θ of the analog wave signal is expressed as θ = 4πh / λ. However, when the position coordinate of the operating shaft 11 at the initial contact point is h ₀ and the displacement therefrom is Δh (t), θ = 4π (h ₀ + Δh (t)) / λ. At this time, the locus of the point (X, Y), that is, the point (V · sin θ, V · cos θ) draws a circle with a radius V with an initial phase of 4πh ₀ / λ. The rotational direction is determined by the positive / negative of the differential coefficient of Δh (t), and the rotational speed is determined by the absolute value thereof.

Now, while the contact point between the probe 13 and the workpiece W is moving from the initial contact point to the apex position P, the probe 13 moves backward, so the point image is shown in FIG. In this manner, it rotates and moves clockwise around the origin 28.
When the measuring unit 8 is further moved upward in the Y-axis direction, the contact point is arranged at the apex position P as shown in FIG. In the vicinity of the vertex position P, since the inclination of the surface of the workpiece W is gentle, the rotational speed of the point image also becomes gentle, and when it is arranged at the vertex position P, the rotational movement stops. Then, when the measurement unit 8 is further moved in the same direction, the contact point moves from the apex position P to the measurement end position located above the optical axis C as shown in FIG. While the contact point is moving from the vertex position P to the measurement end position, the probe 13 moves in the forward direction, so that the point image rotates counterclockwise as shown in FIG. . That is, when the probe 13 exceeds the vertex position P, the point image rotates backward at that moment.
In this way, the scanning of the probe 13 is adjusted by driving the drive stage 7 while observing the rotation direction and speed of the point image on the monitor 26. And the vertex position of the workpiece | work W is detected by finding the state which stops from the clockwise rotation of a point image, and switches to reverse rotation.

As described above, the vertex position P of the workpiece W can be found graphically by observing the change of the point image of the Lissajous waveform 27. Therefore, the vertex position P can be detected with high accuracy and without reducing the display resolution of the application screen.
Further, when the shape measuring instrument 1 has an error factor such as vibration, the point image of the Lissajous waveform 27 is displayed with a certain amplitude width, but the point image has a substantially constant amplitude width. Since it is drawn in an arc as a whole, it is possible to find a reversal of the rotation direction macroscopically. Therefore, vertex detection can be easily performed even under vibration.

In the present embodiment, the computer 22 is provided. However, instead of this, as shown in FIG. 9, an oscilloscope 31 having a control unit 23 and a display unit (display unit) 31a may be provided.
In this embodiment, the vertex detection is performed by moving the probe 13 in the Y-axis direction. However, the workpiece W or both the probe 13 and the workpiece W may be moved, and the movement direction is the X-axis. It may be a direction.
Furthermore, in this embodiment, the output signal from the displacement measuring means is the laser length measurement signal, but the present invention is not limited to this.

In this embodiment, the convex lens is measured. However, the present invention is not limited to this, and a concave lens may be used. In this case, the apex position is a position at which the workpiece W sinks most forward when viewed from the Y-axis direction, that is, a position at the minimum height in the Z-axis direction when viewed from the Y-axis direction. In this case, it goes without saying that the moving direction of the probe 13 and the rotation direction of the point image are opposite to those described above.
Further, the object to be measured may be other than a lens, and for example, a mold for molding an optical element may be used.
Moreover, although the material of the probe 13 is ruby, it is not limited to this, and may be diamond, glass, sapphire, ceramics, or the like.
The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

It is a figure which shows one Embodiment of the shape measuring machine which concerns on this invention, Comprising: It is a side view which shows a mode that the measurement part and the holding | maintenance part were installed in the base. It is explanatory drawing which shows a mode that the displacement meter amplifier, AD conversion circuit, and computer in this embodiment were connected. It is explanatory drawing which shows a mode when the contact point of a probe and a workpiece | work is below the vertex position. It is explanatory drawing which shows the Lissajous waveform in FIG. It is explanatory drawing which shows a mode when the contact point of a probe and a workpiece | work exists in a vertex position. It is explanatory drawing which shows the Lissajous waveform in FIG. It is explanatory drawing which shows a mode when the contact point of a probe and a workpiece | work exists above a vertex position. It is explanatory drawing which shows the Lissajous waveform in FIG. It is explanatory drawing which shows a mode that the oscilloscope was connected instead of the computer of FIG.

Explanation of symbols

1 Shape measuring machine 13 Probe (stylus sensor)
16 Z-axis direction detector (displacement measuring means)
18 Displacement amplifier (Lissajous waveform generating means, signal generating means)
21 AD conversion circuit (Lissajous waveform generation means, AD conversion means)
23 Control unit (Lissajous waveform generating means, processing means)
26 Monitor (display means)
27 Lissajous waveform 31a Display section (display means)
W Workpiece (object to be measured)

Claims (1)

In a state where the stylus sensor is in contact with the surface of the object to be measured, the object to be measured and the stylus sensor are relatively scanned, and the object to be measured in the height direction to be measured during the scan is scanned. A shape measuring machine for measuring a surface shape of the object to be measured by a displacement amount of a stylus sensor,
Displacement amount measuring means for measuring the displacement amount of the stylus sensor in the height direction to be measured and outputting a length measurement signal ;
A Lissajous waveform generating means for generating based rather Lissajous waveform to the is shift measuring means or RaIzuru force said measurement signal,
The Lissajous waveform generating means is electrically connected, and the Lissajous waveform generated by the Lissajous waveform generating means is input, and based on the Lissajous waveform, a predetermined value is determined according to the movement of the stylus sensor relative to the object to be measured. Display means for displaying a locus of a point image rotating around the origin;
Equipped with a,
The rotation direction of the point image displayed on the display means is reversed when the stylus sensor that scans the surface of the measurement object passes through the apex of the measurement object. Shape measuring instruments.

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