JP2021092523A - Noncontact shape-measuring device - Google Patents

Abstract

To provide a noncontact shape-measuring device capable of measuring even a small inner diameter of several mm or less.SOLUTION: Since a light axis K of a laser probe mechanism 11 is inclined relative to X axis, an inner surface shape can be measured by applying laser beams L into a holding hole 2 having a small inner diameter. Since no mirrors inserted into the holding hole 2 are used, even a small inner diameter of several mm or less can be measured. By scanning a measurement work in the Z direction or rotating it in the θ direction, the roundness and diameter of the holding hole 2 or the cross-sectional contour and three-dimensional shape can be measured.SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-contact shape measuring device.

It is known that a laser probe type non-contact shape measuring device using laser autofocus can measure the shape and roughness of precision parts over a wide range with nano-level resolution. That is, as the three-dimensional orthogonal coordinate axis XYZ, the surface of the measurement work to be measured is scanned in the XY direction while autofocusing in the Z direction with the laser beam of the laser probe having the Z axis as the optical axis. , The structure is such that measurement data regarding the surface shape of the measurement work is acquired from the amount of movement of the objective lens of the autofocus optical system.

Recently, a mirror that reflects laser light at a right angle is provided on the objective lens side to convert the optical axis of the laser probe in the X direction, and the mirror is inserted into a hole or the like of a measuring workpiece to automatically detect the inner surface thereof. A technique for measuring the inner surface shape while focusing is also known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-2573

However, in such a conventional technique, since the mirror is inserted into the hole of the measuring work to measure the inner surface shape, there is a limitation on the inner diameter that can be measured from the size of the inserted mirror. It was not possible to measure the inner diameter as small as mm or less.

The present invention has been made focusing on such a related technique, and an object of the present invention is to provide a non-contact shape measuring device capable of measuring a small inner diameter of several mm or less.

According to the first technical aspect of the present invention, the three-dimensional orthogonal coordinate axis XYZ is defined, and the objective lens installed on the optical axis and the light irradiation for irradiating the objective lens with a laser beam parallel to the optical axis. A laser probe mechanism is composed of a means and an optical position detecting means that irradiates the surface of the measurement work through the objective lens, is reflected there, and receives the laser light that has passed through the objective lens again, and the position from the optical position detecting means. A non-contact shape measuring device provided with a focusing means for moving the entire laser probe mechanism in the X direction so that the focus of the laser beam is aligned with the surface of the measurement work based on the signal, and the optical axis of the laser probe mechanism is X. It is characterized in that it is inclined with respect to the X axis in a vertical plane including the axis and the Z axis.

According to the second technical aspect of the present invention, the Z-direction moving means for moving the measurement work relative to the laser beam in the Z direction and the relative θ-direction centered on the θ-axis along the Z-direction. It is characterized by providing a means for moving in the θ direction to rotate.

According to the third technical aspect of the present invention, the magnification of the objective lens is 50 times, and the inclination angle of the optical axis of the laser probe mechanism with respect to the X axis is 45 degrees or less.

According to the first technical aspect of the present invention, since the optical axis of the laser probe mechanism is inclined with respect to the X axis, if there is a hole having a small inner diameter on the surface of the measuring work, the laser beam is used. The inner surface shape can be measured by irradiating the inside of a hole or the like. Since a mirror to be inserted into a hole or the like is not used, a small inner diameter of several mm or less can be measured.

According to the second technical aspect of the present invention, since the means for moving in the θ direction is provided, the two-dimensional shape (roundness and diameter) of the inner circumference is measured by rotating around the θ axis. Can be done. Further, since the Z-direction moving means is provided, it is possible to obtain the cross-sectional contour data of the inner circumference by scanning in the Z direction and using the θ-axis as the step axis.

According to the third technical aspect of the present invention, it is possible to maintain a constant return light and prevent a decrease in focus speed.

The schematic which shows the non-contact shape measuring apparatus. Sectional drawing which shows the barrel which housed a lens. Sectional view showing the barrel. Explanatory drawing which shows the maximum measurable tilt angle. The graph which shows the measurement result of the inner circumference roundness of 4 steps of a barrel.

1 to 5 are views showing a preferred embodiment of the present invention.

FIG. 1 shows a non-contact shape measuring device according to the present embodiment, in which XY is two directions orthogonal to each other on a horizontal plane, X is an autofocus (AF) direction, and Y is a scanning direction. Z is in the vertical direction. θ is the rotation direction of the measuring work centered on the θ axis along the Z direction.

In this embodiment, the barrel 1 of the camera lens for a smartphone is used as the measurement work. The camera lens has a structure in which five aspherical lenses 3 to 7 are incorporated in the holding hole 2 of the barrel 1. In the case of aspherical lenses 3 to 7, the amount of eccentricity of each lens greatly affects the optical performance. In order to reduce the amount of eccentricity, the fitting of the inner diameter of the holding hole 2 of the barrel 1 and the outer diameter of the lens must be incorporated with an accuracy of μm level.

For that purpose, it is necessary to measure the diameter, roundness, and coaxiality of the multi-stage inner diameter of each lens at the submicron level. Further, the lens that serves as the reference of the optical axis is the lowest lens in the multi-stage lens, and high accuracy is required for measuring the inner peripheral radius shape of the bottom of Valles 1 and the contour shape of the diaphragm below it. The barrel 1 is several millimeters in size and is made of a black resin material with low reflectance. Since the wall thickness is thin, high-precision measurement cannot be performed with the conventional contact type.

The barrel 1 is set on a rotating stage (moving means in the θ direction) 8 that is rotatable in the θ direction. The rotary stage 8 is mounted on a Y-axis stage 9 that is slidable in the Y direction, and the Y-axis stage 9 is mounted on a surface plate 10.

The barrel 1 is irradiated with laser light L as a laser probe from the laser probe mechanism 11. The laser probe mechanism 11 includes an objective lens (50 times) 12 installed on the optical axis K, a semiconductor laser irradiation device (which constitutes a light irradiation means) 13 for irradiating the laser light L, and an objective lens 12 for irradiating the laser light L. A beam splitter (which constitutes a light irradiation means) 14 that reflects to the side and is parallel to the optical axis K, is irradiated to the inner surface of the barrel 1 via the objective lens 12, is reflected there, and passes through the objective lens 12 and the beam splitter 14 again. It includes an AF sensor (light position detecting means) 15 that receives the laser light L, and an imaging lens 16 that is arranged immediately before the AF sensor 15.

The laser probe mechanism 11 is mounted on the X-axis stage 17 as a focusing means in an inclined state as a whole, and the X-axis stage 17 is mounted on the Z-axis stage (Z-direction moving means) 18. The X-axis stage 17 can be moved in the Z direction by the Z-axis stage 18, and can be moved in the X direction (focus direction) with respect to the Z-axis stage 18 together with the laser probe mechanism 11. A 10 nm linear scale is attached to the X-axis stage 17, the Y-axis stage 9, and the Z-axis stage 18.

The rotary stage 8, the Y-axis stage 9, and the Z-axis stage 18 are controlled by the stage controller 22. The stage controller 22 outputs a signal for moving each stage in each direction, and outputs the positions of the barrel 1 in the θ direction, the X direction, the Y direction, and the Z direction to the main controller 21.

The laser probe mechanism 11 is mounted on the X-axis stage 17 at an inclination angle G of 45 degrees with respect to the X-axis with the objective lens 12 side down in a vertical plane whose optical axis K includes the X-axis and the Z-axis. It is fixed. The inclination angle G can be changed by moving the laser probe mechanism 11 with respect to the X-axis stage 17 along an arc rail (not shown) provided on the X-axis stage 17.

The laser beam L is emitted from the objective lens 12 into the holding hole 2 of the barrel 1 from diagonally above along the optical path in the vertical plane including the X-axis and the Z-axis, and is reflected on the inner surface thereof. The laser beam L reflected on the inner surface of the barrel 1 passes through the beam splitter 14 from the objective lens 12 again, passes through the imaging lens 16, and reaches the AF sensor 15.

The AF sensor 15 is composed of sensor units α and β divided into upper and lower parts about the optical axis K of the objective lens 12. The outputs from the two sensor units α and β are input to the AF controller 20 via the comparator (differential amplifier) 19. The AF controller 20 outputs the signals of the two sensor units α and β to the main controller 21.

Further, the AF controller 20 moves the entire laser probe mechanism 11 in the focus direction (X direction) by the X-axis stage 17 so that the outputs from the two sensor units α and β of the AF sensor 15 are equal. From the amount of movement in the X direction at that time, the position information in the focus direction of the inner surface of the holding hole 2 of the barrel 1 can be detected.

Since the laser probe mechanism 11 is vertically movable by the Z-axis stage 18 via the X-axis stage 17, the laser beam is moved up and down with respect to the inner surface of the holding hole 2 of the barrel 1 by moving the entire laser probe mechanism 11 up and down. You can also hit L.

Since the laser probe mechanism 11 is inclined, the laser beam L is irradiated into the holding hole 2 of the barrel 1 as it is, and the inner surface thereof can be measured (FIG. 3). The θ-axis that penetrates the center of the holding hole 2 along the Z direction is used as the step axis, and the cross-sectional measurement is performed in the vertical direction of the holding hole 2 by the Z-direction scan measurement at the θ-axis 0 degree, and then the θ-axis is rotated 180 degrees. Similarly, the cross section of the opposite surface is measured by the Z-direction can measurement. The cross-sectional contour data of the inner circumference can be obtained by converting the data into polar coordinates based on the θ-axis and combining them. It is also possible to measure the three-dimensional shape of the inner surface of the holding hole 2.

Next, the inclination angle G will be examined. FIG. 4 shows an example of the barrel 1 when the light L enters the objective lens 12 along the optical axis K and the surface roughness is at the nm level and scattered light is not generated, and the maximum measurable inclination thereof is shown. The angle A3 is expressed by the following equation.

A3 <(α / 2) + (b / 4)
Since the 50x objective lens 12 used in this embodiment has a half-opening angle (a) = 30 degrees and a focusing angle (b) = 40 degrees, the maximum tilt angle A3 = 25 degrees. However, since scattered light is generated on the inner surface of the barrel 1 having a surface roughness of several tens of nm or more, the AF sensor 15 can capture the scattered light and measure the inclined surface having the measurable limit inclination angle A3 or more. .. For example, when the cross-sectional shape of a pin gauge having a surface roughness Ra = 0.1 was measured, it was possible to measure up to an inclined surface of ± 88 degrees. However, as the tilt angle increases, the return light of the scattered light decreases, so that the S / N decreases and the focus speed decreases. Considering them, it is better not to exceed the inclination angle G of 45 degrees. When the objective lens 12 is 50 times (WD = 10.5 mm) and the inclination angle is 45 degrees, it is possible to measure the holding hole 2 having an inner diameter and depth of 7 mm or less in the barrel 1.

FIG. 5 shows an example of a barrel having a structure for accommodating four aspherical lenses, and is the result of measuring the inner surface of each of the four stages corresponding to each lens in the holding hole. In each case, the deviation was 0.8 μm or less, and the roundness was good.

1 barrel (measurement work)
8 Rotating stage (means for moving in the θ direction)
9 Y-axis stage (Y-direction moving means)
11 Laser probe mechanism 12 Objective lens 13 Semiconductor laser irradiation device (light irradiation means)
14 Beam splitter (light irradiation means)
15 AF sensor (optical position detecting means)
17 X-axis stage (focusing means)
18 Z-axis stage (Z-direction moving means)
L Laser light K Optical axis G Tilt angle

A3 <( a / 2) + (b / 4)
Since the 50x objective lens 12 used in this embodiment has a half-opening angle (a) = 30 degrees and a focusing angle (b) = 40 degrees, the maximum tilt angle A3 = 25 degrees. However, since scattered light is generated on the inner surface of the barrel 1 having a surface roughness of several tens of nm or more, the AF sensor 15 can capture the scattered light and measure the inclined surface having the measurable limit inclination angle A3 or more. .. For example, when the cross-sectional shape of a pin gauge having a surface roughness Ra = 0.1 was measured, it was possible to measure up to an inclined surface of ± 88 degrees. However, as the tilt angle increases, the return light of the scattered light decreases, so that the S / N decreases and the focus speed decreases. Considering them, it is better not to exceed the inclination angle G of 45 degrees. When the objective lens 12 is 50 times (WD = 10.5 mm) and the inclination angle is 45 degrees, it is possible to measure the holding hole 2 having an inner diameter and depth of 7 mm or less in the barrel 1.

Claims (3)

The three-dimensional orthogonal coordinate axis XYZ is defined,
An objective lens installed on the optical axis, a light irradiation means for irradiating a laser beam parallel to the optical axis toward the objective lens, and an objective lens that is irradiated on the surface of the measurement work via the objective lens, reflected there, and again. A laser probe mechanism is constructed from an optical position detecting means that receives the laser light that has passed through the device.
A non-contact shape measuring device provided with a focusing means for moving the entire laser probe mechanism in the X direction so that the focus of the laser beam is aligned with the surface of the measuring workpiece based on the position signal from the light position detecting means.
A non-contact shape measuring device characterized in that the optical axis of the laser probe mechanism is inclined with respect to the X axis in a vertical plane including the X axis and the Z axis. It is characterized by providing a Z-direction moving means that moves the measurement work relative to the laser beam in the Z direction and a θ-direction moving means that rotates the measuring work relatively in the θ direction around the θ axis along the Z direction. The non-contact shape measuring device according to claim 1. The non-contact shape measuring device according to claim 1 or 2, wherein the magnification of the objective lens is 50 times, and the inclination angle of the optical axis of the laser probe mechanism with respect to the X axis is 45 degrees or less.

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