CN112880585A - Non-contact shape measuring device - Google Patents

Abstract

The present invention relates to a non-contact shape measuring apparatus. Since the optical axis K of the laser probe mechanism 11 is inclined with respect to the X-axis, the shape of the inner surface of a holding hole 2 having a small inner diameter can be measured by irradiating a laser beam L into the holding hole. Since a mirror inserted into the holding hole (2) is not used, a small inner diameter of a few mm or less can be measured. The roundness, diameter, cross-sectional profile, and three-dimensional shape of the holding hole (2) can be measured by scanning the measurement workpiece in the Z direction or rotating the measurement workpiece in the theta direction.

Description

Non-contact shape measuring device

Technical Field

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

Background

As is well known, a laser probe type non-contact shape measuring apparatus using laser autofocus can measure the shape and roughness of a precision member with a resolution of the order of nanometers in a wide range. Namely, the structure is as follows: as the three-dimensional orthogonal coordinate axis XYZ, the surface of the measurement workpiece to be measured is scanned in the XY direction by the laser beam of the laser probe having the Z axis as the optical axis while performing autofocus in the Z direction, and measurement data relating to the surface shape of the measurement workpiece is acquired from the amount of movement of the objective lens of the autofocus optical system.

Recently, the following techniques are also known: a mirror for reflecting laser light at right angles is provided on the objective lens side, the optical axis of a laser probe is converted into the X direction, and the mirror is inserted into a hole portion or the like of a measurement workpiece, and the inner surface shape is measured while autofocusing is performed on the inner surface. Related art is exemplified in japanese patent laid-open publication No. 2012-2573.

Disclosure of Invention

However, in such a related art, since the inner surface shape is measured by inserting the reflecting mirror into a hole portion of the measurement workpiece, the inner diameter that can be measured is restricted by the size of the inserted reflecting mirror, and measurement of a small inner diameter of not more than several mm cannot be performed.

The present invention has been made in view of the above-described related art, and according to the present invention, it is possible to provide a noncontact shape measurement device capable of measuring a small inner diameter of not more than a certain mm.

According to the 1 st aspect of the present invention, there is provided a noncontact shape measuring apparatus defining three-dimensional orthogonal coordinate axes XYZ, the apparatus including a laser probe mechanism including an objective lens disposed on an optical axis, a light irradiation unit irradiating a laser beam parallel to the optical axis toward the objective lens, and a light position detection unit receiving the laser beam irradiated through the objective lens onto a surface of a measurement workpiece, reflected therefrom, and passed through the objective lens again, the noncontact shape measuring apparatus including a focusing unit moving the entire laser probe mechanism in an X direction based on a position signal from the light position detection unit so as to bring a focal point of the laser beam into coincidence with the surface of the measurement workpiece, the noncontact shape measuring apparatus being characterized in that the optical axis of the laser probe mechanism is inclined with respect to the X axis within a vertical plane including the X axis and the Z axis.

According to the invention of claim 2, the measuring device is characterized in that Z-direction moving means for moving the measuring workpiece relative to the laser beam in the Z-direction and θ -direction moving means for relatively rotating the measuring workpiece in the θ -direction around the θ -axis along the Z-direction are provided.

According to the 3 rd 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.

Drawings

Fig. 1 is a schematic view showing a non-contact shape measuring apparatus.

Fig. 2 is a sectional view showing a lens barrel accommodating a lens.

Fig. 3 is a sectional view showing the lens barrel.

Fig. 4 is an explanatory diagram showing that the maximum tilt angle can be measured.

Fig. 5 is a graph showing the measurement results of the inner circumference circularity of 4 steps of the lens barrel.

Detailed Description

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

Fig. 1 shows a noncontact shape measuring apparatus of the present embodiment, XY are two directions orthogonal on a horizontal plane, X is a control direction of Auto Focus (AF), and Y is a scanning direction. Z is the vertical direction. θ is the rotation direction of the measurement workpiece centered on the θ axis along the Z direction.

In this embodiment, the lens barrel 1 of the camera lens for a smartphone is used as a measurement workpiece. The camera lens has a structure in which 5 aspherical lenses 3 to 7 are fitted into a holding hole 2 of a lens barrel 1. In the case of the aspherical lenses 3 to 7, the decentering amount of each lens has a great influence on the optical performance. In order to reduce the amount of decentering, it is necessary to assemble fitting of the inner diameter in the holding hole 2 of the lens barrel 1 and the outer diameter of the lens with accuracy of the order of μm.

Therefore, it is necessary to measure the diameter, roundness, and coaxiality of the inner diameter of the plurality of steps into which each lens enters, on a submicron scale. Further, the lens serving as a reference of the optical axis is the lowermost lens among the lenses having a plurality of steps, and high accuracy is also required for measuring the inner peripheral R shape of the bottom portion of the lens barrel 1 and the contour shape of the diaphragm below the inner peripheral R shape. The lens barrel 1 is several mm in size and is made of a black resin material having low reflectance. Since the thickness is small, high-precision measurement cannot be performed by the conventional contact type.

The lens barrel 1 is mounted on a rotational stage (θ direction moving unit) 8 that is rotatable in the θ direction. The rotary stage 8 is mounted on a Y-axis stage 9 which is slidable in the Y direction, and the Y-axis stage 9 is mounted on a table 10.

The lens barrel 1 is irradiated with laser light L as a laser probe from a laser probe mechanism 11. The laser probe mechanism 11 includes: an objective lens (magnification of 50 times) 12 provided on an optical axis K, a semiconductor laser irradiation device (constituting a light irradiation unit) 13 that irradiates laser light L, a beam splitter (constituting a light irradiation unit) 14 that reflects the laser light L toward the objective lens 12 side and is parallel to the optical axis K, an AF sensor (light position detection unit) 15 that receives the laser light L irradiated to the inner surface of the lens barrel 1 through the objective lens 12, reflected therefrom, and passed through the objective lens 12 and the beam splitter 14 again, and an imaging lens 16 disposed immediately in front of the AF sensor 15.

The laser probe mechanism 11 is mounted on an X-axis stage 17 as a focusing unit in a state of being tilted as a whole together with the optical axis K, and the X-axis stage 17 is mounted on a Z-axis stage (Z-direction moving unit) 18. The X-axis stage 17 is movable in the Z direction by the Z-axis stage 18, and is movable in the X direction (focusing direction) with respect to the Z-axis stage 18 together with the laser probe mechanism 11. Linear rulers of 10nm are mounted on 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 a stage controller 22. The stage controller 22 outputs a signal for moving each stage in each direction, and outputs the positions of the lens 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 fixed to an X-axis stage 17 such that an optical axis K is inclined at an angle G of 45 degrees with respect to the X-axis in a vertical plane including the X-axis and the Z-axis with the objective lens 12 side down. The inclination angle G can be changed by moving the laser probe mechanism 11 relative to the X-axis stage 17 along an arc orbit, not shown, provided on the X-axis stage 17.

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

The AF sensor 15 is configured by vertically dividing the optical axis K of the objective lens 12 into two sensor portions α and β. The outputs from the 2 sensor units α, β are input to an AF controller 20 via a comparator (differential amplifier) 19. The AF controller 20 outputs signals of the 2 sensor units α and β to the main controller 21.

The AF controller 20 moves the entire laser probe mechanism 11 in the focusing direction (X direction) by the X-axis stage 17 so that the outputs from the 2 sensor units α and β of the AF sensor 15 are equal to each other. The positional information of the inner surface of the holding hole 2 of the lens barrel 1 in the focusing direction can be detected from the amount of movement in the X direction at this time.

Since the laser probe mechanism 11 is vertically movable by the Z-axis stage 18 via the X-axis stage 17, the entire body can be moved up and down, and the laser beam L can be irradiated so as to move in the vertical direction with respect to the inner surface of the holding hole 2 of the lens barrel 1.

Since the laser probe mechanism 11 is inclined, the laser beam L is directly irradiated into the holding hole 2 of the lens barrel 1, and the inner surface thereof can be measured (fig. 3). The section of the holding hole 2 in the up-down direction is measured by scanning measurement in the Z direction at 0 degrees of the θ axis, and then the section of the opposite surface is measured by scanning measurement in the Z direction by 180 degrees. By performing polar coordinate conversion on the data in accordance with the θ -axis reference and combining the data, the cross-sectional profile data of the inner periphery can be obtained. In addition, the three-dimensional shape of the inner surface of the holding hole 2 can also be measured.

Next, the inclination angle G is studied. Fig. 4 shows an example of the lens barrel 1 in a case where the surface roughness is in the order of nm and no scattered light is generated when the light L enters the objective lens 12 along the optical axis K, and the measurable maximum tilt angle a3 is expressed by the following expression (1).

A3＜(a/2)+(b/4) (1)

Since the half opening angle (a) of the 50-fold objective lens 12 used in the present embodiment is 30 degrees and the light converging angle (b) is 40 degrees, the maximum inclination angle a3 is 25 degrees. However, since scattered light is generated on the inner surface of the lens barrel 1 having a surface roughness of several tens nm or more, the AF sensor 15 can capture the scattered light and measure the inclined surface of the measurable limit inclination angle a3 or more. For example, when the cross-sectional shape of the pin gauge with the surface roughness Ra of 0.1 is measured, it is possible to measure an inclined surface of ± 88 degrees. However, as the tilt angle increases, the return light of the scattered light decreases, and therefore, the S/N decreases, and the focusing speed decreases. In view of these circumstances, it is preferable that the inclination angle G is not more than 45 degrees. When the objective lens 12 is 50 times (WD is 10.5mm) and the inclination angle is 45 degrees, the holding hole 2 having an inner diameter and a depth of 7mm or less in the lens barrel 1 can be measured.

Fig. 5 shows an example of a lens barrel having a configuration in which 4 aspherical lenses are accommodated, as a result of measuring the inner surfaces of 4 steps corresponding to each lens in the holding hole, respectively. The deviations were all 0.8 μm or less, and the circularity was good.

As described above, according to the technical aspect of the present invention, since the optical axis of the laser probe mechanism is inclined with respect to the X axis, when a hole portion or the like having a small inner diameter is formed on the surface of the measurement workpiece, the laser beam can be irradiated into the hole portion or the like to measure the inner surface shape. Since a mirror inserted into a hole or the like is not used, it is possible to measure a small inner diameter of not more than a few mm.

According to another aspect of the present invention, since the θ -direction moving means is provided, the two-dimensional shape (roundness, diameter) of the inner periphery can be measured by rotating about the θ axis. Since the Z-direction moving means is further provided, the cross-sectional profile data of the inner periphery can also be acquired by scanning in the Z-direction and setting the θ -axis as the step axis.

Further, by appropriately setting the tilt angle or the like, a constant return light can be maintained, and a decrease in the focusing speed can be prevented.

Claims (3)

1. A non-contact shape measuring device is provided,

three-dimensional orthogonal coordinate axes XYZ are defined,

a laser probe mechanism is constituted by an objective lens disposed on an optical axis, a light irradiation unit irradiating laser light parallel to the optical axis toward the objective lens, and an optical position detection unit receiving the laser light irradiated to the surface of the measurement workpiece through the objective lens, reflected there and passed through the objective lens again,

the non-contact shape measuring device comprises a focusing unit which moves the whole laser probe mechanism in the X direction based on the position signal from the optical position detecting unit so as to make the focal point of the laser coincide with the surface of the measured workpiece,

the non-contact shape measuring apparatus is characterized in that,

the optical axis of the laser probe mechanism is inclined with respect to the X-axis within a vertical plane containing the X-axis and the Z-axis.

2. The non-contact shape measuring apparatus according to claim 1,

a Z-direction moving means for moving a measurement workpiece relative to a laser beam in a Z direction and a theta-direction moving means for rotating the measurement workpiece relative to the Z direction in a theta direction around a theta axis along the Z direction are provided.

3. The non-contact shape measuring apparatus according to claim 1 or 2,

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.

Images