JPH0592623U - Three-dimensional shape measuring device - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the position error and improve the measurement accuracy. A laser light source, an optical component that splits incident light into two directions, an objective lens for converging the emitted light of the laser light source on a measurement target, and a drive unit that moves the objective lens in the optical axis direction. , A polarized beam splitter and a 1/4 wavelength plate on which the first reflected light from the measurement target is incident through the objective lens, and a light incident on the polarized beam splitter and the 1/4 wavelength plate. Again, a plane mirror for entering the measuring object through the objective lens,
A focus position detection optical system that detects a focus error of the objective lens from the divergence angle of the second reflected light from the measurement object and returns the focus error to the position of the objective lens to always bring the focus state.
A stage that relatively moves the object to be measured and the optical system in a plane perpendicular to the optical axis and outputs the displacement, a displacement in the optical axis direction of the objective lens, and a displacement of the stage. A signal processing device for obtaining and displaying the shape of the measurement target from the output is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a three-dimensional shape measuring apparatus that measures the three-dimensional shape of an object in a non-contact manner, and more particularly to an apparatus that reduces the influence of the inclination of the measurement surface.

[0002]

[Prior Art]

 FIG. 2 is a block diagram showing an example of a three-dimensional shape measuring apparatus using the astigmatism method. In FIG. 2, 1 is a laser light source that outputs linearly polarized laser light, 2 is a half mirror that splits incident light into two directions of transmitted light and reflected light, and 3 is for focusing the laser light on the DUT 4. Objective lens, 5 is a stage for scanning the DUT 4 in the directions perpendicular to the optical axis (x and y directions), and 6 is a drive for moving the objective lens 3 in the optical axis direction (z direction). Equipment, 7 and 8 are convex lenses for focusing the reflected light from the DUT 4, cylindrical lenses, and 9 are the light focused by the convex lenses 7 and the cylindrical lenses 8 and are converted into four electric signals. The four-division photodiode 10 detects the focus error of the objective lens 3 from the electric signal from the four-division photodiode 9, moves the driving device 6 to perform focusing, and scans the stage 5 to generate a three-dimensional signal. Signal processing device for moving Is.

In such a configuration, the light output from the laser light source 1 passes through the half mirror 2, is condensed by the objective lens 3, is irradiated to the DUT 4, and is reflected. The reflected light passes through the objective lens 3 and is reflected by the half mirror 2. The reflected light is incident on the focus error detection optical system using the astigmatism method, which is composed of the convex lens 7, the cylindrical lens 8 and the 4-division photodiode 9, and is defocused on the DUT 4 by the 4-division photodiode 9. Is detected, the objective lens 3 is moved by the driving device 6 to adjust the focus. The movement of the driving device 6 at this time is used as a displacement (= height) signal in the Z direction, and the displacement output when the DUT 4 is scanned in the x and y directions by the stage 5 is detected by the signal processing device 10. The three-dimensional shape of the measured object was sought.

[0004]

[Problems to be solved by the device]

 However, in the three-dimensional shape measuring apparatus shown in the above-mentioned prior art, when the DUT 4 is tilted, the beam is deviated from the center on the 4-division photodiode 9, which causes a measurement error. ..

The present invention has been made in view of the above-mentioned problems of the prior art, and an optical axis of reflected light from an object to be measured is irradiated by irradiating the object to be measured with polarized light twice. The object of the present invention is to provide a three-dimensional shape measuring apparatus in which the position error is reduced by keeping the constant value constantly and the measurement accuracy is improved.

[0006]

[Means for Solving the Problems]

 The structure of the present invention for solving the above-mentioned problems is a laser light source, an optical component that splits incident light into two directions, an objective lens for converging the emitted light of the laser light source on a measurement target, and this objective. A drive unit for moving the lens in the optical axis direction, a polarization beam splitter and a quarter wave plate on which the first reflected light from the measurement target is incident through the objective lens, and the polarization beam splitter and 1 A plane mirror for causing the light incident on the / 4 wavelength plate to enter the measurement object again through the objective lens, and the focus error of the objective lens from the divergence angle of the second reflected light from the measurement object. And the focus position detection optical system that always returns to the position of the objective lens to keep in focus, and the measurement target and the optical system move relatively in a plane perpendicular to the optical axis. And its displacement And a signal processing device for displaying and obtaining the shape of the object to be measured from the displacement of the objective lens in the optical axis direction and the displacement output of the stage. It is a thing.

[0007]

[Action]

 According to the present invention, the optical axis of the reflected light is made to coincide with the optical axis of the incident light by irradiating the DUT with light twice using polarized light. Therefore, even if the object to be measured is tilted, it is possible to reduce the deviation of the light spot position on the four-division photodiode.

[0008]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the three-dimensional shape measuring apparatus of the present invention. In FIG. 1, the same elements as those in FIG. 2 are designated by the same reference numerals, and overlapping description will be omitted. In FIG. 1, 11 is a polarization beam splitter for splitting light into reflected light and transmitted light according to the polarization state, 12 is a quarter-wave plate for converting linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light. , 13 are plane mirrors.

In such a configuration, the light emitted from the laser light source 1 passes through the half mirror 2 and the polarization beam splitter 11. The polarization of the laser light source 1 at this time is aligned with the direction of transmission through the polarization beam splitter 11. After that, the light is converted into circularly polarized light by passing through the quarter-wave plate 12, is condensed by the objective lens 3, and is irradiated onto the DUT 4. The reflected light passes through the objective lens 3 and the quarter-wave plate 12, is reflected by the polarization beam splitter 11, is incident on the plane mirror 13, and is reflected. The reflected light is reflected by the polarization beam splitter 11, passes through the quarter-wave plate 12, is condensed by the objective lens 3, and is irradiated onto the DUT 4. The reflected light passes through the objective lens 3, the quarter-wave plate 12, and the polarization beam splitter 11, is reflected by the half mirror 2, and enters the focus error detection optical system by the astigmatism method. In the focus error detection optical system based on the astigmatism method, the four-divided photodiode 9 is irradiated through the two lenses 7 and 8 and converted into an electric signal. The focus shift on the DUT 4 is measured by the signal processing device 10 from the beam shape on the four-division photodiode 9, and the objective lens drive mechanism 6 is moved to adjust the focus. The movement of the objective lens driving mechanism at this time is used as a displacement (= height) signal in the z direction, and the stage 5 is scanned in the x and y directions to measure the three-dimensional shape of the DUT 4.

As described above, in the above-described embodiment, the measured object is irradiated with the light twice by using the polarized light. Therefore, the optical axis of the reflected light can be aligned with the optical axis of the incident light, and even if the DUT is tilted, it is possible to reduce the deviation of the spot position of the light on the 4-division photodiode. The error can be reduced.

In the above embodiment, the movement of the objective lens in the optical axis direction may not be a displacement signal, but may be a defocus signal of the four-division photodiode as a displacement signal. In this case, it can be used as a non-contact probe for a three-dimensional shape measuring instrument that has been conventionally used. In other words, when this probe is brought closer to the object to be measured and a certain distance is reached, a trigger output is output from the zero-cross signal of the displacement signal. The three-dimensional measuring device can measure the surface shape by reading the scale value at that point in time by the trigger signal.

Further, instead of moving the measurement object in the direction perpendicular to the optical axis, the measurement object may be fixed and the entire optical system may be moved in the direction perpendicular to the optical axis (xy direction). It is possible.

[0013]

[Effect of the device]

 As described above in detail with reference to the embodiments, according to the present invention, the optical axis of the reflected light is changed to the optical axis of the incident light by irradiating the DUT with the light twice by using the polarized light. Match. Therefore, even if the object to be measured is tilted, it is possible to reduce the deviation of the light spot position on the four-division photodiode, and it is possible to realize a three-dimensional shape measuring apparatus with improved measurement accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a three-dimensional shape measuring apparatus of the present invention.

FIG. 2 is a conventional example of a three-dimensional shape measuring apparatus.

[Explanation of symbols]

 1 Laser Light Source 2 Beam Splitter 3 Objective Lens 4 Object to be Measured 5 Stage 6 Objective Lens Drive Mechanism 7 Convex Lens 8 Cylindrical Lens 9 4 Division Photodiode 10 Signal Processor 11 Polarization Beam Splitter 12 1/4 Wave Plate 13 Planar Mirror

Claims (1)

[Scope of utility model registration request] 1. A laser light source, an optical component for branching incident light into two directions, an objective lens for converging the emitted light of the laser light source on a measurement target, and a drive for moving the objective lens in the optical axis direction. Section, the first reflected light from the measurement target is incident through the objective lens, and the quarter-wave plate, and the polarization beam splitter and the quarter-wave plate are incident. The focus error of the objective lens is detected by detecting the focus error of the objective lens from the plane mirror for causing the light to enter the measurement target again through the objective lens and the divergence angle of the second reflected light from the measurement target. A focus position detection optical system that returns a position to always bring the object into focus, and a stage that relatively moves the measurement target and the optical system in a plane perpendicular to the optical axis and outputs the displacement. And the objective lens 'S in the optical axis direction of displacement and the stearyl - three-dimensional shape measuring apparatus according to claim from the displacement output of di it has a structure in which a signal processing device for determining and displaying the shape of the measurement target.