JP2010085395A - Optical position angle detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact, light, and precise optical position angle detector that irradiates the surface with spot light, detects the height of the surface by triangulation principles by forming an image of the reflection light on a PSD by a lens, measures the sectional shape of the surface by scanning the surface by spot light, and is not influenced by lens aberrations. <P>SOLUTION: The optical position angle detector includes: a light projection means for condensing light emitted from a light source 1 onto a target surface for scanning; a front side spherical lens 16a and rear side spherical lenses 16b, 16c for forming images of reflection light from the surface by scanning light; a half mirror 21 for dividing the reflection light into two systems; two light position detection means 18a, 18b having mutually different light axis distances; and an operation section for measuring a surface shape by inversely tracing rays from a detection signal from the detection means and lens data of respective spherical lenses 16a, 16b, 16c and hence calculating the positions and angles of reflection points on the surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an optical position angle detecting device that measures unevenness formed on a glossy surface object in a non-contact manner using light.

Various methods are conventionally used as a method for measuring irregularities on a surface object in a non-contact manner using light, and a typical method is a triangulation method. Furthermore, as what measures not only a surface position but a surface angle simultaneously, what was shown by patent document 1, for example is mention | raise | lifted.
This optical sensor includes a displacement measuring optical system and an inclination measuring optical system as shown in FIG. 4, and the displacement measuring optical system can detect the vertical displacement of FIG. 4 by the principle of triangulation. The tilt measuring optical system is configured to detect the tilt of the object in the detection area.

That is, in FIG. 4, the displacement measuring light 55 from the displacement measuring light projecting element 58 is transmitted through the dichroic mirror 57, then condensed by the light projecting lens 60 and irradiated onto the surface of the detection object 71. The displacement measuring light 55 reflected by the detection object 71 is collected by the light receiving lens 63 and selectively passed through the dichroic mirror 64 to form an image on the displacement measuring light receiving element 61. On the other hand, the tilt measurement light 56 from the tilt measurement light projecting element 59 is reflected by the dichroic mirror 57, then becomes a parallel light beam by the light projection lens 60, and irradiates the surface of the detection object 71. The tilt measurement light 56 reflected by the detection object 71 is collected by the light receiving lens 63, selectively reflected by the dichroic mirror 64, and collected on the tilt measurement light receiving element 62.

When the detection object 71 moves up and down in FIG. 4, the light collection position of the light receiving lens moves on the light receiving element 61 for displacement measurement. On the other hand, when the angle of the detection object changes, the light collection position of the light receiving lens moves on the light receiving element 62 for tilt measurement. Therefore, the position and inclination of the detection object 71 can be detected independently.

By moving the optical system and the surface object to be measured relative to each other, the vertical position and inclination of each point on the target surface can be known, and the cross-sectional shape or three-dimensional shape can be acquired by connecting the data. it can.

On the other hand, as shown in Patent Document 2, for example, the surface height is measured by scanning light.
FIG. 5 is a configuration diagram of an example of an optical position angle detection device using laser scanning. The laser light source 1 is, for example, a combination of a semiconductor laser and a collimation lens. On the target surface 6 placed on the conveyance stage 4 by an optical scanning unit that is a combination of the laser light source 1, the polygon scanner 2, and the scanning lens 3. It is to be scanned one-dimensionally.

The transport stage 4 moves in a direction orthogonal to the one-dimensional scanning direction of the laser beam by the optical scanning unit. Therefore, the laser light is two-dimensionally scanned with respect to the target surface 6 by one-dimensional scanning of the laser light by the optical scanning means and movement of the transport stage 4.

On the other hand, an imaging optical system 8 is disposed obliquely above and symmetrical to the optical scanning means with respect to the normal line of the target surface 6, and reflected light from the target surface 6 passes through the imaging optical system 8 as height measuring means. An image is formed on a one-dimensional PSD (optical position detector) 9.

The laser light imaged on the PSD 9 moves in accordance with the height of the position on the target surface 6 where the laser light is irradiated. As a result, from the PSD 9, the position of the laser light and the amount of reflected light from the target surface 6. In response to this, output signals A1 and B1 due to current flow.

An IV converter 10 is connected to the output terminals of the outputs A1 and B1 of the PSD 9, and the output of the IV converter 10 is converted into digital data by the A / D converter 11. A calculation of (A1−B1) / (A1 + B1) is performed to the calculation unit 7 and the light spot position in the PSD 9 is thereby detected.

FIG. 6 shows the principle of height measurement. Light from the light source is irradiated to the target surface 6 through the scanning lens 3. In a standard state, the reflected light enters the center of the PSD 9 via the imaging optical system 8. When the height of the target surface 6 is lowered by Z, the reflection point changes Y0, and light is incident on the PSD 9 at a Y displaced position multiplied by the magnification β of the imaging optical system. Therefore, the height displacement Z from the light spot position displacement Y detected by PSD can be calculated by the following equation.
Z = Y / (2βsinθ)

The above is the measurement of height by triangulation, but in the case of a continuous surface, there is an example of shape measurement by angle measurement, for example, the one shown in Patent Document 3.

FIG. 7 is a diagram showing the principle of angle measurement. The light condensed on the target surface 6 by the scanning lens 3 is re-imaged at the imaging point by the imaging optical system 8. Here, the magnification of the imaging optical system is β.

The reflected light is inclined by the angle θ2 = 2 · θ1 due to the inclination of the inclined angle θ1 of the target surface 6. This tilted light is also re-imaged at the same point by the imaging optical system 8. At this time, if the surface of the PSD 9 is arranged at a position away from the imaging point by a certain distance d in the optical axis direction, the incident position on the PSD 9 varies in proportion to the reflection angle θ2 on the surface.

Based on the variation amount X at this time, the reflection angle variation θ1 on the target surface 6 can be calculated by the following equation.
θ1 = (β · x) / (2 · d)
In this way, the inclination angle on the target surface is detected. The presence or absence of unevenness on the target surface 6 can be detected from the change in the inclination angle. The inclination angle can also be regarded as a differential value of the shape, so that the shape data can be created by integrating the obtained inclination angle data.

JP-A-8-240408 JP-A-6-167322 JP 2008-32669 A

In the first example above, the height and angle can be measured at the same time, but the angle detection beam is much larger than the height detection beam on the target surface, and the angle of fine irregularities cannot be measured was there.

In addition, in the formula used for height detection based on the above triangulation principle or angle detection by shifting the PSD from the focal point, an imaging point that is always conjugate with the reflection point no matter where the reflected light passes through the lens. Assuming convergence to one point. However, there is aberration in an actual lens, and the position of the light spot incident on the PSD varies depending on the position of the reflected light passing through the lens.

For example, even in the case of light reflected at a standard height in FIG. 6, the incident position on the PSD changes by δ when passing outside the lens. Therefore, the limit of measurement accuracy is determined by the residual aberration amount of the lens. Therefore, when trying to make an optical position angle detection device with high measurement accuracy, it is necessary to reduce the residual aberration of the lens. For this purpose, the number of lenses increases, and the lenses become larger, heavier, and cost increases. was there.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly accurate optical position angle detection device that is small and lightweight and is not affected by lens aberration.

In order to solve the above-described problem, an optical position angle detection device that irradiates a target surface with light from a light source, receives the reflected light, and measures the position and angle of the surface. An imaging optical system that forms an image of the reflected light, a half mirror that separates the reflected light into two, two optical position detection means at different optical axis distances from the imaging optical system, and the detection A calculation unit that specifies the position and direction of the light beam based on the detection signal from the means and calculates the position and angle of the reflection point on the target surface from the backtracking result of the light beam based on the lens data of the imaging optical system; It was set as the optical position angle detection apparatus characterized by having.

An optical position angle detection device that irradiates light on a target surface from a light source and receives the reflected light to measure the position and angle of the target surface, wherein the light emitted from the light source is Optical scanning means that scans in a line with respect to the image, an imaging optical system that forms an image of reflected light from the surface by the scanning light, a half mirror that separates the reflected light into two, and an imaging optical system Two optical position detection means at different optical axis distances, and the ray tracing result based on the lens data of the imaging optical system by specifying the position and direction of the light ray by the detection signal from the detection means An optical position angle detecting device having a calculation unit for calculating the position and angle of the reflection point on the target surface.

As described above, since the optical position angle detection device according to the present invention emits a single beam and uses the reflected light, the position and angle measurement points are the same, and the position resolution on the target surface can be increased. In addition, the position and direction of the reflected light beam are identified from the outputs of the two optical position detection means having different optical axis distances, and the position and angle of the reflection point are calculated by reverse ray tracing based on the lens data. The calculation of the reflection point is irrelevant, and there is no need for aberration reduction. Therefore, a single lens or the like can be used. Therefore, the lens system can be made small and light and low cost.
In addition to knowing not only the position of the reflection point, but also the reflection angle, it is possible to grasp the shape more accurately, and if it is a continuous surface, it is difficult to measure height by integrating the angle data by integrating the angle data. Measurement is also possible.

It is a block diagram of the optical position angle detection apparatus in Example 1 of this invention. It is a block diagram of the optical position angle detection apparatus in Example 2 of this invention. FIG. 6 is a configuration diagram of an optical position angle detection device in Embodiment 3. It is a block diagram of the height measuring apparatus of a prior art example. It is a block diagram of the scanning type height measuring apparatus of a prior art example. It is a figure explaining the height detection of the height measuring apparatus of a prior art example. It is a figure explaining the angle detection of the angle measuring apparatus of a prior art example.

Embodiments of the optical position angle detection device of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a configuration diagram of a first embodiment of the present invention. A semiconductor laser collimation light source 1 is disposed as a light source above the target surface 6, and laser light emitted from the semiconductor laser collimation light source 1 enters the light projecting lens 3, and the laser light converges on the target surface 6. And irradiated.

On the other hand, a front spherical lens 16a is arranged opposite to the regular reflection position of the laser beam irradiated on the target surface 6, and a half mirror 21 for dividing the light beam is arranged on the optical path, on each divided optical axis. The rear spherical lenses 16b and 16c having the same specifications are respectively disposed in the imaging optical system 8 together with the front spherical lens 16a.

Further, two-dimensional PSDs (Position Sensitiue Detectors) 18a and 18b are arranged as optical position detecting means at positions where the distances on the optical axis from the rear spherical lenses 16b and 16c are different from each other.

Detection signals from the PSDs 18a and 18b are sent to the arithmetic unit 7 via the I / V conversion circuit 10 and the A / D circuit 11 which are not shown in FIG. The calculation unit 7 calculates the light spot positions (X1, Y1) and (X2, Y2) on the PSDs 18a and 18b from the detection signals of the PSDs 18a and 18b.

The calculation principle will be described below. The PSD 18a is disposed on the front side of the normal lens imaging point, and the PSD 18b is disposed on the rear side. In a standard state, the reflected light is incident on the centers of the PSDs 18a and 18b. As an example, when the height and inclination of the target surface 6 change as shown in 6a, the reflected light beam proceeds as shown in the figure, and enters the PSD 18a at the height of Y1 and on the PSD 18b at the height of Y2.

FIG. 1B shows a diagram in which PSDs 18a and 18b are arranged on the same optical axis. If the positions and intervals of the PSDs 18a and 18b and the incident positions Y1 and Y2 of the light beam are known, the light beam on the optical system can be specified. Therefore, ray tracing calculation is performed in the opposite direction from the lens data of the imaging optical system 8 and the specified ray data, and the intersection position Y0 with the laser irradiation light and the ray angle θ immediately before it are obtained. In this way, the position and angle of the reflection point can be calculated with the same accuracy as in the conventional example regardless of the lens without aberration correction.

A specific method of ray tracing is generally performed as a means of optical design in the optical field and will not be described in detail here. For example, see Non-Patent Document 1 and the like.
"Optical Technology Handbook" (Asakura Shoten) 8.2.1 Ray Tracing Method

In this way, the height position and angle of the reflection point are calculated. Compared to the conventional example, even if it is a single lens, the amount of calculation for calculating the position and angle of the reflection point is enormous, but with the recent development of computer technology, it can be performed in a very short time. ing. If the calculation time is still too long, the position and angle of the reflection point corresponding to the output of each PSD 18a, 18b is calculated and stored in advance, and the data stored when the position of the light beam by each PSD is determined is stored. The calculation time is shortened by reading.

In this embodiment, a two-dimensional PSD is used as the optical position detection means. The PSD has advantages in that it outputs a position signal corresponding to the center of gravity of the light amount and does not require any calculation, and the response speed is fast. However, a plurality of light spots cannot be separated by a thin transparent film or the like. When measuring such an object, the response speed decreases, but a camera element such as a two-dimensional CCD can also be used as the optical position detection means. Even if there are a plurality of light spots by image processing of the camera output, it is possible to classify the spots, determine the center of gravity of each spot, and select one of them depending on the power. On the other hand, when there is a demand to make the response faster than PSD or to increase the sensitivity to the amount of light, it is possible to meet these demands by using a position detection type photomultiplier tube instead of PSD.

In this embodiment, one lens is provided before and after the half mirror, but this is to increase the lens opening. If the lens opening is small, only one front side or only two rear sides may be used. Is possible. Since the half mirror needs to match the optical system of transmitted light and reflected light, it is desirable to use a cube-type or thin-film type half mirror or beam splitter that does not change the optical path length due to reflection and transmission.

Although only one point can be measured at a time in this embodiment, a two-dimensional cross section or a three-dimensional solid shape can be measured by relatively moving the object and the optical system. As a relative moving method, there are a method of moving an object or an optical system on an XYZ stage, a method of rotating the object and moving the optical system in one direction, and the like.

  When the reflectance of the object greatly fluctuates, it is possible to control the power of the light source based on the light amount signal from the optical position detection means so that an appropriate amount of light enters the optical position detection means.

FIG. 2 shows a configuration diagram of the second embodiment of the present invention. A semiconductor laser collimation light source 1 is disposed as a light source above the target surface 6, and laser light emitted from the semiconductor laser collimation light source 1 enters the resonance scanner 2 k. When the resonance scanner 2k reciprocally vibrates, the scanned laser light is incident on the scanning lens 3, and the target surface 6 is irradiated with the laser scanning light. These resonant scanner 2k and scanning lens 3 constitute an optical scanning means.

On the other hand, a front cylindrical lens 8a having a curvature in a direction orthogonal to the scanning direction is arranged opposite to the regular reflection position of the laser scanning light irradiated on the target surface 6, and only the vicinity of the laser wavelength passes through the optical path. An interference filter 15 and a half mirror 21 for splitting the light beam are arranged, and rear cylindrical lenses 8b and 8c of the same specification are arranged on each of the divided optical axes, and together with the front cylindrical lens 8a, the imaging optical system 8 Configure.

Further, one-dimensional PSDs (Position Sensitiue Detectors) 9a and 9b are arranged as optical position detection means having sensitivity in the direction orthogonal to the scanning direction at positions where the distances on the optical axis from the rear cylindrical lenses 8b and 8c are different from each other. The electrode width of each PSD needs to be sufficiently long in the scanning direction corresponding to the scanning width. Position sensitivity exists between the electrodes, and the scanning direction and the position sensitivity direction are orthogonal to each other.

Detection signals from the PSDs 9 a and 9 b are sent to the arithmetic unit 7 via the I / V conversion circuit 10 and the A / D circuit 11. The calculation unit 7 calculates the light spot positions Y1 and Y2 on the PSDs 9a and 9b from the detection signals of the PSDs 9a and 9b.

The PSD 9a is disposed on the front side of the normal lens imaging point, and the PSD 9b is disposed on the rear side. If the positions and intervals of the PSDs 9a and 9b and the incident positions Y1 and Y2 of the light beam are known, the light beam on the optical system can be specified. Therefore, ray tracing calculation is performed in the opposite direction from the lens data of the imaging optical system 8 and the specified ray data, and the intersection position Y0 with the laser scanning light and the ray angle immediately before it are obtained. In this way, the position and angle of the reflection point in the PSD detection direction can be calculated with the same accuracy as in the conventional example regardless of the lens without aberration correction.

The imaging optical system of the present embodiment does not have a condensing function in the scanning direction. This is because the distance from the reflection point to the PSD is short, so that it is incident on the PSD without condensing. When it is necessary to collect light, a cylindrical lens that collects the scanning direction may be disposed behind the front cylindrical lens. The interference filter 15 has a function of limiting the spread of light in the scanning direction.

The reason why the cylindrical lens is used in this embodiment is that the PSDs 9a and 9b used are one-dimensional PSDs that have no sensitivity in the scanning direction. Because. A spherical lens can be used by using a two-dimensional PSD having sensitivity also in the scanning direction, a position detection type photomultiplier tube, and also using scanning position data from a resonance type scanner.

In this embodiment, one cylindrical lens is provided before and after the half mirror, but this is to increase the lens aperture. If the lens aperture is small, only one front lens or one rear lens can be used. It is configurable. Since the half mirror needs to match the optical system of transmitted light and reflected light, it is desirable to use a cube-type or thin-film type half mirror or beam splitter that does not change the optical path length due to reflection and transmission.

Next, FIG. 3 shows a configuration diagram of the third embodiment. FIG. 3 shows two two-dimensional PSDs 18a and 18b in which the resonance scanner 2k is replaced with a polygon scanner 2 in the scanning type optical position angle detection apparatus in the second embodiment, and the reflected light is separated after returning to the polygon scanner. It is made into the structure made to inject into.

Above the target surface, a semiconductor laser collimation light source 1 is disposed as a light source, and laser light emitted from the semiconductor laser collimation light source 1 enters the polygon scanner 2. As the polygon scanner 2 rotates, the scanned laser light is incident on the scanning lens 3 designed telecentrically, and the laser scanning light is irradiated onto the target surface.

The laser scanning light irradiated on the target surface 6 is reflected almost vertically on the target surface, and the scanning lens 3 and the polygon scanner 2 are reversed. Thereafter, the light is reflected by the beam splitter 12 on the optical path, and enters the two two-dimensional PSDs 18 a and 18 b via the imaging lens 17 and the half mirror 21. Detection signals from the PSDs 18 a and 18 b are sent to the calculation unit 7. In FIG. 3, the A / D conversion unit of the signal from the PSD 18b is omitted.

Reference numeral 14 denotes a quarter-wave plate, which can reduce the loss of light quantity by converting the direction of polarization of the going and returning directions by 90 ° and using the beam splitter 12 as a polarizing beam splitter.

The calculation unit specifies the position and direction of the detected light beam based on the signals from the PSDs 18a and 18b in the same manner as described above. From this, the light beam is traced based on the lens data of the imaging lens 17 and the scanning lens 3 and the reflection direction of the polygon scanner 2, and the intersection with the light projecting optical axis and the reflection angle are calculated. In this case, the angle intersecting with the light projection optical axis is very shallow, so it is difficult to calculate the height, but the reflection angle can be obtained accurately. Since the angle of the light projection optical axis varies depending on the reflection direction of the scanner, it is necessary to calculate in advance.

  In this embodiment, in order to stably reverse the reflected light of the target surface 6 in the scanning optical system, the scanning object focal plane side in the scanning lens is f, and the designed entrance pupil diameter is d. Sometimes it is desirable that the scanning lens be a telecentric optical system having an angle d / (2f) rad or less over the entire scanning width.

In this embodiment, the beams on the PSDs 18a and 18b are incident on a fixed position regardless of scanning. Therefore, the electrode lengths of the PSDs 18a and 18b are different from those in the first embodiment, although the beams are incident regardless of the scanning width. It only needs to be large enough. Since the beam positions on the PSDs 18a and 18b do not change depending on scanning, a two-dimensional PSD having beam position sensitivity in the vertical and horizontal directions can be used. Unlike the first embodiment, the inclination in the scanning direction is detected. be able to. Further, even when the imaging lens 17 and the scanning lens 3 that perform ray tracing are spherical lenses, ray tracing can be performed.

In the conventional example (Japanese Patent Laid-Open No. 2008-32669) for measuring the angle, only the aperture in the range in which the aberration is corrected can be used for reducing the aberration, but in this embodiment, as long as the size of the mirror permits. The aperture can be used up to a range where the aberration of the scanning lens is not corrected. In addition, if a cylindrical lens that also serves to correct the tilting of the scanner is disposed before and after the scanner, a large opening can be secured even with a thin mirror.

In Example 2 and Example 3, PSD can be replaced with a position detection type photomultiplier tube, and by this replacement, the amount of light source can be reduced or the surface of an object with low reflectance can be measured. Further, higher speed can be achieved.

Further, in the second and third embodiments, the polygon scanner and the resonant mirror scanner can be replaced with each other, and other scanners may be used, and by replacing them, compactness, high speed, reduction in surface tilt, linearization, etc. Can be achieved.

DESCRIPTION OF SYMBOLS 1 Light source 2 Polygon scanner 2k Resonance type scanner 3 Scanning lens 4 Conveying means 6 Target surface 7 Calculation part 8 Imaging optical system 8a Front cylindrical lens 8b, 8c Rear cylindrical lens 9, 9a, 9b One-dimensional PSD
10 I / V conversion circuit 11 A / D conversion circuit 12 Beam splitter 14 1/4 wavelength plate 15 Interference filter 16a Front spherical lens 16b, 16c Rear spherical lens 17 Imaging lenses 18a, 18b Two-dimensional PSD
21 Half mirror A1, A2, B1, B2, C1, C2, D1, D2 PSD signal output 55 Displacement measuring light 56 Tilt measuring light 57 Dichroic mirror 58 Displacement measuring light emitting element 59 Tilt measuring light projecting element 60 Optical lens 61 Displacement measuring light receiving element 62 Tilt measuring light receiving element 63 Light receiving lens 64 Dichroic mirror 71 Detected object

Claims (7)

An optical position angle detection device that irradiates light on a target surface from a light source, receives the reflected light, and measures the position and angle of the reflection point on the surface, and combines the reflected light from the surface by the irradiated light. An imaging optical system for imaging, a half mirror that separates reflected light into two, two optical position detection means at different optical axis distances from the imaging optical system, and a detection signal from the detection means And a calculation unit for calculating the position and angle of the reflection point on the target surface from the backtracking result of the ray based on the lens data of the imaging optical system by specifying the position and direction of the ray by An optical position angle detection device. 2. The optical position angle detection apparatus according to claim 1, wherein the three-dimensional shape of the target surface can be measured by two-dimensionally moving the positional relationship between the optical position angle detection apparatus and the target surface. An optical position angle detection device that irradiates light on a target surface from a light source, receives the reflected light and measures the shape of the surface, and emits light emitted from the light source in a line shape with respect to the surface An optical scanning means for scanning the light, an imaging optical system for imaging the reflected light from the surface by the scanning light, a half mirror for separating the reflected light into two, and an optical axis distance from the imaging optical system. Two light position detection means at different positions, and the position and direction of the light beam are determined by the detection signal from the detection means, and the result of the back tracking of the light beam based on the lens data of the imaging optical system is used. An optical position and angle detection device comprising: a calculation unit that calculates the position and angle of the reflection point. 4. The optical position angle detection apparatus according to claim 3, wherein the imaging optical system includes a cylindrical lens having no curvature in the scanning direction. 2. The imaging optical system is divided into front and rear parts, the front lens is disposed on the target surface side of the half mirror, and the rear lens is disposed on the optical position detection means side of the half mirror. 4 to 4 optical position angle detection devices. A beam splitter is provided on the light source side of the optical scanning means, and the light reflected from the target plane travels backward through the optical scanning means and reaches the beam splitter, and the optical path is separated by the beam splitter and passes through the imaging optical system and the half mirror. It is structured to be incident on two optical position detection means having different distances from the imaging optical system, and the optical position of the light beam is specified by the detection signal from the detection means and the scanning signal of the optical scanning means. An optical position angle detection apparatus comprising a calculation unit for calculating a position and an angle of a reflection point on a target surface from a result of reverse tracking of the light beam based on lens data of the system and optical scanning means. A calculation for obtaining the position and angle of the reflection point from the output from each light position detection means is performed in advance and stored in a memory, and in actual use, this is read out according to the output from each light position detection means. 7. The optical position angle detection device according to claim 1, wherein the position and angle of the reflection point are obtained.

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