JP2597711B2 - 3D position measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a three-dimensional position measuring device capable of measuring a three-dimensional shape of a subject with high accuracy.

<Conventional Technology> For example, a technology for measuring distortion of a building, a storage tank, or the like with high accuracy is important from the viewpoint of maintenance. Here, the distortion is grasped as a change over time in the three-dimensional shape of the object, but in maintenance and inspection, a resolution of about several mm is required as a measurement accuracy, so a high-precision three-dimensional shape measurement technology is required. Is done.

By the way, conventionally, a moire method and a light cutting method are known as three-dimensional shape measurement techniques.

Here, in the moire method, as shown in FIG. 5, a first reference grating 51 and a second reference grating 52 are arranged so as to face an object 50 as a subject, and light emitted from a light source 53 is transmitted through a lens 54. By first
Through the reference grating 51, and image the reference grating 51
In addition to projecting the image of the grating on the second reference grating 52 via the lens 56 while projecting the image of the grating distorted according to the shape of the object 50 via the lens
The image is observed by the image sensor 58 through the, for example, a pattern 59 as shown in the figure is observed.

On the other hand, in the light section method, as shown in FIG. 6, a thin slit light 61 is projected on the surface of an object
The shape of the object 60 is measured by analyzing the slit image 62 deformed according to the surface shape of the object 60.

<Problems to be Solved by the Invention> However, when the shape of the object to be measured is measured with high accuracy by the above-described conventional method, there are the following problems.

In the above-described method, since the image projected on the object to be measured is a lattice pattern or a line image, the light source irradiates a relatively wide area, and thus sufficient illuminance may not be secured. In particular, when the reflectance of the object to be measured is low or the reflecting surface is inclined, a sufficient amount of light cannot be secured in the observation system, which may cause a decrease in the S / N ratio of the observed image and a decrease in measurement accuracy. There is.

The projected image of the grating or slit projected on the object to be measured may be distorted by the spherical aberration of the projection lens at the edge of the field of view, and the same occurs with the imaging lens. Can not.

Although the resolution of the image pickup device of the image pickup system affects the measurement accuracy, when a two-dimensional CCD camera is used as the image pickup device, the number of pixels is about 500 × 500, which limits the image resolution.

In view of such circumstances, an object of the present invention is to provide a three-dimensional position measuring device capable of performing high-accuracy three-dimensional shape measurement.

<Means for Solving the Problems> A three-dimensional position measuring apparatus according to the present invention that achieves the above object,
The light irradiating section irradiates the subject with parallel light or convergent light as probe light and the irradiation direction thereof is variable by rotation around two rotation axes, an imaging lens, and a light receiving element. A light detection unit that is variable by rotation about the rotation axis of the book, and detects the reflected light from the subject by performing rotation adjustment so that the image of the reflection point coincides with the optical axis;
A processing unit that detects the position of the reflection point based on the principle of triangulation from the emission direction of the probe light, the light receiving direction at the light detection unit, and the relative positional relationship between the light detection unit and the light irradiation unit. Thus, one rotation axis of the light irradiation unit and one rotation axis of the light detection unit coincide with a straight line connecting the rotation center of the light irradiation unit and the rotation center of the light detection unit, and the light receiving element Is a one-dimensional image sensor.

<Operation> The probe light emitted from the light irradiation unit is reflected by the subject, and when the reflected light is detected by the light detection unit, the light detection unit is rotated and adjusted so that the image of the reflection point coincides with the optical axis. I do.

Here, the emission direction and the light reception direction are detected based on the rotation position of the light irradiation unit and the rotation position of the light detection unit, and the position of the reflection point is determined based on the principle of triangulation based on the relative positional relationship between these directions. Is detected by the processing unit.

<Examples> Hereinafter, the present invention will be described based on examples.

FIG. 1 shows a configuration of a three-dimensional position measuring apparatus according to one embodiment.

As shown in the figure, in the light irradiation section A, the light emitted from the He-Ne laser light source 1 passes through a variable attenuator 2 and further passes through a beam expander 5 composed of lenses 3 and 4 to a mirror 6. And the emitted light is reflected by the subject 7
Image on the surface a. Here, the variable attenuator 2 is for preventing the light receiving lens of the observation system from fluctuating due to the influence of the inclination of the surface of the subject 7 and the reflectance. The expander 5 is used to reduce the divergence angle of the He-Ne laser beam, and moves the lens mounting stage 8 on which the lens 4 is mounted so that the beam diameter on the surface a is minimized. Has been adjusted. On the other hand, the mirror 6 is mounted on a rotary stage 9 and is driven by a motor 10. The rotation position of the mirror 6 is defined as a rotation angle θ which is the inclination of the reflected light from the optical axis.
Read by 11.

On the other hand, in the light detecting section B for detecting the reflected light from the subject 7, the imaging optical system 12 includes an imaging lens 13 and a detector 14, and the detector 13 is moved by moving a lens mounting stage 15 on which the lens 13 is mounted. Is adjusted so that the spot diameter at is minimized.
3, the detector 14 and the lens mounting stage 15 are a rotary stage 16
, And is driven by a motor 17, and its rotation angle is read by a rotary encoder 18.

Further, the above-described light irradiation section A and light detection section B are held on a gantry 19 and driven by a motor 20, and the rotation center thereof coincides with the optical axis of the He-Ne laser light, and The angle ω is read by the rotary encoder 21. The rotation axes of the mirror 6 and the light receiver 14 are parallel,
Each crosses the optical axis of the He-Ne laser beam at a right angle at points b and c.

Here, the variable attenuator 2, the lens mounting stage 8 and the motor 10 in the light irradiation unit A, the lens mounting stage 15, the motor 17 and the motor 20 in the light detection unit B are:
Controlled by the driver 22 and the controller 23,
The data of the rotary encoders 11, 18, and 21 is read by the reading counter 24. The series of these controls and the calculation of the position of the surface a of the subject 7 based on the data are CP
Performed by U25.

In the apparatus of the present embodiment, the beam expander 5
By controlling the rotating stage 9, an image adjusted to minimize the beam diameter is formed on the surface a of the subject 7 to be measured so that the image is located at the center of the optical axis of the imaging optical system 12. The rotation stage 16 is controlled and the lens mounting stage 15 is moved so that the spot diameter on the detector 14 is adjusted to be minimum. In this case, the rotation angle θ,
And the point a, using the distance x _m between b, it is possible to calculate the position of the surface a according to the principle of triangulation. Furthermore, three-dimensional mapping of the reflection point position of the subject 7 can be performed by sequentially measuring the rotation angles θ and ω in a similar manner.

In such an apparatus, He-Ne is used as the probe light.
Since the laser convergent light is used, sufficient illuminance can be secured at the measurement point.
A relatively small spot diameter of 10 mmφ at a distance of m and 3 mmφ or less can be obtained by using the lenses 3 and 4, and the luminance level can be improved.

Further, since the image of the reflecting surface a is positioned at the center of the optical axis of the imaging optical system 12 and the light receiving direction thereof is read, a circularly symmetric beam is always generated at the center of the lens 13 in the imaging optical system 12. Therefore, the influence of the lens aberration is removed.

In addition, since the rotation of the reflected light is controlled so as to coincide with the center of the optical axis of the imaging optical system 12, the detector 14 does not need to be a two-dimensional imaging element, and is provided with a one-dimensional line sensor or a pinhole. It may be a detector. In particular, in the above embodiment, the one-dimensional line sensor is sufficient because one of the rotation axes of the light irradiation unit A and the light detection unit B is matched. In the case of a one-dimensional line sensor, the number of pixels in one direction can be larger than that of a two-dimensional CCD, which is advantageous in measurement accuracy. Also, since a pinhole having a diameter of about 1 μm is available as a laser spatial filter, as described later, a CC having a pixel size of about 13 μm is used.
Higher resolution than D is possible.

Furthermore, in the present embodiment, one of the rotation axes of the light irradiation unit A and the light detection unit B is made to coincide with each other, and the other rotation axes are orthogonal to this, so that the position of the surface a by triangulation is determined. Can be easily obtained. In addition, the rotation of the light irradiation unit A and the light detection unit B in one direction can be performed in synchronization without complicating the apparatus. Since the θ scanning plane of the light irradiation unit A and the scanning plane of the light detection unit B coincide with each other, even if a narrow one such as a one-dimensional line sensor or a detector with a pinhole is used as the detector 14, the probe light The alignment of the optical system can be confirmed only by scanning the detector 14 only in the direction of the scan in the θ direction and confirming that the following light can be detected.

Note that one of the rotation axes of the light irradiation unit A and the light detection unit B does not necessarily have to be coincident, and the two rotation axes of the light irradiation unit A and the light detection unit B do not necessarily need to be orthogonal. .

Further, in the above embodiment, it is necessary to move the lenses 4 and 13 to the optimum positions in order to minimize the spot size on the subject 7 and the spot size on the detector 14, respectively. As this method, there is a method of performing focus servo on the lenses 4 and 13 while monitoring the spot size on the detector 14. In this case, the lenses 4 and 13 are used.
It is necessary to move the lenses 4 and 13 for the focus servo, which requires an adjustment time. In order to shorten this time, first, the position of the surface a of the subject 7 is provisionally measured, and the distance between the position and the lens 4, 13 is estimated. Based on the estimated value, the position of the lens 4, 13 is determined. Then, the position of the surface a is measured with high accuracy. In addition,
In this case, the positions of the lenses 4 and 13 and the focal position of the subject 7 (the position where the smallest spot is projected on the subject 7 for the lens 4, and the image of the subject 7 (Position of subject 7 when imaging on top)
Although it is necessary to find the relationship with in advance, it can be easily realized.

 Next, the results of specific tests will be described.

As shown in FIG. 2, a lens 31 (× 10 objective lens) and a lens 32 (camera lens with a focal length of 55 mm) are arranged in front of a He-Ne laser 30 (wavelength: 0.6328 μm) having an output of 10 mW. The lenses 31 and 32 function as beam expanders to focus the laser light on the subject 33. The diameter of the focused beam at this time was about 3 mmφ. Note that the subject 33 was arranged at a position of about 6 m, and the beam diameter when the beam expander was not used was about 10 mmφ. A black-gray rubber sheet was used as the subject 33.

Then, the reflected light from the subject 33 was received by the one-dimensional CCD camera 35 via the imaging lens 34. Here, imaging lens 3
As for 4, use a camera lens with a focal length of 55 mm, one-dimensional C
A CD having 2048 elements was used.

At this time, as shown in FIG. 3, a sufficient observation intensity was obtained for the light receiving signal of the CCD camera 35 despite the use of the subject 33 having a large scatter of the temporary reflectance.

Here, when the position coordinates (x, y, z) of the reflection point a of the subject 33 are obtained by calculation, Becomes This means that the coordinates of the point b are (−x _m / 2,0,0),
The coordinates of point c are (x _m / 2,0,0), and the origin of ω is the y-axis (xy plane corresponds to ω = 0).

Here, taking the difference from the formula Get. ,, Is the measurement error δ of ω, θ to the measurement error (δx, δy, δz) of the position coordinates (x, y, z) of the reflection point
The contributions of ω, δθ, δ are shown.

For example, in the apparatus shown in FIG. 1, ω, θ are read by the rotary encoders 21, 11, and 18, but the measurement accuracy is degraded when the resolution of the detector 14 is insufficient (δ
Becomes larger).

However, in the present invention, as described above, the detector 14
It is not necessary to use a two-dimensional image sensor, and the restriction due to the image resolution of the two-dimensional image sensor can be removed. Therefore, the measurement accuracy can be improved by using a high-resolution one-dimensional line sensor or a detector with a pinhole. Can be.

Here, examples of a high-resolution detector suitably used as the detector 14 are shown in FIGS. 4 (a) and 4 (b).

The detector shown in FIG. 4A has a lens 41 and a pinhole 42 arranged in front of the detector 40, and 43 is a case for holding these. According to this, the image condensed by the lens 41 and passed through the pinhole 42 is detected by the detector 40, and the resolution is improved by the pinhole 42. That is, since the pinhole 42 having a diameter of about 1 μm is available, the resolution can be improved by about one digit compared to the pixel size of the CCD. As the detector 40 in this case, it is desirable to use a detector having high detection sensitivity, such as a photomultiplier.

The detector in FIG. 4 (b) is similar to that in FIG. 4 (a), and members having the same operation are denoted by the same reference numerals.
In this case, a half mirror 44 is provided between the lens 41 and the pinhole 42, and the light reflected by the half mirror 44 can be monitored by the two-dimensional image sensor 45.

<Effects of the Invention> As described above, the three-dimensional position measuring apparatus according to the present invention uses a light beam as the probe light and focuses the light beam on the subject, thereby limiting the measurement target region to a minute region. At the same time, a sufficient luminance level is secured in the light detection unit, and the influence of image distortion due to lens aberration is eliminated by detecting the reflected light so as to match the optical axis by rotating and adjusting the light detection unit. In addition, since it is not necessary to use a two-dimensional image sensor as a detector, a measurement error due to the image resolution can be eliminated, and highly accurate three-dimensional position measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a three-dimensional position measuring device according to one embodiment,
FIG. 2 is an explanatory view showing an apparatus of a test example, FIG. 3 is an explanatory view showing measurement data thereof, FIGS. 4 (a) and (b) are configuration diagrams each showing an example of a detector, FIGS. FIG. 6 is an explanatory view showing a three-dimensional position measuring method according to the prior art. In the drawings, A is a light irradiation unit, B is a light detection unit, 1 is a He-Ne laser light source, 2 is a variable attenuator, 5 is a beam expander, 6 is a mirror, 7 is a subject, 9 is a rotating stage, and 10 is a rotating stage. Motor, 11 is a rotary encoder, 13 is a lens, 14 is a detector, 16 is a rotary stage, 17 is a motor, 18 is a rotary encoder, 19 is a mount, 20 is a motor, 21 is a rotary encoder, 22 is a driver, and 23 is a controller. , 24 is a reading counter and 25 is a CPU.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-196608 (JP, A) JP-A-62-81513 (JP, A) JP-A-62-274204 (JP, A) 116806 (JP, U)

Claims (3)

(57) [Claims] A light irradiating section which irradiates a subject with parallel light or convergent light as probe light and whose irradiation direction is variable by rotation around two rotation axes; an imaging lens and a light receiving element; A light detection unit that changes the optical axis direction by rotation about two rotation axes, and adjusts and detects the reflected light from the optical sample so that the image of the reflection point coincides with the optical axis; A processing unit for detecting the position of the reflection point based on the principle of triangulation from the emission direction of the probe light, the light receiving direction at the light detection unit, and the relative positional relationship between the light detection unit and the light irradiation unit. One rotation axis of the light irradiation unit and one rotation axis of the light detection unit coincide with a straight line connecting the rotation center of the light irradiation unit and the rotation center of the light detection unit, and receive light. A three-dimensional position measuring device, wherein the device is a one-dimensional image sensor. . 2. The apparatus according to claim 1, wherein the light irradiating unit includes focusing means for adjusting the spot diameter of the probe light to the optical sample to be minimum, and the light detecting unit is a spot observed by the light receiving element. Focusing means for adjusting the diameter to be minimum is provided, and the processing unit operates both the focus means based on the data of the position of the reflection point temporarily obtained before the focus by the two focus means, and then determines the accurate reflection point. A three-dimensional position measuring device for performing a process for obtaining a position. 3. The device according to claim 1, wherein the light receiving element of the light detecting unit is a detecting unit with a pinhole, and the light detecting unit rotates so that the light receiving power becomes maximum and changes the light receiving direction. A three-dimensional position measuring device characterized by being obtained.