JP4350497B2 - Shape measuring device for special shaped articles - Google Patents

Description

  The present invention relates to an apparatus for measuring the shape of an article having a special shape composed of a plurality of ridges that are continuously connected, such as a rack that is one of mechanical elements used for conversion between rotational motion and linear motion. More specifically, the present invention relates to automation of dimension measurement at a specific measurement location of a specially shaped article in a final inspection process of the specially shaped article manufactured by machining.

  Conventionally, as a shape measuring device that automatically measures the dimensions of an article in an inspection process at a manufacturing site with high accuracy, the article is imaged by a high-resolution industrial camera, and the image is processed to calculate the dimensions of a desired location. Has been known (for example, see Patent Document 1).

JP 2003-194529 A

  However, the conventional shape measuring apparatus using image processing is suitable for measuring a flat article or an article having a simple shape such as a rectangular parallelepiped or a sphere. No consideration was given to the shape measurement of special-shaped articles having a mold. That is, as shown in FIG. 3 (a), when a specially shaped article 100 having a plurality of continuous mountain shapes is vertically set up and imaged by an imaging means 200 such as an industrial camera, the image shown in FIG. As shown, all the mountain-shaped ridge lines overlap and appear in the projected image 100a, and the respective mountain-shaped ridge lines cannot be specified. Further, as shown in FIG. 4A, when a special-shaped article 100 having a plurality of continuous chevron shapes is horizontally imaged, all the chevron shapes are projected as shown in FIG. 4B. Although appearing in the image 100b, each mountain-shaped ridge line is projected as a point, and thus the height at the center of the ridge line cannot be measured. In particular, in a concave cylindrical article in which the height of the central portion of the mountain shape is lower than both end portions, the height of the central portion of the mountain shape (point G in FIGS. 3 and 4) is to be measured. In this case, since the measurement point does not appear in the projected image, at present, it has been necessary to rely on manual measurement using a micrometer, a caliper, or the like. Therefore, the inspection process not only becomes a bottleneck for shortening the manufacturing lead time, but also causes a measurement error due to a difference in the skill level of the measurer, which causes a decrease in inspection accuracy and inspection quality.

  In addition, as individuality of consumers, high-quality orientation, and diversification of consumer needs are progressing, each manufacturer is urgently required to respond to small quantities of various products and quick delivery. There is a demand for higher quality products. In order to achieve this, development of a high-speed and high-precision shape measuring device for specially shaped articles is required.

  Therefore, an object of the present invention is a shape capable of measuring the height of a mountain shape at a specific measurement location of a specially shaped article having a plurality of mountain shapes that are continuously connected, at high speed and with high accuracy, without manual operation. It is to provide a measuring device.

  The shape measuring apparatus according to claim 1 is an image capturing device for imaging the special shape article in the shape measurement apparatus for measuring the height of the mountain shape at a specific measurement location of the special shape article having a plurality of continuous mountain shapes. Means for irradiating the specially shaped article, holding means for holding the specially shaped article at a given inclination with respect to the imaging means, and calculation for calculating the height of the mountain at the measurement location And the holding means holds the specially shaped article at the inclination angle so as to project a mountain-shaped ridge line where the measurement location is located on the image captured by the imaging means as a shadow line, Based on the projected dimensions relating to the measurement location obtained from the shaded line projected on the image, the known dimensions on the specially shaped article relating to the measurement location, and the inclination angle, By and calculates the height of the mountain-shaped at the measuring point, is to solve the above problems.

  According to the shape measuring apparatus according to claim 1, the special shape article is held at an inclination angle such that the mountain-shaped ridge line where the measurement point is located is projected as a shadow line on the image picked up by the image pickup means, and picked up The height of the mountain shape at the measurement location is calculated based on the projection size relating to the measurement location obtained from the shaded line projected on the measured image, the known size on the specially shaped article relating to the measurement location, and the inclination angle. Therefore, due to the reflection of the irradiated light on the mountain-shaped slope of the specially shaped article and the scattering on the mountain-shaped ridgeline, the mountain-shaped ridgeline where the measurement location is located is projected as a shadow line on the captured image, It becomes possible to measure the height of the mountain shape at a specific measurement location of the shaped article at high speed and with high accuracy without manual intervention.

  An embodiment of the shape measuring apparatus of the present invention will be described with reference to FIG. 1 and FIG.

  FIG. 1 is a diagram for explaining the outline of the configuration of a shape measuring apparatus according to the present invention and the principle of shape measurement. FIG. 1 (a) is a vertical cross section passing through a measurement location H of a specially shaped article 10 as a measurement object. Is shown. The shape measuring apparatus of the present invention is illustrated with an imaging means 20 for imaging a specially shaped article 10 having a plurality of continuous chevron shapes as an object to be measured, and an irradiating means 30 for irradiating the specially shaped article 10. Although not provided, a holding means for holding the specially shaped article 10 at a given inclination angle θ with respect to the imaging means 20 is provided.

  Ideally, as the irradiating means 30, it is preferable to use a parallel optical system transmitted illumination capable of irradiating parallel light rays in terms of minimizing measurement errors. A surface-emitting lamp using a lamp as a light source is preferably used, and incident light Lin, which is a substantially parallel light beam, is applied to a measurement location of the specially shaped article 10.

  The imaging unit 20 is not particularly limited as long as it can capture images with high resolution and without distortion. However, a commercially available industrial camera such as a CCD camera can be used from the viewpoint of simplicity of processing image data, cost, and the like. Preferably used. When extremely high measurement accuracy is required, an imaging lens having a parallel beam path, that is, a CCD camera using a telecentric lens in an optical system is used.

  The special shaped article 10 is held at an inclination angle θ such that the reflected light Lref of the incident light Lin irradiated by the illumination unit 30 is projected onto the image captured by the imaging unit 20. As a result, on the image picked up by the image pickup means 20, as shown in FIG. 1B, all the mountain-shaped ridge lines of the specially shaped article are projected as shadow lines. Here, the reason why all the mountain-shaped ridge lines are projected as shadow lines by inclining the specially shaped article 10 with respect to the imaging means 20 will be described with reference to FIG.

  FIG. 2 is an enlarged view of a chevron cross section at a measurement point of the specially shaped article 10 shown in FIG. In the specially shaped article 10 having a plurality of continuous chevron shapes, a curved cross section having a finite radius of curvature as shown in FIG. It has a shape in which the normal direction changes continuously in the vicinity of the apex portion. Therefore, incident light Lin that is a substantially parallel light beam (irradiation angle is ± θmax or less) is applied to the continuous mountain-shaped slope of the specially shaped article 10 that is inclined at an inclination angle θ with respect to the line of sight of the image pickup means 20. When the image is irradiated and the projected image is picked up by the image pickup means 20, the incident light Lin striking the vicinity of the mountain-shaped apex is not reflected in the direction of the image pickup means 20 and deviates from the field of view of the image pickup means 20. As a result, each mountain-shaped ridge line portion has a smaller amount of light than the mountain-shaped slope portion, and appears as a shaded line on the screen imaged by the imaging means 20 as shown in FIG. .

  When a general industrial camera with a shallow depth of field is used as the imaging means 20, this shadow line is sharpest, that is, thinner and more, by adjusting the focus of the camera to the mountain shape to be measured. It appears dark (darker black on the screen). Therefore, when measuring the specially shaped article 10 in which a plurality of mountain shapes of the same shape are continuously connected, the ridge lines of the plurality of mountain shapes are obtained by sequentially adjusting the focus of the imaging means 20 to each of the mountain shapes. Can be detected. On the other hand, when measuring a specially shaped article having a differently shaped chevron, as is apparent from the description in the previous paragraph, the angle of the illumination unit 30 is changed so that the chevron-shaped ridge line to be measured becomes the image capturing unit 20. It is possible to detect a plurality of mountain-shaped ridge lines that do not have the same shape by making adjustments so that they appear as shaded lines on the imaged image.

  Next, from the projection image as shown in FIG. 1B, the computing means calculates the height of the mountain at a specific measurement location (point H in FIG. 1) of the specially shaped article 10. One technique for doing this will be described with reference to FIGS.

  As described above, the specially shaped article 10 having a plurality of continuous peaks is inclined at an inclination angle θ with respect to the line of sight of the imaging unit 20, and the mountain-shaped slope is irradiated by the illumination unit 30. When the image is taken, a projection image as shown in FIG. 1B is obtained. The peak-shaped height HP (= B) at a specific measurement location H of the special-shaped article 10 is a distance OP (= LB) from the end surface of the special-shaped article 10 having a known dimension to the peak-shaped ridgeline where the measurement location H exists. ) And the inclination angle θ, which is a given angle, and the projection dimension HF (= BT) for the measurement location H obtained from the projection image, are calculated based on the following equation.

B = B _T / cos θ−L _B · tan θ + K (Formula 1)
The reason can be explained geometrically based on FIG. 1A as follows. That is, the peak-shaped height HP (= B) to be obtained is
HP = B = GH-GP (Formula 2)
It is. Since the right triangle HFG and the right triangle OPG are similar, the angle GHF (= θ _H ) and the angle GOP (= tilt angle θ) are equal. And of course,
cos θ _H = HF / GH = B _T / GH (Formula 3)
Because
GH = B _T / cos θ _H = B _T / cos θ (Formula 4)
The following relational expression is obtained. On the other hand, clearly from the relationship between the sides and corners of the right triangle OPG,
_{GP = OP · tanθ = L B} · tanθ ( Equation 5)
The following relational expression holds.

  Therefore, (Formula 1) is obtained by substituting (Formula 4) and (Formula 5) into the above (Formula 2). Here, the K value in (Equation 1) is an offset value obtained by calibration. That is, when measuring a standard article in which the height of the chevron is accurately determined or a reference article in which the height of the chevron is accurately measured in advance by hand, the equation 1 is established. By determining the value, the measurement error caused by the aberration of the optical system of the image pickup means 20 or the property of the object to be measured is calibrated to improve the measurement accuracy.

  Furthermore, as shown in FIG. 2, by disposing the polarizing plate 40 on the front surface of the imaging unit 20, image distortion due to parallax can be suppressed, and measurement accuracy can be further improved.

  The present invention can not only automate the inspection process in the manufacture of specially shaped articles that had to be relied on by hand, but also the measurement time in all industrial fields where the shape measurement of specially shaped articles is required. And the stability of measurement quality can be secured, and its industrial applicability is extremely large.

It is explanatory drawing explaining the outline of the apparatus structure of a shape measuring device of this invention, and a shape measurement principle. It is explanatory drawing explaining the reason a mountain-shaped ridgeline is projected as a shadow line. It is explanatory drawing explaining the measurement of the special-shaped article by the conventional shape measuring apparatus. It is explanatory drawing explaining the measurement of the special-shaped article by the conventional shape measuring apparatus.

Explanation of symbols

10, 100 ... Special shaped article 20, 200 ... Imaging means 30 ... Irradiation means 40 ... Polarizing plate

Claims (1)

In a shape measuring device that measures the height of a mountain shape at a specific measurement location of a specially shaped article having a plurality of mountain shapes that are continuously connected,
Imaging means for imaging the specially shaped article;
Irradiating means for irradiating the specially shaped article;
Holding means for holding the specially shaped article at a given inclination with respect to the imaging means;
Calculating means for calculating the height of the mountain at the measurement location,
The holding means holds the specially shaped article at the inclination angle so as to project a mountain-shaped ridge line where the measurement location is located on the image captured by the imaging means as a shadow line,
The calculation means is based on a projected dimension relating to the measurement location obtained from the shaded line projected on the image, a known dimension on the specially shaped article relating to the measurement location, and the inclination angle. It is to calculate the height of the mountain,
A shape measuring device characterized by

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