JPH04289403A - Method for measuring height of article - Google Patents

Abstract

PURPOSE:To obtain the method for measuring the height of an article which can accurately measure the height of an article such as a honeycomb structure whose cross-sectional shape is noncircular along the entire outer surface. CONSTITUTION:The radius of an article 2 on the line connecting a central axis O of a turntable 4 on which the article 2 such as a honeycomb structure is mounted and a camera 3 is computed beforehand. The radius is inputted in a control device 8. The camera 3 is moved back and forth with a servomotor 5 in response to the above described computed value of the radius with the rotation of the turntable 4. Thus, the distance between the camera 3 and the surface of the article is kept constant. In this way, the focal point of the camera 3 can be focused on the surface of the article 2 all the time, and the height can be accurately measured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the height of an article such as a honeycomb structure having a non-circular cross section.

0002

[Prior Art] Articles such as honeycomb structures for automobile exhaust gas treatment must be tightly housed inside metal casings, so their height must be accurately measured all around before shipping. That is what is required. For this purpose, the present applicant previously developed a device that rotates a honeycomb structure on a turntable and measures the height to its upper edge using a camera with a built-in image sensor. It has been announced as.

However, when the honeycomb structure has a non-circular cross section, the distance between the camera and the surface of the honeycomb structure changes greatly as the turntable rotates, so keeping the camera fixed will not be accurate. It may be impossible to focus, resulting in decreased measurement accuracy. Therefore, in the invention of Japanese Patent Publication No. 60-13443, as shown in FIG. By moving it with a motor, the focus is always kept on the surface of the article 2 on the turntable 4.

However, what is measured by the laser length measuring device 1 is the distance to the point A of the article 2, and what actually matters is the distance to the point B of the article 2. For this reason, when highly accurate measurement is required, there is a risk that the camera 3 will be out of focus depending on the shape of the article 2, resulting in a decrease in measurement accuracy.

[0005]

[Problems to be Solved by the Invention] The present invention solves the above-mentioned conventional problems and allows the camera to always be correctly focused on the surface of the article regardless of the cross-sectional shape of the article, thereby achieving high measurement accuracy. This was completed in order to provide a method for measuring the height of an article by which the height of the article can be measured over the entire circumference.

[0006]

[Means for Solving the Problems] The present invention, which has been made to solve the above problems, is an article whose height is measured by placing the article on a turntable and rotating it, and capturing an image of the upper edge of the article with a camera. In the height measurement method, the radius of the object on the line connecting the center axis of the turntable and the camera is calculated in advance, and the camera is moved forward and backward on the line according to the calculated radius. This method is characterized by performing measurements while maintaining a constant distance from the surface of the article.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in more detail below with reference to illustrated embodiments. 1 and 2, 2 is an article placed on a turntable 4 and rotates around the central axis O of the turntable, and 3 is a camera with a built-in linear image sensor. This is the same as the conventional method. The camera 3 can be moved forward and backward on a line connecting the central axis O and the camera 3 by a feed screw 6 rotated by a servo motor 5.

In the present invention, the radius of the article 2 on the line connecting the central axis O of the turntable 4 and the camera 3 is calculated in advance for each article 2 to be measured. in fact,
For the article 2, such as a honeycomb structure, there are about 150 points to be measured on the circumference, so as shown in Fig. 3, the radius of each of these measurement points P is determined by the rotation angle from the reference line. I will ask for it together. FIG. 4 is a graph showing the relationship between the rotation angle θ and the radius l when the article 2 has an elliptical cross section. Also, Figure 5
6 shows each measurement point P when the cross section of the article is constituted by a large number of circular arcs, and FIG. 6 is a graph showing the relationship between the rotation angle θ and the radius l.

In order to measure the height of the article 2 by the method of the present invention, first, the article 2 such as a honeycomb structure is set correctly at a predetermined position on the turntable 4, and then the servo motor for rotating the turntable is 7, the turntable 4 is rotated so that the first measurement point P is on the line connecting the central axis O of the turntable 4 and the camera 3. Then, the camera 3 is moved forward and backward by the servo motor 5 on the above line in accordance with the calculated value of the radius at the measurement point P, which is input into the control device 8 in advance. This movement of the camera 3 back and forth is to perform measurements while keeping the distance L between the camera 3 and the surface of the article constant, so that the height can be measured with the focus correctly on the surface of the article 2. will be possible.

[0010] When the measurement of the first measurement point P is completed as described above, the servo motor 7 rotates the turntable 4 to the next measurement point P, and similarly rotates the camera 3 to the pre-input radius calculation value. Measure the height while moving the robot forward and backward. In reality, it is not necessary to stop the turntable 4 each time a measurement is made, and it is sufficient to reduce the rotational speed to such an extent that the focus of the camera 3 does not blur. Further, it is desired that the rotation to the next measurement point P be performed as quickly as possible in order to shorten the inspection time. Therefore, the servo motor 7 rotates the turntable 4 once while repeating high speed rotation and low speed rotation. In the example, the time required for one rotation is 3 seconds, and height measurements are performed at approximately 150 measurement points P during this period.

[0011]

As explained above, according to the method of the present invention, the radius of the article on the line connecting the center axis of the turntable and the camera is calculated in advance, and the camera is moved to the calculated radius. The distance between the camera and the surface of the article is kept constant during measurement by moving the camera forward and backward along the above-mentioned line accordingly, so that the focus of the camera can always be accurately set on the measurement surface of the article. Therefore, even if the cross-sectional shape of the article is non-circular, the height can always be measured over the entire circumference with high accuracy. Furthermore, by rapidly rotating the turntable to each measurement point as in the embodiment, height measurements at a large number of measurement points can be completed in a very short time. Therefore, the present invention greatly contributes to the development of industry as a method for measuring the height of an article that solves the conventional problems.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a plan view showing an embodiment of the present invention.

FIG. 3 is a plan view illustrating some of the measurement points of the honeycomb structure.

FIG. 4 is a graph illustrating the relationship between rotation angle and radius of a honeycomb structure.

FIG. 5 is a plan view illustrating some of the measurement points of another honeycomb structure.

FIG. 6 is a graph illustrating the relationship between rotation angle and radius of another honeycomb structure.

FIG. 7 is a plan view showing a conventional measurement method.

[Explanation of symbols]

1 Laser length measuring device 2 Article 3 Camera 4 Turntable 5 Servo motor 6 Feed screw 7 Servo motor for rotating the turntable 8 Control device

Claims (1)

[Claims] Claim 1: In a method for measuring the height of an article, in which the article is placed on a turntable and rotated, and the height is measured by capturing an image of the upper edge of the article with a camera, the object is placed on a line connecting the central axis of the turntable and the camera. The radius of the article is calculated in advance, and the camera is moved forward and backward along the above line according to the calculated value of the radius, thereby making measurements while keeping the distance between the camera and the surface of the article constant. How to measure the height of an item.