JPH03205503A - Image position detecting method for sheet light - Google Patents

Abstract

PURPOSE:To accurately detect the image position of the sheet light even when the brightness distribution of an image of the sheet image is saturated or has right-left asymmetry by weighting a position parameter in measured image data obtained by an image pickup device with a light-dark (brightness) parameter. CONSTITUTION:A body 1 to be measured is irradiated with the sheet light 3 and the image pickup device 4 which has a known image pickup optical axis angle theta to the sheet light 3 picks up an image to find the position P in the obtained image data of the sheet light 3 in the image data of an image pickup element 8. The illuminance brightness B(x) of the sheet light 3 at a scanning position X in the measured image data shown by a lateral axis in the brightness distribution on a scanning line perpendicular to the image of the sheet light 3 is weighted with a certain threshold value Bt in the image data on the body 1 to be measured which is obtained by the image pickup device 4 to aim at only the brightness exceeding this threshold value Bt. A point P which is an image position indicating the mean value of the weighted position is the extremely highly accurate position of the image of the sheet light 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting the image position of a sheet of light used in an optical three-dimensional coordinate measuring device that non-contactly measures the three-dimensional coordinates of an object to be measured. .

[Conventional technology]

In the optical three-dimensional coordinate measuring device mentioned above and the device that measures the relative position between multiple objects, a sheet of light is irradiated onto the object to be measured, and the object is measured at a certain angle with respect to the sheet light. Attempts have been made to take images of objects to be measured and measure their three-dimensional coordinates. This is called the two-beam cutting method, in which three-dimensional information is obtained by creating a cut plane of the object to be measured using a sheet of light and photographing it from the side at a certain (known) angle.

Here, an overview of the optical three-dimensional coordinate measuring device will be explained using diagrams. FIG. 3 is a perspective view showing the configuration of the optical three-dimensional coordinate measuring device, FIG. 4 is a side view thereof, and FIG. 5 is a diagram of its principle.

In Figure 3, 1 is the object to be measured. ．． 2 is a sheet light generation source; 3 is a sheet light irradiated onto the object 1 to be measured; 4 is a sheet light irradiated to the object 1 from the side while having a certain angle with the sheet light 3;
5 is an arithmetic processing device for calculating the three-dimensional coordinates of the object to be measured 1 from the image obtained by the image capturing device 4; 6 is a processing device for calculating the three-dimensional coordinates of the object 1 from the image obtained by the image capturing device 4; This is an image input device for converting into numerical data so that it can be handled by the processing device 5.

The positional relationship of each button on the three-dimensional coordinate measuring device is as shown in FIG. 4 when viewed from the side.

The optical axes of the sheet light 3 and the imaging device 4 intersect at an angle θ. FIG. 4 shows a case where the object to be measured 1 exists at the intersection of the sheet light 3 and the optical axis of the imaging device 4.

The principle of measuring three-dimensional coordinates will be explained with reference to FIG. Components in FIG. 5 with the same numbers as those in FIG. 4 have the same functions, and their explanation will be omitted. 7 is an imaging lens of the imaging device 4F). It is an 8Vi image sensor. Sheet light 3 emitted from sheet light source 2 is applied to object 1 to be measured.
is irradiated. 1 Measured object 1 is at position X. (Sheet light 3
and the optical axis of the imaging device 4 intersect at an angle θ),
The image of the sheet light 3 irradiated (projected) onto the object to be measured 1 is located at the center X of the image sensor 8 . It is in. When the object to be measured 1 is at position X, the image of the sheet of light 3 is located at position The image is located at position X2 on the image sensor 8 when the button is pressed. Therefore, if the angle θ between the sheet light 3 and the optical axis of the imaging device 4 and the distance between them (distance l in FIG. 5) are known in advance, then the relative position in the imaging device 8 (the The position of the object to be measured 1 (relative position with respect to the imaging device 4) can be known from the image sensing device 4, and if the absolute coordinates of the imaging device 4 are known, the absolute coordinates of the object to be measured 1 can be obtained. 1.Shield light 3 and imaging device 4
The three-dimensional absolute coordinates of the entire object to be measured 1 can be obtained by scanning it by a drive device (not shown) while keeping the positional relationship constant. Irradiating the object to be measured 1 with the sheet of light 3 is the same as cutting the object to be measured 1 along the plane represented by the sheet of light 3, and the cut surface is detected by the imaging device 4. This method is called photosection method.

In actual coordinate measurement, from the image obtained by the imaging device 4, the position where the sheet light 3 is irradiated onto the object 1 (that is, the position where the image sensor 8 falls) is determined. FIG. 6 shows an example of image data obtained by the imaging device 4 for which the position on the image data needs to be detected. 9#'i is an image corresponding to the irradiation position of the sheet light 3 irradiated onto the object 1 to be measured. In such a case, the sheet light 3 is scanned in the direction of the broken line shown in the figure.
It is common to search for an image of
The following seventh method is used to calculate the position P of the image of the sheet light 3.
There are two methods as shown in Figure (bl or Figure 7(c)).

(1) Peak method [Fig. 7(b)]: The point having the peak (maximum value) of brightness in the brightness distribution is defined as P.

: In the brightness distribution, exceeds a certain threshold Bt Focus on the range and set the threshold Two points passing through the value Bt (1) Midpoint method [Figure 7 (C)] (rise of brightness distribution falling sharply) Let P be the midpoint of

However, such conventional methods have the following drawbacks.

(1) If the image of the sheet light 3 is very bright and the brightness distribution is saturated, the point P cannot be calculated using the peak method [FIG. 8(a)].

(2) If the brightness distribution of the image of the sheet light 3 is left and right asymmetric, the point P' calculated by the midpoint method is the peak position P of the actual image.
This results in an error [Fig. 8(b)].

(3) If saturation and left-right asymmetry of the luminance distribution occur simultaneously (at 0 [Fig. 8]), neither the peak method nor the midpoint method can detect accurately.

In this way, the case where the position P of the image of the sheet light 3 cannot be detected with high accuracy and accurate three-dimensional coordinates cannot be obtained depends on the material, angle, and type of light source of the surface to be irradiated with the sheet light. often exists.

[Problem to be solved by the invention]

As explained above, the optical cutting method is a method that can measure the three-dimensional coordinates of the object to be measured 1 with high precision in a non-contact manner using a very simple optical system, but it has the following problems. Ru. That is, when the brightness distribution of the image of the sheet light 3 is saturated and asymmetrical, the conventional image position detection method of the sheet light 3 cannot detect the image position with high precision, and accurate coordinate measurement cannot be performed. I can't.

The present invention was made in view of the above-mentioned problems, and is based on image data obtained by an imaging device. To provide a sheet light image position detection method that makes it possible to accurately detect the sheet light image position within measured image data even when the brightness distribution of the sheet light image becomes saturated υ and left-right asymmetric. [Means for solving the problem] That is, the sheet light image position detection method according to the present invention is as follows:
The image position of the sheet light is detected by weighting the brightness (brightness) parameter to the position parameter in the measurement target image data obtained by the imaging device.

[Effect]

Therefore, even if the brightness distribution of the image of the sheet light obtained by the imaging device is saturated or asymmetrical, the image position of the sheet light within the captured image data can be detected with high accuracy.

〔Example〕

An embodiment of the sheet light image position detection method according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the luminance distribution on the scanning line in the direction perpendicular to the image of the sheet light 3 in the image data of the object to be measured 1 obtained by the imaging device 4 shown in FIG. Regarding the irradiation brightness distribution of the sheet light 3, the horizontal axis is the scanning position X in the image data to be measured, and the vertical axis is the irradiation brightness Qx of the sheet light 3. Present invention 1! In this embodiment, attention will be paid only to the luminance distribution applied to the image data of the object to be measured 1, which exceeds a certain threshold value B.

Here, the position P of the image of the sheet light 3 on the image data of the object to be measured 1 imaged by the imaging device 4 is determined using the following equation.

The image position "point P" of the sheet light 3 on the image data to be measured obtained by this formula (1) represents the average value of the position weighted by brightness and darkness based on the irradiation brightness of the sheet light 3, and is extremely accurate. This is the position of the image of the sheet light 3 with a high value.

Figure 2 shows the image position detection state of the sheet light with respect to the sheet light irradiation brightness distribution of the actual image data to be measured. , the image position detection results by the detection method according to the embodiment of the present invention are shown by white circles, and the image position detection results by the conventional detection method (midpoint method) are shown by black circles. (Of course, the peak method cannot be used when the light intensity is saturated like this.

) respectively, the image position of the sheet light 3 obtained when the threshold value of the light intensity th is changed from th1 to th is calculated.

Therefore, according to the sheet light image position detection method as described above, the position of the image of the sheet light 3 can be detected with higher accuracy than the conventional image position detection method. in this case,
It is also true that the image position detection result is greatly influenced by the threshold of the light intensity th.The thO threshold is, for example, 1/2, 1/3, . It can be changed arbitrarily to 2/3 etc. This makes it possible to obtain accurate three-dimensional coordinates of the object to be measured 1.

〔Effect of the invention〕

In summary, according to the present invention, a sheet of light is irradiated onto a measurement target, and the measurement target is photographed by an imaging device having a known imaging optical axis angle with respect to the sheet light. The position of the image of the sheet light is detected within the image data, and the position parameter of the sheet light in the direction perpendicular to the sheet direction within the image data is weighted by two meters of contrast depending on the sheet light irradiation brightness, Since the position of the sheet light image within the image data is determined, even if the brightness distribution of the sheet light image in the captured image data is saturated or asymmetric, the sheet light image relative to the measurement target can be accurately determined. The position of the object can be detected, making it possible to realize optical coordinate measuring devices that are extremely useful in industry.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a scanning brightness distribution for image data to be measured for image position detection in a sheet light image position detection method according to an embodiment of the present invention, and FIG. 2 is a sheet light image position detection method based on the above-mentioned image position detection method. FIG. 3 is a perspective view showing the configuration of an optical coordinate measuring device using the light cutting method; FIG. 4 is a diagram showing the configuration of the optical coordinate measuring device described above. 5 is a schematic diagram showing the principle of coordinate measurement by the optical coordinate measuring device, FIG. 6 is a diagram showing the image of the sheet light within the image data to be measured, and FIG.
Figures 1 to 8 (e) show conventional sheet light image position detection means, and Figures 8 (a) to 8 (c) show sheet light irradiation, which is a problem when detecting the conventional sheet light image position. It is a diagram showing the luminance distribution. 1... object to be measured, 2...
・Sheet light source. 3... Sheet light, 4... Imaging device, 5... Arithmetic processing unit, 6... Image input device, 7... Imaging lens, 8... Imaging element, 9... Sheet image of light.

Claims (1)

[Claims] A sheet of light is irradiated onto the measurement target, the measurement target is imaged by an imaging device having a known imaging optical axis angle with respect to the sheet light, and the sheet light is imaged in the image data obtained by this imaging device. In a sheet light image position detection method for detecting the image position, a position parameter of the sheet light in the direction perpendicular to the sheet direction within the image data is weighted with a brightness parameter according to the sheet light irradiation brightness, 1. A sheet light image position detection method comprising detecting a sheet light irradiation position.