JP2787928B2 - Image signal processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing method for accurately measuring the shape of an object to be measured using laser light.

[0002]

2. Description of the Related Art Recently, measuring instruments for performing various measurements using laser light have been frequently used. A measuring instrument using such a laser beam receives laser reflected light from a measuring object by a one-dimensional line sensor or the like, and performs various measurements by using a video signal based on an electric signal converted by the sensor. Has become. For example, when measuring the shape of a measuring object having an L-shaped cross section, first, the reflected light from the measuring object obtained by irradiating the measuring object with the laser light output from the laser emitting means is used. The level is captured by a one-dimensional CCD camera, and the level of each cell of the CCD is multi-valued based on a video signal from the CCD camera.
Next, the center of the video signal is obtained by calculating the area centroid of the graph (or waveform) obtained by the multi-value conversion, and the distance between the CCD camera and the object to be measured, that is, the distance measurement value is calculated. Further, the above-described processing is sequentially performed while sequentially changing the irradiation position of the laser light, a distance measurement value at each irradiation position is obtained, two-dimensional distance measurement value sequence data is obtained, and a method such as a least squares method is used. The shape is obtained from the distance measurement value sequence data.

[0003]

However, since the laser light reflected from the object to be measured contains secondary reflected light and the like, a variation due to an error occurs near the peak of the obtained video signal. . This is based on the speckle phenomenon due to roughness of the surface of the measurement object. Under the influence, even if the objects existing at the same distance are measured, the distance measurement values will vary. For example,
When the shape of the L-shaped measurement object is measured, a video signal as shown by a solid line in the graph shown in FIG. 6 should be normally obtained. A video signal having a waveform as indicated by the dotted line is obtained. Therefore, when the two-dimensional distance measurement value sequence data is calculated based on the video signal affected by the speckle phenomenon, and the shape thereof is determined based on the data, the variation in the distance measurement value data is large. As a result, as shown in FIGS. 7 and 10, the shape described by a solid line, which is normally obtained, is slightly shifted from the shape described by a dotted line shown in FIG. 7, and as a result, an accurate shape cannot be obtained. There is. In particular, the vertex coordinates of the L-shape are greatly affected by this effect as shown in FIG.

In order to alleviate this problem as much as possible, conventionally, as shown in FIG. 8, about 70% or more of the peak value of the video signal obtained is cut, and the center of gravity is calculated for the remaining portion to obtain a distance measurement. I get value string data. In this way, the error can certainly be reduced, but aside from the video signal shown in FIG. 9, the error is reduced in the case of a video signal having a prominent peak as shown in FIG. Can be said to be negligible. The present invention has been made in view of such problems of the related art, and provides an image signal processing method capable of performing various kinds of measurements on a measurement object without being affected by speckles or the like as much as possible. With the goal.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of irradiating an object to be measured with a laser beam and inputting laser reflected light from the object to be measured. A step of capturing light with a large number of photoelectric conversion elements, converting the photoelectric conversion elements into electric signals of a level corresponding to the reflected light intensity for each of the photoelectric conversion elements, and plotting the levels of the converted electric signals in the order of the photoelectric conversion elements. The step of sequentially reducing the level of the photoelectric conversion element presently having the highest level until the area is reduced by a predetermined ratio, and the step of calculating the position of the center of gravity in the direction of the photoelectric conversion element in the graph in which the area is reduced to the predetermined percentage It is characterized by having.

[0006]

According to the image signal processing method of the present invention, the input laser reflected light is captured by a large number of photoelectric conversion elements, and is converted into an electric signal of a level corresponding to the reflected light intensity for each of the photoelectric conversion elements. A graph in which the level of the photoelectric conversion element presenting the highest level at present is sequentially reduced until the area of the graph created by plotting the level of the electric signal in the order of the photoelectric conversion element and decreasing the area to the predetermined percentage Since the position of the center of gravity in the direction of the photoelectric conversion element is calculated, it is possible to effectively suppress the occurrence of an error in the calculation of the center of gravity of a video signal having a prominent peak. Therefore, even if the video signal includes a large error near the peak due to the influence of the surface condition of the measurement target, the occurrence of the measurement error is suppressed.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image processing apparatus that realizes an image processing method according to the present invention. In the shape measuring sensor 1, a laser light generating means 2 and a laser light L from the laser light generating means 2
Is provided with a reflection mirror 4 for irradiating the light. Further, a lens system 5 for inputting the laser reflected light L 'from the measuring object 3 and a CCD camera 6 are provided. The reflecting mirror 4 also has a role of guiding the laser reflected light L ′ from the measuring object 3 to the above-mentioned lens system 5 and CCD camera 6. The reflection mirror 4 is configured to be able to rotate by a predetermined angle, and this rotation changes the irradiation position of the laser beam. This rotation is performed by a servomotor 7, and the rotation angle is detected by an encoder 8, so that the irradiation position of the laser beam can be recognized. The CCD camera 6 and the encoder 8 are connected to a sensor control board 10, on which photoelectric conversion data from the CCD camera 6 and rotation angle data from the encoder 7 are input. Used for measurement calculation. This sensor control board 10 includes:
The data processing device 12 is connected.
Performs image processing for shape calculation. In addition,
The laser beam used in this embodiment is a spot beam, and C
The photoelectric conversion element built in the CD camera 6 is a one-dimensional line sensor.

The image signal processing apparatus having the above configuration operates as follows based on the flowchart shown in FIG. 2 to calculate the shape of the object to be measured. First, the laser light L output from the laser light generating means 2
Is irradiated on the measurement object 3 via the reflection mirror 4. The laser light L is reflected on the surface of the measuring object 3 to become a laser reflected light L ′, and this laser reflected light is reflected by the reflecting mirror 4.
And is incident on the CCD camera 6 via the lens system 5. Each element constituting the one-dimensional line sensor built in the CCD camera 6 outputs an electric signal of a magnitude corresponding to the amount of light incident on each element to the sensor control board 10. The data processing device 12 generates a video signal as shown in FIG. 3 based on the magnitude of the electric signal output from each element. The horizontal axis of this video signal is the sequence of elements, and the vertical axis is the amount of incident light.

The video signal obtained from one reflected light of the laser spot light is divided into 256 for each element (cell). That is, as shown in FIG. 4, a process of dividing the level of the amount of light incident on each element into 256 levels is performed (S1). Next, application exclusion processing is performed on cells having a low light receiving level. For example, in the process of S1, a process of excluding from the target in performing the subsequent processes is performed for the 50th and lower stages from the low level. For example, FIG.
When this processing is performed on the video signal after the division processing, the areas A and B in the figure are excluded from application (S2). Next, in the graph of FIG. 4, the area and the first moment of area of the figure composed of the cells to be applied are obtained. This area is calculated by adding the level of the target cell for each cell (S
3). Next, a process of searching for the maximum value of the light receiving level is performed, a portion having the highest level is deleted, and a process of subtracting the area and the first moment of area of the deleted portion is performed (S).
4, S5). When the above processing is continuously performed, a high-level portion (a portion filled with black) is deleted as shown in FIG. 5, but the area of the deleted portion is S3. 7 of the area determined in the step
It is determined whether it has become 0% or less. This area is 7
Until it becomes 0% or less, the processing of S5 is performed, and the high-level portions are sequentially deleted. On the other hand, when it becomes 70% or less,
Calculation of the center of gravity in the cell direction in the remaining shape is performed (S6, S7).

As described above, since the area of the high-level portion is deleted by a predetermined ratio with respect to the entire area of the application target area, the error of the video signal having a protruding peak is particularly effectively absorbed. be able to. For example, as shown in FIG. 5, if this processing is performed on a video signal indicated by a dotted line including an error accompanied by a speckle phenomenon, a hatched portion is deleted, and the position of the center of gravity becomes The position is almost the same as the normal video signal. By performing the above processing while rotating the reflection mirror 4 little by little, distance measurement value sequence data as shown in FIG. 10 is obtained, and a straight line is drawn by the least square method based on this data.
The shape of the measurement object can be obtained.

In the above embodiment, a method using a one-dimensional line sensor is exemplified. However, the present invention is not limited to this, and the method of the present invention can be applied to a method using a two-dimensional line sensor. can do. However, when a two-dimensional line sensor is used, the volume is subtracted instead of the area.

[0012]

As described above, according to the present invention, an input laser reflected light is captured by a large number of photoelectric conversion elements, and is converted into an electric signal of a level corresponding to the reflected light intensity for each of the photoelectric conversion elements. Until the area of the graph created by plotting the level of the converted electric signal in the order of the photoelectric conversion elements is reduced by a predetermined ratio, the level of the photoelectric conversion element presenting the highest level at present is sequentially reduced, and the area is reduced to a predetermined ratio. Since the position of the center of gravity in the direction of the photoelectric conversion element in the graph is calculated, it is possible to effectively suppress the occurrence of an error in the calculation of the center of gravity of a video signal having a prominent peak.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for realizing an image signal processing method according to the present invention.

FIG. 2 is an operation flowchart of the apparatus shown in FIG. 1;

FIG. 3 is a diagram illustrating an example of a video signal obtained by laser reflected light from a measurement object.

FIG. 4 is an explanatory diagram of a step of multi-leveling the video signal of FIG. 3;

FIG. 5 is an explanatory diagram of a step of cutting the vicinity of a peak of a video signal after multilevel conversion in FIG. 4;

FIG. 6 is a diagram showing an example of a video signal obtained by a conventional device.

FIG. 7 is a diagram showing a shape of a measurement target obtained based on a video signal obtained by a conventional device.

FIG. 8 is a diagram for explaining a method conventionally used for reducing a measurement error.

FIG. 9 is a diagram for explaining a method conventionally used for reducing a measurement error.

FIG. 10 is a diagram illustrating an example of a shape of a measurement target that should be originally obtained.

[Explanation of symbols]

1. Shape measuring sensor 2. Laser light generating means
DESCRIPTION OF SYMBOLS 3 ... Measurement object 4 ... Reflection mirror 5 ... Lens system 6 ... CCD camera 7 ... Servo motor 8 ... Encoder 10 ... Sensor control board 12 ... Data processing device

Claims (1)

(57) [Claims] A step of irradiating the object to be measured with laser light and inputting laser reflected light from the object to be measured; capturing the input laser reflected light with a large number of photoelectric conversion elements;
A step of converting each of the photoelectric conversion elements into an electric signal having a level corresponding to the reflected light intensity; and An image signal processing method comprising: sequentially reducing the level of the photoelectric conversion element exhibiting the highest level; and calculating the position of the center of gravity of the graph in which the area is reduced to a predetermined ratio in the direction of the photoelectric conversion element. .