JP2620982B2 - Position detection method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detection method for accurately detecting the shape and position of a target object from a light-receiving spot even when a blind spot or secondary reflection occurs.

(Prior Art) Conventionally, in order to detect the height of the object surface of an object by light, it is often the case that the height is detected by triangulation with light (hereinafter referred to as light cutting). This is shown in FIG.
A light beam is applied to the surface of the object 20 from directly above, the reflected light is imaged on the position detection sensor 22 by the lens 21, and the height of the object 20 is detected based on the imaged position.

However, in this method, if the surface of the object 20 is a glossy surface, in the case of the object 23 as shown in FIG. The spot is imaged. For this reason, the position detection sensor 22 based on the secondary reflection from the secondary reflection point R8 without detecting the true height (true detection point which is the spot light position) P8 of the object 23.
There is a drawback that R8 ″ lower than the actual height is detected by the upper image R8 ′.

Further, as shown in FIG. 9, the reflected light of the incident light beam 2 may become a blind spot of another object 24 and may not be detected.

In order to solve these drawbacks, a "shape detecting device" disclosed in Japanese Patent Publication No. Sho 63-22241 has been proposed. In this method, as shown in Fig. 10, since abnormal reflection occurs on the surface of the object to be measured, it is intended to selectively extract light cuts by utilizing the fact that the abnormal reflection part exists below the slit bright line. Met.

(Problems to be Solved by the Invention) However, in this method, as shown in FIG. 11, for example, when the detected object 25 has an inclined surface 26 on one side and a convex The beam is reflected at the point P11, which is the spot light position, forms an image of the spot 11 'on the position detection sensor 22 through the lens 21, and the beam is reflected from the point R11, which is the secondary reflected spot light position on the inclined surface 26, from the point R11. Another spot R11 'is imaged by the reflected light. The image of the spot R11 'appears at the intersection R11 ″ of the incident light of the light beam and the reflected light from the point R11, and the intensity of the light is large and exists above the true detection point P11 which is the spot light position. This has a drawback that it is difficult to apply when the detected object 25 has a complicated shape.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a position detection method that does not cause erroneous detection due to the influence of secondary reflection, blind spots, and the like even when a detected object has a complicated shape. What you want to do.

(Means for Solving the Problems) In order to achieve the above object, a position detection method according to the present invention comprises: a light beam incident on an object to be detected; and the incident light beam incident at a spot light position on the object to be detected. In the position detection method of receiving the reflected light of the object and detecting the position of the detected object using a spot position detection sensor that detects a change in the position of the light receiving spot due to the reception of the reflected light, the spot incident light beam as an axis A spot position detection sensor is arranged at a plurality of positions where the position detection sensor is rotated,
From the position detection signals of the spot position detection sensors obtained from the respective disposed positions, a position where the spot position detection sensor is provided as a predetermined position detection signal is selected, and the position detection of the selected spot position detection sensor is performed. The position of the detected object is detected based on the signal.

(Operation) In the position detection method configured as described above, the spot position detection sensors for detecting a change in the position of the light receiving spot are provided at a plurality of positions different from each other by a rotation angle with respect to the axis of the incident light beam. Since the position of the spot position detection sensor serving as a predetermined position detection signal is selected from the position detection signals of the spot position detection sensors obtained from the respective positions, the accurate spot light position can be detected.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS.

In light cutting, if the incident angle of the reflected light to the spot position detection sensor is constant with respect to the incident direction of the incident light beam, the same applies even if the position of the spot position detection sensor is rotated around the incident light beam as an axis. It is possible to detect the spot light position.

Here, if a line-type sensor is used as the spot position detection sensor, the spot light position hitting the detected object is on the incident light beam if there is no blind spot or secondary reflection, and the line-type sensor is in the same plane as this incident light beam. When arranged at such a position, the spot light is always imaged on the line sensor. If the secondary reflection occurs, the secondary reflection spot is imaged on the line sensor only when the secondary reflection spot light is generated on the above-mentioned plane, and the true spot light position is the secondary reflection spot light. And accurate position detection becomes impossible. However, when the position of the line sensor is rotated about the incident light beam together with the lens, the plane formed by the incident light beam and the line sensor rotates,
A state where the secondary reflected light is not on this plane can be realized.

That is, as shown in FIG. 1, when detecting the position of the point M which is the spot light position on the inclined surface 1a of the detected object 1, the incident light beam 2 is incident from just above the point M. The line type sensor 3 as a spot position detection sensor is located at the position A with respect to the light beam 2 via the lens 7;
Assuming that two spots M 'and N' are imaged on the line type sensor 3, this spot N 'is the secondary reflected light spot at the point N where the incident light beam 2 is the secondary reflected spot light position. is there. This means that an image formed by two spots M 'and N' is formed on a plane A including the incident light beam 2, the spot M 'formed by the spot light at the point M, and the spot N' formed by the secondary reflected light spot at the point N. It has appeared.

In such a case, the rotation is made around the incident light beam 2 without changing the relative positional relationship between the lens 7 and the line-type sensor 3, and one spot MB on the line-type sensor 3 at the position B on the plane B. When only 'is imaged, this spot MB' is due to the spot light at M points. This is shown in FIG.

In FIG. 2, (a) is a detection waveform of the line sensor 3 at the position A, and (b) is a detection waveform of the line sensor 3 at the position B. The two detection waveforms are compared. Thus, it can be seen that the waveforms of M ′ and MB ′ are true spot light waveforms.

The blind spot correction can be performed in the same manner. In FIG. 3, a spot light is generated at the point M by the incident light beam 2 and the line type sensor 3 is located at the position A via the lens 7 to obtain an image. When image formation does not appear, a part of the object 4 enters as a blind spot between the spot light position M and the line sensor 3. In this case, the positions of the lens 7 and the line-type sensor 3 are changed by rotating the incident light beam 2 as an axis,
The spot light on the detected object 1 moves to the position B where the spot light is not blocked by the object 4, and an image of the spot M ′ can be formed on the line sensor 3 at the position B.

Thus, as shown in FIG. 4, the detection signal at the position A is not detected because the spot light is blocked, as shown in FIG. Next, in the detection signal at the position B, the peak point of the light amount appears as an image as shown in FIG. In this case, the above (a)
By combining (b) with (b), a combined output of (c) is obtained. This operation is performed at a plurality of locations, and the line sensor 3 containing no secondary reflected light is selected by employing the output signal with the smallest light amount among the output signals. This enables blind spot correction.

In this way, even if there is a blind spot, by rotating the incident light beam 2 around the center without changing the relative positional relationship between the lens 7 and the line-type sensor 3, erroneous detection due to the blind spot can be made by selecting the detection waveform. Can also be removed.

Next, a selection method when a plurality of line-type sensors 3 are used will be described. This plurality of line type sensors 3
In order to prevent the occurrence of blind spots, for example, if they are arranged in advance at the positions A and B as shown in FIG.
As shown in the figure, the detection signal at the position A and the detection signal at the position B can be simultaneously detected, and by synthesizing them, the synthesized output shown in (c) can be easily obtained. Further, the line-type sensor 3 disposed at the A position and the B position
Is rotated by a fixed angle about the axis of the incident light beam 2 to synthesize the detection signals at each position, and by synthesizing the respective signals, even if the detection object 1 has a complicated form, A simple position detection signal can be detected. As the detection signal, a signal having the smallest light amount may be selected from the output signals captured by the respective line sensors 3.

Generally, when the secondary reflection occurs and is detected by the line sensor 3, the amount of the secondary reflected spot light becomes larger than the true spot light. This is due to the fact that the surface
As shown in the figure, the light is perpendicular to the plane formed by the line-type sensor 3 and the incident light beam 2 and the direction in which the amount of reflected light is the largest. The above-described combined output signal including the line type sensor 3 is larger than the other combined output signals when compared at all light amounts. For this reason, if the signal having the weakest light amount of the combined output signal is selected, it is possible to accurately detect the spot light position. Here, the line type sensor 3 is composed of a light receiving element arranged in a slender form, and represents a peak value of the spot light on a straight line, and a position sensitive detector for directly detecting the position of the spot light. The same effect can be obtained by using a device such as (PSD) and selecting a device having the minimum combined light amount.

In addition, an array sensor having a large number of light receiving elements arranged in the spot movement direction is used as a spot position detection sensor, and array sensors are arranged at a plurality of positions as described above. Are combined. Then, an array sensor having a small number of peak values equal to or more than a certain value may be employed by using the combined output signal. In this case, if the secondary reflected light beam enters as shown in FIG. 2, it has a peak value in addition to the true spot position, and the combined output signal naturally has a plurality of peak values.

The composite output signal to which the secondary reflected beam light is not incident is
By using the signal only with the peak value of the true spot light, the true spot position can be easily and accurately obtained. That is, it is possible to remove the influence of the secondary reflected beam of the detection target object 1 by employing an array sensor having the smallest number of peak values among the combined output signals.

A true spot position can be detected by employing, from the output signals, the one having the largest number of peak values at the same location among the output signals, which is equal to or higher than a certain value, using the above-described array sensor. The method will be described below.

The output signal of each array sensor has various peak values due to the secondary reflected light beam, and the true spot light may disappear due to the blind spot.

However, the peak positions of a plurality of array sensors are extracted, and the probability of becoming the true spot position from the peak position with the largest number of occurrences is high, and the probability increases as the number of array sensors increases. This makes it possible to detect the true spot position.

FIG. 6 is a block diagram of an apparatus for calculating a spot position used in each of the above-described detection methods. The spot position calculation section 6 includes a minimum peak value number sensor detection section, a minimum detection light quantity sensor detection section, and a maximum occurrence frequency peak. It comprises a position detecting section and a spot position calculating section. The outputs of the light receiving elements (spot position detecting sensors) of n columns are input to the spot position calculating section 6 via the line memory of the n columns, and the minimum peak value, the minimum light amount, and the maximum It is input to each block according to the frequency of occurrence. The output after each detection is input to the spot position calculation unit to determine the true spot position, and is input to the spot position memory unit and stored. The minimum peak value number sensor detection unit, the minimum detection light amount sensor detection unit, and the maximum occurrence frequency peak position detection unit in the spot position calculation unit 6 are adapted to each system corresponding to the structure according to the structure of the spot position detection sensor. You may comprise.

(Effects of the Invention) As described above in detail, the position detection method of the present invention includes a method of irradiating a light beam on an object to be detected and reflecting the incident light beam at a spot light position on the object to be detected. In a position detecting method for detecting the position of an object to be detected using a spot position detecting sensor that receives light and detects a change in the position of a light receiving spot due to the reception of the reflected light, a spot position detection is performed with a spot incident light beam as an axis A spot position detection sensor is provided at a plurality of positions where the sensor is rotated, and a spot position detection sensor that becomes a predetermined position detection signal from a position detection signal of the spot position detection sensor obtained from each of the provided positions. The selected position is selected, and the position of the detected object is detected based on the position detection signal of the selected spot position detection sensor. Object also secondary reflection a complicated shape, there is an advantage not to generate the erroneous detection due to the influence of such blind spots.

In addition, the spot position detection sensor is rotated about the spot incident light beam as an axis, and the sensor may be the same spot position detection sensor. In this case, there is an advantage that there is no need to arrange a large number of sensors with high accuracy. There is.

[Brief description of the drawings]

1 to 6 show an embodiment of the present invention. FIG. 1 is a perspective view showing an image forming state when a sensor position is changed. FIGS. 2 (a) and 2 (b) show detection at each sensor position. In the waveform diagram,
FIG. 3A is a view with secondary reflection, FIG. 3B is a view without secondary reflection, FIG. 3 is a plan view showing a detection position for correcting a blind spot, FIG. 4A, FIG. c) is a waveform diagram at each sensor position in FIG. 3, (a) is inside the blind spot, (b) is outside the blind spot,
(C) is a composite of (a) and (b), FIG. 5 is a plan view showing the distribution of reflection intensity generated on an inclined surface or the like, and FIG. 6 is a block diagram, and FIGS. Figure 11 shows a conventional example.
FIG. 7 is a triangulation diagram, FIG. 8 is an example of a secondary reflection of a specular object,
9 is an example of a blind spot, FIG. 10 is an image formed by secondary reflection, and FIG.
The figure shows an example of reflection of a complex shaped object. DESCRIPTION OF SYMBOLS 1 ... Detected object 1a ... Slope surface 2 ... Incident light beam 3 ... Spot position detection sensor (line type sensor) 4 ... Object 6 ... Spot position calculation part 7 ... Lens 20 ... Object 21 ... … Lens 22… Position detection sensor 23… Object 24… Object 25… Detected object 26… Slope surface 27… Convex surface M, P, P8… Spot light position N, R8… Secondary spot Light position

Claims (5)

(57) [Claims] 1. A light beam is incident on an object to be detected, a reflected light of the incident light beam is received at a spot light position on the object to be detected, and a position change of a light receiving spot due to the reception of the reflected light is performed. In the position detection method for detecting the position of the detected object using the spot position detection sensor for detecting the spot position, the spot position detection sensors are arranged at a plurality of positions where the spot position detection sensor is rotated around the spot incident light beam as an axis. And selecting a position where the spot position detection sensor is provided as a predetermined position detection signal from the position detection signal of the spot position detection sensor obtained from each of the provided positions. A position detection method comprising detecting the position of a detected object based on a position detection signal. 2. A position detecting method according to claim 1, wherein a position detecting signal is obtained from a plurality of arranged positions using the same spot position detecting sensor by rotating the incident light beam as an axis. . 3. A combined output signal obtained by combining two position detection signals among the position detection signals obtained from the respective arranged positions, and employing a combination having a peak value equal to or more than a certain value among the combinations. 2. The position detecting method according to claim 1, wherein the position at which the spot position detecting sensor is disposed is selected. 4. A combined output signal obtained by combining two position detection signals among the position detection signals obtained from the respective arranged positions, and employing a combination having the least light quantity among the combinations, 2. The position detection method according to claim 1, wherein a position where the detection sensor is provided is selected. 5. The method according to claim 5, wherein a position detection signal obtained from each of said arranged positions has a peak value equal to or greater than a certain value and has the largest number of peak values existing in the same place. 2. The position detecting method according to claim 1, wherein the set position is selected.