JP2003148920A - Edge detecting sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an edge detecting sensor capable of preventing the wrong detection of the edge position of an object to be detected as much as possible. SOLUTION: A control circuit detects the position where a light receiving level is a threshold or less by a threshold detecting routine (step S1), and determines and outputs, when the position is detected by the threshold detecting routine, this position as the edge position of the object to be detected (step S3). The control circuit detects the position where the light receiving level is minimized by a peak detecting routine when it is judged that the position detection by the threshold detection routine is impossible, and determines and outputs this position as the edge position of the object to be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge detecting sensor for detecting an edge position of a detected object based on a light receiving level.

[0002]

This type of edge detection sensor receives the light emitted from the light source by the light receiving means through the object to be detected, and detects the change in the light reception level to detect the edge of the object to be detected. The position is detected, and a threshold detection method is a typical detection method of these. This threshold value detection method is a method of determining a predetermined threshold value, determining that the received light level exceeds the threshold value, and detecting the position as the edge position of the detected object.

11 (a) to 11 (c) schematically show an example of a position to be detected based on a threshold value detection method and a corresponding light receiving level in a transmission type edge detection sensor, for example. FIG. 11A shows an opaque detected object 1
The case where the edge of is detected is shown. In this case, the edge detection sensor can detect the edge position of the object to be detected 1 by determining that there is a light receiving level at which the light receiving level detected by the light receiving unit is equal to or lower than the predetermined threshold value α. .

FIG. 11 (b) shows a case where the edge of the transparent object 2 to be detected is detected. In this case, although the light receiving level detected by the light receiving means exceeds the threshold value α, the edge detection sensor utilizes the fact that the refraction state changes at the edge portion of the detected object 2 and uses the predetermined threshold. The edge position of the object to be detected can be detected by determining the presence of the light receiving level that is less than or equal to the value.

FIG. 11C shows a case where an edge of a transparent detected object 3 having an acute-angled edge different from the shape of the edge of the detected object 2 shown in FIG. 11B is detected. . In this case, the light receiving level may increase overall with respect to the light receiving level corresponding to the edge of the detected object 2 shown in FIG. 11B, and since the light receiving level has not reached the level below the threshold value α, Even if the edge of the detected object 3 exists, it may be undetected. It is known that this occurs because a difference in optical characteristics such as a refraction state of the edge of the detected object 3 occurs for each detected object.

Therefore, a peak detection method has been considered in order to solve such a problem. The peak detection method is a method of obtaining a minimum light reception level and detecting a portion corresponding to the minimum level as an edge position of the detected object 3. FIG. 12 shows the principle of edge detection based on the peak detection method so as to solve the problem of FIG. 11 (c). According to this method, it is possible to detect the edge position of the transparent object 3 to be detected by the light receiving means detecting the minimum light receiving level.

However, in the peak detection method,
When detecting the edge of the opaque detected object 1, it is considered that the edge of the detected object 1 cannot be detected because the minimum level of the light receiving level has no peak.

The above example shows an example in which the light receiving level decreases when detecting the edge, but when the light receiving level rises, such as in a reflection type edge detection sensor, the edge is detected. The same problem can be considered in the edge detection sensor for detecting.

The present invention has been made in view of the above circumstances, and an object thereof is to detect an edge position regardless of whether an object to be detected is transparent or opaque, and to detect the edge of the object to be detected. An object of the present invention is to provide an edge detection sensor capable of preventing erroneous detection of an edge as much as possible even if a light receiving level changes due to a difference in optical characteristics such as refraction in the vicinity.

[0010]

In order to solve the above problems, an edge detection sensor according to claim 1 has a light receiving element provided corresponding to a light source, and a position is detected based on an output from the light receiving element. A light receiving means for detecting a light receiving level corresponding to, a first detecting means for detecting a position where the light receiving level of the light receiving means is below a predetermined threshold value, and a position where the light receiving level of the light receiving means is a minimum level. And a position detected by the first detection unit as the edge position of the object to be detected, and if the position detected by the first detection unit does not exist, the second detection unit detects It is characterized in that it is provided with a judging means for judging the detected position as the edge position of the detected object.

The present invention is suitable when the fact that the light receiving level is lowered when the edge position of the object to be detected is detected. That is, according to such means, the first
The detecting means detects the position where the light receiving level of the light receiving means is less than or equal to a predetermined threshold value, and the determining means determines the position detected by the first detecting means as the edge position of the detected object.

Therefore, for example, when detecting an edge of an opaque object to be detected, the position of the edge of the object to be detected cannot be detected because there is always a position where the light receiving level of the light receiving means is below a predetermined threshold value. It becomes possible, and the position detected by the first detecting means is judged as the position of the edge.

By the way, for example, when detecting the edge position of a transparent object to be detected, the light receiving level of the light receiving means may not fall below a predetermined threshold value. In such a case, the first detecting means Since there is no position detected by the above, the determination unit determines that the position detected by the second detection unit is the edge position of the detected object. At this time, the second detecting means determines the position where the light receiving level of the light receiving means is at the minimum level as the edge position of the detected object, so that the edge position of the detected object can be detected.

As a result, the edge position can be detected regardless of whether the object to be detected is transparent or opaque, and the light receiving level changes due to the difference in optical characteristics near the edge of the object to be detected. Even in this case, the detection method can be automatically changed to prevent erroneous detection of the edge position of the detected object as much as possible.

An edge detecting sensor according to a second aspect of the present invention has a light receiving element provided corresponding to a light source, and a light receiving means for detecting a light receiving level corresponding to a position based on an output from the light receiving element, and the light receiving element. First detecting means for detecting a position at which the light receiving level of the means exceeds a predetermined threshold value, second detecting means for detecting a position at which the light receiving level of the light receiving means reaches the maximum level, and first detection Determination means for determining the position detected by the means as the edge position of the object to be detected, and determining the position detected by the second detection means as the edge position of the object to be detected when the position detected by the first detection means does not exist. It is characterized by having and.

The present invention is suitable when the fact that the received light level rises is used when detecting an object to be detected.
That is, according to such means, the first detecting means detects the position where the light receiving level of the light receiving means becomes equal to or higher than the predetermined threshold value, and the judging means detects the position detected by the first detecting means as an edge. Judge as the position.

Therefore, for example, when detecting the edge of an opaque object to be detected, there is always a position where the light receiving level of the light receiving means is equal to or higher than a predetermined threshold value, and therefore the position of the edge of the object to be detected cannot be detected. It becomes possible, and the position detected by the first detecting means is output as the position of the edge.

Further, for example, when detecting an edge position of a transparent object to be detected, the light receiving level of the light receiving means may not exceed a predetermined threshold value. In such a case, the first detecting means is used. Since there is no detected position by the determination unit, the determination unit determines that the detection position by the second detection unit is the edge position of the detected object. At this time, the second
Since the position detected by the detecting means is determined as the edge position of the detected object, the position of the edge of the detected object can be detected.

As a result, the edge position can be detected regardless of whether the object to be detected is transparent or opaque, and the light receiving level changes due to the difference in optical characteristics near the edge of the object to be detected. However, by automatically changing the detection method, it is possible to prevent erroneous detection of the edge position of the detected object as much as possible.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) The present invention will be described below with reference to a one-dimensional transmission type used for detecting an edge (hereinafter referred to as an edge) of a transparent glass wafer (corresponding to an object to be detected). A first embodiment applied to an edge detection sensor will be described with reference to FIGS. 1 to 6.

FIG. 2 schematically shows the overall structure.
In FIG. 2, the light source 11 is configured to include an LED (not shown), and emits light toward the detection area A at a predetermined timing according to a control signal from the connected control circuit 12. .

The control circuit 12 includes a CPU, RA (not shown).
It is composed of M, ROM, etc., and controls the operation of the light receiving means 13 connected to the control circuit 12 according to a program stored in the ROM.

FIG. 3 shows an electrical configuration of the control circuit 12. In FIG. 3, the first shown in the control circuit 12
The detection means 12a, the second detection means 12b and the determination means 12c are functional blocks achieved by a program stored in the ROM. In addition, the RAM has a work area,
An area for storing a light receiving level described later is secured. The address of this RAM is set corresponding to the position of the detection area.

The light receiving means 13 is composed of, for example, a so-called CCD image sensor. This is a plurality of CCDs (Charge Coupl
ed Device) element (corresponding to the light-receiving element in the present invention), for example, a CCD sensor unit, and is arranged to face the light source 11. The light emitted from the light source 11 passes through the detection area A to a predetermined position. The light is received at a timing, the light receiving level is detected by the output from each CCD element, and is output to the control circuit 12. Light source 11
An object to be detected 14 made of a transparent glass wafer is conveyed and positioned between the light receiving means 13 and the light receiving means 13.

The operation of the above structure will be described with reference to FIGS. 1 and 4 to 6. FIG. 1 is a flowchart showing a flow of edge detection performed by a one-dimensional edge detection sensor. In the edge detection determination routine in FIG. 1, the first detection means 12a in the control circuit 12 detects the edge position of the detected object 14 by the threshold value detection routine described later (step S1).

<Regarding Position Detection by Threshold Detection Routine> Hereinafter, position detection by the threshold detection routine performed by the first detecting means will be described with reference to FIG. When light is emitted from the light source 11, the light receiving means 13 causes C
Light is received by the CD element (step T1), and the light receiving level corresponding to the position is set to 2 based on the output from the CCD element.
It is detected at the 56th (= 8th power of 2) stage and is output to the control circuit 12.

The control circuit 12 stores the light receiving levels output from the CCD elements as D (1) to D (k) (k indicates the number of CCD elements and the number of light receiving levels) (step T).
2). The control circuit 2 reads a predetermined threshold value α set in advance (step T3), and determines whether or not there are light reception levels D (1) to D (k) below this threshold value α, as follows. It is determined by the routine of steps T4 to T13.

The control circuit 2 substitutes 1 for the variable n (step T4) and reads the light receiving level D (n) (step T4).
5) If D (n) is less than or equal to the threshold value α (step T6: Yes), the addresses of the RAM storing D (n) are sequentially stored (step T7). If D (n) is not less than or equal to the threshold value α (step T6: N
o), the process proceeds to step T8.

At step T8, the control circuit 12
If the variable n does not match the number k of received light levels (step T8: No), the variable n is incremented (step T9) and steps T5 to T9 are repeated. Received light level D
When (n) is read and it is determined whether or not the threshold value is equal to or less than the threshold value α, the control circuit 2 determines in step T8 that the variable n matches the light reception level number k, The process proceeds to step T10.

In this case, the control circuit 12 executes step T7.
It is determined whether or not even one address of the RAM stored in is stored (step T10), and if the address is stored, all the stored addresses are detected (step T11), and this address is stored. The edge position of the detected object 14 is detected by deriving the corresponding detection position from (step T12). Incidentally, step T10
In, when the RAM address is not stored,
In other words, when none of the light receiving levels D (1), ..., D (k) is less than or equal to the threshold value α, the control circuit 2 determines that position detection is impossible (step T1).
3). As described above, when the position is detected by the threshold detection routine, the position is detected, and when the position is not detected, it is determined that the position cannot be detected.

Then, the judgment means 12c of the control circuit 12
If the position is detected as shown in FIG. 1 as a result of executing the edge detection routine as described above (step S
2: Yes), the position detected by the threshold detection routine is determined as the edge position of the detected object 14 and output (step S3).

Even if the detected object 14 is transparent, the edge position of the detected object 14 can be detected by executing the threshold detection routine as described above.

However, when the transparent detection object 14 having an acute-angled edge as shown in FIG. 6 is detected by the threshold detection method described above, when the light receiving level of the light receiving means 13 does not fall below the threshold value. In such a case, the edge position of the detected object 14 cannot be detected.

Therefore, the second detecting means 1 of the control circuit 12
As shown in FIG. 1, when the position is not detected in step S2 (step S2: No), 2b detects the position by the peak detection routine (step S2).
4).

<Regarding Position Detection by Peak Detection Routine> The flow of position detection by the peak detection routine performed by the second detecting means 12b will be described below with reference to the flowchart of FIG. The second detecting means 12b is RA
The light receiving levels D (1) to D (k) stored in M are read (step U1). The second detection means 12b sets the variable n to 1 and compares it with the minimum level D (n) min (step U2). This minimum level D (n) min is preset to the maximum value that the light receiving levels D (1) to D (k) can take at the time of starting the position detection by this peak detection routine.

The second detecting means 12b has a light receiving level D
(N) is compared with the minimum level D (n) min (step U2), and the received light level D (n) is the minimum level D (n) m.
If it is less than in, the light reception level D (n) is substituted and stored as the minimum level D (n) min, and the address of the RAM in which the light reception level D (n) is stored is also stored (step U3). In step U2, if the received light level D (n) is not lower than the minimum level D (n) min, the process of step U3 is not performed and step U3 is not performed.
Go to 4.

The second detecting means 12b determines whether or not the variable n matches the light receiving level number k (step U).
4) If they do not match, the variable n is incremented (step U5) and steps U2 to U5 are repeated.
In step U4, when the variable n matches the light receiving level number k, the second detecting means 12b detects all the RAM addresses stored in step U3 (step U6), and responds from this address. The position is detected by deriving the position of the detection area A (step U7).

Then, the judgment means 12c of the control circuit 12
As shown in FIG. 1, the position detected by the peak detection routine as described above is determined as the edge position of the detected object 14 and is output (step S5).

According to the first embodiment, the control circuit 12 first determines the position detected by the threshold detection routine as the edge position of the detected object 14 and outputs it.
When the position cannot be detected by the threshold detection routine, the position having the minimum level among the light receiving levels is judged as the edge position of the detected object 14 and is output, so that the detected object 14 is transparent. The edge position can be detected even if it is opaque, and the edge position of the detected object 14 is erroneously detected even if the received light level changes due to a difference in optical characteristics near the edge of the detected object 14. Can be prevented as much as possible.

Further, since the threshold detection routine is executed with priority over the peak detection routine, the detection accuracy of the edge of the detected object 14 can be maximized.

(Second Embodiment) FIGS. 7 and 8 show a second embodiment of the present invention. The difference from the first embodiment is that it has a single laser light source. And the light receiving means has a single light receiving element, and the object to be detected 14 is conveyed between the light source and the light receiving means by a driving device (not shown) and positioned. It has been applied to a scanning edge detection sensor. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 7 schematically shows the overall structure.
The light source 15 has a single laser light source (not shown), and irradiates the scanning mirror 16 with light at a predetermined timing according to a control signal from the connected control circuit 12.

The scanning mirror 16 is connected to the control circuit 12 via a drive circuit 17, and is adapted to scan an irradiated laser beam to a predetermined area by reflection in response to a control signal from the control circuit 12. There is. The scanning mirror 16
May be configured by a polygon mirror or the like.

The light projecting lens 18 makes the scanned laser light substantially parallel to the detection area (see the arrow X direction in FIG. 6 which shows the direction in which the light is guided), and the light receiving lens 19
Is configured to guide the guided light to the light receiving means 20.

The light receiving means 20 is configured to have a light receiving element such as a photodiode, and the light receiving lens 1
The light guided from 9 is received, the light receiving level corresponding to the detection area A is detected, and it is output to the connected control circuit 12.

The driving device (not shown) is configured to have a rotary encoder for position detection, and the detected object 14 is substantially perpendicular to the light irradiation direction (see arrow Y direction in FIG. 7). Is configured to be movable.

The rest of the configuration is the same as that of the first embodiment, so its explanation is omitted. The operation of the above configuration will be described. The difference from the first embodiment is the position detection by the threshold value detection routine shown in FIG.

In the scanning edge detection sensor, the control circuit 12 sets the variable n to 1 (step V1), drives and controls the scanning mirror 16 to the initial position, and starts irradiation of light from the light source 15 (step V2). ). The light receiving means 20 is
Light is received by the light receiving element (step V3), and the light receiving level D
(N) is stored in a predetermined address in the RAM area associated with the position of the detection area A (step V4).

Here, the control circuit 12 determines whether or not the variable n matches the number k of received light levels (step V
5) If they do not match, n is incremented (step V6) and the scanning mirror 16 is drive-controlled by a predetermined step (step V7). In this case, the scanning mirror 16 is driven and controlled at every predetermined scanning step. Then, steps V3 to V7 are repeated, and in step V5, when the variable n matches the light receiving level number k, that is, the light receiving means 20 detects the light receiving level corresponding to the position by the light receiving level number k times, and the control circuit 12 determines. When the received light levels are stored as D (1) to D (k), the process proceeds to step V8.

The control circuit 12 reads a predetermined threshold value α (step V8), and the threshold value α is D (1), ..., D.
It is determined whether or not each of the values of (k) is equal to or more than each value, in other words, whether each of the light receiving levels D (1), ..., D (k) is equal to or less than the threshold value α (step V
9). The control circuit 2 receives the light receiving levels D (1), ..., D
When it is determined that any of the values in (k) becomes equal to or less than the threshold value α (step V9: Yes), the light receiving level D
Among the (1), ..., D (k), the address at which the received light level below the threshold value α is stored is detected (step V10). Then, the edge position of the detected object 14 is detected based on the detected address (step V1).
1). At this time, the edge position can be detected by deriving the position of the corresponding detection area A from the address.

At step V9, the received light level D
Any of the values of (1), ..., D (k) is the threshold value α.
If it is determined that the following is not true (step V9: N
o) The position detection is disabled (step V12), and the position detection by the threshold value detection routine ends. In this way, when it is determined that the position cannot be detected, the position is detected by the peak detection routine. The peak detection routine is substantially the same as that of the first embodiment, and therefore its explanation is omitted.

According to such a second embodiment, the first
It is possible to obtain substantially the same operational effects as the operational effects of the above embodiment.

(Third Embodiment) FIG. 9 shows a third embodiment of the present invention.
However, the difference from the first or second embodiment is that the light source is configured with a single light projecting element, and the light receiving means has a single light receiving element. The present invention is applied to a single optical axis edge detection sensor configured such that the light emitting and receiving device equipped with the light source and the light receiving means is configured to operate relative to the object to be detected. The same parts as those in the first or second embodiment are designated by the same reference numerals and the description thereof will be omitted.

The light emitting / receiving device 21 is equipped with the light source 15 and the light receiving means 20, and the light emitting / receiving device 21 is configured to be movable in the direction of arrow Y in FIG. In this case, the light source 15 is a laser light source, and its light beam is extremely thin.

As in the second embodiment, the light source 15 emits light based on the control signal from the control circuit 12, and the light source 1 emits light.
The light emitted from 5 is received by the light receiving means 20. In this case, the light emitting / receiving device 21 is operated in the direction of the arrow Y in FIG. 9 by a predetermined step by a driving device (not shown), the position is similarly detected by the threshold detection routine, and the position is detected by the threshold detection routine. If it is possible, the position detected by the threshold detection routine is judged as the edge position of the object 14 to be output, and if the position cannot be detected by the threshold detection routine, the peak detection routine is executed. The position detected by is determined as the edge position of the detected object 14 and is output. This makes it possible to obtain substantially the same operational effects as the operational effects of the first embodiment.

(Fourth Embodiment) FIG. 10 shows a fourth embodiment of the present invention. The difference from the third embodiment is that the object 14 to be detected has a light source 15 and a light receiving means 20. This is applied to a single optical axis edge detection sensor configured to operate in the arrow Y direction with respect to the mounted light emitting / receiving device 21.

Also in the fourth embodiment as described above, the object 14 to be detected and the light projecting / receiving device 21 are operated relatively, so that substantially the same effect as the third embodiment can be obtained. .

(Other Embodiments) In the above embodiments, the light source is the LED light source or the laser light source, but the light source is not limited to this.
A light source such as a fluorescent light source, a halogen lamp, or a fiber light source may be used.

In the above embodiment, the control circuit 2 includes the first detection means 2a, the second detection means 2b, and the determination means 2c.
The software is stored in the ROM of
The present invention is not limited to this, and may be configured by hardware or the like.

In the above embodiment, the present invention is applied to the one-dimensional edge detection sensor, the scanning type edge detection sensor, and the single optical axis edge detection sensor, but the present invention is not limited to this, and the two-dimensional edge detection sensor is used. Etc. may be applied.

The present invention can be applied to both a reflection type edge detection sensor and a transmission type edge detection sensor.

In the above embodiment, the detected object 14
This is applied to the case where the light reception level is lowered when detecting the object. However, the present invention is not limited to this, and the case where the light reception level is increased when detecting the detected object is used. Can also be applied to. In this case, if the position can be detected when the received light level becomes equal to or higher than a predetermined threshold value, the detection position by the threshold value detection routine is output as the edge position of the detected object to detect the threshold value. When the position cannot be detected by the routine, the position where the received light level becomes the maximum level is output as the edge position of the detected object, so that even if the detected object is transparent. Even if it is opaque, it is possible to detect the edge position, and it is possible to prevent erroneous detection of the edge as much as possible even if the light receiving level changes due to the difference in optical characteristics near the edge of the detected object.

[0063]

As described above, according to the present invention,
The position detected by the first detecting unit that detects the position where the light receiving level of the light receiving unit is less than or equal to a predetermined threshold value is determined as the edge position of the detected object, and the position cannot be detected by the first detecting unit. In this case, since the position detected by the second detecting unit that detects the position where the light receiving level of the light receiving unit is the minimum level is determined as the edge position of the detected object, even if the detected object is transparent, it is opaque. Even if the edge position can be detected, the false detection of the edge can be prevented as much as possible even if the light receiving level changes due to the difference in the optical characteristics near the edge of the detected object.

[Brief description of drawings]

FIG. 1 is a flowchart (No. 1) showing the operation of the one-dimensional edge detection sensor showing the first embodiment of the present invention.

FIG. 2 is a diagram showing a positional relationship among a light source, a light receiving unit, and a detected object.

FIG. 3 is a block diagram showing an electrical configuration.

FIG. 4 is a flowchart showing the operation of the one-dimensional edge detection sensor (No. 2).

FIG. 5 is a flowchart showing the operation of the one-dimensional edge detection sensor (part 3).

FIG. 6 is a diagram showing the positions of edges and their corresponding light reception levels.

FIG. 7 is a diagram corresponding to FIG. 2 showing a second embodiment of the present invention.

FIG. 8 is a view corresponding to FIG.

FIG. 9 is a view corresponding to FIG. 2 showing a third embodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 2 showing a fourth embodiment of the present invention.

11A to 11C are views corresponding to FIG. 6 showing a conventional example.

FIG. 12 is a view corresponding to FIG. 6 showing a conventional example.

[Explanation of symbols]

11 is a light source, 12 is a control circuit, 12a is a first detecting means, 12b is a second detecting means, 12c is a judging means, 13
Is a light receiving means, 14 is an object to be detected, 15 is a light source, 16 is a polygon mirror, 18 is a light projecting lens, 19 is a light receiving lens,
20 is a light receiving means, 21 is a light emitting and receiving device, and A is a detection area.

Claims (2)

[Claims] 1. A light receiving device having a light receiving element provided corresponding to a light source, and detecting a light receiving level corresponding to a position based on an output from the light receiving device, and a light receiving level of the light receiving device is predetermined. A first detecting means for detecting a position where the light receiving level of the light receiving means is a minimum level, a first detecting means for detecting a position where the light receiving level of the light receiving means is a minimum level, and a detected position by the first detecting means. Determination means for determining the edge position of the detected object as the edge position of the object to be detected when the detection position by the first detection means does not exist. Edge detection sensor. 2. A light receiving unit having a light receiving element provided corresponding to a light source, and detecting a light receiving level corresponding to a position based on an output from the light receiving unit, and a light receiving level of the light receiving unit is predetermined. First detection means for detecting a position above a threshold value, second detection means for detecting a position where the light receiving level of the light receiving means reaches the maximum level, and a detection position by the first detection means for the detected object. Determination means for determining the edge position of the detected object as the edge position of the object to be detected when the detection position by the first detection means does not exist. Edge detection sensor.