JP2003083808A - Photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric sensor capable of performing accurate detection of a detection object, measurement of an advance position or the like even if a slit is mounted. SOLUTION: A slit plate 26 having a proper opening area is selected from plural slit plates 26 corresponding to the size of the detection object W2, and the output signal level from a light receiving circuit 19 is stored as 'the maximum output signal level D1' in a storage part in the state where the slit plate 26 is not mounted and the detection object W2 does not exist in an optical path L1. Then the slit plate 26 is mounted, and the output signal level from the light receiving circuit 19 is stored as 'a detected output signal level D2' in the storage part. In this case, a CPU 20 calculates a light receiving ratio S (=D1/D2) from the maximum output signal level D1 and the detected output signal level D2 and stores it in the storage part, and multiplies the output signal level from the light receiving circuit 19 by the light receiving ratio at the 'detection mode' time and performs determination operation based on a conversion level.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photoelectric sensor.

[0002]

2. Description of the Related Art For example, a transmission type photoelectric sensor comprises a light projecting portion and a light receiving portion which are arranged to face each other, and a judging means which operates based on a light receiving amount level of the light receiving portion. If a detection object is present in the optical path of the light emitted from the light projecting means and entering the light receiving means, the light entering the light receiving section is blocked by the detection object, and the light receiving level of the light receiving section is lowered.
Therefore, the detection means can detect the detection object by comparing the level of the amount of light received by the light receiving section with the predetermined reference level.

Here, for example, if the detected object is extremely small, the amount of light shielded by the detected object also becomes small, so the rate of change in the amount of received light at the light receiving portion depending on the presence or absence of the detected object in the optical path is very small. become. Then, there arises a problem that stable detection cannot be performed because, for example, light from other than the light projecting portion, so-called ambient light, is easily received. Therefore, conventionally, by mounting a slit plate on the front surface of the light emitting unit or the light receiving unit to limit the light receiving range in the light receiving unit, the change rate of the light receiving amount level in the light receiving unit which changes depending on the presence or absence of the detected object is increased. On the other hand, a configuration has been considered in which the detection sensitivity is increased by increasing the gain of the light receiving amplifier, for example.

As an example thereof, there is a structure in which a plurality of slit plates having different opening areas are provided on the front surface of the light projecting portion or the light receiving portion in a replaceable manner. This is because, for example, a slit plate having an appropriate opening area is selected from the plurality of slit plates according to the size of the detection object and attached to the front surface of the light receiving unit, and then the detection sensitivity is adjusted. is there. With such a configuration, the slit plate is appropriately replaced according to the size of the detection object or the application of the photoelectric sensor, so that the light receiving range of the light receiving unit is adjusted to a desired range, and the light receiving amount of the light receiving unit is adjusted. You can increase the rate of change of level,
Therefore, it becomes possible to perform stable detection even for a minute detection object.

[0005]

However, in the structure in which the slit plate is attached to adjust the gain of the light receiving amplifier as described above, the gain adjustment work makes it possible to optimize the change ratio corresponding to the change rate increased by the slit plate. There is no guarantee that the detection sensitivity can be set accurately, and the problem that the detection object cannot be detected accurately may occur.

Further, for example, the transmissive displacement sensor has a rate of change of the light receiving amount level in the light receiving section which changes according to the degree of advance of the detection object existing in the optical path between the light projecting section and the light receiving section which are arranged opposite to each other. Based on this, the advancing position of the detected object is measured. Even in this case, while the slit plate is attached to increase the rate of change in the received light amount level, it is usual to increase the detection sensitivity, for example, by increasing the gain of the light receiving amplifier. However, there is no guarantee that the optimum detection sensitivity can be accurately set by the gain adjustment work, and it may not be possible to accurately measure the advancing position of the detection object.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a photoelectric sensor capable of accurately detecting a detection object and measuring an advance position even if a slit is attached. It is in.

[0008]

In order to achieve the above object, a photoelectric sensor according to a first aspect of the present invention is a photoelectric sensor that emits light into a detection region and a reflection of light emitted from the light projector. A photoelectric sensor including a light receiving unit that receives light or transmitted light, and a determination unit that operates according to the amount of light received by the light receiving unit that changes depending on the presence or absence of a detection object in the detection area. The light-receiving range limiting means, which is arranged in at least one of the light-receiving means and is capable of adjusting the light-receiving range in the light-receiving means to a desired range, and the light-receiving range limiting means, in the state where there is no detected object, The determining means includes a detecting means for detecting a light receiving ratio based on a light receiving amount before the light receiving range is limited and a light receiving amount after the light receiving range is limited by the light receiving range limiting means. , By light receiving means Characterized in place to operate on the basis of the conversion levels in terms based on the light ratio set amount of received light level detecting means.

A photoelectric sensor according to a second aspect of the present invention includes a light projecting means for emitting parallel light, a light receiving means arranged to face the light projecting means for receiving the parallel light, and existing in the optical path of the parallel light. In the photoelectric sensor including a determining unit that operates according to the amount of light received by the light receiving unit that changes depending on the amount of light shielding of the detected object, the light receiving unit is disposed in at least one of the light projecting unit and the light receiving unit. A light receiving range limiting means capable of adjusting the light receiving range at a desired range, and a light receiving amount before the light receiving range at the light receiving means is limited by the light receiving range limiting means in a state where no detection object exists in the optical path, The determining means detects the light receiving ratio based on the light receiving amount after the light receiving range of the light receiving range is limited by the light receiving range limiting means, and the determining means detects the light receiving amount level of the light receiving means. Set reception ratio It characterized in place to operate on the basis of the conversion levels in terms accordingly.

According to a third aspect of the invention, in the photoelectric sensor according to the first or second aspect, the light receiving range limiting means is
The feature is that the width of the light receiving range of the light receiving means in the same direction as the moving direction of the detection object is limited to adjust the light receiving range.

[0011]

<Advantages and Effects of the Invention><Inventions of Claims 1 and 2> According to the configuration of Claim 1, for example, first, in a state where no detection object exists in the detection region or in the optical path, the light receiving range of the light receiving means. The light receiving amount of the light receiving unit (hereinafter, referred to as “maximum light receiving amount”) is measured without any limitation. Then
The light receiving range limiting means adjusts the light receiving range of the light receiving unit in consideration of, for example, the size of the detected object. Then, when the amount of light received by the light receiving unit at that time (hereinafter referred to as "detected amount of received light") is measured, the light reception ratio is detected by the limit ratio setting means based on the maximum amount of received light and the detected amount of received light. Then, when the detection of the detected object is started, the determination unit operates based on the conversion level obtained by converting the level of the amount of light received by the light receiving unit according to the light reception ratio detected by the detection unit.

As described above, by adjusting the light receiving range of the light receiving unit by the light receiving range limiting means, it is possible to increase the rate of change in the light receiving amount level of the light receiving unit even for a minute detection object. Further, the determination means operates based on the light reception ratio, that is, the conversion level corresponding to the change rate of the light reception amount level of the light receiving portion changed by the light reception range limiting means. Therefore, unlike the conventional configuration in which the slit plate is attached to adjust the sensitivity, it is possible to set the optimum detection sensitivity corresponding to the change ratio without requiring the gain adjustment work of the light receiving amplifier, and thus the detection can be performed. It is possible to accurately detect an object and measure the advance position.

<Invention of Claim 3> According to the configuration of Claim 3, the light receiving range is adjusted by limiting the width in the same direction as the moving direction of the detected object by the light receiving range limiting means. To be done. Therefore, for example, it is possible to accurately perform detection of a minute detection object or measurement of a position and the like without limiting the detection width when determining the presence or absence of a detection object and the measurement width when measuring the position or width of the detection object. it can.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention.
3 through FIG. FIG. 1 is a diagram showing a hardware configuration of a transmission photoelectric sensor 10 to which the present invention is applied. As shown in FIG.
Is a light projecting unit 11 and a light receiving unit 12 that are arranged to face each other.
And a controller unit 13 for controlling them. Of these, the light projecting portion 11 is a light projecting element 15 that emits light toward the light projecting window 14a in the light projecting case 14 in which a slit-shaped opening (hereinafter referred to as "light projecting window 14a") is formed. And a light projecting circuit 16 for applying a drive signal to the light projecting element 15.

On the other hand, the light receiving portion 12 has a light receiving element 18 for receiving the light incident from the light receiving window 17a in a light receiving case 17 having a slit-shaped opening (hereinafter referred to as "light receiving window 17a"). A light receiving circuit 19 that outputs an output signal according to the amount of light received by the light receiving element 18 is provided.

The controller unit 13 includes a CPU 20.
Is provided. When a control signal is applied to the light projecting circuit 16 by the CPU 20, the light projecting element 15 emits light, and the parallel light L1 is emitted from the light projecting window 14a by a light projecting lens (not shown), for example. Then, the light receiving window 17a of the light receiving unit 12
The collimated light incident on is focused on the light receiving element 18 by a converging lens (not shown), for example. Then, the collected light is photoelectrically converted by the light receiving element 18, A / D converted as an output signal having a level corresponding to the amount of light received by the light receiving element 18, and then provided to the CPU 20.

If, for example, the detection object W1 is present in the optical path L1 of the parallel light, the parallel light incident on the light receiving window 17a is blocked thereby, and the amount of light received by the light receiving element 18 decreases. Therefore, as will be described later, the CPU 20 can detect the detection object existing in the optical path L1 by comparing the output signal level from the light receiving circuit 19 and the reference level as a threshold value. It should be noted that in the present embodiment, the detection objects W1 and W2 are arranged in the light projecting window 14a and the light receiving window 17a.
It is configured to move along the minor axis direction of a (vertical direction in FIG. 1) and cross the optical path L1. Therefore, the width of the light receiving window 17a in the long axis direction (the depth direction in the figure) of the optical path L1 becomes the detection width.

A mode changeover switch 21 is connected to the CPU 20 as shown in FIG. 1, and by operating the mode changeover switch 21, it is possible to change modes such as a "detection mode" and a "reception ratio detection mode" which will be described later. become. Further, in the present embodiment, a so-called jog switch (registered trademark) (hereinafter referred to as “jog switch 22”) is provided, and the switch input circuit 23 causes the CPU to operate in accordance with the operation.
It is designed to give signals to 20.

The contents set according to the operation are displayed on a 7-segment 4-digit liquid crystal display (hereinafter referred to as "LCD 25") driven by the display circuit 24. A predetermined operation in each mode can be performed by the jog switch 22. In addition,
The jog switch 22 is provided with an operation wheel which is rotationally operated by fingers, although the structural details thereof are not shown, and the LC is provided by rotating the operation wheel.
Each digit or character of 0 to 9 can be displayed in each digit of D25, and the number displayed on the LCD 25 can be confirmed by pressing the operation wheel at a desired position.

Now, FIG. 2A shows a slit plate 26 corresponding to the "light receiving range limiting means" of the present invention. Plural kinds of slit plates 26 are prepared (only one of them is shown in FIG. 7A), and each of them is a plate member having substantially the same shape as the surface of the light receiving case 17 having the light receiving window 17a. Therefore, the slit 27 is formed at a position corresponding to the light receiving window 17a of the light receiving unit 12. Regarding the slits 27 of each slit plate 26, the width in the major axis direction is substantially the same as the width in the major axis direction of the light receiving window 17a, and only the width in the minor axis direction has various widths narrower than the light receiving window 17a. Is formed (corresponding to the invention of claim 3).

Further, on each slit plate 26, for example, a pair of hooking elastic pieces 2 projecting so as to sandwich the side surface of the light receiving case 17 at both ends in the same direction as the minor axis direction of the slit 27.
8, 28 are provided. On the other hand, on the side of the light receiving case 17, a pair of hooking holes 30, 30 into which the hooking protrusions 29, 29 at the tips of the pair of hooking elastic pieces 28, 28 are fitted are formed on both side surfaces thereof. . With this structure, the plurality of slit plates 26 can be replaceably attached to the light-receiving case 17, and thus the parallel light from the light-projecting unit 11 can pass through in consideration of, for example, the size of the detection object. It is possible to change the light receiving range of the unit 12.

In addition to the above structure, the "light receiving range limiting means" has a structure in which a pair of plates 31, 31 are slidably arranged in parallel on the front surface of the light receiving case 17 as shown in FIG. 2B. May be Also with this configuration, the light receiving range can be changed by changing the distance between the pair of plates 31, 31. Further, instead of a pair of plates, one plate may be slidably arranged on the front surface of the light receiving case 17, and the plates may be slid to limit the light receiving range from one direction.

Now, regarding the operation and effect of this embodiment, CP
A description will be given based on the control content executed in U20. This explanation of the operation should clarify the software configuration of the present embodiment. For example, as shown in FIG. 1, when detecting a size of the detection object W1, it is considered that accurate detection can be performed without the purpose of mounting the above-mentioned slit plate 26. To be However, when detecting a minute object such as the detection object W2 in the region of the light receiving window 17a of the light receiving unit 12, the amount of light shielded by the detection object W2 is also minute, so the light receiving element 18
Also, the difference in the amount of received light becomes small, and the level difference in the output signal output from the light receiving circuit 19 becomes small. Therefore, stable detection cannot be performed, for example, because the light from other than the light projecting unit 11, that is, the influence of so-called ambient light is easily received. Therefore, the work described below is performed. In the present description, the energy density of the parallel light emitted from the light projecting unit 11 is considered to be substantially uniform, and the light shielding area of the detection object W2 is 10% of the opening area of the light receiving window 17a. I will give you an explanation.

<Detection of Light-Reception Ratio> First, a slit plate 26 having an appropriate opening area from the plurality of slit plates 26 in accordance with the size of the detection object W2 (in this description, the width in the minor axis direction is the light-receiving window 17a). Half width in the minor axis direction) is selected. Then, the mode selector switch 21 of the controller unit 13 is switched to the "light receiving ratio detection mode". The jog switch 22 is pressed once with the slit plate 26 not attached and the detection object W2 not present in the optical path L1. Then, the CPU 20 gives a control signal to the light projecting circuit 16 to cause the light projecting element 15 to emit light, and the output signal level from the light receiving circuit 19 is stored in a storage unit (not shown) as "maximum output signal level D1".

Next, the selected slit plate 26 is mounted on the light receiving case 17, and the jog switch 22 is pressed once again. Then, the CPU 20 also causes the light projecting circuit 1 to operate.
A control signal is given to 6 to cause the light projecting element 15 to emit light, and the output signal level from the light receiving circuit 19 is stored in the storage section as “detection output signal level D2”. Here, the CPU 20
Functions as the "detection means" of the present invention. That is, the light receiving ratio S (= D1 / D2) is calculated from the maximum output signal level D1 and the detected output signal level D2 and stored in the storage unit. In addition,
The maximum output signal level D1 may be preset. With this configuration, when the slit plate 26 is mounted, the detection output signal level D after mounting is set.
The work can be simplified simply by measuring 2.

<Detection of Detection Object> Next, the mode selector switch 21 is switched to the "detection mode" to start detection of the detection object W2. At this time, the CPU 20 functions as the "determination means" of the present invention. That is, the CPU 20 drives the light projecting unit 11 and the light receiving unit 12 at a predetermined timing to receive the output signal level from the light receiving circuit 19. Then, the CPU 20 multiplies the output signal level by the light receiving ratio and performs the determination operation based on the conversion level. More specifically, as shown in FIG. 3, the slit plate 2
6 is not attached, the detection object W2 in the optical path L1
The maximum output signal level D1 when there is no
If I), on the other hand, the output signal level when there is the detection object W2 is 90 (II in the figure). On the other hand, when the slit plate 26 is mounted, the optical path of the parallel light emitted from the light projecting section 11 and reaching the light receiving section 12 is narrowed by the slit 12 (hereinafter, the optical path when the slit is mounted is referred to as "optical path L2").

The detection output signal level D2 when the detection object W2 is not present in the optical path L2 is 50 (III in the figure), and the output signal level when the detection object W2 is present is 40.
(IV in the figure). That is, by limiting the light receiving range of the light receiving unit 12 by the slit plate 26, the change rate of the output signal level that changes depending on the presence or absence of the detection object W2 can be doubled as compared with the case where the slit plate 26 is not attached. it can. Then, the output signal from the light receiving circuit 19 is converted into the light receiving ratio S (2 =
100/50), the conversion level becomes 100 when there is no detected object W2,
When there is, it becomes 80. The CPU 20 can detect the detection object W2 by comparing the conversion level with a preset reference level. The reference level is intermediate between the conversion level when the detection object W2 is present in the optical path L2 with the slit plate 26 attached in advance in the "threshold setting mode" and the conversion level when the detection object W2 is not present. It may be set to a level.

As described above, by adjusting the light receiving range of the light receiving portion 12 by the slit plate 26, a minute detection object W2
Also, it is possible to increase the change rate of the output signal level in the light receiving unit 12. Further, the CPU 20 performs the detection operation based on the light receiving ratio S, that is, the conversion level according to the change rate of the light receiving amount level of the light receiving unit 12 by the slit plate 26. Therefore, it is possible to accurately detect the detection object W2 without requiring a difficult sensitivity adjustment work such as setting the gain of the light receiving amplifier to an optimum gain as in the conventional configuration in which the slit plate 26 is attached to adjust the sensitivity. it can.

In addition, the slits 27 of each slit plate 26
Is formed to be shorter than the light receiving window 17a only in the short axis direction, and therefore, by mounting them, only the width in the short axis direction of the light receiving window 17a, that is, the width in the same direction as the moving direction of the detection object is limited. To be done. Therefore, it is possible to stably and accurately detect the minute detection object W2 without limiting the detection width.

<Other Embodiments> The present invention is not limited to the above-described embodiments. For example, the embodiments described below are also included in the technical scope of the present invention.
Other than the following, various modifications can be made without departing from the scope of the invention. (1) In the above embodiment, the transmissive photoelectric sensor 10 is described as an example, but a reflective photoelectric sensor may be used.

(2) Further, it may be a photoelectric sensor for measuring the advancing position (for example, a displacement sensor) of the detection object advancing in the optical path or the width or size of the detection object existing in the optical path. That is, the same effect can be obtained by applying the present invention not only in the case where the detection object is minute, but also in the photoelectric sensor for measuring various detection objects whose mutual dimensional difference is small, for example. .

(3) In the above embodiment, the slit plate 26
In the above description, the configuration is described in which the light emitting unit 11 is mounted only. However, the configuration is not limited to this, and the light emitting unit 11 may be mounted only in the light projecting unit 11 or both the light projecting unit 11 and the light receiving unit 12.

(4) In the above embodiment, the slit plate 26
Although only the width in the minor axis direction of the light receiving window 17a is limited by the above, the width in the major axis direction or the width in both the minor axis direction and the major axis direction may be narrowed. However,
As described above, with the configuration according to the present embodiment, it is possible to stably and accurately detect a minute detection object, measure dimensions, and the like without limiting the detection width and the measurement width.

[Brief description of drawings]

FIG. 1 is a transmission photoelectric sensor 1 according to an embodiment of the present invention.
0 hardware configuration diagram

FIG. 2 is a perspective view showing a configuration corresponding to a light receiving case 17 and a light receiving range limiting unit.

FIG. 3 is a schematic diagram showing a relationship between a light receiving range and an output signal level.

[Explanation of symbols]

10: Transmission type photoelectric sensor 11 ... Projector 12 ... Light receiving part 13 ... Controller section 17a ... Light receiving window 20 ... CPU 26 ... Slit plate 31 ... Plate L1, L2 ... Optical path W1, W2 ... Detecting object

Continued front page    F term (reference) 2F065 AA01 AA07 AA12 AA20 AA21                       BB12 BB24 DD04 FF02 FF04                       HH03 HH05 HH15 JJ02 JJ09                       JJ25 LL04 LL28 QQ03 QQ05                       QQ08 QQ25 QQ26                 2G065 AA04 AB23 BB23 BC24 BC35                       BD01

Claims (3)

[Claims] 1. A light projecting means for emitting light into a detection region,
A light receiving unit that receives reflected light or transmitted light of the light emitted from the light projecting unit, and a determination unit that operates according to the amount of light received by the light receiving unit that changes depending on the presence or absence of a detection object in the detection region are provided. In the photoelectric sensor, a light receiving range limiting unit that is arranged in at least one of the light projecting unit and the light receiving unit and is capable of adjusting the light receiving range of the light receiving unit to a desired range, and within the detection region. The amount of light received before the light receiving range is limited by the light receiving range limiting means and the light receiving range after the light receiving range is limited by the light receiving range limiting means in the state where no detection object is present. And a detection unit that detects the light reception ratio based on the light reception amount, and the determination unit converts the light reception amount level of the light reception unit according to the light reception ratio set by the detection unit. Photoelectric sensor, wherein the operating based on Le. 2. A light projecting means for emitting parallel light, a light receiving means arranged facing the light projecting means for receiving the parallel light, and a light blocking amount of a detection object existing in an optical path of the parallel light. In a photoelectric sensor including a determining unit that operates according to the amount of light received by the light receiving unit that changes, at least one of the light projecting unit and the light receiving unit is disposed, and the light received by the light receiving unit is received. A light receiving range limiting means capable of adjusting the range to a desired range, and a light receiving amount before the light receiving range of the light receiving means is limited by the light receiving range limiting means in a state where no detection object exists in the optical path, A light receiving amount after the light receiving range is limited by the light receiving range limiting unit, and a detecting unit that detects a light receiving ratio based on a light receiving amount, and the determining unit receives the light receiving level of the light receiving unit. The above A photoelectric sensor which operates based on a conversion level converted according to a light receiving ratio set by a detection means. 3. The light receiving range limiting means adjusts the light receiving range by limiting the width of the light receiving range of the light receiving means in the same direction as the moving direction of the detection object. The photoelectric sensor according to claim 2.