JPH06241783A - Trigonometrical ranging photoelecrtric sensor - Google Patents

Abstract

PURPOSE:To provide a trigonometrical ranging photoelectric sensor capable of relatively precisely detecting objects changed with distances to measured surfaces and having a simple structure. CONSTITUTION:A photoelectric sensor 10 is provided with a light projector 11 radiating the light to objects and a photo-diode array 14 arranged with multiple photo-diodes having light receiving faces receiving the reflected light from the measured surfaces of the objects in the same semiconductor element. The layout pitch of the photo-diodes is set so that the reflected light is concurrently fed to the light receiving faces of both photo-diodes when the reflected light fed to the photo-diode array 14 is located at the middle portion between adjacent photo-diodes, and (2N-1) operating distances are obtained with N photo- diodes (wherein N is an optional integer).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric sensor for individually detecting an object whose distance to a surface to be measured changes.

[0002]

2. Description of the Related Art For example, as shown in FIG. 7, it is assumed that an object T having measured surfaces A, B, C and D having different heights is traveling on a conveyance path. Each measured surface A of this object T
When D is to be detected by the optical sensor S installed at the position P on the transport path, the following two methods have been conventionally adopted.

As one of them, as shown in FIG. 8, a plurality of reflection type optical sensors 1A to 1D for respectively detecting the respective measured surfaces A to D are arranged in parallel at a detection position P, and the respective reflection optical sensors 1A to 1D are arranged. This is a method of individually detecting each of the measured surfaces A to D by the optical optical sensors 1A to 1D. Each reflective optical sensor 1A-1D
Are each composed of a light projector 2 and a light receiver 3.

The other is a method for detecting each of the measured surfaces A to D by the displacement sensor 4 using the optical triangulation method as shown in FIG. The displacement sensor 4 includes a projector 4 ₁ such as a light emitting diode or a semiconductor laser, a PSD (Posi
optical position detection element 4 called “action sensitive detector”
₂ , a light projecting lens 4 ₃ and a light receiving lens 4 ₄ . The light position detection element 4 ₂ is an element that outputs currents I ₁ and I ₂ according to the light incident position on the light receiving surface.
The light emitted from the projector 4 _1, when each is reflected at different measurement surface A~D heights, is incident at different positions of the light receiving surface of the light position detection element 4 _2, each of the measurement surface A The ratio of the output currents I ₁ and I ₂ changes according to D. The displacement sensor 4 has such output currents I ₁ , I
Based on the ratio of ₂ , the distances to the measured surfaces A to D of the object are continuously detected.

[0005]

However, the conventional example having such a structure has the following problems. First, in the case of using a plurality of reflection type optical sensors, there is a problem that the device becomes large in size because it is necessary to provide the sensors according to the number of measured surfaces. In addition, when the sensors are installed close to each other, the adjacent sensors interfere with each other and are apt to malfunction.

On the other hand, the above-mentioned optical position detecting element (PSD)
In the case of the displacement sensor using, the ratio of the output currents I ₁ and I ₂ changes to about 100 to 1000 times depending on the incident position of the reflected light, so that the output currents I ₁ and I ₂ are amplified at the same ratio. However, there is a problem in that signal processing becomes complicated. Further, this type of displacement sensor is generally expensive.

The present invention has been made in view of the above circumstances, and it is possible to detect an object such that the distance to the surface to be measured changes with relatively high accuracy, and the structure is simple. It is intended to provide a photoelectric sensor.

[0008]

The present invention has the following constitution in order to achieve such an object. Claim 1
The triangulation type photoelectric sensor described in 1 is a semiconductor device in which a light projector for irradiating light toward an object and a photodiode having a plurality of light receiving surfaces for receiving reflected light from the surface to be measured of the object are the same semiconductor element. A photodiode array arranged side by side within the photodiode array, and when the reflected light incident on the photodiode array is located at an intermediate portion of the adjacent photodiodes, a part of the reflected light is received on the light receiving surfaces of the photodiodes. So that they are incident simultaneously, the array pitch of the photodiodes is set according to the spot diameter of the reflected light, and the object whose measurement surface is in the vicinity of the working distance related to each photodiode is set to the photodiode array. The detection is performed by each output of.

According to another aspect of the present invention, there is provided a triangulation type photoelectric sensor according to the first aspect.
An amplifier for amplifying the detection signal of each photodiode and a comparator for shaping the output signal of each amplifier into a pulse signal are provided, and the amplification factor of each amplifier or the reference voltage of each comparator is arbitrary. It is configured to be settable.

[0010]

According to the first aspect of the present invention, when light is emitted from the projector toward the object, the reflected light is incident on the photodiode array from the sensor to the surface to be measured of the object. It changes according to the distance. As a result, the output (ON / OFF state) of each photodiode constituting the photodiode array also changes according to the distance from the sensor to the surface to be measured of the object. At this time, when the reflected light is incident on the intermediate portion of the adjacent photodiodes, both photodiodes simultaneously output detection signals. Therefore, by identifying each output of the photodiode array, not only each measured surface at the same working distance as the photodiode is detected, but also at the working distance located approximately in the middle between the respective working distances. Each measured surface can also be detected.

According to the second aspect of the present invention, the amplification factor of the amplifier for amplifying the detection signal of each photodiode or the reference voltage of the comparator for shaping the output signal of each amplifier into a pulse signal is appropriately set. By setting, the pulse width of the pulse signal output from the comparator can be changed. Therefore, when the reflected light is incident on the intermediate portion of the adjacent photodiodes, the high resolution state in which each pulse signal obtained based on the detection signals of both photodiodes is output at the same time, and only one of the pulse signals is output. The low resolution state to be output can be arbitrarily set.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 is a view showing the schematic arrangement of a triangulation type photoelectric sensor according to the first embodiment of the present invention.

The photoelectric sensor 10 includes a light projector 11 such as a light emitting diode or a semiconductor laser, a light projecting lens 12 for focusing light emitted from the light projector 11, and light reflected from the measured surfaces A to D of an object. A light receiving lens 13, a photodiode array 14 that detects the reflected light, a waveform shaping circuit 15 that waveform-shapes each output of the photodiode array 14 and outputs the waveform individually, and the like are housed in a casing 16. There is.

[0014] The photodiode array 14, as shown in FIG. 2, the semiconductor device 17 such as a silicon substrate, each four photodiodes 19 having a rectangular light-receiving surface 18 (18 _{1-18 4)} (19 ₁ - 19 ₄ ) are arranged in parallel at a predetermined pitch P. Each photodiode 19 has a surface to be measured _A , L, L _B , L _C , L _{D in} the vicinity thereof.
It is arranged so as to receive the reflected light RL from B, C, and D. Further, in this embodiment, in order to increase the resolution of the photoelectric sensor, the reflected light RL imaged on the light receiving surface 18 by the light receiving lens 13 is adjacent to the photodiode 1
When incident on the intermediate portion of 9, both photodiodes 19
The arrangement pitch of the photodiodes 19 is set so that part of the reflected light RL is simultaneously incident on the light receiving surface 18 of the reflected light RL.
It is set according to the spot diameter.

[0015] As will become apparent from the explanation of operation will be described later, by arranging the photodiodes 19 as described above, the working distance L _A, L _B, L _C, the measured surface A in the vicinity of the L _D, The seven measured surfaces B, C, D and the measured surfaces AB, BC, CD near the respective intermediate positions are 4
The detection is performed based on each output of the one photodiode 19. Note that reference numeral 20 in FIG. 2 is an electrode for extracting a signal of each photodiode 19.

The number of photodiodes 19 constituting the photodiode array 14 is arbitrarily set according to the number of working distances that the photoelectric sensor 10 is going to detect, and the photoelectric sensor according to this embodiment has a high resolution. According to N
(N + 1) /
Two photodiodes may be arranged side by side. An arbitrary working distance can be set by changing the pitch P of each photodiode 19. Further, each photodiode 19 has a predetermined detection width ΔS, and detects a surface to be measured within the working distance L ± ΔS / 2. The detection width ΔS is appropriately set according to the light receiving width W of the light receiving surface 18.

The waveform shaping circuit 15, as shown in FIG.
Amplifiers 20 _{1 to} 20 ₄ for amplifying the outputs of the photodiodes 19 _{1 to} 19 ₄ and comparators 21 ₁ to shaping the output signals of the amplifiers 20 _{1 to} 20 ₄ into rectangular pulse signals.
It is composed of 21 ₄ . In addition, V _REF in the figure is a reference voltage of the comparators 21 _{1 to} 21 ₄ . In this embodiment,
Although the waveform shaping circuit 15 is composed of individual components, they may be integrally formed with the semiconductor element 17 shown in FIG. 2 so that the photodiode array 14 and the waveform shaping circuit 15 are integrated into one chip.

Next, the operation of the above-described triangulation type photoelectric sensor will be described with reference to FIG. FIG. 4A shows the incident position of the reflected light RL on the photodiode array 14, FIGS. 4B1 to 4B show the output signals of the amplifiers 20 _{1 to} 20 ₄ , and FIG. (C4) is the comparator 21 ₁
21 ₄ shows each output signal.

Now, assuming that the object having the surface A to be measured comes directly under the photoelectric sensor 10, the reflected light (scattered light) RL _A from the surface A to be measured is focused by the light receiving lens 13,
It is incident only on the light receiving surface 18 ₁ of the photodiode array 14. As a result, the output terminal OUT ₁ of the waveform shaping circuit 15
From this, the detection signal S _A is output.

When the surface to be measured B comes directly under the photoelectric sensor 10, the reflected light RL _B is reflected by the photodiode array 14.
It is incident only on the light receiving surface 18 _{2 of the above} , and the detection signal S _B is output only from the output terminal OUT ₂ .

Similarly, when the measured surface C is detected, the detection signal Sc is output only from the output terminal OUT ₃ , and when the measured surface D is detected, the detection signal S is output from only the output terminal OUT _{4. D} is output.

On the other hand, if an object having the surface to be measured AB belonging to the working distance L _AB which is between the working distances L _A and L _B comes directly under the photoelectric sensor 10, the reflected light RL from the surface to be measured AB is measured. _AB is incident on the light receiving surfaces 18 ₁ and 18 _{2 of the} photodiode array 14 at the same time. As a result, the detection signals S _A and S _B are simultaneously output from the output terminals OUT ₁ and OUT _{2 of} the waveform shaping circuit 15.

[0023] Hereinafter, similarly, when the surface to be measured BC is detected belonging to the working distance L _BC, the output terminal OUT ₂ and OU
T ₃ from the detection signal S _B, S _C is output at the same time, the surface to be measured CD is detected belonging to the working distance L _CD, the detection signal from the output terminal OUT ₃ and OUT ₄ S _C, S _D is output at the same time It

<Second Embodiment> In the first embodiment, the resolution of the photoelectric sensor is fixedly set according to the arrangement pitch of the light receiving surfaces which is determined in relation to the spot diameter of the reflected light incident on the photodiode array. In the second embodiment, the resolution can be set arbitrarily.

The photoelectric sensor according to this embodiment is similar to the first embodiment in that the projector 11, the projector lens 12 and the light receiving lens 1 are the same.
3 and the photodiode array 14, and a waveform shaping circuit 25 as shown in FIG. The waveform shaping circuit 25 is provided in each of the amplifiers 20 _{1 to} 20 _4.
The amplification factor of 1 can be arbitrarily set by the variable resistor VR.

The operation of this embodiment will be described below with reference to FIG. For example, the amplification factor of the amplifier 20 ₁ is set to the other amplifier 2
When the amplification factor is set to be smaller than 0 _{2 to} 20 ₄ , the pulse width of the output signal OUT ₁ of the comparator 21 ₁ becomes smaller accordingly (see (b1) and (c1) in FIG. 6). Therefore,
By setting the amplification factor of the amplifier 20 ₁ so low that the detection signal S _A is not output at the same time as the detection signal S _B , the working distance L _{AB at} the intermediate position between the working distances L _A and L _B is set.
It is possible to deactivate the photoelectric sensor with.
That is, here, there are 6 working distances (6 resolutions).

Similarly, other working distances L _BC and L _CD can be arbitrarily set by changing the amplification factors of the amplifiers 20 _{2 to} 20 ₄ . In addition, each amplifier 20 ₁ to 2
If the amplification factor is set so that the level of the output signal of 0 ₄ is always equal to or lower than the reference voltage V _REF , the working distances L _A , L _B ,
It is possible to arbitrarily set L _C and L _D. In short, in this embodiment, the working distance (resolution) is at least 1
One, up to seven, can be arbitrarily set.

[0028] In the second embodiment, an amplifier 20 21 _to
The resolution can be arbitrarily set by changing the amplification factor of 0 _4. However, instead of keeping the amplification factor of each amplifier 20 _{1 to} 20 ₄ constant, the reference voltage V of each comparator 21 _{1 to} 21 ₄ is changed. _The resolution may be arbitrarily set by changing _REF .

[0029]

As is apparent from the above description, according to the invention described in claim 1, the reflected light of the light emitted from the projector toward the surface to be measured of the object is detected by the photodiode array. By doing so, it detects an object at a predetermined working distance, so compared to the conventional example in which measured surfaces with different heights are individually measured using multiple reflective optical sensors. As a result, the device becomes smaller. Further, since only one light projector is used, there is no risk of malfunction due to light interference as in the conventional example.

The output current of the photodiode array has a narrower dynamic range than that of the conventional optical position detecting element (PSD), so that signal processing can be performed easily and a photoelectric sensor of this type can be used. It can also be realized at low cost.

Moreover, when the reflected light from the surface to be measured is incident on the intermediate portion of the adjacent photodiodes, the surface to be measured is detected based on the signals output from both photodiodes. Therefore, 2N-1 working distances can be obtained by using N photodiodes, and a high-resolution photoelectric sensor can be easily realized.

According to the second aspect of the present invention, the width of the pulse signal output from the comparator corresponding to each photodiode is arbitrarily set, so that N photodiodes are used and the width is at least 1. One, an arbitrary number of working distances can be obtained between 2N-1 at maximum, that is, the resolution can be set arbitrarily.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a triangulation type photoelectric sensor according to an embodiment.

FIG. 2 is a plan view of a photodiode array.

FIG. 3 is a block diagram showing a configuration of a photoelectric sensor according to the first embodiment.

FIG. 4 is an operation explanatory diagram of the first embodiment.

FIG. 5 is a block diagram showing a configuration of a photoelectric sensor according to a second example.

FIG. 6 is an operation explanatory diagram of the second embodiment.

FIG. 7 is an explanatory diagram of a conventional measurement example.

FIG. 8 is a diagram showing a measurement example using a reflective optical sensor.

FIG. 9 is a diagram showing an example of measurement by a displacement sensor using an optical position detecting element.

[Explanation of symbols]

10 ... photoelectric sensor 11 ... projector 14 ... photodiode array 15 ... waveform shaping circuit 17 ... semiconductor device 18 _{1-18 4} ... light-receiving surface 19 _{1-19 4} ... photodiode 20 ₁ to 20 ₄ ... amplifier 21 ₁ to 21 ₄ ... Comparator

Claims (2)

[Claims] 1. A photo in which a light projector for irradiating an object with light and a photodiode having a plurality of light receiving surfaces for receiving reflected light from the surface of the object to be measured are arranged in parallel in the same semiconductor element. A diode array, and when the reflected light incident on the photodiode array is located at an intermediate portion of the adjacent photodiodes, a part of the reflected light is simultaneously incident on the light receiving surfaces of the photodiodes. , The array pitch of each photodiode is set according to the spot diameter of the reflected light, and the object whose measured surface is near the working distance associated with each photodiode is detected by each output of the photodiode array. The triangular distance measuring photoelectric sensor characterized in that 2. The triangulation type photoelectric sensor according to claim 1, further comprising an amplifier that amplifies a detection signal of each photodiode, and a comparator that shapes an output signal of each amplifier into a pulse signal, Further, a triangulation type photoelectric sensor characterized in that the amplification factor of each amplifier or the reference voltage of each comparator can be arbitrarily set.