JPH06249649A - Triangulation type photoelectric sensor - Google Patents

Abstract

PURPOSE:To accurately detect such an object that the distance to a surface to be measured varies by using an array on which a plurality of photodiodes for receiving reflected light from the surface to be measured are arranged in parallel at non-regular intervals in the same semiconductor element. CONSTITUTION:The title sensor 10 is constituted of a projector 11, projection lens 12, light receiving lens 13 which converges reflected light rays from surfaces A-D to be measured, photodiode array 14 which detects the reflected light rays, and waveform shaping circuit 15. On the array 14, four photodiodes respectively having rectangular light receiving surfaces 181-184 are arranged in parallel at non-regular intervals in a semiconductor element. The photodiodes are arranged at the positions PA, PB, PC, and PD to which reflected light rays RL respectively reflected by the surfaces A-D near working distances LA, LB, LC, and LD set at regular intervals at every distance (d) are made incident. In addition, the photodiodes are constituted so that the relation between their detecting signals they output whenever they detect the surfaces A-D and the working distances can become linear.

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. 12, 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
In order to detect D through D by the optical sensor S installed at the position P on the transport path, conventionally, the following two methods are adopted.

As one of them, as shown in FIG. 13, a plurality of reflection type optical sensors 1A to 1D for detecting each of the measured surfaces A to D are arranged in parallel at a detection position P, and each reflection type optical sensor 1A to 1D is 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-1
D is composed of a light projector 2 and a light receiver 3, respectively.

The other is, as shown in FIG. 14, each of the measured surfaces A to D is measured by the displacement sensor 4 using the optical triangulation method.
Is a method of detecting. The displacement sensor 4 includes a projector 4 ₁ such as a light emitting diode or a semiconductor laser, a PSD (Po
sition Sensitive Detector), which is composed of a light position detecting element 4 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 height, the light position detecting element 4
_Since the light is incident on different positions on the _two light receiving surfaces, the ratio of the output currents I ₁ and I ₂ changes depending on the measured surfaces A to D. This displacement sensor 4 has such an output current I ₁ ,
The distances to the measured surfaces A to D of the object are continuously detected based on the ratio of I ₂ .

[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.

Further, as shown in FIG. 15, according to the conventional displacement sensor 4 using the triangulation method, for example, the working distances L _A , L _B , Lc and L _D are set at equal intervals with a distance d. If it is, the distance between the position _{P a, P B, Pc,} P D of the reflected light RL from the surface to be measured A~D in each working distance is incident on the light position detecting element 4 ₂ is not at equal intervals,
As in the case of d ₁ , d ₂ and d ₃ (d ₁ <d ₂ <d ₃ ), the closer the measured surface is to the displacement sensor 4, the larger the interval. Since the relationship between the working distance L _A ~L _D the incident position P _A to P _D of the reflected light is not changed linearly (linear), the output current I ₁ of the light position detection element 4 _2, I ₂ And the working distances L _{A to} L _D are also non-linear. Therefore, if it is attempted to make the relationship between the output current and the working distance linear, a linearity correction circuit is required, and the circuit configuration becomes complicated accordingly.

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.

Another object of the present invention is to provide a photoelectric sensor in which the relationship between the output of the photoelectric sensor and the working distance can be set arbitrarily and relatively easily.

[0010]

The present invention has the following constitution in order to achieve such an object. That is, the triangulation type photoelectric sensor according to the present invention includes a light projector that irradiates an object with light, and a photodiode having a plurality of light receiving surfaces that receive reflected light from the surface of the object to be measured. A photodiode array arranged in parallel at non-equidistant positions in the same semiconductor element at positions where reflected light from each surface to be measured located in the vicinity of a plurality of predetermined working distances is incident, The object having each of the surfaces to be measured is detected by each output of.

[0011]

The operation of the present invention is as follows. When light is emitted from the light projector toward the object, the position where the reflected light is incident on the photodiode array changes according to the distance from the sensor to the surface to be measured of the object. 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. Therefore, by identifying the output of the photodiode array, it is possible to detect which photodiode the working distance of the measured surface of the object is.

Further, since the respective photodiodes are arranged in parallel in the same semiconductor element at positions where reflected light from the respective measured surfaces located in the vicinity of a plurality of predetermined working distances are incident, with an unequal pitch. , If the photodiodes are arranged side by side at non-equidistant pitches corresponding to the working distances set at equal intervals, the relationship between each output of the photodiode array and the working distance will be linear, and set at non-equidistant intervals. If the photodiodes are arranged in parallel at non-equidistant pitches corresponding to the determined working distance, the relationship between each output of the photodiode array and the working distance becomes non-linear.

[0013]

Embodiments 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 triangular distance measuring photoelectric sensor according to an embodiment of the present invention. The photoelectric sensor according to the present embodiment is configured such that the relationship between its output and the set working distance is linear.

The photoelectric sensor 10 includes a light projector 11 such as a light emitting diode or a semiconductor laser, a light projecting lens 12 that focuses 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.

The photodiode array 14 is shown in FIG.
As shown in FIG.
Light receiving surface 18₁~ 18_FourFour photodioes with
Do 19₁~ 19_FourAre arranged side by side with unequal pitch. Each
Photodiode 19₁~ 19 _FourIs an equal interval for each distance d
Working distance L set to_A, L_B, L_C, L_DNear
Anti-reflection reflected on each measured surface A, B, C, D
Position P where incident light (scattered light) RL is incident on the element surface_A，
P_B, P_C, P_DAre placed in the respective
It is configured to detect the surfaces A to D in a discrete manner. Na
The reference numeral 20 in the figure indicates each photodiode 19₁~ 1
9_FourThis is an electrode for extracting the signal.

The number of photodiodes constituting the photodiode array 14 is arbitrarily set according to the number of working distances that the photoelectric sensor 10 is to detect. For example, to obtain 10 working distances. If so, ten photodiodes may be arranged in parallel. In addition, the intervals between the photodiodes 19 _{1 to} 19 ₄ are set appropriately according to the intervals of the working distances.

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 a comparator 21 ₁ for shaping the output signals of the amplifiers 20 _{1 to} 20 ₄ into rectangular pulse signals.
It consists of ~ 21 ₄ . In this embodiment, the waveform shaping circuit 15 is composed of individual components, but these components are not shown in FIG.
Alternatively, the photodiode array 14 and the waveform shaping circuit 15 may be integrally formed on the semiconductor element 17 shown in FIG.

Next, the operation of the above-described triangulation type photoelectric sensor will be described with reference to FIGS. Now, it is assumed that the object T having the measured surfaces A to D having different heights is detected by the photoelectric sensor 10 according to the embodiment. As shown in FIG. 4A, when the measured surface A of the object T comes directly under the photoelectric sensor 10, as shown in FIG. 4B, the reflected light from the measured surface A (scattered light). ) RL is focused by the light receiving lens 13 and is incident on the light receiving surface 18 ₁ of the photodiode array 14.
As a result, from the output terminal OUT ₁ of the waveform shaping circuit 15,
The detection signal S _A as shown in FIG. 3 is output.

Subsequently, as shown in FIG. 5, when the surface C to be measured comes directly under the photoelectric sensor 10, the reflected light RL enters the light receiving surface 18 ₃ of the photodiode array 14 and is detected from the output terminal OUT _3. The signal S _C is output. Similarly, as shown in FIG. 6, when the surface D to be measured is detected, the detection signal S _D is output from the output terminal OUT ₄ . Also,
As shown in FIG. 7, when the surface B to be measured is detected, the detection signal S _B is output from the output terminal OUT ₂ .

As described above, according to this embodiment, the measured surfaces A to A belonging to the working distances L _{A to} L _D set at equal intervals.
Since the detection signals S _{A to} S _D are output every time D is detected, a photoelectric sensor having a linear relationship between the detection signal and the working distance can be obtained.

<Second Embodiment> The photoelectric sensor 1 according to the first embodiment.
0 has a unique detection width ΔS for each set working distance L _{A to} L _D. The photoelectric sensor 10 operates when the surface to be measured is within the range of the working distance L ± ΔS / 2. This detection width ΔS is determined by the photodiode array 14
Is related to the width W (see FIG. 2) of the light receiving surfaces 18 ₁ to 18 ₄ . In the first embodiment, the detection widths ΔS _A , ΔS _B , ΔS _C , and ΔS _D at the respective working distances L _{A to} L _D are as follows because the width W of each light receiving surface 18 ₁ to 18 ₄ is set to a constant value. As shown in FIG. 1, the width becomes narrower as it gets closer to the photoelectric sensor 10.

On the other hand, the photoelectric sensor according to the second embodiment is constructed so as to have a constant detection width for each working distance. FIG. 8 shows the structure of the photodiode array, and FIG. 9 shows the schematic structure of the photoelectric sensor according to the second embodiment. In FIGS. 8 and 9, the portions denoted by the same reference numerals as those in FIGS. 1 and 2 have the same configuration as that of the first embodiment, and therefore the description thereof is omitted here.

The photodiode array 34 of this embodiment
As in the first embodiment, equally spaced set working distance L _A ~L _D reflected light reflected by the respective measurement surface A~D in the vicinity of the (scattered light) RL is the element surface photodiode 39 _{1-39 4} receiving surface 38 _{1-38 4} is formed at a position P _a to P _D which enters are arranged, each of the surface to be measured A~D by the photodiodes 39 ₁ to 39 ₄ Is discretely detected. Further, in this embodiment, the light-receiving surface 38 _{1-38 4} of each photodiode 39 _{1-39 4,} as the detection width ΔS of each working distance L _A ~L _D is substantially constant, each of the width W _{1 to} W ₄ are formed wider in that order (W ₁ <W ₂ <W ₃ <
W ₄ ).

The detection width ΔS can be arbitrarily set by appropriately changing the widths W _{1 to} W ₄ of the light receiving surfaces 38 _{1 to} 38 ₄ . In the present embodiment, the photodiode array 34 is configured as follows in order to easily change the setting of the detection width ΔS. Reference is made to the element cross-sectional view of FIG. The semiconductor element 35 such as a silicon substrate with an impurity diffusion layer 36 _{1-36 4} constituting the photodiode 39 _{1-39 4,} the light receiving surface 38 _1-38 widths W ₁ ~ ₄
It is formed wider than W ₄ , and each impurity diffusion layer 36 ₁
To 36 ₄ of the part of the surface is covered with a light shielding film 37 such as aluminum, light-receiving surface 38 _1-3 having a predetermined width W ₁ to _W-4
Forming 8 ₄ . By doing so, the detection width ΔS can be easily changed by changing the photomask of the light shielding film 37. Further, by changing the photo mask of the light-shielding film 37, can offset the center position of the light receiving surface 38 _{1-38 4} to some extent, the working distance L _A ~L _D
Can be easily accommodated.

<Third Embodiment> In the first and second embodiments, the photoelectric sensor in which the relationship between the detection signal and the working distance is linear is taken as an example, but in this embodiment, the detection signal and the working distance Is configured so that the relationship of is non-linear as intended.

Referring to FIG. The photoelectric sensor 40 according to the present embodiment has each of the measured surfaces A belonging to the working distances L _{A to} L _D set so that the respective intervals d ₁ , d ₂ , and d ₃ are different.
The photodiode arrays 44 in which the light receiving surfaces 48 _{1 to} 48 ₄ are arranged in parallel at non-uniform pitches are provided at the positions P _{A to} P _D where the reflected lights RL respectively reflected by the light beams _D to _D enter the element surface. In the present embodiment, the widths of the light receiving surfaces 48 _{1 to} 48 ₄ are made constant, but the widths may be gradually increased in the same manner as in the second embodiment to obtain a constant detection width.

Working distance L and photodiode array 44
FIG. 11 shows the relationship with the incident position P of the reflected light on. As understood from this figure, by appropriately setting the positions of the respective light receiving surfaces 48 _{1 to} 48 ₄ , the detection signal of the photoelectric sensor 40 and the working distance L can be set to a desired non-linear relationship. .

[0028]

As is apparent from the above description, according to the present invention, 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, and the predetermined value is determined. Since it is designed to detect objects at different working distances, the size of the device is smaller than in the conventional example in which multiple reflective optical sensors were used to individually measure the measured surfaces with different heights. Turn into. Further, since only one light projector is used, there is no risk of malfunction due to light interference as in the conventional example.

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

Further, since the photodiodes are arranged in parallel at a position where the reflected light from each surface to be measured, which is located in the vicinity of a plurality of predetermined working distances, is incident at an unequal pitch, the photodiodes are set at equal intervals. By arranging the photodiodes in parallel at non-equidistant pitches corresponding to the working distance, each output of the photodiode array and the working distance can be made to have a linear relationship, and the working distances set at non-equidistant intervals can be set. Correspondingly, by arranging the photodiodes in parallel at non-equidistant pitches, the outputs of the photodiode array and the working distance can be made to have a desired non-linear relationship.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a triangular distance measuring photoelectric sensor according to a first 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.

FIG. 5 is an operation explanatory diagram.

FIG. 6 is an operation explanatory diagram.

FIG. 7 is an operation explanatory diagram.

FIG. 8 is a configuration diagram of a photodiode array according to a second embodiment.

FIG. 9 is a diagram showing a schematic configuration of a triangular distance measuring photoelectric sensor according to a second embodiment.

FIG. 10 is a diagram showing a schematic configuration of a triangular distance measuring photoelectric sensor according to a third embodiment.

FIG. 11 is a diagram showing a relationship between a working distance and an incident position of reflected light.

FIG. 12 is an explanatory diagram of a conventional measurement example.

FIG. 13 is a diagram showing a measurement example using a reflective optical sensor.

FIG. 14 is a diagram showing a measurement example by a displacement sensor using an optical position detecting element.

FIG. 15 is a diagram for explaining a problem of a conventional displacement sensor.

[Explanation of symbols]

10, 30, 40 ... Photoelectric sensor 11 ... Projector 14, 34, 44 ... Photodiode array 15 ... Waveform shaping circuit 17 ... Semiconductor element 18 ₁ to 18 ₄ , 38 _{1 to} 38 ₄ , 48 _{1 to} 48 ₄ ... Light receiving surface 19 _{1-19 4} 39 _{1-39 4} ... photodiode 20 ₁ to 20 ₄ ... amplifier 21 ₁ to 21 ₄ ... comparator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 31/12 Z 7210-4M

Claims (1)

[Claims] 1. 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 provided in the same semiconductor element in advance. A plurality of photodiode arrays arranged in parallel at non-equidistant positions at which reflected light from each surface to be measured in the vicinity of a plurality of defined working distances are incident, and the respective surfaces to be measured by each output of the photodiode array. A triangulation type photoelectric sensor characterized in that it detects an object having.